赝火花脉冲电子束束流传输特性分析

对赝火花放电实验中观察到的脉冲电子束的椭圆形束斑、自箍缩以及细丝效应进行了介绍，并用电磁动力学分析了其成因和影响因素。     

Sub-ns Jitter, 1ns Risetime and 10kV Rectangular Pulse Trigger Generator

A new rectangular pulse trigger generator has been developed which can generate two 10 kV pulses with a risetime less than 1 ns, a jitter of 0.2 ns and a width of about 10 ns and 40 ns, respectively. This generator uses two polymer-foil switches and 25 ohm Blumlein transmission lines composed of two-parallel standard coaxial cables discharging into two 50 ohm output cables. The pulse width and the delay between two pulses can be adjusted by changing the length of the cables.     

强流脉冲中性源的等离子体发生器电源

本文叙述了强流脉冲中性源等离子体发生器电源的特殊要求,给出了用于7×35cm~2大面积源的灯丝电源和弧流电源的主电路。     

Factors Influencing the Electron Yield of Needle-Ring Pulsed Corona Discharge Electron Source for Negative Ion Mobility Spectrometer

A simple negative ion mobility spectrometer （IMS） is designed and used to investi- gate the factors that influence the number and efficiency of electrons generated by the needle-ring pulsed corona discharge electron source. Simulation with Ansoft Maxwell 12 is carried out to analyze the electric field distribution within the IMS, and to offer the basis and foundation for analyzing the measurement results. The measurement results of the quantities of electrons show that when the drift electric field strength and the ring inner diameter rise, both the number of ef- fective electrons and the effective electron rate are increased. When the discharge voltage becomes stronger, the number of effective electrons goes up while the effective electron rate goes down. In light of the simulation results, mechanisms underlying the effects of drift electric field strength, ring inner diameter, and discharge voltage on the effective electron number and effective electron rate are discussed. These will make great sense for designing negative ion mode IMS using the needle-ring pulsed corona discharge as the electron source.     

50kV,1ns前沿高压脉冲源的研制

介绍了50kV,1ns前沿高压脉冲源的工作原理及设计部件的研制,给出了脉冲高压源的输出波形,该高压脉冲源与有界波电磁脉冲模拟器辐照天线相接,可在其工作空间内产生前沿为1．2ns,脉宽为50ns的电磁环境,用于电子系统的电磁脉冲效应研究。     

甲醛水溶液的电子束辐射分解

介绍了在电子能量3~5 MeV、最大束流功率约0.8 kW电子加速器直接辐照下,3种不同初始浓度(25、500、11 000 mg/L)甲醛水溶液的辐射分解过程,并用紫外(UV)吸收谱和液相色谱(LC)法分析了辐解样品。结果显示：溶液中剩余甲醛的质量分数随吸收剂量的增大呈指数衰减,其主要辐解产物至少有4种,其中3种为包括甲酸在内的可确认结构的小分子产物,1种为大分子产物。此外还发现添加辐解助剂NaOH后,甲醛水溶液电子束辐解效率提高近2倍。以上结果表明,电子束辐射有望成为辐解各种浓度甲醛水溶液的高效手段。     

小型静态CT用多焦点X射线源电子束偏转系统研究

第5代全静态电子束CT（EBCT）能在被检测物体、射线源和探测器均处于静止状态下完成CT扫描成像。这种EBCT成像方式既可应用于粉体材料、生物活体样品等易形变物体的CT检测,又可应用于物流包裹、在役管线等的快速CT检测。高精度的电子束偏转系统是静态CT成像多焦点射线源的关键技术之一。本文基于麦克斯韦电磁场相互作用理论,探讨了电子束在均匀磁场、小偏转角、近轴区域内的散焦、畸变及灵敏度特性,研究了影响电子束扫描系统焦点位置重复精度的物理参数及电子束在靶平面上的扫描偏转量与偏转线圈电流的线性关系。并设计、加工制作了一种小型高精度多焦点X射线的电子束偏转扫描系统,实验采用直径0.1 mm标准针规电子束扫描DR投影图像序列,验证了电子束偏转系统有良好的偏转线性,偏转量正比于O点的磁场强度,而与电子束的位置等初始条件无关。实验通过电子束偏转系统控制电子束偏转扫描,获得了熔断式保险管（Ø100 μm）的250个 X 射线视角投影,完成了第5代全静态三维CT重建图像。     

电子束辐照聚二甲基硅烷的结构分析

在室温、真空条件下,利用加速器产生的高能电子束辐照聚二甲基硅烷（PDMS）试样,研究吸收剂量对其结构的影响。通过气相色谱质谱联用分析可知,辐照过程中产生了少量H₂和CH₄,且H₂的产率高于CH₄。FT-IR、激光拉曼光谱以及XRD分析结果表明,经超高剂量（MGy级）辐照后,聚二甲基硅烷的化学结构未发生明显变化,其晶态结构也未遭破坏。这些结果说明,PDMS具有异乎寻常的耐辐射性能,这可能归因于其主链上规整Si—Si键的σ电子离域运动所形成的σ共轭体系的特殊结构。     

电子束引出窗冷却研究

研究1MeV、40mA工业辐照电子加速器引出窗钛膜受力状况,确定钛膜在大气作用下的几何形状,计算电子束在钛膜上各点的入射角度和相应的穿越深度,给出电子束在钛膜上的能量损失分布与钛膜强度、厚度、跨度之间的关系。分析钛膜自身热传导和热辐射的散热能力,表明强迫风冷是提高引出窗输出能力的重要冷却方式。结合数值模拟方法,重点研究强迫风冷的散热能力与出口风速、钛膜曲率半径之间的关系。发现常规风冷结构设计中可能出现回流区,成为窗膜的冷却盲点,需通过结构优化设计消除回流区的影响。     

Simulations and Measurement of Electron Energy and Effective Electron Temperature of Nanosecond Pulsed Argon Plasma

The behavior of argon plasma driven by nanosecond pulsed plasma in a low-pressure plasma reactor is investigated using a global model, and the results are compared with the experimental measurements. The time evolution of plasma density and the electron energy probability function are calculated by solving the energy balance and Boltzmann equations. During and shortly after the discharge pulse, the electron energy probability function can be represented by a bi-Maxwellian distribution, indicating two energy groups of electrons. According to the effective electron temperature calculation, we find that there are more high-energy electrons that play an important role in the excitation and ionization processes than low-energy electrons. The effective electron temperature is also measured via optical emission spectroscopy to evaluate the simulation model. In the comparison, the simulation results are found to be in agreement with the measure- ments. Furthermore, variations of the effective electron temperature are presented versus other discharge parameters, such as pulse width time, pulse rise time and gas pressure.     

强流溅射源负离子出束实验研究

在离子源实验台架上，利用200型强流溅射离子源进行8种元素的负离子出束实验研究。这些负离子对应元素的电子亲合势大部分接近或小于零，负离子难以形成。实验中尝试使用不同的靶材料和辅助气体产生负离子，以提高负离子束的束流强度。     

微波零相位法测量超导加速器ps级电子束纵向长度

本文基于微波零相位法,将中国工程物理研究院太赫兹自由电子激光(CTFEL)2×4-cell超导加速器的下游腔作为零相位腔,测量了上游腔增能后的电子束纵向长度,并通过束流动力学模拟证明,当两个超导腔正常工作时,上游腔出口处的电子束纵向长度与下游腔出口处的接近。实验结果表明,CTFEL 2×4-cell超导加速器能实现半高宽小于6.8 ps的电子束,满足装置出光要求。     

1 MV杆箍缩二极管辐射特性实验研究

依据现有的实验室驱动源能力建立杆箍缩二极管（RPD）粒子模拟计算模型,获得了工作电压为1 MV的RPD电参数特性及电子、离子时空分布特性,并设计了RPD实验装置。在1 MV驱动源平台上开展了实验研究,实验中采用B dot、D dot、热释光剂量片和SiPin二极管测试了RPD电流、电压、辐射剂量和光脉冲信号,分析了RPD电参数及X射线辐射特性。结果表明,阳极采用1.5 mm钨时,1 MV电压下1 m处辐射剂量约1 R,并得出剂量与电压Ud、电流Id的关系式D(R=1 m)=120U1.55d∫Iddt;二极管阻抗范围为26.4~36.7 Ω,空间电荷限制阶段平均阻抗下降率大于2 Ω/ns,磁绝缘阶段平均阻抗下降率小于0.5 Ω/ns;光脉冲宽度较电压脉冲宽度约缩短20%~30%,与电压、电流的关系为∝IdU1.55 d。实验测试的剂量和光脉冲信号结果与拟合计算式计算结果符合较好。     

PIC-MC Code to Model Fast Electron Beam Transport Through Dense Matter

A PIC （particle-in-cell）-MC （Monte Carlo） code to model electron beam transport into dense matter is developed. The background target is treated as a cold, stationary fluid and the fast electrons as particles with the relativistic motions. The process is described by a particle-in-cell method with consideration of the influence of both the self-generated electric and magnetic fields as well as collisions between the fast electrons and the target. The collisional part of the code is solved by the Monte Carlo-type method. Furthermore by assuming that the background current balances with the fast electron current, the electric field is given by the Ohm＇s law and the magnetic field is calculated from the Faraday＇s law. Both are solved in a two-dimensional cylindrical geometry. The algorithms implemented in the code are demonstrated and the numerical experiments are performed for monoenergy homogeneous fast electron beam transport in an aluminum target when the fields, collision and angular scattering are switched on and off independently.     

Three-Dimensional PIC-MC Modeling for Relativistic Electron Beam Transport Through Dense Plasma

We have developed a three dimensional （3D） PIC （particle-in-cell）-MC （Monte Carlo） code in order to simulate an electron beam transported into the dense matter based on our previous two dimensional code. The relativistic motion of fast electrons is treated by the particle-in-cell method under the influence of both a self-generated transverse magnetic field and an axial electric field, as well as collisions. The electric field generated by return current is expressed by Ohm＇s law and the magnetic field is calculated from Faraday＇s law. The slowing down of monoenergy electrons in DT plasma is calculated and discussed.     

脉冲离子束作用下金属氚化物氦释放测量技术研究

为认识脉冲离子束作用下金属氚化物的氦释放行为,建立了脉冲离子束作用下金属氚化物氦释放测量系统。利用标准体积气体取样装置,采用气体反扩散法,对系统的容积比、灵敏度进行了实验标定。在此基础上,发展了脉冲离子束作用下金属氚化物氦释放的测量技术,开展了脉冲离子束作用下金属氚化物氦释放实验研究。结果显示,单次脉冲离子束作用下金属氚化物的氦释放呈脉冲式,释放量最大可达10~(13)个原子以上。     

基于电子束扫描阵列微焦点射线源的倒置结构Micro-CT成像研究

倒置几何结构CT成像系统理论上具有扫描视场大、图像信噪比好、锥束伪影小等优点,但其多焦点、稀疏角的扫描模式亦会带来投影数据截断、稀疏和局部数据冗余等问题。本文利用电子束扫描阵列微焦点射线源和高分辨率小面积探测器等构建了一种新型高分辨率、大视场的倒置几何结构Micro CT实验系统(IG Micro CT)。针对该系统多焦点、稀疏角扫描模式下的投影数据截断和稀疏等特点,提出一种图像先验约束的全变分正则化SART迭代CT图像重建算法。首先通过仿真实验对图像重建算法进行了验证,并对阵列微焦点数量、旋转扫描分度数量等扫描参数进行优化,最后在IG Micro CT实验系统上获得了高分辨的Micro CT测试图像。实验结果表明,本文提出的算法适用于IG Micro CT系统,解决了投影数据截断、稀疏采样和局部数据冗余带来的条状等伪影问题,并验证了IG Micro CT这种新型成像方式的可行性。     

辐射预硫化技术在EPDM发泡材料制备过程中的应用研究

以三元乙丙橡胶（EPDM）为基材,采用电子加速器辐照技术对其进行辐射预硫化处理,研究了敏化剂TMPTMA对硫化参数的影响及其敏化效果,并研究了不同吸收剂量下,发泡制品的外观、材料力学性能、吸水率和压缩永久变形的变化情况。结果表明：TMPTMA对三元乙丙橡胶有较好的敏化效果;在辐射吸收5～15kGy剂量范围内,发泡材料的闭孔性变好,力学性能也随之提高。     

The Propagation Characteristics of the Electron Beam with Initial Modulation

The propagation characteristics of the beam under various initial conditions are investigated by means of PIC method. The influences of density modulation and velocity modulation on the propagation characteristics are discussed and compared. The results reveal that by changing the amplitude of the two kinds of modulations and the phase difference between them, the distribution property of the first harmonic of the current density can be adapted along the beam propagating path, which is a feasible method to enhance the beam-wave interaction efficiency in Cerenkov HPM devices.