强流电子束入射角二维分布测量方法

电子束与靶物质相互作用时的入射角测量是强流电子束热-力学效应研究中的难点问题. 提出了一种新的基于覆盖不同厚度衰减片微型法拉第筒阵列的电子束入射角测量方法, 与现有方法相比, 可获得具有时域特性和位置分布的强流电子束入射角分布. 以此方法进行了入射角二维分布(r, θ)测量实验, 结果表明, 电子束入射角二维分布与束流箍缩情况紧密相关. 如果箍缩不明显, 则电子主要在自身做回旋运动的同时沿着电力线运动, 多以垂直或者小角度(40°以下)轰击到阳极靶面; 如果箍缩明显, 受E×B漂移影响, 电子束入射角度会明显变大, 从40°以下增至60°左右.     

测量电子束流的小型法拉第筒

介绍一种测量束流强度不大于50kA,能量不超过0.8MeV的小型法拉第筒。经标定,此法拉第筒上升前沿小于6ns。已用于契伦柯夫自由电子激光的传输束流测量。     

Analysis of the nitrogen ion beam generated in a low-energy plasmafocus device by a Faraday cup operating in the secondary electronemission mode

The energy distribution and flux of fast nitrogen particles generated in a Mather-type plasma focus device operating at 0.4 Torr of N₂ pressure is reported. A Faraday cup operating in the secondary electron emission mode was employed. To determine the total number of beam particles, multiple scattering of the ions was taken into account. It has been possible to register the ion energy up to a lower kinetic energy threshold of ≈50 keV, which is a value much lower than that obtained with a Thomson spectrometer in a previous work     

Faraday dosimetry characteristics of PIII doping processes

A Faraday cup dosimetry system was developed and characterized to address the issues of plasma immersion ion implantation (PIII) dose measurements. Pure ion current was measured by using an electrostatic suppression mechanism combined with high-bandwidth fiber-optic electronics to isolate high-voltage pulses and eliminate the primary and secondary electron and displacement currents. The ion-current waveform measured by the Faraday cup was verified by an XPDP1 particle-in-cell simulation. All of the positively charged ions striking the target surface were counted for implant dose by the Faraday cup so that both high-energy implant dose during the pulse and low-energy implant dose between pulses can be separately determined. The dose of the high-energy implant during pulses, which is more influential on the junction depth, can be measured with a fairly good accuracy, although the low-energy implant dose cannot be accurately measured due to more complicated surface effects. Compared with other dosimetry methods for PIII doping processes, the Faraday dosimetry technique offers better repeatability and controllability for PIII processes due to its direct, in-situ manner.     

微型法拉第筒阵列束流均匀性测量

研制了一种用于测量强流脉冲电子束束流均匀性的微型法拉第筒阵列,其直径为22mm,由5个微型法拉第筒组成,最大可测束流密度为38A/mm2。利用该系统测量了二极管阳极靶面的束流密度,得到了阳极靶面束流均匀性的分布情况。结果显示,阳极靶面中心处束流密度高于靶面其他位置,靶面束流存在弱箍缩,束流局部均匀,大面积不均匀,束流密度呈径向分布。该结果与理论预期和仿真计算符合较好。     

法拉第筒阻抗对二极管电子束流性能的影响

 分析了法拉第筒阻抗对二极管电子束流性能的影响, 研制了一种安装在阳极座中测量阳极吸收束流的法拉弟筒, 并用它测量了81-7M -01强流相对论电子束加速器二极管阳极吸收束流。     

闪光机回流离子效应及抑制方法

 采用束包络方程分析了单脉冲和多脉冲情况下回流离子对强流相对论电子束聚焦的影响。分析结果表明,单脉冲情况下通过缩短焦距,仍可以获得较小的积分焦斑,而在多脉冲情况下回流离子将导致电子束完全散焦。通过数值模拟和实验研究了利用薄膜阻挡回流离子的可行性,对不同薄膜在电子束作用下的温升及动力学行为的模拟结果表明,在1.06 μs的时间尺度内,薄膜虽然发生了不同程度的膨胀,但是仍然有足够的材料可以阻挡离子回流。在神龙一号加速器上,通过法拉第筒测量了靶前放置和不放置薄膜情况下的离子信号,实验证实了薄膜至少能够将离子约束在薄膜和转换靶之间长达数十μs。     

Relativistic electron beams detection in a dense plasma focus

Fast electron beams into a hollow anode of a small plasma focus machine (2 kJ, 4 μF) were measured. The diagnostic method designed for this purpose is founded in a small Rogowski coil introduced into a cavity performed in the anode. By means of this, electron beam pulses of about 10 ns width generated in the plasma focus are detected. Simultaneously, hard X-ray signals obtained from a scintillator-photomultiplier system are registered. The electron beam energy was measured through the time-of-flight of the electrons between probe and anode top. The beams are found to be relativistic and its energy is into the range of hard X-rays energy. An analysis of signal intensities and relative delays for three hundred shots are here presented. Received 28 February 2002 / Received in final form 7 May 2002 Published online 24 September 2002     

双脉冲电子束源实验研究

 利用现有2MeV直线感应注入器，通过改造，将其次级功率源和8个感应腔分成2组，使之交替工作，建立了一台双脉冲电子束源。二极管电压脉冲幅度达到1MeV，电子束脉冲持续时间为120ns，脉冲间隔可以根据需要在100~500ns间进行调节。实验结果表明：该双脉冲电子束源可以产生双脉冲电子束，其电压幅度差值小于2%，束流可达3kA，并且工作稳定，利用该装置可以进行多脉冲二极管物理和天鹅绒多脉冲发射特性实验研究。     

宏观尺寸弯曲石英管对中低能电子束的导向作用

研究了宏观尺寸的弯曲圆柱形石英管对 1 100, 1 300和1 500 eV 3种能量电子束的导向作用, 并对实验结果与相同材质和尺寸的直管的情形进行了分析对比。 实验中利用一个位置灵敏法拉第筒对从石英管出射的电子束进行探测, 获得从管道中出射的电子束流强度在位置灵敏法拉第筒各道上的分布, 其结果显示宏观尺寸石英管对电子束存在导向作用。 与慢速高电荷态离子和绝缘毛细管相互作用的物理过程类似, 这种导向效应是由电荷在管壁内表面自组织充电引起的。 实验还发现, 入射电子束流的强度越强, 其导向作用越明显, 这与微观尺寸毛细管对慢速高电荷态离子的导向作用不同。 石英管导向能力与管的尺寸、 形状及材料之间的关系还有待进一步的系统研究。 It was inevstigated in the experiment that the guiding effect of electron beam with energy of 1 100, 1 300 and 1 500 eV through a bended cylindrical quartz tube with macro sized. A position sensitive Faraday cup was developed and used to detect the electron beam transmitted through the quartz tube, and the distribution of transmitted beam current on each channel of the Faraday cup was acquired. Results indicate the existence of guiding effect which is due to the self organized charge up in the inner wall of the quartz tube similar to that of the highly charged ions. We also found that the guiding ability of the tube is related to the incident beam intensity. The relationship between the guiding ability and the material as well as the size of the tube is to be studied in the near future.     

测量行波管电子注的法拉第筒的热分析

利用ANSYS软件对测量行波管电子注截面的法拉第筒探头进行了热分析研究.分析了在单脉冲情况下,测量各种直径的不同脉冲功率密度的电子注、不同脉冲宽度对法拉第筒温度的影响,研究了测量不同功率密度的电子注可以使用的脉冲宽度.结果表明,仅法拉第筒上的注斑区域温度迅速上升,温度梯度较大,其它部分温度基本不变,为保证法拉第筒能够持...     

Experimental study of the influence of the processes in the ion-beam drift space on beam current measurements

A method is proposed for separate measurements of the current produced by slow charge-exchange ions and that produced by the ions generated due to gas ionization by the beam ions and fast secondary electrons in the beam drift space. The method is based on an analysis of the current distribution over the electrodes of a modified Faraday cup with nonequipotential electrodes and allows one to determine the coefficient of ion-induced electron emission from the ion collector and the charge-exchange cross section of the accelerated ions. The method has been employed to measure the current of an argon ion beam with an ion energy from a few electronvolts to several tens of kiloelectronvolts and to study the processes in the beam drift space at pressures of 0.03–0.15 Pa.     

Enhanced betatron radiation by a modulating laser pulse in laser wakefield acceleration

We propose a new idea to enhance and control the betatron radiation by using a modulating laser pulse in laser wakefield acceleration. In this scheme, a high-power laser pulse is used for self-trapping and acceleration of the plasma electrons and the accelerated electron beam is modulated by a separately-propagating laser pulse for large amplitude betatron oscillations and microbunching. In this way, the relatively low power modulating laser pulse can enhance the X-ray photon flux and energy significantly. We performed two-dimensional particle-in-cell simulations to demonstrate the idea and the results show that a sub-TW laser pulse is enough for electron beam modulation and it can generate easily-controllable fs X-ray pulses with a wide range of photon energies from soft X-rays to hard X-rays.     

High-power microwave generation using a ferroelectric cathodeelectron gun

A two-stage 500 kV 200-A ferroelectric electron gun has been designed, fabricated, tested, and used in a high power microwave amplifier experiment. We report on the operational characteristics of the gun including measurements of the beam dynamics. The optimum conditions for application of the trigger and its timing are also reported. Faraday cup measurement shows that the beam radius is 4.1 mm, in good agreement with simulation. The gun is designed for use in traveling-wave tube amplifiers, and testing of an X-band amplifier driven by the gun is reported. A peak output power of 5.9 MW has been observed from a single stage amplifier driven by a 100 A. 450 kV beam. This corresponds to energy converging efficiency of 13.1% and is the first observation of high power (~MW) microwave generation using the beam generated from a ferroelectric cathode,     

12MeV LIA轫致辐射靶面回流离子测量

 强流高功率脉冲电子束聚焦成mm量级的束斑后，打击到轫致辐射靶的过程中会产生回流离子，它会导致电子束被提前聚焦，在预定的靶面形成散焦。描述了法拉第筒对12MeV 直线感应加速器的轫致辐射靶面可能产生的离子及其参数进行的实验测量，并对实验结果进行了分析讨论。结果表明在靶前60°~70°方向未发现回流离子。     

Short soft x‐ray sources

In this work we report on the characterization of pulsed soft x‐rays emitted from laser‐produced plasma. The plasma was generated by a pulsed KrF excimer laser focused on pure Si, Cu and Ta targets by 40, 80 and 120 mJ laser energies. The utilized detector was a very sensitive Faraday cup which opportunely biased was able to record time‐resolved signals of x‐rays and to estimate their energy. The found x‐rays energy values were compared with the ion temperature of the plasma obtained by fitting the time‐resolved ion current signals with a shifted Maxwell‐Boltzmann velocity distribution. The results showed that the laser‐produced Ta plasma induced bunches of x‐rays having in average the highest energy values and it was also characterized by ion temperature higher than the ones of the laser‐produced Si and Cu plasmas. Copyright © 2009 John Wiley & Sons, Ltd.     

FLUKA程序在法拉第杯设计中的应用

法拉第杯是加速器束流强度绝对测量装置,其收集效率对于法拉第杯的设计至关重要。应用蒙特卡罗软件FLUKA对北京正负电子对撞机直线加速器分析磁铁AM2处的法拉第杯进行模拟设计。给出了法拉第杯不同部位对收集效率的影响曲线,并给出了入射电子在法拉第杯中的能量沉积分布与带电粒子分布图,最终得到了优化的法拉第杯尺寸,使得对入射电子的收集效率达到99.73%。     

用偏压法拉第筒测量强流脉冲离子束

 分析了偏压法拉第筒测量强流脉冲离子束的原理和影响测量准确度的主要因素,研制了一种结构简单的偏压离子法拉第筒阵列,利用该装置测量了200kV小型强流脉冲离子束源的束流密度分布,束流中心密度最大值约为170A/cm²。     

二次电子发射对质子束流测量精度的影响

二次电子发射直接影响法拉第探测器测量质子束流的精度,减小或消除二次电子发射的影响是提高束流测量精度的关键。根据二次电子补偿原理设计了二次电子补偿型同轴法拉第探测器,实验发现探测器测量质子束流强度时不能完全实现二次电子补偿。为改进和完善探测器的设计,从理论上分析了补偿片未能完全消除二次电子对束流测量影响的原因,是由于补偿片前向发射二次电子数目大于收集极后向发射二次电子数目所致。为此设计了质子束穿过金属箔发射二次电子测量装置,测量得到能量为5~10MeV质子穿过10μm厚铜箔时前向与后向发射二次电子产额,验证了理论分析的正确性。     

电子束潘宁阱非中性等离子体中电子聚心约束实验

介绍了电子束潘宁阱非中性等离子体实验。利用具有小正则角动量电子束的注入,在装置中形成了有稠密核心的电子等离子体。当潘宁阱中电磁场匹配是,约束电子的散射最强。注入电子束的束流强度超过一定的阈值时,电子聚心状态才能形成。阈值与潘宁阱电场成正比。