Optimizing the geometry of a negative ion sputter source

In order to avoid isotope fractionating effects due to slight fluctuations in the position, direction or divergence of the emerging beam, the emittance of an AMS ion source has to be lower than the acceptance of the following beam handling system. The emittance of a negative ion sputter source is determined by the energy spread of the sputtered ions and by its extraction geometry. For various configurations of the latter, we have calculated particle trajectories. Greatly reduced aberrations are attained if the electric field close to the emitting surface is nearly uniform and only weakly focussing and if the acceleration takes place in at least two lens sections. The single acceleration gap of our Hortig-type ion source [1] has therefore been replaced by a two-stage accelerating lens. Further, the curvature of the field at the surface of the sputter target is controlled by an additional electrode.     

400 kV强流中子发生器的物理设计

对400 kV强流中子发生器进行了物理设计。采用Poisson/Superfish软件对中子发生器高压电极和加速管的电场分布进行了模拟,结果显示,各关键区域的空间电场最大值远低于击穿电场限值。以强流束旁轴包络方程为基本模型,发展了强流束传输系统束包络的计算机模拟程序IONB1.0,模拟了中子发生器传输系统中40 mA的D束流包络。结果显示,设计方案中所采取的两间隙高梯度加速结构有较强的聚焦性能,能有效抵消强流束空间电荷效应造成的束流发散,加速管出口处的束包络半径约3 cm,由加速管出口处的空间电荷透镜和三重四极磁透镜组成的传输系统能将束流聚焦在约140 cm处的靶上,且束斑直径小于2 cm。     

微波离子枪离子束光学的数值模拟

用数值模拟方法研究了聚焦离子束系统中微波离子枪的束光学性能，将离子枪看作由源等离子体极和Ｏｒｌｏｆｆ－Ｓｗａｎｓｏｎ透镜组成的双级加速系统，分析了各参对束发射特性的影响。结果展示出引出束光学主要取决于引出导流系数和电势分布，在一定条件下可获得发散度小的离子束。     

尼尔逊离子源重离子束流的发射度

尼尔逊离子源已广泛地应用于重离子加速器、同位素分离器及研究用离子注入机。用于C-600离子注入机的尼尔逊离子源,目前已获得达100μA的三十余种重离子束,其中有近二十种固体元素。     

Cu and Y ion beams by a new LIS generator

In this work, we present the experimental results of a laser ion source (LIS) implemented for ion accelerators. A KrF excimer laser beam operating at 248 nm was focused on a solid target mounted inside a vacuum chamber in order to obtain the plasma. The laser energy was fixed at 11.5 mJ/pulse. The ion components of the plasma were extracted and accelerated up to 160 keV per charge state by a double gap system formed in two different stages. The beam cross section was circular, 1.5 cm in diameter. Using Cu and Y disks, as laser targets, we produced ion beams containing 1.2 × 10¹¹ ions/pulse (0.7 × 10¹¹ ions/cm²). Applying a total accelerating voltage of 60 kV we obtained an increase in ion dose up to 3.4 × 10¹¹ ions/pulse, (2 × 10¹¹ ions/cm²) for the Cu target and up to 6.3 × 10¹¹ ions/pulse (3.5 × 10¹¹ ions/cm²) for the Y target. The characterization of the plasma was performed using a Faraday cup for the electromagnetic properties, and a pepper pot system for the geometric ones. At 60 kV accelerating voltage and 5.5 mA output current the normalized beam emittance resulted in 0.22 π mm mrad for the Cu target, while under the same accelerating voltage, but with 7.4 mA output current, the normalized beam emittance resulted in 0.14 π mm mrad for the Y target.     

The effects of beam line pressure on the beam quality of an electron cyclotron resonance ion source

The results of a series of measurements studying the possibility to use neutral gas feeding into the beam line as a way to improve the quality of the heavy ion beams produced with an electron cyclotron resonance ion source (ECRIS) are presented. Significant reduction of the beam spot size and emittance can be achieved with this method. The observed effects are presumably due to increased space charge compensation degree of the ion beam in the beam line section between the ion source and the analyzing magnet. This is the region where the neutral gas was injected. It is shown that the effects are independent of the ion source tuning. Transmission measurements through the beam line and K-130 cyclotron have been carried out to study the effects of improved ion beam quality to the transmission efficiency.     

FEL中的束流发射度分析

根据自由电子激光器(FEL)对电子束流品质的要求,对束流发射度以及引起束流发射度变化的因素,诸如加速过程中微波场的突变、能量增加、波导结构的尾场效应和传输过程中的空间电荷效应、粒子密度分布的影响及偏转系统中的尾场效应等等,进行了物理上的分析,对其中某些情况,给出了束流发射度变化量的具体估算。     

束流发射度和亮度与束流密度分布的关系

束流发射率和束流亮度是表征加速器束流品质的主要指标。理论和实验研究都已发现,它们与束流空间电荷的非均匀分布有密切关系。     

金属真空弧离子源引出强流离子束的数值模拟

为了引出更高强度、更高亮度的铀离子束,以满足重离子研究中心(Gesellschaft für SchwerionenforschungmbH,GSI)重离子同步加速器的需求,本文用三维的计算机程序KOBRA3-INP对金属真空弧离子源(Metalvapor vacuum arcion source,MEVVA)引出强流铀离子束在引出系统和后加速系统中的动力学特性进行了研究,讨论了离子源发射束流密度对引出束性能的影响.结果表明,束流损失主要发生在引出系统和后加速系统之间的漂移区;在假设漂移区束流被空间电荷中和的情况下,模拟结果和实验结果符合;在发射束流密度为180-230 mA/cm2范围内,经后加速的束流强度变化不大.     

Accelerating Trajectory Simulation With COMA for CYCIAE-100

With multi-particle tracking code COMA, the process of accelerating for CYCIAE-100 is simulated and the beam dynamics such as the energy spread, phase slip, emittance, envelope etc. of the beam with the acceleration are studied in detail.     

A low-cost, accurate and non-intercepting continuous method for beam current measurements in a high-current ion implanter

The development of a low-cost, accurate, non-intercepting continuous method for measuring the beam current in a high-current ion implanter is described. The method, named a differential current monitor, is based on the electric charge conservation principle, applied to the currents that flow in the implanter electrical system, due to the acceleration voltage applied to the ion beam and the leakage currents to ground. This method allows for continuous measurement of the ion beam current without intercepting it. Since its installation, it is possible to accurate measure ion beam currents from tens of μA to mA, which is the normal range for this type of system.     

Transport characteristics of space charge-dominated multi-species deuterium beam in electrostatic low-energy beam line

The transport characteristics of a space chargedominated multi-species deuterium beam consisting of D_1~+,D_2~+, and D_3~+ particles in an electrostatic low-energy beam line are studied. First, the envelope equations of the primary D_1~+ beam are derived considering the space charge effects caused by all particles. Second, the evolution of the envelope of the multi-species deuterium beam is simulated using the PIC code TRACK, with the results showing a significant effect of the unwanted beam on the transport of the primary beam. Finally, different injected beam parameters are used to study beam matching, and a new beam extraction system for the existing duoplasmatron source is designed to obtain the ideal injected beam parameters that allow a D_1~+ beam of up to 50 m A to pass unobstructed through the electrostatic low-energy beam transport line in the presence of an unwanted(D_2~+, D_3~+)beam of 20 m A; at the same time, distortions of the beam emittance and particle distributions are observed.     

缝丝法强流离子束发射度测量中系统误差的模拟研究

本文分析了缝丝法测量强流离子束发射度时系统误差的主要来源,并用模拟计算的方法研究了不同误差来源所带来的误差大小。对于rms发射度测量,因缝采样、忽略缝宽和丝直径、以及空间电荷效应所引起的系统误差均可忽视,而短缝采样和设置较大的阈值则会引起显著的系统误差。     

Nonneutral Plasma Science Issues for Heavy Ion Drivers

A review of nonneutral plasma science issues for heavy ion drivers is presented. The requirements on transverse and longitudinal focusing at the target lead to constraints on the 6D phase space. Mechanisms which act to prevent focusability, including emittance growth, space charge and instabilities are discussed. Experiments which have explored and validated our understanding of beam transport and focusability of space-charge dominated heavy ion beams are described.     

高梯度加速管的束流传输

对不同能量、不同质量数、不同初始条件的入射束和有无空间电荷效应的离子束流在高梯度加速管中的传输进行了计算，并讨论了一些影响加速管聚焦作用的主要因素，计算结果与实际情况相符。     

强流氘束引出系统与加速管束流匹配的研究

为增加传输通过加速管的束流强度,提高中子发生器的中子产额,采用Particle-in-cell(PIC)程序模拟研究了入射束强度在10～150 mA范围内,不同初始参数条件下D⁺₁束在加速管中的传输状态。结果表明,当入射束在加速管入口处的归一化发射度取0.25 πcm•mrad,Courant-Snyder参数α=-4、β=60 cm/rad时,50～100 mA D⁺₁束与加速管匹配良好。根据匹配参数,对双等离子体离子源的引出系统进行了优化,结果显示,在引出系统与加速管之间放置两个螺线管透镜和1个光阑,能有效去除D⁺₂、D⁺₃离子,实现100 mA D⁺₁束顺利传输通过加速管的目的。     

EAST强流离子源电源系统的初步测试运行

测试NBI大功率强流离子源的综合测试台正在建设,已研制了离子源等离子体发生器电源系统、等离子体电极高压电源及梯度极分压器、抑制极负高压电源等电源系统,以及高压传输线及缓冲器,在测试台上开展了对EAST中性束注入器第一台兆瓦级强流离子源样机进行整体电源系统测试和离子源起弧放电的初步测试,完成了离子源电源系统初步性能测试及...     

用三梯度法测量束流发射度的研究

准确测量发射度对加速器束流的调制和性能的评估极端重要，本文介绍在HIRFL(兰州重离子加速器)现有设备基础上，利用三梯度法测量束流发射度的系统，讨论了测量原理和方法，以及测量中要注意的问题．并对数据的计算处理做了详述。专门设计了一套软件系统，以实现束流发射度、束流剖面等束流参数的实时测量。该系统具有可靠性好、测量直观、测量较准确等优点。