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:
Enhancement of underwater shock wave generated by exploding-wire-initiated reaction of aluminum powder suspension
Yuan Wei, Han Ruoyu, Li Chen, Wang Ya’nan, Zhang Yongming
 doi: 10.11884/HPLPB202234.220008
[Abstract](0) [PDF 4328KB](0)
Underwater electrical wire explosions detonating energetic materials can generate stronger and more controllable shock waves (SW), and is considered an important direction for the development of controllable shock wave technology. Compared with other energetic materials, the liquid-phase aluminum powder suspension has more advantages in terms of safety and uniformity that is easy to obtain and has a high reaction heat. It has great potential for civil applications. This paper reports an experimental study on the detonation of aluminum powder suspension by underwater electrical wire explosion. The aluminum powder suspension was confined in a plexiglass tube and passed through a 200 μm metal copper wire in the coaxial direction. After being driven by a high-voltage pulse source, it rapidly phased Transformation and explosion provide reaction conditions for aluminum powder. By comparing the discharge parameters and SW pressure signals of different quality aluminum powder suspensions the electric explosion-driven aluminum powder discharge characteristics and the law of SW enhancement effect are obtained. The experiment found that SW has two obvious peaks, which correspond to the evaporation SW (the first peak) and the breakup of the tube (the second peak). The effect of aluminum powder deflagration on the second SW is very significant. In the 300 mg aluminum powder suspension environment, the peak value of the second SW reaches 2.77 MPa, increased by 2.25 times compared to an optimal underwater electrical wire explosion, and the impulse of the SW is increased by about 50%. This paper also compares the SW signals in the suspension environment of 200 mg aluminum powder under different energy storage. It is found that with the increase of energy storage, both of two peaks of SW increase, reaching 3.17 MPa and 1.91 MPa respectively at 600 J. the impulse of SW also increases with the increase of energy storage. The impulse at 600 J energy storage is 41.12 Pa·s, which increased by 2 times compared to that at 300 J energy storage.
Fast calculation of polishing powder sedimentation characteristics in magnetorheological polishing area under gradient magnetic field based on Kahan linearization
Yang Hang, Zhang Shuai, Zhang Yunfei, Huang Wen, He Jianguo
 doi: 10.11884/HPLPB202234.21353
[Abstract](4) [PDF 6537KB](0)
The sedimentation characteristics of the magnetic polishing liquid in the magnetorheological polishing area is an important part of the material removal mechanism in the polishing process. Aiming at the ultra-large-scale nonlinear problem of numerical calculation of polishing powder sedimentation characteristics, this paper solves the ultra-large-scale fluid-structure interaction calculation problem based on Kahan linearization. The sedimentation characteristics of the multiphase flow of polishing powder composed of hydroxy iron powder and silicone oil in the polishing area under gradient magnetic field were studied. Taking the polishing powder composed of hydroxyl iron powder with mass fraction of 70% and particle size of 5um and silicone oil with viscosity of 0.973 Pa·s as the research object, different polishing wheel rotation speeds, different embedding depths and different mass fractions of carbonyl iron powder were realized. Analysis of the settlement law in the case. It is found that the polishing powder in the magnetorheological polishing area will increase with the increase of the rotating speed of the polishing wheel; when it reaches the outlet, the distribution of the polishing powder tends to be stable; the polishing powder will increase with the increase of the embedded depth and there is a saturation zone ; The mass fraction of hydroxy iron powder affects the sedimentation ability in a non-linear manner.
Study on preheating ablative effects of two-mode Rayleigh-Taylor instability
Kuang Yuanyuan, Lu Yan
 doi: 10.11884/HPLPB202234.220133
[Abstract](7) [PDF 3138KB](0)
Aiming at the growth of ablative Rayleigh-Taylor instability with two perturbations, the evolutions of the amplitudes of high-order harmonics excited by two-mode coupling under different preheating conditions are studied by using a high-precision numerical simulation method. When the fundamental modes area long-wavelength and a short-wavelength mode, the long-wavelength modes of the excited harmonics are dominant, while the development of short-wavelength modes are obviously suppressed; when the fundamental modes are two short-wavelength modes, many fast-growing and long-wavelength modes are excited, and the growth of short-wavelength modes are in the form of small oscillation. By comparing the two different two-mode coupling cases, it is found that the long-wavelength structures are dominant in the weakly nonlinear stage. Especially, in the two short-wavelength modes coupling case, the bubbles and spikes show a long-wavelength structures which are different from the two fundamental modes. By further comparing the three preheating ablative effects, it is found that the stronger the preheat degree is, the more the coupled harmonics growth will be weakened. It is of great significance to control the development of ablative Rayleigh-Taylor instability in inertial confinement fusion engineering.
Optical component damage monitoring method based on acoustic emission
Hong Mengjun, Zhang Junwei, Xu Zhenyuan, Li Yuhai
 doi: 10.11884/HPLPB202234.220031
[Abstract](10) [PDF 5988KB](0)
Optical component damage is one of the important factors that limit the improvement of laser flux level. In order to quickly and accurately detect whether optical component damage occurs and support the use of optical component cycle repair strategy, an optical component damage detection method based on acoustic emission technology is studied and proposed. By studying the characteristics of acoustic emission signals generated by optical component damage, whether the optical component is damaged is judged. A time delay estimation algorithm based on quadratic correlation and fine interpolation of correlation peak (FICP) is developed. The feasibility of the algorithm is verified by simulation. Combined with the principle of time difference location, a method for solving the damage location is established and verified by experiments. The results show that the method can quickly obtain the damage location estimation from the monitoring signal. The average positioning error is 8.61 mm, and the calculation time is 0.143 s/time. It has application potential for on-line damage monitoring of large-aperture optical components.
Preliminary investigation of the separation in a twisted flow aerosol singlet oxygen generator
Xu Xiaobo, Hu Dapeng, Deng Liezheng, YuYang, Chen Wenwu, Jin Yuqi
 doi: 10.11884/HPLPB202234.220052
[Abstract](13) [PDF 13915KB](0)
Gas-liquid separation is the key to the success of an aerosol-type singlet oxygen generator. To solve the problem of gas-liquid separation, the idea of droplet size-controlled centrifugal separation was proposed that size-controlled droplets are produced by using an atomization technique and then during the reaction of the droplets with gas flow the gas-liquid separation is simultaneously done by a centrifugal force which is determined by the sizes of the droplets and generated by a set of high-speed rotating blades. To verify this idea, a twisted flow aerosol singlet oxygen generator (TFA-SOG) based on this idea was built and investigated through simulation and experiment. The investigation shows that the simulated gas-liquid separation efficiencies are consistent with the experimental onesand the idea is feasible; the research emphasis of the next development for TFA-SOGs should be put on the droplet size-controlled atomization technique.
Electromagnetic pulse crimping device and experiment of high-voltage wire harness for electric vehicles
Li Chengxiang, Shen Ting, Zhou Yan, Wu Hao, Zhang Bingfei, Mi Yan
 doi: 10.11884/HPLPB202234.210568
[Abstract](12) [PDF 7441KB](1)
The use of aluminum alloy high-voltage wire harnesses instead of copper wire harnesses can reduce the weight of electric vehicles, increase battery endurance, and reduce cost. Aiming at the difficulty of reliable and effective connection between aluminum alloy high-voltage wire harness and copper alloy terminal, this paper proposes to use electromagnetic pulse crimping technology (EMPC) to connect aluminum alloy high-voltage wire harness and copper alloy terminal. A set of EMPC device suitable for the connection of high-voltage wire harness and terminal has been developed. The EMPW device has a maximum discharge energy of 28 kJ. During the crimping process, with the increase of the discharge voltage, the temperature of the terminal surface increases. The aluminum alloy high-voltage wire harness and the copper alloy terminal can be realized reliably at 12 kV. An optical microscope was used to analyze the microstructure of the connection interface, and electrical properties and mechanical properties has been tested. The analysis results show that the electromagnetic pulse crimping technology can realize the metallurgical combination between the aluminum alloy high-voltage wire harness and the terminal as well as the aluminum alloy core wires. The connection interface has a corrugated morphology and a vortex morphology. The test results show that the contact resistance, vibration test and tensile load test of the joint meet the industrial standards of automobile and the national standards of cable joint. The research results of this paper can provide a scientific and technical foundation for the replacement of copper alloy high-voltage wiring harness with aluminum alloy.
Development of a fully automated magnetic field measurement and shimming platform for small cyclotrons
Guan Leilei, Li Ming, Cui Tao, Jia Xianlu, Zhang Tianjue, An Shizhong, Huang Peng, Wang Fei
[Abstract](14) [PDF 3429KB](0)
In response to the demand for PET medical radionuclides in nuclear medicine diagnosis and treatment, China Institute of Atomic Energy is conducting research on the industrialization of PET medical small cyclotrons. Magnetic field measurement and shimming are key point in the production of cyclotrons. The compact structure of small cyclotron is a difficulty to realize the full automatic control of magnetic field measuring instrument and solving the problems of high processing cost and long cycle of conventional shimming method is the key to industrialized production. This article will introduce in detail the development of a fully automated magnetic field measurement and precision shimming platform for small cyclotrons. Through the magnetic field measurement and shimming practice of multiple small cyclotrons, a set of rapid magnetic field measurement and shimming procedures will be developed to realize fully automatic measurement method to shorten the magnetic field measurement cycle and reduce the times of shimming by precision shimming algorithm. Under the condition of ensuring the high efficiency and high quality of magnetic field measurement and shimming, the time and processing cost are greatly reduced, which lays a foundation for the industrialized production of small cyclotrons. At present, the China Institute of Atomic Energy has completed the commercialization of several small cyclotrons.
Empirical formula of breakdown electric field and time delay for SF6 gas switch under nanosecond pulse and hundreds of kV/cm electric field
Guo Fan, Jia Wei, Xie Linshen, Chen Zhiqiang, Wu Wei, Xie Yanzhao
 doi: 10.11884/HPLPB202234.210538
[Abstract](18) [PDF 12649KB](2)
There are significant differences between the calculation results and experimental results by using J. C. Martin empirical formula to estimate the breakdown electric field for hundreds of kV/cm electric field and nanosecond pulse. In order to improve the design of pulsed gas switch and adjustment of working conditions, the relationships between the breakdown electric field and time delay and the experimental parameters based on the classical empirical formula have been established. The empirical formula of breakdown electric field and time delay for SF6 gas switch under nanosecond pulse and hundreds of kV/cm electric field have been present. It has been indicated that slope of pulse will affect the breakdown characteristics of nanosecond pulse in high electric field and the breakdown electric field is correlated with the breakdown time delay. The differences between the calculation results and experimental results are caused by the experimental conditions. The fitting expression of empirical formula can give more guidance for the design of output switch in the electromagnetic pulse simulator.
Peking University DC-SRF-II photoinjector drive laser system
Feng Liwen, Wang Tianyi, Jia Haoyan, Liu Zhongqi, Xu Hang, Huang Shenlin, Liu Kexin
 doi: 10.11884/HPLPB202234.210343
[Abstract](24) [PDF 0KB](0)
A new drive laser system had was developed to meet the requirement of DC-SRF-II photoinjector in Peking University. This modular drive laser system can be operated from single pulse to 81.25 MHz CW mode, with green light output power 1.41 W @ 1 MHz. Longitudinal and transverse shaping were also implemented in the system, resulting in near flat-top 18 ps laser pulse with cut-Gaussian transverse profile. Measurement shown the system output power stability is 1.8% RMS, and pointing stability less than 1 μrad.
Low-energy pulsed spark discharge characteristics of pin-plate structure in water
Wang Zhi, Han Ruoyu, Li Xiandong, Chen Pengyu, Li Yizhang, MiaoJinsong
 doi: 10.11884/HPLPB202234.220022
[Abstract](11) [PDF 8173KB](2)
The influence of electric pulse parameters pulse width on spark discharge characteristics in water was studied. A solid-state repetitive nanosecond pulse power supply with adjustable parameters was adopted. The discharge load is a pin-plate structure placed in water (the distance between the pin and the plate is 1 mm). The experiment is carried out under low repetitive frequency conditions (approximately 5Hz). The characteristics of pulse discharge in water were obtained by monitoring discharge parameters, taking high-speed shadow images, collecting optical emission spectrum, and measuring sound pressure. And the evolution of pulse discharge with different parameters and its influence on acoustic and spectral characteristics were also obtained. When the energy storage on the order of a few joules, after the initial discharge channel is formed between the two electrodes, the circuit current rises to approximately 10 A within a few hundred ns, followed by a rapid and then slow decline with a duration of 50−60 μs. It is found that the preset pulse width has a great influence on the spark discharge characteristics. Under short pulse width conditions, the discharge channel will be cut off by the solid-state switch of the power supply. Under long pulse width conditions, the discharge channel becomes unstable in the late stage and even interrupts the arc,and the secondary discharge appears in bubbles. The radiation spectrum revealed more information. With the increase of pulse width, the intensity of thecharacteristic spectral lines increased, but no new spectral lines were observed. This indicated that the number of active particles increased, and the type of them remain the same.The channel electron density was estimated on the order of 1018 cm−3. The characteristic width of the pulse sound waveproduced by a short pulse (<150 μs) is 110−150 μs. However, when the pulse width continues to increase, the pulse width does not continue to increase but remains the same (150 μs). We hope that this research have a certain reference value on the mechanism of small energy spark discharge, and provide ideas for the application of underwater acoustics, liquid phase plasma and other fields.
Experimental research on influencing factors of temperature stratification in suppression pool
Guo Rongda, Zhang Dandi, Cao Xuewu
 doi: 10.11884/HPLPB202234.220084
[Abstract](30) [PDF 1055KB](4)
For small modular reactors, containment suppression devices can be used to limit the rapid increasement of temperature and pressure in the containment caused by LOCA accident. However, temperature stratification may occur in the suppression pool with the change of the mass flow flux and water temperature during the process of discharge, which reduces the heat and mass transfer. In this paper, an experimental facility for temperature stratification of suppression pool is established. The effects of steam mass flow flux, submerged depth of sparger and gas-water volume ratio on the temperature stratification characteristics in the pool are studied. Results show that there is temperature stratification in the pool at a wide range of steam mass flow flux. With the increase of mass flow flux, the influence on stratification is weakened, and the thermal interface moves down, leading to more water participating in heat exchange. With the increase of the submerged depth of sparger, the position of thermal interface moves down and the stirring effect of water is enhanced. As the gas-water volume ratio increases, the thermal interface moves down and the disturbed area enlarges.
Monte Carlo simulation of neutron capture γ-rays from nitrogen in the atmosphere
Liu Li, Zuo Yinghong, Niu Shengli, Zhu Jinhui, Li Xiazhi
 doi: 10.11884/HPLPB202234.220055
[Abstract](12) [PDF 1246KB](3)
Neutron capture γ-rays from Nitrogen is an important part of initial nuclear radiation. In order to accurately calculate the early nuclear radiation, the Monte Carlo computing model of the neutron and secondary γ-rays transport in the atmosphere is established. Some variance reduction techniques, such as geometric splitting algorithm and time splitting algorithm are used in the Monte Carlo method to improve computing efficiency. The neutron and secondary γ-rays information on the spherical surface at different distances are calculated. The energy release rates of capture γ-rays from Nitrogen at different positions and at different times are given. The regularity of the energy release rate of capture γ-rays from Nitrogen is studied, and the influence of neutron energy on capture γ-rays from Nitrogen is analyzed. The results show that the energy release rate of capture γ from Nitrogen increases with the increase of source distance at first, reaches the peak at about 500 m from the source, and then decreases exponentially with the increase of distance. The energy release rate of capture γ-rays from Nitrogen obeys exponential decay law in time, and the decay time is about 0.1 s. By introducing the parameter of a representing the radiation intensity and the characteristic attenuation time parameter of τ, a fast calculation formula for the energy release rate of capture γ-rays from Nitrogen at different distances and times is obtained by fitting formulas. Results show that the intensity radiation, the decay time scale of capture γ-rays from Nitrogen and their spatial distribution are closely related to neutron energy.
Current measurement for LTD single branch verification device
Wei Bing, Wang Jie, Li Yuan, Li Feng, Chen Lin, Zhou Liangji, Guo Fan, Yuan Jianqiang
 doi: 10.11884/HPLPB202234.210519
[Abstract](27) [PDF 4886KB](2)
In order to measure the transition section and outlet current of LTD single branch verification device, a B-dot current probe is designed and calibrated. The radial transmission line is used to calibrate the current probe offline, and the corresponding verification experiments are carried out to verify the effectiveness of the calibration. The experimental results show that the sensitivity deviation of the probe is about 1% due to the errors of probe installation depth and angle. When the distance between cathode and anode is greater than the diameter of probe hole, the B-dot calibration result is independent of the distance between cathode and anode. For the coaxial transmission line with large diameter involved in the device, the simulation and calibration results of radial transmission line are effective. According to the experimental results of LTD single channel verification device, the difference of anode current from the four transition sections to the outlet is very small, while the cathode current gradually decreases.
Simulation of the temperature and thermal deformation of anode targets in high-current diodes
Hu Yang, Cai Dan, Sun Jiang, Zhang Jinhai, Yang Hailiang, Sun Jianfeng, Yin Jiahui, Hu Yixiang
 doi: 10.11884/HPLPB202234.210442
[Abstract](15) [PDF 2508KB](1)
The thermal-mechanical damage induced by high current pulsed electron beam striking on anode targets is a key factor affecting the stability and lifetime of high current diodes. This problem is mostly addressed by replacing the anode target and cleaning the cavity and cathode to ensure the normal operation of the diode. In this paper, a diode anode target temperature and thermal deformation simulation method is established using the energy deposition profile of the electron beam in the target as a bridge. The method can be used to determine the temperature distribution and thermal deformation of the target under various diode operating conditions, provide basic data for the investigation of thermal-mechanical damage to the target, and provide technical support for diode configuration design and life enhancement. Apply this method to the “Qiangguang-I” accelerator, the simulation results with show that the surface temperature of the target can reach 5500~6000 ℃ and the thermal deformation can reach about 4.5 mm when the ion density is more than 1014 cm−3 (tight-pinched). The temperature is about 4500 ℃ and the thermal deformation is 2.8~3.2 mm when there is no ion flow (weak-pinched).
Influence of energy spread on the transverse profile of the focused electron beam
Wang Ke, Dai Zhiyong, Xia Liansheng, Zhang Huang, Li Jin, Fan Peiliang, Yang Zhiyong
 doi: 10.11884/HPLPB202234.210450
[Abstract](23) [PDF 1079KB](5)
A brief introduction to evaluating the beam size with the Root-Mean-Square (RMS) value, the Full-Width-Half-Maximum (FWHM) value and the Modulation-Transfer-Function (MTF) value is given in this paper. The focusing of the long pulse electron beam (~100 ns) in an induction linear accelerator is studied by both theoretical analysis and numerical simulation, the contribution of the energy and current difference of the rising edge and the falling edge to the final beam size are discussed. In our results, the rising edge and the falling edge of the beam with large energy deviation may lead to a significant increase of the beam size, especially the MTF beam size, i.e. the FWHM beam size is increased by about 9% while the MTF beam size is increased by about 24%.
Analysis of calibration schemes for CSNS quadrupole
Ma Na, Li Bo, Dong Lan, Wang Xiaolong, Men Lingling, Wang Tong, Liang Jing, He Zhenqiang, Ke Zhiyong, Lu Shang, Han Yuanyin, Yan Luping, Zhang Luyan, Yan Haoyue
 doi: 10.11884/HPLPB202234.210512
[Abstract](16) [PDF 3365KB](2)
The precise alignment of the devices can ensure the accelerator stable operation. Excessive deviation tend to result in excessive divergence of beam produced by the accelerator, reduction of the beam’s energy, and even damage to the small-aperture devices, which directly affects the operation of the devices. The precise alignment of the devices is closely related to the calibration about determination of the center of the devices, the accuracy of the tunnel control network and the adjustment of the tunnel, among which the calibration using the center of the devices as datum should be considered firstly. This paper focuses on the calibration of the quadrupole of CSNS about determination of the center of the devices, analyzes the standard deviation values of magnetic center and rotation center obtained by the magnetic measuring platform, and the one of rotation center and mechanical center after the calibration of each magnet twice. The results show that the standard deviation of magnetic center and rotation center of the quadrupole obtained by the magnetic measuring platform is 0.1 mm, the repeatability accuracy after calibration of rotation center and mechanical center of the CSNS quadrupole twice is within 0.03 mm, and he standard value of the deviation between the rotation and the mechanical center is 0.1 mm. So if the magnet center cannot be carried out to calibration of similar devices of the same accuracy, the calibration based on rotation center instead of mechanical center, with deviation correction of rotation center and magnetic center, can meet the accuracy requirements of the alignment of current equipment alignment. This study provides important reference and guidance for the calibration of similar devices in the future.
Simulation and experimental research of pulse transformer reset system based on energy recovery principle
Wang Qingfeng, Che Yongwang, Li Xiangqiang, Zhang Jianqiong, Tang Xianfeng
 doi: 10.11884/HPLPB202234.210432
[Abstract](15) [PDF 6144KB](1)
In order to improve the core utilization rate of pulse transformer in pulse power system, a pulse transformer reset system based on energy recovery principle is proposed. Firstly, according to the magnetic core hysteresis loop, the change process of the magnetic induction intensity of the reset system based on the energy recovery principle in one cycle is analyzed, and the solution formulas of the pulse transformer excitation current and reset capacitor voltage in different stages are deduced. A simulation model of the pulse transformer reset system based on the energy recovery principle is established, and the correctness of the theoretical analysis and solution formula of the reset system is verified by the simulation results. On this basis, a pulse modulator test platform based on pulse transformer boosting and energy recovery reset system is constructed. The excitation currents of the pulse modulators with reset system and without reset system are compared under the same pulse width. The results show that the reset system pulse modulation can effectively improve the utilization of the magnetic core. The repetition frequency experiment is carried out on the pulse modulator with reset system, and the results show that the reset system can realize the stable operation of 1 kHz repetition frequency.
Method for identifying TE11 mode in TM01/TE11 mixed mode system with eight-hole coupler
Ren Jie, Weng Ming, Lei Le, Lin Shu, Cao Meng, Zhai Yonggui
 doi: 10.11884/HPLPB202234.220040
[Abstract](33) [PDF 846KB](2)
In this paper, based on high power microwave transmission systems, in order to improve power capacity and efficiency, over-mode waveguides are often used, so the mixed modes of TM01 and TE11 often appear in circular waveguides. The method of extracting the mixing ratio and polarization angle of the TE11 mode is analyzed and studied by using an 8-hole circular waveguide coupler with uniform angular distribution. The electric field distribution of the TM01 and TE11 modes in the circular waveguide at the coupling hole is analyzed, and the output power of each coupling hole is simulated by CST. By obtaining the average power of the coupling holes facing each other and the average power of the eight holes we can get the conclusion that the ratio is independent of the phase difference between the modes. At the same time, it is found that the ratio is linearly related to the mixing ratio of the TE11 mode, and the proportionality coefficient in the linear relationship is a linear function of the polarization angle. Expressions for calculating the TE11 mode mixing ratio and polarization direction were obtained by linear fitting. Compared with the parameters set by the simulation, the results calculated by this expression show that when the mixing ratio of TE11 mode is less than 30%, it is feasible to use it to calculate the mixing ratio and polarization angle of TE11 mode, and the error does not exceed 10%. On this basis, this paper presents a specific method for judging TE11 mode information in practical situations.
Cold test and beam commissioning of alternating-phase-focused drift-tube-linac
Xie Xiucui, Pu Yuehu, Zhao Zhentang
 doi: 10.11884/HPLPB202234.220014
[Abstract](24) [PDF 17801KB](4)
Linac injector is a major sub-system of the proton therapy facility. Due to schedule consideration, the Shanghai advance proton therapy facility APTRON use a linac injector that made by ACCSYS in California, USA. Therefore, we develop a linac injector that made up by Electron Cyclotron Resonance (ECR) ion source and 4-vane Radio Frequency Quadrupole (RFQ), as well as alternating- phase- focused (APF) Drift Tube Linac (DTL), which is a significant technological innovation. During last 5 years, we have finished a series of R&D stage including physical design, electromagnetic design, mechanical design, assemble and alignment, cavity cold test, RF conditioning and beam commissioning. Finally, we get 7 mA, 7 MeV proton beam from the down stream Faraday cup. According to our beam diagnostic and analysis system ,the center energy of the beam is 6.975 MeV, the beam intensity that within ±0.35% momentum spread is 6.07 mA.
Experimental study on spores treatment by array plasma jet
Chen Hongyu, Zhang Yong, Liu Zhen, Yan Keping
 doi: 10.11884/HPLPB202234.220003
[Abstract](20) [PDF 0KB](0)
In recent years, with the advancement of atmospheric pressure non-thermal plasma technology in the field of biomedical applications, it has shown many advantages in disinfection and sterilization. In terms of application, the key lies in how to easily generate a large-area, uniform and stable plasma. In this work, a set of unipolar microsecond pulse array plasma jet system is developed, which can be excited to generate plasma jet under atmospheric pressure and realize large-area sterilization treatment. The system generates high-voltage pulses with a peak voltage of 20 kV and a frequency of 15 kHz. The jet is uniform and stable, covering an area of 37.7 cm2, the jet length is stable at 6 cm and the jet power is 40.05 W. Treating for 5 min can basically all inactivate Bacillus subtilis spores in the area covered by the jet. The effects of different parameters on the sterilization efficiency were investigated, and the results showed that the sterilization rate was positively correlated with the working voltage, pulse frequency and treatment time. The sterilization effect was better under helium atmosphere. SEM showed that the plasma jet damaged the shell structure of Bacillus subtilis spores, causing the spores to fail to metabolize normally and eventually die.
Development of the MHz repetition bipolar pulse induction acceleration system
Huang Ziping, Long Jidong, Wang Wei, Chen Yi, Ding Mingjun
 doi: 10.11884/HPLPB202234.210513
[Abstract](22) [PDF 39987KB](7)
Based on the principle of Induction Synchrotron (IS), the high-repetition pulse induction acceleration module can replace the radio frequency acceleration cavity in circular accelerators, thereby obtaining more application prospects. In this paper, a set of MHz continuous repetition bipolar pulse induction acceleration module suitable for Induction Synchrotron is developed, and its circuit design and experimental results are introduced. Compared with the induction acceleration module of KEK, which is the only Induction Synchrotron acceleration module in use at present, this induction module adopts different circuit structures to make the longitudinal dimension of the induction cell be reduced by 5 times at the same pulse flat voltage drop, which can effectively improve the adjustment ability of accelerating voltage in a limited space, reduce the power consumption and cost of system cooling, and improve the reliability of continuous operation of the pulse power system.
LD triggered three electrode gas switch based on photoconductive semiconductor
Fu Jiabin, Wang Lingyun, He Yang, Feng Chuanjun, Xie Weiping
 doi: 10.11884/HPLPB202234.210536
[Abstract](24) [PDF 10006KB](11)
To trigger the gas switch with one fiber, a kind of LD (laser diode) triggered three electrode gas switch based on photoconductive semiconductor without trigger charger source is presented in this paper. The principle of this switch is that a GaAs PCSS, which is triggered by LD, is used to control the trigger pulse generation of the trigger capacitor discharge circuit (CDC). The capacitor in CDC is charged with the energy of the main circuit directly. As a result, this switch can work without trigger charge power source, which means this switch can be made more compact compared with traditional electrical trigger switch. A prototype designed for three electrode gas switch working under 40kV/8kA and PCSS triggered with 83 μJ laser energy is described in this paper in detail. The experimental result proves the feasibility. The experimental result also shows the longevity of photoconductive semiconductor is just several hundred shots. The longevity of photoconductive semiconductor will be improved in nest phase research.
Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Display Method:
A driver circuit to adjust the pulse edges of Marx generators
Zhang Rui, Rao Junfeng, Li Zi, Jiang Song, Wang Yonggang
 doi: 10.11884/HPLPB202234.220011
[Abstract](49) [PDF 4419KB](8)
A novel driving circuit for the adjustment of pulse edges in Marx generators is proposed. By adjusting the driving voltage amplitudes of the charge and discharge switches, the Miller plateau time is controlled in the driving circuit. Then the turn-on speed of the switches and the pulse edges of high-voltage pulses are adjusted. This drive circuit is simple in structure and does not require additional independent signals. A model is established to study the relationship between the driving voltage amplitudes and the turn-on speed of switches. Combined with the theoretical analysis results, the parameters of the driving circuit are designed, and the simulation results show that the driving circuit can adjust the pulse edge. A solid-state Marx generator with the proposed driving circuit was built to experiment under capacitive load and resistive load. Using this method, the edge adjustment of 3.6 kV output pulse from 55 ns to 7.7 μs for 6-stage Marx circuit was achieved, and the influence of different resistive loads on the pulse edge is compared and analyzed. The experiment results show that the driving circuit has unique advantages in improving the edge adjustment performance of pulsed generators.
Storage ring based coherent light sources
Jiang Bocheng, Tang Chuanxiang, Feng Chao, Deng Haixiao, Li Renkai
 doi: 10.11884/HPLPB202234.220047
[Abstract](17) [PDF 6933KB](6)
Synchrotron radiation from an electron storage ring holds many advantages such as stability, broad spectrum, multi-users supporting. However, it lacks coherence. When the coherent radiation is produced from a storage ring, not only the coherence of the light is enhanced, but also the flux, brightness and the energy resolution of the light can be remarkably improved. As the flux is further increased, the power of the radiation may reach the requirement of industry. This paper presents a review of various kinds of electron storage ring based coherent light sources and gives an outlook of its development.
Design and thermal analysis of front-end photon absorber at HALF
Ma Wenjing, Zhao Zhuang, Wang Sihui, Zhang Shancai, Fan Le, Hong Zhiyuan, Wei Wei
 doi: 10.11884/HPLPB202234.220057
[Abstract](28) [PDF 6018KB](7)
The Hefei Advanced Light Facility (HALF) is a diffraction limited storage ring (DLSR).The extracted light of HALF has higher brightness resulting in higher heat load to the storage ring. The redundant synchrotron radiation is absorbed by the photon absorber located in the front-end to protect the ultrahigh vacuum system of DLSR. A special design of the photon absorber is required due to the compact physical design. Considering the toothed surface profile, cooling channel, and installation, we propose a photon absorber made of CuCrZr without additional positioning on the basis of the two-piece vertical absorber. The spot size and power of the radiation from the bending magnet with a bending angle of 2.74° are calculated. The thermal-mechanical simulations based on the finite element analysis method show acceptable results. The maximum thermal deformation, temperature, and stress are 0.05 mm, 80 ℃, and 20.8 MPa, respectively, indicating that the new absorber works in a safe range. The present study provides a critical theoretical basis for the design of the photon absorber in the front-end of HALF.
Cover and Contents
Cover and Contents, High Power Laser and Particle Beams, No 5, Vol 34, 2022
Editorial Office
[PDF 3051KB](26)
Feature Issue on Application Technology of Research Reactor
Actinide nuclear targets preparation and applications
He Yao, Li Gang, Chen Qiping, Hu Rui, Deng Jian, Yang Yuchuan, Tu Jun, Peng Shuming
2022, 34: 056001.   doi: 10.11884/HPLPB202234.210507
[Abstract](87) [PDF 13449KB](35)

There is an increasing demand on precise, accurate and reliable experimental nuclear data in various scientific research fields like basic nuclear physics, nuclear energy, super-heavy element research and others. Actinide targets are composed of a thin-layer, pure actinide compound deposited on a certain metal foil. Acting as the stationary nuclei sources in nuclear reactions, high-quality actinide targets are essential for the uncertainty of the measured nuclear data and ensure the success of the relative experiments. In this review, the preparation methods of actinide nuclear targets, the development of organizations of nuclear targets, and the outlook are discussed.

Neutron irradiation effects of graphite serving in SPRR-300 reactor
Zheng Jian, Yan Zhanfeng, Wang Hao, Feng Qijie, Liu Xiankun, Liu Xiao, Wang Shuyu, Zhou Wei, Qian Dazhi
2022, 34: 056002.   doi: 10.11884/HPLPB202234.210511
[Abstract](57) [PDF 24171KB](8)
During the long period service in the SPRR-300 research reactor, the graphite box in the vicinity of the core has been irradiated for about 30 years. In this paper, we take samples from the graphite box and investigate the changes of the thermal, mechanical properties and microstructure, compare them with those of the commercial IG110 and NG-CT-10 graphite. We find that after the long-time service, the low fluence neutron irradiation has induced tremendous irradiation damage defects in the crystal structures of the SPRR-300 graphite. These defects are mainly dislocation loops, stacking faults, voids, microcracks, et al. A degree of amorphization has also been observed. Comparing with those of the IG110 and NG-CT-10 graphite, the coefficients of thermal expansion, thermal diffusivity, compression strength and the flexural strength of the SPRR-300 graphite decrease while the modulus of elasticity in flexure increase. The changes of the thermal and mechanical properties of the SPRR-300 graphite may due to the irradiation-induced defects.
Safety boundary of flow channel partial blockage in plate-type fuel assembly
Ding Wenjie, Wang Shaohua, Gao Jiao, Guo Haibing, Ma Jimin, Liu Zhiyong
2022, 34: 056003.   doi: 10.11884/HPLPB202234.210508
[Abstract](52) [PDF 854KB](8)
It is necessary to obtain the triggering boundaries of heat transfer deterioration by mastering the flow and heat transfer characteristics in plate-type fuel assembly with multiple channels blocked, to improve the operation safety of plate-type fuel reactors. Based on qualitative analysis, the flow channel partial blockage accidents can be divided into non-adjacent channel blockage accident and adjacent channel blockage accident for the standard fuel assembly of the typical plate-type fuel reactor JRR-3M. Furthermore, the simulations of the flow and heat transfer characteristics under the two types of accidents were carried out using the computational fluid dynamics software ANSYS Fluent. The simulation results show that local boiling will not occur in flow channels and the maximum fuel temperature will be lower than the allowable temperature when non-adjacent channels are completely blocked or the maximum blocking rate of adjacent channels is less than 35%. Therefore, the safety operation boundary of JRR-3M reactor under flow channel blockage accident can be determined.
Mathematical model establishment, simulation and reconstruction of PGAI
Ma Yuhua, Li Hang, Yang Xin, Li Rundong, Huang Hongwen
2022, 34: 056004.   doi: 10.11884/HPLPB202234.210551
[Abstract](152) [PDF 5433KB](30)
In the prompt gamma activation imaging, the neutron self-shielding and gamma self-absorption effect inside the sample will cause uneven distribution of the measurement results. To solve the problem of the biased distribution in the prompt gamma activation imaging, the influence of the neutron field inside the sample and the self-absorption effect of gamma were studied, and the transport process of neutrons and gamma rays was theoretically deduced. A mathematical model for correcting the biased distribution and image reconstruction was established. The Monte Carlo method was used to simulate the prompt gamma activation imaging of Fe and H elements, and the mathematical model was used to reconstruct the element images. The results show that the influence of neutron self-shielding and γ self-absorption effect in prompt gamma activation imaging has been significantly corrected, and the content distribution of Fe and H elements can be accurately reconstructed using this mathematical model, which verify the validity of the mathematical model.
Preliminary application of neutronics calculation in LFR reactor with metallic fuel using dragon code
Zhang Liang, Sun Sheng, Sun Shouhua, Yang Wenhua
2022, 34: 056005.   doi: 10.11884/HPLPB202234.220001
[Abstract](113) [PDF 4801KB](17)
Lead-bismuth/lead cooled fast reactor (LFR) is one of the fourth-generation advanced nuclear energy systems with good application prospects. Aiming at the application of two metallic fuels (UZr, UPuZr) with annular slug in an LFR fuel assembly and a typical LFR core, the Dragon/Donjon code was used to perform neutronics calculations. The results of 172-group and 295-group neutron databases based on the ENDF/B 8.0 library and the transport method (SP3) and the diffusion method (MCFD) were obtained and compared with the results using RMC code. The keff deviations using SP3 algorithm for UZr fuel are less than 550×10−5, and for UPuZr fuel, the keff deviations obtained by MCFD algorithm are less than −700×10−5. The maximum deviation of control rod worth is 7.6%, and the results using 172-grouplib and 295-grouplib are basically the same. By using the SP3 algorithm, the fuel assembly power deviations are less than ±6.0%, and the deviation with the SP3 algorithm is less than that with MCFD algorithm. The results preliminarily prove the feasibility of the Dragon/Donjon code for reactor physics analysis of LFR with metallic fuel.
Asymmetrical operation characteristics of natural circulation lead-bismuth reactor under ocean conditions
Wang Xu, Zhao Ya’nan, Zhao Pengcheng, Yu Tao
2022, 34: 056006.   doi: 10.11884/HPLPB202234.210474
[Abstract](192) [PDF 2803KB](17)
To ensure the vitality of naval nuclear power at all times, the natural cycle lead-bismuth reactor loop will take partial loop operation when it fails under marine conditions. However, there are few studies on the partial loop operation characteristics of lead-bismuth reactor under marine conditions. Based on the secondary development of RELAP5/MOD3.1 program, the off-loop operation characteristics of a 10 MW natural cycle lead-bismuth reactor under typical oceanic conditions are analyzed. The analysis results show that the system parameters of the reactor are less sensitive to the change of tilt angle when the reactor is operating under inclined conditions. Under undulating conditions, the fluctuation of flow rate is reduced by 9% and the outlet temperature is reduced by about 16 K. The larger the undulating amplitude, the more drastic the flow rate fluctuation; the larger the undulating period, the more obvious the flow rate oscillation, but the effect is also weakening. Under rocking conditions, the core flow and outlet temperature are reduced and the reactor introduces higher safety margins. The larger the swing amplitude and the smaller the swing period, the larger the flow fluctuation, and the core outlet temperature is significantly more sensitive to the cycle change than the swing amplitude change.
Intelligent optimization method for lead-bismuth reactor based on Kriging surrogate model
Li Qiong, Liu Zijing, Xiao Hao, XiaoYingjie, Zhao Pengcheng, Wang Chang, Yu Tao
2022, 34: 056007.   doi: 10.11884/HPLPB202234.210560
[Abstract](105) [PDF 1332KB](19)
The extensive application requirements of lead-bismuth reactors require researchers to carry out a lot of optimization design work on the basis of existing core schemes. Aiming at the multi-dimensional nonlinear constrained optimization design problem of lead-bismuth reactor with multi-physical, multi-variable and multi-constraint coupling effects, an intelligent optimization method for lead-bismuth reactor was constructed based on Kriging surrogate model, orthogonal Latin hypercube sampling and SEUMRE spatial search technology. Coupled with physical Monte Carlo calculation/thermal ranalysis code, an optimization platform including sampling, pre-and post-processing of coupling program and reactor optimization analysis function was developed. Taking SPALLER-4 and URANUS as prototypes, the scheme optimization and parameter optimization verification of minimum fuel load were carried out respectively. The verification results show that the core intelligent optimization method is feasible and effective for the optimization of lead-bismuth reactor design scheme and core parameters. Compared with the traditional Monte Carlo calculation optimization, the calculation cost is greatly reduced under the premise of ensuring the prediction accuracy. Compared with the URANUS initial model, the fuel loading, the total mass of the core, the volume of the active zone and the total volume of the core are optimized by 10.8%, 11.5%, 18.1% and 17.1% respectively, which provides a reference for the intelligent optimization method based on the surrogate model applied to the optimization design of lead-bismuth reactor.
The self-ion irradiation effects in 6061-Al alloy
Yan Zhanfeng, Zheng Jian, Zhou Wei, Wang Hao
2022, 34: 056008.   doi: 10.11884/HPLPB202234.210509
[Abstract](69) [PDF 6061KB](14)
Aluminum alloy is the main structural material of research reactors at home and abroad. In this paper, on the basis of the research on the irradiation damage of the structural material aluminum alloy in the 300# research reactor, the microstructural damage and hardness change caused by ion irradiation in 6061-Al alloy are studied to carry out the early exploration of the damage effect of 6061-Al alloy under higher neutron irradiation doses. The results show that 1/3<111> dislocation loops with angles of 72° are generated in 6061-Al alloy after self-ion irradiation. The defect density increases obviously with the increasing irradiation dose from 0.218×1016 cm−2 to 4.367×1016 cm−2. However, the selected area electron diffraction shows a good lattice structure and no amorphous transformation occurs. Nano-indentation test demonstrates obvious irradiation hardening after irradiation and the microhardness increases with the increasing doses. At the highest damage dose of 2.183×1016 cm−2 and 4.367×1016 cm−2, the hardening reaches saturation, approaching 11%. These results can provide data support for the preliminary prediction of the structure and property change in 6061-Al alloy under high neutron irradiation dose.
Size measurements of beryllium assemblies after long term service
Liu Xiao, Yang Wankui, Wang Hao, Wang Jian, Zhang Songbao, Zhang Xinrong, Li Wenhua
2022, 34: 056009.   doi: 10.11884/HPLPB202234.210516
[Abstract](47) [PDF 19694KB](5)
Beryllium is an important material as neutron reflection layers in nuclear reactors. The size change of beryllium after long term neutron irradiation has a great influence on the reactor safety. To obtain the size change of beryllium assemblies after long-time irradiation for the assessment of service performance, a set of special tools were designed and manufactured. The size change of post-irradiation beryllium assemblies was examined on a three coordinate measuring machine. The measurement results indicate that beryllium assemblies of the SPRR-300 reactor have excellent stability after 29 a irradiation, even under the maximum neutron fluence of 6.78×1021 cm−2. The section dimension has little change in local part of beryllium assemblies and the largest change is about 0.13 mm, which indicates that irradiation creep is the main reason for the dimension change of beryllium assemblies during the long-time service.
Investigation into optimum design of recuperator at a confirmed heat transfer area
Gao Jiao, Wang Shaohua, Huang Hongwen
2022, 34: 056010.   doi: 10.11884/HPLPB202234.210521
[Abstract](32) [PDF 4768KB](3)
This study aims to investigate the heat transfer characteristics of supercritical CO2 when flowing through the printed circuit heat exchanger with Z type channel, and further guide the optimum design of recuperator at confirmed heat transfer area. Numerical simulation is used to analyze the local and overall heat transfer characteristics between CO2 at two pressures. The heat transfer characteristics of a recuperator with typical structure are calculated at a typical working condition, and compared to the experimental results to check the computation model. Then, the heat transfer characteristics of the recuperator with the same heat transfer area but different channel structure are calculated. The effect law of the structure on heat transfer is explored. The study shows that the calculation results have good agreement with the experimental results. The heat transfer coefficient decreases the most when the channel included angle increases from 110° to 115°and the advised range is 110°−120° for different design requirements.
A supercritical carbon dioxide cycle efficiency analysis
Wang Shaohua, Gao Jiao, Ding Wenjie, Huang Hongwen, Guo Haibing, Ma Jimin, Liu Zhiyong
2022, 34: 056011.   doi: 10.11884/HPLPB202234.210528
[Abstract](57) [PDF 1924KB](6)
The supercritical carbon dioxide (S-CO2) Brayton cycle is a new type of power generation technology with broad application prospects. This paper takes the supercritical carbon dioxide simple Brayton cycle with recuperation as the research object, and takes the nuclear power plant as the application background. The system cycle model and the efficiency model of the key components is discussed in detail. Based on this model, the influence of various engineering factors on the efficiency of the Brayton cycle and the volume of the system has been discussed. The analysis results show that the sensitivity of cycle efficiency and system volume to parameters such as temperature, pressure, turbomachinery efficiency and regenerator design differs obviously, and the most effective method to reduce the system volume is increasing the turbine inlet temperature. It is necessary to establish a complete system analysis model to optimize the design of the S-CO2 system.
High Power Laser Physics and Technology
Large core air cladding micro structured optical fiber for kW laser transmission
Xia Changming, Huang Zhuoyuan, Liu Jiantao, Yang Jiahao, Mo Zhifeng, Hou Zhiyun, Zhou Guiyao
2022, 34: 051001.   doi: 10.11884/HPLPB202234.210452
[Abstract](86) [PDF 1579KB](24)

Kilowatt high power laser flexible transmission is a necessary link in the field of high power laser processing such as laser cleaning, laser welding, laser etching, and the low loss optical fiber with bend loss is the key device to realize high power laser transmission. At present, high power laser transmission fiber adopts large core diameter fiber, but there are some problems, such as large bending loss, poor flexibility and so on. Therefore, a large core diameter air clad micro structure optical fiber is proposed. The air holes in the fiber cladding can greatly reduce the risk of laser leakage, reduce the strict requirements of high temperature coating in the process of fiber preparation, and achieve kW laser output, thus offer the foundation for the flexible transmission of 10 kW high-power laser.

17.4 kW (1+1) long distance side-pumped laser fiber
Gao Cong, Liu Nian, Li Fengyun, Liu Yu, Dai Jiangyun, Shen Changle, He Hongle, Lü Jiakun, Li Fang, Zhang Lihua, Li Yuwei, Jiang Lei, Guo Chao, Tao Rumao, Ke Weiwei, Zhang Haoyu, Wang Jianjun, Lin Honghuan, Jing Feng
2022, 34: 051002.   doi: 10.11884/HPLPB202234.220070
[Abstract](114) [PDF 1332KB](43)

The long distance side-pumped laser fiber (LDSPF) is characterized by its ability for high power pump power coupling, heat management and nonlinear effect suppressing, which is quite potential for high power fiber laser application.A (1+1) LDSPF for tandem pumping was fabricated and tested. Pumped by 1018 nm fiber lasers, 17.4 kW laser output at 1080 nm with a slope efficiency of 82.1% was achieved with this fiber amplifier with backward pumping technique. Linewidth at 3 dB of the laser is 1.3 nm and the ratio of signal light to SRS is around 37.8 dB at the maximum power. The results demonstrate great potential of LDSPF as power amplifier for tens of kilowatts fiber laser.

Focusing characteristics of Riemann-Silberstein vortices of edge-dislocation Gaussian beam passing through a bifocal lens
Yan Hongwei
2022, 34: 051003.   doi: 10.11884/HPLPB202234.210317
[Abstract](71) [PDF 1132KB](8)
Based on the zeros of the time-averaged complex scalar field, the complex scalar field of Riemann-Silberstein (RS) vortices generated by the edge dislocation line embedded in the Gaussian beam propagating through the bifocal lens is derived. The focal characteristics of the RS vortices are studied in detail, and the influence of the propagation distance and the focal length of the bifocal lens on the RS vortices is nalyzed. It is found that the RS vortices will move after passing through the bifocal lens, a new pair of RS vortices with opposite topological charge will be generated, and two RS vortices with opposite topological charge will gradually approach each other to annihilation. However, during the entire focusing process, the total topological charge of the RS vortices is conserved. In particular, when the RS vortices pass through an ideal lens, there are always only four RS vortices on the x-axis in the complex scalar field. As the propagation distance increases, these four RS vortices gradually approach the origin (0, 0), and then gradually move away from the origin (0,0), but the topological charge of each RS vortex has remained unchanged, thus the total topological charge is conserved.
Inertial Confinement Fusion Physics and Technology
Online diagnosis system for D3He proton in laser fusion implosion experiments
Teng Jian, Deng Zhigang, Shan Lianqiang, Wen Jiaxing, Yuan Zongqiang, Wang Weiwu, Zhang Tiankui, Tian Chao, Zhang Feng, Yu Minghai, Lu Feng, Hong Wei, He Shukai, Zhang Zhimeng, Qi Wei, Cui Bo, Xu Qiuyue, Wei Lai, Li Yingjie, Xia Liqiong, Zhang Xing, Wu Yuchi, Su Jingqin, Zhou Weimin, Gu Yuqiu
2022, 34: 052001.   doi: 10.11884/HPLPB202234.210497
[Abstract](68) [PDF 2333KB](8)
An online magnetic spectrometer system based on a hybrid pixel detector is proposed for the diagnosis of the D3He proton spectrum and yield in laser fusion implosion experiments. By identifying the number and energy of the track clusters and considering the experiment setup, the proton spectrum and yield could be deduced in time. The online diagnosis system is tested on the SG laser facility, in which 31 laser beams are focused on the capsule to drive the fusion reaction. With D2 and 3He gas mixed 1∶1 by atomic ratio, the primary D3He proton energy spectrum with center energy of 14.6 MeV, FWHM of 2.1 MeV, and yield of 2.3×109 is obtained. This system could provide the D3He proton spectrum and yield online, which would be helpful to improve the experiment in time.
Investigation into preparation of thin-walled polystyrene hollow microspheres for ICF
Xu Wenting, Li Jie, Liu Yiyang, Chen Qiang, Yi Yong, Liu Meifang
2022, 34: 052002.   doi: 10.11884/HPLPB202234.210557
[Abstract](60) [PDF 21948KB](5)
As an effective way to explore controlled nuclear fusion, laser inertial confinement fusion (ICF) is expected to obtain clean and pollution-free energy. Thin-walled polystyrene (PS) hollow microspheres are a type of microspheres urgently needed in ICF physics experiments. Thin-walled hollow microspheres are easy to crack while drying and being used due to the increase in diameter-to-thickness ratio (diameter/wall thickness). In this work, the influence of the PS materials on the quality of thin-walled microspheres was studied, and the mechanism was discussed. The results show that when the oil phase (PS) mass fraction was 4%, the stability of W1/O/W2 composite emulsion particles gradually increased with the increase of oil phase viscosity; when the oil phase mass fraction was not less than 8%, the stability of compound droplets was fine. There is no significant difference in the surface roughness of the corresponding microspheres. The sphericity and wall thickness uniformity of microspheres decreased with the increase of initial oil phase viscosity. In the drying process, the cracking rate of microspheres decreased with the increase of oil phase viscosity. The rate of microsphere cracking decreases as the mechanical properties of the raw material improves. To compensate for the adverse effect of the increase in oil phase viscosity on the sphericity and uniformity of the wall thickness of the microspheres, fluorobenzene (FB) droplets were introduced into the external water phase to reduce the solidification rate.
High Power Microwave Technology
Prediction of coupling cross section of hexagonal aperture array based on BP neural network
He Zhibin, Yan Liping, Zhao Xiang
2022, 34: 053001.   doi: 10.11884/HPLPB202234.210566
[Abstract](51) [PDF 2539KB](7)
As an important parameter to measure the leakage of electromagnetic energy through apertures, there has not been a universal, fast and high precision method to obtain the coupling cross section (CCS). For obtaining the hexagonal aperture array normalized CCS, we analyze the influence of various factors on it under the condition of vertical incidence. A total of 13820 sets of CCS data are obtained by selecting appropriate parameters and using full-wave analysis method. After some input parameters are preprocessed and the neural network is trained, a BP neural network model has been constructed with seven parameters including the electrical dimension of the aperture unit, row/column number, the electrical dimension of the row/column distance, the electrical dimension of the aperture wall thickness and polarization angle of incident wave as the input and the normalized CCS as the output. The model has an average relative error of 3.8% when the predicted normalized CCS of the hexagonal aperture array has the electrical dimensions [0.1, 1.2]. A total of 480 CCSs with input parameters not appearing in both the training set and the test set are predicted by the neural network and compared with the full-wave analysis results, and the average relative error is 7.27%. Finally, the universality and effectiveness of the model are validated further by experimental measurement.
Development and validation of electromagnetic coupling solver for electrically large-sized cavity structure based on power balance method
Hu Minglang, Zhou Shihua, Yan Liping, Zhao Xiang
2022, 34: 053002.   doi: 10.11884/HPLPB202234.220026
[Abstract](48) [PDF 1549KB](6)
The power balance (PWB) method is a fast method based on statistical electromagnetics for solving electromagnetic coupling problems in electrically large-sized cavity structures. Based on the PWB method, an electromagnetic coupling solver is developed to solve the electromagnetic coupling level of electrically large-sized cavity structure with different cavity shapes, different aperture shapes and different source types, etc. The validity and efficiency of the solver is validated by comparing its output with the results in the published literature and those of experiments.
Particle Beams and Accelerator Technology
Research advances in ultrafast X-ray free-electron lasers
Jia Haoyan, Huang Senlin, Jiao Yi, Li Jingyi, Liu Kexin, Liu Shuai, Liu Weihang, Liu Zhongqi, Long Tianyun, Qin Weilun, Zhao Sheng
2022, 34: 054001.   doi: 10.11884/HPLPB202234.220056
[Abstract](204) [PDF 14246KB](62)

Advances in modern light sources continue to improve our understanding of the fundamental structure and microscopic dynamics of matter. As the most advanced light source, X-ray free-electron lasers provide the brightest X-rays with ultrahigh peak power, ultrashort pulse length, and excellent coherence, making it possible to detect and manipulate ultrafast processes in atomic and molecular systems. X-ray free-electron laser facilities in operation worldwide have shown great value in the application fields of physics, chemistry, biology, material science, etc. Furthermore, many efforts have focused on improving the performance of X-ray free-electron lasers, including reducing the pulse duration from femtosecond to attosecond for opening new frontiers in ultrafast science. This paper mainly reviews the recent progress of ultrafast X-ray free-electron lasers and summarizes various schemes in terms of their generation mechanisms, unique properties and latest results. Finally, it predicts the future development of ultrafast X-ray free-electron lasers.

Simulation for measurement technique of electron beam divergence basing on Cherenkov radiation
Jiang Xiaoguo, Chi Zhijun, Liao Shuqing, Du Yingchao, Yang Guojun, Zhang Xiaoding, Li Hong, Yang Xinglin, Jiang Wei, Wei Tao, Wang Yuan
2022, 34: 054002.   doi: 10.11884/HPLPB202234.210426
[Abstract](119) [PDF 3629KB](13)
The direction of Cherenkov Radiation (CR) light is strictly defined by the direction along which the charged particle moves. This characteristic can be adopted to measure the electron beam divergence and it is a hopeful method. The Coulomb force on electron in the convertor expand the beam divergence and obviously reduce the measurement precision. A model of multi-slice in cascade connection is adopted to constitute convertor configuration. Taking into account the combined effect of Coulomb force, multiple scattering, bremsstrahlung and ionization, the deviation process of electron in the convertor material is then simulated by Monte-Carlo simulation. Measurement technique of electron beam divergence is further simulated basing on the principle of exact corresponding relationship between electron beam divergence distribution and CR photon distibution. Some effect on measurement are obtained for factors including convertor material, thickness, beam energy divergence and optical bandwidth of measurement system. The simulated results give many useful suggestions for the design of the measurement system and the image data processing. The simulation results obviously show the feasibility of electron beam divergence measurement basing on Cherenkov radiation and that its distribution can also be measured in a certain extent.
Pulsed Power Technology
Design of arbitrary polarity rectangular pulse power supply based on Marx
Jiang Song, Huang Lifei, Rao Junfeng, Wang Yonggang, Li Zi
2022, 34: 055001.   doi: 10.11884/HPLPB202234.210405
[Abstract](113) [PDF 2186KB](25)
Low temperature plasma produced by dielectric barrier discharge (DBD) is widely used in plasma medicine, environmental governance and other fields. The common driving source is high voltage pulse power supply. A rectangular pulse power supply based on Marx circuit is designed. The power supply combines the magnetic ring isolation drive scheme with the full-bridge Marx circuit to realize the output of positive, negative and bipolar high voltage rectangular pulses, which solves the limitation that the conventional pulse power supply can only output specific polarity pulses. The operation mode of the circuit is analyzed theoretically and the experimental prototype is built. Under no-load conditions, the pulse polarity can be adjusted and the amplitude of 10 kV high voltage pulse output is realized. The parallel plate dielectric barrier discharge reactor was successfully driven by the pulse power supply, which further verified the feasibility of the scheme.
Design and analysis of repetitive frequency inductor in high power and high energy storage pulse power supply
Wang Yan, Zhang Qin, Lin Fuchang, Li Hua
2022, 34: 055002.   doi: 10.11884/HPLPB202234.210417
[Abstract](138) [PDF 15704KB](33)
To meet the requirement of continuous discharge in the integrated system of high power pulse power supply a repeatitive frequency water-cooled inductor for the system was developed. In the system, the water-cooled inductor can not only adjust the current waveform of the power supply, but also play an isolation role. The repeatitive frequency water-cooled inductor can withstand high voltage, large current, charge interval period of 6 seconds, and can work continuously for 10 times of discharge capacity. To meet the requirement of continuous discharge, deionized circulating water is used to cool the inductor. Taking the single module energy of 334 kJ, inductance of 30 μH, and current of 100 kA as an example, the design and analysis are carried out to establish the temperature field simulation model of the inductor, and analysis is made on the transient characteristics of the internal temperature of the inductor through ANSYS simulation software. The results show that the inductor is well cooled by deionized water, and the maximum temperature of the inductor reaches 47 ℃ after each operation, and the temperature of the inductor recovers to 41 ℃ before the next operation point. At the same time, the inductor passes the 112 kA electrodynamic test without circulating water. The experimental results agree well with the theoretical analysis, and the inductor runs stably, which verifies the correctness of theoretical analysis and design.
Advanced Interdisciplinary Science
Surface plasmon resonance refractive index sensor based on microstructured fiber with air-hole
Tan Qilong, Zhang Xia, Kang Hu, Peng Zhiqing, Li Xiaowei, Yang Mochou, Feng Guoying
2022, 34: 059001.   doi: 10.11884/HPLPB202234.220062
[Abstract](48) [PDF 3314KB](8)
A photonic crystal fiber refractive index (RI) sensor based on enhanced surface plasmon resonance (SPR) effect is proposed. The sensor structure is spliced with a photonic crystal fiber (PCF) by a fiber fusion splicer, so that an air hole is introduced in the middle of the photonic crystal fiber to form a PCF-air hole-PCF optical fiber sensing structure. Then, a thin gold film is deposited on its surface by using magnetron sputtering coating process. Experiments are carried out to investigate the response of the refractive index and temperature of the sensor. The results show that in the refractive index (RI) range of 1.333−1.389, the sensor has an average RI sensitivity of 2 142.52 nm, with a linearity of 0.981 and a quality factor about 13.10. Experimental results show that the sensor is not sensitive to temperature. Compared with the PCF sensing structure without air hole, the air hole introduced enhances the SPR effect, so that the sensor has a good resonance peak depth. Benefiting from the above advantages, this type of sensor is expected to be applied in fields such as biomedicine and environmental monitoring.