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RSS2020 Vol. 32, No. 3
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2020,
32: 1-2.
2020,
32: 032001.
doi: 10.11884/HPLPB202032.200039
Abstract:
The main goal of inertial confinement fusion (ICF) research is to realize that the energy released by fusion reaction is greater than the threshold value of ignition fusion reaction in the laboratory. A series of key physical problems must be explored deeply for the purpose. In ICF, the capability of target fabrication is particularly important, and the quality of target is the pivotal element of physical experiment. This paper expounds the progress of ICF target preparation in recent years, such as capsule of new ablation material, new technology of capsule support, new material and shape of hohlraums, and reduction of filler tube dimensions. Combining with the physical requirements of ICF, it introduces the development trend of ICF target briefly.
The main goal of inertial confinement fusion (ICF) research is to realize that the energy released by fusion reaction is greater than the threshold value of ignition fusion reaction in the laboratory. A series of key physical problems must be explored deeply for the purpose. In ICF, the capability of target fabrication is particularly important, and the quality of target is the pivotal element of physical experiment. This paper expounds the progress of ICF target preparation in recent years, such as capsule of new ablation material, new technology of capsule support, new material and shape of hohlraums, and reduction of filler tube dimensions. Combining with the physical requirements of ICF, it introduces the development trend of ICF target briefly.
2020,
32: 032002.
doi: 10.11884/HPLPB202032.190399
Abstract:
Various manufacturing defects would be introduced in traditional processing of ultraviolet fused silica components, which need to be eliminated by post-processing technique. Because of the defects, the processing efficiency and surface quality cannot meet the requirements. To solve these problems, the research group proposed controllable compliant techniques including magnetorheological finishing, ion beam figuring, conformal smoothing and hydrodynamic polishing to improve processing effect of fused silica components, and carried out related research. This paper mainly introduces the important progress made by the research group on key technologies, including sub-nanometer precision surface controlled manufacturing technology, nano-precision intrinsic surface property controlled manufacturing method, high-precision and low-defect combination process, equipment of fused silica component. Discussing key technologies and their development status, it provides references for the development of high precision and few defects manufacturing technology of ultraviolet fused silica components in the future.
Various manufacturing defects would be introduced in traditional processing of ultraviolet fused silica components, which need to be eliminated by post-processing technique. Because of the defects, the processing efficiency and surface quality cannot meet the requirements. To solve these problems, the research group proposed controllable compliant techniques including magnetorheological finishing, ion beam figuring, conformal smoothing and hydrodynamic polishing to improve processing effect of fused silica components, and carried out related research. This paper mainly introduces the important progress made by the research group on key technologies, including sub-nanometer precision surface controlled manufacturing technology, nano-precision intrinsic surface property controlled manufacturing method, high-precision and low-defect combination process, equipment of fused silica component. Discussing key technologies and their development status, it provides references for the development of high precision and few defects manufacturing technology of ultraviolet fused silica components in the future.
2020,
32: 032003.
doi: 10.11884/HPLPB202032.190426
Abstract:
The liquid crystal phase modulators (LCPMs) have applications and prospects in fusion ignition, laser processing, optoelectronic countermeasure, laser radar, laser communication, laser protection and so on. However, owing to the limited laser damage resistance of the materials constituting the LCPMs as well as insufficient system research on the laser damage and the phase modulation performance degradation of LCPMs induced by high power lasers, the laser handling power of LCPMs cannot satisfy the requirements of high power laser developments. To provide guidance for optimizing the fabrication process of LCPMs with high laser handling power, we reviewed the laser damage and the phase modulation performance degradation characteristics of LCPMs irradiated by high-peak-power lasers and high-average-power-lasers and then summarized the methods to improve the laser handling power of LCPMs.
The liquid crystal phase modulators (LCPMs) have applications and prospects in fusion ignition, laser processing, optoelectronic countermeasure, laser radar, laser communication, laser protection and so on. However, owing to the limited laser damage resistance of the materials constituting the LCPMs as well as insufficient system research on the laser damage and the phase modulation performance degradation of LCPMs induced by high power lasers, the laser handling power of LCPMs cannot satisfy the requirements of high power laser developments. To provide guidance for optimizing the fabrication process of LCPMs with high laser handling power, we reviewed the laser damage and the phase modulation performance degradation characteristics of LCPMs irradiated by high-peak-power lasers and high-average-power-lasers and then summarized the methods to improve the laser handling power of LCPMs.
2020,
32: 032004.
doi: 10.11884/HPLPB202032.190447
Abstract:
Ultra-low density SiO2 aerogel as a classic three-dimensional network nano-porous material is widely used in many fields such as thermal insulation and adsorption. In this manuscript, tetramethoxysilane (TMOS) is used as the silicon source and an acid-base two-step method is used. Ultra-low density SiO2 aerogels were prepared by ethanol supercritical drying technology, and a series of studies were performed on the aerogels using SEM\TEM\BET and other characterization methods. When the aerogel density was 0.6 mg/cm3, it had the best comprehensive properties. In addition, this aerogel has the advantages of ultra-low density, high specific surface area, good formability, and short preparation cycle. Thus, it is expected to play a significant role as a frozen target in laser inertial confinement fusion experiments.
Ultra-low density SiO2 aerogel as a classic three-dimensional network nano-porous material is widely used in many fields such as thermal insulation and adsorption. In this manuscript, tetramethoxysilane (TMOS) is used as the silicon source and an acid-base two-step method is used. Ultra-low density SiO2 aerogels were prepared by ethanol supercritical drying technology, and a series of studies were performed on the aerogels using SEM\TEM\BET and other characterization methods. When the aerogel density was 0.6 mg/cm3, it had the best comprehensive properties. In addition, this aerogel has the advantages of ultra-low density, high specific surface area, good formability, and short preparation cycle. Thus, it is expected to play a significant role as a frozen target in laser inertial confinement fusion experiments.
2020,
32: 032005.
doi: 10.11884/HPLPB202032.190262
Abstract:
The influence of cutting parameters on the frequency characteristics of optical crystal surface has been studied. The experiment of single point diamond turning was adopted to process KDP crystal. The frequency distribution of surface profile was obtained by power spectral density. The continuous wavelet method was used to evaluate the influence of cutting depth, feed rate and spindle speed on machined surface. The results show that the frequency characteristics reflect the effects of cutting parameters on surface topography. The wavelength and amplitude of mid frequency embody the change of cutting depth and spindle speed, and the amplitude increases with the increase of cutting depth and speed. Low frequency reflects the change of feed rate, and the amplitude becomes small as feed rate decreases. High frequency is the manifestation of vibration and material anisotropy in processing. Therefore the analysis of frequency characteristics on surface topography provides a reference for selecting the optimal process parameters.
The influence of cutting parameters on the frequency characteristics of optical crystal surface has been studied. The experiment of single point diamond turning was adopted to process KDP crystal. The frequency distribution of surface profile was obtained by power spectral density. The continuous wavelet method was used to evaluate the influence of cutting depth, feed rate and spindle speed on machined surface. The results show that the frequency characteristics reflect the effects of cutting parameters on surface topography. The wavelength and amplitude of mid frequency embody the change of cutting depth and spindle speed, and the amplitude increases with the increase of cutting depth and speed. Low frequency reflects the change of feed rate, and the amplitude becomes small as feed rate decreases. High frequency is the manifestation of vibration and material anisotropy in processing. Therefore the analysis of frequency characteristics on surface topography provides a reference for selecting the optimal process parameters.
2020,
32: 031001.
doi: 10.11884/HPLPB202032.190303
Abstract:
A thermal damage analysis model of scratches and residual polishing particles on the optical surface is established. The thermal damage properties of optical materials under such complex defects are studied. The finite difference method was used to calculate the light field modulation and temperature field distribution of the optical material surface at different positions of the polished particles at different scales. According to the surface temperature distribution, the thermal damage threshold of the optical material under the corresponding conditions is achieved. The results show that in addition to the influence of the polishing particle radius on the material damage threshold, when the polishing particles are located at different positions in the scratch width direction, the thermal damage threshold of the material will also change significantly. Among them, the polishing particles in the center of the scratch have the strongest modulation on the light field, and are more likely to cause melting damage of the material.
A thermal damage analysis model of scratches and residual polishing particles on the optical surface is established. The thermal damage properties of optical materials under such complex defects are studied. The finite difference method was used to calculate the light field modulation and temperature field distribution of the optical material surface at different positions of the polished particles at different scales. According to the surface temperature distribution, the thermal damage threshold of the optical material under the corresponding conditions is achieved. The results show that in addition to the influence of the polishing particle radius on the material damage threshold, when the polishing particles are located at different positions in the scratch width direction, the thermal damage threshold of the material will also change significantly. Among them, the polishing particles in the center of the scratch have the strongest modulation on the light field, and are more likely to cause melting damage of the material.
2020,
32: 031002.
doi: 10.11884/HPLPB202032.190250
Abstract:
To solve the problem that the non-uniform distribution of extinction coefficients in the vertical direction of the atmosphere makes it difficult to directly measure the vertical visibility by traditional methods, this paper presents a method for calculating the vertical visibility based on lidar detection. Firstly, according to the basic principle of atmospheric radiation transmission and radiation transfer equation, it deduces the calculation formula of vertical visibility, which solves the problem that there is no specific formula for calculating vertical visibility. Secondly, it inverts the extinction coefficient distribution in the vertical direction of the atmosphere by using the lidar equation and Klett algorithm. On this basis, it proposes an iterative algorithm for vertical visibility. Finally, it uses the gray model GM(1,1) and batch statistics algorithm to evaluate the backscattering coefficient obtained by laser radar inversion, and gives the error confidence interval (0.760±0.339)×10−4(srad·km)−1. The results show that the method is a particularly effective one for calculating vertical visibility, which meets the basic requirements of detection, with small error and high precision.
To solve the problem that the non-uniform distribution of extinction coefficients in the vertical direction of the atmosphere makes it difficult to directly measure the vertical visibility by traditional methods, this paper presents a method for calculating the vertical visibility based on lidar detection. Firstly, according to the basic principle of atmospheric radiation transmission and radiation transfer equation, it deduces the calculation formula of vertical visibility, which solves the problem that there is no specific formula for calculating vertical visibility. Secondly, it inverts the extinction coefficient distribution in the vertical direction of the atmosphere by using the lidar equation and Klett algorithm. On this basis, it proposes an iterative algorithm for vertical visibility. Finally, it uses the gray model GM(1,1) and batch statistics algorithm to evaluate the backscattering coefficient obtained by laser radar inversion, and gives the error confidence interval (0.760±0.339)×10−4(srad·km)−1. The results show that the method is a particularly effective one for calculating vertical visibility, which meets the basic requirements of detection, with small error and high precision.
2020,
32: 031003.
doi: 10.11884/hplpb202032.190342
Abstract:
With the rapid development of high-power lasers and electronic technology, higher requirements have been proposed for the structure and material of the heat sink device. Based on the principle of conduction-insulation heat, alternating stack epoxy resin composites with excellent thermal protection were prepared, the hexagonal boron nitride (h-BN: 5%, 15%, 25%) and expanded vermiculite (E-ver: 1%) are used as fillers for heat dissipation layer and thermal insulation layer, respectively. The thermal protection performance experiment was completed. The result shows that the temperature of the top center is 13−16 °C lower than that of the traditional materials, and the thermal delay time is greatly improved. An increase in the h-BN content causes an increase in the thermal protection properties of the composites. The thermal mechanism of the anisotropic stacked composites was explained.
With the rapid development of high-power lasers and electronic technology, higher requirements have been proposed for the structure and material of the heat sink device. Based on the principle of conduction-insulation heat, alternating stack epoxy resin composites with excellent thermal protection were prepared, the hexagonal boron nitride (h-BN: 5%, 15%, 25%) and expanded vermiculite (E-ver: 1%) are used as fillers for heat dissipation layer and thermal insulation layer, respectively. The thermal protection performance experiment was completed. The result shows that the temperature of the top center is 13−16 °C lower than that of the traditional materials, and the thermal delay time is greatly improved. An increase in the h-BN content causes an increase in the thermal protection properties of the composites. The thermal mechanism of the anisotropic stacked composites was explained.
2020,
32: 033001.
doi: 10.11884/HPLPB202032.190199
Abstract:
To design size-reduced balanced bandpass filters (BPFs) with high selectivity, two new multilayer dual-mode substrate integrated waveguide (SIW) balanced BPFs are proposed. Firstly, the characteristic of dual-mode SIW cavity is analyzed in detail. Then, a balanced SIW BPF with balanced input/output (IO) ports locating on the upper dual-mode SIW cavity is proposed, and the lower dual-mode SIW cavity is coupled to the upper one using two crossed slots. Three transmission zeros (TZs) can be produced at any locations. A balanced SIW BPF with balanced IO ports locating on the upper and lower dual-mode cavities respectively is also proposed, and the two cavities are coupled by a slot. Two symmetrical TZs can be produced. Based on the proposed structures, two filters with center frequency of 10 GHz are designed, fabricated and measured. The measured results agree well with the simulated ones, which indicates the feasibility of the proposed multilayer dual-mode SIW balanced BPFs with compact size and high selectivity.
To design size-reduced balanced bandpass filters (BPFs) with high selectivity, two new multilayer dual-mode substrate integrated waveguide (SIW) balanced BPFs are proposed. Firstly, the characteristic of dual-mode SIW cavity is analyzed in detail. Then, a balanced SIW BPF with balanced input/output (IO) ports locating on the upper dual-mode SIW cavity is proposed, and the lower dual-mode SIW cavity is coupled to the upper one using two crossed slots. Three transmission zeros (TZs) can be produced at any locations. A balanced SIW BPF with balanced IO ports locating on the upper and lower dual-mode cavities respectively is also proposed, and the two cavities are coupled by a slot. Two symmetrical TZs can be produced. Based on the proposed structures, two filters with center frequency of 10 GHz are designed, fabricated and measured. The measured results agree well with the simulated ones, which indicates the feasibility of the proposed multilayer dual-mode SIW balanced BPFs with compact size and high selectivity.
2020,
32: 033002.
doi: 10.11884/HPLPB201931.190351
Abstract:
To solve the problems of the existing HPM radiation field power density measurement system, such as many measurement links, system complexity and long cable which can’t adapt to complex electromagnetic environment measurement, a miniaturized and integrated power density measurement system of high-power microwave radiation field is developed. An antenna-coupler-adapter is used as the front receiver, the back end of the system is a coaxial signal processing unit, where the attenuation, power detection and electro-optical conversion are achieved in the shield box, hence, the system can be measured and monitored remotely. Meanwhile, modular calibration is applied in the system, which can effectively reduce the measurement uncertainty. The system has 30 dB dynamics, a minimum measurable pulse width of 50 ns and a measurable radiation field power density of 100 MW/m2. It is compact, easy to carry, anti-electromagnetic radiation, and capable of quick power density measurement of GW high-power microwave radiation field in X-band.
To solve the problems of the existing HPM radiation field power density measurement system, such as many measurement links, system complexity and long cable which can’t adapt to complex electromagnetic environment measurement, a miniaturized and integrated power density measurement system of high-power microwave radiation field is developed. An antenna-coupler-adapter is used as the front receiver, the back end of the system is a coaxial signal processing unit, where the attenuation, power detection and electro-optical conversion are achieved in the shield box, hence, the system can be measured and monitored remotely. Meanwhile, modular calibration is applied in the system, which can effectively reduce the measurement uncertainty. The system has 30 dB dynamics, a minimum measurable pulse width of 50 ns and a measurable radiation field power density of 100 MW/m2. It is compact, easy to carry, anti-electromagnetic radiation, and capable of quick power density measurement of GW high-power microwave radiation field in X-band.
2020,
32: 033003.
doi: 10.11884/HPLPB202032.190318
Abstract:
The paper introduces a high-performance multifunctional apparatus for studying secondary electron emission characteristics of dielectric. The apparatus is equipped with a collector containing three grids and a 30 eV−30 keV electron gun, the secondary electron emission characteristics of dielectric can be measured under ultra-high vacuum, and in-situ XPS analysis spectrometer, heating and argon ion sputtering can also be performed. The paper also introduces the measurement of secondary electron yield by pulse method, gives the measured secondary electron current pulse of gold and Al2O3, presents the charging saturation time and influence of the thickness of dielectric on the charge amount obtained by judging the change of the current pulse waveform with time and the number of irradiations.
The paper introduces a high-performance multifunctional apparatus for studying secondary electron emission characteristics of dielectric. The apparatus is equipped with a collector containing three grids and a 30 eV−30 keV electron gun, the secondary electron emission characteristics of dielectric can be measured under ultra-high vacuum, and in-situ XPS analysis spectrometer, heating and argon ion sputtering can also be performed. The paper also introduces the measurement of secondary electron yield by pulse method, gives the measured secondary electron current pulse of gold and Al2O3, presents the charging saturation time and influence of the thickness of dielectric on the charge amount obtained by judging the change of the current pulse waveform with time and the number of irradiations.
2020,
32: 033101.
doi: 10.11884/HPLPB202032.190291
Abstract:
In this paper, the plasma electron density and collision frequency are calculated based on the flow field simulation of RAM C-III air vehicle, and an inhomogeneous plasma model is established according to the calculation results. The effects of plasma density, plasma thickness, plasma collision frequency and external magnetic field on the propagation characteristics of terahertz wave in plasma are analyzed using scattering matrix method. The results show that the propagation loss increases with plasma electron density and plasma thickness, while the transmittance decreases first and then increases with the increasing of collision frequency. When an external magnetic field is applied, the propagation characteristics of the left-handed polarized terahertz wave will be improved, while for the right-handed polarized terahertz wave, the application of magnetic field induces an absorption peak, which shifts to high frequency range with the increasing of magnetic induction intensity. This work may make a contribution to solving the problem of communication blackout.
In this paper, the plasma electron density and collision frequency are calculated based on the flow field simulation of RAM C-III air vehicle, and an inhomogeneous plasma model is established according to the calculation results. The effects of plasma density, plasma thickness, plasma collision frequency and external magnetic field on the propagation characteristics of terahertz wave in plasma are analyzed using scattering matrix method. The results show that the propagation loss increases with plasma electron density and plasma thickness, while the transmittance decreases first and then increases with the increasing of collision frequency. When an external magnetic field is applied, the propagation characteristics of the left-handed polarized terahertz wave will be improved, while for the right-handed polarized terahertz wave, the application of magnetic field induces an absorption peak, which shifts to high frequency range with the increasing of magnetic induction intensity. This work may make a contribution to solving the problem of communication blackout.
2020,
32: 033102.
doi: 10.11884/HPLPB202032.190302
Abstract:
This paper studies the interaction effect between the micro-structure photoconductive antenna (PCA) and femtosecond laser, the control of radiated terahertz (THz) wave, and the radiation regulation mechanism of the THz wave for the photoconductive antenna (PCA). The Drude-Lorentz theory model is used to solve the photocurrent density, which is then iterated to the excitation grid by FDTD method. And then the time-varying electromagnetic fields is solved by Maxwell’s equations. The radiated THz wave from the near field to far field in the multi-layer medium is got through the Green's Function of transmission line, and the relationship between the photocurrent and impedance of the radiation is established. At the same time, the relationship between the photocurrent and the magnetic resonance model is also established. The control mechanism of THz wave radiation from micro-structure S-shaped PCA is analyzed by simulation. The results show that the radiation impedance of the equivalent model is changed after split ring resonator (SRR) is introduced into the H-shaped PCA. Meanwhile, it is known that the coupling effect exists when the coupling coefficient is not zero. With the increasing of the coupling coefficient, and the radiation intensity of the resonance frequency peak increases and shifts. The adjusting range of the center frequency between 0.50−0.80 THz, the frequency modulation degree is 75%, and the peak radiation efficiency increases by 70% after simulating the S-shaped PCA. This work lays an important foundation for the design of THz wave resonance center frequency range and structure of high-power PCA.
This paper studies the interaction effect between the micro-structure photoconductive antenna (PCA) and femtosecond laser, the control of radiated terahertz (THz) wave, and the radiation regulation mechanism of the THz wave for the photoconductive antenna (PCA). The Drude-Lorentz theory model is used to solve the photocurrent density, which is then iterated to the excitation grid by FDTD method. And then the time-varying electromagnetic fields is solved by Maxwell’s equations. The radiated THz wave from the near field to far field in the multi-layer medium is got through the Green's Function of transmission line, and the relationship between the photocurrent and impedance of the radiation is established. At the same time, the relationship between the photocurrent and the magnetic resonance model is also established. The control mechanism of THz wave radiation from micro-structure S-shaped PCA is analyzed by simulation. The results show that the radiation impedance of the equivalent model is changed after split ring resonator (SRR) is introduced into the H-shaped PCA. Meanwhile, it is known that the coupling effect exists when the coupling coefficient is not zero. With the increasing of the coupling coefficient, and the radiation intensity of the resonance frequency peak increases and shifts. The adjusting range of the center frequency between 0.50−0.80 THz, the frequency modulation degree is 75%, and the peak radiation efficiency increases by 70% after simulating the S-shaped PCA. This work lays an important foundation for the design of THz wave resonance center frequency range and structure of high-power PCA.
2020,
32: 033201.
doi: 10.11884/HPLPB202032.190355
Abstract:
The experiments reveal, for the RF filter, the out-off-band transfer property under ultra wide band (UWB) pulses is essentially in agreement with that of continous wave (CW). However, for some frequencies in the in-band of the filter, the transfer function of UWB is much larger than 1. Moreover, the oscillating property is found in the time domain response of the filter. Therefore, based on the nonlinear passive intermodulation (PIM) and the Q-value, the response mechanisms of the filter are studied. The PIM of the filter shows nonlinear effects under the two different field strengths, which results in the limited universality of measurement results. Furthermore, the signal through the filter is predicted by making use of the two measured transfer functions. The predicting results under CW pulse are smaller than the measured ones in energy and peak power. In a word the response mechanisms of the filter under UWB pulse does differ from the that under CW pulse, i. e., the measured results of CW can’t be applied for the UWB effect analysis and evaluation.
The experiments reveal, for the RF filter, the out-off-band transfer property under ultra wide band (UWB) pulses is essentially in agreement with that of continous wave (CW). However, for some frequencies in the in-band of the filter, the transfer function of UWB is much larger than 1. Moreover, the oscillating property is found in the time domain response of the filter. Therefore, based on the nonlinear passive intermodulation (PIM) and the Q-value, the response mechanisms of the filter are studied. The PIM of the filter shows nonlinear effects under the two different field strengths, which results in the limited universality of measurement results. Furthermore, the signal through the filter is predicted by making use of the two measured transfer functions. The predicting results under CW pulse are smaller than the measured ones in energy and peak power. In a word the response mechanisms of the filter under UWB pulse does differ from the that under CW pulse, i. e., the measured results of CW can’t be applied for the UWB effect analysis and evaluation.
2020,
32: 033202.
doi: 10.11884/HPLPB202032.190402
Abstract:
This paper presents a high-precision Runge-Kutta (RK) method for solving transmission line equations. This method adopts high-order Taylor expansion in space, which improves the approximation accuracy of spatial differentiation. Compared with the traditional finite element time-domain method, when the number of samples per wavelength is the same, RK method has higher precision. At the same time, according to the Taylor model, researchers use RK method to solve transmission line equation in the external field excitation. The correctness and high precision of the RK method are verified by numerical examples of our study.
This paper presents a high-precision Runge-Kutta (RK) method for solving transmission line equations. This method adopts high-order Taylor expansion in space, which improves the approximation accuracy of spatial differentiation. Compared with the traditional finite element time-domain method, when the number of samples per wavelength is the same, RK method has higher precision. At the same time, according to the Taylor model, researchers use RK method to solve transmission line equation in the external field excitation. The correctness and high precision of the RK method are verified by numerical examples of our study.
2020,
32: 035001.
doi: 10.11884/HPLPB202032.190094
Abstract:
Laser-triggered pseudospark switches, also called back-lighted thyratrons (BLTs), are low pressure, high voltage, high current glow-mode switches The feasibility of BLTs is verified. The laser beams with wavelengths of 266 nm and 532 nm were used in the test. In the non-focused mode, the minimum trigger energy for 266 nm laser is 15 mJ, the anode ignition delay time is about 340 ns, and the time jitter is about 40 ns. The minimum trigger energy for 532 nm laser is 83 mJ, the anode ignition delay time is about 420 ns, and the time jitter is about 60 ns. In the focused mode, the minimum trigger energy for 266 nm laser is 4 mJ, when the laser trigger energy is 8 mJ, the anode delay time is 190 ns, the jitter is less than 1 ns. The minimum trigger energy for 532 nm laser is 6 mJ, when the laser trigger energy is 8 mJ, the anode delay time is than 240 ns, the jitter is less than 1 ns. The methods to further reduce the energy of the laser trigger will be studied in the future.
Laser-triggered pseudospark switches, also called back-lighted thyratrons (BLTs), are low pressure, high voltage, high current glow-mode switches The feasibility of BLTs is verified. The laser beams with wavelengths of 266 nm and 532 nm were used in the test. In the non-focused mode, the minimum trigger energy for 266 nm laser is 15 mJ, the anode ignition delay time is about 340 ns, and the time jitter is about 40 ns. The minimum trigger energy for 532 nm laser is 83 mJ, the anode ignition delay time is about 420 ns, and the time jitter is about 60 ns. In the focused mode, the minimum trigger energy for 266 nm laser is 4 mJ, when the laser trigger energy is 8 mJ, the anode delay time is 190 ns, the jitter is less than 1 ns. The minimum trigger energy for 532 nm laser is 6 mJ, when the laser trigger energy is 8 mJ, the anode delay time is than 240 ns, the jitter is less than 1 ns. The methods to further reduce the energy of the laser trigger will be studied in the future.
2020,
32: 035002.
doi: 10.11884/HPLPB202032.190339
Abstract:
Three-electrode field-distortion gas switch is a crucial element of modular fast linear transformer driver (FLTD). Electrode erosion affects the trigger jitter during the lifetime of the switch, which in turn can affect the output characteristics of FLTD. Therefore, studying the impact of electrode erosion on the trigger jitter of the switch is of great significance to optimize the switch structure and predict the switch life. This paper studies the erosion characteristic of intermediate electrode of three-electrode switch, and the electrode materials are stainless steel and brass. The key factors affecting the lifetime of switch are obtained by considering the changing rules of trigger and erosion characteristics, which provides theoretical support for the optimization of the performance of the three-electrode switch. The results show that the erosion area and surface roughness of stainless steel and brass electrodes increase with discharge times. The brass electrode is ablated more seriously and the stainless steel electrode has higher surface roughness. With the increase of discharge times, the breakdown point moves to the electrode edge area, which affects the insulation performance of the switch.
Three-electrode field-distortion gas switch is a crucial element of modular fast linear transformer driver (FLTD). Electrode erosion affects the trigger jitter during the lifetime of the switch, which in turn can affect the output characteristics of FLTD. Therefore, studying the impact of electrode erosion on the trigger jitter of the switch is of great significance to optimize the switch structure and predict the switch life. This paper studies the erosion characteristic of intermediate electrode of three-electrode switch, and the electrode materials are stainless steel and brass. The key factors affecting the lifetime of switch are obtained by considering the changing rules of trigger and erosion characteristics, which provides theoretical support for the optimization of the performance of the three-electrode switch. The results show that the erosion area and surface roughness of stainless steel and brass electrodes increase with discharge times. The brass electrode is ablated more seriously and the stainless steel electrode has higher surface roughness. With the increase of discharge times, the breakdown point moves to the electrode edge area, which affects the insulation performance of the switch.
2020,
32: 035003.
doi: 10.11884/HPLPB202032.190300
Abstract:
Synchronous induction coil launcher mainly uses pulse current to supply power directly to the coil. The temperature rise of armature and coil will occur in the actual working process, and it is a major factor restricting the development of coil launcher to miniaturization and high speed. In this paper, the temperature rise model of electromagnetic coil is established. For single trigger, Comsol and self-programmed Coilgun are used to calculate, and the corresponding test platform is built to verify the temperature rise. The Comsol method with direct coupling is the most accurate method, and the change of material parameters with temperature can also be considered. The simulation results show that the temperature rise of armature is about 4.2 ℃ and the maximum temperature rise of coil is 7.7 ℃. Because of the limitation of measurement delay and sampling frequency of thermocouple temperature sensor, the armature temperature test curve can not measure the maximum temperature point in the simulation curve, it can record the temperature change curve in the whole test process. The change of temperature and the final stable temperature are basically consistent with that of the simulation. The maximum error is 6.1%, which shows the accuracy of the simulation. This study lays a foundation for subsequent multi-stage coil continuous launching.
Synchronous induction coil launcher mainly uses pulse current to supply power directly to the coil. The temperature rise of armature and coil will occur in the actual working process, and it is a major factor restricting the development of coil launcher to miniaturization and high speed. In this paper, the temperature rise model of electromagnetic coil is established. For single trigger, Comsol and self-programmed Coilgun are used to calculate, and the corresponding test platform is built to verify the temperature rise. The Comsol method with direct coupling is the most accurate method, and the change of material parameters with temperature can also be considered. The simulation results show that the temperature rise of armature is about 4.2 ℃ and the maximum temperature rise of coil is 7.7 ℃. Because of the limitation of measurement delay and sampling frequency of thermocouple temperature sensor, the armature temperature test curve can not measure the maximum temperature point in the simulation curve, it can record the temperature change curve in the whole test process. The change of temperature and the final stable temperature are basically consistent with that of the simulation. The maximum error is 6.1%, which shows the accuracy of the simulation. This study lays a foundation for subsequent multi-stage coil continuous launching.
2020,
32: 035004.
doi: 10.11884/HPLPB202032.190283
Abstract:
This paper proposes a novel motor-driving charging integrated topology with high-frequency AC link (HF AC-link), soft-switching operation and high-frequency (HF) galvanic isolation, which can apply to the two modes of motor driving control and charging. The topology belongs to a new class of resonant AC-link topology, and its link is composed of a series ac inductor/capacitor (LC) pair.When the topology is working in the forward direction, the driving motor is in the motor driving control state, and the battery is being charged in the backward working period. In this paper, the principle of operation of the two working modes of the new topology is introduced in detail. The effective control strategy is used and the simulation model is built by MATLAB/Simulink software. The integrated topology and control strategy are verified. The simulation results show that the topology works. The charging mode can meet the different voltage requirements of the whole charging phase of the battery; working in the motor driving mode, the stator current exhibits a good three-phase sinusoidal shape in both the acceleration process and the normal working process, and the rotation speed can reach a given value, thereby proving the feasibility of this topology and control strategy.
This paper proposes a novel motor-driving charging integrated topology with high-frequency AC link (HF AC-link), soft-switching operation and high-frequency (HF) galvanic isolation, which can apply to the two modes of motor driving control and charging. The topology belongs to a new class of resonant AC-link topology, and its link is composed of a series ac inductor/capacitor (LC) pair.When the topology is working in the forward direction, the driving motor is in the motor driving control state, and the battery is being charged in the backward working period. In this paper, the principle of operation of the two working modes of the new topology is introduced in detail. The effective control strategy is used and the simulation model is built by MATLAB/Simulink software. The integrated topology and control strategy are verified. The simulation results show that the topology works. The charging mode can meet the different voltage requirements of the whole charging phase of the battery; working in the motor driving mode, the stator current exhibits a good three-phase sinusoidal shape in both the acceleration process and the normal working process, and the rotation speed can reach a given value, thereby proving the feasibility of this topology and control strategy.
2020,
32: 035005.
doi: 10.11884/HPLPB202032.190354
Abstract:
This paper introduces the basic principle and design ideas of absorptive method for X-ray energy spectrum measurement. Si-PIN detectors array and Cu, Al attenuation materials were used to design the energy spectrometer combining theoretical calculation and experimental study. The collimating and anti-interference system was developed to obtain higher signal-to-noise ratio waveforms. The influence of scattering was researched. The different attenuation waveforms of pulsed hard X-ray at ShanguangⅡ accelerator were measured experimentally in the vacuum environment. The energy spectrum was calculated. The maximum energy of X-ray was about 600 keV, and the average energy was about 89.1 keV, which agreed with the calculation results.
This paper introduces the basic principle and design ideas of absorptive method for X-ray energy spectrum measurement. Si-PIN detectors array and Cu, Al attenuation materials were used to design the energy spectrometer combining theoretical calculation and experimental study. The collimating and anti-interference system was developed to obtain higher signal-to-noise ratio waveforms. The influence of scattering was researched. The different attenuation waveforms of pulsed hard X-ray at ShanguangⅡ accelerator were measured experimentally in the vacuum environment. The energy spectrum was calculated. The maximum energy of X-ray was about 600 keV, and the average energy was about 89.1 keV, which agreed with the calculation results.
2020,
32: 035006.
doi: 10.11884/HPLPB202032.190400
Abstract:
This paper presents the design and verification of a portable resonant voltage doubling capacitor charging power supply with an input voltage of 24 V and an output voltage of 3 kV. According to the characteristic of high voltage ratio, this power supply adopts a topology structure combining the series resonant topology and the voltage doubling rectifier, which avoids the adverse effects of excessive number of turns on the secondary side of the high frequency transformer and excessive distributed parameters. The core components such as high frequency transformer, resonant capacitor and switching device were designed and debugged. The power supply was used to conduct the capacitor charging experiment, and the test results have verified the correctness of the design.
This paper presents the design and verification of a portable resonant voltage doubling capacitor charging power supply with an input voltage of 24 V and an output voltage of 3 kV. According to the characteristic of high voltage ratio, this power supply adopts a topology structure combining the series resonant topology and the voltage doubling rectifier, which avoids the adverse effects of excessive number of turns on the secondary side of the high frequency transformer and excessive distributed parameters. The core components such as high frequency transformer, resonant capacitor and switching device were designed and debugged. The power supply was used to conduct the capacitor charging experiment, and the test results have verified the correctness of the design.
2020,
32: 035007.
doi: 10.11884/HPLPB202032.190383
Abstract:
To improve the housing lifetime, insulation reliability and assembly consistency, the process and breakdown characteristics of a ceramic packaged multi-gap gas switch used for fast linear transformer driver (FLTD) were studied based on the multi-gap gas switch with stackable insulators and electrodes. The effects of different sealing processes on the electric field distribution of the interface between ceramic and metal were compared and analyzed, then the reasonable sealing structure was optimized. A ceramic packaged multi-gap gas switch was designed and its self-breakdown and triggering characteristics were experimentally tested. The results show that when the switch operates at the charging voltage of ±100 kV, the gas pressure of about 0.3 MPa and the peak current of 30 kA, the average delay time of 5 000 shots is 36.4 ns and the jitter is 2.8 ns. The ceramic package gas switch has the advantages on productization and maintenance-free, and will have broad application prospects in FLTD module.
