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RSS2018 Vol. 30, No. 6
Recommend Articles
column
- Project Progress Report
- Overview
- High Power Laser and Optics
- ICF and Laser Plasma
- High Power Microwave
- Terahertz Technology
- Complex Electromagnetic Environment
- Particle Beams Technology
- Micro-nano Technology
- Pulsed Power Technology
- Accelerator Technology
- Nuclear Science and Engineering
- Applications of Laser and Particle Beams
- 本期封面及目录
Display Method:
2018,
30: 060201.
doi: 10.11884/HPLPB201830.180087
Abstract:
Mode (transverse mode) is one of the key parameters, which could be deduced from the status of the fiber lasers with different mode properties. The relationship between mode and beam quality is analyzed by numerical calculations, based on which it is pointed out that mode decomposition is the key to well understand the mode constitution and beam quality, then the common mode decomposition techniques are introduced. Aimed at mode instability (MI), which is a new phenomenon that prohibits power scaling of fiber laser, various parameters affecting the threshold of MI are summarized, then the physical mechanism and technique to increase the threshold are concluded. The recent progress on mode control of fiber laser is introduced from the viewpoint of high-order-mode suppression and structured light field generation.
Mode (transverse mode) is one of the key parameters, which could be deduced from the status of the fiber lasers with different mode properties. The relationship between mode and beam quality is analyzed by numerical calculations, based on which it is pointed out that mode decomposition is the key to well understand the mode constitution and beam quality, then the common mode decomposition techniques are introduced. Aimed at mode instability (MI), which is a new phenomenon that prohibits power scaling of fiber laser, various parameters affecting the threshold of MI are summarized, then the physical mechanism and technique to increase the threshold are concluded. The recent progress on mode control of fiber laser is introduced from the viewpoint of high-order-mode suppression and structured light field generation.
2018,
30: 061001.
doi: 10.11884/HPLPB201830.170492
Abstract:
Laterally graded periodic [Mo/B4C]60 multilayer mirrors for an EUV interval of 6.8-11.0 nm were deposited by direct current magnetron sputtering on silicon substrate. The structure properties and performance of laterally graded [Mo/B4C]60 multilayers were investigated by grazing X-ray reflectivity measurements and synchrotron radiation reflectance measurements. The results show that the multilayer period thickness D-spacing varies linearly from 4.39 nm to 7.82 nm in the long direction of the sample, indicating the average D-spacing gradient of 0.054 nm/mm. Reflectance of all measured point on the mirror is about 10% at the incident angle of 45°. Spectral width (FWHM) of the reflectance peaks varies from 0.13 nm to 0.31 nm with the increase of multilayer period thickness.
Laterally graded periodic [Mo/B4C]60 multilayer mirrors for an EUV interval of 6.8-11.0 nm were deposited by direct current magnetron sputtering on silicon substrate. The structure properties and performance of laterally graded [Mo/B4C]60 multilayers were investigated by grazing X-ray reflectivity measurements and synchrotron radiation reflectance measurements. The results show that the multilayer period thickness D-spacing varies linearly from 4.39 nm to 7.82 nm in the long direction of the sample, indicating the average D-spacing gradient of 0.054 nm/mm. Reflectance of all measured point on the mirror is about 10% at the incident angle of 45°. Spectral width (FWHM) of the reflectance peaks varies from 0.13 nm to 0.31 nm with the increase of multilayer period thickness.
2018,
30: 061002.
doi: 10.11884/HPLPB201830.170511
Abstract:
The complex sky cloud background edge and infrared dim small target cannot be distinguished using traditional tracking algorithms, and the "deviation" problem is produced when tracking the target. To solve this problem, this paper proposes a target tracking algorithm based on Gaussian curvature filter (GCF) and spatio-temporal context (STC) after introducing the STC theory and analyzing the reason of "deviation". First of all, the context areas are dealt with GCF which can reserve the image edge and eliminate the noise and the infrared dim small target, so as to obtain the infrared dim small target's accurate confidence map. Then the infrared dim small target's coordinates are confirmed by the confidence map. Four groups of the infrared dim small target sequences in the complex sky background experimental results prove that the proposed algorithm is effective, compared with several classical algorithms, such as TMT, MS-PF and FCT. The proposed algorithm has better performance than the three traditional algorithms on subjective vision and objective evaluating indicator and shows higher tracking accuracy and better real time performance. The infrared dim small target in complex sky cloud background can be effectively tracked with this algorithm.
The complex sky cloud background edge and infrared dim small target cannot be distinguished using traditional tracking algorithms, and the "deviation" problem is produced when tracking the target. To solve this problem, this paper proposes a target tracking algorithm based on Gaussian curvature filter (GCF) and spatio-temporal context (STC) after introducing the STC theory and analyzing the reason of "deviation". First of all, the context areas are dealt with GCF which can reserve the image edge and eliminate the noise and the infrared dim small target, so as to obtain the infrared dim small target's accurate confidence map. Then the infrared dim small target's coordinates are confirmed by the confidence map. Four groups of the infrared dim small target sequences in the complex sky background experimental results prove that the proposed algorithm is effective, compared with several classical algorithms, such as TMT, MS-PF and FCT. The proposed algorithm has better performance than the three traditional algorithms on subjective vision and objective evaluating indicator and shows higher tracking accuracy and better real time performance. The infrared dim small target in complex sky cloud background can be effectively tracked with this algorithm.
2018,
30: 062001.
doi: 10.11884/HPLPB201830.180011
Abstract:
Much deformation of the large aperture mirror by deadweight leads to large PV (peak-to-valley) value of its aperture surface, and it is hard to ensure the point accuracy on laser beams of optical facility. Finite element model is built up to calculate the PV value of the mirror surface in this paper. Moreover, parameters including position and size of erection column as well as the mirror thickness are optimized in order to minimize the PV value of the aperture surface. Both the direct optimization based on finite element model and the optimization based on surrogate model are adopted herein, and the PV value is reduced by 74% of its initial value as a result. In contrast to direct optimization, optimization based on surrogate model conveniently provides the objective variation with design variables and sensitivity analysis as well, which brings much benefit for structure design. In case of numerous and wide-range design variables, it is suggested to firstly decrease the design range according to prior knowledge or low-fidelity surrogate model and then optimize the parameters based on high-fidelity surrogate model within the shrunk range in order to avoid large amount of calculation. Furthermore, a scheme of four-cylinder support is recommended to replace the three-cylinder support for smaller PV value according to the optimization result.
Much deformation of the large aperture mirror by deadweight leads to large PV (peak-to-valley) value of its aperture surface, and it is hard to ensure the point accuracy on laser beams of optical facility. Finite element model is built up to calculate the PV value of the mirror surface in this paper. Moreover, parameters including position and size of erection column as well as the mirror thickness are optimized in order to minimize the PV value of the aperture surface. Both the direct optimization based on finite element model and the optimization based on surrogate model are adopted herein, and the PV value is reduced by 74% of its initial value as a result. In contrast to direct optimization, optimization based on surrogate model conveniently provides the objective variation with design variables and sensitivity analysis as well, which brings much benefit for structure design. In case of numerous and wide-range design variables, it is suggested to firstly decrease the design range according to prior knowledge or low-fidelity surrogate model and then optimize the parameters based on high-fidelity surrogate model within the shrunk range in order to avoid large amount of calculation. Furthermore, a scheme of four-cylinder support is recommended to replace the three-cylinder support for smaller PV value according to the optimization result.
2018,
30: 062002.
doi: 10.11884/HPLPB201830.170440
Abstract:
Based on the urgent need of conducting imaging diagnostics of dense laser-produced plasma, we present the optical system design of Wolter type X-ray microscope based on Abbe's sine condition. This paper details the structural features and optical design approaches of Wolter microscope. The impacts of initial structure parameters including the object distance, magnification, grazing angle and mirror length of hyperbolic mirror on objective performance are studied quantitatively. According to ray-tracing simulation, the spatial resolution is better than 1 μm in a range of ±260 μm and better than 3 μm in a range of ±460 μm. The effective field of view is estimated as about 1 mm in diameter with a geometric solid angle of 6.1×10-5 sr. The system is flat-response with an efficiency consistency of 93.7% over the field of view. This paper contributes to the development of high-resolution and high-flux hard X-ray imaging diagnostic instruments in the future.
Based on the urgent need of conducting imaging diagnostics of dense laser-produced plasma, we present the optical system design of Wolter type X-ray microscope based on Abbe's sine condition. This paper details the structural features and optical design approaches of Wolter microscope. The impacts of initial structure parameters including the object distance, magnification, grazing angle and mirror length of hyperbolic mirror on objective performance are studied quantitatively. According to ray-tracing simulation, the spatial resolution is better than 1 μm in a range of ±260 μm and better than 3 μm in a range of ±460 μm. The effective field of view is estimated as about 1 mm in diameter with a geometric solid angle of 6.1×10-5 sr. The system is flat-response with an efficiency consistency of 93.7% over the field of view. This paper contributes to the development of high-resolution and high-flux hard X-ray imaging diagnostic instruments in the future.
2018,
30: 062003.
doi: 10.11884/HPLPB201830.170457
Abstract:
The mid-spatial-frequency error (MSFR) of large aperture aspherical optical elements have a direct influence on the precision of the beam diffusion function and the energy scattering of the high energy laser. To solve this problem, we put forward a kind of multi-tool NC polishing technology of computer controlled optical surfacing(CCOS) for effective suppression of MSFR. The polishing process of semi-rigid polishing tool is analyzed by finite element methods, and the polishing process is theoretically simulated based on Bridging model. The experimental results show that the MSFR of large aperture aspherical optical elements can be effectively reduced by multi-tool polishing technology. The wavefront PSD1 value of specific spatial frequency has been restrained effectively. For the two finished ϕ460 mm elements, the wavefront PSD1 value has a 70% descend down to 2.835 nm. Besides, the PV value is less than 0.16λ(632.8 nm) and the RMS value is less than 0.02λ.
The mid-spatial-frequency error (MSFR) of large aperture aspherical optical elements have a direct influence on the precision of the beam diffusion function and the energy scattering of the high energy laser. To solve this problem, we put forward a kind of multi-tool NC polishing technology of computer controlled optical surfacing(CCOS) for effective suppression of MSFR. The polishing process of semi-rigid polishing tool is analyzed by finite element methods, and the polishing process is theoretically simulated based on Bridging model. The experimental results show that the MSFR of large aperture aspherical optical elements can be effectively reduced by multi-tool polishing technology. The wavefront PSD1 value of specific spatial frequency has been restrained effectively. For the two finished ϕ460 mm elements, the wavefront PSD1 value has a 70% descend down to 2.835 nm. Besides, the PV value is less than 0.16λ(632.8 nm) and the RMS value is less than 0.02λ.
2018,
30: 063001.
doi: 10.11884/HPLPB201830.170463
Abstract:
Analysis for the radiation pattern of antennas with physical optics method is now widely used in the calculation for far field pattern of reflector antennas, which has fast computing speed and low memory requirements. The expression to calculate the far field of reflector antennas using the Stratton-Chu integral formula is derived based on surface current, and the directivity of an offset reflector antenna calculated in MATLAB is right using this method comparing with the results in the reference. The expression to calculate the gain of antennas is derived with cosqθ as pattern of the feed. The offset reflector antenna is shaped for good gain flatness during scanning in the pitching direction for 20°, and the far field pattern of shaped reflected antenna is analyzed. Results of gain of the reflector antenna in different scanning angles before and after shaping is calculated, which show that the gain flatness is improved by shaping and less time and lower memory space is taken using this method to analyse the far field pattern of antennas with physical optics method.
Analysis for the radiation pattern of antennas with physical optics method is now widely used in the calculation for far field pattern of reflector antennas, which has fast computing speed and low memory requirements. The expression to calculate the far field of reflector antennas using the Stratton-Chu integral formula is derived based on surface current, and the directivity of an offset reflector antenna calculated in MATLAB is right using this method comparing with the results in the reference. The expression to calculate the gain of antennas is derived with cosqθ as pattern of the feed. The offset reflector antenna is shaped for good gain flatness during scanning in the pitching direction for 20°, and the far field pattern of shaped reflected antenna is analyzed. Results of gain of the reflector antenna in different scanning angles before and after shaping is calculated, which show that the gain flatness is improved by shaping and less time and lower memory space is taken using this method to analyse the far field pattern of antennas with physical optics method.
2018,
30: 063002.
doi: 10.11884/HPLPB201830.170426
Abstract:
Based on the device physics simulation, focusing on the influence of pulse interval on thermal damage process of PIN limiter, the peak temperature of combined pulses with different pulse interval from 1 to 20 ns is studied. Numerical simulation results show that the pulse interval in which the device temperature rises most has a positive relationship with intrinsic region thickness. The thermal breakdown mechanism is analyzed. It is the spike leakage of the second sub-pulse that makes the temperature rise speed up. And the high temperature of the P-type region also causes the electrothermal feedback which makes it easier to get higher temperature.
Based on the device physics simulation, focusing on the influence of pulse interval on thermal damage process of PIN limiter, the peak temperature of combined pulses with different pulse interval from 1 to 20 ns is studied. Numerical simulation results show that the pulse interval in which the device temperature rises most has a positive relationship with intrinsic region thickness. The thermal breakdown mechanism is analyzed. It is the spike leakage of the second sub-pulse that makes the temperature rise speed up. And the high temperature of the P-type region also causes the electrothermal feedback which makes it easier to get higher temperature.
2018,
30: 063003.
doi: 10.11884/HPLPB201830.170462
Abstract:
The design methodologies, numerical results for TE01 circular waveguide mode transducer were reported. It is shown that, TE01 circular waveguide mode can realize high transmission efficiency in a wide band by utilizing travelling wave power divide structures, realizing TE10 rectangular waveguide mode divided into four TE10 rectangular waveguide modes, and then combining to a TE01 circular waveguide mode. The optimized transducer has a transmission efficiency of over 99.9% at 9.40 GHz, and exceeds 99.0% in the range of 9.08-9.61 GHz. Experimental results show that the transmission loss is less than -0.2 dB, which is mainly caused by waveguide ohmic loss and waveguide-coaxial adapter. However, the results also have verified the feasibility of the manufactured transducer.
The design methodologies, numerical results for TE01 circular waveguide mode transducer were reported. It is shown that, TE01 circular waveguide mode can realize high transmission efficiency in a wide band by utilizing travelling wave power divide structures, realizing TE10 rectangular waveguide mode divided into four TE10 rectangular waveguide modes, and then combining to a TE01 circular waveguide mode. The optimized transducer has a transmission efficiency of over 99.9% at 9.40 GHz, and exceeds 99.0% in the range of 9.08-9.61 GHz. Experimental results show that the transmission loss is less than -0.2 dB, which is mainly caused by waveguide ohmic loss and waveguide-coaxial adapter. However, the results also have verified the feasibility of the manufactured transducer.
2018,
30: 063004.
doi: 10.11884/HPLPB201830.170405
Abstract:
In order to solve the problem that the traditional directional coupler has a narrow bandwidth and is greatly influenced by harmonic signals, this paper presents a broadband directional coupler with the function of harmonic suppression. The directional coupler adds a branch section to double-branch-line directional coupler, thus can effectively improve the bandwidth. While its transmission lines are added with low-pass filter structures, it can filter harmonics well. The experimental results show that the directional coupler reflection coefficient and isolation are less than -15 dB, the transmission loss is more than -3.8 dB, the fluctuation range is 0.5 dB and the phase difference is 90°. It satisfies the design requirement of coupler, and can be applied to microwave components to improve the performance.
In order to solve the problem that the traditional directional coupler has a narrow bandwidth and is greatly influenced by harmonic signals, this paper presents a broadband directional coupler with the function of harmonic suppression. The directional coupler adds a branch section to double-branch-line directional coupler, thus can effectively improve the bandwidth. While its transmission lines are added with low-pass filter structures, it can filter harmonics well. The experimental results show that the directional coupler reflection coefficient and isolation are less than -15 dB, the transmission loss is more than -3.8 dB, the fluctuation range is 0.5 dB and the phase difference is 90°. It satisfies the design requirement of coupler, and can be applied to microwave components to improve the performance.
2018,
30: 063005.
doi: 10.11884/HPLPB201830.170431
Abstract:
In this paper, a novel high current diode with multipacting cathode is studied and verified by using simplified dynamic theory and Monte Carlo simulation. Firstly, based on the design-prototype and the emission characteristics of secondary electron, the dynamic model is established, the expressions of electron velocity, displacement and transit time are obtained from the simplified dynamic equations. The multipacting cathode's working range (multipacting susceptibility) is obtained, by using dynamic theory and Vaughan's SEY (Secondary Electron Yield) model. Secondly, the importance of the applied electric field in radial direction is discussed, and the characteristics parameters of moving secondary electrons are analyzed theoretically, such as maximum displacement, transit time, and impact energy. Finally, the novel high current diode with multipacting cathode is investigated by using Monte Carlo simulation in detail. The physical images of secondary electron's trajectory, impact energy and the multipacting working range diagram are analyzed and discussed. The theoretical results are verified by Monte Carlo simulation and they agree with the theoretical results. The possible reason of the error between theoretical and simulated results is discussed. Both theoretical and numerical results demonstrate that the concept of the novel high current diode is feasible, by adjusting the magnitude of the applied electric field and magnetic field, the moving status of secondary electrons could be controlled effectively. Under the condition of multipactor saturation, the roughly theoretical estimation indicates that the novel multipacting cathode has the performance of high emission current density, and the emission current density can run up to the level of ~kA/cm2. Enhancing the magnitude of applied electrostatic field in radial direction can effectively improve the emission current density. In addition, the design procedure of the multipacting cathode is introduced and discussed in detail.
In this paper, a novel high current diode with multipacting cathode is studied and verified by using simplified dynamic theory and Monte Carlo simulation. Firstly, based on the design-prototype and the emission characteristics of secondary electron, the dynamic model is established, the expressions of electron velocity, displacement and transit time are obtained from the simplified dynamic equations. The multipacting cathode's working range (multipacting susceptibility) is obtained, by using dynamic theory and Vaughan's SEY (Secondary Electron Yield) model. Secondly, the importance of the applied electric field in radial direction is discussed, and the characteristics parameters of moving secondary electrons are analyzed theoretically, such as maximum displacement, transit time, and impact energy. Finally, the novel high current diode with multipacting cathode is investigated by using Monte Carlo simulation in detail. The physical images of secondary electron's trajectory, impact energy and the multipacting working range diagram are analyzed and discussed. The theoretical results are verified by Monte Carlo simulation and they agree with the theoretical results. The possible reason of the error between theoretical and simulated results is discussed. Both theoretical and numerical results demonstrate that the concept of the novel high current diode is feasible, by adjusting the magnitude of the applied electric field and magnetic field, the moving status of secondary electrons could be controlled effectively. Under the condition of multipactor saturation, the roughly theoretical estimation indicates that the novel multipacting cathode has the performance of high emission current density, and the emission current density can run up to the level of ~kA/cm2. Enhancing the magnitude of applied electrostatic field in radial direction can effectively improve the emission current density. In addition, the design procedure of the multipacting cathode is introduced and discussed in detail.
2018,
30: 063006.
doi: 10.11884/HPLPB201830.170455
Abstract:
Power meters, oscilloscopes, detectors, and vector network analyzers are commonly used in microwave measurements. The introduced errors by these instruments have direct impact on the measurement accuracy. In this paper, the measurement methods of power meters, oscilloscopes, detectors, and network analyzers are described, based on which the introduced errors by the typical measurement instruments under different measurement conditions are analyzed. The experiment results demonstrate that the measured power by the detectors is at most 0.4 dB bigger than that by the oscilloscope. The maximum difference of the measured power by the oscilloscope under different suppression bandwidths is 0.3 dB. The measured power by the vector network analyzer N9917A is 1 dB bigger than that by the analyzer AV3672 at 4 GHz with the attenuation of 60 dB.
Power meters, oscilloscopes, detectors, and vector network analyzers are commonly used in microwave measurements. The introduced errors by these instruments have direct impact on the measurement accuracy. In this paper, the measurement methods of power meters, oscilloscopes, detectors, and network analyzers are described, based on which the introduced errors by the typical measurement instruments under different measurement conditions are analyzed. The experiment results demonstrate that the measured power by the detectors is at most 0.4 dB bigger than that by the oscilloscope. The maximum difference of the measured power by the oscilloscope under different suppression bandwidths is 0.3 dB. The measured power by the vector network analyzer N9917A is 1 dB bigger than that by the analyzer AV3672 at 4 GHz with the attenuation of 60 dB.
2018,
30: 063007.
doi: 10.11884/HPLPB201830.170468
Abstract:
In order to explore the miniaturized relativistic klystron amplifier(RKA), we develop the theoretical analysis and simulation on the periodic permanent magnet (PPM) of the coaxial RKA. The Halbach arrays are applied to this PPM system and generate periodic cusped magnetic field. We evaluate the radial and axial components of the PPM field and present the characteristics of the magnetic distribution. Based on our expressions of the magnetic distribution, we get the transmission stability condition of the annular IREB in the PPM system for the coaxial waveguide. According to the stability condition, we design and optimize a PPM system for a Ka band coaxial RKA. Then the optimized period and amplitude of the PPM system are obtained. The results of the research show that the PPM system can focus the electron beam with voltage of 500 kV and current of 6 kA in the Ka band coaxial RKA, while the period and amplitude of the PPM system are 18 mm, 0.33 T, respectively. In addition, the coaxial RKA can stably generate millimeter wave with power of 1 GW. In a word, it is possible that the PPM system can be applied to the high power coaxial RKA.
In order to explore the miniaturized relativistic klystron amplifier(RKA), we develop the theoretical analysis and simulation on the periodic permanent magnet (PPM) of the coaxial RKA. The Halbach arrays are applied to this PPM system and generate periodic cusped magnetic field. We evaluate the radial and axial components of the PPM field and present the characteristics of the magnetic distribution. Based on our expressions of the magnetic distribution, we get the transmission stability condition of the annular IREB in the PPM system for the coaxial waveguide. According to the stability condition, we design and optimize a PPM system for a Ka band coaxial RKA. Then the optimized period and amplitude of the PPM system are obtained. The results of the research show that the PPM system can focus the electron beam with voltage of 500 kV and current of 6 kA in the Ka band coaxial RKA, while the period and amplitude of the PPM system are 18 mm, 0.33 T, respectively. In addition, the coaxial RKA can stably generate millimeter wave with power of 1 GW. In a word, it is possible that the PPM system can be applied to the high power coaxial RKA.
2018,
30: 063008.
doi: 10.11884/HPLPB201830.170461
Abstract:
In order to detect microwave pulse parameters at aerial target areas (tens of meters to hundreds of kilometers)of a certain type high power microwave radiation system, a data acquisition system whose structure is simple and compact for high power microwave remote measurement is designed base on wireless remote data transmission link of aerial flying platform. The system can display running state dynamically, set measuring parameter remotely and display waveform in real time. What's more, the weight of the system is less than 2 kg and the dynamic range of the system is more than 15 dB. Our experiments show that the system can measure high repetition frequency microwave radiation field. It meets the requirement of aerial microwave radiation field measurement at hundreds of kilometers distance. It also lays the foundation for the design of microwave radiation field measurement systems at higher and farther distance in the future.
In order to detect microwave pulse parameters at aerial target areas (tens of meters to hundreds of kilometers)of a certain type high power microwave radiation system, a data acquisition system whose structure is simple and compact for high power microwave remote measurement is designed base on wireless remote data transmission link of aerial flying platform. The system can display running state dynamically, set measuring parameter remotely and display waveform in real time. What's more, the weight of the system is less than 2 kg and the dynamic range of the system is more than 15 dB. Our experiments show that the system can measure high repetition frequency microwave radiation field. It meets the requirement of aerial microwave radiation field measurement at hundreds of kilometers distance. It also lays the foundation for the design of microwave radiation field measurement systems at higher and farther distance in the future.
2018,
30: 063009.
doi: 10.11884/HPLPB201830.170458
Abstract:
Charging power supply based on AC-link has the advantage of high power density and can be used for primary energy source of high-power microwave (HPM) system. In order to meet the requirement of high power density, a three-phase AC/AC converter based on AC-link parallel resonance is studied. Topological structure and operating principle of the converter is analyzed, the specific working process of 16 modes and the realization of soft-switching are described and the algorithm of switches on time is given. A 15 kW simulation platform is built and energy conversion processes under different loads are analyzed. The result shows that the conversion of voltage and frequency is realized, currents of both sides are sinusoidal, also, unity input power factor and zero voltage switching(ZVS) are realized.
Charging power supply based on AC-link has the advantage of high power density and can be used for primary energy source of high-power microwave (HPM) system. In order to meet the requirement of high power density, a three-phase AC/AC converter based on AC-link parallel resonance is studied. Topological structure and operating principle of the converter is analyzed, the specific working process of 16 modes and the realization of soft-switching are described and the algorithm of switches on time is given. A 15 kW simulation platform is built and energy conversion processes under different loads are analyzed. The result shows that the conversion of voltage and frequency is realized, currents of both sides are sinusoidal, also, unity input power factor and zero voltage switching(ZVS) are realized.
2018,
30: 063010.
doi: 10.11884/HPLPB201830.170310
Abstract:
Aiming at improving the effectiveness of the experimental multipactor tests, three different methods of electron seeding based on radioactive sources, ultra violet light sources and electron gun are investigated. Advantages and application range of these methods are introduced and compared. Then, two radioactive sources, β decay and γ transition, are particularly discussed, and their characteristics of electron seeding are quantitatively analyzed. The obtained result shows that both methods can be used to generate seeding electrons that can penetrate millimeter-level aluminum walls of microwave devices, suitable for electron seedings in high-power multipactor tests for microwave components.
Aiming at improving the effectiveness of the experimental multipactor tests, three different methods of electron seeding based on radioactive sources, ultra violet light sources and electron gun are investigated. Advantages and application range of these methods are introduced and compared. Then, two radioactive sources, β decay and γ transition, are particularly discussed, and their characteristics of electron seeding are quantitatively analyzed. The obtained result shows that both methods can be used to generate seeding electrons that can penetrate millimeter-level aluminum walls of microwave devices, suitable for electron seedings in high-power multipactor tests for microwave components.
2018,
30: 063101.
doi: 10.11884/HPLPB201830.180015
Abstract:
A new kind of THz hybrid metal-plasma Yagi antenna has been proposed on the basis of plasma antenna to meet the requirements of good directivity and high gain, in which reflection oscillator is replaced by right-angle reflector. The structure is designed by the theory of plasma antenna and Yagi antenna, and the parameters are preliminarily determined. Then electromagnetic simulation is carried out to examine the performance parameters of the Yagi antenna, such as the return loss, gain, voltage standing wave ratio and radiation pattern, in which the condition of different distances between the vertex of angle reflector and dipole is considered. Contrasted with the antennas without angle reflector, the structure proposed in this article has much higher gain and better front-to-rear ratio.
A new kind of THz hybrid metal-plasma Yagi antenna has been proposed on the basis of plasma antenna to meet the requirements of good directivity and high gain, in which reflection oscillator is replaced by right-angle reflector. The structure is designed by the theory of plasma antenna and Yagi antenna, and the parameters are preliminarily determined. Then electromagnetic simulation is carried out to examine the performance parameters of the Yagi antenna, such as the return loss, gain, voltage standing wave ratio and radiation pattern, in which the condition of different distances between the vertex of angle reflector and dipole is considered. Contrasted with the antennas without angle reflector, the structure proposed in this article has much higher gain and better front-to-rear ratio.
2018,
30: 063201.
doi: 10.11884/HPLPB201830.170479
Abstract:
Based on the polarization decomposition theory, the scattering field of the bar of the metal space frame is analyzed. The mechanical strength and scattering characteristics of the cylindrical bar and the rectangular bar are compared. Considering the advantages and disadvantages of the round bars and the rectangle bars, the optimal design of bars with rounded rectangular section is put forward. The radiation effect are simulated and analyzed. The results show that the rectangle bar has higher sidelobe level than the round bar due to the accumulation of electric charge on its edge, but performs better in resistance of bending. The rounded rectangle bar is a feasible scheme for improving both the mechanics and electromagnetics performance of the radome because of lower scattering intensity and higher mechanical strength.
Based on the polarization decomposition theory, the scattering field of the bar of the metal space frame is analyzed. The mechanical strength and scattering characteristics of the cylindrical bar and the rectangular bar are compared. Considering the advantages and disadvantages of the round bars and the rectangle bars, the optimal design of bars with rounded rectangular section is put forward. The radiation effect are simulated and analyzed. The results show that the rectangle bar has higher sidelobe level than the round bar due to the accumulation of electric charge on its edge, but performs better in resistance of bending. The rounded rectangle bar is a feasible scheme for improving both the mechanics and electromagnetics performance of the radome because of lower scattering intensity and higher mechanical strength.
2018,
30: 063202.
doi: 10.11884/HPLPB201830.170365
Abstract:
Aiming at the develop requirement of the radar EW(electronic warfare) simulation under the complex electromagnetic environment, the method of radar EW composable simulation was brought up. This paper expounds the basic theory of composable simulation, analyzes the development model of component-based composable simulation, and studies the implementation technology from four aspects of simulation—component development, testing, management and assembly. The supporting tools for component-based simulation of radar EW were designed and realized, which could be used to reduce the difficulty of composable simulation development and improve the automation degree of composable simulation.
Aiming at the develop requirement of the radar EW(electronic warfare) simulation under the complex electromagnetic environment, the method of radar EW composable simulation was brought up. This paper expounds the basic theory of composable simulation, analyzes the development model of component-based composable simulation, and studies the implementation technology from four aspects of simulation—component development, testing, management and assembly. The supporting tools for component-based simulation of radar EW were designed and realized, which could be used to reduce the difficulty of composable simulation development and improve the automation degree of composable simulation.
2018,
30: 064001.
doi: 10.11884/HPLPB201830.170414
Abstract:
Energy loss and scattering angle of penetrating protons are main sources of image blur for proton radiography (PRAD). PRAD relying on Zumbro lens can basically eliminate the image blur caused by scattering angle and achieve spatial resolution of several tens microns. However, the chromatic blur resulted from energy loss cannot be optimized, and it is the major cause for limiting spatial resolution. To eliminate the influence of energy loss and make a further improvement of spatial resolution, a new type of magnetic lens is proposed, called energy-loss focused imaging lens. A 11 MeV low-energy energy-loss imaging beamline is designed and a numerical model is built for energy-loss PRAD by using GEANT4 to study its image ability in simulation. The simulation results show that the 11 MeV low-energy energy-loss PRAD can achieve about 30 μm spatial resolution for 10 μm Al target. Compared with Zumbro lens of the same size, the spatial resolution is improved obviously.
Energy loss and scattering angle of penetrating protons are main sources of image blur for proton radiography (PRAD). PRAD relying on Zumbro lens can basically eliminate the image blur caused by scattering angle and achieve spatial resolution of several tens microns. However, the chromatic blur resulted from energy loss cannot be optimized, and it is the major cause for limiting spatial resolution. To eliminate the influence of energy loss and make a further improvement of spatial resolution, a new type of magnetic lens is proposed, called energy-loss focused imaging lens. A 11 MeV low-energy energy-loss imaging beamline is designed and a numerical model is built for energy-loss PRAD by using GEANT4 to study its image ability in simulation. The simulation results show that the 11 MeV low-energy energy-loss PRAD can achieve about 30 μm spatial resolution for 10 μm Al target. Compared with Zumbro lens of the same size, the spatial resolution is improved obviously.
2018,
30: 064002.
doi: 10.11884/HPLPB201830.170498
Abstract:
Using the technique of Particle-In-Cell to simulate the secondary electron effect of proton beams bombarding the target surface, we obtained the results of the quality of proton beams and the quantity of secondary electrons affected by the extracted voltage. From which, we find that the width of proton beams' waist is 1.8 mm at 50 kV and 1.2 mm at 150 kV. Therefore, the proton beams become dispersed at lower voltages and compact at higher voltages. Adjusting the extracted voltage between acceleration areas, we can control the quality of proton beams.
Using the technique of Particle-In-Cell to simulate the secondary electron effect of proton beams bombarding the target surface, we obtained the results of the quality of proton beams and the quantity of secondary electrons affected by the extracted voltage. From which, we find that the width of proton beams' waist is 1.8 mm at 50 kV and 1.2 mm at 150 kV. Therefore, the proton beams become dispersed at lower voltages and compact at higher voltages. Adjusting the extracted voltage between acceleration areas, we can control the quality of proton beams.
2018,
30: 064101.
doi: 10.11884/HPLPB201830.180006
Abstract:
Aiming at the phenomenon that left transmission zero of bulk acoustic wave(BAW) filter has a leftward deviation in combined acoustic-electromagnetic simulation, we verified the existence of common inductance effect in simulation and analyzed the influence of common ground inductance on filter performance. We changed positions of parallel thin-film bulk acoustic resonators(FBARs) P1 and P4 to ground in the original layout of the BAW filter(shortening paths to the ground), respectively. Then combined acoustic-electromagnetic simulation of filter was done. The results show that: common ground inductance effect existed between parallel FBAR to ground and input port and output port in combined acoustic-electromagnetic simulation. When the paths of parallel FBARs to ground were shortened, the common ground inductance effect was reduced in combined acoustic-electromagnetic simulation, and out of band rejection was better. The influence of common ground inductance effect on the smaller area parallel FBAR was more obvious. So the influence of common inductance effect on left transmission zero and left out of band rejection should be considered in combined acoustic-electromagnetic simulation of BAW filter.
Aiming at the phenomenon that left transmission zero of bulk acoustic wave(BAW) filter has a leftward deviation in combined acoustic-electromagnetic simulation, we verified the existence of common inductance effect in simulation and analyzed the influence of common ground inductance on filter performance. We changed positions of parallel thin-film bulk acoustic resonators(FBARs) P1 and P4 to ground in the original layout of the BAW filter(shortening paths to the ground), respectively. Then combined acoustic-electromagnetic simulation of filter was done. The results show that: common ground inductance effect existed between parallel FBAR to ground and input port and output port in combined acoustic-electromagnetic simulation. When the paths of parallel FBARs to ground were shortened, the common ground inductance effect was reduced in combined acoustic-electromagnetic simulation, and out of band rejection was better. The influence of common ground inductance effect on the smaller area parallel FBAR was more obvious. So the influence of common inductance effect on left transmission zero and left out of band rejection should be considered in combined acoustic-electromagnetic simulation of BAW filter.
2018,
30: 065001.
doi: 10.11884/HPLPB201830.170516
Abstract:
As the key components of all solid-state pulse sources, semiconductor opening switches have the advantages of high frequency, long life, fast interruption, and large power capacity. The pre-pulse in output pulse voltage of semiconductor opening switches seriously affects the pulse rise time and the repetition frequency of the system. In this paper, the mechanism of the pre-pulse during the reverse interruption process is studied. The evolution process of the carriers and the electric field during the forward and reverse pumping processes of the semiconductor opening switches are investigated by using the simulation software Silvaco-Atlas. It is found that the pre-pulse is caused by the N-N+ junction interruption in the bilateral interruption process. The length of pre-pulse depends mainly on the mobility of minorities in the P-type region, and the slope of the pulse depends on the PN interruption process. Meanwhile, the devices with different base region lengths and different pumping conditions have been simulated and compared. It is found that the device base region is narrower, the pulse rises faster, and the pre-pulse is almost equal with each other. Under low current density conditions, only N-N+ junction interruption occurs; under high current density, bilateral interruption occurs. The delay of bilateral interruption is longer, but the pulse rises faster.
As the key components of all solid-state pulse sources, semiconductor opening switches have the advantages of high frequency, long life, fast interruption, and large power capacity. The pre-pulse in output pulse voltage of semiconductor opening switches seriously affects the pulse rise time and the repetition frequency of the system. In this paper, the mechanism of the pre-pulse during the reverse interruption process is studied. The evolution process of the carriers and the electric field during the forward and reverse pumping processes of the semiconductor opening switches are investigated by using the simulation software Silvaco-Atlas. It is found that the pre-pulse is caused by the N-N+ junction interruption in the bilateral interruption process. The length of pre-pulse depends mainly on the mobility of minorities in the P-type region, and the slope of the pulse depends on the PN interruption process. Meanwhile, the devices with different base region lengths and different pumping conditions have been simulated and compared. It is found that the device base region is narrower, the pulse rises faster, and the pre-pulse is almost equal with each other. Under low current density conditions, only N-N+ junction interruption occurs; under high current density, bilateral interruption occurs. The delay of bilateral interruption is longer, but the pulse rises faster.
2018,
30: 065002.
doi: 10.11884/HPLPB201830.170306
Abstract:
In magnetically driven experiments, such as solid liner implosion, magnetically driven flyer plate emission and magnetically driven quasi-isentropic/impulse compression, the metal starts from a solid phase and gradually turns into liquid phase by ohmic heating. In order to study the effects of material hardness the solid phase has on those magnetically driven experiments, we have added an elastoplasticitic module to the two-dimensional magnetically driven simulation code (MDSC2). With this code, we carried out numerical simulations of the development of Rayleigh-Taylor (RT) instability in magnetically driven solid liner implosion. The numerical results show that while the elastoplasticitic term has little effect on the trajectories of the inner and outer radius of the solid liner without an initial disturbance, it suppresses significantly the RT instability growth of the magnetically driven solid liner with an initial disturbance.
In magnetically driven experiments, such as solid liner implosion, magnetically driven flyer plate emission and magnetically driven quasi-isentropic/impulse compression, the metal starts from a solid phase and gradually turns into liquid phase by ohmic heating. In order to study the effects of material hardness the solid phase has on those magnetically driven experiments, we have added an elastoplasticitic module to the two-dimensional magnetically driven simulation code (MDSC2). With this code, we carried out numerical simulations of the development of Rayleigh-Taylor (RT) instability in magnetically driven solid liner implosion. The numerical results show that while the elastoplasticitic term has little effect on the trajectories of the inner and outer radius of the solid liner without an initial disturbance, it suppresses significantly the RT instability growth of the magnetically driven solid liner with an initial disturbance.
2018,
30: 065003.
doi: 10.11884/HPLPB201830.170335
Abstract:
Based on the need of high power repetitive pulse power source, the repetitive frequency characteristics of high power pulse charging power supply are studied in this paper. The constant current charging technology based on the full bridge series resonant charging principle is analyzed. According to the work requirement of high power Marx type pulse power source, the key parameters of the series resonant charging are calculated. The compact high power pulse charging power supply, with the maximum output voltage ±50 kV, the charging current 2.5 A and the repetition frequency 1-50 Hz, can run stably for a long time under the condition of repetition frequency. The charging power supply has the advantages of small volume, light weight, strong anti-interference ability and strong resistance to short circuit, and has been applied to the research of high power repetitive pulse power source technology, in which it has achieved 100 000 times repetition-frequency operation without fault.
Based on the need of high power repetitive pulse power source, the repetitive frequency characteristics of high power pulse charging power supply are studied in this paper. The constant current charging technology based on the full bridge series resonant charging principle is analyzed. According to the work requirement of high power Marx type pulse power source, the key parameters of the series resonant charging are calculated. The compact high power pulse charging power supply, with the maximum output voltage ±50 kV, the charging current 2.5 A and the repetition frequency 1-50 Hz, can run stably for a long time under the condition of repetition frequency. The charging power supply has the advantages of small volume, light weight, strong anti-interference ability and strong resistance to short circuit, and has been applied to the research of high power repetitive pulse power source technology, in which it has achieved 100 000 times repetition-frequency operation without fault.
2018,
30: 065101.
doi: 10.11884/HPLPB201830.170214
Abstract:
Due to the small space and invisibility in MSE3, the alignment of MSE3 of separated sector cyclotron remains a longstanding challenging for the aligned personnel. Coupled with the compressed time, to quickly and accurately find MSE3's fault and realign its position is essential for the regular operation of the accelerator. This paper analyzes the principle of MSE3 and its transmission mechanisms, and establishes an effective model to standardize the drive motor. Furthermore, it develops a rapid realignment method based on multiple coordinate system transformation. The method can provide a basis for overhaul and alignment of similar component in related accelerators.
Due to the small space and invisibility in MSE3, the alignment of MSE3 of separated sector cyclotron remains a longstanding challenging for the aligned personnel. Coupled with the compressed time, to quickly and accurately find MSE3's fault and realign its position is essential for the regular operation of the accelerator. This paper analyzes the principle of MSE3 and its transmission mechanisms, and establishes an effective model to standardize the drive motor. Furthermore, it develops a rapid realignment method based on multiple coordinate system transformation. The method can provide a basis for overhaul and alignment of similar component in related accelerators.
2018,
30: 066001.
doi: 10.11884/HPLPB201830.170245
Abstract:
The research of Segmented Gamma Scanning(SGS) technique is mainly focused on two aspects: self-absorption correction of waste drum and efficiency calibration of the system. For the purpose of self-absorption correction, it is necessary to calculate the scanning efficiency. In this paper, a mathematical model was established for the correction, which was based on the spatial distribution of radioactive waste barrels, collimators and HPGe detectors in SGS detection systems. In addition, calculation of the detection efficiency of midpoint sources (Cs-137) in low and intermediate level radioactive waste steel drum was managed. Then the calculation corresponding to efficiency function based on MCNP method was operated as well. The results of the two methods were compared with the numerical calculations. It was found that the results from numerical calculation was usually larger than that from MCNP simulation and the maximum relative error reached 143.26% whereas the average error was 37.15%. After correction the maximum error was reduced down to 17.22% and the average value was 4.54%, which indicates that the model is scientific for the temporary storage, transportation and final disposal of the waste bucket.
The research of Segmented Gamma Scanning(SGS) technique is mainly focused on two aspects: self-absorption correction of waste drum and efficiency calibration of the system. For the purpose of self-absorption correction, it is necessary to calculate the scanning efficiency. In this paper, a mathematical model was established for the correction, which was based on the spatial distribution of radioactive waste barrels, collimators and HPGe detectors in SGS detection systems. In addition, calculation of the detection efficiency of midpoint sources (Cs-137) in low and intermediate level radioactive waste steel drum was managed. Then the calculation corresponding to efficiency function based on MCNP method was operated as well. The results of the two methods were compared with the numerical calculations. It was found that the results from numerical calculation was usually larger than that from MCNP simulation and the maximum relative error reached 143.26% whereas the average error was 37.15%. After correction the maximum error was reduced down to 17.22% and the average value was 4.54%, which indicates that the model is scientific for the temporary storage, transportation and final disposal of the waste bucket.
2018,
30: 066002.
doi: 10.11884/HPLPB201830.170382
Abstract:
The reactor oscillator method is a method for measuring small reactivity, its measurement precision is related to the selection of experimental conditions. In order to select the optimal conditions of experiment, several major factors which affect measurement accuracy are analyzed by numerical simulation and derivations of formulas. The research shows that the accuracy of reactivity measurement with reactor oscillator method can be improved by choosing suitable amplitude and frequency of reactivity oscillation. According to the analysis result, for the reactor which has short neutron generation time, we should choose high-frequency reactivity oscillation.
The reactor oscillator method is a method for measuring small reactivity, its measurement precision is related to the selection of experimental conditions. In order to select the optimal conditions of experiment, several major factors which affect measurement accuracy are analyzed by numerical simulation and derivations of formulas. The research shows that the accuracy of reactivity measurement with reactor oscillator method can be improved by choosing suitable amplitude and frequency of reactivity oscillation. According to the analysis result, for the reactor which has short neutron generation time, we should choose high-frequency reactivity oscillation.
2018,
30: 069001.
doi: 10.11884/HPLPB201830.170386
Abstract:
To describe morphological changes in the drilling hole and simulate the temperature distribution during nanosecond laser drilling, a physical model of titanium nanosecond-pulsed laser drilling was established and programmed using ANSYS Parametric Design Language (APDL). Elements birth and death technology was applied to simulate the drilling process in the finite element analysis software ANSYS. Experimental and simulation results were compared, and curve changes in the laser drilling results (hole depth and diameter) together with laser machining parameters (laser energy and pulse number) were obtained and investigated. Effects of process parameters on hole quality are analyzed and compared from finite element simulation and experiment to optimize process parameters and improve hole quality. The universal law of nano-second pulsed laser drilling on titanium alloy is discussed systematically.
To describe morphological changes in the drilling hole and simulate the temperature distribution during nanosecond laser drilling, a physical model of titanium nanosecond-pulsed laser drilling was established and programmed using ANSYS Parametric Design Language (APDL). Elements birth and death technology was applied to simulate the drilling process in the finite element analysis software ANSYS. Experimental and simulation results were compared, and curve changes in the laser drilling results (hole depth and diameter) together with laser machining parameters (laser energy and pulse number) were obtained and investigated. Effects of process parameters on hole quality are analyzed and compared from finite element simulation and experiment to optimize process parameters and improve hole quality. The universal law of nano-second pulsed laser drilling on titanium alloy is discussed systematically.
2018,
30: 069002.
doi: 10.11884/HPLPB201830.170480
Abstract:
The vortex wave flow field of symmetric channel has a wide range of applications in industrial mass transfer and heat transfer. To further analyze the flow characteristics and variation laws of the vortex wave flow field within symmetric channel under laminar flow conditions, 2D PIV measurements was carried out to obtain data of instantaneous flow velocity vector field, then modes were decomposed and vortex wave flow field reconstructed using proper orthogonal decomposition(POD) technology. According to the reconstruction of the flow field, analysis were carried out for mean velocity profile, pulsation intensity of flow field, velocity and spectral distribution of the characteristics points, etc. of the vortex wave flow field within the symmetrical channel. The results show that the first 15 POD modes could characterize the dominant vortex wave flow field structure, the first and the third modes were a pair of vortices with opposite rotating, while the second mode had a vortex and the wavy mainstream feature. Five vortex core positions were extracted as the flow field feature points. Analysis based on POD reconstructed stream field. Analysis shows that the average speed distribution in the flow direction is parabolic, and the normal average speed distribution is symmetrical; flow pulsation intensity is greatly influenced by the wall, the normal fluctuation intensity distribution exhibits a parabolic shape; the speed pulsation features of feature points 1#, 4#, 5#(closer to the center mainstream) are influenced by mainstream pulsation strength, the velocity distribution of feature points is affected by pulsation speed frequency of 0.15 Hz frequency and the natural frequency of the flow field 0.35 Hz together; the flow velocity of feature points 2#, 3# has a fading trend, the normal speed variation amplitude is large in the early stage.
The vortex wave flow field of symmetric channel has a wide range of applications in industrial mass transfer and heat transfer. To further analyze the flow characteristics and variation laws of the vortex wave flow field within symmetric channel under laminar flow conditions, 2D PIV measurements was carried out to obtain data of instantaneous flow velocity vector field, then modes were decomposed and vortex wave flow field reconstructed using proper orthogonal decomposition(POD) technology. According to the reconstruction of the flow field, analysis were carried out for mean velocity profile, pulsation intensity of flow field, velocity and spectral distribution of the characteristics points, etc. of the vortex wave flow field within the symmetrical channel. The results show that the first 15 POD modes could characterize the dominant vortex wave flow field structure, the first and the third modes were a pair of vortices with opposite rotating, while the second mode had a vortex and the wavy mainstream feature. Five vortex core positions were extracted as the flow field feature points. Analysis based on POD reconstructed stream field. Analysis shows that the average speed distribution in the flow direction is parabolic, and the normal average speed distribution is symmetrical; flow pulsation intensity is greatly influenced by the wall, the normal fluctuation intensity distribution exhibits a parabolic shape; the speed pulsation features of feature points 1#, 4#, 5#(closer to the center mainstream) are influenced by mainstream pulsation strength, the velocity distribution of feature points is affected by pulsation speed frequency of 0.15 Hz frequency and the natural frequency of the flow field 0.35 Hz together; the flow velocity of feature points 2#, 3# has a fading trend, the normal speed variation amplitude is large in the early stage.
2018,
30: 060000.
