Unstable plasma characteristics in mirror field electron cyclotron resonance microwave ion source

Electron cyclotron plasma reactor are prone to instabilities in specific input power [3–7] region (150–450 watts). In this region power absorption by gas molecules in the cavity is very poor and enhanced input power gets reflected substantially without increasing ion density. There are abrupt changes in plasma characteristics when input power was decreased from maximum to minimum, it was observed that reflected power changed from <2% to ∼50%. Minimum two jumps in reflected power were noticed in this specific power region and these appear to be highly sensitive to three stub tuner position in the waveguide for this particular input power zone. Unstable plasma region of this source is found to be dependent upon the magnetic field strength. Some changes in reflected power are also noticed with pressure, flow and bias and they are random in nature.     

Characteristics of a hot ion collector placed in a weak ion cyclotron resonance magnetic field

The separation characteristics of a planar collector system placed in the weak magnetic field region of a facility that separates isotopes of stable metals by the ion-cyclotron-resonance method are calculated. An increase in the gyroradius of the accelerated ions in the weak field allows the designer to increase the collector plate spacing and decrease undesired screen losses. It is theoretically shown that placing the collector in the week field increases the degree of separation. Also, the transverse-to-longitudinal ion energy conversion makes it possible to extend the product deposition area on the collector plates and, thus, to reduce the thermal load on the collector and facilitate the long-term production of the target material in large amounts.     

2 cm电子回旋共振离子推力器离子源中磁场对等离子体特性与壁面电流影响的数值模拟

电子回旋共振离子推力器(electron cyclotron resonance ion thruster,ECRIT)离子源内等离子体分布会影响束流引出,而磁场结构决定的ECR区与天线的相对位置共同影响了等离子体分布.在鞘层作用下,等离子体中的离子或电子被加速对壁面产生溅射,形成壁面离子或电子电流,造成壁面磨损和等离子体损失,因此研究壁面电流与等离子体特征十分重要.为此本文建立2 cm ECRIT的粒子PIC/MCC(particle-in-cell with Monte Carlo collision)仿真模型,数值模拟研究磁场结构对离子源内等离子体与壁面电流特性的影响.计算表明,当ECR区位于天线上游时,等离子体集中在天线上游和内外磁环间,栅极前离子密度最低,故离子源引出束流、磁环端面电流和天线壁面电流较低.ECR区位于天线下游时,天线和栅极上游附近的等离子体密度较高,故离子源引出束流、天线壁面电流和磁环端面电流较高.腔体壁面等离子体分布与电流受磁场影响最小.     

电子回旋共振离子推力器放电室等离子体数值模拟

电子回旋共振离子推力器属于静电型推力器,具有寿命长、比冲高、结构简单、可靠性高等优点,适用于深空探测等长时间空间飞行任务.放电室是一个关键部件,其内部通过电子回旋共振产生等离子体.针对放电室内等离子体流场建立飘移-扩散近似模型,采用迎风格式有限差分法对该模型进行数值求解,得到了放电室内不同时刻的等离子体流场分布及其演化规律.数值模拟结果可以为推力器的设计和实验研究提供有用信息.     

Selection of resonant ions in isotope separation by ion cyclotron resonance using an acute-angled magnetic field

By numerically solving equations of motion, the feasibility of separating a charged particle flow containing particles with high and low transverse velocities and passing through an acute-angled magnetic field is considered. The flow is divided into two components uniformly distributed over the cross section that contain particles with initially high and initially low transverse velocities.     

电子回旋共振微波等离子体刻蚀α:CH薄膜的工艺

为了刻蚀出图形完整、侧壁陡直、失真度小的α:CH薄膜微器件,研究了有铝和无铝掩膜、气体流量比、工作气压对刻蚀速率的影响,并对纯氧等离子体刻蚀稳定性进行了研究。研究结果表明：在相同条件下,刻蚀速率随刻蚀时间变化不大;a:CH薄膜上有铝和无铝掩膜时,刻蚀速率相同;流量一定时,刻蚀速率随氩气和氧气体积比的增大而降低,当用纯氩气时,几乎没刻蚀作用;刻蚀速率随工作气压的增大而降低。实验中,得到最佳刻蚀条件是：纯氧气,流量4 mL·s-1,工作气压9.9×10-2 Pa,微波源电流80 mA,偏压-90 V。     

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The generation and control of microwave electron cyclotron resonance (ECR) plasma cathode electron beam is studied experimentally. A complete set of discharge, electron beam extraction, focusing and measuring system was set up. The characteristics and performance of microwave ECR plasmas as electron beam extraction source were studied by measuring the current of water cooling target and the beam spot size on the target. Experimental results indicated that both microwave input power and accelerating voltage are conducive to improving electron beam current. The influence of gas pressure on the electron beam current was complex. With the increase of gas pressure, the electron beam current is characterized by decreasing first and then increasing. The extracted electron current of microwave ECR plasma cathode can reach 75mA at gas pressure of 7×10⁻⁴Pa, and the energy of the electron beam can reach 9keV. The energy utilization can reach 0.6. By adjusting the current of the focusing coil, the diameter of electron beam spot is reduced from 20mm to 13mm and the electron beam current keeps the value unchanged.     

微波ECR全方位离子注入制备类金刚石碳膜的结构及摩擦学性能研究

利用微波ECR全方位离子注入技术，在单晶硅（100）衬底上制备类金刚石薄膜.分析结果表明，所制备的类金刚石碳膜具有典型的类金刚石结构特征，薄膜均匀、致密，表面粗糙度小，摩擦系数小.其中，薄膜的结构和性能与氢流量比关系密切，随氢流量比的增加，薄膜的沉积速率减小，表面粗糙度降低，且生成sp³键更加趋向于金刚石结构，表面能 更低，从而使摩擦系数大幅降低. 关键词： 全方位离子注入 类金刚石碳膜 拉曼光谱 摩擦磨损     

微波电子回旋共振等离子体阴极电子束的实验研究

介绍了实验室研制的微波电子回旋共振(ECR)等离子体阴极电子束系统及初步研究结果，该系统包括微波ECR 等离子体源、电子束引出极、聚焦线圈等。通过测量水冷靶电流和靶上的束斑尺寸，实验研究了微波ECR 等离子体阴极电子束的流强、聚束性能等随电子束系统工作条件的变化。结果表明：微波输入功率越高、引出电压越高，引出电子束流强越大；工作气压对电子束流强的影响较复杂，随气压增加呈现出先降低后升高的特点；在7×10⁻⁴Pa 的极低气压下电子束流强可达75mA，引出电压9kV；能量利用率可达0.6；调整聚焦线圈的驱动电流，电子束的束斑直径从20mm 减小到13mm，电子束流强未有明显变化。     

Heating of gadolinium plasma ions by the ion cyclotron resonance method

Resonance rf heating of gadolinium plasma ions is calculated in the configuration when an electric field travels along a permanent magnetic field and simultaneously rotates in the direction normal to the latter. Two model functions are taken as initial ion distribution functions over longitudinal velocities: one is a linear function of the velocity in the low velocity range and the other is a shifted semi-Maxwellian function. The ion transverse velocity distribution function is calculated under the assumption that the initial “transverse” distribution function is Maxwellian with a temperature of 5 eV. Ion fluxes toward collector plates are calculated by integrating the total distribution function over the allowed ranges of longitudinal and transverse velocities and transverse coordinates of the guiding center of the ions before the collector. The calculation is performed as applied to the ¹⁵⁷Gd target isotope and its two nearest neighbors. The effect of the longitudinal temperature on the width of the heating efficiency resonance line and of the longitudinal magnetic field on the ion heating selectivity is studied. Also, the influence of the longitudinal wavenumber of the warming traveling electric field on the selectivity of an ion cyclotron resonance reactor is investigated. The heating efficiency is estimated from the frequency dependence of the fraction of ions heated to an energy above a given value.     

Electron field emission characteristics of nano-catkin carbon films deposited by electron cyclotron resonance microwave plasma chemical vapour deposition

This paper reported that the nano-catkin carbon films were prepared on Si substrates by means of electron cyclotron resonance microwave plasma chemical vapour deposition in a hydrogen and methane mixture. The surface morphology and the structure of the fabricated films were characterized by using scanning electron microscopes and Raman spectroscopy, respectively. The stable field emission properties with a low threshold field of 5V/μm corresponding to a current density of about 1μA/cm^2 and a current density of 3.2mA/cm^2 at an electric field of 10V/μm were obtained from the carbon film deposited at CH4 concentration of 8%. The mechanism that the threshold field decreased with the increase of the CH4 concentration and the high emission current appeared at the high CH4 concentration was explained by using the Fowler-Nordheim theory.     

Characterization of microwave plasma generated in inhomogeneous magnetic field

The paper is devoted to the investigation of the electron cyclotron resonance (ECR) discharge in the decreasing magnetic field in the pressure range from 0.02 Pa to 90 Pa and the absorbed microwave power from 50 W to 400 W. For a discharge characterization we used the floating potentialU _fl and the saturated ion current densityi _sat ⁺ . The influence of the substrate holder presence on the plasma microparameters was studied. It was shown that for the substrate holder located near ECR at pressures below 0.3 Pa mainly the magnitude ofU _fl strongly depends on the pressurep, the absorbed microwave powerP _a, and the position of the substrate holder with respect to ECR. The values ofU _fl in the plasma in which the substrate holder is inserted strongly differ from those in the plasma without the substrate holder.U _fl of low pressuresp<0.05 Pa achieves high positive values of about +50 V and this results in sputtering of chamber walls.     

不同磁路电子回旋共振离子源引出实验

空间推进所用的电子回旋共振离子源(ECRIS)应具有体积小、效率高的特点. 本文研究的ECRIS使用永磁体环产生磁场, 有效减小了体积, 该离子源利用微波在磁场中加热电子, 电子与中性气体发生电离碰撞产生等离子体. 磁场在微波加热电子的过程中起关键作用, 同时影响离子源内等离子体的约束和输运. 通过比较四种磁路结构离子源的离子电流引出特性来研究磁场对10 cm ECRIS性能的影响. 实验发现: 在使用氩气的条件下, 特定结构的离子源可引出160 mA的离子电流, 最高推进剂利用率达60%, 最小放电损耗为120 W·A^-1; 所有离子源均存在多个工作状态, 工作状态在微波功率、气体流量、引出电压变化时会发生突变. 离子源发生状态突变时的微波功率、气体流量的大小与离子源内磁体的位置有关. 通过比较不同离子源的引出离子束流、放电损耗、气体利用率、工作稳定性的差异, 归纳了磁场结构对此种ECRIS引出特性的影响规律, 分析了其中的机理. 实验结果表明: 保持输入微波功率、气体流量、引出电压不变时, 增大共振区的范围、减小共振区到栅极的距离, 离子源能引出更大的离子电流; 减小共振区到微波功率入口、气体入口的距离能降低维持离子源高状态所需的最小微波功率和最小气体流量, 提高气体利用率, 但会导致放电损耗增大. 研究结果有助于深化对此类离子源工作过程的认识, 为其设计和性能优化提供参考.     

Chromatic monitoring of downstream microwave plasma source

The application of the chromatic sensing for monitoring of a microwave plasma source is described. The emitted radiation from the plasma excited in the argon, oxygen and CF₄ mixture was measured with three PIN-diodes with integrated optical filters. The response of the chromatic signals on variation of power and gas composition was investigated. Whereas a good sensitivity of the integrated optical signal to the power was confirmed, only a limited sensitivity to the working gas mixture was found.     

Linear and non-linear aspects of ion cyclotron resonance

A quantum-mechanical approach based on a projection-operator formalism is presented for the ion motion and the instantaneous power absorption in ion cyclotron resonance. The role of non-linearities in the power absorption is investigated by incorporating the formalism in a non-linear response theory, and their effect on the line-shape is discussed.     

电子回旋共振微波等离子体技术及应用

 电子回旋共振微波等离子体技术(ECR-MP)在表面处理、等离子体刻蚀和薄膜制备，尤其是高品质的激光惯性约束聚变薄膜靶的制备中有着重要的应用。综述了ECR-MP的基本原理、反应装置、实验研究、理论研究和应用情况的发展现状，同时分析了其今后可能的发展趋势。     

电子回旋共振微波等离子体技术及应用

电子回旋共振微波等离子体技术(ECR-MP)在表面处理、等离子体刻蚀和薄膜制备,尤其是高品质的激光惯性约束聚变薄膜靶的制备中有着重要的应用。综述了ECR-MP的基本原理、反应装置、实验研究、理论研究和应用情况的发展现状,同时分析了其今后可能的发展趋势。