Penning型负氢离子源诊断

 为了给小型医用回旋加速器提供负氢离子,研制了一台Penning型负氢离子源。采用发射光谱法对该负氢离子源进行了诊断,同时结合离子源功率变化对离子源工作状态进行了分析。实验测量了不同氢气流量、离子源弧流及磁场条件下,该离子源等离子体氢原子巴尔末系中前三条谱线的相对光强和离子源功率变化,分析了不同工作条件对离子源工作状态的影响。结果表明：在可调节范围内,该离子源的工作状态主要受氢气流量的影响,对离子源弧流及磁场的变化不敏感。     

等离子体中辐射的附加谱宽和谱形

等离子体为耗散介质，其中离子（或原子）辐射谱线将获得一个附加“宽度”２ｋ（ｗ），其中２ｋ（ｗ）代表等离子体中频率为ω的光子的衰率，这样就有可能对实验测得的等离子体中氢原子Ｌｙｍａｎ－α线的谱宽与传统理论的偏差提供一种解释，另外由于２ｋ（ｗ）是ω的函数，等离体中谱线形状将与洛仑兹谱形有差异。本文给出了不同浓度和不同温度下等离子体中ＣⅣ离子的辐射谱形，在一定的浓度和温度区间，辐射谱形的顶端甚至可能出现     

脉冲金属氢化物真空弧放电等离子体发射光谱特性

利用发射光谱方法对真空弧离子源放电等离子体特性进行了诊断。同时,基于局域热力学平衡等离子体的发射光谱理论,建立了等离子体的发射光谱拟合模型,对真空弧放电等离子体光谱进行了分析。针对TiH真空弧离子源,分别对330~340nm与498~503nm范围内Ti+离子与Ti原子的发射光谱进行了对比拟合,获得了较好的符合度,解决了传统Boltzmann斜率法计算等离子体温度需要孤立的不受附近谱线干扰的线状光谱的困难。最后,利用该方法计算了真空弧离子源在不同放电条件下的等离子体发射光谱、等离子体密度与温度参数。结果表明,TiH真空弧放电等离子体温度在1eV左右,同时,放电所产生的氢原子要远远大于金属原子,并且随着真空弧离子源馈入功率的增加,TiH电极中解吸附出来的氢比蒸发出来的金属增加得更多,这有利于TiH离子源在中子发生器方面的应用。     

强流激光离子源中的等离子体参数诊断

强流激光离子源是最有希望为重离子聚变直线感应加速器提供离子的离子源之一。离子源内等离子体决定了离子源性能和引出品质,为了了解强流激光离子源内等离子体参数,采用发射光谱和ICCD成像的方法对该离子源中的等离子体进行了诊断。该离子源由一台四倍频的266 nm Nd:YAG激光器和Cu靶组成,激光束经过透镜聚焦后照射在Cu靶上产生等离子体,激光打靶能量密度约为108 W/cm2,持续时间15 ns。ICCD相机拍摄了激光照射后等离子体的膨胀过程,初始时刻等离子体垂直表面喷射,膨胀速度约为1 cm/s。光谱仪测量了离子发射光谱,谱线主要由Cu原子的Cu Ⅰ谱线和Cu+离子的Cu Ⅱ谱线组成。采用Boltzmann图法得到膨胀等离子体电子激发温度约为1 eV,采用Stark展宽法得到电子密度约为1016 cm-3。     

基于氢原子碰撞辐射模型的发射光谱法诊断电子密度

基于碰撞辐射模型,利用氢原子的巴尔末线比对HUST射频负氢离子源等离子体电子密度进行诊断。首先针对HUST离子源等离子体的放电条件,建立了综合考虑氢原子直接激发和氢分子解离激发机制的碰撞辐射模型。基于建立的模型,利用氢原子的巴尔末线比来诊断电子密度。进一步分析了不同的氢原子分子密度比对电子密度诊断的影响,结果表明当电子温度较高,氢分子的解离度较低的等离子体放电状态下,必须同时考虑氢原子直接激发和氢分子解离激发对激发态氢原子的贡献。     

介质阻挡放电氢等离子体中氢原子浓度的光谱诊断

在化学气相沉积功能材料等离子体刻蚀及表面处理等过程中,氢原子起着非常重要的作用.文章详细论述了利用发射光谱技术诊断氢原子的基本原理,以氩气作为内标对介质阻挡放电氢等离子体中的氢原子浓度进行了定量的诊断,研究了氢原子浓度、氢分子解离率随气压的变化规律.发现在0.32到5.1 kPa气压范围内,氢分子的解离率由5.2%下降到0.089%,相应的氢原子浓度由4.9×1015·cm-3下降到1.3×1015·cm-3.文章还研究了氢Balmer系以及氩(750.4 nm)谱线的发射强度随气压、放电电压、频率等放电参数的变化规律.     

高频H型放电离子源的场特性

 从Maxwell方程组出发，推导了高频H型放电离子源放电空间的场分布, 并采用Mafia软件进行了三维实体建模，计算了高频离子源放电击穿前和稳定工作后的电磁场分布，得到了高频离子源放电空间电磁场分布的直观图像。通过比较击穿前高频电场的轴向和环向分量，得出了轴向电场在高频离子源击穿中起主要作用的结论，并进而推导出了高频离子源的击穿判据，得出了气体击穿时离子源击穿电压和放电管内气压的关系，与实验结果符合较好。     

中红外下半导体掺杂调制的表面等离子体透射增强效应

理论研究了平面电磁波通过n型重掺GaAs薄膜的透射谱.当GaAs薄膜两表面刻上亚波长的周期性沟槽结构时，透射谱在中红外波段出现了异常的透射增强现象.把这一现象归因于表面等离子体模式和波导模式的耦合.通过优化结构参数可以得到最大的透射效率.此外，发现随着掺杂浓度的升高，透射谱线中的透射峰逐渐向高频方向移动，最优化后透射峰值随掺杂浓度的升高而逐渐降低.这是由于掺杂浓度的改变，导致了不同的等离子体频率和电子碰撞频率，从而影响了激发模式和薄膜对电磁波的吸收. 关键词： 表面等离子体 掺杂半导体 增强透射 掺杂调制     

Z箍缩Al等离子体X特征辐射谱线数值模拟及考虑叠加效应后的修正

采用基于细致能级的非局域热动平衡模型,对"强光一号"装置10174发次Z箍缩铝等离子体特征辐射谱进行细致的分析和计算,提取电子密度约为3.5×1021cm-3.数值计算结果显示,采用单一等离子体状态参数不能很好地描述等离子体辐射特征谱线.在进一步的分析计算中,本文初步考虑高温区域和低温区域等离子体特征辐射谱线的叠加效应,将等离子体划分为高温高密度和低温低密度两部分,分析了两部分等离子体辐射对总辐射谱的贡献,并给出了修正后的等离子体辐射谱线.考虑叠加效应后,Heα伴线显著增强,计算结果改善明显.     

Hα线型分析

利用高斯分布拟合HT-6M托卡马克Hα线型，得出了由反射进入等离子体中的氢原子、氢分子离解后产生的氢原子，以及电荷交换产生的氢原子辐射Ｈα谱线的份额，由Doppler频移和展宽分别得出它们的入射速度和离子温度．在简化模型下讨论了氢原子的输运行为，得出了氢原子的密度分布和体发射系数，以及入射速度大小对粒子约束时间的影响，并与实验数据进行比较．由中性氢原子能量分布得出发生在边界的分子过程是氢分子的离解激发和电离离解 关键词：     

�����NBI ��Ƶ����Դ����������Ʒ���

为探究射频离子源驱动器线圈电气参数对射频放电的影响,主要进行了射频离子源等离子体激发的物理分析,并计算了射频电源的频率选择与线圈放电电流、线圈匝间电压以及放电气压之间的关系,设计了射频离子源驱动器的主要参数。研制的射频离子源驱动器装置,成功获得氢等离子体射频放电。实验结果和理论计算结果符合很好。     

ANALYSIS OF DUAL FREQUENCY CONFINED CAPACITIVELY COUPLED PLASMA AT LOW POWER

Confined dual frequency hydrogen plasma discharge has been investigated with microwave interferometer method and radial profiles are taken by Abel inversion technique. Dual radio-frequency sources, operating at 27.12MHz and 1.94MHz, are coupled to each other through the plasma. 27.12MHz RF power is used to enhance plasma density and 1.94MHz power is used to enhance ion acceleration energy to the electrode. Radial density profiles has been taken for comparing the effects of low frequency source that the secondary RF source causes reduction in plasma density due to the sheath expansion. Instead radial density profile is assumed as flat by most of the models, there is about 2.5eV of potential drop occurs from centre to boundary at 40W of primary source power. It has been observed that increasing sheath width (increasing the secondary source power to primary source power) reduces the bulk plasma volume and makes potential profile flattening in y direction. While the high frequency power is dissipated by electrons in the bulk plasma; low frequency power is mostly dissipated by ions in the sheath region. Using both high and low frequency power, we may control plasma density and ion acceleration energy to the electrode simultaneously.     

Experimental results of helicon sources

Helicon plasma sources are known as efficient generators of uniform and high density plasma.A helicon plasma source was developed for the investigation of plasma stripping and plasma lenses at the Institute of Modern Physics, CAS.In this paper, the characteristics of helicon plasma have been studied by using a Langmuir four-probe and a high plasma density up to 3.9×10~(13)/cm~3 has been achieved with the Nagoya type Ⅲ antenna.In the experiment, several important phenomena were found: (1) for a given magnetic induction intensity, the plasma density became greater with the increase of RF power; (2) helicon mode appeared at RF power between 300 W and 400 W; (3) the plasma density gradually tended to saturation as the RF power increased to the higher power; (4) a higher plasma density can be obtained by a good match between the RF power and the magnetic field distribution.The key issue is how to optimize the matching between the RF power and the magnetic field.Moreover, some tests on the extraction of ion beams were performed, and preliminary results are given.The problems which existed in the helicon ion source will be discussed and the increase in beam density will be expected by extraction system optimum.     

Plasma parameter diagnosis using hydrogen emission spectra of a quartz-chamber 2.45 GHz ECRIS at Peking University

A quartz-chamber 2.45 GHz electron cyclotron resonance ion source(ECRIS) was designed for diagnostic purposes at Peking University [Patent Number: ZL 201110026605.4]. This ion source can produce a maximum 84 m A hydrogen ion beam at 50 k V with a duty factor of 10%. The root-mean-square(RMS) emittance of this beam is less than 0.12π mm mrad. In our initial work,the electron temperature and electron density inside the plasma chamber had been measured with the line intensity ratio of noble gases. Based on these results, the atomic and molecular emission spectra of hydrogen were applied to determine the dissociation degree of hydrogen and the vibrational temperature of hydrogen molecules in the ground state, respectively. Measurements were performed at gas pressures from 4×10~(-4) to 1×10~(-3) Pa and at input peak RF power ranging from 1000 to 1800 W. The dissociation degree of hydrogen in the range of 0.5%-10% and the vibrational temperature of hydrogen molecules in the ground state in the range of 3500-8500 K were obtained. The plasma processes inside this ECRIS chamber were discussed based on these results.     

Study on the RF Power Necessary to Ignite Plasma for the ICP Test Facility at HUST

An Radio‐Frequency (RF) Inductively Coupled Plasma (ICP) ion source test facility has been successfully developed at Huazhong University of Science and Technology (HUST). As part of a study on hydrogen plasma, the influence of three main operation parameters on the RF power necessary to ignite plasma was investigated. At 6 Pa, the RF power necessary to ignite plasma influenced little by the filament heating current from 5 A to 9 A. The RF power necessary to ignite plasma increased rapidly with the operation pressure decreasing from 8 Pa to 4 Pa. The RF power necessary to ignite plasma decreased with the number of coil turns from 6 to 10. During the experiments, plasma was produced with the electron density of the order of 10¹⁶m^–3 and the electron temperature of around 4 eV. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

射频等离子体鞘层动力学模型

在流体力学方程的基础上建立了一种自洽的无碰撞射频等离子体鞘层动力学模型.这种自洽性包含两个方面:一方面,由于考虑了瞬时鞘层电场对离子运动的影响,因此该模型适用于描述任意频率段的射频鞘层演化过程;另一方面,在模型中采用等效电路方法来自洽地确定极板上的瞬时电位与瞬时鞘层厚度之间的关系.采用数值方法模拟出鞘层的瞬时厚度及极板的瞬时电位变化、鞘层内离子密度和电场强度等物理量的时空变化.结果表明,当射频场的频率小于或等于离子等离子体频率时,离子流密度明显地随时间变化 关键词： 射频 离子 鞘层 流体力学     

射频离子源束流特性分析

介绍了为HL-2A 装置设计的引出束功率为1MW 的射频离子源研制情况。目前，在测试平台上，该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，达到了其设计束功率的44%。用红外热成像的方法测量了离子束能量密度分布。结果表明，在距离引出系统地电极 1.3m 处，束密度分布遵循高斯分布。引出束的最佳导流系数为1.689×10^–6A•V^-3/2 左右，随射频功率改变有较小的变化。根据这些实验结果，采取了相关改进措施来改善离子源的引出束性能。     

Investigations on ionic processes and dynamics in the sheath region of helium and hydrogen discharges by laser spectroscopic electric field measurements

Temporally and spatially resolved measurements of the electric field distribution in the sheath region of RF and dc discharges provide a detailed insight into the sheath and ion dynamics. The electric field is directly related to the sheath ion and electron densities, the sheath voltage, and the displacement current density. Under certain assumptions also the electron and ion conduction current densities at the electrode, the ion current density into the sheath from the plasma bulk, the ion energy distribution function, and the power dissipated in the discharge can be inferred. Furthermore, the electric field distribution can give an indication of the collision-induced conversion between different ion species in the sheath. Laser spectroscopic techniques allow the noninvasive in situ measurement of the electric field with high spatial and temporal resolution. These techniques are based on the spectroscopic measurement of the Stark splitting of Rydberg states of helium and hydrogen atoms. Two alternative techniques are applied to RF discharges at 13.56 MHz in helium and hydrogen and a pulsed dc discharge in hydrogen. The measured electric field profiles are analyzed, and the results discussed with respect to the ion densities, currents, energies, temporal dynamics and species composition. Received: 26 July 2000 / Accepted: 12 December 2000 / Published online: 3 April 2001     

ǿ��RF ����Դ���Ƽ�����ʵ��

介绍了RF离子源驱动源的结构设计及RF线圈的热流固耦合分析。RF离子源采用外置天线的感应耦合方式,采用双射频驱动源设计,每个射频驱动源功率约60kW,总体功率为120kW,可产生均匀高密度的等离子体,以满足稳定的长脉冲运行的要求。在完成上述工作的基础上完成了RF离子源样机组装和初步实验测试。     

Properties of inductively coupled plasma source with helical coil

This paper presents modeling and experimental results of the voltage, current, and density profiles of a helical resonator plasma source. The source has a 5/4-wavelength (λ) helical resonator structure with the helical coil short-circuited at one end and open circuited at the other end. When the radio frequency (RF) tap for power feeding was located at an odd multiple of λ/4 from the short-circuited end, the observed voltage, current, and plasma density were higher in the short-circuited section than those in the open-circuited section. The opposite property was observed with the RF tap at an even multiple of λ/4. A microstrip transmission line model was used to explain the experimental results. The model accurately predicted the RF voltage and current profiles. After calculation of RF voltage and current, the plasma density was solved numerically. The difference between the calculated and measured plasma density was within a factor of two. The changes on the density profile indicate that the transport properties of plasma can be adjusted with the RF tap position