一个90°偏转的磁分析器

前言磁分析器是用来分析含有不同动量成分的离子束,是核反应研究工作中必不可少的仪器之一。因为从加速器离子源中出来的离子束,不但成分不同,能量也不一样,质子比在最好的情况下是80%到90%,较差的只有30%左右。因而要迸行精确的研究工作,必须使带电粒子在经过磁场的偏转后得到具有单一能量、单一成分的粒子束。磁分析器的原理是基于带电粒子在磁场中的运动。当一带电粒子在磁场中运动时,它将受到一垂直于磁场及运动方向的力F:     

双等源强流离子束分析

目前所使用的各种离子源,还不能产生具有完全单一荷质比的离子,所以,离子源所提供的离子束是包含多种离子组态的混合束。因此,要把离子加速到高能,就涉及到一个多动量离子束加速系统。在由电磁场(电磁组件)构成的强流带电粒子加速系统中,多动量离子束的加速和聚焦会产生许多缺陷与困难。在强流加速器中,提高所需离子的加速效率,减轻加速器的总负荷,是一个很重要的     

利用质子静电加速器加速H_2~ 和H_3~

为满足物理实验需要,我们将质子静电加速器分析磁铁真空盒加以保护,成功地加速了H_2~ 和H_5~ 离子。束流经分析磁铁偏转聚焦后进入实验管道,通过如图1所示的装置轰击到靶上。加速H_2~ 、H_3~ 离子束时,分析磁铁出口60cm处石英屏上束流强度分别可达10μA、3.2μA,靶上流强一般被限制在几nA左右,束流能散度0.07％。     

使用背散射与二次离子质谱方法分析类金刚石厚样品中的杂质

卢瑟福背散射分析是测定薄膜或镀层成分和厚度的成熟手段,但在分析含多种微量元素成分的厚样品时,精确测定样品中多种元素的分布是比较困难的。二次离子质谱对样品表面成分有较高的质量分辨能力,可以作为对卢瑟福背散射分析的补充。在北京大学2×1.7 MV串列静电加速器终端上,结合使用这两种分析方法,分析了类金刚石厚样品中的金属元素杂质。     

多电荷双等离子体离子源

离子注入机、单级静电加速器,各类高能重离子加速器和各种利用离子束对固体等材料进行表面分析(如卢瑟福散射,沟道效应技术等)的装置中均需重离子源,特别是强流(每秒大于10~(13)粒子)多电荷重离子源对提高被加速离子的能量,实现装置的小型化具有重要意义。例如对重离子回旋加速器,被加速离子每个核子的能量直接正比于电荷数Q的平方:     

加速器-电镜联机的离子光路及其调整方案

离子辐照引起的材料微结构变化是一个复杂的过程,用加速器-电镜联机装置可原位观察载能离子束辐照引起的材料微结构演变.武汉大学加速器-电镜联机装置由1台2×1.7 MV串列加速器、1台200 kV离子注入机和1台200 kV透射电镜组成,通过自行设计的传输系统实现联机.本文介绍联机装置的光路布局,给出了静电加速器离子动力学计算程序LEADS(linear and electrostatic accelerator dynamics simulation)优化计算的结果,提出了两种改进方案,并用LEADS对改造后的加速器-电镜联机中离子运动进行了计算.结果显示,调整现光路二单元四极透镜的同时,在200 kV注入机90°偏转磁铁至电镜之间增加1个二单元静电四极透镜,将提高该系统中离子束传输效率.     

用于双离子束注入器的杂质消除系统

研制了一套用于双离子束注入器的杂质消除系统，该系统由两台速度选择器、1台单透镜和1台双孔选束光阑组成，可实现不同荷质比的两种离子束在同时传输过程中消除杂质离子。该技术已用于1台H⁺₂和He⁺两种离子束同时传输的50 keV双离子束注入器，实现了1台加速器同时产生、传输两种离子束，并同轴注入靶内，离子束纯度好于99.9%。     

加速器联机装置运行状况

2008年武汉大学加速器联机系统初步建成,200 kV离子注入机至透射电镜束线进行了运行调试,开展了气体离子注入单晶Si、GaAs、Ag纳米晶和超临界反应堆材料(C276和6XN)的原位结构研究。结果表明,样品在注入至一定剂量时发生明显多晶和非晶化,单晶Si出现非晶化的临界剂量在10~(14) cm~(-2)。C276材料经1×10~(15)cm~(-2)的Ar离子辐照后,产生尺寸3-12 nm的位错环,其密度随剂量提高而增大,至5×10~(15)cm~(-2)出现多晶,剂量超过3×10~(16) cm~(-2)出现非晶化。在加速器-电镜联机光路上安装在线RBS靶室对离子束辐照材料进行元素成分和晶格定位测试。靠近电镜端安装50 kV低能离子源,开展核材料中氦泡形成过程的原位观测。对RBS/C装置进行数字化改造,用Labview控制系统运行,目前可进行计算机控制的背散射沟道测试。     

北京大学4.5 MV静电加速器核反应分析系统

为满足对聚变堆面向等离子体材料中氘氚滞留问题的研究,北京大学4.5 MV静电加速器在原束线基础上新增核反应分析系统,该系统使用能量0.8～3.6 MeV的H~+、D~+、~3He~+和~4He~+粒子束流,可对核反应微分截面和样品中元素浓度的深度分布进行测量分析。本文对核反应分析原理、核反应分析系统的设备布局和实验方法进行了讨论,并以D(~3He,p)~4He核反应为例,分析了微分截面计算和样品中氘元素浓度深度分布的数据结果,其深度分辨小于1.5μm,实验误差约为7.5%。     

基于0.3MV小型AMS的~(129)I测量方法研究

<正>基于中国原子能科学研究院自主设计建造的端电压为0.3 MV的AMS(图1)开展了~(129)I的测量技术研究,通过离子的传输、气体剥离、电荷态选取、本底排除等方法实现了~(129)I的高效、高精度与高灵敏度测量。1粒子传输过程~(129)I-离子的传输通路通过127I-离子束流进行模拟。测量样品形式为AgI与银粉按1∶1质量比混合后压入钛锥。调整离子源参数、静电分析器电压、注入磁铁磁场后,将得到的最佳~(127)I-束流     

Hefei utility negative ions test equipment with RF source: commissioning and first results

In order to study the key technology and physics of RF driven negative ion source for neutral beam injector in China, the Hefei utility negative ions test equipment with RF source was developed at Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). Its negative ion source can be equipped with single or double RF drivers. There is a plasma expansion chamber with depth of 19 mm and an enhanced filter field. A three electrodes negative ion accelerator was employed to extract and accelerate the negative ions, which are plasma grid, extraction grid and ground grid. And there are several diagnostic tools for the plasma and beam parameters measurement. The characteristics of plasma generation, negative ion production and extraction were studied on the test equipment. The negative ion beam was extracted from the RF driven negative ion source for the first time. The detailed structure and main results are presented in this article.     

290MeV/u ~9C离子束在液态水靶中输运的蒙特卡洛模拟

9C离子束是双重辐射源于在治疗肿瘤有明显优势。我们用蒙特卡洛程序FULKA模拟了290 MeV/u 9C离子束在水靶中的输运,研究其能量沉积、核碎片分布以及核碎片注量的深度分布,可为9C离子束肿瘤治疗剂量学提供参考。     

Gas flow and related beam losses in the ITER neutral beam injector

The gas flow in the ITER neutral beam injectors has been studied using a 3D Monte Carlo code to define a number of key parameters affecting the design and operation of the injector. This paper presents the results of calculations of the gas density in the two accelerator concepts presently considered as options for the ITER injectors, and the resultant stripping losses of the negative ions during their acceleration to 1 MeV. The sensitivity of the model to various parameters has been studied, including the gas temperature in the ion source and the subsequent accommodation by collisions with the accelerator structure, and the degree of dissociation of the D₂ or H₂ in the ion source, and subsequent recombination during collisions with the accelerator structure. Additionally the sensitivity of the losses to details of the beam source design and operating parameters are examined for both accelerator concepts.     

Progress of the RF negative hydrogen ion source for fusion at HUST

Huazhong University of Science and Technology has developed an experimental setup of a radio frequency (RF) driven negative hydrogen ion source, to investigate the physics of production and extraction of the H− ions for neutral beam injection in nuclear fusion reactors. The main design parameters of the ion source are: RF power ≤40 kW; extraction voltage ≤10 kV; accelerator voltage ≤20 kV. This paper gives an overview of the progress of the ion source with particular emphasis on some issues. The RF driver and source plasma are analyzed and optimized in terms of impedance matching, plasma characteristics and power coupling. In regard to the simulation analysis, a plasma model based on the particle-in-cell method and a beam trajectory model considering beam stripping loss are developed to investigate the plasma and negative ions transport inside the ion source. Furthermore, a collisional radiative model of H and H2 is built for plasma optical diagnosis.     

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。     

Creation of microstructures using heavy ion beam lithography

In this work, three-dimensional (3D) structures were produced in PMMA and CR-39 polymer resists using a carbon ion microbeam. To investigate possible advantages of heavy ions compared to the well-established proton beam lithography, the same resist materials were also irradiated with protons that had a range in the materials studied here similar to that of carbon ions. The microstructures produced in different resists were analysed after chemical etching. The quality of the bottom and side walls of the structures produced by protons and carbon ions were compared using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed that, for the resist materials tested, lithographic structures made with the 8 MeV carbon beam had more rough lateral and bottom surfaces compared to those made with 0.6 MeV proton beam lithography.     

袖珍永磁端引出PIG离子源

介绍了一个袖珍永磁端引出ＰＩＧ离子源，它可用于产生各种气体的单电荷和多电荷离子，在不大于３０Ｗ的放电功率下，可引出ｍＡ级离子流，源的阴极寿命大于２００ｈ。     

Modification of an Ion Source for the Production of Microampere 4He- Beams

Several modifications of the ion source of a model EN Tandem Van de Graaff Accelerator have increased the production of 4He- beams by a factor of 100 over that first obtained with the source (~10 nA). While using H2 gas for charge exchange, the replacement of the source drift tube by a screen and the installation of a system for precise adjustment of the button alignment with respect to the extractor electrode increased the output to 150 nA at the ion source. Recently potassium vapor has been used for charge exchange. Since the introduction of this technique, 4He- beam currents of 1. 2 ?A have been regularly produced. The 4He+ ions from a duoplasmatron ion source are accelerated to 20 keV and passed through the standard exchange canal which is modified by the addition of a potassium vapor chamber. Analyzed 4He++ beams of 0.3 to 0.8 ?A have been obtained with terminal voltage between 1.8 and 6 MV. The modified source has been used with K-vapor exchange for continuous periods of up to 120 hours without deterioration of source performance. Normal operation with H2 gas exchange for other beams is possible without the interruption of the source operation.     

用于EBIT装置的小型MEVVA源及其离子注入实验

为给上海电子束离子阱(Electron Beam Ion Traps,EBIT)装置提供低电荷离子,我们研制了小型金属蒸汽真空弧(Metal Vapor Vacuum Arc,MEVVA)离子源,可产生多种金属以及半导体材料的低电荷离子.本文介绍小型MEVVA离子源的特性及其在上海EBIT装置上的离子注入实验.实验结果显示,合理控制注入参数可以使注入并被束缚在EBIT中的离子数密度达到108～109/cm3.     

脉冲离子束流聚焦装置的研制

用小型化的质量分析系统进行脉冲离子束流实验研究时,从真空弧离子源中引出的束流脉冲幅度大、能量低,由于空间电荷效应使脉冲束流发散度很大,使得离子束流成分分析的不确定度增大。为克服在有限的空间范围内脉冲离子束流聚焦的困难,研制了一种新的双限束光阑三膜片透镜离子束流聚焦装置。双限束光阑着重减少束流发射度,三膜片透镜则适合小尺度空间的脉冲束流聚焦。计算机模拟的结果符合这种大脉冲离子束流聚焦的设计思想。磁质谱仪应用该聚焦装置后,发散到质量分析器分析盒上的脉冲离子束流幅值从未加聚焦前的115 mA减少至0.06 mA,脉冲离子束流质量分析的不确定度降低。