Just Accepted manuscripts are peer-reviewed and accepted for publication. They are posted online prior to technical editing formatting for publication and author proofing.
Display Method:
Research on real-time target image generation method under multi-light source illumination
Zhang Yushuang, Su Hua, Xie Xiaogang, Wang Rui, Zhang Feizhou
 doi: 10.11884/HPLPB202436.230442
[Abstract](3) [PDF 1658KB](0)
Abstract:
Impacted by various factors such as geographical position, sun and atmospheric environment, it is impossible to obtain the real images of space targets under various postures and illumination conditions, let alone the interaction between laser, sun and background light. In this paper, a real-time target image generation method under multi-light source irradiation is proposed. This method is based on the modern graphics card programming technique and frame caching object advantages. At the GPU (Graphics Processing Unit) side, shader language is used to efficiently calculate target brightness values and enhance realism under the influence of multi-light source. The open-source 3D graphics engine named OSG (Open Scene Graph) helps support 3D model files of various formats and improve the compatibility with the domestic Kirin operating system as well as common battlefield situation display software. Simulation experiments demonstrate the effectiveness and superiority of the proposed method.
Study on glow discharge triggered repetitive frequency pseudospark switch
Ding Wenjing, Feng Jinjun, Zhang Ming, Yang Hongfei
 doi: 10.11884/HPLPB202436.240036
[Abstract](4) [PDF 7709KB](0)
Abstract:
The pseudospark switch works in the left branch of Paschen curve with low gas pressure, which has the advantage of ns-level breakdown time, 100 kA-level pulse current and long lifetime. High pules repetition frequency (PRF) pseudospark switch are widely used in both civil and military fields. This paper focuses on the double-pulse trigger structure, and the switch with this structure is tested with 10 kV anode voltage for different gas pressure, pre-trigger voltage and main trigger voltage. Then the corresponding relationship between the gas pressure, the two trigger voltages and trigger current are calculated respectively. Finally, the influence of two pulses on the trigger process is analysed. The results show that the minimum trigger voltage is only 100 V, and the switch can work stably with high repetition frequency.
A design of B-dot calibration simulator for azimuthal transmission line
Zhang Xinjun, Luo Weixi, Hu Yixiang, Yin Jiahui, Zhou Wenyuan
 doi: 10.11884/HPLPB202436.230341
[Abstract](9) [PDF 3287KB](1)
Abstract:
An off-line calibration platform is designed based on the requirement of off-line calibration of induction cavity azimuthal transmission line current probe.The analog device is a flat-plate transmission line structure, which has lower distortion than on-line calibration.The source of cross-platform calibration error is analyzed, and the measures to reduce the error are put forward.The analysis shows that the installation eccentricity and probe longitudinal installation depth are the biggest sources of cross-platform calibration error, which need to be paid attention to in engineering design. An off-line calibration platform is established and the error analysis is carried out. The result of 3.3% cross-platform calibration error is obtained.
Progress in active phase control for large-scale coherent laser beam combining
Zhou Hongbing, Zhang Haoyu, Li Min, Feng Xi, Xie Lianghua, Liu Yu, Chu Qiuhui, Yan Yuefang, Tao Rumao, Lin Honghuan, Wang Jianjun, Yan Lixin, Jing Feng
 doi: 10.11884/HPLPB202436.230426
[Abstract](15) [PDF 32277KB](5)
Abstract:
Large-scale coherent beam combining is one of the effective techniques to break through the limit of a single laser, and obtain extreme characteristics laser such as ultra-high peak/average power, ultra-high pulse energy, ultra-high spatial/spectral brightness, and the key to large-scale coherent beam combining is active phase control. Active phase control technology can control the phase of each beam actively, compensate for coherence degradation and efficiency reduction caused by phase noise, and realize high-quality combined laser. Since the proposal of coherent beam combining technology, researchers have developed a variety of active phase control methods for phase correction, among which active phase control methods suitable for large-scale coherent laser beam combining have developed rapidly. In this paper, active phase control methods for large-scale coherent laser beam combining are systematically reviewed, and the principles, characteristics, application scenarios and expansibilities of different methods are analyzed. The latest progress and landmark achievements of coherent beam combining achieved by various active phase control methods are introduced, and the breakthrough result of 6 μs closed-loop locking time for 19-channel coherent beam combining has been reported for the first time. the future development trend of large-scale active phase control methods is predicted.
Evaluation of reliability improvement effect on laser adaptive optics systems
Jia Qiwang, Li Xinyang, Gan Yongdong, Ma Ruihao, Mei Yue, Sina Zhuoma
 doi: 10.11884/HPLPB202436.230436
[Abstract](13) [PDF 1084KB](4)
Abstract:
With the development of adaptive optics (AO) technology in laser field, a variety of improvement measures based on software monitoring and hardware protection have been added to the classical AO system to ensure the stable and continuous light output of laser AO system. Facing the reliability challenge brought by the increase of structural complexity, how to build a system failure model to evaluate the reliability of laser AO system has become an important part of the development of laser AO system. In this paper, a dynamic fault tree (DFT) method is proposed to evaluate the reliability of laser AO system, and the dynamic fault tree is established according to the dynamic relationship between the equipment. The bottom event failure rate is estimated by combining the manufacturer information, fatigue life test and historical data. The reliability parameters of DFT are obtained by using binary decision graph and Markov model. Using DFT to analysis the reliable running time of the AO system increasing by the improvement measures, the result shows more than ten times improvement relative to the basic fault tree. During the actual system joint commissioning, no self-induced failure occurred during the expected reliable running time, which is consistent with the DFT estimate. It is proved that the reliability evaluation of laser AO system with improved measures is more accurate by using DFT method.
Research on working characteristics of hydrogen thyratron
Zhao Yanhao, Rao Bo, Yang Yong, Yu Haojun, Zhang Ming
 doi: 10.11884/HPLPB202436.240040
[Abstract](6) [PDF 1810KB](0)
Abstract:
The working characteristics of the hydrogen thyratron and the optimization effect of the potential equalization treatment are investigated experimentally. Experiments show that the heating voltage had a greater influence on the working characteristics of hydrogen thyratron, on the premise of not appear self-discharge phenomenon on its use higher heating voltage can obtain better conduction performance. The difference of trigger pulse and anode voltage have little effect on the conduction performance of hydrogen thyratron. Using resistors to equalize the voltage of hydrogen thyratron can make the voltage distribution more uniform and alleviate the phenomenon of self-discharge. The research provides reference and guidance for the use of hydrogen thyratron.
Research on insulated gate bipolar transistor drive circuit of high pulse repetition precision solid state modulator
Shi Xiuqian, He Dayong, Li Fei, Gan Nan, Mu Yajie, Li Jingyi
 doi: 10.11884/HPLPB202436.240031
[Abstract](15) [PDF 11053KB](5)
Abstract:
The adder topology solid state modulator is a device that uses insulated gate bipolar transistors (IGBTs) to discharge the stored energy of capacitors to generate high voltage pulses. Compared with pulse forming network (PFN) type modulator, it has lots of advantages such as modularity, good stability, and long lifespan. However, the normal operation of IGBT requires the use of gate drive circuit to amplify the control signal, and the performance of the drive circuit directly affects the switching characteristics of the IGBT, ultimately affecting the quality of pulse voltage. Especially the turn-on jitter index of the drive circuit, which is one of the key factors affecting the pulse voltage repetition precision. Based on the operating characteristics of IGBT in the adder topology solid state modulator, the drive circuit was studied with the goal of improving pulse voltage repetition precision. The impact of turn-on jitter on voltage repetition precision was analyzed, the design principle was introduced, the drive circuit board was developed, and its working performance was experimentally tested using a discharge module. The test results indicate that the turn-on jitter of the drive circuit is 300 ps, which is three times better than commercial driving circuits. At the charging voltage of 1 kV, the discharge module discharges on a 0.5 Ω load, forming a pulse voltage with the rise time of 500 ns and the peak-to-peak value of turn-on jitter below 5 ns. When the desaturation fault occurs, the drive circuit can turn off the IGBT within 4 µs. This drive circuit meets the working requirements of high pulse repetition precision solid state modulators.
Simulation of coolant boiling phenomenon in sodium cooled fast reactor based on porous medium approach
Hui Tianyu, Tong Lili, Cao Xuewu
 doi: 10.11884/HPLPB202436.230408
[Abstract](8) [PDF 1914KB](0)
Abstract:
As the first stage of severe accidents in sodium cooled fast reactors, accurate prediction of the occurrence time and location of coolant boiling is of great significance for the safety assessment of Sodium Cooled Fast Reactors (SFR). Based on a two fluid six equation model, conservation equations are constructed for the gas-liquid two-phase flow of sodium. The evaporation-condensation model is used to characterize the interphase mass exchange, and explicit and implicit methods are used to calculate evaporation-condensation model. Constitutive relationships such as Sobolev resistance model, two phase flow heat transfer model, and phase momentum exchange are considered. A porous medium analysis approach which is suitable for simulating SFR coolant boiling was developed, and comparative verification was conducted using KNS-37 L22 loss of flow experiment data. L29 flow data is used to verify the applicability of the model. The results indicate that the established sodium boiling porous medium analysis approach can effectively simulate the boiling phenomenon. It predicts that the boiling time will be around 6.3 seconds, which is 0.2 seconds different from the experiment. The overall trend of temperature and flow rate changes are in good agreement with experimental data.
Preparation and luminescence performance of phosphor@SiO2 aerogel composite luminescent material for laser illumination
Feng Jie, Gao Yan, Zhu Jiayi, Bi Yutie, Ren Hongbo
 doi: 10.11884/HPLPB202436.240010
[Abstract](6) [PDF 10730KB](1)
Abstract:
The preparation of Tb3Al5O12 (TAG) phosphors was achieved through the sol-gel method. Thermal analysis data confirm that an increase in the H3BO3 molar ratio correlates with a reduction in the transition temperature of the final phase. Concurrently, scanning electron microscopy revealed that an elevated H3BO3 molar ratio results in larger phosphor particle sizes. Under the excitation wavelength of 275 nm, the emission spectrum manifests multiple peaks within the 480-650 nm range, originating from the 5d→4f transitions of Tb3+ ions. Subsequently, the phosphor@SiO2 aerogel composite luminescent material was successfully synthesized through a combination of physical doping and a supercritical drying process. This composite luminescent material exhibited a substantial increase in the internal quantum yield, reaching 63.64% compared to the standalone phosphor. Excited by a 355 nm laser source, the phosphor@SiO2 aerogel composite luminescent material demonstrated the capability for wire-free, long-distance luminescence with commendable uniformity. These findings demonstrate the potential application prospects of the phosphor@SiO2 aerogel composite luminescent material in the domain of laser emergency lighting.
Design of a high-power miniaturized waveguide E-plane heterodyne power combiner
Su Yiyu, Li Xiangqiang, Wei Yihong, Zhang Jianqiong, Wang Qingfeng
 doi: 10.11884/HPLPB202436.230433
[Abstract](2) [PDF 11482KB](2)
Abstract:
The existing heterodyne power combiners are not suitable for applications that the input and output of signal need to be the same direction with limited space. In order to solve the problem, this paper designs a high-power and miniaturized heterodyne power combiner operating at frequencies of 9.3 GHz and 9.7 GHz. Based on the traditional filter-based heterodyne power combiner, the proposed design utilizes a over-mode rectangular waveguide E-plane power combiner. The waveguide filters are parallel and the input ports are also located on the same plane, so that the combiner is suitable for the specific applications. The size of the rectangular waveguide are reduced to suppress higher-order modes. Besides, the distance between mode strips is decreased in integer multiples of half-wavelength of the waveguide to compresses the overall length with high power capacity. The combiner has a length of 9.2 λ a width of 1.5 λ and a height of 2.8 λ, while λ is the wavelength corresponding to the frequency of 9.5 GHz in free space. At 9.3 GHz and 9.7 GHz, the return loss of the combiner is more than 20 dB, its combining efficiency is more than 98% , and the isolation between input ports is more than 20 dB. At microwave pulse breakdown threshold of 80 MV/m, the combiner provides power capacities of 310 MW.
Design of an ultra-wideband thin frequency selective surface absorber
Li Xi, Wang Dongjun, Zhang Yuan, Zhao Xiang, Yan Liping
 doi: 10.11884/HPLPB202436.230443
[Abstract](10) [PDF 7803KB](2)
Abstract:
An novel ultra-wideband thin frequency selective surface (FSS) absorber loaded with lumped resistors is presented in this article. The proposed absorber consists of a single FSS lossy layer with a single resonance structure, and features thinness, ultra-wide bandwidth and polarization-insensitivity. The absorber is designed with lumped resistors loaded at positions that deviates from the central symmetry axis of the unit cell. It also features the nonuniformly wide metallic strips and the addition of branches with circular tops. All these specific design effectively enhances the bandwidth of the absorber. Both an equivalent circuit model and full wave simulation demonstrate that the proposed absorber achieves over 90% absorption in the frequency range of 6.0-26.77 GHz, with a fractional bandwidth of 126.8%. The thickness of the proposed absorber is 0.086 λL (the wavelength at the lowest frequency), which is only 1.09 times the ultimate thickness based on Rozanov’s theory. A prototype of the proposed absorber is fabricated, good agreements between experimental and simulated results are observed, validating the effectiveness of the design.
Slow drift suppression of continuous laser carrier synchronization system
Jia Yanqing, Du Yingchao, Huang Wenhui
 doi: 10.11884/HPLPB202436.230353
[Abstract](14) [PDF 1640KB](0)
Abstract:
The high-precision synchronization system is one of the key factors for the accelerator to generate high-quality beams. This paper is based on the existing continuous laser carrier synchronization system of Tsinghua University and analyzed the long-term drift of the reference microwave signal phase difference between different receiving ends, that is, the slow drift of the synchronization system. An EOM bias voltage control method based on the amplitude of the reference microwave signal at the receiving end is proposed to suppress slow drift. After adopting this method, the slow drift of the L-band (1 300 MHz) synchronization system of Tsinghua University's VHF band photocathode electron gun test platform was suppressed to 10.45 fs@24 h, and the slow drift of the S-band (2 856 MHz) synchronization system of Tsinghua University's Thomson Scattering Facility (TTX) was suppressed to 10.53 fs@24 h. Moreover, this method can make the entire synchronization system work in a room temperature environment, effectively improving the adaptability of the synchronization system to the working environment temperature.
Research of aircraft pose estimation based on neural network feature line extraction
Chen Changjun, Tang Dan, Yang Hao, You anqing, Pan Xudong
 doi: 10.11884/HPLPB202436.240032
[Abstract](12) [PDF 6016KB](1)
Abstract:
In order to estimate the aircraft pose in complex situation, this paper proposes a new method of aircraft pose estimation based on neural network line extraction. This method uses 3D model to render images, and forms dataset through adding backgrounds. The dataset is enhanced to make the algorithm robust. The line extraction model uses convolutional neural network to extract deep features, and uses heatmap to obtain aircraft feature lines. The target pose is solved by combining the aircraft feature line, the aircraft 3D model and the perspective-n-line method. The accuracy of the line extraction model is 91% in complex background. The accuracy is 84% after adding sorts of noises. The aircraft pose is solved by using EPnL algorithm and nonlinear optimization. The average angle error is about 0.57°, and the average translation error is about 0.47% when the target is in a complex background. After adding sorts of noises to the image, the average angle error is about 2.11°, and the average translation error is about 0.93%. The aircraft pose estimation method proposed in this article can accurately predict the aircraft pose under complex backgrounds and various types of noise, and its application scenarios are more extensive.
Research progress in deep learning for wavefront reconstruction and wavefront prediction
Qiu Congpan, Liu Guodong, Zhang Dayong, Hu Liusen
 doi: 10.11884/HPLPB202436.230430
[Abstract](17) [PDF 19076KB](4)
Abstract:
The combination of deep learning technology and adaptive optics technology is expected to effectively improve the wavefront correction effect and better cope with more complex environmental conditions. The research progress of applying deep learning in the direction of wavefront reconstruction and wavefront prediction is detailed, including the specific research methods and corresponding neural network structure design adopted by the researchers in these two research directions, and the performance of these neural networks in different practical application scenarios is analyzed, and the differences between the different neural network structures are compared and discussed, and the specific impacts of the structural differences are explored. The differences between the different neural network structures are compared and discussed, and the specific impacts brought by the structural differences are explored. Finally, the existing methods of deep learning in these two directions are summarized, and the future development trend of the deep integration of deep learning and adaptive optics technology is also prospected.
Design of discrete magnetic coupling drivers for high-frequency nanosecond pulse modulator
Chen Lei, Li Guochao, Zhang Ge, Zhu Caihui, Qiu Jian, Zhao Hui, Liu Kefu
 doi: 10.11884/HPLPB202436.230306
[Abstract](19) [PDF 2531KB](4)
Abstract:
With the increasing and extensive applications of high-voltage nanosecond solid-state pulse generators in various fields such as biology, industry, and environment, the pulse waveform, voltage amplitude, pulse duration, and pulse repetition frequency have become essential controllable variables for specific pulse power applications. To further reduce the size and cost of the pulsed power supply, a high-voltage nanosecond pulse modulator with high repetition frequency is proposed with positive Marx circuit, drivers with multiple pulse transformers as the core, and ns rising time. This driver enables the design of a high-voltage nanosecond pulse modulator with ns-level rise time and high repetition frequency. The proposed driver features a compact structure and eliminates the need for multiple isolated power supplies for driving. It allows the gate voltage of two MOSFETs to rise and fall rapidly and synchronously at a high repetition frequency, enabling the generation of gate voltage with controllable amplitude within one hundred nanoseconds. In the case, not only is the maximum pulse width not limited by the magnetic core saturation, but also the negative bias voltage makes switch can be reliably turned off, improving the reliability of the circuit. In addition, the influence of different turns and magnetic core materials on the driving waveform is studied. A 14-stage pulse modulator prototype is developed. Test results show that the output voltage and pulse width of the modulator based on the drivers are continuously adjustable, with the ability to change the pulse profile. The maximum output voltage reaches 5.5 kV with 100 ns to 50 ms width, minimum rise time of approximately 18 ns, and a continuous repetition frequency of 100 kHz.
Design of high voltage constant current charging power supply based on LC series resonance
Jiang Jinbo, Xu Lin, Luo Zheng, Yang Wen, Tang Ming, Yao Yandong, Chen Rui
 doi: 10.11884/HPLPB202436.230295
[Abstract](31) [PDF 4453KB](28)
Abstract:
LC series resonant high voltage constant current charging power supply can realize high efficiency and fast charging of the capacitor and has an excellent capacity of anti-load short-circuit, which has extensive application prospects in high repetition frequency pulsed power systems. The efficiency of the charging power supply is a crucial factor to determine the ability of the system to operate at repetition rate. Improving efficiency is the primary goal of designing high-voltage capacitor charging power supply. According to the working principle of LC series resonant circuit, it can be analyzed that the operating mode of power supply, the switching frequency of the inverter bridge and the distribution parameters of the high-frequency transformer are the main ingredients affecting the efficiency. For a DC power supply with a power of 10 kW and an output voltage of 40 kV, the main circuit parameters were calculated and the circuit model was established using Pspice to verify its accuracy. The soft switching technology was used to reduce the switching loss, and the high frequency transformer with smaller distribution parameters was designed to further improve the efficiency. On this basis, the overall structure design of the power supply was completed. Finally, the charging characteristics of the power supply were tested. Experimental tests indicate that the power supply can charge a 0.1 µF capacitor to 39.5 kV within 37 ms, and the charging efficiency of the power supply is 87.1%.
Method for predicting plasma channel length for rock breaking by pulsed discharge
Liu Yi, Liao Hongbin, Cheng Jin, Li Liuxia, Lin Fuchang, Zhao Yong
 doi: 10.11884/HPLPB202436.230432
[Abstract](36) [PDF 3001KB](21)
Abstract:
Aiming at the difficulty of predicting the length of rock-breaking arc plasma channel by high voltage pulse discharge, a comprehensive test platform for rock-breaking arc plasma channel by high voltage pulse discharge was constructed. The development characteristics and typical current and voltage parameters of arc plasma channel under granite-tap water combined medium were measured, and the broken region formed on the rock surface under different electrode spacing and pulse discharge times was extracted. Based on the energy balance equation, the impedance model of the arc plasma channel in rock is established. The approximate optimal solution of the impedance model parameters is obtained by iterative optimization algorithm. The relative error between the calculated results and the experimental results is less than 7%. Based on the optimized parameters, the length of plasma channel is predicted by the measured current and voltage data. The absolute error between the plasma channel length predicted by the model and the measured value is in the order of mm, and the relative error of both is less than 10%, which provides theoretical support for the matching design of power-electrode load in the high-voltage pulse discharge rock breaking system.
Application of MORPHY program in lead-cooled fast reactor
Li Jinzhou, Zhang Tengfei, He Donghao, Pan Qingquan, Liu Xiaojing
 doi: 10.11884/HPLPB202436.230357
[Abstract](21) [PDF 39621KB](10)
Abstract:
Lead cooled fast reactor has obvious advantages in fuel proliferation and nuclear waste treatment. For the Europe Lead-cooled System(ELSY), based on the “two-step method”, Monte Carlo software is used to generate few group component parameters, and after section correction, it is passed to the determining theory program MORPHY for core calculation. The effects of section modification and angle development order on the calculation accuracy were analyzed, and the effective multiplication factor, normalized flux level and control rod value of the ELSY core were quantified and compared. For different examples, transport correction and neutron multiplication effect correction were adopted, and the core calculation was developed with S4 order. The maximum deviation of effective multiplication factor was 38×10−5, the calculation deviation of control rod value was within 45×10−5, the maximum absolute deviation of normalized neutron flux density was 9.73%, and the average absolute deviation was less than 2%. The feasibility of MORPHY program in the physical analysis of lead-cooled fast reactor is preliminarily verified, which is of reference significance for the subsequent development and use of the program.
Simulation of the effect of hole shape on the performance of CsI: Tl scintillation screens based on silicon microchannel arrays
Zhao Zifeng, Wang Guozheng, Hao Ziheng, Zhang Ni, Ge Jun, Yang Jikai
 doi: 10.11884/HPLPB202436.230424
[Abstract](41) [PDF 4002KB](12)
Abstract:
The Geant4 program was used to simulate the effect of micropore shape on the performance of CsI:Tl X-ray scintillation screen based on silicon microchannel array. The simulated scintillation screen performance parameters include: scintillation photons, bottom light output, transmission efficiency, percentage of n times total reflection, and Modulation transfer function versus spatial resolution. The shapes of the micropores were set to be square and circular during the simulation process, and the microchannel array period was the same for both hole shapes, which was 10 μm. The simulation results show that the number of scintillation photons in square micropores is better than that in circular micropores, and the number of fluorescent photons is directly proportional to the cross-sectional area of the micropores; Thickness less than 400 μm, the bottom light output of square micropores is better than that of circular micropores,.When the thickness greater than 400 μm, the situation is opposite; The transmission efficiency of circular micropores is better than that of square micropores; When the thickness of 40 and 200 μm ,the spatial resolution of the square micropores scintillation screen is better than that of the circular micropores scintillation screen with the same thickness. A square microporous CsI: Tl scintillation screen sample was prepared, and the relationship between its MTF and spatial resolution was measured. When the MTF was 0.1, the spatial resolution was 22.6 lp/mm.
Laser-diode-pumped electro-optic Q-switched Tm:SrF2 laser
Wu Guang, Zhang Zhen, Wang Tao, Ji Lailin, Cui Yong, Gao Yanqi, Sui Zhan
 doi: 10.11884/HPLPB202436.230140
[Abstract](33) [PDF 1104KB](9)
Abstract:
The Tm3+ gain medium with high doping concentration can improve the quantum efficiency of the laser through the cross relaxation process, but it also increases the energy loss and limits the improvement of laser efficiency caused by energy up-conversion. The fluorescence characteristics and laser performance of Tm:SrF2 crystal are studied. Under laser-diode (LD) end-pumping, a continuous-wave laser with a maximum output power of 2.99 W and a slope efficiency of up to 82.1% is realized. The pump threshold of the laser is 0.81 W, and the center wavelength is 1851 nm. Electro-optic Q-switching of the Tm:SrF2 laser is demonstrated. At the repetition rate of 500 Hz, a maximum pulse energy of 1.02 mJ and a minimum pulse width of 45 ns are achieved, resulting in a peak power of 22.67 kW. The experimental results indicate that the Tm:SrF2 laser based on LD pumping has very high efficiency and is expected to be an ideal pump source for optical parametric oscillators (OPO) and optical parametric amplifiers (OPA).
High voltage damped oscillator based on interstage self-triggering Marx circuit
Chen Yufeng, Wang Qingfeng, Li Xiangqiang, Zhang Jianqiong
 doi: 10.11884/HPLPB202436.230360
[Abstract](35) [PDF 2763KB](21)
Abstract:
In order to increase the output voltage and reduce the volume and cost of the high voltage damped oscillator, a 4×4 stage self-triggering Marx structure damped oscillator model is established in this paper. In this model, the main switch of each stage adopts series IGBTs module based on capacitor trigger mode. Only one isolated signal is provided to control the turn-on and turn-off of the primary discharge switch tube. The grid of the adjacent discharge tube is automatically charged and discharged through the interstage capacitance to make it turn-on and turn-off. The model improves the working voltage of Marx single stage and simplifies the driving circuit of each stage, and solves the problem of dynamic and static voltage equalization of switching tube by adding buffer circuit. Based on this topology, a prototype of a high-voltage damped oscillator is built, which outputs 16 kV damped oscillation waveform with a frequency of 1 MHz on an inductive load. The rise time of the waveform is about 75 ns, and the repetition frequency is 500 Hz. The prototype is small in size and stable in operation, which verifies the feasibility of the scheme.
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Display Method:
Reactive force field molecular dynamics simulation of structure and mechanical property of Si-doped glow discharge polymer
Huang Baosheng, Yang Wu, Yi Yong, Bi Peng
 doi: 10.11884/HPLPB202436.230316
[Abstract](27) [PDF 2601KB](3)
Abstract:
The structural models of Si-doped glow discharge polymer (Si-GDP) were established using reactive force field molecular dynamics simulation (ReaxFF MD), and the effects of silicon content, hydrogen content, and density on its hybrid carbon bonding and mechanical properties were investigated. The results show that with the silicon content increasing, the molecules tend to form a silicon-containing macromolecule, and the types and number of small molecules decrease, the silicon content improves the mechanical properties by promoting the binding of carbon and silicon atoms and inhibiting the formation of end-group sp3CH3. Besides, species such as ·C2H3, ·C3H5 and ·Si(CH3)3 were found during the formation of Si-GDP, which were in good agreement with the thin film deposition experiment of glow discharge polymer. The hydrogen content is measured as the atomic ratio of hydrogen to carbon and silicon, as the ratio grows, the number of model molecules did not change significantly, the ratio of sp3C and sp3CH3 increased, and the hydrogen content decreased the mechanical properties mainly by promoting the formation of sp3CH3. With the density increasing, the number of molecular species in the model did not change much, and the proportion of sp2C in the model was significantly increased, while the proportion of sp3C was slightly increased, the mechanical properties of Si-doped hydrogenated amorphous carbon were mainly improved by increasing the proportion of sp2C. This study provides an example for constructing Si-GDP by ReaxFF MD, and may provide a new method and reference for evaluating the structure and mechanical properties of Si-GDP.
Compact pulsed-power circuit methods and practice
Jiang Weihua, Tokuchi Akira, Sugai Taichi, Yu Liang, Feng Yu, Zhuang Longyu, Ren Xiaojing, Yang Junxiang
 doi: 10.11884/HPLPB202436.240053
[Abstract](32) [PDF 13721KB](11)
Abstract:
This review article aims at summarizing the basic principles of circuit methods used in compact pulsed-power generators. The concept of energy storage and voltage adding has been explained followed by the descriptions on switching unit design and control signal generation. Some examples of applications of these circuit methods are given that include Marx circuit using capacitor energy storage, Marx circuit using inductive energy storage, Marx circuit using hybrid energy storage, linear transformer driver (LTD) circuit using capacitive energy storage and LTD circuit using inductive energy storage.
Utilizing RTP crystal to generate fifth-order Stokes laser emission with 271 cm−1 Raman shift
Wang Jing, Jin Xinxin, Wang Yanyi, Wang Hongyan, Li Zhihong, Duan Yanmin, Zhu Haiyong
 doi: 10.11884/HPLPB202436.240004
[Abstract](17) [PDF 999KB](7)
Abstract:
The RbTiOPO4 crystal Raman emission at high-order Stokes with 271 cm−1 shift driven by an end-pumped passively Q-switched laser was demonstrated. The Nd:YAG and Cr4+:YAG bonding design was used to reduce the intracavity loss and make the laser system compact, so as to raise the intracavity photon density, which proved helpful for the conversion of Raman shift to high-order Stokes light. The first-Stokes laser with different Raman shifts is designed to oscillate in different cavities, and the first-Stokes laser with 687 cm−1 shift is suppressed by using the difference in cavity mode matching with the fundamental laser, and the fifth-order Stokes laser with 271 cm−1 shift is obtained. Under the pump power of 8.1 W, a 1 244 nm wavelength laser with an average output power of 230 mW was obtained, and the corresponding pulse width and pulse frequency repetition were 2.9 ns and 11.7 kHz, respectively. The 1 244 nm laser wavelength perfectly matched the OH−1 absorption peak in water, which could have significant applications in fields such as surface vegetation and planetary water detection.
Breakdown characteristics of pre-ionization trigger gap in different gases under bipolarity pulse
Wang Yi, Guo Fan, Chen Zhiqiang, Jia Wei, Wang Gefei, Shi Ling, Xie Linshen, Wu Gang, Wu Wei
 doi: 10.11884/HPLPB202436.230392
[Abstract](25) [PDF 2141KB](17)
Abstract:
The breakdown characteristics of trigger gap for the pre-ionization switch in N2, the mixture of N2 and SF6 and SF6 atmosphere under positive and negative pulse were investigated for the higher voltage grade and bipolarity application. The relationships between the breakdown voltage and delay time of the pre-ionization gap and the pressure of different kinds of gases were obtained, and the breakdown characteristics were compared for the pre-ionization gap under positive and negative polarities. The results of the experiment demonstrate that the breakdown process of the gap in N2 was more stable, and the linearity of breakdown voltage varying with pressure in N2 was the best among the three kinds of gases. The breakdown voltage was saturated only in SF6 with the increase of gas pressure. The breakdown voltage of the gap under negative polarity was higher than that under the positive at some certain values of the pressure, and this phenomenon might suggest that there was a polarity effect upon the breakdown process of pre-ionization gap. Compared with the mixture and N2, the absolute differences between negative and positive polarity for both breakdown voltage and delay time in SF6 were relatively higher. N2 should be preferred as the insulating medium for the pre-ionization gap to reduce the synchronization delay difference of the bipolar self-triggered switches. The polarity effect of the pre-ionization gap and the distinctions among the different kinds of insulated gas medium should be paid more attention in engineering applications for the pre-ionization gap.
Development and validation of V/N gas switches for photo conductive semiconductor switch triggers
Song Yuhui, Wang Lingyun, Zhou Liangji, Liu Hongwei, Zhang Dongdong, Chen Lin, Yuan Jianqiang, Deng Minghai, Xie Weiping, Gao Bin, Wang Ruijie
 doi: 10.11884/HPLPB202436.230347
[Abstract](35) [PDF 6606KB](21)
Abstract:
To meet the requirements of multi-channel precise synchronous trigger switch, photo conductive semiconductor switch (PCSS) is combined with V/N gas switch, which takes advantage of the photoelectric isolation, low trigger threshold, low delay time jitter and photoelectric isolation of PCSS, as well as the advantages of high operating voltage and strong load capacity of V/N gas switch. The core of the combination of the two switches is that the structural parameters of the V/N gas switch match the parameters of the PCSS trigger loop. The structural capacitance, trigger loop oscillation parameters and switching electric field distribution of the V/N gas switch are analyzed and calculated. The relationship between the structural capacitance of the V/N gas switch and the oscillation loop composed of PCSS and series inductors is studied. The self-breakdown voltage curve, on-delay time and delay time jitter of the switch under different under voltage ratios are obtained. The performance of the V/N gas switch for PCSS triggering is preliminarily verified.
Development and application of experimental platform for vacuum insulator stack
Zhou Yawei, Hu Yixiang, Yang Shi, He Deyu, Yin Jiahui, Luo Weixi, Zhang Xinjun
 doi: 10.11884/HPLPB202436.230410
[Abstract](32) [PDF 1502KB](18)
Abstract:
The study of vacuum surface flashover along the insulator ring was carried out. An experimental platform for vacuum insulator stack was built. The influence of flashover among insulator ring on the voltage of the vacuum insulator stack was evaluated by equivalent circuit model. Vacuum surface flashover along the three kinds of material insulator stacks were carried out, which verify the availability and reliability of the experimental platform. This work provides a reference for the engineering research of the vacuum insulator stack of pulse power device, and also provides an experimental platform for research of new insulation materials.
Vacuum surface flashover characteristics of cross-linked polystyrene under high repetition rate burst multi-pulse loading
Huang Ziping, Li Yuan, Deng Xu, Li Feng, Li Xin
 doi: 10.11884/HPLPB202436.230337
[Abstract](31) [PDF 2976KB](15)
Abstract:
Based on the requirement of high current multi-pulse accelerator, the surface flashover characteristics of cross-linked polystyrene (XLPS) material under burst multi-pulse in vacuum were studied experimentally. Vacuum surface flashover experiments were carried out with XLPS samples placed in flat electrodes under single pulse and three pulses with interval of 500 ns. Special phenomena such as continuous decrease of equivalent impedance of vacuum surface before flashover and continuous maintenance of flashover channel after pulse end were observed, and statistical data of vacuum surface flashover of XLPS materials under corresponding conditions were obtained. On the basis of experiments, the flashover characteristics of XLPS in vacuum under high repetition rate multi-pulse loading are analyzed, which provides experimental basis for insulation design of high repetition rate multi-pulse accelerator.
Cover and Contents
High Power Laser and Particle Beams, No 3, Vol 36, 2024
Editorial Office
2024, 36: 1-2.  
[Abstract](24) [PDF 5828KB](41)
Special Issue on High Power Microwave Technology
Achieving prolonged continuous operation of a self-designed 28 GHz/50 kW gyrotron
Hu Linlin, Huang Qili, Zhuo Tingting, Hu Peng, Gong Shenggang, Sun Dimin, Jiang Yi, Ma Guowu, Chen Hongbin, Ma Hongge
2024, 36: 033001.   doi: 10.11884/HPLPB202436.240049
[Abstract](128) [PDF 2556KB](62)
Abstract:

This paper presents the latest experimental results of a 28 GHz/50 kW continuous wave gyrotron, developed by Institute of Applied Electronics, Chinese Academy of Engineering Physics for applications in the electron cyclotron resonance heating (ECRH) system of magnetic confinement fusion devices, the electron cyclotron resonance (ECR) ion source in heavy ion accelerators and frontier scientific explorations. Stable prolonged continuous operation at multiple power levels ranging from 10 kW to 50 kW has been achieved through structural optimization and stability design verification. Typical sustained operation was observed at 16 kW for 3000 s, 26 kW for 900 s, 46 kW for 1800 s, and 50 kW for 300 s. Notably, a record-breaking continuous stable operation lasting up to 400 min was accomplished at a power level of 32 kW. This achievement represents China’s first successful development of a medium-power gyrotron capable of hour-level continuous operation.

A hierarchical method for verification of particle-in-cell/ Monte Carlo collision modelling on plasma discharges
Shang Tianbo, Yang Wei¹, Song Mengmeng, Zhou Qianhong
2024, 36: 033002.   doi: 10.11884/HPLPB202436.230335
[Abstract](136) [PDF 1172KB](38)
Abstract:
The verification of scientific computing currently places a strong emphasis on grid discretization methods for systems of deterministic partial differential equations. However, verifying particle-in-cell (PIC) simulations, which employ a particle-mesh method to model discharging plasmas, presents distinctive challenges. Firstly, PIC simulations require discretization not only in time and space but also in macro-particle weights. Secondly, challenges arise regarding the utilization of the discretized particle phase space distribution function for verification purposes. Thirdly, the interpolation of electric fields and charge distribution can significantly impact the overall accuracy of PIC convergence.When PIC methods are integrated with Monte Carlo (MC) methods, discretization and stochastic errors often combine, necessitating Richardson extrapolation in conjunction with ensemble averaging.To tackle these challenges, this paper introduces a hierarchical verification approach. It commences with order-of-accuracy tests for individual particle trajectories, electromagnetic field solvers, and binary-particle collisions. Discretization errors for integrated PIC and MC modules are then evaluated using classical physical models that possess exact solutions, such as space-charge-limited current and Fourier flow in gases. Finally, a code-to-code comparison is performed with benchmark examples of simplified discharge simulations.
Design of an S-band ultra-wideband energy selective surface
Zhou Tao, Hu Ning, Gai Longjie, Huang Wentao, Xu Yanlin, Liu Peiguo
2024, 36: 033003.   doi: 10.11884/HPLPB202436.230369
[Abstract](139) [PDF 4063KB](44)
Abstract:
In this paper, an energy selective surface (ESS) structure working in S-band is designed, which can realize ultra-wideband adaptive strong electromagnetic (EM) protection. The ESS is composed of top and bottom layers. The top layer includes two parallel strips and a patch, on which two PIN diodes are loaded, and the bottom layer includes two vertical stripes. When the incident EM intensity is lower than the threshold value, the ESS works in the transparent state, which makes the electromagnetic waves propagate; When the EM intensity exceeds the threshold value, the induced voltage generated between the metal strips and patch makes the PIN diode turn on, and the ESS enters the protective state and the electromagnetic wave is shielded. The working principle of the ESS is analyzed by simulating the surface current and electric field distribution in PIN diode on-off state and equivalent circuit model. The prototype was processed by PCB process and the insertion loss of weak field incident and shielding efficiency of strong field incident were measured. The experimental and simulation results are in great agreement. The results show that in the transparent state, the operating center frequency of the ESS is 2.7 GHz, and the operating band with insertion loss less than 1 dB is 2.2−3.5 GHz. In the protective state, the shielding efficiency of the operating band is greater than 10 dB, which meets the requirement of ultra-wideband.
Design of X-band low phase noise sapphire oscillator
Liu Ying, Xiong Yisong, Li Yue, Li Xin, Zeng Cheng, Ning Junsong, Bu Shirong, Wang Zhanping, Zhang Xiaoyu, Liu Shaoyang, Guo Wanting
2024, 36: 033004.   doi: 10.11884/HPLPB202436.230343
[Abstract](59) [PDF 1045KB](18)
Abstract:
The paper presents the design and temperature control of a low phase noise sapphire oscillator. Utilizing the theory of sapphire resonator, finite element simulation software is employed to accomplish the design process. The measured center frequency of the sapphire resonator is 9.84 GHz with a loaded Q value of 113000. By utilizing the sapphire resonator as a frequency selection network along with components such as amplifier, filter, phase shifter and coupler, a low-noise sapphire oscillator is constructed. The output frequency of this oscillator is 9.84 GHz with an output power of 9 dBm. It exhibits excellent performance in terms of phase noise: −117 dBc/Hz at 1 kHz deviation from the carrier, −144 dBc/Hz at 10 kHz deviation from the carrier, and −161 dBc/Hz at 100 kHz deviation from the carrier. This oscillator significantly enhances radar capabilities for the detection of low-speed and small targets.
Simulation of high power microwave oscillator with locked frequency and phase based on nested structure
Li Jiawen, Ge Xingjun, Dang Fangchao, Zhang Peng, Deng Rujin, Hu Xiaodong, Li Zhimin
2024, 36: 033005.   doi: 10.11884/HPLPB202436.230344
[Abstract](143) [PDF 3551KB](32)
Abstract:
The power capacity of high-power microwave generating devices is improved by increasing the overmode ratio of the slow wave structure. The nested structure allows the use of the hollow or inner conductor structure of the overmode device, while the low impedance of the nested structure device makes it a good match for low-impedance pulsed power sources. A high-power microwave oscillator with locked frequency and phase is proposed based on the nested structure. Compared with the traditional method to lock phase and frequency, a method based on coupling waveguide is proposed to realize the locked frequency and phase. The microwave generated by the outer relativistic klystron oscillator (RKO) or inner RKO leaks into the other RKO through the coupling waveguide to premodulate the electron beam to lock phase and frequency. In addition, a dual-way power combiner is designed at the operating frequency of the oscillator to realize the combination of the inner and outer high-power microwave. The power combiner can make up for the phase difference between the two output ways, increasing the power combination efficiency to 98.3%. When the diode voltage is 575 kV and the magnetic field is 0.6 T, the output power of inner and outer RKOs are 2.2 GW and 3.2 GW, respectively, with the frequency difference fluctuating less than 20 MHz and the phase difference stabilized near 10°; loading the designed power combiner, high power microwave with power of 5.31 GW and efficiency of 32.2% is obtained. The results show that the oscillator saturation time is shortened and the output power is increased when the nested device is in the locked state.
Coupling response of unmanned aerial vehicle antennas under high-power microwave radiation
Zhao Min, Chen Yazhou, Zhou Xing, Nie Yaning, Li Huijuan
2024, 36: 033006.   doi: 10.11884/HPLPB202436.230215
[Abstract](157) [PDF 13762KB](63)
Abstract:
Unmanned aerial vehicle (UAV) is vulnerable to interference and even damage under high-power microwave (HPM) radiation, and its airborne antennas are important coupling pathways. To study the coupling response of its airborne antennas under HPM radiation, taking the datalink antenna and the navigation receiver as the research objects, their coupling models under HPM radiation are established according to the actual layout of the UAV. The accuracy of the antenna models are verified by their far-field pattern and S11 parameter of the antenna. The coupling voltages induced on the ports of the datalink antenna and the navigation receiver antenna under HPM radiation with different scenarios and parameters are obtained, and typical scenario experiment is carried out to verify the simulation results. The results show that the coupling voltage induced on the port of the datalink antenna under L-band HPM radiation is higher than that under S, C and X bands HPM radiation. Compared with the horizontal polarization, HPM with the vertical polarization has better interference effect on the datalink of UAV, and the coupling voltage is linearly related to the radiated field strength and is less affected by the pulse width and the rise time of HPM. The coupling voltage induced on the port of the navigation receiver antenna under space-based HPM is higher than that under ground-based HPM. The research will provide the theoretical references in attacking UAVs with HPM weapons.
Design and experimental study of S-band permanent magnet relativistic magnetron
Zhang Yanyan, Chen Hong, Xu Jianjun, Deng Kun, Liu Dongsheng, Liu Qiao
2024, 36: 033007.   doi: 10.11884/HPLPB202436.230250
[Abstract](83) [PDF 1924KB](48)
Abstract:
In this paper, an S band all cavity extraction relativistic magnetron with permanent magnet is theoretically designed and numerically simulated, and an experimental investigation is also carried out. The initial structural parameters of the relativistic magnetron are obtained through theoretical analysis, and the model is optimized by particle simulation. The permanent magnetic field generation structure is designed according to the needs of the guiding magnetic field. Simulation results reveal that this permanent magnet relativistic magnetron could generate a microwave power of 1.978 GW corresponding to a power conversion efficiency of 49.2% when the driver voltage is 500 kV. This permanent magnet tube is tested on the high-voltage pulse drive platform. In the experiment, gigawatt class output microwave power was obtained, corresponding to a power conversion efficiency of about 40%. The experimental results are in good agreement with the simulation results.
Design and research of C-band miniaturized high power microwave output window
Mao Pengxin, Tang Yongliang, Wang Xiufang, Liu Qingxiang
2024, 36: 033008.   doi: 10.11884/HPLPB202436.230359
[Abstract](116) [PDF 11323KB](56)
Abstract:
To meet the high power capacity and compact application requirements of microwave output window in high power microwave system, a C-band miniaturized high power microwave output window is designed based on the design theory of traditional box window by optimizing the form structure and adding transition segments. By increasing the surface area of the window and changing the connection mode of the rectangular waveguide-circular waveguide transition segment, the power capacity can be increased and the longitudinal size of the microwave output window can be reduced. The “I” form structure can effectively suppress the influence of multipactor near the triple point(vacuum-media-mental) on the performance of the output window. On the basis of electromagnetic simulation, the multipactor near the triple point of the microwave output window is studied by using the Particle-in-Cell method. From the microscopic point of view, it is further confirmed that the "I" form structure can make the position of the triple point move, reduce the probability of multipactor generated by the electrons emitted by the triple point on the surface of the window, and reduce the breakdown risk of the microwave output window. The design results show that the main mode reflection coefficient of the microwave output window at the center frequency is lower than 0.01, the transmission efficiency is higher than 99.9%, and the power capacity can reach 47.9 MW.
A technology for generating intense annular electron beam with variable beam radius and its application
Zhou Fugui, Zhang Dian, Zhang Jun, Chen Yinghao, Jin Zhenxin, Zhou Shengyue
2024, 36: 033009.   doi: 10.11884/HPLPB202436.230394
[Abstract](73) [PDF 4316KB](26)
Abstract:
Intense annular electron beam with variable beam radius has important applications in high power microwave (HPM) generation devices with cross-band frequency hopping. This paper proposes a technology of changing the radius of annular electron beam based on the adjustment of the externally guided magnetic field. The core components of the technology include an annular cathode, an anode, an electron beam transfer channel, two transmission channels and an external guide magnet (a three-segment solenoid) system. When the current of the solenoid differs, the solenoid system can generate different magnetic field distributions. In the particle-in-cell (PIC) simulation, when the currents of the three segments are 1 025 A, 107 A, 107 A and 300 A, 300 A, 0 A respectively, the solenoid generates two magnetic fields to achieve the change of the electron beam radius. Based on the theory of single particle motion, this paper deduces the expression of the trajectory of electron beam guided by the gradient magnetic field, explains the principle of the electron beam radius variation under the gradient magnetic field, and investigates the influence of the slope and range of the gradient magnetic field on the electron beam radius. In the cross-band HPM devices simulation, the output power of X-band is 1.6 GW, the frequency is 8.2 GHz, and the power efficiency is 40%. The Ku-band has achieved a power output of 1.5 GW, a frequency of 14.4 GHz, and a power efficiency of 38%.
Low magnetic field X-band over-mode relativistic backward wave oscillator with dual-cavity reflector
Zuo Jingfan, Li Shifeng, Wu Yang, Huang Hua, Sun Limin, Song Falun
2024, 36: 033010.   doi: 10.11884/HPLPB202436.230319
[Abstract](50) [PDF 2223KB](27)
Abstract:
This paper propose an X-band over-mode high-efficiency relativistic backward wave oscillator (RBWO), whose main structure includes a dual resonant cavity reflector, a periodic slow wave structure and an inserted coaxial mode selector. The RBWO uses an over-mode structure and transmits a pure TM01 mode in the output waveguide. The dual-cavity reflector enables the slow-wave structure to achieve good isolation from the diode region under over-mode conditions, and at the same time provides sufficient pre-modulation for the electron beam to achieve high microwave conversion efficiency under low magnetic field. The addition of the coaxial inner conductor allows the device to work in TM02 mode, while eliminating other unnecessary mode competition, achieving higher power capacity. In the PIC simulation, under the conditions of a guiding magnetic field of 0.63 T, a diode voltage of 850 kV, and a beam current of 11.74 kA, a microwave output power of 3.5 GW was obtained, and the device efficiency was about 35%.
Influence of repeated frequency UWB electromagnetic pulse on GPS navigation receiver
Hu Ming, Chen Shengxian, Li Yonglong, Yuan Xuelin
2024, 36: 033011.   doi: 10.11884/HPLPB202436.230324
[Abstract](103) [PDF 4777KB](37)
Abstract:
While the global positioning system (GPS) is widely used, it is also susceptible to external interference. Therefore, it is of great significance to study the reliability of GPS navigation receivers. Ultra-wideband (UWB) electromagnetic pulse has a steep rising edge and a wide spectrum, it can interfere with GPS and has become a new navigation interference method. This paper explores the interference mechanism of repeated frequency UWB electromagnetic pulses to GPS navigation receivers by analyzing their energy spectrum line distribution and studies the relationship between their interference effect on GPS receivers and the pulse parameters. The results show that repeated frequency UWB electromagnetic pulses can cause nonlinear interference to the radio frequency front-end circuit of the navigation receiver, reducing the receiver's acquisition performance. Increasing the pulse field strength or repetition frequency can enhance the interference effect and even cause the receiver to lose its acquisition ability.
Design and measurement of high Q-factor coaxial resonant cavity
Lü Yankui, Yang Fuxiang, Dang Fangchao, Ge Xingjun, He Juntao
2024, 36: 033012.   doi: 10.11884/HPLPB202436.230294
[Abstract](103) [PDF 3092KB](31)
Abstract:
With the development of high power microwave sources towards high power, high frequency and long pulse, coaxial relativistic klystron amplifiers (RKA) have become one of the research hotspots in recent years. However, its development is limited by self-excited oscillation, etc. Therefore, a high Q-factor single-gap coaxial resonator is designed in this paper to suppress the self-oscillation caused by TEM mode leakage of the coaxial RKA. Through the theoretical analysis and simulation of TM01 mode and TEM mode conversion in a single-gap coaxial resonator, it is found that the depth difference and axial dislocated values of the upper and lower slots of the coaxial resonator have a great influence on the change of its Q factors. When the depth difference and axial dislocation value of the upper and lower slots are 0.3 mm and 0 mm respectively, the Q factor of the coaxial resonator has the maximum value (18 764). This means that the conversion between the two modes in the resonator is minimal, greatly reducing the risk of self-oscillation between several cascaded coaxial resonators. When three cascaded high-Q-factor single-gap coaxial resonators are applied to the compact coaxial RKA, the output microwave power of the device is stable, the spectrum is pure, and there are no self-excited oscillations in the simulation and experiments.
Study on the properties of low dielectric loss composite insulating materials for superconducting cables
Wang Mingyang, Dong Hailian, He Pengyu, Jiang Tao
2024, 36: 033013.   doi: 10.11884/HPLPB202436.230450
[Abstract](46) [PDF 3053KB](18)
Abstract:
Compared with traditional cables, superconducting cables have the advantages of no resistance loss, large transmission capacity and high reliability. However, polypropylene laminated paper as its main insulation has high loss factor, which leads to large dielectric loss in the operation of superconducting cables and increases the load of cooling system. In this paper, polytetrafluoroethylene filter paper with low loss factor is used to replace the kraft paper layer in the polypropylene lamination paper, and a sandwich structure composite insulation with porous surface can be formed by being hot-pressed with the polypropylene film. The test results show that replacing the polypropylene lamination paper with polytetrafluoroethylene/polypropylene composite material as the main insulation in the superconducting cable will reduce by more than half the dielectric loss. At the same time, due to the smaller dielectric constant difference between the polytetrafluoroethylene/polypropylene composite material and the liquid nitrogen used as the coolant in the high temperature superconducting cable and the volume effect of liquid nitrogen breakdown, the low dielectric loss composite insulation made of polytetrafluoroethylene filter paper with smaller aperture has stronger resistance to partial discharge and higher AC insulation breakdown strength, which can greatly improve the insulation reliability of the high temperature superconducting cable.
High Power Laser Physics and Technology
2 kW fiber laser pumped by long-wavelength laser diodes
Wang Peng, Meng Xiangming, Wu Hanshuo, Ye Yun, Yang Baolai, Xi Xiaoming, Shi Chen, Zhang Hanwei, Wang Xiaolin, Xi Fengjie, Wang Zefeng, Xu Xiaojun, Zhou Pu, Chen Jinbao
2024, 36: 031001.   doi: 10.11884/HPLPB202436.240035
[Abstract](121) [PDF 1163KB](48)
Abstract:

The high-power fiber laser pumped by laser diodes (LDs) has the advantages of high efficiency, small size, light weight, and good stability, and has been widely used in many fields such as industrial processing. To improve the absorption rate of pump laser, the 915 nm and 976 nm LDs are commonly used as the pump source of the traditional fiber lasers. The quantum defect and pump absorption coefficient are comparatively high in the fiber lasers pumped by these LDs, which leads to low transverse mode instability (TMI) threshold. To improve quantum efficiency and potential TMI threshold, the fiber laser directly pumped by LDs with wavelength longer than1010 nm is proposed. An oscillating-amplifying integrated laser was built, and 2.05 kW output laser with beam quality M2 of 1.7 was realized when the fiber laser was pumped by 1010 nm LDs with maximum pump power of 2.56 kW. In the future, fiber laser with higher output power and better beam quality can be realized by increasing the pump power and optimizing the fiber characteristics.

Simulation of light field regulation based on micro-nano structure and material properties
Zheng Xinzhi, Dou Shiji, Liu Xiang, Zhao Chenxi, Zhao Shilong, Yang Yue, Wang Shaoyi, Zhao Zongqing, Ma Yujie
2024, 36: 031002.   doi: 10.11884/HPLPB202436.230453
[Abstract](58) [PDF 11758KB](19)
Abstract:
The finite-difference time-domain algorithm (FDTD) was used to simulate the optical field distribution of the micro-nano structure target, explore the optical transmission mechanism in the micro-nano structure target, and analyze the influence of material properties and structural parameters on the optical transmission characteristics and optical field distribution. Based on the simulation results of optical field distribution and evolution, the laser transmission characteristics in the nano-wire and nano-pore array targets of semiconductor alumina, insulator silicon dioxide and metal copper with different electrical conductivity are compared, and the modifications of optical field distribution during optical transmission are analyzed. The results show that the optical transmission characteristics and optical field distribution in the target can be modulated by changing the diameter and spacing of the holes (nanowires) in the target structure, and the optical field can be periodically oscillated between the dielectric material and the vacuum region, or transmitted in a stable state. When the laser is transmitted in the copper nanopore array, the light transmittance increases with the increase of the hole radius. Based on the simulation results of light field distribution and evolution, the laser transmission properties of different materials and micro-nano structure targets are compared, the physical images and corresponding phenomena are given, and the micro-nano structure target design is given according to the requirements of light field regulation.
Performance research and parameter optimization of 15 nm Bulk nFinFET device
Hou Tianhao, Fan Jieqing, Zhao Qiang, Zhang Fang, Hao Jianhong, Dong Zhiwei
2024, 36: 031003.   doi: 10.11884/HPLPB202436.230169
[Abstract](78) [PDF 4224KB](36)
Abstract:
Due to the growing severity of the short-channel effect in semiconductor devices, a new type of device, the FinField-Effect Transistor (FinFET), has been proposed, developed and applied. This paper aims to establish a 15 nm n-type Bulk FinFET device model to investigate the impact of basic structural parameters, device temperature, and gate material on the performance of Bulk FinFETs. Simulations are conducted to analyze the effect of different gate lengths, fin widths, fin heights, channel doping concentration, device operating temperature, and gate materials on the performance of FinFETs. The results show that increasing the gate length, decreasing the fin width, and increasing the fin height can effectively suppress the short-channel effect. Moreover, the channel doping concentration below 1×1017 cm−3 has little effect on the device characteristics, while high doping concentration causes device failure. Additionally, increasing the operating temperature leads to device performance degradation. Finally, using high K dielectric material as the gate material is found to enhance device performance compared to using conventional SiO2 material.
Ion Beam Science and Technology and Its Applications
Effect of laser on the stopping power of a large range energetic Carbon ion in a two-component plasma
Yi He, Wang Guiqiu, Wang Shixuan, Gao Xin, Liu Dajun
2024, 36: 034001.   doi: 10.11884/HPLPB202436.230200
[Abstract](55) [PDF 1015KB](22)
Abstract:
This paper, studies the influence of laser on the stopping power of a carbon ion in a two-component plasma, with emphasis on the effects of different laser amplitude, laser frequency, laser angle, plasma density, and plasma temperature on the stopping power based on the linearized Vlasov-Poisson model and molecular dynamics simulation. The research results show that the influence of laser on stopping power is very obvious in all the projectile region. In the low energy region (the magnitude of incident velocity is 0-0.1 plasma electron thermal velocity), the energy loss of the carbon ion mainly comes from the contribution of ions in the plasma, especially when the incident velocity is around the plasma ion thermal velocity, the first peak of stopping power occurs. In the medium and high energy region (the magnitude of incident velocity is greater than 0.1 plasma electron thermal velocity), the energy loss of the carbon ion mainly comes from the contribution of electrons in the plasma, especially when the magnitude of incident velocity is around 1.5 times the plasma electron thermal velocity, the second peak of stopping power occurs. The bimodal structure of the stopping power of the carbon ion in the plasma reflects the contribution of ions and electrons to the stopping power in different energy regions. On the other hand, the increase of laser intensity or laser frequency can decrease the stopping power of the carbon ion. The stopping power will be enhanced with the increase of plasma density or the decrease of electron temperature. Such an enhancement is more significant for stopping power for the low energy peak caused by ions compared to high energy peak caused by electrons.
Design and implementation of scanning magnet power supply based on PREF
Fan Qi, Zang Hang, Guo Qi, Yan Hongbin, Shi Chengcheng, Shangguan Jingbin, Zhang Yun
2024, 36: 034002.   doi: 10.11884/HPLPB202436.230289
[Abstract](52) [PDF 3233KB](19)
Abstract:
The PREF device is a 10−60 MeV proton synchrotron jointly designed and built by Xinjiang Institute of Physics and Chemistry, Chinese Academy of Sciences and Institute of Modern Physics, Chinese Academy of Sciences, which is the only dedicated device for displacement damage effect simulation test in China. For the technical requirements—the output current frequency of the scanning magnet power supply is 200 Hz, and the tracking error is less than ≤±5×10−3—of the device, three stage H-bridge series topology schemes are adopted, and the technical requirements are realized based on pulse width modulation through phase shift control. Simulation and test results show that the power supply can output high precision triangular wave current with peak-to-peak value of ±420 A, continuously adjustable amplitude and frequency to meet the requirements of engineering applications.
Particle Beams and Accelerator Technology
Small sized bremsstrahlung conversion target
Jing Xiaobing, Shi Jinshui
2024, 36: 034003.   doi: 10.11884/HPLPB202436.230271
[Abstract](93) [PDF 1124KB](32)
Abstract:
The paper aims to reduce the lateral size of the X-ray source in a linear induction accelerator and design a bremsstrahlung conversion target. Analyzing the trajectory of the electron beam during the focused shooting process, it is pointed out that the distribution of the same electron beam trajectory can be described as either the transverse broadening of the electron beam at a certain longitudinal position or the axial distribution broadening when the electron beam maintains a small transverse size. Therefore, the concept design of a small-sized multi-layer target with multiple small targets placed near the waist to effectively block the focused electron beam is proposed. The EGS4 program was used to calculate the X-ray yield, and it was found that the change in X-ray yield was relatively small when the target thickness changed within a certain range. Based on this rule, the structural design of a small-sized multi-layer target was completed. Further investigation was conducted on a design application example. When the minimum envelope diameter of the focused electron beam is 3 mm and the convergence angle is 100 mrad, compared to large-sized targets, using a designed small-sized multi-layer target can obtain an X-ray light source with an equivalent diameter reduction of about 50% and a yield reduction of about 10%. By adopting the proposed design method, it is expected to obtain X-ray light sources with lateral dimensions smaller than the minimum envelope size of the electron beam under the same electron beam quality and focusing conditions, which has certain application value.
Development of the NFTHz accelerator beam profile measurement system
Zhu Wenchao, Wei Zhengyu, Xie Chunjie, Zhou Zeran, Wang Lin, Liang Yu
2024, 36: 034004.   doi: 10.11884/HPLPB202436.230361
[Abstract](41) [PDF 2522KB](17)
Abstract:
The “Composite Light Source” project of the National Synchrotron Radiation Laboratory, Terahertz Near-Field High-Flux Material Property Testing System, consists of an approximately 3-meter electron linear accelerator. To characterize the performance of the accelerator and monitor the status of the beam, it is necessary to measure the beam size. Specifically designed for the terahertz linear accelerator, a beam size measurement system based on the EPICS distributed system has been developed. A beam spot detector is taken for the conversion of the beam spot into an optical spot and a remote mirror is taken to image the optical spot onto a CCD camera for image acquisition. Subsequently, the camera-captured image data is integrated into the EPICS database using ADAravis. Due to the dark current and radiation environment, salt-and-pepper noise is present in the acquired images. Therefore, a Convolutional Neural Network (CNN) is employed to suppress the salt-and-pepper noise in the images. Finally, Gaussian fitting is applied to calculate the beam cross-sectional dimensions from the images. The experimental results indicate that the CNN can effectively eliminate salt-and-pepper noise, and the resolution of this system is 15.8 μm, which satisfies the design requirement.
Pulsed Power Technology
Optimization of tetracycline degradation by nanosecond pulsed gas-liquid discharge with needle-water configuration
Chen Pengju, Zhou Zikai, Wang Sen, Fang Zhi
2024, 36: 035001.   doi: 10.11884/HPLPB202436.230270
[Abstract](62) [PDF 1875KB](19)
Abstract:
Water pollution caused by the overuse of antibiotics poses a major threat to the natural environment and human health. As a green and environmentally friendly advanced oxidation technology, low-temperature plasma is considered to be one of the most promising antibiotic degradation methods, but it needs to be further improved in terms of degradation efficiency and energy efficiency. In this study, transient spark discharge was obtained by using nanosecond pulse power supply with a needle-water electrode configuration, and applied to tetracycline degradation in water. The effect of pulse voltage, frequency, initial concentration, initial pH value on tetracycline degradation was studied, and the results show that the degradation rate of tetracycline was the highest under the condition that the initial concentration was 50 mg/L, the pulse voltage was 9 kV, the frequency was 2 kHz, the initial pH is neutral, and the degradation rate reached 91.6% when the processing time was 10 min. The energy efficiency and electrical energy per order are 0.165 g·kW−1·h−1 and 0.78 kW·h·m−3, respectively. Free radical quenching experiments showed that hydroxyl radicals (·OH) played a major role in the degradation of tetracycline, while H2O2 and O3 played a slightly weaker role. Cytotoxicity experiments also showed that the toxicity of the solution decreased significantly after 10 min of gas-liquid discharge treatment.
Research on two-channel high-voltage pulse generator with reverse bias voltage
Li Zi, Zhang Di, Jiang Song, Wang Yonggang, Rao Junfeng
2024, 36: 035002.   doi: 10.11884/HPLPB202436.240003
[Abstract](91) [PDF 2050KB](29)
Abstract:
The influence of electric field penetration on mass spectrometer can be improved by adjusting the reverse bias voltage to improve the resolution of mass spectrometer. To meet the different output waveform requirements of mass spectrometers, this paper proposes a pulse generator that can simultaneously output two pulses of the same voltage amplitude and with opposite polarities, and a negative DC bias voltage is coupled to the high-voltage positive pulse. Only one charging power source is needed to generate both positive and negative pulsed electric fields. This paper analyzes the synchronous driving effect of the series switch, and then solves the problem of uneven charging voltage of the series capacitors by adding the compensation windings and parallel resistors. The difference of charging voltage between four capacitors is within 0.1%. A 4-stage prototype was constructed. This pulse generator can generate a high-voltage positive pulse with amplitude from 0 to 1.5 kV and adjustable pulse width from 2 to 10 µs and coupled with a negative bias voltage with amplitude from 0 to −200 V, and a high-voltage negative pulse with amplitude from 0 to −1.5 kV and adjustable pulse width from 2 to 10 µs. All the rising edges are shorter than 30 ns. The pulse generator can achieve adjustable output voltage, pulse widths and frequencies.
Study of low-jitter laser-triggered pseudo-spark switches
Yang Mingjie, Yang Hongfei, Zhang Ming, Qu Bo
2024, 36: 035003.   doi: 10.11884/HPLPB202436.240033
[Abstract](58) [PDF 1117KB](23)
Abstract:
Pseudo-spark switches have been successfully used in a variety of pulsed power applications, including the European Large Hadron Collider, anti-missile radar systems, and aero-engine ignition. For such applications, it is important to reduce the delay and jitter of the switch to improve stability. In this paper, a laser-triggered pseudo-spark switch is designed using a laser with a wavelength of 532 nm, and the anode firing delay time and jitter of the laser-triggered pseudo-spark switch are tested under different air pressures, operating voltages, and triggering energies. The test results show that increasing the laser energy can reduce the delay and jitter of the switch, and the laser energy threshold of 1.5 mJ for switch stability can make the jitter of the switch less than 1 ns, and the delay and jitter of the switch no longer change significantly with continuing increase of the trigger energy; in addition, increasing the hydrogen pressure inside the tube can reduce the delay and jitter of the switch; when the trigger energy is large enough, changing the anode voltage does not change the delay and jitter of the switch.
Nuclear Science and Engineering
Development of mechanical property analysis program for space thermionic fuel element
Yang Wenyu, Chai Xiang, Zhu Enping, Liu Xiaojing
2024, 36: 036001.   doi: 10.11884/HPLPB202436.230388
[Abstract](55) [PDF 4751KB](15)
Abstract:
To predict the safety performance of fuel elements during operation of a space thermionic reactor, this study developed a mechanical performance analysis program for fuel elements, and conducted high-precision simulation of stress, strain, and geometric deformation for the multi-layer cylindrical TOPAZ-II thermionic fuel element. The program takes into account the irradiation swelling of nuclear fuel under high-temperature radiation environment, and analyzes the mechanical response of the fuel pellet-emitter after contact, thereby quickly and accurately solving the mechanical state of the fuel pellet and emitter, to provide accurate prediction of the performance during operation of the space thermionic reactor. The results indicate that in normal operating conditions, the fuel of a space thermionic reactor undergoes significant swelling effects, which causes deformation that can lead to potential safety hazards such as reduced thermal-electric conversion efficiency and component failure.
Research on diagnosis of fuel defects in operating pressurized water reactors
Fu Pengtao, Zhang Anlong, Gu Peiyong
2024, 36: 036002.   doi: 10.11884/HPLPB202436.230387
[Abstract](54) [PDF 1241KB](22)
Abstract:
Fuel cladding is the first barrier to confine the radionuclides produced in the reactor core. Once the fuel rods defect, fission product activity in the primary loops will increase and may lead to temporary shutdown of the reactor when fuel rod failure has deteriorated to certain levels. This paper introduces the theoretical mechanism of production and migration of fission product from defective fuel rods to the primary loops in the operating pressurized water reactors. The analytical solution of fission product concentration in primary loops is got based on the first-order differential equations for steady operation. Based on the release-to-birth ratios for recoil and diffusion by least squares method, a method is developed to diagnose the status of fuel failure in pressurized water reactors, including fuel failure time, the degrees of defect size, the disseminated actinides, the average burnup and the fuel batch. The prediction results of fuel failure are verified well with that of a typical fuel failure with secondary degradation in one commercial pressurized water reactor, as well as those of the sipping test and the post irradiation examination.
Advanced Interdisciplinary Science
Characteristic analysis of P-SP topology wireless power transfer system based on parity-time-symmetric principle
He Xiyu, Guo Feng, Xu Xingpeng
2024, 36: 039001.   doi: 10.11884/HPLPB202436.230356
[Abstract](52) [PDF 2437KB](20)
Abstract:
The parity time (PT) symmetry principle has been proved to be a powerful tool to improve the degree of freedom of wireless power transfer (WPT) systems. However, the operating range of the P-P (parallel-parallel) topology WPT system based on the PT symmetry principle is still limited. To solve this problem, a P-SP (series-parallel) compensated WPT system based on PT symmetry principle is proposed. The circuit model of the system is simplified by the equivalent circuit method, and the influence of the capacitance distribution ratio on the oscillation frequency, the critical coupling coefficient, the coupling coefficient satisfying the system entering the PT symmetric region, the load resistance range and the transmission efficiency is analyzed by the coupled mode theory. A prototype is built to carry out experiments to test the applicability of the proposed method. The results show that the transmission distance can be expanded from 110 mm to 210 mm with only 2% loss of system transmission efficiency. Hence, preparations are made to expand the application scope, increase application scenarios, and optimize the working performance of the sending and receiving module units in the laser wireless charging system.