RF离子源引出特性的研究

为了使RF离子源具有良好的引出特性, 测试了吸极几何参数、振荡器板压、引出电压对离子源引出特性的影响, 对实验结果进行了分析. 在其他参数不变的情况下, 存在最佳的D/d; 增加D/d,有利于过聚焦的离子束恢复聚焦状态. b/D增大时, 聚焦度上升, 引出束流下降. B/d减小时,聚焦度增大; 当B/d小于4时, 聚焦度增加趋势变缓. 综合考虑聚焦度、引出束流和气压,D/d,b/D,B/d适宜的选择范围分别为1.6—2.1, 0.7—1.1, 4—7. 改变引出电压和振荡器功率对离子源性能的影响具有相反的方向, 两者都存在最佳工作点.     

HL-2A装置中性束离子源引出系统束流分析

在中性束离子源引出过程中,详细分析了引出束流的产生,这有利于得到更准确的引出功率和引出电极表面的热功率沉积情况。根据HL-2A装置中性束离子源引出电极的电连接方式和束流引出的物理过程,对离子源束流引出过程进行了分析,给出抑制极电流产生的主要来源。通过分析放电气压扫描实验中的结果发现:随着放电气压的增加,不同弧放电电流情况下抑制极电流均逐渐增加,且抑制极电流与引出电流的比值近似线性增加。针对引出离子束流经过引出电极的过程建立了物理模型。计算了抑制极电流与引出电流的比值与放电气压的依赖关系,计算结果与实验结果一致,验证了引出束流分析结果的合理性。     

用于静电加速器的高频离子源及其引出特性

 根据离子束生物工程的需要,设计和研制了一台用于静电加速器的小型高频离子源。针对使用环境从理论上确定了离子源的结构和尺寸。通过实验调试取得了引出束流与引出电压、聚焦电压以及放电气压之间的变化特性曲线,测定了引出束流的束径包络,对束流的不稳定性进行了分析,在设计中采取了有效的措施抑制束流不稳定性。结果表明,离子源的最佳工作条件为引出电压1 600V~1 800V,放电气压在（4~8）×10^-4Pa范围,此时离子源可引出最大束流30μA。束流大小及其稳定性均达到预期要求。     

ECR离子源中的微波功率在线测量

 在中子发生器中采用ECR离子源是一种新技术。由于受结构的限制，ECR离子源不能像高频源离子源那样通过观察气体放电的颜色判断其工作状态，所以在运行中调节状态非常困难。解决这个问题的方法是：用定向耦合器加微波小功率计的方法在线测量ECR离子源的微波入射功率，通过微波入射功率可以直接得到ECR离子源引出离子束流的大小，从而推断微波信号源的放电过程是否正常,然后调整ECR离子源，最终使中子发生器工作在最佳状态。从ECR离子源后面的引出电极测得的最大束流为20 mA，且工作长时间稳定，当微波功率在160 W~500 W之间时，放电效果较好，离子束流随微波功率的增加而增加。     

用于NPA标定系统的高频离子源研制

研制了一台用于Neutral Particle Analyzer(NPA)标定系统的高频离子源,对其性能参数进行了实验测量,得到引出束流与高频振荡器板压、引出电压及放电气压之间的特性曲线,对影响引出束流稳定性的原因进行了分析.结果表明:当工作气体为氢气,在板压580 V、引出电压1600 V、聚焦电压1550 V和气压9.5×10~(-4) Pa时,能引出66μA的离子流;在41μA束流条件下,4小时内的束流稳定性优于2.6%,影响束流稳定性的主要因素是放电管内工作气体气压的波动和等离子体温度的升高.此结果可以满足HL-2A/M上NPA系统的标定对离子源的要求.     

射频离子源离子束成分光谱测量

为HL-2A 装置中性束注入器研制了引出束功率为1MW 的射频离子源。在测试平台上，实验离子源已经成功引出了束能量和束电流分别为35keV 和12.4A、束质子比为79%、脉宽为100ms 的氢离子束，达到了设计束功率要求的44%。在射频离子源实验平台上，利用多普勒频移光谱方法测量了离子源引出束流成分比例，对比了束流成分和射频离子源引出束流之间的关系。实验数据分析表明，在10A 引出束流的情况下，离子流成分 H⁺ ₁、H⁺ ₂ 和H⁺ ₃ 分别为75%、18%和7%。并且当引出束流从3.3A 升至10.4A 时，H⁺ ₁ 从37%升至78%，而H⁺ ₃ 则从19%降至9%。     

ECR源低能强流高电荷态离子束四维发射度测量仪的研制

为全面研究ECR（Electron Cyclotron Resonance）离子源引出的高电荷态离子束流品质，获取ECR离子源引出离子束流的横向四维相空间分布，提高向加速器的注入效率，中国科学院近代物理研究所研制了一台高精度Pepper Pot型发射度测量仪PEMiL（Pepper pot Emittance Meter in Lanzhou）。根据使用需求，利用KBr晶体喷涂技术取代传统的CsI闪烁体成像技术，解决了束流光斑重叠效应，获得了边界清晰的束流图像；并开发了相应的数据处理分析程序，以分析处理得到的束流横向四维相空间分布。利用PEMiL获得了75 keV，170 eμA的O5+束流横向四维发射度。分析结果表明:PEMiL测量分析后的束流发射度结果可靠性高，荧光屏电荷累积效应造成的发射度差异不超过25%，PEMiL可作为ECR离子源引出离子束流品质诊断的有效装置。     

材料表面处理用强流电子回旋共振离子源

介绍一台2.45 GHz永磁强流电子回旋共振离子源,其外径160mm,高90 mm,放电室直径70 mm,高50 mm。微波馈入采用介质耦合方式,微波窗由一块f50 mm10 mm柱形BN和两块f30 mm10 mm的柱形陶瓷构成。离子源工作在脉冲模式下,采用三电极引出系统,最高引出电压达到100 kV,在微波输入功率300 W、进气量0.4 mL/min时,可引出峰值超过30 mA的氮离子束,在距离离子源引出孔1200 mm位置处的束流均匀区直径大于200 mm。     

射频离子源离子束成分光谱测量

为HL-2A装置中性束注入器研制了引出束功率为1MW的射频离子源。在测试平台上,实验离子源已经成功引出了束能量和束电流分别为35ke V和12.4A、束质子比为79%、脉宽为100ms的氢离子束,达到了设计束功率要求的44%。在射频离子源实验平台上,利用多普勒频移光谱方法测量了离子源引出束流成分比例,对比了束流成分和射频离子源引出束流之间的关系。实验数据分析表明,在10A引出束流的情况下,离子流成分H+1、H+2和H+3分别为75%、18%和7%。并且当引出束流从3.3A升至10.4A时,H+1从37%升至78%,而H+3则从19%降至9%。     

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为提高NBI系统的稳定运行参数和可靠性,研制了一台基于高频开关电源技术的全固态调制输出负高压测试电源,并将HL-2A装置NBI系统原4套抑制极电源的电子管调制器改为基于IGBT串联技术的全固态调制器.对比原抑制极电源系统,给出了基于高频开关技术和IGBT串联技术的抑制极电源结构.结合NBI系统调试实验,通过调节抑制极电源电压,瞬态电流输出能力,分析了抑制极电源输出性能对离子源束流引出特性,离子源引出电极击穿特性的影响,获得了引出稳定离子束流的最低抑制电压.     

Optimization of Extraction System for Cold Cathode Ion Source

We have simulated ion trajectories with the SIMION 3D, version 7.0, package to optimize the extraction system of a cold-cathode ion source and compared the results with experimental data collected under the same operational conditions. The simulation determined the negative voltage applied to the extractor electrode and the extraction gap widths that maximize the ion-beam current for singly charged nitrogen ions with low emittance and small diameter. The experiment measured the input electrical discharge and output ion beam characteristics of the source at different nitrogen pressures. The extractor electrode voltage and the extraction gap width were determined at 8?×?10^?4?Torr nitrogen. The results of the simulation agreed well with the experimental data.     

Analytical and simulation studies for diode and triode ion beam extraction systems

This work is concerned with ion beam dynamics and compares the emittance to aberration ratios of two-and three-electrode extraction systems. The study is conducted with the aid of Version 7 of SIMION 3D ray-tracing software. The beam dependence on various parameters of the extraction systems is studied and the numerical results lead to qualitative conclusions.     

强流ECR离子源引出系统研究

为了提高强流ECR 离子源的引出束流品质,分别设计了1# 和2# 引出系统,利用束流引出模拟软件PBGUNS 对1# 和2# 引出系统进行了质子束流引出与传输的模拟计算,结合实际测得的发射度数据分析引出系统,发现2# 引出系统比1# 引出系统引出束流品质高。对ECR 离子源引出系统的电势等位线分布等参数引起的球差进行了简单数学推导及MATLAB 绘图,并结合1# 和2# 引出系统束流相图模拟结果证明了球差会使引出束流品质有效发射度增长,通过适当加大电极孔径可改善束流聚焦情况,得到了束流光学聚焦较好的束流引出系统设计。To improve the quality of extracted ion beam from a high current ECR ion source, 1# and 2# extraction systems were designed and tested. The PBGUNS code was used to simulate the 1# and 2# extraction systems of proton ion beam. The emittance measurement results with the two different extraction systems were compared and analyzed with the simulation, the conclusion that more high quality beam extracted from 2# system than 1# system was got. The formula derivation of ECR ion source extraction system spherical aberration and MATLAB drawing was done by the analyzing on the distribution of extraction field equipotentials, effective emittance increasing caused by spherical berration was proved by 1# and 2# extraction systems beam phase space simulation result, beam focusing would be improved if electrode hole size increasing appropriately and a general concept on good optics focusing of ion beam extraction system was proposed finally.     

HL-2M装置中性束离子源束光学红外成像实验研究

为了研究HL-2M装置中性束注入(NBI)加热用的80kV/45A/5s热阴极离子源束光学特性，采用红外电荷耦合元件(CCD)成像技术，测量离子源引出粒子束轰击量热靶板产生的温度分布，得到束功率密度空间分布区间特征参数1/e半宽度。在NBI热阴极离子源调试平台上，扫描离子源的放电和引出参数，利用CCD红外热像仪获得了对应参数下量热靶上的束功率密度分布。实验结果表明，HL-2M装置NBI加热系统80kV/45A离子源可用的导流系数范围为0.7~1.5μP。同样导流系数下，梯度电极与等离子体电极的分压比较高时，引出束流的半宽度较小。     

Feasibility study on high current ion beam extraction from anode spot plasma for large area ion implantation

In this paper, we have investigated the feasibility of the high current beam extraction from anode spot plasma as an ion source for large area ion implantation. Experiments have been carried out with the ambient plasma produced by inductive coupling with radio-frequency (RF) power of 200 W at the frequency of 13.56 MHz. Anode spot plasmas are generated near the extraction hole of 2 mm in diameter at the center of a bias electrode whose area exposed to the ambient plasma can be changed. It is found that the maximum ion beam current is extracted at the optimum operating pressure at which the area of bias electrode exposed to ambient plasma is fully covered with the anode spot plasma whose size is dominantly determined by the operating pressure for given gas species. It is also observed that the extracted ion beam current increases nonlinearly with the bias power due to the changes in size and shape of the anode spot plasma. With the well-established anode spot plasma operating at the optimum gas pressure, we have successfully extracted high current ion beam of 6.4 mA (204 mA/cm²) at the bias power of 22 W (∼10% of RF power), which is 43 times larger than that extracted from the plasma without anode spot. Based on the experimental results, criteria for electrode design and operating pressure for ion beam extraction from larger extraction aperture are suggested. In addition, the stability of anode spot plasma in the presence of ion beam extraction through an extraction hole is discussed in terms of the particle balance model.     

等离子体离子源发射面的理论计算与数值模拟

 等离子体离子源发射面的位置和形状决定了离子束的传输特性，而发射面的位置与形状又取决于等离子体参数、引出电压、电极结构等，并自动地调节到某个平衡状态。介绍了一种2维情况下等离子体离子源发射面的位置与形状的理论计算方法，即非磁化等离子体不能扩散进入外加电场中大于一定临界值的区域，等离子体离子源发射面的位置及形状可以通过直接求解引出系统的Laplace方程而得到。利用基于PIC的OOPIC程序对不同引出结构的发射面位置及形状和引出束流进行了数值模拟，结果与理论计算的结果十分接近。     

Numerical simulation and design of a thermionic electron gun

This paper reports the simulation of an electron gun. The effects on the beam quality of some parameters on the beam quality were studied and optimal choices were identified. It gives numerical beam qualities for a common electrostatic triode gun, and the dependencies on design parameters such as electrode geometries and bias voltages to these electrodes are shown. An electron beam of diameter 5 mm with energy of 5 ke V was assumed for the simulation process. Some design parameters were identified as variable parameters in the presence of space charge.These parameters are the inclination angle of emission electrode, the applied voltage to the focusing electrode, the gap width between the emission electrode and the focusing electrode and the diameter of the focusing electrode. The triode extraction system is designed and optimized by using CST software(for Particle Beam Simulations). The physical design of the extraction system is given in this paper. From the simulation results, it is concluded that the inclination angle of the emission electrode is optimized at 22.5?, the applied voltage to the focusing electrode was optimized and found to be Vfoc =-600 V, the optimal separation distance(gap between emission electrode and focusing electrode) is 4 mm, and the optimal diameter of the emission electrode is 14 mm. Initial results for these efforts aimed at emittance improvement are also given.     

High current density ion-beam extraction

High current density (up to 700 mA/cm²) ion-beam extraction has been studied by 3D code KOBRA3-INP [INP, Junkerstr. 99, 65205 Wiesbaden, Germany]. Ion beams with such high current densities can be generated by ECR ion source driven by 37.5 GHz/100 kW gyrotron [Golubev S.V. et al. Trans. Furion Sci. Technol., 47, n. 1T, fuste 8, 345]. The influence of plasma parameters on extracted ion beam has been investigated. Different geometries of extraction system and applied potentials have been simulated to optimize extracted and transported ion beam current. KOBRA3-INP code has been applied to simulate ion-beam transport as well. The results of simulations have been compared with experimental results. Good agreement between measurements and simulations was always found by varying ion-beam space-charge compensation degree.     

4 MV静电加速器调试中出现的问题及解决方案

 4 MV静电加速器由高压系统、离子源及束流系统、控制系统和气体系统四部分组成。调试中出现了离子源不起弧、加速管破裂、控制系统失灵和输电带输电能力降低等技术问题，分析了出现这些问题的原因，然后分别采取了相应的措施加以解决：变换工作流程，在每次关机前先把引出电压降为零，开机时等离子源起弧后再把引出电压升到预定值；对过渡法兰进行车加工，重新封装；对高压端的控制设备采取屏蔽措施，在输入、输出端使用TVS二极管，对控制软件进行抗干扰设计；对绝缘气体进行循环干燥等。调试出了流强为100 μA、能量在3 MeV以上的稳定质子流。