二维多丝室探测器读出方法的优化

中国散裂中子源将建设一台基于~3He气体的二维多丝室,作为多功能反射谱仪束线的中子探测器.基于已有的研究,为优化选择二维多丝室探测器的丝结构,本文研究了三种不同的丝结构,并采用重心读出方法和数字读出方法进行了探测器的性能测量,得到了满足多功能反射谱仪探测器需求的读出方法.实验结果表明:对同种丝结构的二维多丝室探测器,重心读出方法的位置分辨和成像性能都好于数字读出方法;基于重心法读出的多丝室探测器位置分辨率可以达到约160μm,基于数字读出方法的多丝室探测器位置分辨率可以达到约400μm.优化设计的丝结构为:基于重心读出法的阳极丝间距1.5 mm、读出通道间距4 mm,基于数字读出法的阳极丝间距1.5 mm、读出通道间距2 mm.优化设计的丝结构均能满足谱仪的位置分辨要求.     

多丝室工作于自猝灭流光模式下定位特性的研究

对多丝室运行于自猝灭流光(SQS)模式下的定位性能进行了实验研究.用两种不同的丝室结构,以Ar和CO₂的混合气体作为工作气体,在不同的CO₂含量比例及高压下测试了感应电荷信号在阳极丝周围电极上的分布.以阳极丝相邻电极上感应电荷的比来确定入射粒子在垂直阳极丝方向上的位置,分辨率σ_x好于350μm.由阴极面上感应电荷的分布,用重心法确定入射粒子在沿阳极丝方向上的位置,分辨率好于250μm.     

倾斜多丝正比室辐射状阴极条感应电荷重心读出的定位性能研究

本文针对倾斜多丝室辐射状阴极条的具体结构,研究了阴极面上感应电荷密度分布,给出了四或五根条取样时重心读出定位修正函数和相应的定位精度,用⁵⁵Fe X射线进行了定位测量,实验和理论符合得较好.     

塑料流光管感应读出的某些特性

本文介绍了新型塑料自猝灭流光管的感应读出特点. 对用于二维读出方式的感应条上的感应输出电荷脉冲分布谱与高压关系及相邻条上的感应电荷分布进行了研究. 对空间分辨率进行了测量分析及估算. 文中并对分布谱的双峰效应进行了解释, 指出阳极丝两侧的流光距感应条有远近两类是产生双峰的根源. 最后报导了感应板(Pad)读出方式的初步测量结果.     

塑料流光管感应读出的某些特牲

本文介绍了新型塑料自猝灭流光管的感应读出特点.对用于二维读出方式的感应条上的感应输出电荷脉冲分布谱与高压关系及相邻条上的感应电荷分布进行了研究.对空间分辨率进行了测量分析及估算.文中并对分布谱的双峰效应进行了解释,指出阳极丝两侧的流光距感应条有远近两类是产生双峰的根源.最后报导了感应板(Pad)读出方式的初步测量结果.     

多丝室在北京试验束中的应用

 介绍了北京正负电子对撞机直线加速器附设e，p试验束多丝室的结构及工作机理。该室间隙6 mm，窗口面积80 mm×80 mm，位置灵敏面积50 mm×50 mm；阳极丝和阴极丝分别采用直径为20 mm和50 mm镀金钨丝，阳极丝距2 mm，阴极丝距0.7 mm,每6根阴极丝并联构成阴极条，阴极条间距4.2 mm。采用阴极条感应重心读出分辨位置，对5.9 keV的γ光子，获得优于0.3 mm (FWHM)的位置分辨;对1.1 GeV电子束流，获得0.224 mm (FWHM)的位置分辨。     

用于HL－1M的弯晶谱仪中的MWPC的空间分辨测试

本文简述了多丝正比计数室（ＭＷＰＣ）的结构、工作原理、读出方式及位置分辨测试方法，测得多丝正比计数室的位置分辨为３００±２０ｕｍ。     

CEE-TPC中GEM读出探测器传输性能实验研究

气体电子倍增器(GEM)因其具有较好的位置分辨以及各项同性的二维结构等优点,近年来受到了广泛的关注,在HIRFL-CSR上正在建设的低温高密核物质测量谱仪(CEE)也计划使用GEM作为TPC的读出探测器。不同电场条件下GEM探测器的传输特性对探测器的有效增益及能量分辨有较大影响。文中研究了单层GEM探测器中漂移区电场及感应区电场对探测器传输特性的影响;随后研究了双层GEM探测器的电压分配及传输区电场对探测器电荷传输性能的影响。结果表明,在单层及多层GEM探测器中,漂移区电场、传输区电场及感应区电场主要通过改变电子透过率和GEM雪崩电场强度及分布影响探测器的电荷传输性能,进而影响探测器的有效增益及能量分辨。以上实验结果表明GEM探测器是CEE-TPC读出探测器的理想选择,同时测试结果也为TPC中多层级联GEM工作点的选择提供了参考依据。     

二维空间电荷限制流实验研究

对基于圆柱平板结构电子枪的二维空间电荷限制流进行了研究.采用粒子模拟软件详细探讨了二维空间电荷限制流随间距、电压、逸出功、温度、阴极结构等物理量的变化关系.设计了一种实用圆柱平板结构电子枪,对其空间电荷限制流和发射性能进行了实验探索.通过测试,发射电流与二维模型的比较吻合,远大于一维模型的结果.     

高温等离子凝聚体存在的新原理

本文详细地考虑了影响带单一符号电荷的粒子束以下四个因素:平行于粒子束轴的外磁场;粒子束在某种意义下的旋转;由于体电荷引起的粒子间相互排斥力以及速度的温度分布,因而得到束中粒子的某种稳定运动状态的结论。这种稳定状态的特征是粒子束有非常清晰的圆柱形边界,其半径看来不是任意的,而由上列各因素所决定。也就是说,粒子束有一个有效半径,温度和磁之间存在着一定的关系式,取适当的磁场和粒子束大小的数值,可以期望温度达到10¹⁰—10¹²°K的数量级。粒子束并不以回旋加速器频率旋     

A system for proton beam control during radiotherapy

A system for the on-line control of proton beam profiles and track has been designed and constructed to guarantee the quality assurance of radiotherapy carried out in the Medical-Technical Complex of the Joint Institute for Nuclear Research. To measure the horizontal and vertical profiles of the beam in the treatment room, a multiwire ionization chamber has been designed and constructed. The chamber consists of two anode and three cathode electrodes. Each anode electrode contains 30 wires 0.1 mm in diameter separated by 3 mm. To control the beam track, four industrial semiconductor diodes 2D212A designed for radio engineering application were used. The system is installed in front of the first collimator in the peripheral part of the beam, so that it does not disturb the operated part of the beam. Output signals from the ionization chamber and the diodes are processed by a specially constructed electronic device connected to a personal computer. It utilizes 64-channel 16-bit charge-current converters (TERA chip). One-years’s experience of the operation of the system in proton therapy treatment sessions has shown its high reliability and sensitivity to proton beam parameters. The accuracy of controlling the asymmetry of the beam profiles is 2% and the track deviations are equivalent to 0.2 mm of water.     

THE PROTOTYPE OF THE TIME EXPANSION CHAMBER

The prototype of the time expansion chamber, one kind of drift chambers, inwhich the drift region and amplification region is well separated, is described. Its prin-ciple, characteristic, construction and some experimental results are given in detail, Theseresulte are: signals of ionization process along a single charged particle track; the driftvelocities of the electrons in several gases; and the counts distribution of the ionizationclusters in the unit track of a beta particle. And some possible improvements of theseexperiments and the possible applications of this chamber are discussed.     

Secondary electron yield from stainless steel surface coated with titanium nitride

The experiment on measurement of secondary electron yield from surface of a stainless steel Kh189 sample covered with titanium nitride is performed at stand “Recuperator”. This work is related to known problem of electron clouds formation in a vacuum chamber by a propagating charge particle beam. An original method of secondary electron yield measurement was developed in this experiment. The obtained results allow one to estimate efficiency of coating nitride titanium.     

ECR离子源外电子注入技术研究

使用电子枪对ECR（Electron Cyclotron Resonance）等离子体注入外电子束是继铝衬弧腔、偏压盘之后,对等离子体电子的额外补充的又一种手段,通过向弧腔中注入一定能量与流强的电子束,以期提高引出束流的流强与电荷态。但由于该方法可控参数繁多,经验积累与报道资料都很少,且设计与操作远不如偏压盘等手段简便,故一直未能得到深入研究。通过以三维仿真软件CST粒子工作室对注入到弧腔电子束的运动轨迹的模拟结果为依据、以18 GHz ECR蒸发冷却源为平台,进行了ECR等离子体注入电子束的实验,结果表明:在一定实验条件下,当注入电子束能量超过1 800 eV时,会产生一种引出的离子束流的激增现象。在这个现象中,脉冲与直流的流强均比未注入电子时要高,束流电荷态向高价方向移动,且可通过控制实验条件来控制这种现象。最后对于这种电子并未通过共振面,却能起到提高电荷态与流强的作用进行了分析与讨论,并认为该现象在改善直流束与脉冲束性能的方面都有着积极的意义。The injection of the electron beam into the ECR (Electron Cyclotron Resonance)plasma by electron gun is a new method for the additional supplementary of the plasma electron, following the aluminum chamber wall and the bias plate, we are expecting for the higher current and charge state of the ion beam with it. However, because of the controllable parameter's variety, the lack of the accumulation of experience and data, and the shortage of convenience in designing and experimental practicing compared by biased disk and other means,it has always not been intensively studied. In this article, we take the 18 GHz ECR Ion Source using evaporative cooling technique as experimental platform, do the experiment of injecting electron into ECR plasma base on the simulation result of the electron beam's path in ECR's chamber by the 3D simulation software CST the particle studio. It shows that a pulsing leap of the current of the extracting ion beam appears when the injecting electron's energy is above 1 800 eV. In the mean time, the top of the pulse and the average current of the ion beam rises, the ionization state moves to a higher level. This phenomenon can be turned on and off by controlling the experimental condition. At the last part of the article, we discuss this improvement of the current and charge state of the ion beam despite of the position's missing between the injection of electron beam and the resonance surface, and hold the opinion that this phenomenon is positive to both pulsed and direct beam.     

Numerical simulation for space charge dominated beam transport

To simulate the intense bunched beam transport, a computer program LEADS-3D has been developed. The particle trajectories are analysed with the Lie algebraic method. The third order approximation of the trajectory solutions is made with space charge forces off, and the second order approximation is made with space charge forces on. The particle distribution in the 3D ellipsoid is uniform or Gaussian. Most of the conventional beam optical elements are incorporated in the code. The optimization procedures are provided to fit the beam lines to satisfy the given optical conditions.     

基于PIC方法的二维束流动力学模拟程序及其初步应用

为了深入研究强流负氢束在强流质子回旋加速器CYCIAE-100轴向注入线中的传输, 利用split-operator方法分解外场和束流自身的空间电荷场的作用. 对外 场利用单粒子跟踪技术, 采用一阶线性近似; 对空间电荷场采用PIC方法, 利用 快速傅里叶变换求解Poisson方程. 用FORTRAN95语言开发了一个基于面向对象技术的二维宏粒子传输计算程序CYCPIC2D, 本程序可以计算任意分布的强流束在输运线上的传输.最后给出了对CYCIAE-100注入线的模拟计算结果, 并和程序ORBIT, TRACE 3-D的结果进行比对验证, 结果表明: 空间电荷效应在此注入线上有较大的影响, 而且3个程序计算的不同中性化的结果基本上一致; 束流强度达到几十毫安时, 基于PIC方法的两个程序CYCPIC2D和ORBIT的计算结果完全吻合, 而线性近似程序TRACE 3-D有明显差异.     

Ionisierungs- und Umladequerschnitte von Wasserstoff-Atomen und Ionen von 9 bis 60 keV in Wasserstoff

This paper describes the measurement of ionization and charge exchange cross-sections for hydrogen atoms (H⁰), Protons (H⁺) and molecular hydrogen ions H ₂ ⁺ and H ₃ ⁺ in hydrogen gas in the energy range 9 to 60 keV. Further, the emission of secondary electrons from copper-beryllium by impact of these particles was measured. A beam of monoenergetic neutral hydrogen atoms was produced by charge exchange of a beam of protons in a gas chamber. Separation of the charged and uncharged components was accomplished by a magnetic field. The pressure in the chamber in which the cross-sections were measured was so low, that only a few particles of the incident beam suffered an effective collision. The positive and negative charges, which were produced by ionization and charge exchange along the path of the beam, were extracted by a transverse electric field and the saturation current was measured. The intensity of the neutral beam was determined at the same time by repeated charge exchange in an 80 mμ thick foil of aluminiumoxide.     

Simulation of Electron Cooling Proces in a Storage Ring

A simulation of electron cooling process for the heavy ion beam in the proposed HIRFL Cooler-Storage Ring(HIRFL-CSR)is performed by taking into account the betatron and synchrotron oscilations of single particle.The continuous evolution of ion beam emittances and relative momentum spread are shown.Some factors that influence the cooling speed,like the space charge effect of electron beam,the dispersion in cooler section and the electron beam transverse temperature are presented.     

储存环内电子冷却过程模拟

考虑储存环内离子的横向振荡和纵向振荡的运动特性,模拟了HIRFL-CSR内重离子束的电子冷却过程.给出了离子束的横向发射度和纵向动量散度随时间连续变化的图象,由此分析了电子束的空间电荷效应,冷却段色散函数和横向电子束温度对冷却过程快慢的影响.     

Space charge limiting current of an electron beam transported in a coaxial drift chamber

An expression for the space charge limiting current of an electron beam in a vacuum coaxial drift chamber is obtained in the strong field approximation. The expression is an analogue of the Bogdankevich-Rukhadze interpolation formula for a cylindrical drift chamber. The space charge limiting currents in the coaxial and cylindrical chambers are compared. The space charge limiting current in the vacuum coaxial chamber is numerically calculated and compared to analytical predictions.