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, Available online ,
doi: 10.11884/HPLPB202436.230444
Abstract:
During the commissioning of the primary helium circulator of the high-temperature gas-cooled reactor (HTGR), it could not complete the performance test of the full speed range, because the resistance of the primary loop was lower than the design condition. Based on the theoretical characteristics of the primary helium circulator and similar principles, a method for calculating the commission parameters of the primary helium circulator under different resistance conditions is developed. Combined with the monomeric test operating points of the primary helium circulator, accurately calculated the operating point parameters of the cold and hot performance tests of the primary helium circulator, and guided the completion of the full speed and full power performance tests of the primary helium circulator in HTGR. By comparing and analyzing the commission and factory test results of the primary helium circulator, the feasibility of this calculation method is verified, and provide correction factors for the conversion of working conditions between air medium and helium medium. Through comparing and analyzing the commission and operation data of the primary helium circulator, it can be seen that the commission conditions provided in this article have sufficient enveloping ability, which can cover all operating conditions of the primary helium circulator during the operation of HTGR. This proves that the variable resistance condition commission method of the primary helium circulator meets the performance verification requirements of HTGR, and it can be used to guide the primary helium circulator commission of subsequent HTGR.
During the commissioning of the primary helium circulator of the high-temperature gas-cooled reactor (HTGR), it could not complete the performance test of the full speed range, because the resistance of the primary loop was lower than the design condition. Based on the theoretical characteristics of the primary helium circulator and similar principles, a method for calculating the commission parameters of the primary helium circulator under different resistance conditions is developed. Combined with the monomeric test operating points of the primary helium circulator, accurately calculated the operating point parameters of the cold and hot performance tests of the primary helium circulator, and guided the completion of the full speed and full power performance tests of the primary helium circulator in HTGR. By comparing and analyzing the commission and factory test results of the primary helium circulator, the feasibility of this calculation method is verified, and provide correction factors for the conversion of working conditions between air medium and helium medium. Through comparing and analyzing the commission and operation data of the primary helium circulator, it can be seen that the commission conditions provided in this article have sufficient enveloping ability, which can cover all operating conditions of the primary helium circulator during the operation of HTGR. This proves that the variable resistance condition commission method of the primary helium circulator meets the performance verification requirements of HTGR, and it can be used to guide the primary helium circulator commission of subsequent HTGR.
, Available online ,
doi: 10.11884/HPLPB202436.230374
Abstract:
LINAC control network is the reference for optical axis transmission. According to the layout of key equipment in LINAC tunnel, the control network is laid out on the ground and wall of the tunnel. Tracker is the main instrument for measuring LINAC control network, and the angle measurement error is a key factor affecting the accuracy of the tracker. Based on the layout of wall and ground network points and the measurement plan, laser tracker’s angles were decomposed horizontal and vertical angles in all measurement states. Then, through the linkage testing of high-precision CMM and laser trackers, all the decomposed angles were calculated, and the calculated values are used to correct the tracker’s measurement angles. Based on the test results, regardless of the measurement state, measured angle of the tracker is larger than the calculated value. The ground network points’ vertical angle deviation and horizontal angle deviation almost equal to the nominal accuracy of the tracker. When the horizontal angle of wall points exceeds 15 degree, deviation increase significantly, and the deviation should be corrected while measuring the wall network points.
LINAC control network is the reference for optical axis transmission. According to the layout of key equipment in LINAC tunnel, the control network is laid out on the ground and wall of the tunnel. Tracker is the main instrument for measuring LINAC control network, and the angle measurement error is a key factor affecting the accuracy of the tracker. Based on the layout of wall and ground network points and the measurement plan, laser tracker’s angles were decomposed horizontal and vertical angles in all measurement states. Then, through the linkage testing of high-precision CMM and laser trackers, all the decomposed angles were calculated, and the calculated values are used to correct the tracker’s measurement angles. Based on the test results, regardless of the measurement state, measured angle of the tracker is larger than the calculated value. The ground network points’ vertical angle deviation and horizontal angle deviation almost equal to the nominal accuracy of the tracker. When the horizontal angle of wall points exceeds 15 degree, deviation increase significantly, and the deviation should be corrected while measuring the wall network points.
, Available online ,
doi: 10.11884/HPLPB202436.230342
Abstract:
Aiming at the output characteristics of diesel generator set with pulse load, an index is proposed to evaluate the consistency of output voltage (current) waveform to judge the simulation degree of the model. Also, a dynamic limiting method for synchronous generator excitation voltage output based on BP neural network algorithm is proposed, which is applied to the model optimization of diesel generator set. Experimental results show that 18 groups of real-time waveform proximity of waveforms are less than 90% among the 27sets of examples, but the optimized simulation model become better because all the test groups are higher than 90%, indicating that the optimized simulation model is more effective, and can be applied to the further research on diesel generator set with pulse load.
Aiming at the output characteristics of diesel generator set with pulse load, an index is proposed to evaluate the consistency of output voltage (current) waveform to judge the simulation degree of the model. Also, a dynamic limiting method for synchronous generator excitation voltage output based on BP neural network algorithm is proposed, which is applied to the model optimization of diesel generator set. Experimental results show that 18 groups of real-time waveform proximity of waveforms are less than 90% among the 27sets of examples, but the optimized simulation model become better because all the test groups are higher than 90%, indicating that the optimized simulation model is more effective, and can be applied to the further research on diesel generator set with pulse load.
, Available online ,
doi: 10.11884/HPLPB202436.240076
Abstract:
In the field of computational electromagnetics, the Discontinuous Galerkin Time Domain (DGTD) method typically relies on irregular grid partitioning in model space and high-order polynomial interpolation calculations on elements. When comparing two-dimensional spatial quadrilateral mesh partitioning to triangular mesh partitioning at the same interpolation order, quadrilateral meshing offers fewer degrees of freedom and higher computational efficiency. However, traditional basis function spaces, relying on isoparametric transformations and polynomial tensor product interpolation, only possess low-order completeness on quadrilateral elements. Consequently, their stability and accuracy are significantly influenced by grid distortion. Addressing this challenge, this thesis proposes a high-order B-spline interpolation DGTD method based on irregular quadrilateral meshes for solving Maxwell's equations. The advantage of B-spline interpolation lies in its high-order completeness on irregular elements, effectively eliminating internal degrees of freedom within the elements. Furthermore, the coefficient matrices of the discrete system for Maxwell's equations also possess exact analytical forms.. Utilizing this method to analyze the eigenmodes of cavities and the electromagnetic scattering of wedge structures, the results indicate that increasing the maximum allowable time step by 2.5 times, and reducing the required unknowns by 25% compared to COMSOL software, the proposed algorithm exhibits notable advantages in terms of higher stability and precision.
In the field of computational electromagnetics, the Discontinuous Galerkin Time Domain (DGTD) method typically relies on irregular grid partitioning in model space and high-order polynomial interpolation calculations on elements. When comparing two-dimensional spatial quadrilateral mesh partitioning to triangular mesh partitioning at the same interpolation order, quadrilateral meshing offers fewer degrees of freedom and higher computational efficiency. However, traditional basis function spaces, relying on isoparametric transformations and polynomial tensor product interpolation, only possess low-order completeness on quadrilateral elements. Consequently, their stability and accuracy are significantly influenced by grid distortion. Addressing this challenge, this thesis proposes a high-order B-spline interpolation DGTD method based on irregular quadrilateral meshes for solving Maxwell's equations. The advantage of B-spline interpolation lies in its high-order completeness on irregular elements, effectively eliminating internal degrees of freedom within the elements. Furthermore, the coefficient matrices of the discrete system for Maxwell's equations also possess exact analytical forms.. Utilizing this method to analyze the eigenmodes of cavities and the electromagnetic scattering of wedge structures, the results indicate that increasing the maximum allowable time step by 2.5 times, and reducing the required unknowns by 25% compared to COMSOL software, the proposed algorithm exhibits notable advantages in terms of higher stability and precision.
, Available online ,
doi: 10.11884/HPLPB202436.230371
Abstract:
In order to reduce the jitter of the direct current self-breakdown voltage, not affect the self-breakdown voltage as much as possible, an auxiliary discharge electrode structure with an auxiliary discharge needle implanted in the cathode center is designed based on the discharge gap of the annular electrode. The influence of the diameter, length and top chamfer of the auxiliary discharge needle on the field distortion is studied by electric field simulation. The direct current self-breakdown characteristics of the unintroduced auxiliary discharge needle and the introduce auxiliary discharge needle in dry air and SF6 gas are studied by experiments. The results show that the smaller the diameter and the longer the length of the auxiliary discharge needle, the weaker the shielding effect of the electrode ring on the electric field, the stronger the field distortion intensity;the influence of the implatation of auxiliary discharge needle on the direct current self-breakdown of SF6 gas discharge gap is small,and with the increase of the field distortion coefficient, the percentage drop of self-breakdown voltage of dry air at the same air pressure is 2～3 times that of SF6 gas; the auxiliary discharge needle has a beneficial effect on the breakdown stability of dry air and SF6 gas discharge gap under the condition of direct current , the dispersion reduction percentage is about 25% higher than that without auxiliary discharge needle.
In order to reduce the jitter of the direct current self-breakdown voltage, not affect the self-breakdown voltage as much as possible, an auxiliary discharge electrode structure with an auxiliary discharge needle implanted in the cathode center is designed based on the discharge gap of the annular electrode. The influence of the diameter, length and top chamfer of the auxiliary discharge needle on the field distortion is studied by electric field simulation. The direct current self-breakdown characteristics of the unintroduced auxiliary discharge needle and the introduce auxiliary discharge needle in dry air and SF6 gas are studied by experiments. The results show that the smaller the diameter and the longer the length of the auxiliary discharge needle, the weaker the shielding effect of the electrode ring on the electric field, the stronger the field distortion intensity;the influence of the implatation of auxiliary discharge needle on the direct current self-breakdown of SF6 gas discharge gap is small,and with the increase of the field distortion coefficient, the percentage drop of self-breakdown voltage of dry air at the same air pressure is 2～3 times that of SF6 gas; the auxiliary discharge needle has a beneficial effect on the breakdown stability of dry air and SF6 gas discharge gap under the condition of direct current , the dispersion reduction percentage is about 25% higher than that without auxiliary discharge needle.
, Available online ,
doi: 10.11884/HPLPB202436.240042
Abstract:
High-altitude electromagnetic pulse (HEMP), as a wide-area electromagnetic attack method, can cause severe impacts on the power equipment and even collapse of power infrastructure, posing significant challenges to the electromagnetic safety of novel power systems. This article focused on latest research progress on the power system effects in HEMP late-time environment. Firstly, the mechanism of geomagnetic disturbance generation and the calculation method of induced geomagnetic field are analyzed. The calculation method of geomagnetically induced current (GIC) is provided. Then, the effects and mechanisms of typical primary power equipment, such as power transformers, current transformers, circuit breakers, etc. under extreme GIC conditions are summarized. Next, the extreme GIC injection devices and simulated experiment methods are discussed. And the experimental and simulation results acquired by Defense Threat Reduction Agency (DTRA) and Electric Power Research Institute (EPRI) are also discussed, as well as the power system effects simulation and assessment. Finally, we summarized the main conclusions reached by the present work, and analyzed the future research from the perspective of effects mechanism, primary power equipment characteristics, simulated experimental methods, and system-level effects assessment.
High-altitude electromagnetic pulse (HEMP), as a wide-area electromagnetic attack method, can cause severe impacts on the power equipment and even collapse of power infrastructure, posing significant challenges to the electromagnetic safety of novel power systems. This article focused on latest research progress on the power system effects in HEMP late-time environment. Firstly, the mechanism of geomagnetic disturbance generation and the calculation method of induced geomagnetic field are analyzed. The calculation method of geomagnetically induced current (GIC) is provided. Then, the effects and mechanisms of typical primary power equipment, such as power transformers, current transformers, circuit breakers, etc. under extreme GIC conditions are summarized. Next, the extreme GIC injection devices and simulated experiment methods are discussed. And the experimental and simulation results acquired by Defense Threat Reduction Agency (DTRA) and Electric Power Research Institute (EPRI) are also discussed, as well as the power system effects simulation and assessment. Finally, we summarized the main conclusions reached by the present work, and analyzed the future research from the perspective of effects mechanism, primary power equipment characteristics, simulated experimental methods, and system-level effects assessment.
, Available online ,
doi: 10.11884/HPLPB202436.240034
Abstract:
Accurate measurement of the intense pulse electron beam is required by upgrade of linear induction accelerator. This is achieved by not only the technology of beam position monitor (BPM) design and assamble, but also the calibration of BPM. This paper describes the research of calibration technology based on the measuring principle of intense pulse electron beam position monitor in linear induction accelerator. Theoretic method is used to calculate calibrated effects in different signal calculation, polynomial fit and calibration. Characteristic plane calibration is provided according to the analytic results. In the system of BPM position calibration,The No.23RRM (resistive ring monitor) of multi-pulse electron linear induction accelarator is calibrated in different calibration and experimental data processed in different method. The experimental results validate the theoretic results. The calibration method of intense pulse electron beam position monitor is decided according to the results of research.
Accurate measurement of the intense pulse electron beam is required by upgrade of linear induction accelerator. This is achieved by not only the technology of beam position monitor (BPM) design and assamble, but also the calibration of BPM. This paper describes the research of calibration technology based on the measuring principle of intense pulse electron beam position monitor in linear induction accelerator. Theoretic method is used to calculate calibrated effects in different signal calculation, polynomial fit and calibration. Characteristic plane calibration is provided according to the analytic results. In the system of BPM position calibration,The No.23RRM (resistive ring monitor) of multi-pulse electron linear induction accelarator is calibrated in different calibration and experimental data processed in different method. The experimental results validate the theoretic results. The calibration method of intense pulse electron beam position monitor is decided according to the results of research.
, Available online ,
doi: 10.11884/HPLPB202436.230425
Abstract:
The Institute of High Energy Physics of the Chinese Academy of Sciences completed the research and development of the high quality factor 1.3 GHz superconducting cryomodule in June 2023, taking the lead in the world to realize the technical route of the medium temperature baking. Eight 1.3 GHz 9-cell superconducting cavities with the medium temperature baking process are integrated. During the integration test of the cryomodule, the temperature of the high-order mode (HOM) coupler of the superconducting cavity was abnormal, which made the superconducting cavity unable to work stably under high gradient. In this paper, the electromagnetic analysis of the higher-order mode coupler is carried out by the HFSS software and eigenmode Solver in CST software and the thermal analysis of the high-order mode coupler is carried out by theory and Ansys Workbench software. Combining with the high-power experiment of cavity, the reason that caused the abnormal performance of the superconducting cavity was found. Also, the cooling structure of the HOM coupler in the superconducting cavity was further optimized to solve the instability of the superconducting cavity under high gradient in the module.
The Institute of High Energy Physics of the Chinese Academy of Sciences completed the research and development of the high quality factor 1.3 GHz superconducting cryomodule in June 2023, taking the lead in the world to realize the technical route of the medium temperature baking. Eight 1.3 GHz 9-cell superconducting cavities with the medium temperature baking process are integrated. During the integration test of the cryomodule, the temperature of the high-order mode (HOM) coupler of the superconducting cavity was abnormal, which made the superconducting cavity unable to work stably under high gradient. In this paper, the electromagnetic analysis of the higher-order mode coupler is carried out by the HFSS software and eigenmode Solver in CST software and the thermal analysis of the high-order mode coupler is carried out by theory and Ansys Workbench software. Combining with the high-power experiment of cavity, the reason that caused the abnormal performance of the superconducting cavity was found. Also, the cooling structure of the HOM coupler in the superconducting cavity was further optimized to solve the instability of the superconducting cavity under high gradient in the module.
, Available online ,
doi: 10.11884/HPLPB202436.240048
Abstract:
The far-field wavefront inversion exhibits degeneracy states, leading to the problem of encountering multiple solutions when recovering the wavefront. In comparison to traditional iterative algorithms, the combination of phase modulation and deep learning in the phase inversion method not only significantly reduces computational complexity but also effectively solves multi-solution problems. This method possesses strong real-time capabilities and a simple structure, showcasing its unique advantages. In this paper, different Walsh functions are used to modulate the phase, and a deep learning approach is taken to train a convolutional neural network to obtain the 4th-30th order Zernike coefficients from the modulated single-frame far-field intensity maps so as to recover the original wavefront, which solves the problem of multiple solutions of phase inversion. For the residual wavefront of the turbulent aberration of 3-15 cm atmospheric coherence length, the ratio of its RMS to the RMS of the original wavefront can reach 7.8%. In addition, this paper also deeply investigates the effects of various factors such as Zernike order, random noise, occlusion, and intensity map resolution on the wavefront recovery accuracy. The results show that this deep learning-based phase inversion method exhibits good robustness in complex environments.
The far-field wavefront inversion exhibits degeneracy states, leading to the problem of encountering multiple solutions when recovering the wavefront. In comparison to traditional iterative algorithms, the combination of phase modulation and deep learning in the phase inversion method not only significantly reduces computational complexity but also effectively solves multi-solution problems. This method possesses strong real-time capabilities and a simple structure, showcasing its unique advantages. In this paper, different Walsh functions are used to modulate the phase, and a deep learning approach is taken to train a convolutional neural network to obtain the 4th-30th order Zernike coefficients from the modulated single-frame far-field intensity maps so as to recover the original wavefront, which solves the problem of multiple solutions of phase inversion. For the residual wavefront of the turbulent aberration of 3-15 cm atmospheric coherence length, the ratio of its RMS to the RMS of the original wavefront can reach 7.8%. In addition, this paper also deeply investigates the effects of various factors such as Zernike order, random noise, occlusion, and intensity map resolution on the wavefront recovery accuracy. The results show that this deep learning-based phase inversion method exhibits good robustness in complex environments.
, Available online ,
doi: 10.11884/HPLPB202436.240001
Abstract:
In order to investigate the motion law of the plasma sheath in a dense plasma focus (DPF) device and the influence of related design parameters, this paper uses a self-developed FOI program to conduct two-dimensional magnetohydrodynamic simulation of the plasma sheath motion process and focus formation process in the Mather type discharge chamber structure, and obtains results similar to the visible light experimental images of the Livermore National Laboratory in the United States. At the same time, the influence of different pressure, current, anode radius and cathode-anode gap on the motion law of the plasma sheath is explored. The calculation results show that the plasma sheath will compress the gas radially with a certain degree of curvature, which is one of the reasons for the instability phenomenon; the axial velocity of plasma sheath is inversely proportional to the square root of pressure, and is proportional to the current. The larger the anode size of the device, the smaller the axial velocity of sheath. To increase the current, it is necessary to extend the anode length to match the focusing time with the current peak. The gap between cathode and anode has little effect on the axial motion process of plasma sheath near the anode.
In order to investigate the motion law of the plasma sheath in a dense plasma focus (DPF) device and the influence of related design parameters, this paper uses a self-developed FOI program to conduct two-dimensional magnetohydrodynamic simulation of the plasma sheath motion process and focus formation process in the Mather type discharge chamber structure, and obtains results similar to the visible light experimental images of the Livermore National Laboratory in the United States. At the same time, the influence of different pressure, current, anode radius and cathode-anode gap on the motion law of the plasma sheath is explored. The calculation results show that the plasma sheath will compress the gas radially with a certain degree of curvature, which is one of the reasons for the instability phenomenon; the axial velocity of plasma sheath is inversely proportional to the square root of pressure, and is proportional to the current. The larger the anode size of the device, the smaller the axial velocity of sheath. To increase the current, it is necessary to extend the anode length to match the focusing time with the current peak. The gap between cathode and anode has little effect on the axial motion process of plasma sheath near the anode.
, Available online ,
doi: 10.11884/HPLPB202436.230354
Abstract:
A compact repetitive pulse power source is developed as an experimental platform for high power relativistic magnetron with low magnetic field. In order to obtain better output pulse waveform with a compact structure, the pulsed power source designed based on PFN-Marx technology has a coaxial structure. A circular pulse forming net (PFN) is carried out with the impedance of 4 Ω, working voltage of 50kV, and electrical length of 53 ns, consisting of 13 ceramic capacitors with the capacitance of 1nF. Two PFN devices in series by a gas switch and an insulation plate form a circular high-voltage pulse generation module. Multiple pulse generation modules are coaxial and stacked in a metal cylinder. Inductive isolation is used between the modules. After all switches are turned on, all modules are discharged in series to generate a fast rising-time high-power square wave pulse. Moreover, repetitive operation is achieved through synchronous control of the trigger switch and charging power supply. In experiments the 22-stage PFN-Marx pulsed power source developed was charges to 51 kV, and a high-voltage square wave pulse of 516 kV was obtained on a load of 84 Ω, with pulse width (FWHM) of 104 ns, flat top of 63 ns and rising-time of 11 ns. This power source can operate stably at a repetition rate of 20 Hz for 15 seconds.
A compact repetitive pulse power source is developed as an experimental platform for high power relativistic magnetron with low magnetic field. In order to obtain better output pulse waveform with a compact structure, the pulsed power source designed based on PFN-Marx technology has a coaxial structure. A circular pulse forming net (PFN) is carried out with the impedance of 4 Ω, working voltage of 50kV, and electrical length of 53 ns, consisting of 13 ceramic capacitors with the capacitance of 1nF. Two PFN devices in series by a gas switch and an insulation plate form a circular high-voltage pulse generation module. Multiple pulse generation modules are coaxial and stacked in a metal cylinder. Inductive isolation is used between the modules. After all switches are turned on, all modules are discharged in series to generate a fast rising-time high-power square wave pulse. Moreover, repetitive operation is achieved through synchronous control of the trigger switch and charging power supply. In experiments the 22-stage PFN-Marx pulsed power source developed was charges to 51 kV, and a high-voltage square wave pulse of 516 kV was obtained on a load of 84 Ω, with pulse width (FWHM) of 104 ns, flat top of 63 ns and rising-time of 11 ns. This power source can operate stably at a repetition rate of 20 Hz for 15 seconds.
, Available online ,
doi: 10.11884/HPLPB202436.230413
Abstract:
A fluorescence target historical image data storage system based on MongoDB database was constructed to address the issues of historical image data storage, continuously increasing data generated by the system, and slow historical data retrieval speed of the Heavy Ion Research Facility in Lanzhou (HIRFL) fluorescence target. In order to save, observe and analyze fluorescence target beam images, this article establishes an EPICS based historical data archiving system to obtain PV (Process Variable) data of fluorescence target images. The obtained data is stored using MongoDB database sharding technology, and the image conversion and web page implementation are achieved through the Django framework. Image classification algorithms are applied in the system to improve data read and write speed. This system can stably obtain, store, and observe fluorescence target beam history images on HIRFL, providing convenience for beam analysis and tuning work.
A fluorescence target historical image data storage system based on MongoDB database was constructed to address the issues of historical image data storage, continuously increasing data generated by the system, and slow historical data retrieval speed of the Heavy Ion Research Facility in Lanzhou (HIRFL) fluorescence target. In order to save, observe and analyze fluorescence target beam images, this article establishes an EPICS based historical data archiving system to obtain PV (Process Variable) data of fluorescence target images. The obtained data is stored using MongoDB database sharding technology, and the image conversion and web page implementation are achieved through the Django framework. Image classification algorithms are applied in the system to improve data read and write speed. This system can stably obtain, store, and observe fluorescence target beam history images on HIRFL, providing convenience for beam analysis and tuning work.
, Available online ,
doi: 10.11884/HPLPB202436.230421
Abstract:
Aiming at the application requirements of array antenna with high-power capacity, high efficiency and low profile characteristics, a high-power capacity and high efficiency open waveguide array antenna is proposed and designed. The antenna consists of a compact 16-way waveguide power distribution network, 4×4 rectangular open waveguide unit cells and ceramic sealing radome. By designing the size of the open waveguide and loading E-plane metal bar on the surface of the open waveguide, the electric field distribution on the radiation aperture surface is more uniform, and the radiation gain of the unit cell is improved. The step matching structure is used to realize the size transformation from the output port of the waveguide power distribution network to the interface of the open waveguide unit cell, and the impedance bandwidth of the system is improved. The ceramic radome loaded on the array keeps the interior of the antenna in a vacuum state and improves the power capacity of the antenna. According to the application requirements of X-band high-power array antenna, a 16-element open waveguide array with a center frequency of 9.5 GHz is optimized and designed, the simulation results show that the aperture efficiency is greater than 90% and the reflection coefficient is less than -13.9 dB in the range of 9.25～9.65 GHz. The antenna is processed and tested, the measured antenna reflection curve and radiation pattern at the center frequency are in good agreement with the simulation results, the antenna gain at the center frequency is 21.7 dBi. The overall profile height of the antenna is twice the wavelengths at the central frequency, and the power capacity in vacuum obtained by simulation is 40 MW, which has the characteristics of high power capacity, high efficiency and low profile.
Aiming at the application requirements of array antenna with high-power capacity, high efficiency and low profile characteristics, a high-power capacity and high efficiency open waveguide array antenna is proposed and designed. The antenna consists of a compact 16-way waveguide power distribution network, 4×4 rectangular open waveguide unit cells and ceramic sealing radome. By designing the size of the open waveguide and loading E-plane metal bar on the surface of the open waveguide, the electric field distribution on the radiation aperture surface is more uniform, and the radiation gain of the unit cell is improved. The step matching structure is used to realize the size transformation from the output port of the waveguide power distribution network to the interface of the open waveguide unit cell, and the impedance bandwidth of the system is improved. The ceramic radome loaded on the array keeps the interior of the antenna in a vacuum state and improves the power capacity of the antenna. According to the application requirements of X-band high-power array antenna, a 16-element open waveguide array with a center frequency of 9.5 GHz is optimized and designed, the simulation results show that the aperture efficiency is greater than 90% and the reflection coefficient is less than -13.9 dB in the range of 9.25～9.65 GHz. The antenna is processed and tested, the measured antenna reflection curve and radiation pattern at the center frequency are in good agreement with the simulation results, the antenna gain at the center frequency is 21.7 dBi. The overall profile height of the antenna is twice the wavelengths at the central frequency, and the power capacity in vacuum obtained by simulation is 40 MW, which has the characteristics of high power capacity, high efficiency and low profile.
, Available online ,
doi: 10.11884/HPLPB202436.240022
Abstract:
The repetitive narrow pulse signal generator with a sub-nanosecond front, high-voltage amplitude, and approximately Gaussian single-cycle waveform is extensively applied in areas such as ultra-wideband detection and electromagnetic compatibility testing. This paper introduces the design of an all-solid-state repetitive pulse generator utilizing a Marx circuit architecture, which incorporates components like mica capacitors, avalanche transistors, surface-mount technology resistors, and inductors. To meet the signal output specifications, the printed circuit board layout and microstrip lines have been optimized. Through fine-tuning the matching circuit element parameters, the generator successfully delivers a unipolar negative pulse signal with a peak value of approximately 1 kV, a pulse width of around 650 ps, a leading edge of approximately 450 ps, and a trailing edge of about 700 ps across a 50 Ω resistive load. The resulting pulse waveform exhibits similar, smooth, and steep leading and trailing edges, achieving a repetition rate of 10 kHz. Both the peak value and full width at half maximum jitters are maintained at less than 10%.
The repetitive narrow pulse signal generator with a sub-nanosecond front, high-voltage amplitude, and approximately Gaussian single-cycle waveform is extensively applied in areas such as ultra-wideband detection and electromagnetic compatibility testing. This paper introduces the design of an all-solid-state repetitive pulse generator utilizing a Marx circuit architecture, which incorporates components like mica capacitors, avalanche transistors, surface-mount technology resistors, and inductors. To meet the signal output specifications, the printed circuit board layout and microstrip lines have been optimized. Through fine-tuning the matching circuit element parameters, the generator successfully delivers a unipolar negative pulse signal with a peak value of approximately 1 kV, a pulse width of around 650 ps, a leading edge of approximately 450 ps, and a trailing edge of about 700 ps across a 50 Ω resistive load. The resulting pulse waveform exhibits similar, smooth, and steep leading and trailing edges, achieving a repetition rate of 10 kHz. Both the peak value and full width at half maximum jitters are maintained at less than 10%.
, Available online ,
doi: 10.11884/HPLPB202436.230285
Abstract:
This article investigates the Ricker pulse to address the issue of low radiation efficiency in time-domain antennas. Firstly, it highlights the high center frequency of the Ricker pulse, which is advantageous for improving antenna radiation efficiency. This article then proceeds to explain the power synthesis method for generating Ricker pulses, starting with precise time delay control. It describes the design of a unipolar pulse and the optimization of its falling edge using the sharpening capacitor method. With this unipolar pulse as a foundation, a Ricker pulse is designed, featuring a peak-to-peak value of 5.1 kV, a main peak half-width of 350 ps, and a center frequency of 0.5 GHz. To verify the correctness of the analysis, the article proposes a simple method to calculate the radiation efficiency of all-metal time-domain antennas. Both the designed Ricker pulse and a single-pole pulse with the same pulse width are used to excite the same antenna. The results demonstrate that the amplitude radiation efficiency of the single-pole pulse is only about 60%. In contrast, the Ricker pulse achieves over 80% efficiency. Similarly, the power radiation efficiency of the single-pole pulse is less than 40%, while the Ricker pulse can exceed 60% efficiency. This article derives a theoretical formula for the optimal delay of synthesizing high-order Gaussian pulses and proposes a simplified method for calculating the time-domain radiation efficiency of all-metal antennas. The utilization of Ricker pulses as excitation has proven to be highly effective in enhancing the radiation efficiency of antennas, thereby minimizing the potential damage to transmission systems caused by reflected power. Additionally, this technique holds immense value in antenna miniaturization and exhibits promising applications in time-domain technologies like ground penetrating radar and high-power microwave sources.
This article investigates the Ricker pulse to address the issue of low radiation efficiency in time-domain antennas. Firstly, it highlights the high center frequency of the Ricker pulse, which is advantageous for improving antenna radiation efficiency. This article then proceeds to explain the power synthesis method for generating Ricker pulses, starting with precise time delay control. It describes the design of a unipolar pulse and the optimization of its falling edge using the sharpening capacitor method. With this unipolar pulse as a foundation, a Ricker pulse is designed, featuring a peak-to-peak value of 5.1 kV, a main peak half-width of 350 ps, and a center frequency of 0.5 GHz. To verify the correctness of the analysis, the article proposes a simple method to calculate the radiation efficiency of all-metal time-domain antennas. Both the designed Ricker pulse and a single-pole pulse with the same pulse width are used to excite the same antenna. The results demonstrate that the amplitude radiation efficiency of the single-pole pulse is only about 60%. In contrast, the Ricker pulse achieves over 80% efficiency. Similarly, the power radiation efficiency of the single-pole pulse is less than 40%, while the Ricker pulse can exceed 60% efficiency. This article derives a theoretical formula for the optimal delay of synthesizing high-order Gaussian pulses and proposes a simplified method for calculating the time-domain radiation efficiency of all-metal antennas. The utilization of Ricker pulses as excitation has proven to be highly effective in enhancing the radiation efficiency of antennas, thereby minimizing the potential damage to transmission systems caused by reflected power. Additionally, this technique holds immense value in antenna miniaturization and exhibits promising applications in time-domain technologies like ground penetrating radar and high-power microwave sources.
, Available online ,
doi: 10.11884/HPLPB202436.230422
Abstract:
To investigate the spatial distribution characteristics of active particles in atmospheric pressure pulse driven plasma jet, a coaxial double ring plasma jet reactor was used. Under external pulsed power excitation, the relative intensity changes of characteristic peaks of each active particle in different ionization regions along the axial space were studied. The results show that active particle characteristic peaks such as NO, OH, N2, N2+, He, can be detected at all measurement points of the pulse excited plasma jet, with the emission spectral bands and characteristic peaks corresponding to OH, N2, N2+ particles being more significant; In the upstream ionization section between the high-voltage electrode and the grounding electrode, the relative intensities of characteristic peaks of active particles NO, OH and N2 are higher near the high-voltage electrode and grounding electrode, while lower in the middle of the upstream ionization section. The relative intensities of characteristic peaks of different levels of He and N2+ gradually decrease along the airflow direction; In the midstream ionization section from the grounding electrode to the reactor nozzle, the axial distribution of relative intensities of active particles NO, OH and characteristic peaks of different energy levels N2, N2+ and He shows a gradually decreasing trend with the direction of the airflow; In the downstream ionization section from the reactor nozzle to the end of the plasma jet, the axial distribution of the relative intensity of the characteristic peaks of active particles OH and NO gradually weakens with the direction of gas flow. The relative intensity of the characteristic peaks of different energy levels N2, N2+ and He shows a pattern of first increasing and then decreasing, providing strong support for the in-depth study of the energy transfer process and reaction mechanism of pulse driven plasma jet.
To investigate the spatial distribution characteristics of active particles in atmospheric pressure pulse driven plasma jet, a coaxial double ring plasma jet reactor was used. Under external pulsed power excitation, the relative intensity changes of characteristic peaks of each active particle in different ionization regions along the axial space were studied. The results show that active particle characteristic peaks such as NO, OH, N2, N2+, He, can be detected at all measurement points of the pulse excited plasma jet, with the emission spectral bands and characteristic peaks corresponding to OH, N2, N2+ particles being more significant; In the upstream ionization section between the high-voltage electrode and the grounding electrode, the relative intensities of characteristic peaks of active particles NO, OH and N2 are higher near the high-voltage electrode and grounding electrode, while lower in the middle of the upstream ionization section. The relative intensities of characteristic peaks of different levels of He and N2+ gradually decrease along the airflow direction; In the midstream ionization section from the grounding electrode to the reactor nozzle, the axial distribution of relative intensities of active particles NO, OH and characteristic peaks of different energy levels N2, N2+ and He shows a gradually decreasing trend with the direction of the airflow; In the downstream ionization section from the reactor nozzle to the end of the plasma jet, the axial distribution of the relative intensity of the characteristic peaks of active particles OH and NO gradually weakens with the direction of gas flow. The relative intensity of the characteristic peaks of different energy levels N2, N2+ and He shows a pattern of first increasing and then decreasing, providing strong support for the in-depth study of the energy transfer process and reaction mechanism of pulse driven plasma jet.
, Available online ,
doi: 10.11884/HPLPB202436.240019
Abstract:
To compare the effects of different physics lists on the dose of proton boron capture therapy (PBCT) by Monte Carlo simulation Geant4. Geant4 was used to establish PBCT model with different three physics lists (FTFP, QBBC and QGSP). Compared the dose distribution of three physics lists with and without boron using an 80 MeV proton beam, as well as the nuclear reaction product data of a 3 MeV proton beam bombards pure boron. There is no significant difference in the dose distribution of the three physics lists in the water phantom with and without boron, and the consistency of the different physics models PDD’s curves are good. The PBCT nuclear reaction products obtained from FTFP physics list are significantly less than those obtained from QBBC and QGSP physics lists. The yields, mean energies and energy ranges of the alpha particles obtained from the QGSP physics list are more consistent with the actual situation than that of the QBBC physics list. The QGSP physics list in Geant4 is more suitable for MC simulation studies of PBCT, after a comprehensive evaluation of the inelastic scattering models used by the three physics lists and the simulated nuclear reaction data.
To compare the effects of different physics lists on the dose of proton boron capture therapy (PBCT) by Monte Carlo simulation Geant4. Geant4 was used to establish PBCT model with different three physics lists (FTFP, QBBC and QGSP). Compared the dose distribution of three physics lists with and without boron using an 80 MeV proton beam, as well as the nuclear reaction product data of a 3 MeV proton beam bombards pure boron. There is no significant difference in the dose distribution of the three physics lists in the water phantom with and without boron, and the consistency of the different physics models PDD’s curves are good. The PBCT nuclear reaction products obtained from FTFP physics list are significantly less than those obtained from QBBC and QGSP physics lists. The yields, mean energies and energy ranges of the alpha particles obtained from the QGSP physics list are more consistent with the actual situation than that of the QBBC physics list. The QGSP physics list in Geant4 is more suitable for MC simulation studies of PBCT, after a comprehensive evaluation of the inelastic scattering models used by the three physics lists and the simulated nuclear reaction data.
, Available online ,
doi: 10.11884/HPLPB202436.230341
Abstract:
An off-line calibration platform is designed based on the requirement of off-line calibration of induction cavity azimuthal transmission line current probe.The analog device is a flat-plate transmission line structure, which has lower distortion than on-line calibration.The source of cross-platform calibration error is analyzed, and the measures to reduce the error are put forward.The analysis shows that the installation eccentricity and probe longitudinal installation depth are the biggest sources of cross-platform calibration error, which need to be paid attention to in engineering design. An off-line calibration platform is established and the error analysis is carried out. The result of 3.3% cross-platform calibration error is obtained.
An off-line calibration platform is designed based on the requirement of off-line calibration of induction cavity azimuthal transmission line current probe.The analog device is a flat-plate transmission line structure, which has lower distortion than on-line calibration.The source of cross-platform calibration error is analyzed, and the measures to reduce the error are put forward.The analysis shows that the installation eccentricity and probe longitudinal installation depth are the biggest sources of cross-platform calibration error, which need to be paid attention to in engineering design. An off-line calibration platform is established and the error analysis is carried out. The result of 3.3% cross-platform calibration error is obtained.
, Available online ,
doi: 10.11884/HPLPB202436.230426
Abstract:
Large-scale coherent beam combining is one of the effective techniques to break through the limit of a single laser, and obtain extreme characteristics laser such as ultra-high peak/average power, ultra-high pulse energy, ultra-high spatial/spectral brightness, and the key to large-scale coherent beam combining is active phase control. Active phase control technology can control the phase of each beam actively, compensate for coherence degradation and efficiency reduction caused by phase noise, and realize high-quality combined laser. Since the proposal of coherent beam combining technology, researchers have developed a variety of active phase control methods for phase correction, among which active phase control methods suitable for large-scale coherent laser beam combining have developed rapidly. In this paper, active phase control methods for large-scale coherent laser beam combining are systematically reviewed, and the principles, characteristics, application scenarios and expansibilities of different methods are analyzed. The latest progress and landmark achievements of coherent beam combining achieved by various active phase control methods are introduced, and the breakthrough result of 6 μs closed-loop locking time for 19-channel coherent beam combining has been reported for the first time. the future development trend of large-scale active phase control methods is predicted.
Large-scale coherent beam combining is one of the effective techniques to break through the limit of a single laser, and obtain extreme characteristics laser such as ultra-high peak/average power, ultra-high pulse energy, ultra-high spatial/spectral brightness, and the key to large-scale coherent beam combining is active phase control. Active phase control technology can control the phase of each beam actively, compensate for coherence degradation and efficiency reduction caused by phase noise, and realize high-quality combined laser. Since the proposal of coherent beam combining technology, researchers have developed a variety of active phase control methods for phase correction, among which active phase control methods suitable for large-scale coherent laser beam combining have developed rapidly. In this paper, active phase control methods for large-scale coherent laser beam combining are systematically reviewed, and the principles, characteristics, application scenarios and expansibilities of different methods are analyzed. The latest progress and landmark achievements of coherent beam combining achieved by various active phase control methods are introduced, and the breakthrough result of 6 μs closed-loop locking time for 19-channel coherent beam combining has been reported for the first time. the future development trend of large-scale active phase control methods is predicted.
, Available online ,
doi: 10.11884/HPLPB202436.230436
Abstract:
With the development of adaptive optics (AO) technology in laser field, a variety of improvement measures based on software monitoring and hardware protection have been added to the classical AO system to ensure the stable and continuous light output of laser AO system. Facing the reliability challenge brought by the increase of structural complexity, how to build a system failure model to evaluate the reliability of laser AO system has become an important part of the development of laser AO system. In this paper, a dynamic fault tree (DFT) method is proposed to evaluate the reliability of laser AO system, and the dynamic fault tree is established according to the dynamic relationship between the equipment. The bottom event failure rate is estimated by combining the manufacturer information, fatigue life test and historical data. The reliability parameters of DFT are obtained by using binary decision graph and Markov model. Using DFT to analysis the reliable running time of the AO system increasing by the improvement measures, the result shows more than ten times improvement relative to the basic fault tree. During the actual system joint commissioning, no self-induced failure occurred during the expected reliable running time, which is consistent with the DFT estimate. It is proved that the reliability evaluation of laser AO system with improved measures is more accurate by using DFT method.
With the development of adaptive optics (AO) technology in laser field, a variety of improvement measures based on software monitoring and hardware protection have been added to the classical AO system to ensure the stable and continuous light output of laser AO system. Facing the reliability challenge brought by the increase of structural complexity, how to build a system failure model to evaluate the reliability of laser AO system has become an important part of the development of laser AO system. In this paper, a dynamic fault tree (DFT) method is proposed to evaluate the reliability of laser AO system, and the dynamic fault tree is established according to the dynamic relationship between the equipment. The bottom event failure rate is estimated by combining the manufacturer information, fatigue life test and historical data. The reliability parameters of DFT are obtained by using binary decision graph and Markov model. Using DFT to analysis the reliable running time of the AO system increasing by the improvement measures, the result shows more than ten times improvement relative to the basic fault tree. During the actual system joint commissioning, no self-induced failure occurred during the expected reliable running time, which is consistent with the DFT estimate. It is proved that the reliability evaluation of laser AO system with improved measures is more accurate by using DFT method.
, Available online ,
doi: 10.11884/HPLPB202436.230408
Abstract:
As the first stage of severe accidents in sodium cooled fast reactors, accurate prediction of the occurrence time and location of coolant boiling is of great significance for the safety assessment of Sodium Cooled Fast Reactors (SFR). Based on a two fluid six equation model, conservation equations are constructed for the gas-liquid two-phase flow of sodium. The evaporation-condensation model is used to characterize the interphase mass exchange, and explicit and implicit methods are used to calculate evaporation-condensation model. Constitutive relationships such as Sobolev resistance model, two phase flow heat transfer model, and phase momentum exchange are considered. A porous medium analysis approach which is suitable for simulating SFR coolant boiling was developed, and comparative verification was conducted using KNS-37 L22 loss of flow experiment data. L29 flow data is used to verify the applicability of the model. The results indicate that the established sodium boiling porous medium analysis approach can effectively simulate the boiling phenomenon. It predicts that the boiling time will be around 6.3 seconds, which is 0.2 seconds different from the experiment. The overall trend of temperature and flow rate changes are in good agreement with experimental data.
As the first stage of severe accidents in sodium cooled fast reactors, accurate prediction of the occurrence time and location of coolant boiling is of great significance for the safety assessment of Sodium Cooled Fast Reactors (SFR). Based on a two fluid six equation model, conservation equations are constructed for the gas-liquid two-phase flow of sodium. The evaporation-condensation model is used to characterize the interphase mass exchange, and explicit and implicit methods are used to calculate evaporation-condensation model. Constitutive relationships such as Sobolev resistance model, two phase flow heat transfer model, and phase momentum exchange are considered. A porous medium analysis approach which is suitable for simulating SFR coolant boiling was developed, and comparative verification was conducted using KNS-37 L22 loss of flow experiment data. L29 flow data is used to verify the applicability of the model. The results indicate that the established sodium boiling porous medium analysis approach can effectively simulate the boiling phenomenon. It predicts that the boiling time will be around 6.3 seconds, which is 0.2 seconds different from the experiment. The overall trend of temperature and flow rate changes are in good agreement with experimental data.
, Available online ,
doi: 10.11884/HPLPB202436.230433
Abstract:
The existing heterodyne power combiners are not suitable for applications that the input and output of signal need to be the same direction with limited space. In order to solve the problem, this paper designs a high-power and miniaturized heterodyne power combiner operating at frequencies of 9.3 GHz and 9.7 GHz. Based on the traditional filter-based heterodyne power combiner, the proposed design utilizes a over-mode rectangular waveguide E-plane power combiner. The waveguide filters are parallel and the input ports are also located on the same plane, so that the combiner is suitable for the specific applications. The size of the rectangular waveguide are reduced to suppress higher-order modes. Besides, the distance between mode strips is decreased in integer multiples of half-wavelength of the waveguide to compresses the overall length with high power capacity. The combiner has a length of 9.2 λ a width of 1.5 λ and a height of 2.8 λ, while λ is the wavelength corresponding to the frequency of 9.5 GHz in free space. At 9.3 GHz and 9.7 GHz, the return loss of the combiner is more than 20 dB, its combining efficiency is more than 98% , and the isolation between input ports is more than 20 dB. At microwave pulse breakdown threshold of 80 MV/m, the combiner provides power capacities of 310 MW.
The existing heterodyne power combiners are not suitable for applications that the input and output of signal need to be the same direction with limited space. In order to solve the problem, this paper designs a high-power and miniaturized heterodyne power combiner operating at frequencies of 9.3 GHz and 9.7 GHz. Based on the traditional filter-based heterodyne power combiner, the proposed design utilizes a over-mode rectangular waveguide E-plane power combiner. The waveguide filters are parallel and the input ports are also located on the same plane, so that the combiner is suitable for the specific applications. The size of the rectangular waveguide are reduced to suppress higher-order modes. Besides, the distance between mode strips is decreased in integer multiples of half-wavelength of the waveguide to compresses the overall length with high power capacity. The combiner has a length of 9.2 λ a width of 1.5 λ and a height of 2.8 λ, while λ is the wavelength corresponding to the frequency of 9.5 GHz in free space. At 9.3 GHz and 9.7 GHz, the return loss of the combiner is more than 20 dB, its combining efficiency is more than 98% , and the isolation between input ports is more than 20 dB. At microwave pulse breakdown threshold of 80 MV/m, the combiner provides power capacities of 310 MW.
, Available online ,
doi: 10.11884/HPLPB202436.230443
Abstract:
An novel ultra-wideband thin frequency selective surface (FSS) absorber loaded with lumped resistors is presented in this article. The proposed absorber consists of a single FSS lossy layer with a single resonance structure, and features thinness, ultra-wide bandwidth and polarization-insensitivity. The absorber is designed with lumped resistors loaded at positions that deviates from the central symmetry axis of the unit cell. It also features the nonuniformly wide metallic strips and the addition of branches with circular tops. All these specific design effectively enhances the bandwidth of the absorber. Both an equivalent circuit model and full wave simulation demonstrate that the proposed absorber achieves over 90% absorption in the frequency range of 6.0-26.77 GHz, with a fractional bandwidth of 126.8%. The thickness of the proposed absorber is 0.086 λL (the wavelength at the lowest frequency), which is only 1.09 times the ultimate thickness based on Rozanov’s theory. A prototype of the proposed absorber is fabricated, good agreements between experimental and simulated results are observed, validating the effectiveness of the design.
An novel ultra-wideband thin frequency selective surface (FSS) absorber loaded with lumped resistors is presented in this article. The proposed absorber consists of a single FSS lossy layer with a single resonance structure, and features thinness, ultra-wide bandwidth and polarization-insensitivity. The absorber is designed with lumped resistors loaded at positions that deviates from the central symmetry axis of the unit cell. It also features the nonuniformly wide metallic strips and the addition of branches with circular tops. All these specific design effectively enhances the bandwidth of the absorber. Both an equivalent circuit model and full wave simulation demonstrate that the proposed absorber achieves over 90% absorption in the frequency range of 6.0-26.77 GHz, with a fractional bandwidth of 126.8%. The thickness of the proposed absorber is 0.086 λL (the wavelength at the lowest frequency), which is only 1.09 times the ultimate thickness based on Rozanov’s theory. A prototype of the proposed absorber is fabricated, good agreements between experimental and simulated results are observed, validating the effectiveness of the design.
, Available online ,
doi: 10.11884/HPLPB202436.240032
Abstract:
In order to estimate the aircraft pose in complex situation, this paper proposes a new method of aircraft pose estimation based on neural network line extraction. This method uses 3D model to render images, and forms dataset through adding backgrounds. The dataset is enhanced to make the algorithm robust. The line extraction model uses convolutional neural network to extract deep features, and uses heatmap to obtain aircraft feature lines. The target pose is solved by combining the aircraft feature line, the aircraft 3D model and the perspective-n-line method. The accuracy of the line extraction model is 91% in complex background. The accuracy is 84% after adding sorts of noises. The aircraft pose is solved by using EPnL algorithm and nonlinear optimization. The average angle error is about 0.57°, and the average translation error is about 0.47% when the target is in a complex background. After adding sorts of noises to the image, the average angle error is about 2.11°, and the average translation error is about 0.93%. The aircraft pose estimation method proposed in this article can accurately predict the aircraft pose under complex backgrounds and various types of noise, and its application scenarios are more extensive.
In order to estimate the aircraft pose in complex situation, this paper proposes a new method of aircraft pose estimation based on neural network line extraction. This method uses 3D model to render images, and forms dataset through adding backgrounds. The dataset is enhanced to make the algorithm robust. The line extraction model uses convolutional neural network to extract deep features, and uses heatmap to obtain aircraft feature lines. The target pose is solved by combining the aircraft feature line, the aircraft 3D model and the perspective-n-line method. The accuracy of the line extraction model is 91% in complex background. The accuracy is 84% after adding sorts of noises. The aircraft pose is solved by using EPnL algorithm and nonlinear optimization. The average angle error is about 0.57°, and the average translation error is about 0.47% when the target is in a complex background. After adding sorts of noises to the image, the average angle error is about 2.11°, and the average translation error is about 0.93%. The aircraft pose estimation method proposed in this article can accurately predict the aircraft pose under complex backgrounds and various types of noise, and its application scenarios are more extensive.
, Available online ,
doi: 10.11884/HPLPB202436.230430
Abstract:
The combination of deep learning technology and adaptive optics technology is expected to effectively improve the wavefront correction effect and better cope with more complex environmental conditions. The research progress of applying deep learning in the direction of wavefront reconstruction and wavefront prediction is detailed, including the specific research methods and corresponding neural network structure design adopted by the researchers in these two research directions, and the performance of these neural networks in different practical application scenarios is analyzed, and the differences between the different neural network structures are compared and discussed, and the specific impacts of the structural differences are explored. The differences between the different neural network structures are compared and discussed, and the specific impacts brought by the structural differences are explored. Finally, the existing methods of deep learning in these two directions are summarized, and the future development trend of the deep integration of deep learning and adaptive optics technology is also prospected.
The combination of deep learning technology and adaptive optics technology is expected to effectively improve the wavefront correction effect and better cope with more complex environmental conditions. The research progress of applying deep learning in the direction of wavefront reconstruction and wavefront prediction is detailed, including the specific research methods and corresponding neural network structure design adopted by the researchers in these two research directions, and the performance of these neural networks in different practical application scenarios is analyzed, and the differences between the different neural network structures are compared and discussed, and the specific impacts of the structural differences are explored. The differences between the different neural network structures are compared and discussed, and the specific impacts brought by the structural differences are explored. Finally, the existing methods of deep learning in these two directions are summarized, and the future development trend of the deep integration of deep learning and adaptive optics technology is also prospected.
, Available online ,
doi: 10.11884/HPLPB202436.230306
Abstract:
With the increasing and extensive applications of high-voltage nanosecond solid-state pulse generators in various fields such as biology, industry, and environment, the pulse waveform, voltage amplitude, pulse duration, and pulse repetition frequency have become essential controllable variables for specific pulse power applications. To further reduce the size and cost of the pulsed power supply, a high-voltage nanosecond pulse modulator with high repetition frequency is proposed with positive Marx circuit, drivers with multiple pulse transformers as the core, and ns rising time. This driver enables the design of a high-voltage nanosecond pulse modulator with ns-level rise time and high repetition frequency. The proposed driver features a compact structure and eliminates the need for multiple isolated power supplies for driving. It allows the gate voltage of two MOSFETs to rise and fall rapidly and synchronously at a high repetition frequency, enabling the generation of gate voltage with controllable amplitude within one hundred nanoseconds. In the case, not only is the maximum pulse width not limited by the magnetic core saturation, but also the negative bias voltage makes switch can be reliably turned off, improving the reliability of the circuit. In addition, the influence of different turns and magnetic core materials on the driving waveform is studied. A 14-stage pulse modulator prototype is developed. Test results show that the output voltage and pulse width of the modulator based on the drivers are continuously adjustable, with the ability to change the pulse profile. The maximum output voltage reaches 5.5 kV with 100 ns to 50 ms width, minimum rise time of approximately 18 ns, and a continuous repetition frequency of 100 kHz.
With the increasing and extensive applications of high-voltage nanosecond solid-state pulse generators in various fields such as biology, industry, and environment, the pulse waveform, voltage amplitude, pulse duration, and pulse repetition frequency have become essential controllable variables for specific pulse power applications. To further reduce the size and cost of the pulsed power supply, a high-voltage nanosecond pulse modulator with high repetition frequency is proposed with positive Marx circuit, drivers with multiple pulse transformers as the core, and ns rising time. This driver enables the design of a high-voltage nanosecond pulse modulator with ns-level rise time and high repetition frequency. The proposed driver features a compact structure and eliminates the need for multiple isolated power supplies for driving. It allows the gate voltage of two MOSFETs to rise and fall rapidly and synchronously at a high repetition frequency, enabling the generation of gate voltage with controllable amplitude within one hundred nanoseconds. In the case, not only is the maximum pulse width not limited by the magnetic core saturation, but also the negative bias voltage makes switch can be reliably turned off, improving the reliability of the circuit. In addition, the influence of different turns and magnetic core materials on the driving waveform is studied. A 14-stage pulse modulator prototype is developed. Test results show that the output voltage and pulse width of the modulator based on the drivers are continuously adjustable, with the ability to change the pulse profile. The maximum output voltage reaches 5.5 kV with 100 ns to 50 ms width, minimum rise time of approximately 18 ns, and a continuous repetition frequency of 100 kHz.
, Available online ,
doi: 10.11884/HPLPB202436.230424
Abstract:
The Geant4 program was used to simulate the effect of micropore shape on the performance of CsI:Tl X-ray scintillation screen based on silicon microchannel array. The simulated scintillation screen performance parameters include: scintillation photons, bottom light output, transmission efficiency, percentage of n times total reflection, and Modulation transfer function versus spatial resolution. The shapes of the micropores were set to be square and circular during the simulation process, and the microchannel array period was the same for both hole shapes, which was 10 μm. The simulation results show that the number of scintillation photons in square micropores is better than that in circular micropores, and the number of fluorescent photons is directly proportional to the cross-sectional area of the micropores; Thickness less than 400 μm, the bottom light output of square micropores is better than that of circular micropores,.When the thickness greater than 400 μm, the situation is opposite; The transmission efficiency of circular micropores is better than that of square micropores; When the thickness of 40 and 200 μm ,the spatial resolution of the square micropores scintillation screen is better than that of the circular micropores scintillation screen with the same thickness. A square microporous CsI: Tl scintillation screen sample was prepared, and the relationship between its MTF and spatial resolution was measured. When the MTF was 0.1, the spatial resolution was 22.6 lp/mm.
The Geant4 program was used to simulate the effect of micropore shape on the performance of CsI:Tl X-ray scintillation screen based on silicon microchannel array. The simulated scintillation screen performance parameters include: scintillation photons, bottom light output, transmission efficiency, percentage of n times total reflection, and Modulation transfer function versus spatial resolution. The shapes of the micropores were set to be square and circular during the simulation process, and the microchannel array period was the same for both hole shapes, which was 10 μm. The simulation results show that the number of scintillation photons in square micropores is better than that in circular micropores, and the number of fluorescent photons is directly proportional to the cross-sectional area of the micropores; Thickness less than 400 μm, the bottom light output of square micropores is better than that of circular micropores,.When the thickness greater than 400 μm, the situation is opposite; The transmission efficiency of circular micropores is better than that of square micropores; When the thickness of 40 and 200 μm ,the spatial resolution of the square micropores scintillation screen is better than that of the circular micropores scintillation screen with the same thickness. A square microporous CsI: Tl scintillation screen sample was prepared, and the relationship between its MTF and spatial resolution was measured. When the MTF was 0.1, the spatial resolution was 22.6 lp/mm.
Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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, Available online ,
doi: 10.11884/HPLPB202436.230357
Abstract:
Lead cooled fast reactor has obvious advantages in fuel proliferation and nuclear waste treatment. For the Europe Lead-cooled System (ELSY), based on the “two-step method”, Monte Carlo software is used to generate few group component parameters, and after section correction, it is passed to the determining theory program MORPHY for core calculation. The effects of section modification and angle development order on the calculation accuracy were analyzed, and the effective multiplication factor, normalized flux level and control rod value of the ELSY core were quantified and compared. For different examples, transport correction and neutron multiplication effect correction were adopted, and the core calculation was developed with S4 order. The maximum deviation of effective multiplication factor was 38×10−5, the calculation deviation of control rod value was within 45×10−5, the maximum absolute deviation of normalized neutron flux density was 9.73%, and the average absolute deviation was less than 2%. The feasibility of MORPHY program in the physical analysis of lead-cooled fast reactor is preliminarily verified, which is of reference significance for the subsequent development and use of the program.
Lead cooled fast reactor has obvious advantages in fuel proliferation and nuclear waste treatment. For the Europe Lead-cooled System (ELSY), based on the “two-step method”, Monte Carlo software is used to generate few group component parameters, and after section correction, it is passed to the determining theory program MORPHY for core calculation. The effects of section modification and angle development order on the calculation accuracy were analyzed, and the effective multiplication factor, normalized flux level and control rod value of the ELSY core were quantified and compared. For different examples, transport correction and neutron multiplication effect correction were adopted, and the core calculation was developed with S4 order. The maximum deviation of effective multiplication factor was 38×10−5, the calculation deviation of control rod value was within 45×10−5, the maximum absolute deviation of normalized neutron flux density was 9.73%, and the average absolute deviation was less than 2%. The feasibility of MORPHY program in the physical analysis of lead-cooled fast reactor is preliminarily verified, which is of reference significance for the subsequent development and use of the program.
, Available online ,
doi: 10.11884/HPLPB202436.240031
Abstract:
The adder topology solid state modulator is a device that uses insulated gate bipolar transistors (IGBTs) to discharge the stored energy of capacitors to generate high voltage pulses. Compared with pulse forming network (PFN) type modulator, it has lots of advantages such as modularity, good stability, and long lifespan. However, the normal operation of IGBT requires the use of gate drive circuit to amplify the control signal, and the performance of the drive circuit directly affects the switching characteristics of the IGBT, ultimately affects the quality of pulse voltage, especially the turn-on jitter index of the drive circuit, which is one of the key factors affecting the pulse voltage repetition precision. Based on the operating characteristics of IGBT in the adder topology solid state modulator, the drive circuit was studied with the goal of improving pulse voltage repetition precision. The impact of turn-on jitter on voltage repetition precision was analyzed, the design principle was introduced, the drive circuit board was developed, and its working performance was experimentally tested using a discharge module. The test results indicate that the turn-on jitter of the drive circuit is 300 ps, which is three times better than commercial driving circuits. At the charging voltage of 1 kV, the discharge module discharges on a 0.5 Ω load, forming a pulse voltage with the rise time of 500 ns and the peak-to-peak value of turn-on jitter below 5 ns. When the desaturation fault occurs, the drive circuit can turn off the IGBT within 4 µs. This drive circuit meets the working requirements of high pulse repetition precision solid state modulators.
The adder topology solid state modulator is a device that uses insulated gate bipolar transistors (IGBTs) to discharge the stored energy of capacitors to generate high voltage pulses. Compared with pulse forming network (PFN) type modulator, it has lots of advantages such as modularity, good stability, and long lifespan. However, the normal operation of IGBT requires the use of gate drive circuit to amplify the control signal, and the performance of the drive circuit directly affects the switching characteristics of the IGBT, ultimately affects the quality of pulse voltage, especially the turn-on jitter index of the drive circuit, which is one of the key factors affecting the pulse voltage repetition precision. Based on the operating characteristics of IGBT in the adder topology solid state modulator, the drive circuit was studied with the goal of improving pulse voltage repetition precision. The impact of turn-on jitter on voltage repetition precision was analyzed, the design principle was introduced, the drive circuit board was developed, and its working performance was experimentally tested using a discharge module. The test results indicate that the turn-on jitter of the drive circuit is 300 ps, which is three times better than commercial driving circuits. At the charging voltage of 1 kV, the discharge module discharges on a 0.5 Ω load, forming a pulse voltage with the rise time of 500 ns and the peak-to-peak value of turn-on jitter below 5 ns. When the desaturation fault occurs, the drive circuit can turn off the IGBT within 4 µs. This drive circuit meets the working requirements of high pulse repetition precision solid state modulators.
, Available online ,
doi: 10.11884/HPLPB202436.240010
Abstract:
The preparation of Tb3Al5O12 (TAG) phosphors was fabricated by the sol-gel method. Thermal analysis data confirm that an increase in the H3BO3 molar ratio correlates with a reduction in the transition temperature of the final phase. Concurrently, scanning electron microscopy revealed that an elevated H3BO3 molar ratio results in larger phosphor particle sizes. Under the excitation wavelength of 275 nm, the emission spectrum manifests multiple peaks within the 480-650 nm range, originating from the 5d→4f transitions of Tb3+ ions. Subsequently, the phosphor@SiO2 aerogel composite luminescent material was successfully synthesized through a combination of physical doping and a supercritical drying process. This composite luminescent material exhibited a substantial increase in the internal quantum yield, reaching 63.64% compared to the standalone phosphor. Excited by a 355 nm laser source, the phosphor@SiO2 aerogel composite luminescent material demonstrated the capability for wire-free, long-distance luminescence with commendable uniformity. These findings demonstrate the potential application prospects of the phosphor@SiO2 aerogel composite luminescent material in the domain of laser emergency lighting.
The preparation of Tb3Al5O12 (TAG) phosphors was fabricated by the sol-gel method. Thermal analysis data confirm that an increase in the H3BO3 molar ratio correlates with a reduction in the transition temperature of the final phase. Concurrently, scanning electron microscopy revealed that an elevated H3BO3 molar ratio results in larger phosphor particle sizes. Under the excitation wavelength of 275 nm, the emission spectrum manifests multiple peaks within the 480-650 nm range, originating from the 5d→4f transitions of Tb3+ ions. Subsequently, the phosphor@SiO2 aerogel composite luminescent material was successfully synthesized through a combination of physical doping and a supercritical drying process. This composite luminescent material exhibited a substantial increase in the internal quantum yield, reaching 63.64% compared to the standalone phosphor. Excited by a 355 nm laser source, the phosphor@SiO2 aerogel composite luminescent material demonstrated the capability for wire-free, long-distance luminescence with commendable uniformity. These findings demonstrate the potential application prospects of the phosphor@SiO2 aerogel composite luminescent material in the domain of laser emergency lighting.
, Available online ,
doi: 10.11884/HPLPB202436.230442
Abstract:
Impacted by various factors such as geographical position, sun and atmospheric environment, it is impossible to obtain the real images of space targets under various postures and illumination conditions, let alone under the interaction between laser, sun and background light. In this paper, a real-time target image generation method under multi-light source irradiation is proposed. This method is based on the modern graphics card programming technique and frame caching object advantages. At the GPU (Graphics Processing Unit) side, shader language is used to efficiently calculate target brightness values and enhance realism under the influence of multi-light source. The open-source 3D graphics engine named OSG (Open Scene Graph) helps support 3D model files of various formats and improve the compatibility with the domestic Kirin operating system as well as common battlefield situation display software. Simulation experiments demonstrate the effectiveness and superiority of the proposed method.
Impacted by various factors such as geographical position, sun and atmospheric environment, it is impossible to obtain the real images of space targets under various postures and illumination conditions, let alone under the interaction between laser, sun and background light. In this paper, a real-time target image generation method under multi-light source irradiation is proposed. This method is based on the modern graphics card programming technique and frame caching object advantages. At the GPU (Graphics Processing Unit) side, shader language is used to efficiently calculate target brightness values and enhance realism under the influence of multi-light source. The open-source 3D graphics engine named OSG (Open Scene Graph) helps support 3D model files of various formats and improve the compatibility with the domestic Kirin operating system as well as common battlefield situation display software. Simulation experiments demonstrate the effectiveness and superiority of the proposed method.
, Available online ,
doi: 10.11884/HPLPB202436.230432
Abstract:
Aiming at the difficulty of predicting the length of rock-breaking arc plasma channel by high voltage pulse discharge, a comprehensive test platform for rock-breaking arc plasma channel by high voltage pulse discharge was constructed. The development characteristics and typical current and voltage parameters of arc plasma channel under granite-tap water combined medium were measured, and the broken region formed on the rock surface under different electrode spacing and pulse discharge times was extracted. Based on the energy balance equation, the impedance model of the arc plasma channel in rock is established. The approximate optimal solution of the impedance model parameters is obtained by iterative optimization algorithm. The relative error between the calculated results and the experimental results is less than 7%. Based on the optimized parameters, the length of plasma channel is predicted by the measured current and voltage data. The absolute error between the plasma channel length predicted by the model and the measured value is in the order of mm, and the relative error is less than 10%, which provides theoretical support for the matching design of power-electrode load in the high-voltage pulse discharge rock breaking system.
Aiming at the difficulty of predicting the length of rock-breaking arc plasma channel by high voltage pulse discharge, a comprehensive test platform for rock-breaking arc plasma channel by high voltage pulse discharge was constructed. The development characteristics and typical current and voltage parameters of arc plasma channel under granite-tap water combined medium were measured, and the broken region formed on the rock surface under different electrode spacing and pulse discharge times was extracted. Based on the energy balance equation, the impedance model of the arc plasma channel in rock is established. The approximate optimal solution of the impedance model parameters is obtained by iterative optimization algorithm. The relative error between the calculated results and the experimental results is less than 7%. Based on the optimized parameters, the length of plasma channel is predicted by the measured current and voltage data. The absolute error between the plasma channel length predicted by the model and the measured value is in the order of mm, and the relative error is less than 10%, which provides theoretical support for the matching design of power-electrode load in the high-voltage pulse discharge rock breaking system.
, Available online ,
doi: 10.11884/HPLPB202436.230423
Abstract:
In a previous work, a two-stage microstructure was proposed and demonstrated to be able to sharply improve surface flashover voltage of polymer insulators in vacuum. In this paper, the two-stage microstructure was separated into two sub-structures, i.e., surface micro-groove structure and surface micro-hole structure, to study the voltage improvement mechanism in the two-stage microstructure. Through the synthesis of a composite material, laser treatment and acid corrosion, the two-stage microstructure was prepared as well as the two sub-structures. Flashover test of the insulators with the three kinds of surface structures showed that construction of micro grooves and micro holes on the surface of insulators could both enhance the surface flashover strength and their combination could further enhance the flashover strength. The results indicate that through proper combination of different kinds of surface structures multiple suppression of the flashover could be achieved and the surface flashover voltage could be further improved.
In a previous work, a two-stage microstructure was proposed and demonstrated to be able to sharply improve surface flashover voltage of polymer insulators in vacuum. In this paper, the two-stage microstructure was separated into two sub-structures, i.e., surface micro-groove structure and surface micro-hole structure, to study the voltage improvement mechanism in the two-stage microstructure. Through the synthesis of a composite material, laser treatment and acid corrosion, the two-stage microstructure was prepared as well as the two sub-structures. Flashover test of the insulators with the three kinds of surface structures showed that construction of micro grooves and micro holes on the surface of insulators could both enhance the surface flashover strength and their combination could further enhance the flashover strength. The results indicate that through proper combination of different kinds of surface structures multiple suppression of the flashover could be achieved and the surface flashover voltage could be further improved.
, Available online ,
doi: 10.11884/HPLPB202436.230410
Abstract:
The study of vacuum surface flashover along the insulator ring was carried out. An experimental platform for vacuum insulator stack was built. The influence of flashover among insulator ring on the voltage of the vacuum insulator stack was evaluated by equivalent circuit model. Vacuum surface flashover along the three kinds of material insulator stacks were carried out, which verify the availability and reliability of the experimental platform. This work provides a reference for the engineering research of the vacuum insulator stack of pulse power device, and also provides an experimental platform for research of new insulation materials.
The study of vacuum surface flashover along the insulator ring was carried out. An experimental platform for vacuum insulator stack was built. The influence of flashover among insulator ring on the voltage of the vacuum insulator stack was evaluated by equivalent circuit model. Vacuum surface flashover along the three kinds of material insulator stacks were carried out, which verify the availability and reliability of the experimental platform. This work provides a reference for the engineering research of the vacuum insulator stack of pulse power device, and also provides an experimental platform for research of new insulation materials.
, Available online ,
doi: 10.11884/HPLPB202436.230337
Abstract:
Based on the requirement of high current multi-pulse accelerator, the surface flashover characteristics of cross-linked polystyrene (XLPS) material under burst multi-pulse in vacuum were studied experimentally. Vacuum surface flashover experiments were carried out with XLPS samples placed in flat electrodes under single pulse and three pulses with interval of 500 ns. Special phenomena such as continuous decrease of equivalent impedance of vacuum surface before flashover and continuous maintenance of flashover channel after pulse end were observed, and statistical data of vacuum surface flashover of XLPS materials under corresponding conditions were obtained. On the basis of experiments, the flashover characteristics of XLPS in vacuum under high repetition rate multi-pulse loading are analyzed, which provides experimental basis for insulation design of high repetition rate multi-pulse accelerator.
Based on the requirement of high current multi-pulse accelerator, the surface flashover characteristics of cross-linked polystyrene (XLPS) material under burst multi-pulse in vacuum were studied experimentally. Vacuum surface flashover experiments were carried out with XLPS samples placed in flat electrodes under single pulse and three pulses with interval of 500 ns. Special phenomena such as continuous decrease of equivalent impedance of vacuum surface before flashover and continuous maintenance of flashover channel after pulse end were observed, and statistical data of vacuum surface flashover of XLPS materials under corresponding conditions were obtained. On the basis of experiments, the flashover characteristics of XLPS in vacuum under high repetition rate multi-pulse loading are analyzed, which provides experimental basis for insulation design of high repetition rate multi-pulse accelerator.
, Available online ,
doi: 10.11884/HPLPB202436.230392
Abstract:
The breakdown characteristics of trigger gap for the pre-ionization switch in N2, the mixture of N2 and SF6 and SF6 atmosphere under positive and negative pulse were investigated for the higher voltage grade and bipolarity application. The relationships between the breakdown voltage and delay time of the pre-ionization gap and the pressure of different kinds of gases were obtained, and the breakdown characteristics were compared for the pre-ionization gap under positive and negative polarities. The results of the experiment demonstrated that the breakdown process of the gap in N2 was more stable, and the linearity of breakdown voltage varying with pressure in N2 was the best among the three kinds of gases. The breakdown voltage was saturated only in SF6 with the increase of gas pressure. The breakdown voltage of the gap under negative polarity was higher than that under the positive at some certain values of the pressure, and this phenomenon might suggest that there was a polarity effect upon the breakdown process of pre-ionization gap. Compared with the mixture and N2, the absolute differences between negative and positive polarity for both breakdown voltage and delay time in SF6 were relatively higher. N2 should be preferred as the insulating medium for the pre-ionization gap to reduce the synchronization delay difference of the bipolar self-triggered switches. The polarity effect of the pre-ionization gap and the distinctions among the different kinds of insulated gas medium should be paid more attention in engineering applications for the pre-ionization gap.
The breakdown characteristics of trigger gap for the pre-ionization switch in N2, the mixture of N2 and SF6 and SF6 atmosphere under positive and negative pulse were investigated for the higher voltage grade and bipolarity application. The relationships between the breakdown voltage and delay time of the pre-ionization gap and the pressure of different kinds of gases were obtained, and the breakdown characteristics were compared for the pre-ionization gap under positive and negative polarities. The results of the experiment demonstrated that the breakdown process of the gap in N2 was more stable, and the linearity of breakdown voltage varying with pressure in N2 was the best among the three kinds of gases. The breakdown voltage was saturated only in SF6 with the increase of gas pressure. The breakdown voltage of the gap under negative polarity was higher than that under the positive at some certain values of the pressure, and this phenomenon might suggest that there was a polarity effect upon the breakdown process of pre-ionization gap. Compared with the mixture and N2, the absolute differences between negative and positive polarity for both breakdown voltage and delay time in SF6 were relatively higher. N2 should be preferred as the insulating medium for the pre-ionization gap to reduce the synchronization delay difference of the bipolar self-triggered switches. The polarity effect of the pre-ionization gap and the distinctions among the different kinds of insulated gas medium should be paid more attention in engineering applications for the pre-ionization gap.
, Available online ,
doi: 10.11884/HPLPB202436.240036
Abstract:
The pseudospark switch works in the left branch of Paschen curve with low gas pressure, and it has the advantages of ns-level breakdown time, 100 kA-level pulse current and long lifetime. High pulse repetition frequency (PRF) pseudospark switch are widely used in both civil and military fields. This paper focuses on the double-pulse trigger structure and presents the design of a switch with this structure, which is tested with 10 kV anode voltage for different gas pressure, pre-trigger voltage and main trigger voltage. The corresponding relationship between the gas pressure, the two trigger voltages and trigger current are calculated respectively. In addition, the influence of pre-trigger and main trigger pulses on the trigger process is analysed. The results show that the minimum trigger voltage is only 100 V, and the switch can work stably with high repetition frequency.
The pseudospark switch works in the left branch of Paschen curve with low gas pressure, and it has the advantages of ns-level breakdown time, 100 kA-level pulse current and long lifetime. High pulse repetition frequency (PRF) pseudospark switch are widely used in both civil and military fields. This paper focuses on the double-pulse trigger structure and presents the design of a switch with this structure, which is tested with 10 kV anode voltage for different gas pressure, pre-trigger voltage and main trigger voltage. The corresponding relationship between the gas pressure, the two trigger voltages and trigger current are calculated respectively. In addition, the influence of pre-trigger and main trigger pulses on the trigger process is analysed. The results show that the minimum trigger voltage is only 100 V, and the switch can work stably with high repetition frequency.
, Available online ,
doi: 10.11884/HPLPB202436.240040
Abstract:
The working characteristics of the hydrogen thyratron and the optimization effect of the potential equalization treatment are investigated experimentally. The experiments show that the heating voltage has great influence on the working characteristics of hydrogen thyratron, on the premise of no self-discharge phenomenon, using higher heating voltage can obtain better conduction performance. The differences of trigger pulses and anode voltages have little effect on the conduction performance of hydrogen thyratron. Using resistors to equalize the voltage of hydrogen thyratron can make the voltage distribution more uniform and alleviate the phenomenon of self-discharge. The research provides reference and guidance for the use of hydrogen thyratron.
The working characteristics of the hydrogen thyratron and the optimization effect of the potential equalization treatment are investigated experimentally. The experiments show that the heating voltage has great influence on the working characteristics of hydrogen thyratron, on the premise of no self-discharge phenomenon, using higher heating voltage can obtain better conduction performance. The differences of trigger pulses and anode voltages have little effect on the conduction performance of hydrogen thyratron. Using resistors to equalize the voltage of hydrogen thyratron can make the voltage distribution more uniform and alleviate the phenomenon of self-discharge. The research provides reference and guidance for the use of hydrogen thyratron.
, Available online ,
doi: 10.11884/HPLPB202436.230347
Abstract:
To meet the requirements of multi-channel precise synchronous trigger switch, photo conductive semiconductor switch (PCSS) is combined with V/N gas switch, which takes advantage of the photoelectric isolation, low trigger threshold, low delay time jitter and photoelectric isolation of PCSS, as well as the advantages of high operating voltage and strong load capacity of V/N gas switch. The core of the combination of the two switches is that the structural parameters of the V/N gas switch match the parameters of the PCSS trigger loop. The structural capacitance, trigger loop oscillation parameters and switching electric field distribution of the V/N gas switch are analyzed and calculated. The relationship between the structural capacitance of the V/N gas switch and the oscillation loop composed of PCSS and series inductors is studied. The self-breakdown voltage curve, on-delay time and delay time jitter of the switch under different under voltage ratios are obtained. The performance of the V/N gas switch for PCSS triggering is preliminarily verified.
To meet the requirements of multi-channel precise synchronous trigger switch, photo conductive semiconductor switch (PCSS) is combined with V/N gas switch, which takes advantage of the photoelectric isolation, low trigger threshold, low delay time jitter and photoelectric isolation of PCSS, as well as the advantages of high operating voltage and strong load capacity of V/N gas switch. The core of the combination of the two switches is that the structural parameters of the V/N gas switch match the parameters of the PCSS trigger loop. The structural capacitance, trigger loop oscillation parameters and switching electric field distribution of the V/N gas switch are analyzed and calculated. The relationship between the structural capacitance of the V/N gas switch and the oscillation loop composed of PCSS and series inductors is studied. The self-breakdown voltage curve, on-delay time and delay time jitter of the switch under different under voltage ratios are obtained. The performance of the V/N gas switch for PCSS triggering is preliminarily verified.
, Available online ,
doi: 10.11884/HPLPB202436.230420
Abstract:
Flash X-ray photography technology has important scenarios in military and civil fields. According to the requirement of high repetition rate of the linear induction a ccelerator, we put foruarc a pulse power source scheme based on tri-coaxial cable Blumlein lines drivien by hydrogen thyratron. A tri-coaxial cable was designed and developed. The conduction characteristics of hydrogen thyratron were studied. The verification setup for the pulse power source was built. The experimental research on kHz repetition rate pulse power source and kHz repetition rate pulse power source driving induction cavity was carried out. The results show that the tri-coaxial cable Blumlein lines pulse power source driven by hydrogen thyratron can realize the kHz repetition rate square wave output with excellent waveform quality.
Flash X-ray photography technology has important scenarios in military and civil fields. According to the requirement of high repetition rate of the linear induction a ccelerator, we put foruarc a pulse power source scheme based on tri-coaxial cable Blumlein lines drivien by hydrogen thyratron. A tri-coaxial cable was designed and developed. The conduction characteristics of hydrogen thyratron were studied. The verification setup for the pulse power source was built. The experimental research on kHz repetition rate pulse power source and kHz repetition rate pulse power source driving induction cavity was carried out. The results show that the tri-coaxial cable Blumlein lines pulse power source driven by hydrogen thyratron can realize the kHz repetition rate square wave output with excellent waveform quality.
, Available online ,
doi: 10.11884/HPLPB202436.240045
Abstract:
This paper proposes a design method for a high-power pulsed power supply for YAG laser systems, which is capable of realizing high-energy repetitive pulse with flexible voltage regulations. The power supply consists of an LC resonant converter as the charging network and a thyristor-based pulse forming network. Based on the proposed design approach, a 7 kW prototype is developed, which is able to output maximum voltage of 2.2 kV with a repetitive frequency ranged from 1 to 10 Hz. Moreover, the developed power supply is able to release up to 700 J of the energy on the xenon lamp.
This paper proposes a design method for a high-power pulsed power supply for YAG laser systems, which is capable of realizing high-energy repetitive pulse with flexible voltage regulations. The power supply consists of an LC resonant converter as the charging network and a thyristor-based pulse forming network. Based on the proposed design approach, a 7 kW prototype is developed, which is able to output maximum voltage of 2.2 kV with a repetitive frequency ranged from 1 to 10 Hz. Moreover, the developed power supply is able to release up to 700 J of the energy on the xenon lamp.
, Available online ,
doi: 10.11884/HPLPB202436.230295
Abstract:
LC series resonant high voltage constant current charging power supply can realize high efficiency and fast charging of the capacitor and has an excellent capacity of anti-load short-circuit, hence it has extensive application prospects in high repetition frequency pulsed power systems. The efficiency of the charging power supply is a crucial factor to determine the ability of the system to operate at repetition rate. Improving efficiency is the primary goal of designing high-voltage capacitor charging power supply. According to the working principle of LC series resonant circuit, it is analyzed that the operating mode of power supply, the switching frequency of the inverter bridge and the distribution parameters of the high-frequency transformer are the main ingredients affecting the efficiency. For a DC power supply with a power of 10 kW and an output voltage of 40 kV, the main circuit parameters were calculated and the circuit model was established using Pspice to verify its accuracy. The soft switching technology was used to reduce the switching loss, and the high frequency transformer with smaller distribution parameters was designed to further improve the efficiency. On this basis, the overall structure design of the power supply was completed. Finally, the charging characteristics of the power supply were tested. Experimental tests indicate that the power supply can charge a 0.1 µF capacitor to 39.5 kV within 37 ms, and the charging efficiency of the power supply is 87.1%.
LC series resonant high voltage constant current charging power supply can realize high efficiency and fast charging of the capacitor and has an excellent capacity of anti-load short-circuit, hence it has extensive application prospects in high repetition frequency pulsed power systems. The efficiency of the charging power supply is a crucial factor to determine the ability of the system to operate at repetition rate. Improving efficiency is the primary goal of designing high-voltage capacitor charging power supply. According to the working principle of LC series resonant circuit, it is analyzed that the operating mode of power supply, the switching frequency of the inverter bridge and the distribution parameters of the high-frequency transformer are the main ingredients affecting the efficiency. For a DC power supply with a power of 10 kW and an output voltage of 40 kV, the main circuit parameters were calculated and the circuit model was established using Pspice to verify its accuracy. The soft switching technology was used to reduce the switching loss, and the high frequency transformer with smaller distribution parameters was designed to further improve the efficiency. On this basis, the overall structure design of the power supply was completed. Finally, the charging characteristics of the power supply were tested. Experimental tests indicate that the power supply can charge a 0.1 µF capacitor to 39.5 kV within 37 ms, and the charging efficiency of the power supply is 87.1%.
, Available online ,
doi: 10.11884/HPLPB202436.240020
Abstract:
Flash X-ray radiography is often used to photograph the internal structure and hydrodynamic behavior of high-speed moving objects, and has gradually expanded to the fields of industrial flaw detection, precision system state detection and so on. This paper summarizes the research process and progress of small flash X-ray machine (SFXM), relating to four main technical routes of Marx generator, pulse forming line, fast pulse linear transformer, high-voltage transformer, and two key components of X-ray diode and switches. The research status of small flash X-ray radiography system is discussed, and the shortcomings of mature commercial small X-ray machines abroad and domestic commercial products are explored, The development trend of SFXM in the future is analyzed, which provides reference and basis for the research and development of SFXM and the exploration of commercial popularization.
Flash X-ray radiography is often used to photograph the internal structure and hydrodynamic behavior of high-speed moving objects, and has gradually expanded to the fields of industrial flaw detection, precision system state detection and so on. This paper summarizes the research process and progress of small flash X-ray machine (SFXM), relating to four main technical routes of Marx generator, pulse forming line, fast pulse linear transformer, high-voltage transformer, and two key components of X-ray diode and switches. The research status of small flash X-ray radiography system is discussed, and the shortcomings of mature commercial small X-ray machines abroad and domestic commercial products are explored, The development trend of SFXM in the future is analyzed, which provides reference and basis for the research and development of SFXM and the exploration of commercial popularization.
, Available online ,
doi: 10.11884/HPLPB202436.230360
Abstract:
To increase the output voltage and reduce the volume and cost of the high voltage damped oscillator, a 4×4 stage self-triggering Marx structure damped oscillator model is established in this paper. In this model, the main switch of each stage adopts series IGBTs module based on capacitor trigger mode. Only one isolated signal is provided to control the turn-on and turn-off of the primary discharge switch tube. The grid of the adjacent discharge tube is automatically charged and discharged through the interstage capacitance to make it turn-on and turn-off. The model improves the working voltage of Marx single stage and simplifies the driving circuit of each stage, and solves the problem of dynamic and static voltage equalization of switching tube by adding buffer circuit. Based on this topology, a prototype of a high-voltage damped oscillator is built, which outputs 16 kV damped oscillation waveform with a frequency of 1 MHz on an inductive load. The rise time of the waveform is about 75 ns, and the repetition frequency is 500 Hz. The prototype is small in size and stable in operation, which verifies the feasibility of the scheme.
To increase the output voltage and reduce the volume and cost of the high voltage damped oscillator, a 4×4 stage self-triggering Marx structure damped oscillator model is established in this paper. In this model, the main switch of each stage adopts series IGBTs module based on capacitor trigger mode. Only one isolated signal is provided to control the turn-on and turn-off of the primary discharge switch tube. The grid of the adjacent discharge tube is automatically charged and discharged through the interstage capacitance to make it turn-on and turn-off. The model improves the working voltage of Marx single stage and simplifies the driving circuit of each stage, and solves the problem of dynamic and static voltage equalization of switching tube by adding buffer circuit. Based on this topology, a prototype of a high-voltage damped oscillator is built, which outputs 16 kV damped oscillation waveform with a frequency of 1 MHz on an inductive load. The rise time of the waveform is about 75 ns, and the repetition frequency is 500 Hz. The prototype is small in size and stable in operation, which verifies the feasibility of the scheme.
, Available online ,
doi: 10.11884/HPLPB202436.240053
Abstract:
This review article aims at summarizing the basic principles of circuit methods used in compact pulsed-power generators. The concept of energy storage and voltage adding are explained followed by the descriptions on switching unit design and control signal generation. Some examples of applications of these circuit methods are given, including Marx circuit using capacitor energy storage, Marx circuit using inductive energy storage, Marx circuit using hybrid energy storage, linear transformer driver (LTD) circuit using capacitive energy storage and LTD circuit using inductive energy storage.
This review article aims at summarizing the basic principles of circuit methods used in compact pulsed-power generators. The concept of energy storage and voltage adding are explained followed by the descriptions on switching unit design and control signal generation. Some examples of applications of these circuit methods are given, including Marx circuit using capacitor energy storage, Marx circuit using inductive energy storage, Marx circuit using hybrid energy storage, linear transformer driver (LTD) circuit using capacitive energy storage and LTD circuit using inductive energy storage.
, Available online ,
doi: 10.11884/HPLPB202436.230353
Abstract:
The high-precision synchronization system is one of the key factors for the accelerator to generate high-quality beams. Based on the existing continuous laser carrier synchronization system of Tsinghua University, this paper analyzes the long-term drift of the reference microwave signal phase difference between different receiving ends, that is, the slow drift of the synchronization system. An electro-optic modulator (EOM) bias voltage control method based on the amplitude of the reference microwave signal at the receiving end was proposed to suppress the slow drift. After adopting this method, the slow drift of the L-band (1300 MHz) synchronization system of Tsinghua University’s VHF band photocathode electron gun test platform was suppressed to 10.45 fs@24 h, and the slow drift of the S-band (2 856 MHz) synchronization system of Tsinghua University’s Thomson Scattering Facility (TTX) was suppressed to 10.53 fs@24 h. Moreover, this method can make the entire synchronization system work in a room temperature environment, effectively improving the adaptability of the synchronization system to the working environment temperature.
The high-precision synchronization system is one of the key factors for the accelerator to generate high-quality beams. Based on the existing continuous laser carrier synchronization system of Tsinghua University, this paper analyzes the long-term drift of the reference microwave signal phase difference between different receiving ends, that is, the slow drift of the synchronization system. An electro-optic modulator (EOM) bias voltage control method based on the amplitude of the reference microwave signal at the receiving end was proposed to suppress the slow drift. After adopting this method, the slow drift of the L-band (1300 MHz) synchronization system of Tsinghua University’s VHF band photocathode electron gun test platform was suppressed to 10.45 fs@24 h, and the slow drift of the S-band (2 856 MHz) synchronization system of Tsinghua University’s Thomson Scattering Facility (TTX) was suppressed to 10.53 fs@24 h. Moreover, this method can make the entire synchronization system work in a room temperature environment, effectively improving the adaptability of the synchronization system to the working environment temperature.
, Available online ,
doi: 10.11884/HPLPB202436.230363
Abstract:
The classical Jiles-Atherton (J-A) equation has been modified through theoretical analysis, which enhances its adaptability under pulsed conditions. Hysteresis loops of Fe-based nanocrystalline cores are measured at different magnetization rates by using an experimental platform for pulsed magnetization properties. The genetic algorithm (GA) is used for J-A parameter identification under pulsed excitation, and the validity of the modified J-A equations is verified by fitting the algorithmically simulated hysteresis loops to the experimentally tested hysteresis loop dataset. Finally, the J-A parameter obtained by GA optimization are applied to the definition of magnetic core parameters in the field-circuit coupling model of the pulse transformer, the simulation and experimental errors when the primary voltage of the pulse transformer is 1.5 kV are analyzed. The results show that the pulse front error of the output waveform is 3.33% and the amplitude error is 2.91%, which is more accurate than the conventional nonlinear solving method of J-A parameter. This indicates that the optimized J-A parameter can be better applied to the modeling and simulation of magnetic-containing components in pulsed power systems.
The classical Jiles-Atherton (J-A) equation has been modified through theoretical analysis, which enhances its adaptability under pulsed conditions. Hysteresis loops of Fe-based nanocrystalline cores are measured at different magnetization rates by using an experimental platform for pulsed magnetization properties. The genetic algorithm (GA) is used for J-A parameter identification under pulsed excitation, and the validity of the modified J-A equations is verified by fitting the algorithmically simulated hysteresis loops to the experimentally tested hysteresis loop dataset. Finally, the J-A parameter obtained by GA optimization are applied to the definition of magnetic core parameters in the field-circuit coupling model of the pulse transformer, the simulation and experimental errors when the primary voltage of the pulse transformer is 1.5 kV are analyzed. The results show that the pulse front error of the output waveform is 3.33% and the amplitude error is 2.91%, which is more accurate than the conventional nonlinear solving method of J-A parameter. This indicates that the optimized J-A parameter can be better applied to the modeling and simulation of magnetic-containing components in pulsed power systems.
, Available online ,
doi: 10.11884/HPLPB202436.230140
Abstract:
The Tm3+ gain medium with high doping concentration can improve the quantum efficiency of the laser through the cross relaxation process, but it also increases the energy loss caused by energy up-conversion and limits the improvement of laser efficiency. The fluorescence characteristics and laser performance of Tm:SrF2 crystal are studied. Under laser-diode (LD) end-pumping, a continuous-wave laser with a maximum output power of 2.99 W and a slope efficiency of up to 82.1% is realized. The pump threshold of the laser is 0.81 W, and the center wavelength is 1851 nm. Electro-optic Q-switching of the Tm:SrF2 laser is demonstrated. At the repetition rate of 500 Hz, a maximum pulse energy of 1.02 mJ and a minimum pulse width of 45 ns are achieved, resulting in a peak power of 22.67 kW. The experimental results indicate that the Tm:SrF2 laser based on LD pumping has very high efficiency and is expected to be an ideal pump source for optical parametric oscillators (OPOs) and optical parametric amplifiers (OPAs).
The Tm3+ gain medium with high doping concentration can improve the quantum efficiency of the laser through the cross relaxation process, but it also increases the energy loss caused by energy up-conversion and limits the improvement of laser efficiency. The fluorescence characteristics and laser performance of Tm:SrF2 crystal are studied. Under laser-diode (LD) end-pumping, a continuous-wave laser with a maximum output power of 2.99 W and a slope efficiency of up to 82.1% is realized. The pump threshold of the laser is 0.81 W, and the center wavelength is 1851 nm. Electro-optic Q-switching of the Tm:SrF2 laser is demonstrated. At the repetition rate of 500 Hz, a maximum pulse energy of 1.02 mJ and a minimum pulse width of 45 ns are achieved, resulting in a peak power of 22.67 kW. The experimental results indicate that the Tm:SrF2 laser based on LD pumping has very high efficiency and is expected to be an ideal pump source for optical parametric oscillators (OPOs) and optical parametric amplifiers (OPAs).
, Available online ,
doi: 10.11884/HPLPB202436.230316
Abstract:
The structural models of Si-doped glow discharge polymer (Si-GDP) were established using reactive force field molecular dynamics simulation (ReaxFF MD), and the effects of silicon content, hydrogen content, and density on its hybrid carbon bonding and mechanical properties were investigated. The results show that with the silicon content increasing, the molecules tend to form a silicon-containing macromolecule, and the types and number of small molecules decrease, the silicon content improves the mechanical properties by promoting the binding of carbon and silicon atoms and inhibiting the formation of end-group sp3CH3. Besides, species such as ·C2H3, ·C3H5 and ·Si(CH3)3 were found during the formation of Si-GDP, which were in good agreement with the thin film deposition experiment of glow discharge polymer. The hydrogen content is measured as the atomic ratio of hydrogen to carbon and silicon, as the ratio grows, the number of model molecules did not change significantly, the ratio of sp3C and sp3CH3 increased, and the hydrogen content decreased the mechanical properties mainly by promoting the formation of sp3CH3. With the density increasing, the number of molecular species in the model did not change much, and the proportion of sp2C in the model was significantly increased, while the proportion of sp3C was slightly increased, the mechanical properties of Si-doped hydrogenated amorphous carbon were mainly improved by increasing the proportion of sp2C. This study provides an example for constructing Si-GDP by ReaxFF MD, and may provide a new method and reference for evaluating the structure and mechanical properties of Si-GDP.
The structural models of Si-doped glow discharge polymer (Si-GDP) were established using reactive force field molecular dynamics simulation (ReaxFF MD), and the effects of silicon content, hydrogen content, and density on its hybrid carbon bonding and mechanical properties were investigated. The results show that with the silicon content increasing, the molecules tend to form a silicon-containing macromolecule, and the types and number of small molecules decrease, the silicon content improves the mechanical properties by promoting the binding of carbon and silicon atoms and inhibiting the formation of end-group sp3CH3. Besides, species such as ·C2H3, ·C3H5 and ·Si(CH3)3 were found during the formation of Si-GDP, which were in good agreement with the thin film deposition experiment of glow discharge polymer. The hydrogen content is measured as the atomic ratio of hydrogen to carbon and silicon, as the ratio grows, the number of model molecules did not change significantly, the ratio of sp3C and sp3CH3 increased, and the hydrogen content decreased the mechanical properties mainly by promoting the formation of sp3CH3. With the density increasing, the number of molecular species in the model did not change much, and the proportion of sp2C in the model was significantly increased, while the proportion of sp3C was slightly increased, the mechanical properties of Si-doped hydrogenated amorphous carbon were mainly improved by increasing the proportion of sp2C. This study provides an example for constructing Si-GDP by ReaxFF MD, and may provide a new method and reference for evaluating the structure and mechanical properties of Si-GDP.
, Available online ,
doi: 10.11884/HPLPB202436.240004
Abstract:
The RbTiOPO4 crystal Raman emission at high-order Stokes with 271 cm−1 shift driven by an end-pumped passively Q-switched laser was demonstrated. The Nd:YAG and Cr4+:YAG bonding design was used to reduce the intracavity loss and make the laser system compact, so as to raise the intracavity photon density, which proved helpful for the conversion of Raman shift to high-order Stokes light. The first-Stokes laser with different Raman shifts is designed to oscillate in different cavities, and the first-Stokes laser with 687 cm−1 shift is suppressed by using the difference in cavity mode matching with the fundamental laser, and the fifth-order Stokes laser with 271 cm−1 shift is obtained. Under the pump power of 8.1 W, a 1 244 nm wavelength laser with an average output power of 230 mW was obtained, and the corresponding pulse width and pulse frequency repetition were 2.9 ns and 11.7 kHz, respectively. The 1 244 nm laser wavelength perfectly matched the OH−1 absorption peak in water, which could have significant applications in fields such as surface vegetation and planetary water detection.
The RbTiOPO4 crystal Raman emission at high-order Stokes with 271 cm−1 shift driven by an end-pumped passively Q-switched laser was demonstrated. The Nd:YAG and Cr4+:YAG bonding design was used to reduce the intracavity loss and make the laser system compact, so as to raise the intracavity photon density, which proved helpful for the conversion of Raman shift to high-order Stokes light. The first-Stokes laser with different Raman shifts is designed to oscillate in different cavities, and the first-Stokes laser with 687 cm−1 shift is suppressed by using the difference in cavity mode matching with the fundamental laser, and the fifth-order Stokes laser with 271 cm−1 shift is obtained. Under the pump power of 8.1 W, a 1 244 nm wavelength laser with an average output power of 230 mW was obtained, and the corresponding pulse width and pulse frequency repetition were 2.9 ns and 11.7 kHz, respectively. The 1 244 nm laser wavelength perfectly matched the OH−1 absorption peak in water, which could have significant applications in fields such as surface vegetation and planetary water detection.
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2024, 36: 043001.
doi: 10.11884/HPLPB202436.230375
Abstract:
In this article, the development of strong electromagnetic protection technology is reviewed in response to the strong electromagnetic environmental threats and protection reinforcement requirements faced by electronic information equipment in complex electromagnetic countermeasures environments, and the development prospects of strong electromagnetic system level comprehensive protection are proposed. Strong electromagnetic protection is a technical means to ensure that electronic information equipment is not damaged or destroyed in a strong electromagnetic environment. This paper analyzes the current focus and difficulties of electromagnetic protection from the coupling pathway of electromagnetic waves, and then analyzes and summarizes the development status of front door protection technology from three aspects: limiter technology, frequency filtering technology, and energy selection protection technology. Finally, the new electromagnetic protection technology is prospected from two aspects of new shielding materials and protective devices, and the system level electromagnetic protection is summarized from three aspects of integrated front and rear door protection, integrated field and road protection, and multi domain joint protection, which provides support for the electromagnetic protection reinforcement design of electronic information equipment in complex electromagnetic environment.
In this article, the development of strong electromagnetic protection technology is reviewed in response to the strong electromagnetic environmental threats and protection reinforcement requirements faced by electronic information equipment in complex electromagnetic countermeasures environments, and the development prospects of strong electromagnetic system level comprehensive protection are proposed. Strong electromagnetic protection is a technical means to ensure that electronic information equipment is not damaged or destroyed in a strong electromagnetic environment. This paper analyzes the current focus and difficulties of electromagnetic protection from the coupling pathway of electromagnetic waves, and then analyzes and summarizes the development status of front door protection technology from three aspects: limiter technology, frequency filtering technology, and energy selection protection technology. Finally, the new electromagnetic protection technology is prospected from two aspects of new shielding materials and protective devices, and the system level electromagnetic protection is summarized from three aspects of integrated front and rear door protection, integrated field and road protection, and multi domain joint protection, which provides support for the electromagnetic protection reinforcement design of electronic information equipment in complex electromagnetic environment.
2024, 36: 043002.
doi: 10.11884/HPLPB202436.230338
Abstract:
Aiming at the problem that the layout design of air-terminations in multiple lightning rod systems relies too much on engineering experience, based on the principle of least cost, an optimization model for the layout of air-terminations in multiple lightning rod systems is established by taking height and installation position of the air-terminations as the optimization variables. An optimization method for the layout of multiple air-terminations based on the genetic algorithm is proposed. The effectiveness of the proposed optimization method is verified by typical design cases. The results show that the deviation of the height and position of the air-terminations obtained by this method is not more than 0.29 m. All the preset objects to be protected can be completely covered within the protection range of the multiple lightning rod systems, and the minimum distance between the protected objects and the boundary of the protection range is not more than 0.71 m, which can fully meet the needs of engineering applications.
Aiming at the problem that the layout design of air-terminations in multiple lightning rod systems relies too much on engineering experience, based on the principle of least cost, an optimization model for the layout of air-terminations in multiple lightning rod systems is established by taking height and installation position of the air-terminations as the optimization variables. An optimization method for the layout of multiple air-terminations based on the genetic algorithm is proposed. The effectiveness of the proposed optimization method is verified by typical design cases. The results show that the deviation of the height and position of the air-terminations obtained by this method is not more than 0.29 m. All the preset objects to be protected can be completely covered within the protection range of the multiple lightning rod systems, and the minimum distance between the protected objects and the boundary of the protection range is not more than 0.71 m, which can fully meet the needs of engineering applications.
2024, 36: 043003.
doi: 10.11884/HPLPB202436.230261
Abstract:
The shielding effectiveness of a miniature unmanned aerial vehicle (UAV) has a significant impact on its ability to resist strong external electromagnetic interference. An equivalent method based on a large-scale model is employed to overcome the difficulties of measurement performed inside an extremely small space. In this method, the original miniature UAV is enlarged in proportion with scaling factor n and then a large-scale model is obtained. The shielding effectiveness of the large-scale model can be measured by existing mature instruments and test method. Then, the shielding effectiveness of the original model is obtained according to the relationship between the two models. On this basis, two typical miniature UAVs, i.e., a loitering munition and a quad-rotor UAV, are modeled and simulated. It is validated that the shielding effectiveness of the original model at the frequency f is equal to that of the large-scale model at the frequency\begin{document}$ {f_1} = f/n $\end{document} ![]()
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The shielding effectiveness of a miniature unmanned aerial vehicle (UAV) has a significant impact on its ability to resist strong external electromagnetic interference. An equivalent method based on a large-scale model is employed to overcome the difficulties of measurement performed inside an extremely small space. In this method, the original miniature UAV is enlarged in proportion with scaling factor n and then a large-scale model is obtained. The shielding effectiveness of the large-scale model can be measured by existing mature instruments and test method. Then, the shielding effectiveness of the original model is obtained according to the relationship between the two models. On this basis, two typical miniature UAVs, i.e., a loitering munition and a quad-rotor UAV, are modeled and simulated. It is validated that the shielding effectiveness of the original model at the frequency f is equal to that of the large-scale model at the frequency
2024, 36: 043004.
doi: 10.11884/HPLPB202436.230267
Abstract:
As the battlefield environment becomes increasingly complex, especially in high-confrontation environments, it poses a great threat to all types of existing equipment. This article designs a C-band radar receiver protector, which adopts the structural design of inflatable microwave switch tube + waveguide coaxial conversion, innovatively integrates the solid-state limiter chip into the waveguide coaxial convertor, while the limiting chip adopts a cascaded form to increase the power of the microstrip limiter. With a power resistance of over 10 MW and a response time of less than 5 ns, the protector is not only used for receiver protection during radar transmission, but also can cope with external electromagnetic interference and high-power microwave attacks.
As the battlefield environment becomes increasingly complex, especially in high-confrontation environments, it poses a great threat to all types of existing equipment. This article designs a C-band radar receiver protector, which adopts the structural design of inflatable microwave switch tube + waveguide coaxial conversion, innovatively integrates the solid-state limiter chip into the waveguide coaxial convertor, while the limiting chip adopts a cascaded form to increase the power of the microstrip limiter. With a power resistance of over 10 MW and a response time of less than 5 ns, the protector is not only used for receiver protection during radar transmission, but also can cope with external electromagnetic interference and high-power microwave attacks.
2024, 36: 043005.
doi: 10.11884/HPLPB202436.230246
Abstract:
In view of the characteristics of many electromagnetic interference measurement parameters, measurement points and measurement conditions in complex electromagnetic environment and large-scale systems, the traditional sweeping frequency-domain measurement method has practical problems such as high cost and being time-consuming. This paper proposes a multi-channel time-domain rapid measurement and signal calculation method for low-frequency electromagnetic interference, and a multi-channel time-domain rapid measurement system for low-frequency electromagnetic interference is developed. The experimental results show that the proposed measurement, calculation method and the developed measurement system can accurately obtain the low frequency electromagnetic interference characteristics of complex electromagnetic environment and large-scale system, and the measurement speed is fast and the cost is low.
In view of the characteristics of many electromagnetic interference measurement parameters, measurement points and measurement conditions in complex electromagnetic environment and large-scale systems, the traditional sweeping frequency-domain measurement method has practical problems such as high cost and being time-consuming. This paper proposes a multi-channel time-domain rapid measurement and signal calculation method for low-frequency electromagnetic interference, and a multi-channel time-domain rapid measurement system for low-frequency electromagnetic interference is developed. The experimental results show that the proposed measurement, calculation method and the developed measurement system can accurately obtain the low frequency electromagnetic interference characteristics of complex electromagnetic environment and large-scale system, and the measurement speed is fast and the cost is low.
2024, 36: 043006.
doi: 10.11884/HPLPB202436.230327
Abstract:
Strong electromagnetic pulse can be coupled into vehicle engine management system (EMS) through external cables, causing interference and even damage to EMS equipment. Electromagnetic protection components can provide support for vehicle EMS protection design. This article takes vehicle EMS as the research object, comprehensively considers EMS equipment and its external connecting cables, establishes an electromagnetic simulation model of EMS equipment, and conducts simulation research on the port coupling characteristics of cables of different lengths and the induced current on the surface of EMS metal shell. Based on protective circuit simulation, an electromagnetic protection component applied to vehicle EMS equipment was designed. The simulation results show that the protection component can limit the 5 kV electromagnetic pulse to the maximum peak amplitude of 18 V, and the protection efficiency reaches 48 dB. Adding the protection component to the EMS cable interface can effectively improve the reliability in strong electromagnetic environment, which has certain reference significance for the electromagnetic protection design of the vehicle platform control system.
Strong electromagnetic pulse can be coupled into vehicle engine management system (EMS) through external cables, causing interference and even damage to EMS equipment. Electromagnetic protection components can provide support for vehicle EMS protection design. This article takes vehicle EMS as the research object, comprehensively considers EMS equipment and its external connecting cables, establishes an electromagnetic simulation model of EMS equipment, and conducts simulation research on the port coupling characteristics of cables of different lengths and the induced current on the surface of EMS metal shell. Based on protective circuit simulation, an electromagnetic protection component applied to vehicle EMS equipment was designed. The simulation results show that the protection component can limit the 5 kV electromagnetic pulse to the maximum peak amplitude of 18 V, and the protection efficiency reaches 48 dB. Adding the protection component to the EMS cable interface can effectively improve the reliability in strong electromagnetic environment, which has certain reference significance for the electromagnetic protection design of the vehicle platform control system.
2024, 36: 043007.
doi: 10.11884/HPLPB202436.230320
Abstract:
To solve the problem that the aviation Engine Electronic Controller (EEC) is easily disturbed by high-intensity radiation field (HIRF) interference, the plane wave irradiation simulation is performed to simulate the interference effect of HIRF on the EEC through the software CST for the modeling of the EEC. The simulation results show that HIRF can be coupled into the EEC and the electric field strength increases significantly at the resonance frequency. Conducting EEC radiated susceptibility tests at 400 MHz-4 GHz, the test results show that the EEC failure frequency points are 2.40 GHz and 3.84 GHz, the susceptive module is the analog input and output module, The EEC failure frequency is close to the resonance frequency, and the EEC failure is related to the cavity resonance. The wave-absorbing material is mounted inside the EEC and simulation is carried out, and the simulation results show that the wave-absorbing material can effectively suppress the resonance electromagnetic interference, and the results of the study can provide a theoretical basis and reference for the HIRF protection of the EEC.
To solve the problem that the aviation Engine Electronic Controller (EEC) is easily disturbed by high-intensity radiation field (HIRF) interference, the plane wave irradiation simulation is performed to simulate the interference effect of HIRF on the EEC through the software CST for the modeling of the EEC. The simulation results show that HIRF can be coupled into the EEC and the electric field strength increases significantly at the resonance frequency. Conducting EEC radiated susceptibility tests at 400 MHz-4 GHz, the test results show that the EEC failure frequency points are 2.40 GHz and 3.84 GHz, the susceptive module is the analog input and output module, The EEC failure frequency is close to the resonance frequency, and the EEC failure is related to the cavity resonance. The wave-absorbing material is mounted inside the EEC and simulation is carried out, and the simulation results show that the wave-absorbing material can effectively suppress the resonance electromagnetic interference, and the results of the study can provide a theoretical basis and reference for the HIRF protection of the EEC.
2024, 36: 043008.
doi: 10.11884/HPLPB202436.230272
Abstract:
In this paper, a typical backdoor coupled target is constructed, and the echo characteristics of the target are simulated from two dimensions of time domain and frequency domain. It is found that amplitude pits can be observed in the echo frequency domain waveform when the aperture-cavity structure of the target is strongly coupled, and the echo time domain waveform when the aperture-cavity structure is strongly coupled is bimodal, which is obviously different from the non-strongly coupled echo. By changing the size and shape of the backdoor coupled target, the characteristic law of the echo signal is verified by simulation.
In this paper, a typical backdoor coupled target is constructed, and the echo characteristics of the target are simulated from two dimensions of time domain and frequency domain. It is found that amplitude pits can be observed in the echo frequency domain waveform when the aperture-cavity structure of the target is strongly coupled, and the echo time domain waveform when the aperture-cavity structure is strongly coupled is bimodal, which is obviously different from the non-strongly coupled echo. By changing the size and shape of the backdoor coupled target, the characteristic law of the echo signal is verified by simulation.
2024, 36: 043009.
doi: 10.11884/HPLPB202436.230358
Abstract:
To recover the missing frequency information in optical-frequency-comb-based down-converted signal receiving, this paper introduces a frequency recovering method based on frequency-phase-mapping. An optical time delay line is used to generate a certain time delay and it builds a frequency-phase-mapping between signal’s frequency and down-converted component’s phase, which can be acquired by data processing. Thus, the frequency can be calculated through the measurable phase and certain time delay. Then, this paper analyzes parameters such as time delay on frequency recovery, estimates the limit requirements of this method for the uncertainty of phase measurement, and finally gives the setting strategy of key parameters in the specific implementation of this method. The number of signals under test is theoretically unlimited as long as the down-converted components are not aliased. Compared to related works, this method has better performance in multi-signals recovery, because its expense in time consumption and data processing is nearly constant as the number of signals increases.
To recover the missing frequency information in optical-frequency-comb-based down-converted signal receiving, this paper introduces a frequency recovering method based on frequency-phase-mapping. An optical time delay line is used to generate a certain time delay and it builds a frequency-phase-mapping between signal’s frequency and down-converted component’s phase, which can be acquired by data processing. Thus, the frequency can be calculated through the measurable phase and certain time delay. Then, this paper analyzes parameters such as time delay on frequency recovery, estimates the limit requirements of this method for the uncertainty of phase measurement, and finally gives the setting strategy of key parameters in the specific implementation of this method. The number of signals under test is theoretically unlimited as long as the down-converted components are not aliased. Compared to related works, this method has better performance in multi-signals recovery, because its expense in time consumption and data processing is nearly constant as the number of signals increases.
2024, 36: 043010.
doi: 10.11884/HPLPB202436.230321
Abstract:
With the increasing complexity of the electromagnetic environment, the threats posed of electromagnetic weapons to electronic equipment are becoming increasingly serious. As a sensitive integrated electronic device, the optoelectronic system is coupled with high-power electromagnetic pulse energy. This can disrupt the normal operation of the optoelectronic system, especially when it lacks sufficient electromagnetic protection. To clarify the high-power microwave coupling process of typical optoelectronic systems including barrel type, side window type, multi-window type under different irradiation conditions, simulations and analyses are conducted. The characteristics of high-power microwave coupling in optoelectronic systems and their constraints are extracted. The necessity and urgency of protecting reinforcing optoelectronic systems with high-power microwave are verified. For addressing the issue of weak high-power microwave protection ability in optoelectronic systems, the simulation analysis verifies the effectiveness of reinforcing transparent electromagnetic protection windows for high-power microwave. The study focuses in the method of electromagnetic gap protection and reinforcement, which is based on the support step and the conductive side wall. The key parameters of the installation structure for the gap coupling leakage of transparent electromagnetic protection windows are analyzed, and a method of non-electric contact assembly gap high-power microwave protection and reinforcement method is proposed. When the length of the gap protection structure is 6 mm, the average high-power microwave protection efficiency of the 0.2−4 GHz optoelectronic system increases by 4.51 dB. The study provides theoretical guidance and specific solutions for enhancing the high-power microwave protection capability of optoelectronic systems.
With the increasing complexity of the electromagnetic environment, the threats posed of electromagnetic weapons to electronic equipment are becoming increasingly serious. As a sensitive integrated electronic device, the optoelectronic system is coupled with high-power electromagnetic pulse energy. This can disrupt the normal operation of the optoelectronic system, especially when it lacks sufficient electromagnetic protection. To clarify the high-power microwave coupling process of typical optoelectronic systems including barrel type, side window type, multi-window type under different irradiation conditions, simulations and analyses are conducted. The characteristics of high-power microwave coupling in optoelectronic systems and their constraints are extracted. The necessity and urgency of protecting reinforcing optoelectronic systems with high-power microwave are verified. For addressing the issue of weak high-power microwave protection ability in optoelectronic systems, the simulation analysis verifies the effectiveness of reinforcing transparent electromagnetic protection windows for high-power microwave. The study focuses in the method of electromagnetic gap protection and reinforcement, which is based on the support step and the conductive side wall. The key parameters of the installation structure for the gap coupling leakage of transparent electromagnetic protection windows are analyzed, and a method of non-electric contact assembly gap high-power microwave protection and reinforcement method is proposed. When the length of the gap protection structure is 6 mm, the average high-power microwave protection efficiency of the 0.2−4 GHz optoelectronic system increases by 4.51 dB. The study provides theoretical guidance and specific solutions for enhancing the high-power microwave protection capability of optoelectronic systems.
2024, 36: 043011.
doi: 10.11884/HPLPB202436.230249
Abstract:
To meet the requirements of MV/m intensity pulse electric field measurement, a single optical path type small volume broadband pulse electric field measurement system based on integrated optics is designed and developed. Based on electro-optical effect and electro-optic modulation principle, the amplitude and frequency response transfer function of the measuring system is established, the reception characteristics of the integrated optical probe are analyzed, the relationship between its sensitivity and bandwidth with the length of the waveguide is derived. The pure optical non-metallic single-optical waveguide structure is designed, and a method of adjusting the measurement sensitivity using crystal width is proposed, which raised the designed half-wave electric field more than 3 times. The passive probe size is less than 20 mm×10 mm×5 mm, the theoretical bandwidth is more than 4 GHz, and the maximum measurement range is more than 1.2 MV/m. The developed measurement system has applications in the fields of high-altitude electromagnetic pulse (HEMP), lightning (LEMP) and pulsed power technology.
To meet the requirements of MV/m intensity pulse electric field measurement, a single optical path type small volume broadband pulse electric field measurement system based on integrated optics is designed and developed. Based on electro-optical effect and electro-optic modulation principle, the amplitude and frequency response transfer function of the measuring system is established, the reception characteristics of the integrated optical probe are analyzed, the relationship between its sensitivity and bandwidth with the length of the waveguide is derived. The pure optical non-metallic single-optical waveguide structure is designed, and a method of adjusting the measurement sensitivity using crystal width is proposed, which raised the designed half-wave electric field more than 3 times. The passive probe size is less than 20 mm×10 mm×5 mm, the theoretical bandwidth is more than 4 GHz, and the maximum measurement range is more than 1.2 MV/m. The developed measurement system has applications in the fields of high-altitude electromagnetic pulse (HEMP), lightning (LEMP) and pulsed power technology.
2024, 36: 043012.
doi: 10.11884/HPLPB202436.230367
Abstract:
Aiming at the problem of high reflection and poor low-frequency radiation performance of TEM horn antenna, the simulation optimization design is carried out. The low frequency compensation methods of end loading resistance and back loading resistance are analyzed by using time domain analysis method, and the structural parameters such as the size of the TEM horn antenna and the apex angle of the plate are optimized. The peak field strength and pulse width of the radiation field are improved by using the end crimping structure. According to the simulation results, TEM horn antenna with length of 2.5 m, the included angle of the plates of 45° and antenna plate apex angle of 45° is developed. The simulation results are verified by the measurement of the new antenna. The results show that the loading resistance can effectively reduce the reflection, and the peak field strength and pulse width of the back loading resistance are higher than that of the end loading resistance, and the effect of 4 resistors in parallel loading is better. The radiation performance of the antenna can be improved by appropriately increasing the antenna length, the apex angle of the plate and the included angle between two plates. The research results provide a reference for the application of TEM horn antenna in the radiation nuclear electromagnetic pulse test system.
Aiming at the problem of high reflection and poor low-frequency radiation performance of TEM horn antenna, the simulation optimization design is carried out. The low frequency compensation methods of end loading resistance and back loading resistance are analyzed by using time domain analysis method, and the structural parameters such as the size of the TEM horn antenna and the apex angle of the plate are optimized. The peak field strength and pulse width of the radiation field are improved by using the end crimping structure. According to the simulation results, TEM horn antenna with length of 2.5 m, the included angle of the plates of 45° and antenna plate apex angle of 45° is developed. The simulation results are verified by the measurement of the new antenna. The results show that the loading resistance can effectively reduce the reflection, and the peak field strength and pulse width of the back loading resistance are higher than that of the end loading resistance, and the effect of 4 resistors in parallel loading is better. The radiation performance of the antenna can be improved by appropriately increasing the antenna length, the apex angle of the plate and the included angle between two plates. The research results provide a reference for the application of TEM horn antenna in the radiation nuclear electromagnetic pulse test system.
2024, 36: 043013.
doi: 10.11884/HPLPB202436.230237
Abstract:
PIN diodes are critical devices for preventing damage from strong electromagnetic signals. Accurately predicting the temperature rise curve of the PIN diode has important guiding significance for selecting protective devices. Machine learning-based methods can effectively predict the characteristics of devices. However, the temperature rise characteristic curve of the PIN diode contains strong nonlinearity and small fluctuations, and traditional machine learning methods cannot predict accurately. To accurately predict the temperature rise characteristic curve of PIN diodes, this paper proposes a prediction method that combines variational mode decomposition (VMD) and autoencoder to decompose the temperature rise characteristics into sub-signals, which include high-frequency fluctuations, intermediate quantities, and low-frequency trend quantities. Then an autoencoder is used to predict each component. Finally, the predicted values of the components are added together, so as to accurately predict the temperature rise characteristic curve of the PIN diode. By comparing with various machine learning methods, it is verified that combining VMD decomposition can effectively improve prediction accuracy, and the advantage of autoencoder in fitting characteristic curves is also verified.
PIN diodes are critical devices for preventing damage from strong electromagnetic signals. Accurately predicting the temperature rise curve of the PIN diode has important guiding significance for selecting protective devices. Machine learning-based methods can effectively predict the characteristics of devices. However, the temperature rise characteristic curve of the PIN diode contains strong nonlinearity and small fluctuations, and traditional machine learning methods cannot predict accurately. To accurately predict the temperature rise characteristic curve of PIN diodes, this paper proposes a prediction method that combines variational mode decomposition (VMD) and autoencoder to decompose the temperature rise characteristics into sub-signals, which include high-frequency fluctuations, intermediate quantities, and low-frequency trend quantities. Then an autoencoder is used to predict each component. Finally, the predicted values of the components are added together, so as to accurately predict the temperature rise characteristic curve of the PIN diode. By comparing with various machine learning methods, it is verified that combining VMD decomposition can effectively improve prediction accuracy, and the advantage of autoencoder in fitting characteristic curves is also verified.
2024, 36: 043014.
doi: 10.11884/HPLPB202436.230345
Abstract:
Conducting material shielding effectiveness testing in complex electromagnetic environments of reverberation chambers has become a key technology for accurately evaluating the electromagnetic protection ability of materials. To study the performance of the boundary deformation mutual coupling reverberation chamber shielding effectiveness testing system, experiments were conducted to verify the dynamic range, electric field distribution characteristics, and uncertainty. The results show that: in actual testing, a test result less than 60 dB is considered a reliable test value; the standard deviation of the electric field in both the transmitting and receiving reverberation chambers is less than 3 dB within the testing frequency range, fully meeting the uniformity requirements of the reverberation chamber; especially, the standard deviation of the spatial electric field in the receiving reverberation chamber is all less than 2 dB, and the uniformity is excellent; the expanded uncertainty of the testing system is 5.90 dB, which can be used as a material shielding effectiveness testing platform.
Conducting material shielding effectiveness testing in complex electromagnetic environments of reverberation chambers has become a key technology for accurately evaluating the electromagnetic protection ability of materials. To study the performance of the boundary deformation mutual coupling reverberation chamber shielding effectiveness testing system, experiments were conducted to verify the dynamic range, electric field distribution characteristics, and uncertainty. The results show that: in actual testing, a test result less than 60 dB is considered a reliable test value; the standard deviation of the electric field in both the transmitting and receiving reverberation chambers is less than 3 dB within the testing frequency range, fully meeting the uniformity requirements of the reverberation chamber; especially, the standard deviation of the spatial electric field in the receiving reverberation chamber is all less than 2 dB, and the uniformity is excellent; the expanded uncertainty of the testing system is 5.90 dB, which can be used as a material shielding effectiveness testing platform.
2024, 36: 043015.
doi: 10.11884/HPLPB202436.230384
Abstract:
An analysis of lightning standards is made for military and civil aircraft platforms, subsystems, and equipment both domestically and internationally, detailing the applicable areas, waveform requirements, and testing configurations for each test item for both direct and indirect lightning effects. Based on the existing domestic lightning design verification standards and shortcomings in testing, suggestions are proposed to improve the compatibility between testing equipment and testing verification technology, expand the field of military standard testing, and unify the requirements of the same service and platform. Through presenting the lightning design verification standards and testing for military airborne platforms, equipment, and subsystems, the analysis provides design index references for relevant product designers and testers to clarify the design requirements and verification requirements for lightning protection, thus to achieve targeted goals and improve design cost-effectiveness.
An analysis of lightning standards is made for military and civil aircraft platforms, subsystems, and equipment both domestically and internationally, detailing the applicable areas, waveform requirements, and testing configurations for each test item for both direct and indirect lightning effects. Based on the existing domestic lightning design verification standards and shortcomings in testing, suggestions are proposed to improve the compatibility between testing equipment and testing verification technology, expand the field of military standard testing, and unify the requirements of the same service and platform. Through presenting the lightning design verification standards and testing for military airborne platforms, equipment, and subsystems, the analysis provides design index references for relevant product designers and testers to clarify the design requirements and verification requirements for lightning protection, thus to achieve targeted goals and improve design cost-effectiveness.
2024, 36: 043016.
doi: 10.11884/HPLPB202436.230119
Abstract:
Aiming at the problems of low recognition accuracy and poor timeliness of existing radar emitter signal recognition methods under the condition of low SNR, this paper proposes a radar emitter signal recognition method based on compressed residual network. Using Choi-Williams distribution for reference, the time-domain signal is converted into a two-dimensional time-frequency image, which improves the effectiveness of signal essential feature extraction. According to the characteristics of the application scenario, it selects the “compression” range of convolutional neural networks (CNN), and builds a compression residual network to automatically extract image features and identify. The simulation results show that compared with other advanced models, the proposed method can reduce the running time of signal recognition by about 88%, and the average recognition rate of 14 radar emitter signals is at least 5% higher when the signal-to-noise ratio is −14 dB. This paper provides an efficient intelligent recognition method of radar emitter signal, which has potential engineering application prospects.
Aiming at the problems of low recognition accuracy and poor timeliness of existing radar emitter signal recognition methods under the condition of low SNR, this paper proposes a radar emitter signal recognition method based on compressed residual network. Using Choi-Williams distribution for reference, the time-domain signal is converted into a two-dimensional time-frequency image, which improves the effectiveness of signal essential feature extraction. According to the characteristics of the application scenario, it selects the “compression” range of convolutional neural networks (CNN), and builds a compression residual network to automatically extract image features and identify. The simulation results show that compared with other advanced models, the proposed method can reduce the running time of signal recognition by about 88%, and the average recognition rate of 14 radar emitter signals is at least 5% higher when the signal-to-noise ratio is −14 dB. This paper provides an efficient intelligent recognition method of radar emitter signal, which has potential engineering application prospects.
2024, 36: 043017.
doi: 10.11884/HPLPB202436.230383
Abstract:
Due to extensive electromagnetic radiation or interference, the rapid detection and location of electromagnetic interference sources in a large space has become a hot issue to be studied urgently. Electromagnetic imaging technology can visually display the location of radiation sources and solve the problem of rapid detection and localization of electromagnetic interference sources. However, the existing reflector electromagnetic imaging system is bulky and cannot meet the requirements of airborne, vehicle-mounted, UAV and other application platforms. To address this issue, this paper studies the structure and imaging characteristics of Luneburg lens, designs a large field-of-view Luneburg lens electromagnetic imaging (EMI) system, and realizes rapid identification and location of EMI with the advantages of large field of view, wide bandwidth and high resolution. In this paper, the parameters of the 300 mm Luneburg lens with spherical core are calculated, the E-field intensity distribution of the 4～18GHz is simulated, and the space invariant imaging characteristics of Luneburg lens and its super-resolution algorithm are verified. The paper finally compares the volume, field of view, source number and resolution of the parabolic reflector electromagnetic imaging system and the Luneburg lens electromagnetic imaging system. The results demonstrate the superiority of the system proposed in this paper, achieving a large field of view with azimuth and elevation angles of 40° at the same resolution.
Due to extensive electromagnetic radiation or interference, the rapid detection and location of electromagnetic interference sources in a large space has become a hot issue to be studied urgently. Electromagnetic imaging technology can visually display the location of radiation sources and solve the problem of rapid detection and localization of electromagnetic interference sources. However, the existing reflector electromagnetic imaging system is bulky and cannot meet the requirements of airborne, vehicle-mounted, UAV and other application platforms. To address this issue, this paper studies the structure and imaging characteristics of Luneburg lens, designs a large field-of-view Luneburg lens electromagnetic imaging (EMI) system, and realizes rapid identification and location of EMI with the advantages of large field of view, wide bandwidth and high resolution. In this paper, the parameters of the 300 mm Luneburg lens with spherical core are calculated, the E-field intensity distribution of the 4～18GHz is simulated, and the space invariant imaging characteristics of Luneburg lens and its super-resolution algorithm are verified. The paper finally compares the volume, field of view, source number and resolution of the parabolic reflector electromagnetic imaging system and the Luneburg lens electromagnetic imaging system. The results demonstrate the superiority of the system proposed in this paper, achieving a large field of view with azimuth and elevation angles of 40° at the same resolution.
2024, 36: 043018.
doi: 10.11884/HPLPB202436.230186
Abstract:
With the development of networks such as mobile communications, Internet of Things (IoT), V2X (meaning Vehicle to everything, including Vehicle to Vehicle and Vehicle to Infrastructure), and Industrial Internet of Things (IIoT), the electromagnetic environment is becoming increasingly complex, illegal electronic devices are also increasing day by day, and there are severe coupling and intermodulation of various signals, which bring difficulties to the identification of leaked signal types. This paper proposes a leakage signal classification and recognition method based on fused features. Comprehensively utilizing high-dimensional feature extraction methods and graphical dimensionality reduction characterization methods, and combining with deep learning models such as residual networks and feature fusion analysis methods, the method can distinguish more comprehensively multiple types of electromagnetic leakage signals. The features method has with high robustness against noise and good interpretability, and can support the intelligent detection engineering application of radiation sources based on electromagnetic signal type recognition.
With the development of networks such as mobile communications, Internet of Things (IoT), V2X (meaning Vehicle to everything, including Vehicle to Vehicle and Vehicle to Infrastructure), and Industrial Internet of Things (IIoT), the electromagnetic environment is becoming increasingly complex, illegal electronic devices are also increasing day by day, and there are severe coupling and intermodulation of various signals, which bring difficulties to the identification of leaked signal types. This paper proposes a leakage signal classification and recognition method based on fused features. Comprehensively utilizing high-dimensional feature extraction methods and graphical dimensionality reduction characterization methods, and combining with deep learning models such as residual networks and feature fusion analysis methods, the method can distinguish more comprehensively multiple types of electromagnetic leakage signals. The features method has with high robustness against noise and good interpretability, and can support the intelligent detection engineering application of radiation sources based on electromagnetic signal type recognition.
2024, 36: 043019.
doi: 10.11884/HPLPB202436.230380
Abstract:
A Grad-CAM based visualizing method for important regions is proposed for the interpretability of RF fingerprint extraction and deep learning models of time-domain pulse signal samples. The impact of important regions on RF fingerprint recognition results is analyzed through multiple mask tests of important regions. Based on signal samples of 10 emitters, the test results of two ResNet models with different layers are compared. It is found that the proposed method can distinguish different types of signals and present individual differences. Analysis shows that this method can detect important regional localization differences when different emitters send the same signal, and can visually reflect the spatial distance of RF fingerprint characteristics, as well as the differences in feature representation and fingerprint localization accuracy of different models; At the same time, it is found that masks for important areas are more prone to false predictions, which proves the existence of RF fingerprints related to time-frequency characteristics in specific signals, and can assist in visualizing key points that affect the recognition of RF fingerprint samples.
A Grad-CAM based visualizing method for important regions is proposed for the interpretability of RF fingerprint extraction and deep learning models of time-domain pulse signal samples. The impact of important regions on RF fingerprint recognition results is analyzed through multiple mask tests of important regions. Based on signal samples of 10 emitters, the test results of two ResNet models with different layers are compared. It is found that the proposed method can distinguish different types of signals and present individual differences. Analysis shows that this method can detect important regional localization differences when different emitters send the same signal, and can visually reflect the spatial distance of RF fingerprint characteristics, as well as the differences in feature representation and fingerprint localization accuracy of different models; At the same time, it is found that masks for important areas are more prone to false predictions, which proves the existence of RF fingerprints related to time-frequency characteristics in specific signals, and can assist in visualizing key points that affect the recognition of RF fingerprint samples.
2024, 36: 043020.
doi: 10.11884/HPLPB202436.230302
Abstract:
Optical down-conversion technology can simultaneously down-convert all electromagnetic signals within a wide frequency band to the low-frequency range for reception, and is a new type of fast reception technology for broadband electromagnetic environments. However, the obtained optical down-conversion signal contains multiple signals with unknown number of sources and different bandwidths. Existing signal separation methods need to know the number of source signals and cannot simultaneously separate narrowband and broadband signals. To achieve automatic separation of optical down-conversion signals, a method for optical down-conversion signal separation based on VMD adaptive mode recombination is proposed. By using spectral segmentation factors and spectral envelope detection, the VMD over decomposition modes of optical down-conversion signals are automatically recombined and signal recombination modes are extracted, achieving the separation of optical down-conversion signals. For optical down-conversion signals containing ordinary pulse signals, WCDMA signals, and linear frequency modulation pulse signals, this method can automatically separate the three types of signals, and the similarity coefficients with the original signal are all higher than 0.97. The experimental results show that the method proposed in this paper does not need to know the number of source signals when separating optical down-conversion signals, and can simultaneously separate multiple source signals with different bandwidths.
Optical down-conversion technology can simultaneously down-convert all electromagnetic signals within a wide frequency band to the low-frequency range for reception, and is a new type of fast reception technology for broadband electromagnetic environments. However, the obtained optical down-conversion signal contains multiple signals with unknown number of sources and different bandwidths. Existing signal separation methods need to know the number of source signals and cannot simultaneously separate narrowband and broadband signals. To achieve automatic separation of optical down-conversion signals, a method for optical down-conversion signal separation based on VMD adaptive mode recombination is proposed. By using spectral segmentation factors and spectral envelope detection, the VMD over decomposition modes of optical down-conversion signals are automatically recombined and signal recombination modes are extracted, achieving the separation of optical down-conversion signals. For optical down-conversion signals containing ordinary pulse signals, WCDMA signals, and linear frequency modulation pulse signals, this method can automatically separate the three types of signals, and the similarity coefficients with the original signal are all higher than 0.97. The experimental results show that the method proposed in this paper does not need to know the number of source signals when separating optical down-conversion signals, and can simultaneously separate multiple source signals with different bandwidths.
2024, 36: 043021.
doi: 10.11884/HPLPB202436.230303
Abstract:
The cognitive bias is an objective existence of cognitive electronic warfare. Based on the method of dynamic gaming, this paper investigates the approach to modeling radar countermeasure with the cognitive bias caused by the incomplete information and the measuring error in the cognitive radar countermeasure. It adopts the anti-jamming improvement factors of radar and the jamming payoff factors of jammer to calculate the utilities of both adversarial parties. Thereafter, the dynamic radar countermeasure model is setup with the perfect Bayesian equilibrium. The influence of cognitive bias on gaming result is further analyzed. The results of simulation test validate the effectiveness of the proposed method.
The cognitive bias is an objective existence of cognitive electronic warfare. Based on the method of dynamic gaming, this paper investigates the approach to modeling radar countermeasure with the cognitive bias caused by the incomplete information and the measuring error in the cognitive radar countermeasure. It adopts the anti-jamming improvement factors of radar and the jamming payoff factors of jammer to calculate the utilities of both adversarial parties. Thereafter, the dynamic radar countermeasure model is setup with the perfect Bayesian equilibrium. The influence of cognitive bias on gaming result is further analyzed. The results of simulation test validate the effectiveness of the proposed method.
2024, 36: 043022.
doi: 10.11884/HPLPB202436.230236
Abstract:
A field-circuit co-simulation model of a two-stage PIN limiter was built to explore the influence of high-power microwave signal parameters on the temperature distribution of the limiter. The simulation results indicate that the increase in microwave pulse amplitude or frequency can expand the PIN diode's high-temperature region inside the two-stage PIN limiter towards the P-region. Compared with the frequency, the amplitude of the microwave pulse has a more significant impact on the temperature distribution of the PIN limiter.
A field-circuit co-simulation model of a two-stage PIN limiter was built to explore the influence of high-power microwave signal parameters on the temperature distribution of the limiter. The simulation results indicate that the increase in microwave pulse amplitude or frequency can expand the PIN diode's high-temperature region inside the two-stage PIN limiter towards the P-region. Compared with the frequency, the amplitude of the microwave pulse has a more significant impact on the temperature distribution of the PIN limiter.
2024, 36: 043023.
doi: 10.11884/HPLPB202436.230276
Abstract:
The high-speed switching of power devices such as MOSFETs and IGBT switches in power conversion systems will generate high amplitude and broadband electromagnetic interference (EMI), which is the most common and unavoidable EMI for electric vehicles. At the same time, interconnecting cables are the carrier of signals and energy transmitted by electrical devices, the antenna effect of cables is the main pathway for EMI radiation propagation, and is one of the main sources of system electromagnetic compatibility (EMC) problems. To analyze the electromagnetic coupling between the high-voltage power conversion system and the low-voltage control system, this paper takes the pulse width modulation (PWM ) wave generated by the IGBT as the EMI source, and uses the actual cable as the analysis object to construct a high and low voltage harness crosstalk model. The simulation analysis analyzes the near-end crosstalk voltage of multiple types of low voltage cable under different conditions of cable spacing and ground distance, obtains the anti-interference performance of low-voltage cables, thus provides guidance for the wiring of the system cable harness.
The high-speed switching of power devices such as MOSFETs and IGBT switches in power conversion systems will generate high amplitude and broadband electromagnetic interference (EMI), which is the most common and unavoidable EMI for electric vehicles. At the same time, interconnecting cables are the carrier of signals and energy transmitted by electrical devices, the antenna effect of cables is the main pathway for EMI radiation propagation, and is one of the main sources of system electromagnetic compatibility (EMC) problems. To analyze the electromagnetic coupling between the high-voltage power conversion system and the low-voltage control system, this paper takes the pulse width modulation (PWM ) wave generated by the IGBT as the EMI source, and uses the actual cable as the analysis object to construct a high and low voltage harness crosstalk model. The simulation analysis analyzes the near-end crosstalk voltage of multiple types of low voltage cable under different conditions of cable spacing and ground distance, obtains the anti-interference performance of low-voltage cables, thus provides guidance for the wiring of the system cable harness.
2024, 36: 043024.
doi: 10.11884/HPLPB202436.230273
Abstract:
Using 3D MC code and PIC code, model of electromagnetic pulse (SGEMP) generated in the cavity system radiated by SG-facility is calculated. The simulated results show that the intensity of electric field could be 2.2 MV/m and magnetic field be 0.8×10−3 T under irradiation of the bremsstrahlung X-ray point source with full width at half maximum 2.9 ns, average energy 10.3 keV produced by SG-facility irradiating the end of cylinder cavity. The electric field is mainly axial and the magnetic field is primarily azimuthal. Both electric field and magnetic field are concentrated near the emitting surface, with the pulsed DC field being predominant and the amplitude of the AC radiation field being relatively smaller, at the level of kV/m. The effect of fluence on SGEMP is also studied, showing that higher fluence leads to faster axial variation of the electric field and larger proportion of the AC radiation field.
Using 3D MC code and PIC code, model of electromagnetic pulse (SGEMP) generated in the cavity system radiated by SG-facility is calculated. The simulated results show that the intensity of electric field could be 2.2 MV/m and magnetic field be 0.8×10−3 T under irradiation of the bremsstrahlung X-ray point source with full width at half maximum 2.9 ns, average energy 10.3 keV produced by SG-facility irradiating the end of cylinder cavity. The electric field is mainly axial and the magnetic field is primarily azimuthal. Both electric field and magnetic field are concentrated near the emitting surface, with the pulsed DC field being predominant and the amplitude of the AC radiation field being relatively smaller, at the level of kV/m. The effect of fluence on SGEMP is also studied, showing that higher fluence leads to faster axial variation of the electric field and larger proportion of the AC radiation field.
2024, 36: 043025.
doi: 10.11884/HPLPB202436.230299
Abstract:
Based on the object-oriented C++ language, a 3D cylindrical coordinate conformal grid generation program is developed. The conformal grid generation of beam-field interaction(BFI) device discretizing is performed, providing integral line and face elements for Particle-in-Cell simulation algorithm. By defining the basic elements of the three-dimensional cylindrical coordinate grid system, including grid step-size, grid index, guardian grid layer and bounding box, the spatial information of the model can be converted into the information of the cylindrical coordinate grid information necessary for numerical calculation. The grid cells on-axis should be specially treated so as to maintain the consistency of the particle-in-cell algorithm between the axial grid and the non-axial grid. The discrete boundary points on the model subsurface and on the model edge were attained by ray-tracing algorithm. Meanwhile, the vertices of the model were obtained by topological relations. Topological information and cylindrical coordinate grid information of the two types of boundary points and model vertices were recorded, then the basic grid elements were coupled with the boundary point information, finally the model was reconstructed in the discrete grid system. Taking the relativistic magnetron for example, using the conformal grid generation technique proposed in the paper to discretize the model, the transparent cathode, anode, and resonant cavity structures of the magnetron can be identified.
Based on the object-oriented C++ language, a 3D cylindrical coordinate conformal grid generation program is developed. The conformal grid generation of beam-field interaction(BFI) device discretizing is performed, providing integral line and face elements for Particle-in-Cell simulation algorithm. By defining the basic elements of the three-dimensional cylindrical coordinate grid system, including grid step-size, grid index, guardian grid layer and bounding box, the spatial information of the model can be converted into the information of the cylindrical coordinate grid information necessary for numerical calculation. The grid cells on-axis should be specially treated so as to maintain the consistency of the particle-in-cell algorithm between the axial grid and the non-axial grid. The discrete boundary points on the model subsurface and on the model edge were attained by ray-tracing algorithm. Meanwhile, the vertices of the model were obtained by topological relations. Topological information and cylindrical coordinate grid information of the two types of boundary points and model vertices were recorded, then the basic grid elements were coupled with the boundary point information, finally the model was reconstructed in the discrete grid system. Taking the relativistic magnetron for example, using the conformal grid generation technique proposed in the paper to discretize the model, the transparent cathode, anode, and resonant cavity structures of the magnetron can be identified.
2024, 36: 043026.
doi: 10.11884/HPLPB202436.230370
Abstract:
To analyze the electromagnetic environmental effects of composite shell platforms in strong electromagnetic environments such as nuclear electromagnetic pulses, we have obtained an equivalent calculation method of the finite-difference time-domain method in dealing with weakly conducting thin-layer dielectric materials based on the integral form of the Maxwell-Amper theorem. The thin layer model can be appropriately thickened while proportionally reducing its conductivity when the equivalent wavelength of the medium is larger than the model thickness. The electromagnetic coupling characteristics of the model before and after parameter equivalence are essentially the same. This method can reduce the computational effort by increasing the grid step size. In addition, this method does not require changing the time step format of the traditional finite-difference time-domain method and does not affect the stability of the calculation. Numerical experiments, such as the examples using infinitely large thin plates, thin spherical layers, and electromagnetic coupling of unmanned aerial vehicles with thin shells, have shown that it has good applicability to the electromagnetic coupling simulation of thin-shell platforms containing weakly conducting materials with millimeter thickness in nuclear electromagnetic pulse environments.
To analyze the electromagnetic environmental effects of composite shell platforms in strong electromagnetic environments such as nuclear electromagnetic pulses, we have obtained an equivalent calculation method of the finite-difference time-domain method in dealing with weakly conducting thin-layer dielectric materials based on the integral form of the Maxwell-Amper theorem. The thin layer model can be appropriately thickened while proportionally reducing its conductivity when the equivalent wavelength of the medium is larger than the model thickness. The electromagnetic coupling characteristics of the model before and after parameter equivalence are essentially the same. This method can reduce the computational effort by increasing the grid step size. In addition, this method does not require changing the time step format of the traditional finite-difference time-domain method and does not affect the stability of the calculation. Numerical experiments, such as the examples using infinitely large thin plates, thin spherical layers, and electromagnetic coupling of unmanned aerial vehicles with thin shells, have shown that it has good applicability to the electromagnetic coupling simulation of thin-shell platforms containing weakly conducting materials with millimeter thickness in nuclear electromagnetic pulse environments.
2024, 36: 043027.
doi: 10.11884/HPLPB202436.230245
Abstract:
Near-ground nuclear explosion fallout consists of radioactive particles of different particle size, and its motion has a large spatial and temporal scales. For the problem how to simulate the atmospheric γ ionizing radiation environment of the near-ground explosion fallout, in this paper, firstly, the mechanism analysis of atmospheric gamma radiation is carried out, the no-wind conditions are set up, and the theoretical model of fallout gamma radiation is established. Secondly, the corresponding numerical difference and integration algorithms are introduced and proposed. Finally, the simulation example of the radioactivity and radiative dose rate in the atmosphere of the 1000 kt Nevada near-ground explosion is given, a certain summary of the temporal and spatial evolution patterns of the radiation environment and the comparison of the results are accomplished, and the comparison reveals that the present model is able to calculate the theoretical maximum of the atmospheric radiation dose rate while ensuring the consistency of the activity results.
Near-ground nuclear explosion fallout consists of radioactive particles of different particle size, and its motion has a large spatial and temporal scales. For the problem how to simulate the atmospheric γ ionizing radiation environment of the near-ground explosion fallout, in this paper, firstly, the mechanism analysis of atmospheric gamma radiation is carried out, the no-wind conditions are set up, and the theoretical model of fallout gamma radiation is established. Secondly, the corresponding numerical difference and integration algorithms are introduced and proposed. Finally, the simulation example of the radioactivity and radiative dose rate in the atmosphere of the 1000 kt Nevada near-ground explosion is given, a certain summary of the temporal and spatial evolution patterns of the radiation environment and the comparison of the results are accomplished, and the comparison reveals that the present model is able to calculate the theoretical maximum of the atmospheric radiation dose rate while ensuring the consistency of the activity results.
2024, 36: 043028.
doi: 10.11884/HPLPB202436.230372
Abstract:
This study aims to address the issue of the rapidly increasing quantity of space debris by investigating the feasibility of active debris removal by strong electromagnetic irradiation. A multi-layer insulation structure was employed as a typical model for hazardous space debris, and feasibility validation experiments were conducted in a complex physical environment incorporating multiple environmental factors under strong electromagnetic irradiation in the S-band and vacuum conditions. The experimental results demonstrate that, in a vacuum environment at the order of 10−3 Pa, strong electromagnetic pulses interact with the multi-layer insulation structure, triggering discharge phenomena and generating plasma, accompanied by changes in macroscopic dynamic characteristics. Through observation and analysis, possible physical processes were explored, including strong field breakdown leading to point discharge in materials, surface flashover causing mesh discharge and coating to damage, particle absorption of microwave energy resulting in material deformation or expansion, as well as plasma ablation leading to material destruction. This study provides important technical support for the active removal of hazardous space debris using strong electromagnetic irradiation.
This study aims to address the issue of the rapidly increasing quantity of space debris by investigating the feasibility of active debris removal by strong electromagnetic irradiation. A multi-layer insulation structure was employed as a typical model for hazardous space debris, and feasibility validation experiments were conducted in a complex physical environment incorporating multiple environmental factors under strong electromagnetic irradiation in the S-band and vacuum conditions. The experimental results demonstrate that, in a vacuum environment at the order of 10−3 Pa, strong electromagnetic pulses interact with the multi-layer insulation structure, triggering discharge phenomena and generating plasma, accompanied by changes in macroscopic dynamic characteristics. Through observation and analysis, possible physical processes were explored, including strong field breakdown leading to point discharge in materials, surface flashover causing mesh discharge and coating to damage, particle absorption of microwave energy resulting in material deformation or expansion, as well as plasma ablation leading to material destruction. This study provides important technical support for the active removal of hazardous space debris using strong electromagnetic irradiation.
2024, 36: 043029.
doi: 10.11884/HPLPB202436.230373
Abstract:
Monte Carlo method was used to study the shielding characteristics of ship compartments in early nuclear radiation scenarios. Using early gamma radiation as a radiation source, the mass attenuation coefficients of three commonly used materials, HSLA-80, 5456Al, and FDCL-3B, for ship bodies were measured. A simulated cabin model was established based on the geometric structure of the ship, and Gaussian broadening method was used to fit the detector's energy spectrum. The absorption energy spectrum of the NaI detector inside the cabin under gamma radiation was obtained, and compared with experimental results in the literature, thus verified the reliability of the calculation model and results. On this basis, using the gamma protection coefficient as the evaluation index, considering two scenarios of radioactive isotopes (single energy point sources) and early gamma radiation (surface sources with energy distribution), the spatial distribution characteristics of gamma radiation shielding in simulated cabins were calculated and analyzed. The results show that the protection coefficient of the simulated cabins for different radioactive isotopes was different, with a maximum difference of 6.74 times (Cd-109 and Cs-137); The protection coefficient varies in different positions of the cabin. The gamma radiation dose at the front end of the cabin is relatively high, while the gamma radiation dose at the corners is relatively low, with a difference of 35%; The protection coefficient is related to the incident angle of gamma irradiation. Compared with normal incidence, the simulated cabin has a higher gamma radiation protection coefficient for oblique 45° incidence, which can be improved by 43%.
Monte Carlo method was used to study the shielding characteristics of ship compartments in early nuclear radiation scenarios. Using early gamma radiation as a radiation source, the mass attenuation coefficients of three commonly used materials, HSLA-80, 5456Al, and FDCL-3B, for ship bodies were measured. A simulated cabin model was established based on the geometric structure of the ship, and Gaussian broadening method was used to fit the detector's energy spectrum. The absorption energy spectrum of the NaI detector inside the cabin under gamma radiation was obtained, and compared with experimental results in the literature, thus verified the reliability of the calculation model and results. On this basis, using the gamma protection coefficient as the evaluation index, considering two scenarios of radioactive isotopes (single energy point sources) and early gamma radiation (surface sources with energy distribution), the spatial distribution characteristics of gamma radiation shielding in simulated cabins were calculated and analyzed. The results show that the protection coefficient of the simulated cabins for different radioactive isotopes was different, with a maximum difference of 6.74 times (Cd-109 and Cs-137); The protection coefficient varies in different positions of the cabin. The gamma radiation dose at the front end of the cabin is relatively high, while the gamma radiation dose at the corners is relatively low, with a difference of 35%; The protection coefficient is related to the incident angle of gamma irradiation. Compared with normal incidence, the simulated cabin has a higher gamma radiation protection coefficient for oblique 45° incidence, which can be improved by 43%.
2024, 36: 043030.
doi: 10.11884/HPLPB202436.230275
Abstract:
As a kind of high power microwave generator, the plasma relativistic microwave generators (PRMGs) have the virtues of wideband high power microwave output and fine frequency tunability. Thus PRMG is very useful for a wide variety of applications. The beam-wave interaction region in the PRMG is generally a cylindrical metal waveguide with preformed annular plasma. The dispersion characteristics of the operating slow plasma wave TM01 mode (called as P-TM01 mode below) in the interaction region are critical to the output properties. Therefore, the dispersion characteristics and field distributions of the P-TM01 mode in a cylindrical waveguide loaded with annular plasma beam is studied numerically using the all electromagnetic PIC (Particle-in-Cell) code. Variation trends of the dispersion characteristics and the field distributions of the P-TM01 mode with the density np, radial thickness Δrp and radial position rp of the plasma beam, the intensity of the guiding magnetic field Bz and the radius of the waveguide rw are obtained. Simulation results show that: (1) Both np and Δrp affect the dispersion characteristics markedly and the frequency of the P-TM01 mode increases with the increasing of either np or Δrp at the same axial wave number kz. (2) Variations of rp, rw or Bz have very slight influence on the dispersion in the interested range. It is indicated that one can choose relatively larger dimensions of the waveguide for larger power capacity and lower guiding magnetic field for compactness if necessary. (3) The basic features of the field distributions of the P-TM01 mode will not change with the variations of the above mentioned physical parameters. But with the increasing of axial mode number and kz, the electromagnetic energy will be trapped inside the plasma beam gradually and no effective beam-wave interaction will happen in the end. Therefore, it is suggested to choose the operating point with relatively small kz for the efficient operation of PRMG.
As a kind of high power microwave generator, the plasma relativistic microwave generators (PRMGs) have the virtues of wideband high power microwave output and fine frequency tunability. Thus PRMG is very useful for a wide variety of applications. The beam-wave interaction region in the PRMG is generally a cylindrical metal waveguide with preformed annular plasma. The dispersion characteristics of the operating slow plasma wave TM01 mode (called as P-TM01 mode below) in the interaction region are critical to the output properties. Therefore, the dispersion characteristics and field distributions of the P-TM01 mode in a cylindrical waveguide loaded with annular plasma beam is studied numerically using the all electromagnetic PIC (Particle-in-Cell) code. Variation trends of the dispersion characteristics and the field distributions of the P-TM01 mode with the density np, radial thickness Δrp and radial position rp of the plasma beam, the intensity of the guiding magnetic field Bz and the radius of the waveguide rw are obtained. Simulation results show that: (1) Both np and Δrp affect the dispersion characteristics markedly and the frequency of the P-TM01 mode increases with the increasing of either np or Δrp at the same axial wave number kz. (2) Variations of rp, rw or Bz have very slight influence on the dispersion in the interested range. It is indicated that one can choose relatively larger dimensions of the waveguide for larger power capacity and lower guiding magnetic field for compactness if necessary. (3) The basic features of the field distributions of the P-TM01 mode will not change with the variations of the above mentioned physical parameters. But with the increasing of axial mode number and kz, the electromagnetic energy will be trapped inside the plasma beam gradually and no effective beam-wave interaction will happen in the end. Therefore, it is suggested to choose the operating point with relatively small kz for the efficient operation of PRMG.
2024, 36: 043031.
doi: 10.11884/HPLPB202436.230248
Abstract:
In response to the possible breakdown phenomenon of high-power microwave in atmospheric transmission, our study focuses on the first breakdown delay pulse number in pulse sequences. It is found that it is closely related to seed electrons, pulse breakdown probability, and microwave field strength. Microwave field strength can indirectly affect the pulse breakdown probability and delay pulse number through seed electrons. A method is proposed to estimate the critical field strength of microwave breakdown using the number of delayed pulses, and the microwave critical field strength is defined as the breakdown threshold when the probability of pulse breakdown is greater than a certain value. In this paper, the estimation formula of pulse impulse breakdown probability is derived, and the performance of the estimator is analyzed. Then, the experimental verification is carried out using the S band microwave atmospheric breakdown simulation device. The experimental results show that, within a certain range, the number of pulse delays for repetitive frequency microwave pulse breakdown is only inversely proportional to the seed electron generation rate and pulse width, and can be used to estimate the probability of pulse breakdown, thereby giving the critical field strength for breakdown.
In response to the possible breakdown phenomenon of high-power microwave in atmospheric transmission, our study focuses on the first breakdown delay pulse number in pulse sequences. It is found that it is closely related to seed electrons, pulse breakdown probability, and microwave field strength. Microwave field strength can indirectly affect the pulse breakdown probability and delay pulse number through seed electrons. A method is proposed to estimate the critical field strength of microwave breakdown using the number of delayed pulses, and the microwave critical field strength is defined as the breakdown threshold when the probability of pulse breakdown is greater than a certain value. In this paper, the estimation formula of pulse impulse breakdown probability is derived, and the performance of the estimator is analyzed. Then, the experimental verification is carried out using the S band microwave atmospheric breakdown simulation device. The experimental results show that, within a certain range, the number of pulse delays for repetitive frequency microwave pulse breakdown is only inversely proportional to the seed electron generation rate and pulse width, and can be used to estimate the probability of pulse breakdown, thereby giving the critical field strength for breakdown.
2024, 36: 043032.
doi: 10.11884/HPLPB202436.230101
Abstract:
The relativistic electron beam can hit the target with a high injection rate under the ideal paramagnetic environment, but in reality, due to the influence of the environment, the transmission direction of the relativistic electron beam may deviate from the geomagnetic field at a small angle, thus the Larmor precession will be generated by the action of the geomagnetic field, which affects the target aiming of the electron beam as well as the amount of the injection to the target. In this paper, based on the two-dimensional sheet relativistic electron beam, taking the paramagnetic relativistic electron beam and the beam with 3° angle deviation from the magnetic field as two cases, through the simulation of the propagation of the bunches, we analyze and study the effect of different transmission distance on the bunch to target rate in paramagnetic environment, as well as that of the 3° deviation from the magnetic field on the amount of injection in the propagation process, thus to provide data for reference in the prediction of relativistic electron beam-to-target rate and target aiming.
The relativistic electron beam can hit the target with a high injection rate under the ideal paramagnetic environment, but in reality, due to the influence of the environment, the transmission direction of the relativistic electron beam may deviate from the geomagnetic field at a small angle, thus the Larmor precession will be generated by the action of the geomagnetic field, which affects the target aiming of the electron beam as well as the amount of the injection to the target. In this paper, based on the two-dimensional sheet relativistic electron beam, taking the paramagnetic relativistic electron beam and the beam with 3° angle deviation from the magnetic field as two cases, through the simulation of the propagation of the bunches, we analyze and study the effect of different transmission distance on the bunch to target rate in paramagnetic environment, as well as that of the 3° deviation from the magnetic field on the amount of injection in the propagation process, thus to provide data for reference in the prediction of relativistic electron beam-to-target rate and target aiming.
