本文通过分析γ射线二极管的物理过程,对二极管的阴阳极材料和结构进行了改进,并在强光一号装置上进行了实验验证.实验结果表明,通过采用深槽结构的黄铜阴极和多层阳极靶可显著降低强光一号装置二极管的阴极烧蚀、溅射沉积污染及阳极的热-力学损伤.改进后的阴极至少可重复使用3发次,阳极至少可重复使用4发次.实验结果为建设中的大面积脉冲γ射线辐射装置二极管的研制和实验效率提升提供了新技术途径.

介绍了利用串级二极管产生高强度脉冲硬X射线的方法及其辐射场参数.以"闪光二号"加速器为平台,通过适应性改造,产生快前沿电压脉冲;研制了两级阻抗1 Ω串级二极管,通过串联分压降低二极管端电压、各级二极管电子束独立打靶在空间叠加形成高强度均匀辐射场.解决了悬浮电极绝缘支撑、二极管阴极均匀发射等技术难题,实现了串级二极管的稳定工作.在总电压约700 kV、电流约310 kA条件下,X射线平均能量87 keV,500 cm2上的平均能注量36 mJ/cm2,剂量均匀性(最大值比最小值)达到2:1.

Electron beam pinching is a common physical phenomenon in the working process of high-current electron beam diodes. The radial collapse velocity (Va) of the beam is an important index to determine the beam pinching and the working characteristics of the diode. The current research methods are based on optical diagnosis and theoretical estimation formulas for a specific diode. The radial collapse velocity of Qiangguang-I accelerator’s tight-pinched short γ diode can be obtained by the following three methods in this paper: 1) a theoretical formula, which is used to calculate the radial collapse velocity on the basis of the existing research results, and can very quickly determine the pinching situation because in this case this formula just needs a diode pinching current; 2) the method of calculating Va, which is established based on particle-in-cell simulation. The simulation model includes the anode ion current, thus can simulate the pinching of electron beam more precisely; 3) a method of calculating Va, which is given by measuring the pinch center offset and the γ-ray PIN waveform, because the Qiangguang-I γ diode is inconvenient for optical diagnosis. The radial collapse velocities obtained by the above three methods are 8.43, 8.70 and 7.89 cm2/ns respectively, and the relative difference among the three methods is < 10%. The third method obtains a slightly smaller value because the ion current assumed in the theory and simulation is H+. The ion current composition in the actual diode is complex, the diffusion speed is slower, then the radial collapse velocity is smaller. Compared with the typical Va value (2–4 cm2/ns) of the Gamble II accelerator diode given by the Blaugrund team, the Va value of the short γ diode of the Qiangguang-I accelerator is nearly doubled. The diode on Qiangguang-I, which works after a plasma opening switch (POS), has a very short rising time (less than 10 ns), and pinches quickly. In contrast, the rising time of the Gamble II accelerator diode is about 40 ns, which is different from the working status of the Qiangguang-I diode. This paper provides a new way to study the radial collapse velocity of high-current diodes.

介绍了基于吸收法的脉冲硬X射线能谱测量的基本原理及设计思路,完成了探测器及吸收片的选型,设计了射线准直系统,研究了散射对测量的影响,以12路PIN探测器阵列及铜、铝吸收片为测量核心部件研制了脉冲硬X射线能谱测量系统.实验测量了真空环境下"闪光二号"加速器串级二极管产生的脉冲硬X射线强度,获得了不同衰减程度的实验波形,通过解谱获得了脉冲硬X射线的能谱,光子最高能量约600 keV,平均能量约89.1 keV,与理论计算的结果比较符合.

Pulsed high-energy fluence X-ray source is based on the "Flash II" accelerator. It can be used to carry out effect vulnerability and sensitivity test of unit level system generated electromagnetic pulse (SGEMP). The energy fluence of pulsed hard X-ray is a main parameter of the equipment beam. At present, theoretical calculation method is widely used. Energy fluence can be calculated according to the dose, energy spectrum and energy absorption coefficient of each energy segment. The principle measuring energy fluence of pulsed hard X-ray by total absorption method is introduced. The photoelectric cell with lutetium silicate (LSO) scintillator is selected as a core component of the detection system, and the measurement system is developed. It is composed of scintillation detector, LSO scintillator, dimmer film, photon collimator, visible light shielding material, power supply and signal collecting system. The conversion coefficient between the incident photon energy and the waveform parameter is calibrated by a standard X-ray source. The energy fluence measurement experiment is carried out with the high-energy beam source of the "Flash II" accelerator as an experimental platform. In order to meet the requirements of the effect test experiments, the series diode structure is used in the accelerator for forming a high strength and large area uniform X-ray source. In the experiment, the LiF TLD is located in the front of the phototube and used to monitor the dose. According to the measured waveform, the actual energy of the incident photons is calculated. Combined with the receiving area of incident photons, the energy fluence of pulsed hard X-ray is calculated. The average measured value is 35.9 mJ/cm(2) in 5 consecutive experiments. Energy fluence calculated from the measured dose and energy spectrum is 39.8 mJ/cm(2). The results of the two methods are compared. It can be found that the experimental result is about 9.8% smaller than the theoretical value. The reasons are as follows. According to the law of exponential decay of rays in matter, in fact, the scintillator cannot absorb all the rays, and some of the rays can penetrate through, the energy of these rays cannot be detected, and thus giving rise to small experimental value. Due to the limited energy point of quasi-monoenergetic source, the sensitivity under the mean photon energy is taken as the sensitivity of the detector, and therefore there is a certain degree of uncertainty. The successful application of the measurement technology provides a good experimental method for the following similar research, and can also provide a reference for X-ray intensity analysis.

通过优化设计法拉第筒的响应电阻和分布电感,在"TPG700"平台上对无箔二极管阴极发射的环形电子束束流进行轴向测试.结果表明,无波二极管工作在低磁场(<1 T)条件下,在二极管电压较低时,优化后的法拉第筒测试获得的电子束束流前沿较慢,随着二极管电压的升高,电子束束流前沿明显变快;在强磁场(>2 T)条件下,法拉第筒测试结果与罗果夫斯基线圈测试结果一致.该结果表明,相比于罗果夫斯基线圈,法拉第筒更能准确地测试出无箔二极管的前向电子束束流.

In this paper is given briefly a survey of situation of simulating pulsed x-ray with high current pulsed electron beam accelerator. It´s indicated that technology of high pulsed power Z-pinch has vast application prospects in the realization of ultraintensive pulsed x-ray simulator and ICF driver as a chief technological way. Also are described the progress and the current status of simulators for pulsed x-ray in China, and proposals for the future development of Z-pinch technology.

Based on a 12-cell transmission line code model, the effects of cell-driving jitters on the output voltage (both the rise time and the flat-top waveform) of magnetically insulated induction voltage adders (MIVAs) were analyzed in detail. Simulation results show that the rise time (0.1-0.9) of the MIVA output voltage is a function of sigma (the standard deviation of the cell-driving jitters) when N (the number of cells connected in series for an MIVA) is small. When cell-driving jitters follow a normal probability distribution, the rise time of the output voltages also accord well with normal distributions. Parameters of these distributions are analytically deduced and presented. For any experimental shot, there is a fiducial probability that the rise time falls into the analytic solution range (within a certain error range). With the same error range, the fiducial probability decreases as s increases, while probabilities that the rise time are higher or lower than this range increase synchronously. Simulation results also indicate that cell-driving jitters have fewer effects on the flat-top peak of the MIVA output voltage. However, a series of ripple voltages is added on the flat-top waveform, and the average peak of these ripple voltages increases as s increases.

This paper presents a method for moderate pulsed X rays produced by a series diode, which can be driven by high voltage pulse to generate intense large-area uniform sub-100-keV X rays. A two stage series diode was designed for Flash-II accelerator and experimentally investigated. A compact support system of floating converter/cathode was invented, the extra cathode is floating electrically and mechanically, by withdrawing three support pins several milliseconds before a diode electrical pulse. A double ring cathode was developed to improve the surface electric field and emission stability. The cathode radii and diode separation gap were optimized to enhance the uniformity of X rays and coincidence of the two diode voltages based on the simulation and theoretical calculation. The experimental results show that the two stage series diode can work stably under 700 kV and 300 kA, the average energy of X rays is 86 keV, and the dose is about 296 rad(Si) over 615 cm2 area with uniformity 2:1 at 5 cm from the last converter. Compared with the single diode, the average X rays' energy reduces from 132 keV to 88 keV, and the proportion of sub-100-keV photons increases from 39% to 69%.

Coupled by the Marx of the “JianGuang-I” facility, a high voltage, low time-delay trigger generator was developed. Working principles of this trigger generator and its key issues were described in detail. Structures of this generator were also carefully designed and optimized. Based on the “JianGuang-I” Marx generator, a test stand was established. And a series of experiment tests were carried out to the study performance of this trigger generator. Experiment results show that the output voltage of this trigger generator can be continuously adjusted from 58 kV to 384 kV. The time delay (from the beginning of the Marx-discharging pulse to the time that the output pulse of the trigger generator arises) of this trigger pulse is about 200 ns and its peak time (0%∼100%) is less than 50 ns. Experiment results also indicate that the time-delay jitter of trigger voltages decreases rapidly with the increase in the peak voltage of trigger pulses. When the trigger voltage is higher than 250 kV, the time-delay jitters (the standard deviation) are less than 7.7 ns.

介绍了利用串级二极管产生大面积脉冲硬X射线的基本原理,建立了串级二极管的等效电路模型,分析了二极管串联工作过程,通过模拟计算给出了串级二极管工作过程的影响因素.串级二极管分压过程分为电容分压、阻抗和容抗分压、真空击穿后动态平衡及阻抗分压四个阶段,二极管电容和真空击穿电压是影响二极管串联初始阶段分压的主要因素,二极管的阻抗变化过程和二极管间隙的击穿时间差决定二极管分压的一致性.

The principle of measuring electron emission threshold of surface area metal electrode is presented. The measurement system of electron emission thresholds of two electrodes is developed. The electron emission characteristics of materials with different roughness degrees or Cr2O3 coating-deposit 40 um are measured in “Chenguang” accelerator. The results show that polishing can suppress electron emission. The higher the roughness degree of material, the lower the electron emission threshold is. Material coated with Cr2O3 has higher electron emission threshold than polished material.

An improved optimal 3-Dimensional (3-D) assignment algorithm based on Multi-source Information (IMFOA) is proposed. The algorithm firstly gets the correlation degree between multi-source measurements of single-sensor and target track through fusing multi-source information by using grey relational analysis algorithm and then a 3-D assignment model based on multi-source information fusion can be got. Further, an improved point- track optimal assignment algorithm is used to complete point-track correlations. In comparison with the Optimal 3- D Assignment (OA) algorithm based on dynamic information and the Improved Optimal Assignment (IOA) algorithm which implements point-track correlation through using marginal correlation probability on the basis of OA algorithm, IMFOA algorithm improves the tracking accuracy of multi-target in varying degrees under different detection scenarios and is an optimal measurement data correlation algorithm with stronger anti-interference.

For improving the effect of multi-target tracking in dense target and clutter scenario, a centralized fuzzy optimal assignment algorithm (CMS-FOA) of three-sensor multi-target system is proposed. And on the base of this, a generalized probabilistic data association algorithm (CMS-FOAGPDA) based on CMS-FOA algorithm is presented. The fusion algorithm gets effective 3-tuple of measurement set by using components of several satisfactory solutions of the fuzzy optimal assignment problem and then uses generalized probabilistic data association algorithm to calculate the update states of targets. Simulation results show that, in the aspect of multi-target tracking accuracy, CMS-FOA algorithm is superior to the optimal assignment (CMS-OA) algorithm based on state estimate and CMS-FOAGPDA algorithm is better than CMS-FOA algorithm. But considering the time spent, CMS-FOA algorithm spends a minimum of time and CMS-FOAGPDA algorithm is exactly on the contrary. Therefore, compared with CMS-OA algorithm, the two algorithms presented in the study each has its advantages and should be chosen according to the needs of the actual application when in use.

The rod pinch diode is perfect as a source of accelerators for flash X-ray radiography by virtue of a small and stable spot.But it is not suitable for intensive current drivers because of high diode impendence of 40~60Ω.However,by employing pre-filled plasma into diode prior to the driving current,the diode impendence can be efectively reduced.Plasma density plays an important role in this process,especially for sheath formation and space charge current in the diode.Analysis and simulation results show that a proper range of plasma density could be 1015~1016cm-3.

针对目前脉冲硬X射线源能谱硬、辐照面积小、辐射场电子份额高无法开展系统电磁脉冲效应实验研究的技术难题,提出了采用复合薄靶软化脉冲硬X射线能谱、降低电子份额的方法.采用MCNP程序数值模拟了电子和光子在不同材料中的输运规律,分析了复合靶结构和材料厚度对X射线能谱、电子份额的影响.以“闪光二号”加速器为电子束源,设计了复合薄靶、X射线窗.实验得到的X射线参数:平均能量121keV;均匀性2∶1情况下,700 cm2平均剂量40 rad(Si),500 cm2平均剂量170 rad(Si)；光子数与电子数的比值大于103,可以开展系统电磁脉冲效应初步实验研究.

Based on the relativistic Brillouin flow theory, electron current and power loss in loss-front stage of coaxial cylinder vacuum magnetically insulated transmission line (MITL) are deduced under limiting current approximation. Through the particle-in-cell (PIC) model, loss currents and loss powers under different anode voltages are simulated. Simulation and theory results show that the proportions of loss current and loss power to the total current and power decrease when cathode-anode voltage increases. Beyond 4MV, limiting current approximation fits simulation results better than minimum current approximation. At voltages higher than 10 MV, relative error from limiting approximation is under 10%, while it exceeds 50% under minimum current approximation. This work is meaningful for establishing full circuit simulation of MITL system.

The 1.2MV, 70ns FWHM induction cell is developed for a 3MV Induction Voltage Adder (IVA) accelerator with three series connected cavities through a high voltage, vacuum insulating transmission line (VITL) driving rod-pinch diode (RPD) for radiography. The experimentally measured maximum relative permeability of IVA used amorphous material under pulse excitation is consistent with saturation wave model with flux density changing rate dB/dt greater than 10T/μs up to 32 T/μs. The remanence ratio Br/Bs is experimentally measured for IVA pre-annealed amorphous cores. Upon experimental results, cores in each cell are designed and determined according to current transfer efficiency and volt-second integral necessary for each induction cavity, and peak field preventing VITL bore negative surface from electron emission. The field analysis is carried out for designing VITL vacuum stack and oil cavity that contains cores and azimuthal transmission line with operation field stress being about 50% critical breakdown field. The prototype cell tests validate electric field safety and magnetic core performance. With magnetization inductance and resistance of eddy current calculated for inductive cell, the IVA accelerator circuit model is set up, and simulation predictions approximately according with experimental results are presented.