Just Accepted manuscripts are peer-reviewed and accepted for publication. They are posted online prior to technical editing formatting for publication and author proofing.
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Investigationon wide-angle scanning technology for high power resonant waveguide slot array antenna
Ma Jiawen, Sun Yunfei, Wan Jianfeng, Zhang Qiang, Yuan Chengwei
 doi: 10.11884/HPLPB202133.210307
[Abstract](32) [PDF 1483KB](3)
In traditional high-power slotted waveguide arrays, the mutual coupling between the adjacent slots seriously affects the wide-angle scanning ability of the array. To improve beam scanning ability, the scanning characteristics of the array has been analyzed. An isolation barrier has been introduced into the traditional slotted waveguide array to suppress the cross polarization caused by the inclined slots and improve the isolation of the elements. In this paper, an antenna array based on the rectangular waveguide with resonant slot in the narrow-wall has been proposed and designed, the simulation results show that the traditional structure can only scan to ±34° when S11≤−10 dB. But after loading the isolation barrier, the scanning range is expanded to ±45° with 2.3 dB gain variation. Moreover, the power handling capacity of a single slotted waveguide is more than330 MW, which indicates application potentials of this antenna in high power microwave (HPM) field.
Application of random media program based on SuperMC in solving double-heterogeneity
Zhu Tong, Chen Yuqing, Xie Mingliang, Li Ang, Ye Lei
 doi: 10.11884/HPLPB202133.210301
[Abstract](16) [PDF 878KB](0)
The dispersed fuel element is often used in small integrated PWR. The fuel core is composed of a large number of small fuel microspheres mixed in the metal matrix, and the volume heterogeneity exists between the fuel particles and the matrix. If the local space self-screen effect of the dispersion fuel can not be effectively treated, it will bring some deviation to the calculation of physical property parameters. The traditional deterministic method neglects the double-heterogeneity of dispersive fuel. In this paper, the explicit modelling and the random medium program based on SuperMC are used to establish the volumetric homogenization model and grain model to verify double-heterogeneity. Finally, the traditional RPT model of the dispersive plate-fuel was established to correct the calculation deviation. The results show that the random media program combined with SuperMC can simulate the calculation of transport and burn up of various types of particles, and can well analyze and solve the double-heterogeneity.
Study on the measurement of environmental level x, γ dose value with conversion of complete spectra without deconvolution method of MC simulation
Cao Lei, Zhang Yaofeng, Yang Yang, Huang Jianwei, Zhang Xiaole
 doi: 10.11884/HPLPB202133.210300
[Abstract](19) [PDF 2610KB](0)
For the accurate measurement of environmental X/γ radiation dose rate, the conversion from energy spectrum to dose rate is used. In this paper, the energy spectrum and dose value of the electrically cooled high-purity germanium detector (HPGe detector) in the energy range of 0.01−1.5 MeV are obtained by Monte Carlo simulation. And the method “Conversion of complete spectra without deconvolution” is used for energy spectrum-dose conversion study. It is found that the dose rate calculated by Conversion of complete spectra without deconvolution method is in good agreement with the simulated dose rate. Through the experimental verification in the standard radiation field (Co-60, Cs-137) of the environmental γ radiation air absorbed dose of the China Institute of Metrology, the result shows that in the energy range of 0.01−1.5 MeV, the error between the dose rate value obtained by energy spectrum-dose conversion and the standard dose rate value is less than ±10%. The study shows that it is feasible to solve the energy spectrum-dose (rate) conversion coefficient by the method “Conversion of complete spectra without deconvolution”.
Bunch-by-bunch phase measurement and longitudinal instabilities diagnostics at Hefei Light Source
Tang Leilei, Lu Ping, Sun Baogen, Zhou Zeran, Wu Ruizhe
 doi: 10.11884/HPLPB202133.210164
[Abstract](30) [PDF 1686KB](1)
In order to study the longitudinal motion characteristics of multi bunches in a storage ring, a bunch-by-bunch phase measurement system is developed at HLS-II. The system uses oscilloscope to collect BPM sum-signal directly, and take zero-crossing detection method combined with temporal difference (TD) method to extract the phase of bunch-by-bunch from BPM sum-signal. The system architecture, phase extraction method and some experimental results at HLS-II are introduced here. In the experiment, through off-line analysis of the phase data of 5ms bunch-by-bunch multi turns recorded by the system, the characteristic information of the synchrotron oscillation frequency, the longitudinal tune value, the modes information of bunches oscillation and the growth rate of the oscillation mode are obtained. It is diagnosed that there are two strong longitudinal coupled-bunch unstable modes at HLS-II during the top-off constant-current operation, and the growth rates of the two oscillation modes are extracted. The results of bunch-by-bunch phase measurement and the analysis of longitudinal instability can provide the references for machine study, longitudinal feedback system tuning and performance evaluation of high frequency RF system.
The research status and progress of pulsed laser ablation propulsion technology in the field of aerospace
Hong Yanji, Mao CengTao, Feng XiaoHui
 doi: 10.11884/HPLPB202133.210275
[Abstract](27) [PDF 2254KB](3)
Pulsed laser ablation propulsion has the characteristics of high specific impulse and precise and controllable thrust. It can be used not only for launching payload, but also for satellite drive, even for deflecting the orbit of asteroid, whose surface material would be ablated as propellant. Therefore, pulsed laser ablation propulsion has attracted more and more attention in the aerospace field. Focusing on laser launch vehicle of single stage to orbit, transmission to geosynchronous orbit and Mars orbit; laser plasma thrusters for the attitude and orbit control of spacecraft, laser-electric hybrid acceleration systems; laser ablation for orbit manipulation of centimeter scale space debris and attitude manipulation of larger space debris; laser ablation for deflecting the orbit of asteroid, this paper systematically and comprehensively summarizes the research status and progress of pulsed laser ablation propulsion technology in the field of aerospace, and analyzes in detail the key problems such as the average power, wavelength, pulse width of laser and the selection of propellant.
Fiber-laser-pumped high-power mid-infrared optical parametric oscillator based on MgO:PPLN
He Yang, Chen Fei, Wan Haohua, Ji Yanhui
 doi: 10.11884/HPLPB202133.210308
[Abstract](31) [PDF 797KB](3)
In order to achieve high-power mid-infrared laser output with high efficiency, the optical parametric oscillator (OPO) based on MgO:PPLN crystal is researched. The pump source is linearly polarized Yb-doped fiber laser (YDFL) with master oscillator power amplifier (MOPA) structure. Experimental results indicate that the YDFL can realize the pulse linearly polarized laser with the highest power of 79.1 W at 1064.1 nm. With the pump laser, the OPO obtains the maximum MIR power of 9.15 W at 3.754 µm by optimizing the curvature radius of output coupler and the pump waist diameter. The corresponding optical-to-optical conversion efficiency is 11.57%. The repetition rate and the pulse width of mid-infrared laser are 300 kHz and ~110 ns, respectively.
Progress on intra-pulse difference frequency generation in femtosecond laser
Yang Xuemei, Tian Kan, He Linzhen, Wang Weizhe, Houkun Liang
 doi: 10.11884/HPLPB202133.210246
[Abstract](30) [PDF 1500KB](2)
Mid-infrared (MIR) lasers have various advantages and can be widely used in either fundamental research fields or practical applications such as strong-field physics, molecular sensing and minimally-invasive tissue ablation. Generally, there are two categories of methods to generate MIR laser emission: one is direct lasing and the other is nonlinear frequency down-conversion. However, for the ultra-broadband few-cycle MIR generation, nonlinear down-conversion is the only available method. Intra-pulse Difference Frequency Generation (IP-DFG) is a simple method of nonlinear frequency conversion. In this article, the IP-DFG technology for the ultra-broadband MIR few-cycle pulses generation is reviewed. Different MIR nonlinear crystals, various driving laser sources, the spectral coverage of the MIR-IPDF output, and the conversion efficiency are compared and discussed. Last but not least, the prospects and challenges of MIR IP-DFG are presented.
Relationship between the geometric characteristics of the polishing area and the key parameters of the flow field creation
Yang Hang, Yu Yumin, Zhang Yunfei, Huang Wen, He Jianguo
 doi: 10.11884/HPLPB202133.210151
[Abstract](27) [PDF 1418KB](0)
In the actual working process of magnetorheological polishing, the difference of the geometric characteristics of the polishing area will have a great influence on the key parameters of the flow field creation. However, there is still a lack of research in this area, so this article establishes a three-dimensional model and experimental simulation for this problem. When studying the relationship between the geometric characteristics of the polishing area and the key parameters of the flow field creation, first change the shape of the polishing area to observe its influence on the shear stress and pressure in the flow field creation; when the shape of the polishing area is the same, pass Change the size of the polishing area and observe the effect on the shear stress and pressure in the creation of the flow field. It is found that when the shape of the polishing area is different, the shear stress is the largest when the polishing area is concave, and the shear stress is the smallest when the polishing area is convex. When the shape of the polishing area is convex, the shear stress on both sides of the polishing area increases as the curvature of the polishing area increases; when the shape of the polishing area is concave, the shear stress on both sides of the polishing area increases as the curvature of the polishing area increases. Decrease. When the shape of the polishing area is different, the pressure is maximum when the polishing area is concave, and the pressure is minimum when the polishing area is convex. When the shape of the polishing area is convex, the pressure at the polishing area increases as the curvature of the polishing area increases; when the shape of the polishing area is concave, the pressure at the polishing area decreases as the curvature of the polishing area increases.
Design and test of transition device from ridge waveguide to coaxial line
Zhang Hui, Mu Zhencheng, Rong Linyan, Wang Bo, Wan Maliang, Xie Zhexin, Zhou Wenzhong, Li Song, Liu Meifei
 doi: 10.11884/HPLPB202133.210105
[Abstract](24) [PDF 1529KB](0)
Waveguide to coaxial line transformer is often used in RF measurement systems. In order to measure the network parameters of these RF devices with a vector network analyzer and other instruments, the transformer from waveguide to coaxial line is indispensable to convert the waveguide ports of the RF devices to 50 Ω coaxial line which can directly access the network analyzer. The 648 MHz/WR1500 transformer designed in this paper is mainly used for the measurement of the superconducting Linac RF devices at the CSNS upgrading phase (CSNS-II). In this paper used Chebyshev ridge ladder impedance transformation and probe coupling completed waveguide to coaxial line transition. The ridge loaded waveguide and discontinuous coaxial line are analyzed respectively, and the optimal size is obtained.The designed transformer has the characteristics of low insertion loss, low VSWR and wide bandwidth to achieve high measurement accuracy. At last, the transition device is tested, and the test results are close to the simulation results, which can meet the requirements of being a measuring device.
Adjustment method of control network for alignment in CSNS
Wang Tong, Dong Lan, Liang Jing, Ma Na, Ke Zhiyong, He Zhenqiang, Luo Tao, Men Lingling, Yan Luping, Han Yuanying, Lu Shang, Zhang Luyan, Yan Haoyue, Liu Xiaoyang
 doi: 10.11884/HPLPB202133.210096
[Abstract](25) [PDF 1022KB](0)
Control network is the reference of equipment installation and alignment, so the adjustment processing of control network is very important. In this paper, the data processing methods of plane and elevation adjustment separately and three-dimensional adjustment were studied in LINAC of China Spallation Neutron Source. Meanwhile, in order to make the data processing more simple and convenient, SA software was introduced to realize the three-dimensional with the gravity orientation constrained. Through the comparison of different software and different data processing methods, the correctness of data processing of control network is verified. Finally, the accuracy of 200 m linear control network was better than 0.2 mm, which provides guidance for data processing of control network for alignment.
Investigation on the storing and dumping processes of energy in high quality factor resonant cavity
Wang Zicheng, Zhang Zhiqiang, Gao Dongping, Ding Yaogen, Gao Huailin
 doi: 10.11884/HPLPB202133.210132
[Abstract](33) [PDF 1251KB](0)
In order to calculate the storing process and dumping process of energy in high quality factor resonant cavity, the input iris and the output coupling structure are modeled as a 2-port net and a 3-port net respectively, and an algorithm based on iteration is proposed according to the signal flow graph of the high quality factor resonant cavity. The algorithm is then used to design a high quality factor resonant cavity working at near to 2.92 GHz and based on rectangular waveguide of type BJ32, when the width of the input iris takes 20 mm and the width of the output iris takes 60 mm, the resonant frequency, the storing time, the pulse width of the output pulse, the peak output power gain and the energy efficiency are calculated to be 2.9198 GHz, 2.6 μs, 6.82 ns, 129.6 and 0.169, respectively.
Vehicle cable electromagnetic pulse coupling simulation and suppression
Wang Zhen, Cai Jinliang, Qin Feng, Hu Zezheng
 doi: 10.11884/HPLPB202133.210227
[Abstract](29) [PDF 2637KB](1)
Transient electromagnetic pulses can be coupled to vehicle electronic system through cables, causing electronic equipment disturbed, even damaged. Research on the suppression characteristics of transient protection devices on electromagnetic pulse can provide strong support for vehicle electromagnetic harden. In this paper, we build the electromagnetic simulation model of vehicle engine by considering the key metal structure, cables and electronic equipment. Cables coupling characteristics were calculated under transient electromagnetic pulse; A test platform for transient protection devices was built, and the response characteristics of transient voltage suppress (TVS) and metal oxide varistor (MOV) were obtained, such as response time, clamping voltage, and peak voltage leakage. Based on the simulation and test results, a type of TVS was selected. This TVS is used to the signal line electromagnetic protection of camshaft position sensor. The result shows that this type TVS has an ability of cable interference suppression close to 20 dB, and placing it in the front of filter can effectively suppress cable coupling interference and protect terminal equipment.
Wideband radar cross section reduction of a slot array antenna using
Pan Chenqing, Zhou Dongfang, Liu Qikun, Zhang Yi, Lü Dalong, Zhang Dewei
 doi: 10.11884/HPLPB202133.210197
[Abstract](38) [PDF 1527KB](6)
A new type of unit that uses polarization conversion metasurfaces (PCM) to reduce the radar cross section (RCS) and maintain the radiation characteristics of slot antenna arrays is proposed. The PCM is composed of slotted rectangular patches arranged obliquely at 45°, which are placed on the upper surface of the slot array antenna. This paper analyzes the characteristics and principles of RCS reduction. Simulation and experimental results show that the single-site RCS reduction bandwidth of the slot antenna array with PCM is 8.0~21.8 GHz under the impact of x-polarized and y-polarized waves. At the same time, the antenna's radiation characteristics are well maintained in terms of impedance bandwidth, gain, and radiation pattern.
Design of a low-scattering transmissive lens based on integrationof absorption with focusing
Hu Jiaqi, Li Zhenyu, Wang Zuxin, Shang Yuping, Wang Sihao, Liao Cheng
 doi: 10.11884/HPLPB202133.210169
[Abstract](58) [PDF 2883KB](8)
Based on integration of a transmissive metasurface lens with the circuit analog absorber, the design of a microwave composite material with characteristics of both transmissive wavefront conversion and out-of-band radar cross-section reduction is proposed and examined. With refraction tuned by gradient phase compensation, the lens consisting of sub-wavelength spaced layers of periodic inclusions exhibits a reciprocal conversion between planar and spherical wavefronts. Moreover, responses of the lens at lower side of the wavefront conversion band are used to construct a circuit analog absorption profile containing one lossy layer. By using an aperture-coupled microstrip patch antenna element as the primary feeding antenna, main lobe gain enhancement over a wide band is observed as a result of the wavefront conversion of the composite material. In comparison with the lens, the introduction of the circuit analog absorption profile produces radar cross-section reduction over the bandwidths of 130.68% and 155.11% for TE and TM polarizations, respectively. The full-wave simulation and experimental measurement demonstrate the enhanced radiation gain and reduced radar cross-section and illustrate the validity of the composite material design with integrated absorption and focusing.
Quantification characterization technology of electromagnetic compatibility based on test results
Chen Xin, Qiu Yang, Tian Jin, Zuo Jiang jiang, Lu Xichen, Yang Chun, Xu Liang, Zhao Renzhong
 doi: 10.11884/HPLPB202133.210138
[Abstract](35) [PDF 1243KB](1)
Based on the quantitative requirements of equipment electromagnetic compatibility (EMC), the test results can be divided into EMI type and EMS type according to the characteristics of EMC test data. Thus the quantitative representation methods of EMI and EMS test results are put forward and the mathematical model is established in this paper. By analyzing the characteristics of EMI test data, the corresponding quantization representation model is constructed through the two dimensions of standard data share and excessive features. According to the characteristics that EMS test results are only qualitative description and combined with the sensitive phenomena in the measurement process, a quantitative characterization model is constructed from two dimensions of interference source and sensitive frequency band. Besides, the relevant quantitative model is realized by software and verified by experimental measurement. In this paper, the quantitative research of the test results is carried out and the mathematical quantification model of the corresponding test items is obtained, and the quantitative characterization of the EMC qualitative test results based on the national military standard is achieved. The relevant research results of this paper have certain reference significance in the direction of system-level EMC performance quantitative evaluation, big data analysis of test results and optimization design of equipment EMC.
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).
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Cover and Contents
Cover and Contents, High Power Laser and Particle Beams, No 9, Vol 33, 2021
[PDF 2570KB](1)
High Power Laser Physics and Technology
Fabrication of high-power semiconductor laser with wavelength-locked at 780 nm
He Lin’an, Zhou Kun, Zhang Liang, Li Yi, Du Weichuan, Hu Yao, Gao Songxin, Tang Chun
2021, 33: 091001.   doi: 10.11884/HPLPB202133.210099
[Abstract](41) [PDF 955KB](6)
A short wavelength of 780 nm semiconductor laser has been designed and fabricated, and the mode locking by external cavity feedback has been studied. The epitaxial layers were prepared by the metal organic chemical vapor deposition technology. GaAsP and GaInP were used as the quantum well and waveguide layer, respectively. The confinement layers were AlGaInP material with low refractive index. Using the ultra-high vacuum cleavage and passivation technology, an amorphous ZnSe passivation layer was deposited on the laser cavity facets. For the original device the catastrophic optical damage (COD) occurred when the output power was 2.5 W. The ZnSe passivated device did not show COD phenomenon until 10.1 W. When the current was 10 A, the output power was 10.1 W, and the electro-optical conversion efficiency was 54%. Before and after the wavelength being locked by the volume Bragg grating (VBG), the full width at half maximum of the spectrum were 2.6 nm and 0.06 nm, respectively, and the wavelength range was about 230 pm through controlling the temperature of VBG.
Low-stress mounting technology of large aperture mirror
Zheng Shengheng, Ma Wenjing, Yang Ying, Cao Tingfen, Chen Xiaojuan, Guo Yuyuan, Liao Yuzhen, Zhang Xin, Han Wei, Deng Xuewei, Hu Dongxia
2021, 33: 091002.   doi: 10.11884/HPLPB202133.210176
[Abstract](87) [PDF 1369KB](11)
The high-power solid-state laser facility puts forward stringent requirements for the additional wavefront distortion and attitude stability of the large-aperture mirror. While ensuring attitude stability, the peak-to-valley (PV) value of additional wavefront distortion caused by low-stress mounting is required to be less than λ/3 (wavelength λ=633 nm). In this paper, a mounting technology of large aperture mirror with three-point front support and eight point side fixing is proposed. The additional wavefront distortion caused by the mounting structure is simulated and experimentally studied. And the attitude stability of mirror under different working conditions is experimentally researched. The results show that the PV value of additional wavefront distortion introduced by this mounting method is about 23.6 nm, and the PV value of the mirror pointing under different conditions of vibration, shaking, and flipping is less than 50 μrad. The additional wavefront distortion and attitude stability meet the requirements of high-power lasers.
Experimental study of high yield neutron source based on multi reaction channels
Cui Bo, Zhang Zhimeng, Dai Zenghai, Qi Wei, Deng Zhigang, Huang Hua, He Shukai, Wang WeiWu, Teng Jian, Zhang Bo, Liu Hongjie, Chen Jiabin, Xiao Yunqing, Wu Di, Ma Wenjun, Hong Wei, Su Jingqin, Zhou Weimin, Gu Yuqiu
2021, 33: 091003.   doi: 10.11884/HPLPB202133.210330
[Abstract](23) [PDF 1140KB](1)
The short-pulse neutron source based on ultra-short and ultra-intense laser is an ideal neutron source for ultra-fast neutron detection. For many applications of the novel laser neutron source, the neutron yield now becomes a major limitation. It is proposed here that, based on the Target Normal Sheath Acceleration mechanism (TNSA) and the beam-target reaction scheme, the adoption of composite component target LiD as the neutron converter can be an effective path to enhance the neutron yield. Compared with the traditional LiF converter, which has two typical reaction channels p-Li and d-Li, the use of LiD converter has the advantages on introducing two more reactions channels, i.e., p-D and d-D. Therefore, more reaction channels are expected to be beneficial for increasing the neutron yield. It is experimentally demonstrated that by using LiD converter, an enhancement of 2−3 folds of neutron yield is achieved compared with the LiF converter. As a result, a neutron beam with the highest yield of 5.2×108 sr−1 with a forward beamed distribution is well obtained. The contribution of multi reaction channels is also identified, indicating the enhancement of neutron yield mainly comes from the p-D reaction.
Automated alignment research on off-axis eight-pass laser amplifier
Chen Zhifei, Yao Ke, Fan Chen, Tang Jun, Lǚ Mengjie, Lu Zhenhua, Gao Song, Xie Xudong, Fu Xuejun, Fan Mengqiu, Zheng Kuixing, Chen Bo, Peng Zhitao, Feng Bin
2021, 33: 091004.   doi: 10.11884/HPLPB202133.210207
[Abstract](30) [FullText HTML](19) [PDF 934KB](0)
We present a technical research experimentally demonstrating automated alignment on off-axis eight-pass laser amplifier, the mentioned technique aims to replace manual alignment method with automatic alignment system on the multipass complex laser amplifier, of which the efficiency, accuracy, and output beam quality would get spectacularly improved. This technique realizes precise reference mark of pinhole spatial centre position in the spatial filter of off-axis eight-pass laser amplifier via main laser lighting and image relaying system. And the far-field facula is processed by edge detection so that the beam pointing centre is obtained. Based on difference between beam centre position and reference, we realizes closed loop automated alignment on the amplifier system via two-dimensionally controlling specific reflector frames. Additionally we indicate that the experimental results of the research fairly satisfied requirements for efficiency and accuracy of off-axis eight-pass laser amplifier, and verified feasibility of the alignment technique applied in the amplifier as well.
Design of photonic crystal fibers with low loss broadband near-zero dispersion and high nonlinearity
Du Hailong, Zheng Yi, Pang Xuemin
2021, 33: 091005.   doi: 10.11884/HPLPB202133.210221
[Abstract](27) [PDF 1638KB](2)
A photonic crystal fiber (PCF) structure with low loss, broadband near-zero dispersion and high nonlinearity is proposed. The diameter of the air hole in the cladding increases gradually from the core to the cladding. The dispersion, loss and nonlinear characteristics of the PCF are analyzed by the multipole method through changing the air hole spacing, diameter and the number of air hole layers. Finally, the variation law of each characteristic is obtained and the optimal structure parameters of PCF are designed. The results show that the fiber has three zero dispersion points, the dispersion and dispersion slope is less than 0.27 ps·nm−1·km−1 and 0.008 ps·km−1·nm−2 respectively between 1.25 μm and 1.55 μm, and the loss is 0.021 dB/km at 1.55 μm. The nonlinear coefficients are 78.6 W−1·km−1, 60.4 W−1·km−1, and 38.2 W−1·km−1 at the femtosecond laser pumping wavelength 0.8 μm, 1.06 μm and 1.55 μm respectively.
Simulation analysis of ultrasonic vibration for laser ablation of aluminum surface temperature field
Wang Yan, Yin Jie, Dong Yinghuai, Li Yuehua, Cheng Zizheng, Zhao Jingnan, Yang Shuo
2021, 33: 091006.   doi: 10.11884/HPLPB202133.210160
[Abstract](8) [PDF 1223KB](0)
In view of the influence of ultrasonic vibration on the temperature field of laser ablation of aluminum surface, a three-dimensional numerical model was established, and the temperature field of ultrasonic vibration assisted laser ablation of metal aluminum was numerically simulated by using ANSYS software. By comparing the change of temperature field of two adjacent spots with time under different laser scanning speed and ultrasonic vibration frequency, it is found that the temperature, size and position of adjacent spots all change. The numerical results show that with the increase of laser scanning speed, the maximum temperature of laser scanning to the same position decreases, and the depth of craters becomes shallow. Due to the displacement of medium molecules caused by ultrasonic vibration, when the ultrasonic vibration frequency is 15 kHz, the temperature of the crater decreases significantly and the crater position is misplaced in the direction of vibration, which is conducive to the generation of a new laser action trajectory. These experimental results have a certain guiding effect on the design of ultrasonic vibration assisted laser control parameters.
Inertial Confinement Fusion Physics and Technology
Sealed X-ray framing tube with CsI photocathode to achieve high detection efficiency and stability
Yang Yang, Zhu Bingli, Gou Yongsheng, Chen Zhen, Bai Xiaohong, Qin Junjun, Bai Yonglin, Liu Baiyu, Xu Peng, Wang Bo, Cao Weiwei
2021, 33: 092001.   doi: 10.11884/HPLPB202133.210192
[Abstract](65) [PDF 1119KB](2)
A hermetically sealed X-ray framing tube with CsI photocathode is proposed to solve the problems of poor stability and low detection quantum efficiency brought by the open structure framing tube with Au photocathodes. Two microstrip photocathodes of 100 nm Au and 100 nm CsI are fabricated to compare their sensitivities under the same environmental conditions. The structure and the fabrication process of the sealed framing tube are described inthispaper. After fabrication, the sealed framing tube is tested to verify its performance. The measurement shows that exposure time of the proposed framing tube is 65 ps when gated by an ultrafast pulse with 200 ps width and −2.7 kV amplitude. At static mode, the image intensity of the CsI photocathode is 3.4 times that of the Au photocathode under the irradiation of non-monochromatic high energy X-ray source. Its static response intensity is reduced to 83% compared with the initial value after being stored in the laboratory air for 1000 h. These results indicate that the sealed framing tube with CsI photocathode can achieve higher detection efficiency and stability, and can effectively improve the quality and reliability of X-ray framing imaging.
White light spectroscopy technology for measuring the uniformity of capsule shell thickness
Fan Ting, Ma Xiaojun, Wang Zongwei, Wang Qi, He Zhibing, Yi Yong
2021, 33: 092002.   doi: 10.11884/HPLPB202133.210179
[Abstract](29) [PDF 888KB](0)
To measure accurately the thickness and its distribution of capsule, the white light reflection spectrum measurement technology is studied. The basic principle of white light reflection spectrum and the corresponding data processing methods, such as the extreme value method, the peak fitting method and the interference order correction method, are analyzed. Based on the white light reflection spectrum and the precision rotary axis system, the measuring apparatus applied to determine the shell thickness and its distribution of the capsule is developed. The white light reflectance spectrum measurement, data processing and reliability verification experiments of GDP capsule are carried out and the circular thickness distribution curve of capsule is obtained. The research results show that the thickness and its distribution of capsule can be measured accurately by white light reflectance spectrum technology based on spectral peak fitting method and interference order correction method and the measurement error is less than 0.1 μm.
High Power Microwave Technology
Study on GIC algorithm of railway traction power supply system under action of late time HEMP
Gao Zhiwei, Zhou Yuxiang, Zhu Siyi
2021, 33: 093001.   doi: 10.11884/HPLPB202133.210061
[Abstract](54) [PDF 1145KB](3)
The late effect of high-altitude electromagnetic pulse (E3) will cause dramatic changes in the Earth's magnetic field and form a ground induced electric field. The induced electric field is equivalent to forming a loop between the excitation source and the ground long-distance conductor and the Earth, generating a geomagnetic induction current (GIC). GIC can cause DC bias of the transformer in the traction power supply system, thereby seriously threatening the safe operation of the traction power supply system. Based on the plane wave theory, the layered Earth conductivity model and the circuit model of the traction power supply system, this paper proposes the GIC algorithm of the traction power supply system under the action of E3, and takes the railway traction power supply system with return line direct power supply as an example. Calculating the system GIC situation shows that the GIC in the traction power supply system under this power supply mode is far greater than the withstand value of the transformer and other equipment in the system. The study provides support for further research on the effect of the traction power supply system under the action of E3, the selection of our domestic railway equipment, and disaster prevention.
Self-consistent nonlinear numerical simulation of millimeter wave gyro-klystron amplifiers
Zhang Dian, An Chengxiang, Zhang Jun, Zhang Jiande, Zhong Huihuang
2021, 33: 093002.   doi: 10.11884/HPLPB202133.210129
[Abstract](29) [PDF 892KB](1)
To realize quick design of the gyro-klystron amplifiers, a kind of numerical simulation method based on the single mode self-consistent nonlinear theory of gyrotrons was investigated. The single mode theory can’t be used to match the disrupt boundary conditions of the input and the middle cavities of the gyro-klystrons, thus the input and the middle cavities can only be processed through single mode theory based on given field distributions. As for the output cavities with smooth boundaries at the power output ends, the single mode nonlinear simulation could be self-consistent. A millimeter wave two cavity gyro-klystron amplifier with reported detailed parameters was simulated using the developed single mode theory. The effectiveness of the numerical simulation was verified by comparing the simulation results with those obtained in a commercial particle in cell (PIC) simulation tool.
Analysis of high-frequency atmospheric windows for terahertz communication between the ground and the satellite
Cao Xiangchun, Hao Jianhong, Zhao Qiang, Zhang Fang, Fan Jieqing, Dong Zhiwei
2021, 33: 093003.   doi: 10.11884/HPLPB202133.210186
[Abstract](108) [PDF 1108KB](3)
The large path loss limits the transmission distance of terahertz wireless communication in the atmosphere. To realize long-range transmission of terahertz waves between the ground and the satellite, the first and key step is to find low attenuation atmospheric transparent windows. In this paper, based on the characteristics of atmospheric distribution in China, atmospheric model (am) is used to compute and compare atmospheric absorption attenuation of terahertz waves in two representative cities, and obtain the most ideal ground-based site suitable for terahertz communication between the ground and the satellite in China. Subsequently, by means of real atmospheric data and layered transmission theory, the total path loss of terahertz communication between the ground and the satellite is calculated. Combined with the signal transmit power, antenna gain, Signal-to-Noise Ratio (SNR), noise power and the corresponding path loss threshold, the total usable bandwidth and atmospheric windows in the 10−15 THz frequency band are given. Moreover, by taking the High Altitude Platform as the terahertz communication relay link between the ground and the satellite, the usable atmospheric windows in the 1−15 THz frequency band with antenna gain of 0−100 dBi are given, which provide theoretical and numerical reference for the establishment of ground-satellite communication links and the selection of ground-based sites and communication frequency bands in China.
Physical modeling and particle simulation technology of multi-pulse MILO cathode outgassing ionization
Yang Yulin, Dong Zhiwei, Sun Huifang, Yang Wenyuan, Zhang Fang
2021, 33: 093004.   doi: 10.11884/HPLPB202133.210121
[Abstract](88) [PDF 1453KB](5)
The commutation phenomena produced by cathode outgassing ionization is a possible factor to limit work performance of magnetically insulated transmission line oscillator (MILO), and also is the main obstacle to limit its repeat frequency. In this paper, physical modeling technology of MILO cathode outgassing ionization phenomena and three-dimensional particle simulation are presented. The relation between remaining gas of previous outgassing and pulse duration is analyzed. When the number of positive ions is greater than that of electrons the plasma caused by the ionization will rapidly reduce microwave output power.
Design and validation test of high-altitude electromagnetic pulse conductive protector module for wireless communication system
Du Chuanbao, Mao Congguang, Cui Zhitong, Sun Dongyang, Hao Jia, Wu Wei, Chen Wei, Wu Zhiqiang, Qiu Yang
2021, 33: 093005.   doi: 10.11884/HPLPB202133.210155
[Abstract](57) [PDF 1548KB](4)
To improve the anti-HEMP ability of very high frequency wireless communication systems, based on the vulnerability analysis results in the early stage, the design principle and indicators of the combination of transient discharge and steady-state filtering were determined, and the protector module sample was produced. The 20 ns/500 ns conduction injected waveform was used to carry out the pulsed conducted injection test for the protector sample. Compared with the original protector, the peak of the residual current was reduced by 60%, the start time was shortened by 75%, the action time was shortened by 80%, and the low-frequency energy limit of the injected waveform below 20 MHz was increased by 1 order of magnitude. A VHF wireless communication system was taken as the test product, and the protection validation test was carried out. The test illustrated that the residual current peak is controlled below 10 A, and the function and performance of the tested system are norm, which verifies the effectiveness of the designed protector module.
Oscillation properties of ion channel during long-range propagation of electron beam
Xue Bixi, Hao Jianhong, Zhao Qiang, Zhang Fang, Fan Jieqing, Dong Zhiwei
2021, 33: 093006.   doi: 10.11884/HPLPB202133.210187
[Abstract](81) [PDF 1385KB](3)
It is known that the ion channel can limit the radial expansion of the electron beam during long-range propagation in the plasma environment. Previous research typically concentrated on the interaction between the beam and plasma, but research on the establishment and transient properties may lay the foundation for understanding and using the ion channel during long-range propagation. In this study, a series of 2D particle-in-cell simulations is performed and an analytical model of ion channel oscillation is constructed according to the single-particle-motion. The results show that the ion channel established by relativistic electron beam in the plasma continues to oscillate periodically during the long-range propagation of relativistic electron beam. The beam electron density, initial beam radius and the plasma density can influence the dynamics of the ion channel oscillation. Choosing suitable beam parameters based on the various plasma environment can contribute to the improvement of the stability of the ion channel and further the beam quality.
Study on nonstationary oscillation in continuous frequency tunable terahertz gyrotron
Zhao Qixiang, Feng Jinjun, Lü You, Zheng Shuquan, Zhang Tianzhong
2021, 33: 093007.   doi: 10.11884/HPLPB202133.210205
[Abstract](148) [PDF 3029KB](13)
Terahertz gyrotron can achieve high output power and has a certain frequency tuning range, thus it is an ideal high power terahertz radiation source for NMR spectroscopy system. A 263 GHz, TE5,2 fundamental harmonic frequency continuously tunable gyrotron is designed, the corresponding frequency tuning range can reach 1.4 GHz through adjusting the magnetic field. The unstable oscillation state of the designed gyrotron is studied by using the time domain multi-mode multi frequency self-consistent nonlinear theory. The results show that in the magnetic field range of low order axial mode, when the operating current is greater than the starting current, the continuously tuned gyrotron enters the stable state, where the high order axial mode is suppressed, and the output power of TE5,2 remains unchanged with time. When the current increases, the competition between axial modes causes the gyrotron to enter the unstable oscillation state from the stable state, the output power of TE5,2 oscillates with time and the interaction efficiency decreases greatly. With the further increase of current, the gyrotron returns to another stable state different from that of low current. It is also found that the initial current increases with the increase of magnetic field. The research of this paper has a certain guiding significance for the development of continuously tuned THz gyrotron for DNP-NMR applications.
Particle Beams and Accelerator Technology•Overview
Machine learning applications in large particle accelerator facilities: review and prospects
Wan Jinyu, Sun Zheng, Zhang Xiang, Bai Yu, Tsai Chengying, Chu Paul, Huang Senlin, Jiao Yi, Leng Yongbin, Li Biaobin, Li Jingyi, Li Nan, Lu Xiaohan, Meng Cai, Peng Yuemei, Wang Sheng, Zhang Chengyi
2021, 33: 094001.   doi: 10.11884/HPLPB202133.210199
[Abstract](64) [PDF 1491KB](16)
Rapid growth of machine learning techniques has arisen over last decades, which results in wide applications of machine learning for solving various complex problems in science and engineering. In the last decade, machine learning and big data techniques have been widely applied to the domain of particle accelerators and a growing number of results have been reported. Several particle accelerator laboratories around the world have been starting to explore the potential of machine learning the processing the massive data of accelerators and to tried to solve complex practical problems in accelerators with the aids of machine learning. Nevertheless, current exploration of machine learning application in accelerators is still in a preliminary stage. The effectiveness and limitations of different machine learning algorithms in solving different accelerator problems have not been thoroughly investigated, which limits the further applications of machine learning in actual accelerators. Therefore, it is necessary to review and summarize the developments of machine learning so far in the accelerator field. This paper mainly reviews the successful applications of machine learning in large accelerator facilities, covering the research areas of accelerator technology, beam physics, and accelerator performance optimization, and discusses the future developments and possible applications of machine learning in the accelerator field.
Particle Beams and Accelerator Technology
Drive laser shaping and transport system for photocathode RF gun
Li Cheng, Wang Wenxing, Li Weiwei, Zhang Haoran, Jiang Shimin, Gao Panyun, He Zhigang, Zhang Shancai
2021, 33: 094002.   doi: 10.11884/HPLPB202133.210091
[Abstract](25) [FullText HTML](13) [PDF 1086KB](6)
To meet the requirements of Hefei Advanced Light Facility (HALF) for high quality injection beam, a photocathode RF gun is developed as the electron source of the injector in the R&D project. To obtaining an electron beam with high qualities, it is necessary to carry out experimental research on drive laser shaping and transport system. For suppressing the beam emittance growth caused by space charge force, the temporal pulse shape is modified by using birefringent crystals, while an aperture is used for spatial pulse shaping. An optical image transport system is designed to achieve high stability of the laser beam position on the photocathode. Detailed design of the optical system is presented in this paper. The experimental result shows that a quasi uniform distribution in the three-dimensional space of laser pulse is obtained, and the laser beam position jitter on the photocathode is less than 4 µm. The performance of the laser pulse meets the experiment requirements.
Novel electron source based on interaction between high power laser and metal wire
Yin Jiapeng, Yuan Xiaohui, Zhou Zusheng, Pei Guoxi, Liu Shengguang
2021, 33: 094003.   doi: 10.11884/HPLPB202133.210244
[Abstract](37) [FullText HTML](20) [PDF 1074KB](8)
Electron source generates electron bunch and dominates the electron beam quality for an accelerator. We put forward a novel mechanism of electron source in this paper. A great amount of hot electrons with several hundred keV can be generated during the interaction process between high power laser and metal wire, and some of them fly forward along the wire, guided by EM field. We generate electron beam and measure beam parameters downstream the Au wire, W wire and Cu wire experimentally. 3 nC electrons can be collected by a Faraday-cup for a single shot. Electron energy spectrum is between 0−240 keV continually, and there is a density peak at 100 keV. RF buncher cavity can be used to compress the bunch length short enough for further RF acceleration in main accelerator. Start-to-end simulation has been done with ASTRA code. Electron beam with 55 ps length and 1 nC charge is injected into a 2-cell RF buncher cavity, it can be compressed into 27 ps long, which satisfies the general requirement of the main accelerator on the electron source.
Study and implementation of automatic gain calibration method for 4-channel digital beam position monitor
Gao Guodong, Cao Jianshe, Liu Zhi, Du Yaoyao, Ye Qiang, Ma Huizhou, Sui Yanfeng, Yue Junhui, He Jun, Xu Taoguang, Yang Jing, Zhang Xing’er, Tang Xuhui, Wei Shujun
2021, 33: 094004.   doi: 10.11884/HPLPB202133.210202
[Abstract](86) [PDF 1094KB](9)
The accuracy of beam position measurement is affected by the gain inconsistency of the four channels of the digital BPM. Based on the existing hardware and the requirement of beam position monitor (BPM) measurement accuracy, a design for automatic calibration of digital BPM sample data gain is implemented by Verilog language in the self-made electronics. Firstly, the system design of automatic gain calibration module is introduced. Secondly, the realization method of the module is described in detail, and the ADC data automatic gain calibration test platform is designed and built to verify the function of the automatic gain calibration module. Finally, the application of this design in BPM channel calibration is introduced. Test results show that this method achieves 4-channel gain consistency and makes the data amplitude after ADC sampling equal. This method effectively solves the measurement bias caused by channel gain inconsistency and the difficulty of ADC data amplitude calibration in engineering application. It will play an important role in the automatic channel calibration of BPM system.
Safety control system for HEPS insertion device based on new safety architecture
Zhao Shutao, Cao Jianshe, Lu Huihua, Sun Shuchen, Gong Keyun, Sun Yajun, Zhang Xiangzhen, Li Xiaoyu, Zhang Lei, Li Yuhui, Li Zhiqiang, Chen Wan, Gong Lingling, Guo Qing, Huang Yongsheng, Yang Yanwei
2021, 33: 094005.   doi: 10.11884/HPLPB202133.210087
[Abstract](19) [PDF 1088KB](0)
The control system of Insertion Device (ID) for High Energy Photon Source (HEPS) is mainly responsible for the opening and closing motion control of the magnetic gap of ID. The safe movement of the ID control system is essential for the safety of ID, storage ring and beamline station. Based on the safety requirements of HEPS ID control system, a high-level and multi-level safety system based on the new safety architecture has been designed and applied. It is the first time that this kind of safety system has been applied to the same type of ID control system worldwide. The safety system is designed and implemented in accordance with international safety standards and achieves the high safety level of Safety Integrity Level. The safety system has been successfully applied in the Cryogenic Permanent Magnet Undulator (CPMU) for HEPS, and the systematic tests have been accomplished. These tests results show that the safety system meets all the expected safety specifications, and achieves the standard of industrial control system with high safety level.
Pulsed Power Technology
Development of a 3 MV transfer capacitor used in an electromagnetic pulse simulator
Chen Zhiqiang, Xie Linshen, Jia Wei, He Xiaoping, Tang Junping, Chen Weiqing
2021, 33: 095001.   doi: 10.11884/HPLPB202133.210195
[Abstract](896) [PDF 1091KB](18)
The design process and experimental results of a transfer capacitor used in a large vertical polarization bounded wave simulator are introduced. The capacitor adopts modular design based on capacitor elements and components, and forms a cone shape. The shell is made of vacuum process glass fiber reinforced plastic material. The capacitance value of capacitor is determined by the equivalent two-stage pulse compression circuit of the simulator, which is calculated to be 1.8 nF. The internal insulation medium of capacitor is dodecyl benzene, while the external insulation environment is 45# transformer oil. The designing working voltage is 3 MV, and the capacitor’s insulation length is mainly determined by the body insulation characteristics of capacitor elements. Three-dimensional electromagnetic simulation is used to estimate the inductance of the circuit composed of capacitor and switch, and the result is close to the measured data 623 nH. The measurement for the pulse voltage of capacitor is achieved by integrating the current of the capacitor, and the acquisition of the current is realized by a measurement module which consists of three oxidation film resistors in parallel and encapsulated in SF6 gas. The actual operation data show that the designed capacity of the transfer capacitor is achieved and the calibration coefficient of the measuring device is stable and the working voltage can reach up to 3.1 MV.
Fractional-turn ratio solid-state modulator for 50 MW klystron
Li Yunhai, Guo Xiang, Yang Rong, Ruan Zheng, Tong Yi, Xie Xiaofeng
2021, 33: 095002.   doi: 10.11884/HPLPB202133.210220
[Abstract](57) [PDF 1324KB](6)
This paper introduces The fractional ratio pulse modulator for S-band 50 MW klystron, which has the characteristics of pulse transformer ratio of 1∶300, primary voltage of 1.25 kV and output peak power of 113 MW. The selection of five sub cores, the design of transformation ratio, the calculation of primary voltage and current, and the calculation of average output power are carried out. It is analyzed that the total inductance of single discharge circuit which affects the output front of solid-state modulator should be less than 0.4 μH. The loop inductance is distributed in the discharge module, the discharge cable, the internal wiring of the pulse transformer and the primary leakage inductance. The low inductance design of the internal loop of the discharge module, the low leakage inductance design of the pulse transformer and the modeling and simulation results are mainly analyzed. The results show that the high-power all solid-state pulse modulator with 312 kV output pulse voltage, 360 A pulse current and less than 1.4 μs front and back edges can be realized. It has promising applications in the fields of accelerator driving RF power source, high-power radar transmitter and so on, which need high-voltage pulse modulator.
Nuclear Science and Engineering
Short-circuit impedance design for converter transformer of superconducting magnet power supply for CRAFT
Huang Ronglin, Fu Peng, Huang Liansheng, Xu Liuwei, Gao Ge, He Shiying
2021, 33: 096001.   doi: 10.11884/HPLPB202133.210088
[Abstract](72) [PDF 1122KB](2)
The superconducting magnet power supply for the Comprehensive Research Facility for Fusion Technology (CRAFT) has the abilities of large current steady-state operation, high power pulse operation and transient fault suppression, which is closely related to the short circuit impedance of converter transformer. On the basis of parameters of AC system and equivalent circuit model of converter transformer, the relationship between the performance of superconducting magnet power supply and the short circuit impedance of converter transformer is studied. The research shows that the small short circuit impedance is beneficial to the output voltage and the reactive power loss of superconducting magnet power supply, but the short-circuit fault current and harmonic current increase accordingly. For short-circuit impedance design for converter transformer purposes, firstly, short-circuit impedance must satisfy the transient fault suppression capability and the rated output voltage, and secondly, it is easy to suppress the high characteristic harmonic current brought by thyristor multi-phase converter for CRAFT, hence small short-circuit impedance should be chosen.
Advanced Interdisciplinary Science
Error analysis of incoherent imaging binocular vision system
Huang Hongjiang, Wang Xin, Chu Xiuxiang
2021, 33: 099001.   doi: 10.11884/HPLPB202133.210045
[Abstract](25) [PDF 1212KB](0)
There are many factors that affect the measurement accuracy of binocular vision system. Currently, the influence of system structure parameters on the measurement accuracy mainly includes the angle between optical axis and baseline, baseline distance, horizontal viewing angle, object distance and lens focal length. Since the aperture size directly affect the imaging resolution, it is the core factor that determines the accuracy of binocular vision measurement. Consequently, according to the incoherent imaging theory, the binocular imaging process is simulated and tested. Moreover, Speeded Up Robust Features algorithm is adopted to extract and match the features of the image pairs to obtain their parallax values. The parallax root mean square error is calculated to represent the systematic errors. The results show that the system error decreases with the increase of lens aperture, and approaches saturation. This research can provide theoretical and experimental basis for the selection of system parameters and aperture size during the design of the binocular system.