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RSS2023 Vol. 35, No. 8
Recommend Articles
column
- Cover and Contents
- Laser Damage of Optical Elements
- High Power Laser Physics and Technology
- Operation and Maintenance of Large Scale Scientific Facility
- Inertial Confinement Fusion Physics and Technology
- High Power Microwave Technology
- Particle Beams and Accelerator Technology
- Pulsed Power Technology
- Nuclear Science and Engineering
- Advanced Interdisciplinary Science
- Research News
Display Method:
2023,
35: 1-2.
2023,
35: 081001.
doi: 10.11884/HPLPB202335.230067
Abstract:
Defects and impurities in optical components can lead to significant reduction in the laser damage threshold, which has become a “bottleneck” in the development of high-power and high-energy laser devices and needs to be solved urgently. In the study of laser damage of optical components, it is found that the laser damage resistance of optical components can be effectively improved by pretreating the surface of the components with a laser below the damage threshold. In this paper, the background, qualitative mechanism, quantitative theoretical model and application status of laser conditioning technology are summarized, and a new film conditioning technology for in-situ real-time laser conditioning of thin films is introduced. Finally, it is pointed out that laser conditioning is one of the most effective methods that can effectively improve the laser induced damage threshold of optical films, optical glasses, and optical crystal components. However, its mechanism, practicality, and instrumentation still need further development.
2023,
35: 081002.
doi: 10.11884/HPLPB202335.220404
Abstract:
Laser driven inertial confinement fusion (ICF) has attracted much attention for its potential to solve the global energy crisis. As fused silica is an important functional ultraviolet (UV) element in the final optics assembly of ICF device, its laser-induced damage has become a key factor limiting the development of ICF output energy to a stronger and higher level. Therefore, the further increase of ICF output energy puts forward a significant application demand for the new UV components that have superior UV laser-induced damage resistance. In this paper, the research status of high-energy UV laser-induced damage of UV fluorophosphate glasses developed by Xi’an Institute of Optics and Precision Mechanics, CAS was reviewed, and the existing practical problems are analyzed. Finally, the development direction of UV fluorophosphate glasses with high laser-induced damage resistance is prospected.
2023,
35: 081003.
doi: 10.11884/HPLPB202335.230201
Abstract:
The bidirectional output fiber laser can achieve two laser outputs through a resonant cavity structure, which can reduce the volume and cost of high-power fiber laser systems and has good application prospects in the industrial field. Based on the oscillator with bidirectional pumping, employing the double cladding ytterbium-doped fiber (DCYDF) with a core/cladding diameter of 30/400 µm which was pumped by the wavelength-stabilized 981 nm laser diodes (LDs), a bidirectional output fiber laser oscillator with a total output power of greater than 8 kW was achieved experimentally for the first time. With the total bidirectional pump power of 10.951 kW, a total output power of 8169 W with 3769 W at end A and 4400 W at end B were achieved, with an O-O efficiency of 74.6%. No TMI or SRS were observed at both ends, and higher laser output power can be expected by further increasing the pumping power.
2023,
35: 081004.
doi: 10.11884/HPLPB202335.230018
Abstract:
Time-resolved X-ray absorption fine structure spectrum technology needs to produce X-ray source with high brightness, uniform and wide spectrum. The M-band radiation source generated by an elementary target has high brightness, but poor uniformity. Therefore, this paper proposes a scheme to generate M-band radiation using a multilayer composite target prepared by a variety of metallic materials. For the K edge X-ray absorption spectroscopy experiment of Si, the optimal material ratio was theoretically calculated according to the previous elementary target M-band spectrum experiment data, and the multilayer composite target composed of Au, Yb, Dy was prepared. The radiation spectrum measurement of the multilayer composite target driven by pulse laser was carried out on the Shenguang II laser facility, and the experimental results were basically consistent with the theoretical calculation. Compared with an elementary target, the M-band radiation source generated by multilayer composite target has the advantages of wide spectrum and uniform overall brightness, and has great application potential in time-resolved X-ray absorption fine structure spectroscopy experiments.
Time-resolved X-ray absorption fine structure spectrum technology needs to produce X-ray source with high brightness, uniform and wide spectrum. The M-band radiation source generated by an elementary target has high brightness, but poor uniformity. Therefore, this paper proposes a scheme to generate M-band radiation using a multilayer composite target prepared by a variety of metallic materials. For the K edge X-ray absorption spectroscopy experiment of Si, the optimal material ratio was theoretically calculated according to the previous elementary target M-band spectrum experiment data, and the multilayer composite target composed of Au, Yb, Dy was prepared. The radiation spectrum measurement of the multilayer composite target driven by pulse laser was carried out on the Shenguang II laser facility, and the experimental results were basically consistent with the theoretical calculation. Compared with an elementary target, the M-band radiation source generated by multilayer composite target has the advantages of wide spectrum and uniform overall brightness, and has great application potential in time-resolved X-ray absorption fine structure spectroscopy experiments.
2023,
35: 081005.
doi: 10.11884/HPLPB202335.230044
Abstract:
Combined with the heat transfer mechanism of honeycomb structure and the ablation mechanism of composites, the thermal response of honeycomb sandwich composite structure under laser irradiation was studied. For typical honeycomb cells, a theoretical microstructure model of thermal conduction and ablation is established. Based on the finite element software thermal analysis module and secondary development program, a high temperature heat transfer numerical model of honeycomb sandwich structure was constructed, taking into account the nonlinear changes of thermal physical parameters, resin pyrolysis and fiber ablation process. Using continuous laser as the loading heat source, the thermal ablation experiments of honeycomb structure in atmospheric environment were designed and carried out, and the dynamic ablation characteristics of honeycomb structure were obtained. The results show that the honeycomb sandwich composite structure has good ablation resistance when the laser power density is 102 W/cm2; The numerical model can accurately simulate the temperature field and the ablation of resin and fiber in the process of laser loading the honeycomb structure, and can obtain comparatively real ablation morphology.
Combined with the heat transfer mechanism of honeycomb structure and the ablation mechanism of composites, the thermal response of honeycomb sandwich composite structure under laser irradiation was studied. For typical honeycomb cells, a theoretical microstructure model of thermal conduction and ablation is established. Based on the finite element software thermal analysis module and secondary development program, a high temperature heat transfer numerical model of honeycomb sandwich structure was constructed, taking into account the nonlinear changes of thermal physical parameters, resin pyrolysis and fiber ablation process. Using continuous laser as the loading heat source, the thermal ablation experiments of honeycomb structure in atmospheric environment were designed and carried out, and the dynamic ablation characteristics of honeycomb structure were obtained. The results show that the honeycomb sandwich composite structure has good ablation resistance when the laser power density is 102 W/cm2; The numerical model can accurately simulate the temperature field and the ablation of resin and fiber in the process of laser loading the honeycomb structure, and can obtain comparatively real ablation morphology.
2023,
35: 081006.
doi: 10.11884/HPLPB202335.230077
Abstract:
For the transfer of the pupil and optical axis position in the design of complex optical mechanical system, the algorithm model of coupling control of the pupil mirror and the optical axis mirror and the analytical formula for implementing control are constructed. Based on the coupling control process, the calibration process and method of each coefficient in the analytical formula are elaborated. At the same time, the rationality of the above model and the analytical formula is verified through the built test optical path. Combined with the calculated pupil and optical axis spot center on the target plane of the detector, the fast coupling of pupil and optical axis can be realized in one step through the linkage control of the two motors of the pupil and optical axis coupling mirrors. The pupil can achieve an accuracy of 0.2% of the near field spot and an accuracy of 3 μrad for the optical axis by performing three different control strategies for the pupil and optical axis coupling.
For the transfer of the pupil and optical axis position in the design of complex optical mechanical system, the algorithm model of coupling control of the pupil mirror and the optical axis mirror and the analytical formula for implementing control are constructed. Based on the coupling control process, the calibration process and method of each coefficient in the analytical formula are elaborated. At the same time, the rationality of the above model and the analytical formula is verified through the built test optical path. Combined with the calculated pupil and optical axis spot center on the target plane of the detector, the fast coupling of pupil and optical axis can be realized in one step through the linkage control of the two motors of the pupil and optical axis coupling mirrors. The pupil can achieve an accuracy of 0.2% of the near field spot and an accuracy of 3 μrad for the optical axis by performing three different control strategies for the pupil and optical axis coupling.
2023,
35: 082001.
doi: 10.11884/HPLPB202335.220320
Abstract:
Laser pulse shape is one of the most critical parameters for the success of inertial confinement fusion experiments. The ability to shape the laser pulse with accuracy, efficiency, and robustness is fundamental for high-power laser facility with individual characteristics and independent adjustability for each beam. An autonomous pulse-shaping method is established by employing an iterative algorithm and some strategies, solving the problem of nonlinear response in the pulse-shaping process, as well as improving the convergence rate. The test results indicate that it is capable of shaping an almost arbitrary pulse waveform at the accuracy of better than 10% (rms) of the deviances within 20 iterations or about 10 min, even a 23∶1 high-contrast-pulse waveform can be done with high quality of pulse and measure condition. With this method, the precise control on the laser pulse shape and the operational efficiency can fully meet the experimental requirements.
Laser pulse shape is one of the most critical parameters for the success of inertial confinement fusion experiments. The ability to shape the laser pulse with accuracy, efficiency, and robustness is fundamental for high-power laser facility with individual characteristics and independent adjustability for each beam. An autonomous pulse-shaping method is established by employing an iterative algorithm and some strategies, solving the problem of nonlinear response in the pulse-shaping process, as well as improving the convergence rate. The test results indicate that it is capable of shaping an almost arbitrary pulse waveform at the accuracy of better than 10% (rms) of the deviances within 20 iterations or about 10 min, even a 23∶1 high-contrast-pulse waveform can be done with high quality of pulse and measure condition. With this method, the precise control on the laser pulse shape and the operational efficiency can fully meet the experimental requirements.
2023,
35: 082002.
doi: 10.11884/HPLPB202335.220294
Abstract:
Aiming at the requirement of the synchronous trigger signals of large-scale laser device with wide spatial distribution and high-precision (one is that the long-term timing jitter is less than 5 ps, and the other is that the time delay resolution is less than 15 ps), a synchronous timing generation scheme of “data stream codec optical transmission,coarse delay by using transceiver, and fine delay by using broadband microstrip delay line” is designed. The optical transmission architecture of the data stream codec realizes the timing alignment over a wide spatial range, and the technology of the transceiver and microstrip delay line solves the problems of low time jitter and high delay resolution. The design and development of the whole system were completed by simulating the timing logic of the system and the key circuits board, and experimental test were carried out. The test results show that the system can realize the generation of synchronous timing signals in a wide spatial range, and the time jitter accuracy is better than 3.76 ps (rms, 8 h ), 39.6ps (peak-to-peak, 8 h), and the time delay resolution is better than 8 ps; If the system is applied to a small spatial range, the time accuracy of the synchronous signal can be better than 1.27 ps (rms, 8 h ), 12.4 ps (peak-to-peak, 8 h).
Aiming at the requirement of the synchronous trigger signals of large-scale laser device with wide spatial distribution and high-precision (one is that the long-term timing jitter is less than 5 ps, and the other is that the time delay resolution is less than 15 ps), a synchronous timing generation scheme of “data stream codec optical transmission,coarse delay by using transceiver, and fine delay by using broadband microstrip delay line” is designed. The optical transmission architecture of the data stream codec realizes the timing alignment over a wide spatial range, and the technology of the transceiver and microstrip delay line solves the problems of low time jitter and high delay resolution. The design and development of the whole system were completed by simulating the timing logic of the system and the key circuits board, and experimental test were carried out. The test results show that the system can realize the generation of synchronous timing signals in a wide spatial range, and the time jitter accuracy is better than 3.76 ps (rms, 8 h ), 39.6ps (peak-to-peak, 8 h), and the time delay resolution is better than 8 ps; If the system is applied to a small spatial range, the time accuracy of the synchronous signal can be better than 1.27 ps (rms, 8 h ), 12.4 ps (peak-to-peak, 8 h).
2023,
35: 082003.
doi: 10.11884/HPLPB202335.220248
Abstract:
In this paper, the precision delay generator with closed-loop monitoring of synchronous timing is developed. To enhance the anti-interference ability of signal transmission, the output of the delay generator is transmitted with optical signals. The optical synchronization signals is transmitted and fed back by using single-fiber feedback optical module. Based on the interpolation time interval measurement method, the time difference between the feedback optical synchronization signal and the reference signal can be measured with high precision. This system realizes the timing closed-loop monitoring of optical synchronization signals, and the error is less than or equal to 250 ps. On the one hand, the precision delay generator can ensure the reliable delivery of the synchronization signal to the trigger object. On the other hand, the inherent delay of the synchronization signal through the light transmission can be obtained according to the compared result between measured time difference and the set timing delay, so as to meet the precise configuration requirements of the precision timing.
In this paper, the precision delay generator with closed-loop monitoring of synchronous timing is developed. To enhance the anti-interference ability of signal transmission, the output of the delay generator is transmitted with optical signals. The optical synchronization signals is transmitted and fed back by using single-fiber feedback optical module. Based on the interpolation time interval measurement method, the time difference between the feedback optical synchronization signal and the reference signal can be measured with high precision. This system realizes the timing closed-loop monitoring of optical synchronization signals, and the error is less than or equal to 250 ps. On the one hand, the precision delay generator can ensure the reliable delivery of the synchronization signal to the trigger object. On the other hand, the inherent delay of the synchronization signal through the light transmission can be obtained according to the compared result between measured time difference and the set timing delay, so as to meet the precise configuration requirements of the precision timing.
2023,
35: 082004.
doi: 10.11884/HPLPB202335.230133
Abstract:
In this paper, by means of the developed two dimensional radiation magneto-hydrodynamic Lagrangian code, the dynamic hohlraums, which are consisted of tungsten plasma shell and low density foam cylinder with or without an embedded hard foam layer on the cylinder and a capsule in the center, are simulated. We understand the effects of the hard foam layer on the hohlraum radiation field, and the coupling of capsule and hohlraum for the capsule fusion, by comparing the simulated results of different configuration hohlraums. After applying a hard foam layer on the low density foam cylinder, the time, uniformity, and the first peak value of radiation field, receipted by the capsule, is delayed, increased, and reduced, respectively. Furthermore, the radiation temperature on the capsule surface is increasing smoothly, and the dwelling time of the hohlraum is prolonged. For a driven current of peak 50 MA and full rise time 300 ns, the dwelling time can be longer than 10 ns, and the radiation temperature at the late time can be higher than 350 eV. The time variation of the radiation temperature is close to that measured in American National Ignition Facility (NIF) hohlraum in which the capsule was imploded and the fusion energy of 1.37 MJ was released. After embedding a capsule into the center of low density foam cylinder, the radiation temperature receipted by the capsule during the late process increases. This implies that both the hard foam layer and the coupling of the capsule and the dynamic hohlraum are good for the capsule ablating implosion.
In this paper, by means of the developed two dimensional radiation magneto-hydrodynamic Lagrangian code, the dynamic hohlraums, which are consisted of tungsten plasma shell and low density foam cylinder with or without an embedded hard foam layer on the cylinder and a capsule in the center, are simulated. We understand the effects of the hard foam layer on the hohlraum radiation field, and the coupling of capsule and hohlraum for the capsule fusion, by comparing the simulated results of different configuration hohlraums. After applying a hard foam layer on the low density foam cylinder, the time, uniformity, and the first peak value of radiation field, receipted by the capsule, is delayed, increased, and reduced, respectively. Furthermore, the radiation temperature on the capsule surface is increasing smoothly, and the dwelling time of the hohlraum is prolonged. For a driven current of peak 50 MA and full rise time 300 ns, the dwelling time can be longer than 10 ns, and the radiation temperature at the late time can be higher than 350 eV. The time variation of the radiation temperature is close to that measured in American National Ignition Facility (NIF) hohlraum in which the capsule was imploded and the fusion energy of 1.37 MJ was released. After embedding a capsule into the center of low density foam cylinder, the radiation temperature receipted by the capsule during the late process increases. This implies that both the hard foam layer and the coupling of the capsule and the dynamic hohlraum are good for the capsule ablating implosion.
2023,
35: 082005.
doi: 10.11884/HPLPB202335.230100
Abstract:
A dual-constrained image reconstruction algorithm based on Kalman filtering is proposed to solve the problem of reconstructing the two-dimensional shock wave fringe image from the compressed image obtained by the Velocity Interferometer System for Any Reflector (VISAR) based on Compressed Ultrafast Photography (CUP). Based on the sparsity and smoothness of fringed images, the algorithm firstly transforms the problem into an optimization problem based on wavelet and total variational double prior constraints, and then, considering the noise of actual imaging, the weighted Kalman filter is used to predict and adjust the existing information of the image, and finally the Kalman filter is introduced into the iterative process of the two-step iterative threshold algorithm, and then the double-constraint optimization problem is solved to realize the accurate reconstruction of the compressed image. In the large-noise simulation experiment, the peak signal-to-noise ratio and structural similarity of the reconstructed images of the algorithm are increased by 4.8 dB and 14.81%, respectively, which significantly improves the image reconstruction quality. In actual experiments, the algorithm reconstructs a clear shock wave fringe image and reduces the maximum relative error of shock wave velocity by 9.57% and the average relative error of shock wave velocity by 2.2%, which verifies the feasibility of the algorithm.
A dual-constrained image reconstruction algorithm based on Kalman filtering is proposed to solve the problem of reconstructing the two-dimensional shock wave fringe image from the compressed image obtained by the Velocity Interferometer System for Any Reflector (VISAR) based on Compressed Ultrafast Photography (CUP). Based on the sparsity and smoothness of fringed images, the algorithm firstly transforms the problem into an optimization problem based on wavelet and total variational double prior constraints, and then, considering the noise of actual imaging, the weighted Kalman filter is used to predict and adjust the existing information of the image, and finally the Kalman filter is introduced into the iterative process of the two-step iterative threshold algorithm, and then the double-constraint optimization problem is solved to realize the accurate reconstruction of the compressed image. In the large-noise simulation experiment, the peak signal-to-noise ratio and structural similarity of the reconstructed images of the algorithm are increased by 4.8 dB and 14.81%, respectively, which significantly improves the image reconstruction quality. In actual experiments, the algorithm reconstructs a clear shock wave fringe image and reduces the maximum relative error of shock wave velocity by 9.57% and the average relative error of shock wave velocity by 2.2%, which verifies the feasibility of the algorithm.
2023,
35: 083001.
doi: 10.11884/HPLPB202335.230089
Abstract:
To master the anti-electromagnetic interference performance of radar equipment, it is necessary to carry out comprehensive electromagnetic environment effect test and evaluation to provide technical support for radar application and electromagnetic protection reinforcement. Based on the mechanism of pseudo-signal interference effect of second-order intermodulation electromagnetic radiation, the concept of effect index is introduced to characterize the multivariable problem of complex electromagnetic environment adaptability with a single variable. The quantitative characterization of pseudo-signal interference effect of radar equipment in complex electromagnetic environment is realized, and the evaluation model of pseudo-signal interference effect of second-order intermodulation is established. Taking a certain type of sweep frequency continuous wave ranging radar as the research object, aiming at the second-order intermodulation pseudo-signal interference phenomenon in the test radar, the method of determining the model parameters is given, and the prediction and evaluation method of the second-order intermodulation pseudo-signal interference effect of radar equipment is proposed. Experimental verification shows that whether it is to change the pseudo-signal sensitivity level, or to change the dual-frequency electromagnetic radiation combination in the range of large radiation frequency offset and large intermodulation difference, the universal second-order intermodulation pseudo-signal interference effect model can be used to evaluate the second-order intermodulation pseudo-signal interference effect of the tested radar. The evaluation error is within 2.5 dB, and the second-order intermodulation pseudo-signal interference of radar equipment can be objectively evaluated according to the effect prediction method.
To master the anti-electromagnetic interference performance of radar equipment, it is necessary to carry out comprehensive electromagnetic environment effect test and evaluation to provide technical support for radar application and electromagnetic protection reinforcement. Based on the mechanism of pseudo-signal interference effect of second-order intermodulation electromagnetic radiation, the concept of effect index is introduced to characterize the multivariable problem of complex electromagnetic environment adaptability with a single variable. The quantitative characterization of pseudo-signal interference effect of radar equipment in complex electromagnetic environment is realized, and the evaluation model of pseudo-signal interference effect of second-order intermodulation is established. Taking a certain type of sweep frequency continuous wave ranging radar as the research object, aiming at the second-order intermodulation pseudo-signal interference phenomenon in the test radar, the method of determining the model parameters is given, and the prediction and evaluation method of the second-order intermodulation pseudo-signal interference effect of radar equipment is proposed. Experimental verification shows that whether it is to change the pseudo-signal sensitivity level, or to change the dual-frequency electromagnetic radiation combination in the range of large radiation frequency offset and large intermodulation difference, the universal second-order intermodulation pseudo-signal interference effect model can be used to evaluate the second-order intermodulation pseudo-signal interference effect of the tested radar. The evaluation error is within 2.5 dB, and the second-order intermodulation pseudo-signal interference of radar equipment can be objectively evaluated according to the effect prediction method.
2023,
35: 083002.
doi: 10.11884/HPLPB202335.220287
Abstract:
To realize the high-purity TE01 mode input of the Ka-band cyclotron traveling wave tube, the two-stage power divider TE01 input coupler is improved by adding a filter structure at the output port, and the transmission efficiency of the spurious mode is reduced from the original average of 7% to less than 2%. The main body of the structure is a cascading two-stage Y-type power divider network, which can efficiently realize the conversion of rectangular waveguide TE10 mode to circular waveguide TE01 mode. Based on the theoretical analysis of transmission performance of power divider network based on transmission line theory, and with the help of 3D electromagnetic simulation software, several optimization iterations are carried out, and finally a wideband TE01 input coupler with mode conversion efficiency greater than 99% near the frequency of 31 GHz is obtained, the input coupling structure has a −0.1 dB insertion loss bandwidth of 5 GHz, and the average mode conversion efficiency in the effective frequency band is as high as 98.6%, the mode purity is 99% and the return loss is less than −15 dB. Back-to-back cold test experiments were carried out on the device using vector network analyzer, and the results show that the in-band attenuation is about 0.5 dB, which deviates little from the simulation calculation result, which meets the actual engineering requirements.
To realize the high-purity TE01 mode input of the Ka-band cyclotron traveling wave tube, the two-stage power divider TE01 input coupler is improved by adding a filter structure at the output port, and the transmission efficiency of the spurious mode is reduced from the original average of 7% to less than 2%. The main body of the structure is a cascading two-stage Y-type power divider network, which can efficiently realize the conversion of rectangular waveguide TE10 mode to circular waveguide TE01 mode. Based on the theoretical analysis of transmission performance of power divider network based on transmission line theory, and with the help of 3D electromagnetic simulation software, several optimization iterations are carried out, and finally a wideband TE01 input coupler with mode conversion efficiency greater than 99% near the frequency of 31 GHz is obtained, the input coupling structure has a −0.1 dB insertion loss bandwidth of 5 GHz, and the average mode conversion efficiency in the effective frequency band is as high as 98.6%, the mode purity is 99% and the return loss is less than −15 dB. Back-to-back cold test experiments were carried out on the device using vector network analyzer, and the results show that the in-band attenuation is about 0.5 dB, which deviates little from the simulation calculation result, which meets the actual engineering requirements.
2023,
35: 083003.
doi: 10.11884/HPLPB202335.230050
Abstract:
Comb spectrum microwave usually refers to electromagnetic wave with center frequency spectrum distribution similar to comb shape, and energy distribution at multiple frequency points within a certain bandwidth. Comb spectrum microwave has unique advantages in electronic countermeasure that other countermeasure ways do not have, and shows an excellent application prospect in communication countermeasure, radar countermeasure and other fields. This paper introduces a method to generate high power comb spectrum microwave. The microwave generated by wideband continuous wave source is compressed by using channel encoding pulse compression technology to obtain the comb spectrum microwave with center frequency of 2.85 GHz, bandwidth of 1 GHz, spectral gap of 250 kHz and peak power of 160 kW. The subsequent experiments further show that the center frequency, bandwidth and spectral gap of comb spectrum microwave obtained by this method are flexible and adjustable, which can be used in a variety of electronic countermeasure scenarios to improve the anti-jamming capability.
Comb spectrum microwave usually refers to electromagnetic wave with center frequency spectrum distribution similar to comb shape, and energy distribution at multiple frequency points within a certain bandwidth. Comb spectrum microwave has unique advantages in electronic countermeasure that other countermeasure ways do not have, and shows an excellent application prospect in communication countermeasure, radar countermeasure and other fields. This paper introduces a method to generate high power comb spectrum microwave. The microwave generated by wideband continuous wave source is compressed by using channel encoding pulse compression technology to obtain the comb spectrum microwave with center frequency of 2.85 GHz, bandwidth of 1 GHz, spectral gap of 250 kHz and peak power of 160 kW. The subsequent experiments further show that the center frequency, bandwidth and spectral gap of comb spectrum microwave obtained by this method are flexible and adjustable, which can be used in a variety of electronic countermeasure scenarios to improve the anti-jamming capability.
2023,
35: 083004.
doi: 10.11884/HPLPB202335.230114
Abstract:
The design and latest experimental progress of a 105/140 GHz dual-frequency megawatt-level gyrotron for fusion applications are presented. The resonant cavity, quasi-optical mode converter and BN output window of the gyrotron adopt the design of dual-frequency sharing, the electron gun adopts the triode magnetron injection gun with dual-frequency multiplexing, and the collecting pole adopts the single-stage depressed collector. The experimental results are as follows: under the ms short-pulse condition with repetitive rate of 1 Hz, pulse powers of 710 kW at 105 GHz and 1.057 MW at 140 GHz have been achieved. The pulse width is 0.7 ms, and the total efficiency is 34% at 105 GHz and 49% at 140 GHz, respectively. Through pulse width extension and aging, the experimental results of 105 GHz/300 kW/2 s, 105 GHz/400 kW/1 s and 140 GHz/400 kW/1 s are obtained. The temperature of BN window reaches 606 ℃, 503 ℃ and 633 ℃, respectively, in the three states. The frequencies during long-pulse operations are stable, indicating that there are no parasitic modes. The experiment basically verifies the physical design of the device.
The design and latest experimental progress of a 105/140 GHz dual-frequency megawatt-level gyrotron for fusion applications are presented. The resonant cavity, quasi-optical mode converter and BN output window of the gyrotron adopt the design of dual-frequency sharing, the electron gun adopts the triode magnetron injection gun with dual-frequency multiplexing, and the collecting pole adopts the single-stage depressed collector. The experimental results are as follows: under the ms short-pulse condition with repetitive rate of 1 Hz, pulse powers of 710 kW at 105 GHz and 1.057 MW at 140 GHz have been achieved. The pulse width is 0.7 ms, and the total efficiency is 34% at 105 GHz and 49% at 140 GHz, respectively. Through pulse width extension and aging, the experimental results of 105 GHz/300 kW/2 s, 105 GHz/400 kW/1 s and 140 GHz/400 kW/1 s are obtained. The temperature of BN window reaches 606 ℃, 503 ℃ and 633 ℃, respectively, in the three states. The frequencies during long-pulse operations are stable, indicating that there are no parasitic modes. The experiment basically verifies the physical design of the device.
2023,
35: 084001.
doi: 10.11884/HPLPB202335.230014
Abstract:
There are hundreds of electric power supplies and radio frequency equipment in the accelerator of CSNS. Operations of these devices are executed through twenty-odd operator interfaces, which are time-consuming and cumbersome. During these processes, breakdowns are easy to occur but difficult to debug. To simplify the machine operation process, a one-key-on/off-operation program is developed. This program integrates the twenty-odd operator interfaces into a single one. The switch on/off operation of every device is realized in a thread, and the program completes the operation of all the devices concurrently. This program accomplishes the machine snapshot save/restore and the switch on/off operation of all the electric power supplies and radio frequency equipment through a one-button operation in the operator interface. With this program, the time needed to switch on/off all the devices in the machine is reduced from forty minutes to about two minutes. This program could be applied to other facilities.
There are hundreds of electric power supplies and radio frequency equipment in the accelerator of CSNS. Operations of these devices are executed through twenty-odd operator interfaces, which are time-consuming and cumbersome. During these processes, breakdowns are easy to occur but difficult to debug. To simplify the machine operation process, a one-key-on/off-operation program is developed. This program integrates the twenty-odd operator interfaces into a single one. The switch on/off operation of every device is realized in a thread, and the program completes the operation of all the devices concurrently. This program accomplishes the machine snapshot save/restore and the switch on/off operation of all the electric power supplies and radio frequency equipment through a one-button operation in the operator interface. With this program, the time needed to switch on/off all the devices in the machine is reduced from forty minutes to about two minutes. This program could be applied to other facilities.
2023,
35: 084002.
doi: 10.11884/HPLPB202335.220303
Abstract:
An electron beam radiation device for sterilization of the packing box surface was developed successfully at Institute of Modern Physics (IMP), and the reliability test of 8 h was achieved for industrial application. Six electron curtain accelerators were installed in the sterilization transport line for processing the six whole surfaces of the box. This paper introduces the design of the electron curtain accelerator. The E-gun code was used to compute the trajectories of the electron beam, and it is proved valid with experimental results. The high voltage insulating structure is optimized based on CST software to improve the uniformity of the electric field and decrease the numbers of the high voltage breakdown. Finally, the radiation dose distribution was tested and the inhomogeneity is less than 10%, which meets the requirement for the industrial application.
An electron beam radiation device for sterilization of the packing box surface was developed successfully at Institute of Modern Physics (IMP), and the reliability test of 8 h was achieved for industrial application. Six electron curtain accelerators were installed in the sterilization transport line for processing the six whole surfaces of the box. This paper introduces the design of the electron curtain accelerator. The E-gun code was used to compute the trajectories of the electron beam, and it is proved valid with experimental results. The high voltage insulating structure is optimized based on CST software to improve the uniformity of the electric field and decrease the numbers of the high voltage breakdown. Finally, the radiation dose distribution was tested and the inhomogeneity is less than 10%, which meets the requirement for the industrial application.
2023,
35: 085001.
doi: 10.11884/HPLPB202335.230034
Abstract:
High voltage DC power supply is widely used in research and application areas of electron beam. Recently the method of decreasing ripple is a research hotspot due to the ripple of high voltage is the very key factor to quality of beams. This paper studies a novel circuit topology, which is comprised of a high bridge converter and a double polarity Cockcroft-Walton circuit with unsymmetrical capacitors. The experimental results show that the ripple is lower than 0.06% when the output voltage and current are 100 kV and 25 mA, respectively. Meanwhile the storage energy of high voltage units is only 0.85 of traditional circuit.
High voltage DC power supply is widely used in research and application areas of electron beam. Recently the method of decreasing ripple is a research hotspot due to the ripple of high voltage is the very key factor to quality of beams. This paper studies a novel circuit topology, which is comprised of a high bridge converter and a double polarity Cockcroft-Walton circuit with unsymmetrical capacitors. The experimental results show that the ripple is lower than 0.06% when the output voltage and current are 100 kV and 25 mA, respectively. Meanwhile the storage energy of high voltage units is only 0.85 of traditional circuit.
2023,
35: 085002.
doi: 10.11884/HPLPB202335.230108
Abstract:
To achieve synchronous driving of multiple SiC MOSFET switches in an all solid-state Marx generator, a drive control circuit based on a pulse transformer was designed. The synchronization of multiple drive signals can affect the output waveform parameters of the Marx generator, thus it is required that the drive signal have the characteristics of fast pulse front and low jitter. According to the driving principle and requirements of SiC MOSFET, the influencing factors of pulse front in SiC MOSFET driving circuit were analyzed, and its related parameters were calculated and simulated for verification. A pulse transformer with 10 primary core piercing stages in series was designed, with 1 turn for the primary and 9 turns for the secondary. The second stage was driven by a 10 stage Marx circuit after passing through a positive and negative pulse signal conditioning circuit. The actual measurement results indicate that the resonant circuit composed of the primary leakage inductance of the pulse transformer and the resonant capacitor in intermittent mode has higher driving power, faster pulse front, and better synchronization. The pulse front of the synchronous driving circuit is 112 ns, the pulse width is adjustable from 1 μs to 10 μs, and the frequency is adjustable from 10 kHz to 25 kHz, which can meet the adjustment requirements of solid-state Marx generator parameters.
To achieve synchronous driving of multiple SiC MOSFET switches in an all solid-state Marx generator, a drive control circuit based on a pulse transformer was designed. The synchronization of multiple drive signals can affect the output waveform parameters of the Marx generator, thus it is required that the drive signal have the characteristics of fast pulse front and low jitter. According to the driving principle and requirements of SiC MOSFET, the influencing factors of pulse front in SiC MOSFET driving circuit were analyzed, and its related parameters were calculated and simulated for verification. A pulse transformer with 10 primary core piercing stages in series was designed, with 1 turn for the primary and 9 turns for the secondary. The second stage was driven by a 10 stage Marx circuit after passing through a positive and negative pulse signal conditioning circuit. The actual measurement results indicate that the resonant circuit composed of the primary leakage inductance of the pulse transformer and the resonant capacitor in intermittent mode has higher driving power, faster pulse front, and better synchronization. The pulse front of the synchronous driving circuit is 112 ns, the pulse width is adjustable from 1 μs to 10 μs, and the frequency is adjustable from 10 kHz to 25 kHz, which can meet the adjustment requirements of solid-state Marx generator parameters.
2023,
35: 085003.
doi: 10.11884/HPLPB202335.230002
Abstract:
LC resonant charging scheme is suitable for high repetition rate pulse power system because of its simple circuit structure and control method, small size and high power efficiency. To make the LC resonant charging scheme with a higher boost range and improve its adaptability to supply voltage changes, this paper adopts a circuit topology with a boost structure, which enables the LC resonant charging scheme to have the ability to boost and reduce voltage. At the same time, it uses a control algorithm based on real-time energy detection, which enables the scheme to accurately charge and discharge according to preset parameters, and enhances the adaptability to supply voltage fluctuations. The preliminary experimental results show that the power supply can complete the regulation of voltage rise and fall when the supply voltage fluctuates, and the maximum voltage deviation is less than 5 V, thus it has higher charging accuracy and better charging consistency.
LC resonant charging scheme is suitable for high repetition rate pulse power system because of its simple circuit structure and control method, small size and high power efficiency. To make the LC resonant charging scheme with a higher boost range and improve its adaptability to supply voltage changes, this paper adopts a circuit topology with a boost structure, which enables the LC resonant charging scheme to have the ability to boost and reduce voltage. At the same time, it uses a control algorithm based on real-time energy detection, which enables the scheme to accurately charge and discharge according to preset parameters, and enhances the adaptability to supply voltage fluctuations. The preliminary experimental results show that the power supply can complete the regulation of voltage rise and fall when the supply voltage fluctuates, and the maximum voltage deviation is less than 5 V, thus it has higher charging accuracy and better charging consistency.
2023,
35: 086001.
doi: 10.11884/HPLPB202335.220421
Abstract:
Based on Nuctech radiography Monte Carlo simulation software NucRPD, three methods are developed to analyze the effect of the two-dimensional anti-scatter grid in the container CT inspection system with a 9MeV accelerator: target crystal pen tag method, scattered component tag method, and tomography image reconstruction method. Calculation results of the three methods all show that the profit of the two-dimensional anti-scatter grid in reducing scattered X-rays in this container CT inspection system is limited. It is suggested that the two-dimensional anti-scatter grid not to be used in the subsequent engineering implementation, which will greatly reduce not only the mechanical design difficulty of the detector and rotating gantry, but also the engineering cost.
Based on Nuctech radiography Monte Carlo simulation software NucRPD, three methods are developed to analyze the effect of the two-dimensional anti-scatter grid in the container CT inspection system with a 9MeV accelerator: target crystal pen tag method, scattered component tag method, and tomography image reconstruction method. Calculation results of the three methods all show that the profit of the two-dimensional anti-scatter grid in reducing scattered X-rays in this container CT inspection system is limited. It is suggested that the two-dimensional anti-scatter grid not to be used in the subsequent engineering implementation, which will greatly reduce not only the mechanical design difficulty of the detector and rotating gantry, but also the engineering cost.
2023,
35: 089001.
doi: 10.11884/HPLPB202335.220361
Abstract:
During the flight of hypersonic vehicle, plasma sheath will be produced on the surface due to the influence of surface shockwave. Because the plasma sheath will absorb, reflect and scatter electromagnetic waves, the communication signal will be attenuated or even interrupted, causing “blackout” problem. Theoretically, the interaction between the plasma sheath and microwave is nonlinearly changing with electric field, so there may be a suitable E-field amplitude and irradiation time interval to make electromagnetic wave transmissivity rise. For this possibility, Finite Element Analysis is used to conduct a two-dimensional coupled simulation of the plasma sheath flow field and the electromagnetic field on the hypersonic vehicle’s surface, and the change of the plasma sheath transmissivity after microwave irradiation is obtained. The plasma sheath was irradiated for 30 ns with electric field of 5×104 V/m, 1×105 V/m, 2.5×105 V/m, 5×105 V/m, respectively. The maximum transmissivity to 1.2 GHz and 1.6 GHz electromagnetic waves is enhanced after irradiation. It provides a new possibility to solve the “blackout” problem.
During the flight of hypersonic vehicle, plasma sheath will be produced on the surface due to the influence of surface shockwave. Because the plasma sheath will absorb, reflect and scatter electromagnetic waves, the communication signal will be attenuated or even interrupted, causing “blackout” problem. Theoretically, the interaction between the plasma sheath and microwave is nonlinearly changing with electric field, so there may be a suitable E-field amplitude and irradiation time interval to make electromagnetic wave transmissivity rise. For this possibility, Finite Element Analysis is used to conduct a two-dimensional coupled simulation of the plasma sheath flow field and the electromagnetic field on the hypersonic vehicle’s surface, and the change of the plasma sheath transmissivity after microwave irradiation is obtained. The plasma sheath was irradiated for 30 ns with electric field of 5×104 V/m, 1×105 V/m, 2.5×105 V/m, 5×105 V/m, respectively. The maximum transmissivity to 1.2 GHz and 1.6 GHz electromagnetic waves is enhanced after irradiation. It provides a new possibility to solve the “blackout” problem.
2023,
35: 089002.
doi: 10.11884/HPLPB202335.230040
Abstract:
Optical elements are the core components of laser systems, and their health status is the key to the stable operation of laser systems. How to realize real-time monitoring and fault diagnosis of optical elements in the working status of laser systems is a problem that urgently needs to be solved in this professional field. To solve this problem, this paper proposes a fault diagnosis method for optical elements based on infrared and visible light videos. Firstly, a long-wave infrared camera and a visible light camera are used to collect video information during the working process of the optical element. Then, the collected video information is processed using anomaly point detection algorithms. Finally, the fault diagnosis and localization of the optical element are carried out in combination with the thermal rise characteristics of the optical element. The experimental results show that, under the same algorithm, the method proposed in this paper has improved the fault diagnosis precision rate, false alarm rate and missed alarm rate by 9.70%, 3.60% and 6.10%, respectively, compared with the method of fault diagnosis using infrared videos alone; the method proposed in this paper has improved the fault diagnosis precision rate, false alarm rate and missed alarm rate by 18.00%, 16.00% and 2.00%, respectively, compared with the method of fault diagnosis using visible light videos alone.
Optical elements are the core components of laser systems, and their health status is the key to the stable operation of laser systems. How to realize real-time monitoring and fault diagnosis of optical elements in the working status of laser systems is a problem that urgently needs to be solved in this professional field. To solve this problem, this paper proposes a fault diagnosis method for optical elements based on infrared and visible light videos. Firstly, a long-wave infrared camera and a visible light camera are used to collect video information during the working process of the optical element. Then, the collected video information is processed using anomaly point detection algorithms. Finally, the fault diagnosis and localization of the optical element are carried out in combination with the thermal rise characteristics of the optical element. The experimental results show that, under the same algorithm, the method proposed in this paper has improved the fault diagnosis precision rate, false alarm rate and missed alarm rate by 9.70%, 3.60% and 6.10%, respectively, compared with the method of fault diagnosis using infrared videos alone; the method proposed in this paper has improved the fault diagnosis precision rate, false alarm rate and missed alarm rate by 18.00%, 16.00% and 2.00%, respectively, compared with the method of fault diagnosis using visible light videos alone.
