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Just Accepted manuscripts are peer-reviewed and accepted for publication. They are posted online prior to technical editing formatting for publication and author proofing.
Display Method:
Research on the influence of cutting parameters on the frequency characteristics of KDP surface topography
Kuang Liangjie, Pang Qilong, Chen Mingjun, Ma Luqiang, Xu Youlin
Accepted Manuscript  doi: 10.11884/HPLPB202032.190262
[Abstract](365) [PDF 1612KB](12)
Abstract:
The influence of cutting parameters on the frequency characteristics of optical crystal surface has been studied. The experiment of single point diamond turning has been adopted to process KDP crystal. The frequency distribution of surface profile has been obtained by power spectral density. The continuous wavelet method is used to evaluate the influence of cutting depth, feed rate and spindle speed on machined surface. The results show that the frequency characteristics reflect the effects of cutting parameters on surface topography. The wavelength and amplitude of mid frequency embody the change of cutting depth and spindle speed, and amplitude increases with the increase of cutting depth and speed. Low frequency reflects the change of feed rate, and the amplitude becomes small as feed rate decreases. High frequency is the manifestation of vibration and material anisotropy in processing. Therefore the analysis of frequency characteristics on surface topography provides a reference value for selecting the optimal process parameters.
Research on Lidar scanning mode
Yuan Guangfu, Ma Xiaoyu, Liu Shuang, Yang Qilong
Accepted Manuscript  doi: 10.11884/HPLPB202032.190382
[Abstract](126) [PDF 838KB](2)
Abstract:
Scanning Lidar is widely used in atmospheric remote sensing detection and target capture. In order to realize the effective detection of Lidar, four common scanning modes of Lidar, raster scanning, Lissajo scanning, Spiral scanning and hexagonal scanning, are studied in this paper. The corresponding scanning equation is deduced, and the physical meaning and adjustment method of parameters are discussed. Aiming at the requirement of fine scanning in atmospheric remote sensing detection, the distribution of spot under raster scanning and hexagonal scanning is studied. The leakage rate and overlap rate of two scanning modes are simulated and analyzed. The results show that under the same scanning condition, the leakage area of hexagonal scanning mode is the least. The physical image and scan pattern of scanning control system based on the above research contents are presented. Finally, the characteristics of four scanning modes are summarized, and their application and suggestions are given.
Characteristics analysis of electrohydraulic shockwave
Wu Min’gan, Liu Yi, Lin Fuchang, Liu Siwei, Sun Jianjun
Accepted Manuscript  doi: 10.11884/HPLPB202032.190356
[Abstract](124) [PDF 1279KB](2)
Abstract:
Characteristics of electrohydraulic shockwave are the keys to the application of electrohydraulic disintegration of rocks(EHDR), mathematical models are used to characterize the generation and propagation of the shockwave, an integrated experimental platform is established, the measured and simulated results of typical shockwave characteristics are analyzed. The simulated results of characteristics of shockwaves under different charge voltage are given, and the influence of charge voltage on the shockwave characteristics are analyzed. The results show that the peak value and energy of shockwave is 2.67 MPa and 27.30 J respectively, the wave front time is 2.16 μs, the loading rate is 1.24 MPa/μs, when the charge voltage is 11 kV. The peak value and energy of shockwaves increase, the wave front time decrease, the loading rate of shockwaves increase, while the efficiency of electrical energy transfer into shockwave energy decrease, when the charge voltage of capacitor raise. Characteristics of shockwaves can be predicted from the parameters of discharge circuit through the simulation method, which can provide theoretical basis for further study on the morphology and effect of EHDR.
New type of high power energy calorimeter with full absorption
Zhang Cuicui, Wang Yi, Wang Jianzhong, He Bin, Yu Mingmei
Accepted Manuscript  doi: 10.11884/HPLPB201931.190351
[Abstract](158) [PDF 1054KB](2)
Abstract:
In order to solve the problem of the existing HPM radiation field power density measurement system, such as many measurement links, complex system and long cable which can’t adapt to complex electromagnetic environment measurement, a miniaturized and integrated power density measurement system of high-power microwave radiation field is developed in this paper. A antenna-coupler-adapter is used as the front receiver, the back end of the system is coaxial signal processing unit, where the attenuation, power detection and electro-optical conversion is achieved in the shield box, so, the system can be measured and monitored remotely. Meanwhile, modular calibration is applied in the system, which can effectively reduce the measurement uncertainty. The system has 30 dB dynamics, a minimum measurable pulse width of 50 ns and a measurable radiation field power density of 100 MW/m2, the system is compact structure, and is easily to carry, anti-electromagnetic radiation, and power density measurement of GW high-power microwave radiation field in X-band can be realized immediately.
Comparison of insulation properties of several liquid dielectrics under nanosecond pulse
Jia Wei, Chen Zhiqiang, Guo Fan, Li Yaoyao, Qi Yuhang, Chen Yongping, Yang Tian
Accepted Manuscript  doi: 10.11884/HPLPB202032.190338
[Abstract](982) [PDF 760KB](1)
Abstract:
Based on the self-developed nanosecond pulsed test platform with output voltage of 30 ns risetime and 100 ns half width, and the standard dielectric strength DC tester, the breakdown characteristics of four liquid dielectrics (transformer oil, glycerol, deionized water and Galden HT200) under DC and nanosecond pulse were experimentally studied and compared. And the following conclusions were obtained: (1)Under both DC and nanosecond pulse, Galden HT200 has the highest breakdown field strength which is more than 40% higher than the transformer oil. (2) Under the nanosecond pulse, the breakdown field strength of Galden HT200 and transformer oil both increased by 6.5-7 times than those under DC. And it took the shortest time(nanosecond scale) for Galden HT200 to breakdown, followed by the transformer oil(20 ns), then glycerol(45 ns) and deionized water(70 ns). (3) After multiple breakdowns, a lot of carbonized discharge products are accumulated at the electrode gap in the glycerol which has the largest viscosity coefficient. However, there are no obvious breakdown traces in the Galden HT200 and deionized water, which both have the smaller viscosity coefficient. But obvious shock waves were observed in the Galden HT200 and deionized water, which make the gap electrodes to loosen.
High-performance multifunctional apparatus for studying secondary electron emission characteristics of dielectric
He Yun, Yang Jing, Miao Guanghui, Zhang Na, Cui Wanzhao
Accepted Manuscript  doi: 10.11884/HPLPB202032.190318
[Abstract](119) [PDF 847KB](1)
Abstract:
The paper introduces a high-performance multifunctional apparatus for studying secondary electron emission characteristics of dielectric. The apparatus is equipped with a collector containing three grids and a 30 eV−30 keV electron gun, the secondary electron emission characteristics of dielectric can be measured under ultra-high vacuum, and in-situ XPS spectrometer, heating and argon ion sputtering can also be performed. The paper also introduces the measurement of secondary electron yield by pulse method, gives the measured secondary electron current pulse of gold and Al2O3, the charging saturation time and influence of the thickness of dielectric on the charge amount are obtained by judging the change of the current pulse waveform with time and the number of irradiations.
Effect of residual polishing particles on the thermal damage characteristics of materials in surface scratches
Guo Wenhua, Tao Ye, Zhang Rongzhu
Accepted Manuscript  doi: 10.11884/HPLPB202032.190303
[Abstract](92) [PDF 893KB](1)
Abstract:
A thermal damage analysis model of scratches and residual polishing particles on the optical surface is established. The thermal damage properties of optical materials under such complex defects are studied. The finite difference method was used to calculate the light field modulation and temperature field distribution of the optical material surface at different positions of the polished particles at different scales. According to the surface temperature distribution, the thermal damage threshold of the optical material under the corresponding conditions is achieved. The results show that in addition to the influence of the polishing particle radius on the material damage threshold, when the polishing particles are located at different positions in the scratch width direction, the thermal damage threshold of the material will also change significantly. Among them, the polishing particles in the center of the scratch have the strongest modulation on the light field, and are more likely to cause melting damage of the material.
Operation stability improvement for synchrotron light sources by tune feedback system
Wu Xu, Tian Shunqiang, Zhang Qinglei, Zhang Wenzhi
Accepted Manuscript  doi: 10.11884/HPLPB202032.190270
[Abstract](150) [FullText HTML](71) [PDF 806KB](2)
Abstract:
Ten Insert Devices (IDs) had been installed in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The ID gaps were repeatedly adjusted for the scientific experiments during the user time. The residual quadrupole errors beyond the ID feedforward disturbed the beam optics, including the betatron tune deviations that spoiled machine performance and brightness stability. A tune feedback system was developed and implemented in the SSRF storage ring to resolve the deterioration. The tune stability of ±0.001 in 2 weeks was reached. Another important function of this feedback system is finding out slow drift in the power supplies of dipole or quadrupole by observing the correction current changes in the feedback. To prove this feedback’s feasibility, we compared variations of the beam parameters, including the injection efficiency, the beam life-time, the horizontal beam size and the beta-beatings.
Compact balanced bandpass filters based on multilayered dual-mode substrate integrated waveguide cavities
Lü Dalong, Liu Qing, Zhang Junjie, Zhang Dewei, Zhou Dongfang
Accepted Manuscript  doi: 10.11884/HPLPB202032.190199
[Abstract](102) [PDF 1083KB](3)
Abstract:
To design size-reduced balanced bandpass filters (BPFs) with high selectivity, two new multilayered dual-mode substrate integrated waveguide (SIW) balanced BPFs are proposed. Firstly, the characteristic of dual-mode SIW cavity is analyzed in detail. Then, a balanced SIW BPF with balanced input/output (IO) ports locating on the upper dual-mode SIW cavity is proposed, and the lower dual-mode SIW cavity is coupled to the upper one using two crossed slots. Three transmission zeros (TZs) can be produced at any locations. A balanced SIW BPF with balanced IO ports locating on the upper and lower dual-mode cavities respectively is also proposed, and the two cavities are coupled by a slot. Two symmetrical TZs can be produced. Based on the proposed structures, two filters with center frequency of 10 GHz are designed, fabricated and measured. The measured results agree well with simulated ones, which indicates the feasibility of the proposed multilayered dual-mode SIW balanced BPFs with compact size and high selectivity.
Electron beam introduction of Ka-band coaxial multi-beam relativistic klystron amplifier
Dang Zhiwei, Li Shifeng, Wang Zhanliang, Huang Hua, Wang Tengfang, Liu Zhenbang, Gong Yubin
Accepted Manuscript  doi: 10.11884/HPLPB202032.190192
[Abstract](126) [PDF 995KB](0)
Abstract:
The Ka-band high power microwave coaxial multi-beam relativistic klystron amplifier is a potential device. This paper firstly determines the main factors affecting the efficiency of multi-injection electron beam introduction and preliminary structural parameters through theoretical analysis. Secondly, the Ka-band relativistic multi-beam diode model is established by three-dimensional particle simulation software to optimize the structural parameters. The final efficiency of electron beam introduction can reach 89%. Finally, an experimental study on the generation and transmission of electron beams was carried out to verify the results of particle simulation. Under the condition of electron beam voltage 502 kV, beam current 4.34 kA, axial magnetic induction strength 0.76 T, the electron beam introduction efficiency reached 72%. The electron beam pattern obtained by electron beam bombardment of the nylon target indicates that the shape of the electron beam is not distorted during generation and transmission. The generated electron beam diameter is about 2 mm. The simulation and experimental results show that the designed high-current multi-beam diode can generate high-quality electron beams and achieve efficient electron beam introduction. Provide technical support for Ka-band coaxial multi-reported relativistic klystron amplifiers.
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:
Energy spectrum measurement for pulsed hard X-ray from 15 keV to 600 keV
Su Zhaofeng, Lai Dingguo, Qiu Mengtong, Ren Shuqing, Xu Qifu, Yang Shi
Corrected proofs  doi: 10.11884/HPLPB202032.190354
[Abstract](80) [PDF 701KB](3)
Abstract:
This paper introduces the basic principle and design ideas of absorptive method for X-ray energy spectrum measurement. Si-PIN detectors array and Cu, Al attenuation materials were used to design the energy spectrometer combining theoretical calculation and experimental study. The collimating and anti-interference system was developed to obtain higher signal-to-noise ratio waveforms. The influence of scattering was researched. The different attenuation waveforms of pulsed hard X-ray at ShanguangⅡ accelerator were measured experimentally in the vacuum environment. The energy spectrum was calculated. The maximum energy of X-ray was about 600 keV, and the average energy was about 89.1 keV, which agreed with the calculation results.
Anisotropic stacked epoxy composites with excellent thermal properties
Li Jiapeng, Xia Lansong, Zhang Ping, Liu Dong
Corrected proofs  doi: 10.11884/hplpb201931.190342
[Abstract](161) [PDF 742KB](3)
Abstract:
With the rapid development of high-power lasers and electronic technology, higher requirements have been proposed for the structure and material of the heat sink device. Based on the principle of conduction-insulation heat, alternating stack epoxy resin composites with excellent thermal protection were prepared, the hexagonal boron nitride (h-BN: 5%, 15%, 25%) and expanded vermiculite (E-ver: 1%) are used as fillers for heat dissipation layer and thermal insulation layer, respectively. The thermal protection performance experiment was completed. The result shows that the temperature of the top center is 13-16 °C lower than that of the traditional materials, and the thermal delay time is greatly improved. An increase in the h-BN content causes an increase in the thermal protection properties of the composites. The thermal mechanism of the anisotropic stacked composites was explained.
Inversion algorithm of vertical visibility based on lidar and its error evaluation
Song Hairun, Wang Xiaolei, Li Hao
Corrected proofs  doi: 10.11884/HPLPB202032.190250
[Abstract](237) [PDF 1451KB](3)
Abstract:
To solve the problem that the non-uniform distribution of extinction coefficients in the vertical direction of the atmosphere makes it difficult to directly measure the vertical visibility by traditional methods, this paper presents a method for calculating the vertical visibility based on lidar detection. Firstly, according to the basic principle of atmospheric radiation transmission and radiation transfer equation, it deduces the calculation formula of vertical visibility, which solves the problem that there is no specific formula for calculating vertical visibility. Secondly, it inverts the extinction coefficient distribution in the vertical direction of the atmosphere by using the lidar equation and Klett algorithm. On this basis, it proposes an iterative algorithm for vertical visibility. Finally, it uses the gray model GM(1,1) and batch statistics algorithm to evaluate the backscattering coefficient obtained by laser radar inversion, and gives the error confidence interval (0.760±0.339)×10−4(srad·km)−1. The results show that the method is a particularly effective one for calculating vertical visibility, which meets the basic requirements of detection, with small error and high precision.
High-precision Runge-Kutta method for transmission line equation
Wang Xutong, Zhou Hui, Ma Liang, Cheng Yinhui, Li Jinxi, Liu Yifei, Zhao Mo, Guo Jinghai, Wang Wenbing
Corrected proofs  doi: 10.11884/HPLPB202032.190402
[Abstract](130) [PDF 1755KB](3)
Abstract:
This paper presents a high-precision Runge-Kutta (RK) method for solving transmission line equations. This method adopts high-order Taylor expansion in space, which improves the approximation accuracy of spatial differentiation. Compared with the traditional finite element time-domain method, when the number of samples per wavelength is the same, RK method has higher precision. At the same time, according to the Taylor model, researchers use RK method to solve transmission line equation in the external field excitation. The correctness and high precision of the RK method are verified by numerical examples of our study.
Design of portable resonant voltage doubling capacitor charging power supply
Zhang Yuanyi, Ling Zhibin, Li Xuguang
Corrected proofs  doi: 10.11884/HPLPB202032.190400
[Abstract](169) [PDF 891KB](2)
Abstract:
This paper presents the design and verification of a portable resonant voltage doubling capacitor charging power supply with an input voltage of 24 V and an output voltage of 3 kV. According to the characteristic of high voltage ratio, this power supply adopts a topology structure combining the series resonant topology and the voltage doubling rectifier, which avoids the adverse effects of excessive number of turns on the secondary side of the high frequency transformer and excessive distributed parameters. The core components such as high frequency transformer, resonant capacitor and switching device were designed and debugged. The power supply was used to conduct the capacitor charging experiment, and the test results have verified the correctness of the design.
Two-phase streamer characteristics in transformer oil under nanosecond impulses voltages
Wang Qi, Wang Meng, Wang Jue, Yan Ping
Corrected proofs  doi: 10.11884/HPLPB202032.190380
[Abstract](297) [PDF 2125KB](0)
Abstract:
To reveal the influence of the formation and development of gas-phase streamer channel on liquid discharge between pin-plane electrodes, a numerical model of the transformer-oil discharge in the pin-plane electrode system is built based on the continuity equations of free charge carriers, which are coupled with the Poisson’s equation. The gas-phase processes during the streamer development process is also taken into consideration, including impact ionization and the increase in the mobility of free charge carriers in the gas-phase relative to the liquid-phase in the streamer channel. The Heaviside function is used to switch the simulation model between gas-phase and liquid-phase. The initial and propagation progress of streamer discharge under nano-second pulse voltage is simulated using the model. Simulating results show that the electric field at the streamer body is significantly reduced and the electric field at the head of the streamer is further enhanced with the addition of such low density gas-phase region. The propagation speed of the streamer in two-phase model is also faster than that of the ordinary liquid-phase model.
Analysis on nonlinear response of RF filter under ultra wide band pulse environment
Lu Xicheng, Qiu Yang, Wu Jing, Tian Jin, Yang Zhiqiang
Corrected proofs  doi: 10.11884/HPLPB202032.190355
[Abstract](289) [PDF 764KB](5)
Abstract:
The experiments reveal, for the RF filter, the out-off-band transfer property under ultra wide band (UWB) pulses is essentially in agreement with that of continous wave (CW). However, for some frequencies in the in-band of the filter, the transfer function of UWB is much larger than 1. Moreover, the oscillating property is found in the time domain response of the filter. Therefore, based on the nonlinear passive intermodulation (PIM) and the Q-value, the response mechanisms of the filter are studied. The PIM of the filter shows nonlinear effects under the two different field strengths, which results in the limited universality of measurement results. Furthermore, the signal through the filter is predicted by making use of the two measured transfer functions. The predicting results under CW pulse are smaller than the measured ones in energy and peak power. In a word the response mechanisms of the filter under UWB pulse does differ from the that under CW pulse, i. e., the measured results of CW can’t be applied for the UWB effect analysis and evaluation.
Lifetime characteristic of three-electrode field-distortion gas switch of fast linear transformer driver
Li Ying, Jin Jianwei, Chen Li, Sun Fengju, Li Xingwen, Wang Zhiguo, Jiang Xiaofeng, Wu Jian, Li Penghui
Corrected proofs  doi: 10.11884/HPLPB202032.190339
[Abstract](258) [PDF 1180KB](4)
Abstract:
Three-electrode field-distortion gas switch is a crucial element of modular fast linear transformer driver (FLTD). Electrode erosion affects the trigger jitter during the lifetime of the switch, which in turn can affect the output characteristics of FLTD. Therefore, studying the impact of electrode erosion on the trigger jitter of the switch is of great significance to optimize the switch structure and predict the switch life. This paper studies the erosion characteristic of intermediate electrode of three-electrode switch, and the electrode materials are stainless steel and brass. The key factors affecting the lifetime of switch are obtained by considering the changing rules of trigger and erosion characteristics, which provides theoretical support for the optimization of the performance of the three-electrode switch. The results show that the erosion area and surface roughness of stainless steel and brass electrodes increase with discharge times. The brass electrode is ablated more seriously and the stainless steel electrode has higher surface roughness. With the increase of discharge times, the breakdown point moves to the electrode edge area, which affects the insulation performance of the switch.
Study on temperature rise of electromagnetic coil launcher
Xiong Min, Zhang Yadong, Gong Yujia, Zhang Hu
Corrected proofs  doi: 10.11884/HPLPB202032.190300
[Abstract](227) [PDF 1235KB](1)
Abstract:
Synchronous induction coil launcher mainly uses pulse current to supply power directly to the coil. The temperature rise of armature and coil will occur in the actual working process, and it is a major factor restricting the development of coil launcher to miniaturization and high speed. In this paper, the temperature rise model of electromagnetic coil is established. For single trigger, Comsol and self-programmed Coilgun are used to calculate, and the corresponding test platform is built to verify the temperature rise. The Comsol method with direct coupling is the most accurate method, and the change of material parameters with temperature can also be considered. The simulation results show that the temperature rise of armature is about 4.2 ℃ and the maximum temperature rise of coil is 7.7 ℃. Because of the limitation of measurement delay and sampling frequency of thermocouple temperature sensor, the armature temperature test curve can not measure the maximum temperature point in the simulation curve, it can record the temperature change curve in the whole test process. The change of temperature and the final stable temperature are basically consistent with that of the simulation. The maximum error is 6.1%, which shows the accuracy of the simulation. This study lays a foundation for subsequent multi-stage coil continuous launching.
Propagation characteristics of terahertz wave in plasma sheath around air vehicle
Geng Xingning, Xu Degang, Li Jining, Chen Kai, Zhong Kai, Yao Jianquan
Corrected proofs  doi: 10.11884/HPLPB202032.190291
[Abstract](319) [PDF 1132KB](15)
Abstract:
In this paper, the plasma electron density and collision frequency are calculated based on the flow field simulation of RAM C-III air vehicle, and an inhomogeneous plasma model is established according to the calculation results. The effects of plasma density, plasma thickness, plasma collision frequency and external magnetic field on the propagation characteristics of terahertz wave in plasma are analyzed using scattering matrix method. The results show that the propagation loss increases with plasma electron density and plasma thickness, while the transmittance decreases first and then increases with the increasing of collision frequency. When an external magnetic field is applied, the propagation characteristics of the left-handed polarized terahertz wave will be improved, while for the right-handed polarized terahertz wave, the application of magnetic field induces an absorption peak, which shifts to high frequency range with the increasing of magnetic induction intensity. This work may make a contribution to solving the problem of communication blackout.
Analysis and research on new integrated motor-driving and charging topology
Zhang Yaowen, Zhang Zhengquan, Liu Qingxiang, Ou Weili
Corrected proofs  doi: 10.11884/HPLPB202032.190283
[Abstract](128) [PDF 924KB](0)
Abstract:
This paper proposes a novel motor-driving charging integrated topology with high-frequency AC link (HF AC-link), soft-switching operation and high-frequency (HF) galvanic isolation, which can apply to the two modes of motor driving control and charging. The topology belongs to a new class of resonant AC-link topology, and its link is composed of a series ac inductor/capacitor(LC) pair.When the topology is working in the forward direction, the driving motor is in the motor driving control state, and the battery is being charged in the backward working period. In this paper, the principle of operation of the two working modes of the new topology is introduced in detail. The effective control strategy is used and the simulation model is built by MATLAB/Simulink software. The integrated topology and control strategy are verified. The simulation results show that the topology works. The charging mode can meet the different voltage requirements of the whole charging phase of the battery; working in the motor driving mode, the stator current exhibits a good three-phase sinusoidal shape in both the acceleration process and the normal working process, and the rotation speed can reach a given value, thereby proving the feasibility of this topology and control strategy.
Nitrogen doping experiment of 1.3 GHz superconducting cavity
Dong Chao, Sha Peng, Liu Baiqi, Li Zhongquan, Yang Jisen, Wang Honglei
Corrected proofs  doi: 10.11884/HPLPB202032.190141
[Abstract](203) [PDF 712KB](9)
Abstract:
In order to greatly improve the quality factor (Q) of a Nb superconducting cavity and reduce its power loss, we performed high-temperature nitrogen doping (N-doping) on the superconducting cavity, which is the most widely used method in the world. Based on the needs of large-scale accelerators at home and abroad, the Institute of High Energy Physics, Chinese Academy of Sciences, carried out researches on 1.3 GHz 1-cell superconducting cavities, including standard post-processing and N-doping. After data analysis and comparison, it can be found that the Q values of two 1.3 GHz 1-cell fine-grain superconducting cavities have been significantly improved. At the same time, the abnormal behavior of Q value depending on acceleration gradient (Eacc) was observed in low-temperature vertical test, which is called the "anti-Q-slope" phenomenon.
The preliminary study of laser-triggered pseudospark switch
Zhou Liang, Zhang Ming, Sun Chengge
Corrected proofs  doi: 10.11884/HPLPB202032.190094
[Abstract](206) [PDF 1012KB](2)
Abstract:
Laser-triggered pseudospark switches, also called back-lighted thyratrons (BLTs), are low pressure, high voltage, high current glow-mode switches The feasibility of BLTs is verified. The laser beams with wavelengths of 266 nm and 532 nm were used in the test. In the non-focused mode, the minimum trigger energy for 266 nm laser is 15 mJ, the anode ignition delay time is about 340 ns, and the time jitter is about 40 ns. The minimum trigger energy for 532 nm laser is 83 mJ, the anode ignition delay time is about 420 ns, and the time jitter is about 60 ns. In the focused mode, the minimum trigger energy for 266 nm laser is 4 mJ, when the laser trigger energy is 8 mJ, the anode delay time is 190 ns, the jitter is less than 1 ns. The minimum trigger energy for 532 nm laser is 6 mJ, when the laser trigger energy is 8 mJ, the anode delay time is than 240 ns, the jitter is less than 1 ns. The methods to further reduce the energy of the laser trigger will be studied in the future.
 Cover and Contents
 Cover and Contents No 1, Vol 32, 2020
2020, 32: 1-2.  
[Abstract](14) [PDF 3111KB](7)
Foreword
Introduction for Special Issue
2020, 32: 011001.   doi: 10.11884/HPLPB202032.200009
[Abstract](46) [PDF 201KB](5)
Academician Interview
2020, 32: 011002.   doi: 10.11884/HPLPB202032.0467
[Abstract](44) [PDF 1532KB](5)
Special Overview
Progress on laser precise control for high power laser facility
Zheng Wanguo, Li Ping, Zhang Rui, Zhang Ying, Deng Xuewei, Xu Dangpeng, Huang Xiaoxia, Wang Fang, Zhao Junpu, Han Wei
2020, 32: 011003.   doi: 10.11884/HPLPB202032.190469
[Abstract](183) [PDF 3414KB](13)
Abstract:
Beam precise control is the basic requirement of Interial Confinement Fusion (ICF) research for laser facility. Its technical characteristics determine that it is a system project for laser facility. This paper introduces the important progress made by the Laser Fusion Research Center of Chinese Academy of Engineering Physics in the control of focal-plane irradiance, pulse precision shaping, beam near-field intensity and novel beam exploration in recent years.
Research Letter
kJ low-coherence broadband Nd:glass laser driver facility
Gao Yanqi, Ji Lailin, Cui Yong, Rao Daxing, Zhao Xiaohui, Feng Wei, Xia Lan, Liu Dong, Wang Tao, Shi Haitao, Li Fujian, Liu Jia, Du Pengyuan, Li Xiaoli, Liu Jiani, Zhang Tianxiong, Shan Chong, Ma Weixin, Sui Zhan, Fu Sizu
2020, 32: 011004.   doi: 10.11884/HPLPB202032.190427
[Abstract](89) [PDF 494KB](4)
Abstract:
The instability of the laser plasma interaction is expected to be greatly suppressed by reducing the coherence of the output pulse of the high-power laser facilities. Using the low-coherence light as the seed source and the Nd:glass as the amplifying medium, the first kJ low-coherence broadband laser was developed delivering 960 J pulses centered at 1 056 nm with a bandwidth of 13 nm. The output pulse has a coherence time of 300 fs and a pulse duration adjustable from 3 ns to 10 ns. The spectrum of laser pulse is smooth with no longitudinal mode structure. And the spectral phase is randomly distributed, which can realize uncorrelated tunable output of pulse waveform and spectral shape. This facility successfully demonstrates the unit and system integration technologies of the broadband low-coherence laser driver and provides a new experimental platform for laser plasma interaction and high energy density physics research.
All-fiber narrow linewidth fiber laser achieved 3 kW near diffraction limited output at 1 030 nm
Chu Qiuhui, Shu Qiang, Lin Honghuan, Tao Rumao, Yan Donglin, Wang Jianjun, Jing Feng
2020, 32: 011005.   doi: 10.11884/HPLPB202032.190463
[Abstract](73) [PDF 433KB](10)
Abstract:
In this paper, we demonstrate an all-fiber high-power Yb-doped 1 030 nm fiber laser based on master oscillator power amplifier structure. The record output power at 1 030 nm up to 3 004 W was achieved, along with a slope efficiency of 69.27%, which is the highest output power for 1030 nm near diffraction limited beam quality fiber laser. The beam quality factor is Mx2=1.169, My2=1.174, and full width at half maximum is 0.18 nm at maximum power level. The amplified spontaneous emission (ASE) suppression ratio reaches up to 37 dB.
Output of 3.08 kW narrow linewidth linearly polarized all-fiber laser based on a simple MOPA structure
Wang Yanshan, Wang Jue, Chang Zhe, Peng Wanjing, Sun Yinhong, Ma Yi, Gao Qingsong, Zhang Kai, Tang Chun
2020, 32: 011006.   doi: 10.11884/HPLPB202032.200004
[Abstract](32) [PDF 606KB](5)
Abstract:
We demonstrated a narrow linewidth linearly polarized all-fiber laser operating at maximum output power of 3.08 kW with a 3 dB linewidth of 0.2 nm based on a simple master oscillator power amplifier (MOPA) structure. The polarization extinction ratio (PER) is about 94% and the M 2 is about 1.4 along the whole power scaling process. This is the first demonstration of a 3 kW linearly polarized all-fiber laser output. Compared with the narrow linewidth fiber amplifier based on phase modulation, this system can achieve a nearly same linewidth. Meanwhile, it has the characteristics of high stimulated Brillouin scattering (SBS) threshold, simple structure, and low cost, etc.
Expert Overview
Retrospect and prospect on 60-year development of high energy laser
Xu Xiaojun
2020, 32: 011007.   doi: 10.11884/HPLPB202032.0480
[Abstract](165) [PDF 448KB](15)
Abstract:
Ordered motion of quantum particles produces laser, while disordered motion produces heat, this conflict overwhelms development of high energy laser since its beginning, and the guide-line of its history is just a battle with waste heat. Reviewing the 60-year development of high energy laser and examining the science behind it, we divided its history into pre and past 30 years, which separately solved the problem of capability and was just solving the problem of easy-to-use ability. Sticking with heat generation and dissipation, we discussed inner links between power, beam quality and efficiency of high energy laser, reviewed the rise and fall of different kinds of lasers, and predicted future development of high energy laser.
Plasma optics technologies: State of the art and future perspective
Li Ping, Zhang Jun, Wei Xiaofeng
2020, 32: 011008.   doi: 10.11884/hplpb202032.190466
[Abstract](135) [PDF 1849KB](14)
Abstract:
Plasma optics is an important way for the development of high power laser technology because plasma medium has high energy storage density, no laser-induced damage threshold and rich optical properties. The research status of plasma optics in recent years is introduced, and the development trend of plasma optics in the future is discussed.
Progress of the research on Yb3+-doped femtosecond laser crystals
Sun Shijia, Lou Fei, Lin Zhoubin, Zhong Degao, Teng Bing
2020, 32: 011009.   doi: 10.11884/HPLPB202032.190451
[Abstract](139) [PDF 2023KB](7)
Abstract:
As widely used in military, medicine, communication, processing and other fields, femtosecond laser has become a research hotspot of the whole laser technology in the 21st century. The pump source used by laser diodes (LDS) has become a new development trend of all-solid-state femtosecond lasers owe to the rapid development of LDs. Yb3+-doped laser crystal materials gradually become important gain media for LD pumping and generate 1.0 μm femtosecond laser due to their unique energy level structures, broad absorption and emission spectra. In this paper, the research progress of Yb3+-doped femtosecond laser crystals is summarized in detail, the main problems are analyzed, and two directions for the development of femtosecond laser crystals in the future are proposed: high efficiency and low power femtosecond laser, high power and high energy femtosecond laser. The crystal growth, spectra properties, continuous and femtosecond laser performances of the Yb3+:Sr3Y2(BO3)4 crystal were studied in detail. And the Yb3+:Sr3Y2(BO3)4 femtosecond laser with the center wavelength of 1060 nm, pulse width of 116 fs, average output power of 1.08 W and optical conversion efficiency of 33.1% were successfully generated. The experimental results indicate that Yb3+:Sr3Y2(BO3)4 and its corresponding system crystals are excellent femtosecond laser materials with high optical conversion efficiency.
Research Article
Thermal management of water-cooled 10 Hz Yb:YAG laser amplifier
JiangXinying, WangZhenguo, ZhengJiangang, YanXiongwei, LiMin, ZhangXiongjun, SuJingqin, ZhuQihua, ZhengWanguo
2020, 32: 011010.   doi: 10.11884/HPLPB202032.190456
[Abstract](140) [PDF 1530KB](5)
Abstract:
To control the thermal wavefront distortion of repetition frequency laser, we′ve developed a water-cooled active-mirror laser amplifier, which was uniformly cooled from the rear of crystal disk. The numerical anslysis and experimental study on the characterstics of the amplifier’s thermal distortion were carried out. It was found that the thermal distorition devoted a significiant modulation to the near field of the laser when the average pump power density was as high as 200 W/cm2 with the operation frequency of 10 Hz. Near-field modulation would bring a risk to damage the amplifier. To eliminate the modulation of thermal distortion in the near field, two approaches were taken. Firstly, the pump intensity distribution was homogenized, then the edge thermal balance control was carried out. The near field modulation from thermal wavefront distortion was eliminated by these means, a four-pass amplifier with water-cooled laser heads ran well at 10 Hz. The focal spot of output laser was smaller than 5 diffraction limits without any compensation.
Laser-induced damage in fused silica under multi-wavelength simultaneous laser irradiation
Qiu Rong, Jiang Yong, Guo Decheng, Shi Jinfang, Li Cui, Ye Cheng, Zhou Qiang, Han Wei, Huang Jin
2020, 32: 011011.   doi: 10.11884/HPLPB202032.190479
[Abstract](97) [PDF 779KB](12)
Abstract:
The initial damage and damage growth of fused silica optical elements irradiated by 3ω alone, by two wavelengths (3ω+2ω and 3ω+1ω) at the same time were studied. When the energy density of 3ω is near its threshold, the influence of 2ω and 1ω of low energy density on the initial damage and damage growth is studied. The energy coupling mechanism between wavelengths is analyzed. The results show that: When the energy density of 2ω or 1ω is much lower than its threshold, irradiating at the same time, their effects on the initial damage probability and damage growth threshold can be ignored. But the initial damage degree and damage growth coefficient will increase. The measurement of shock wave velocity based on femtosecond dual pulse imaging shows that, when 3ω and 1ω irradiate at the same time, the energy coupling effect between wavelengths will promote the deposition efficiency of laser energy to materials.
Conjugate rotation smoothing scheme for laser quad based on dual-frequency laser and spiral phase plate
Zhong Zheqiang, Zhang Bin
2020, 32: 011012.   doi: 10.11884/HPLPB202032.190454
[Abstract](79) [PDF 1116KB](5)
Abstract:
Conjugate rotation smoothing scheme for laser quad based on dual-frequency laser and spiral phase plate was proposed. The dual-frequency laser provides frequency shift among the beamlets, the spiral phase plates with same helical charge but opposite sign transform the beamlets into Laguerre-Gaussian beams, and the polarization control is applied to make these beamlets coherently superposed on the target plane. On this basis, the conjugate continuous phase plates are adopted to enable the beamlets with different central wavelength and orthogonal polarization form focal spots with rapid rotation. Moreover, the spatiotemporal focal spot of the laser quad looks like conjugate spin light because of the frequency beats. It is indicated that, the scheme enables the fine-scale speckles within the focal spot rotate in a period of a few picoseconds, and even exhibit different intensities and wavelengths at different time and different positions. Hence, the novel scheme can effectively smooth the irradiation uniformity of the laser quad and even has the potential to mitigate laser plasma interactions.
NbSe2 nanoparticles mode-locked 2 μm thulium fiber laser
Liu Xinxing, Tian Zhen, Tang Yulong
2020, 32: 011013.   doi: 10.11884/HPLPB202032.190458
[Abstract](30) [PDF 925KB](3)
Abstract:
High-repetition-rate laser pulses with large pulse energies have great application potential in various areas including telecommunications, sensing, material processing, etc. Here, we report the linear and nonlinear optical properties of solution-based transition-metal dichalcogenide NbSe2 nanoparticles, and at the same time its application to mode-locked 2 μm fiber laser. The linear absorption of the NbSe2 nanoparticles covers the near-infrared to the near mid-infrared regions, and decreases with increasing wavelength, showing a broadband operation potential. Nonlinear absorption measurement of the NbSe2 nanoparticle gives a modulation depth of 6.5% and saturable intensity of 19 MW·cm−2 at the wavelength of about 2 μm. The the NbSe2 nanoparticles were transferred onto a gold mirror to fabricate a saturable absorber, with which a mode-locked thulium fiber laser was constructed and harmonic mode-locking was achieved. The mode-locked laser provides pulse energy of 3.36 nJ, pulse duration of 1.48 ns and repetition rate of 50.66 MHz. The laser wavelength is centered at 1 910.8 nm with a spectral bandwidth of 5.8 nm. The realization of dissipative-soliton mode-locking in the 2 μm fiber laser with NbSe2 nanoparticles proves that NbSe2 nanoparticles are good modulators for pulse generation in the 2 μm spectral region, and the integratable solution based nanoparticles hvae the potential of being new broadband nonlinear light modulators.
Amplification and beam combination of ultra-short KrF laser pulse
Wang Zhao, Zhang Ji, Li Jing, Gao Zhixing, Hu Fengming, Tian Baoxian, Ban Xiaona
2020, 32: 011014.   doi: 10.11884/HPLPB202032.190460
[Abstract](25) [PDF 646KB](1)
Abstract:
To make full use of the long pump time of krypton fluoride excimer laser amplifiers and to increase the amplification efficiency, we carried out experimental research on multi-pulse amplification and beam combination of ultra-short UV pulses. The effect of delay time on pulse energy was studied using dual pulse amplification. Based on the above relationship, optimal delay time was confirmed, the increase of total energy and the reduction of amplified spontaneous emission (ASE) were both archived. Amplification of four ultraviolet pulses was achieved, and the energy was nearly four times that of the single pulse amplification. We also explored beam combining technology of ultraviolet ultra-short laser pulses, and combined two sub-picosecond pulses accurately.
All optical control of long period fiber grating based on graphene oxide
Ma Yukuan, Chen Xiaoxu, Zhou Shouhuan, Feng Guoying, Zhou Hao, Liu Pengyu
2020, 32: 011015.   doi: 10.11884/HPLPB202032.190468
[Abstract](30) [PDF 1162KB](1)
Abstract:
A kind of all-optical control method based on the deposition of graphene oxide dispersion in long period fiber grating is proposed and experimentally validated. Pumped by an external vertical light, graphene oxide generates heat and changes the phase difference of the cladding mode of long-period fiber grating. Due to the effect of thermal expansion, the grating period of the part covered by graphene oxide is changed, which makes the resonance spectrum shift. The maximum modulation depth can reach 10.6 dB, and the maximum resonance spectrum can be red-shifted by 12.8 nm. It is found that the number of times to deposit graphene oxide dispersion with the same concentration influences the experimental results. By depositing graphene oxide dispersion at the same position of the same grating once and three times respectively, it is found that the more uniform graphene oxide film can be obtained on the surface of optical fiber by three times of deposition, which enhances the interaction between light and graphene oxide, and has higher modulation efficiency and tuning efficiency. Finally, the time response test is carried out, and the response speed of the long period fiber grating after three times of deposition can reach 0.61 ms. It is found that the graphene oxide dispersion can be deposited more evenly on the surface of the optical fiber, thus obtaining greater thermal conductivity.
Phase jump in multiphoton resonant harmonic emission driven by strong frequency-comb fields
Chen Chunjuan, Zhao Yuanyuan, Zhao Di, Jiang Chenwei, Fang Aiping, Gao Shaoyan, Li Fuli
2020, 32: 011016.   doi: 10.11884/HPLPB202032.190453
[Abstract](34) [PDF 759KB](3)
Abstract:
This paper presents a theoretical investigation of the phase jump of multiphoton harmonic emission driven by two frequency-comb fields. The Floquet theorem is employed to provide a nonperturbative and exact treatment of the interaction between a quantum system and frequency-comb fields. Multiple multiphoton-transition paths for the harmonic emission are coherently summed. The phase information about paths can be extracted via the Fourier Transform analysis of the harmonic signals which oscillate as a function of the relative phase between two frequency-comb fields. Phase jumps were observed when harmonic emission was sweeping across the resonance by varying the frequency or intensity of two frequency-comb fields, which allows us to observe the Stark-shifted transition energy of resonant frequency of quantum system driven by strong laser fields.
Dissipative soliton erbium-doped fiber laser based on hybrid mode-locking
Feng Xingli, Zhao Lei, Zhang Haoyu, Deng Guoliang, Wang Sha, Feng Guoying, Zhou Shouhuan, Ma Yukuan
2020, 32: 011017.   doi: 10.11884/HPLPB202032.190481
[Abstract](35) [PDF 1336KB](2)
Abstract:
The dissipative solitons with high stability and wide spectrum are obtained from a simple and all fiber hybrid passively mode-locked erbium-doped fiber laser. The laser combines two mode-locked mechanisms of saturable absorber and nonlinear polarization rotation, and operates in the normal dispersion region. Through dispersion management, the laser can generate a series of soliton pulses with spectral width of 39.1 nm and pulse duration of 178 fs. The wavelength of laser operation is 1.55 μm, the repetition frequency is about 34.3 MHz, and single pulse energy is evaluated to be 0.33 nJ. At the same time, the laser also possesses the slope efficiency of about 15.5%; at room temperature, the laser can realize self-starting mode locking, and the operation time in the stable state of a single pulse output is more than 15 h.
Interaction between laser-driven high-velocity metal granule and gas
Han Xue, Zhang Li, Zhang Yongqiang, Wu Jichuan, Tan Fuli
2020, 32: 011018.   doi: 10.11884/HPLPB202032.190265
[Abstract](218) [PDF 1151KB](7)
Abstract:
We apply laser-driven launching technique to the interaction between high-velocity metal granule and gas to investigate high speed gas-solid two-phase flow transport. Optimization of target design and adjustment of laser parameters were used to control the laser-driven process. Diagnostic tools with high resolving power of space and time as well as higt accuracy were set up to capture the high-velocity granule. The unsteady flow field of the granule was simulated by solving the the 3-D Reynolds averaged Navier-Stokes equations and six degree of freedom ballistic equation. With the implicit Gauss-Seidel scheme, the code was advanced in time. The results indicated that the laser-driven launching technique was effective and the shadow photographs of high-velocity granule were taken successfully. The aerodynamic drag of high-velocity granule was computed with numerical simulation.
Improvement of beam quality by pump homogenization of Innoslab laser amplifier
He Tao, Chen Xiaoming, Lu Yanhua, Zhang Bin, Xu Liu, Ye Xianlin, Xu Xiafei
2020, 32: 011019.   doi: 10.11884/HPLPB202032.190277
[Abstract](116) [PDF 1164KB](3)
Abstract:
The effect of pump homogenization on the beam quality of the output laser is studied for a compact partially end-pumped hybrid-cavity slab laser amplifier, i.e. Innoslab laser amplifier. Using ZEMAX simulation software, two pump coupling modes, direct imaging and homogenization with waveguide were designed, and their effects on the uniformity of light intensity distribution in the slow axis (crystal width) direction of laser diode arrays were compared. It is found that the pump uniformity is significantly improved after the waveguide is homogenized and the influence of the laser diode array luminescence dead pixels on the pump imaging is weakened. Furthermore, the effect of pumping homogenization on the performance of Innoslab laser amplifier is verified by experiments: the uniformity of slow-axis pumping increases from 90.6% to 95.4% after homogenization with waveguide, and the quality of output laser beam M2 increases from 2.41 to 1.55 after three-pass amplification, and the self-oscillation in the cavity is effectively suppressed.
Influence of structural surface roughness on self-excited oscillation of main amplification system of high power laser device
Liao Yuzhen, Wang Deen, Deng Xuewei, Zhang Xin, Yang Ying, Guo Yuyuan, Zheng Shengheng, Yuan Qiang, Hu Dongxia
2020, 32: 011020.   doi: 10.11884/HPLPB202032.190274
[Abstract](184) [PDF 1298KB](2)
Abstract:
For high-power laser devices using off-axis multi-pass amplification technology, the technology to suppress self-oscillation is of great research value. It is found in engineering practice that the surface of the structure near the aperture of the main amplification system is relatively bright, thus when the amplifier is working, with sufficient gain, a resonant cavity is formed between the bright structural surface and the cavity mirror to generate self-oscillation and ablation. In this paper, this problem of the device is studied by using Monte Carlo method to simulate the surface of the structure. According to the principle of geometric optics, the reflection model of the laser beam on the surface of the structure is derived. The surface of the main amplification system is simulated using this model, and the parameters of the optical path are used to calculate the relationship between surface roughness and residual reflected light reflected into the amplifier. The surface treatment process is applied to our project. By increasing the surface roughness of the structure, the resonant cavity loss is greater than the gain, which provides a basis for suppressing the self-oscillation of the main amplification system of high-power laser devices.
Random vibration response analysis of Shenguang laser facility component based on PANDA platform
Wang Keying, Fan Xuanhua, Chen Xueqian, Niu Hongpan
2020, 32: 011021.   doi: 10.11884/HPLPB202032.190269
[Abstract](225) [PDF 1659KB](4)
Abstract:
Reliability design requirements for large and complex equipment pose new challenges to numerical simulation of structural dynamics. In this paper, based on self-developed parallel computing platform PANDA, the modal superposition method is used to calculate the random vibration response under multi-point foundation excitation. The algorithm design and parallel implementation are carried out, and the corresponding solving module is constructed. Taking the six-degree-of-freedom platform structure in the target positioning prototype of Shenguang facility as a numerical example, the modal and random vibration responses of the structure under ground fluctuating load are analyzed with our self-developed progress modules in PANDA platform. The analysis results are compared with the test results and commercial software analysis results. In terms of mode frequency, mode shape and displacement response, the results are consistent, which verifies the correctness of the relevant software and proves the feasibility of PANDA platform in actual engineering structural analysis. The correlative studies have important significance on solving dynamic analysis problems of complex equipments with autonomic software and breaking limitations of commercial finite element software.
Broadband second harmonic generation of spatially chirped pulses
Tao Yudong, Hu Dongxia, Han Wei
2020, 32: 011022.   doi: 10.11884/HPLPB202032.190146
[Abstract](741) [PDF 775KB](4)
Abstract:
Efficient broadband harmonic conversion has important application value in high power laser. However, it is difficult to achieve broad bandwidth and high efficiency at the same time in the traditional second harmonic generation (SHG). This paper proposes a novel broadband SHG scheme, which uses the space-time coupling effect to transform the temporally chirped pulse into a spatially chirped one, and then several spliced crystals are used to achieve efficient broadband frequency conversion. Simulation results show that for the spliced KDP crystal, the conversion efficiency of the fundamental harmonic reaches about 60%, for pulse bandwidth of 30 nm and central wavelength of 1 053 nm. Moreover, the frequency doubled light is still linear and broadband, and can be compressed as the fundamental pulse.