Measurement of Ion Cyclotron Emissions by Using High-Frequency Magnetic Probes in the LHD

Two pairs of high-frequency magnetic probes were installed in the Large Helical Device (LHD). During the injection of a perpendicular neutral beam, ion cyclotron emissions (ICEs) with the fundamental frequency corresponding to the ion cyclotron frequency at the plasma edge were detected, which are the same type of ICE as measured with the former spare ion cyclotron range of frequencies (ICRF) heating antennas. This type of ICE was further investigated with regard to the phase and intensity of signals. Another type of ICE was found in the LHD, and these ICEs were synchronized with bursts of toroidicity induced Alfv¶en eigenmodes (TAE) and the rise of intensity of lost ion °ux. Therefore the source of these ICEs was thought to be the particles transferred from the core to the outer region of plasma by the TAE bursts. The frequency of ICEs induced by the TAE bursts increases linearly with the magnetic ¯eld strength, since the ion cyclotron frequency increases with the magnetic ¯eld strength.     

串列加速器358型双等离子体离子源改进及性能研究

为提高北京师范大学GIC4117型串列加速器358型双等离子体离子源束流强度及灯丝使用寿命,改进了离子源灯丝涂覆材料中Ba、Sr、Ca元素的占比、灯丝涂覆方法及离子源保护措施。讨论了在不同灯丝电流下,进气量、弧流、约束磁铁电流对离子源输出束流强度的影响。灯丝累积使用寿命达到200 h以上,靶室束流强度较原来采用860A溅射源提高约500倍。同时本文对358型双等离子体离子源调试过程中的异常断弧情况进行了分析和改进。     

强流负氢离子源发射度测量仪研制

在加速器技术研究中,束流发射度是反映束流品质的重要物理参数,也是加速器和束流传输线设计的重要依据。100 MeV回旋加速器采用18 mA强流负氢离子源来产生负氢束,为了准确测量离子源的发射度,研制了一台强流负氢离子源发射度测量仪,介绍了其基本原理、机械设计和实验结果,得到了离子源的发射度信息,为100 MeV回旋加速器的设计提供了发射度参数。     

Calculation of Beam Intensity Distribution for the Neutral Beam Injection in EAST

Theoretical beam intensity distribution is derived for the neutral-beam-injection ion source with a multi-slot extraction in EAST. The beam intensity profile, b...     

强流双潘宁离子源弧特性研究

针对22cm双潘宁离子源,研究了其弧流与放电调节参数的关系以及二次进气的效果,确定了拉长弧流脉宽、提高弧流强度与稳定性、达成离子源合适工作状态的措施,为获得高品质的弧流提供了依据.离子源弧特性测试研究结果对提高强流离子源的工作性能以实现NBI系统强流准稳态运行有重要的指导意义.     

支持气体对弧放电离子源的有益作用

在弧放电等离子体离子源中,用支持气体改善离子源的工作已有三十年的历史。美国ORNL在Calutron源中引进N_2或惰性气体。1973年Freeman提出,蒸汽未放电时,先用惰性气体帮助放电,直到蒸汽能建立放电时就停止供气。1977年Hudson等报道了用支持气体提高Ne~(6 )流强。但是,支持气体在弧放电离子源中的作用,至今尚未深入研究,     

CSNS强流负氢离子源及其改进

中国散裂中子源（CSNS）的离子源是1台强流负氢离子源,该离子源负氢束流的能量为50 keV,负氢流强可达40 mA,束流占空比最高为1.25%（重复频率为25 Hz,脉宽为500 μs）。目前该负氢离子源已投入到CSNS中使用。由于等离子体放电电极受带电粒子溅射的缘故,在1.5%（25 Hz,600 μs）的占空比、负氢流强30 mA运行下,离子源的寿命约为30 d。为提高离子源使用的稳定性,对离子源进行改进优化,提高了离子源的运行效率和稳定性。     

碳团簇及C60负离子的产生

利有铯负离子溅射源和石墨阴极产生并引出了碳团簇负离子流，观察到了一些电子亲和势很小的团簇，用Ｃ６０／Ｃ７０混合物做阴极，也引出了Ｃ６０及其碎片的负离子束，分析了碳团簇负离子束流的质谱组成特点和束流变化的一些规律。     

双频加热的LECR3离子源设计及初步的调试

研制成功了一台新的ECR（Electron Cyclotron Resonance）离子源LECR3（Lanzhou ECR No.3）。该离子源能为原子核物理与表面物理研究提供高电荷态离子束流，LECR3的设计主要基于IMP（Institute of Modern Physics）的14.5GHz ECR离子源（Lanzhou ECR No.2），但采用了双频加热、波导直接馈入微波功率及铝制等离子体弧腔等新技术和新方法。另外，LECR3的弧腔容积比LECR2的大，增加可注入的微波功率，可有效地增加引出的高电荷态离子束流的强度。虽然增大了弧腔的内么，但仍然保持径向六极磁铁在弧腔内壁上产生最大磁场强度与LECR2的同样大小。     

Modeling of magnetized collisional plasma sheath with nonextensive electron distribution and ionization source

The properties of an atmospheric-pressure collisional plasma sheath with nonextensively distributed electrons and hypothetical ionization source terms are studied in this work. The Bohm criterion for the magnetized plasma is extended in the presence of an ion–neutral collisional force and ionization source. The effects of electron nonextensive distribution, ionization frequency, ion– neutral collision, magnetic field angle and ion temperature on the Bohm criterion of the plasma sheath are numerically analyzed. The fluid equations are solved numerically in the plasma–wall transition region using a modified Bohm criterion as the boundary condition. The plasma sheath properties such as charged particle density, floating sheath potential and thickness are thoroughly investigated under different kinds of ion source terms, contributions of collisions, and magnetic fields. The results show that the effect of the ion source term on the properties of atmosphericpressure collisional plasma sheath is significant. As the ionization frequency increases, the Mach number of the Bohm criterion decreases and the range of possible values narrows. When the ion source is considered, the space charge density increases, the sheath potential drops more rapidly, and the sheath thickness becomes narrower. In addition, ion–neutral collision, magnetic field angle and ion temperature also significantly affect the sheath potential profile and sheath thickness.     

用于溅射负离子源的透射表面电离器的研制

介绍了１种应用于表面电离型溅负离子源的球面形透射表面的电离器，并阐述了原理。这种电离器可使铯蒸气直接通过，避免了铯蒸气绕射造成电离表面铯原子通量低的缺点，增大了铯离子的产额也使离子源的流强较采用非透射型电离器时提高了５０－８７％。‘     

用于蓝姆移动型极化离子源的低能强流双等源

建立了用于蓝姆移动型极化离子源的双等源和低能引出聚焦系统，实验比较了等离子体出口孔径和聚焦电极之间的距离对引出束的影响，并调整了离子源的运行参数。离子束的质子比可达６０％以上，满足了极化离子源的工作要求。约有４ｍＡ低能氢离子束（５５０ｅＶ）或氘离子束（１１００ｅＶ）进入铯蒸汽电荷交换管道，在极化源上使用低能强流双等源后，可获得２００ｎＡ左右的极化质子（或氘核）束。     

Trapping of Free Electrons in Multipole System

In this paper, the effective Parameters in the confinement and trapping of fast electrons in plasma source Such as; plasma pressure, wall material of plasma chamber and magnetic mirror rate have been investigated with using Comsol & Geant4 code. The calculations are shown that the Multicusp magnetic field was effective the pressure less than 5?mTor, and the confinement effect becomes stronger with decreasing pressure. It is equivalent to a higher yield of output ions of plasma source. The number of fast electrons trapped in the magnetic field increases with increasing magnetic field intensity and using aluminum for wall material. Optimum conditions of confinement plasma, leading to increased the hot electron density, and ionization efficiency is increased. The results of investigations have demonstrated good correspondence with theoretical calculations, therefore there is the adequacy of the developed approach and the possibility to build more effective source ion on this basis.     

Status and future development of ion sources for on-line mass separators

The status is given of ion sources for on-line mass separators with examples of recent developments on element availability, ionization efficiency, speed and selectivity. Since the target and the ion source are most often integrated, a discussion is included of the progress in the most important methods used to bring the nuclear reaction products out of the target and into the active region of the source. A number of novel, more advanced target and ion source systems have recently emerged and may in the future offer new possibilities for existing machines. Selected examples will be given for: (1) new release and delay studies, (2) selective resonant laser ionization, (3) electron cyclotron resonance (ECR) ion sources, (4) chemical reactions inside the ion source, (5) ion sources with bunched beam release. In view of the planned new facilities with post-acceleration of radioactive ion beams or on-line to high intensity low repitition rate accelerators, a number of future requirements of the ion sources are discussed.     

New production systems at ISOLDE

New target systems for the ISOLDE on-line mass separator facility are presented. Targets of carbides, metal/graphite mixtures, foils of refractory metals, molten metals and oxides have been tested. Beams of high intensity of neutron-rich isotopes of a large number of elements are obtained from a uranium carbide target with a hot plasma-discharge ion source. A target of ZrO₂ has been shown to provide high intensity beams of neutron-deficient isotopes of Mn, Cu, Zn, Ga, Ge, As, Se, Br, Kr and Rb, while a SiC target with a hot plasma ion source gives intense beams of radioactive isotopes of a number of light elements. All these systems are rather chemically unselective. Chemically selective performance has been obtained for several systems, i.e.: the production of neutron-deficient Au from (³He, pχn) reactions on a Pt/graphite target with a hot plasma ion source; the production of neutron-deficient Lu and LuF⁺ and Hf and HfF₃⁺ from a Ta-foil target with a hot plasma ion source under CF₄ addition; the production of neutron-deficient Sr as SrF⁺ and Y as YF₂⁺ form a Nb-foil target with a W surface ionizer under CF₄ addition; the production of neutron-deficient Se as COSe⁺ from a ZrO₂ target with a hot plasma ion source under O₂ addition; and the production of radioactive F from a SiC target with a hot plasma ion source operating in Al vapour.     

在线低能气体离子源

材料中氦和氢积累可引起材料性能的恶化甚至失效。为研究材料内氦和氢的存在形式、氦与氢及缺陷的相互作用、气泡的形成和演变过程以及各种因素的影响,建立一套离子束能量最高20keV的潘宁型气体离子源引出和聚焦系统,与200kV透射电镜联机,在离子注入现场原位观察氦和氢不同注入浓度下材料内部的微观结构及变化过程。对离子源进行氦离子的起弧、引出和聚焦测试。离子源在15–60mA放电电流范围内稳定地工作。在5×10–3Pa和1.5×10–2Pa工作气压下,放电电压约380V和320V。低气压下引出离子束流比高气压下大,且引出束流随放电电流和吸极电压的增加而增加。等径三圆筒透镜有显著聚焦作用,在距透镜出口150cm处,离子束流密度提高一个量级以上。能量10keV左右的氦离子获得束流密度约200nA·cm–2的离子束,可满足多种材料进行在线离子注入和原位电镜观测的需要。     

The Production and Acceleration of Metal Ions in the Harwell Variable Energy Cyclotron

The range of ions accelerated by the V.E.C. has recently been extended to metal ions. For example, a 5 to 10 ?A beam of 48 MeV 58Ni6+ is now available and has been used by a customer. This beam has become possible as a result of success in adapting the normal ion source for the production of metal ions. The problem was to add to the ion source a controlled source of metal vapour without increasing the size of the ion source or adding separate oven heaters and controls. This has been achieved by inserting a graphite liner into the existing ion source chimney, the metal being embedded in the liner and out of direct contact with the arc. Provided the arc power exceeds a few kilowatts, the metal becomes molten and the vapour diffuses through the graphite into the arc which then becomes self-sustaining. With nickel (the most widely tested so far), intensity at full radius of between 10 and 20 ?A of 6+ ions and 1?A of 8+ ions is readily obtained and source life averages about 4 hours. Other metals such as cobalt, iron, chromium and copper give similar results.     

Ge nano-layer fabricated by high-fluence low-energy ion implantation

A Ge nano-layer embedded in the surface layer of an amorphous SiO₂ film was fabricated by high-fluence low-energy ion implantation. The component, phase, nano-structure and luminescence properties of the nano-layer were studied by means of Rutherford backscattering, glancing incident X-ray diffraction, laser Raman scattering, transmission electron microscopy and photoluminescence. The relation between nano-particle characteristics and ion fluence was also studied. The results indicate that nano-crystalline Ge and nano-amorphous Ge particles coexist in the nano-layer and the ratio of nano-crystalline Ge to nano-particle Ge increases with increasing ion fluence. The intensity of photoluminescence from the nano-layer increases with increasing ion fluence also. Prepared with certain ion fluences, high-density nano-layers composed of uniform-sized nano-particles can be observed.     

真空弧离子源脉冲工作瞬间的放电行为

采用高速摄影和光谱诊断的方法研究了真空弧离子源脉冲工作瞬间的放电行为。拍摄了离子源放电瞬间吸氢电极上阴极斑的形成过程，分析了不同放电电流时阴极斑的发射光谱。实验结果表明，当脉冲工作电流为10^1—10^2A时，真空弧离子源放电区一般只有单个阴极斑，阴极斑的位置在同一次放电中的变化很小；较大的脉冲工作电流有利于提高阴极斑的温度，并最终导致氢离子浓度的增加，但也会使阴极材料的溅射更加严重，造成离子源等离子体品质下降。