放电功率变化对电磁波在电感耦合闭式等离子体中的衰减特性

射频电感耦合等离子体(ICP)放电方式能够在较宽的压强范围内产生大面积、密度高的等离子体,在对电磁波衰减应用中具有较大优势。通过研究ICP等离子体与电磁波相互作用的过程,改进闭式等离子体模型,建立电磁波在非均匀等离子体中传播的分层计算模型,对实测诊断分布情形下等离子体与电磁波的相互作用进行研究,得到不同功率条件下电磁波衰减的变化情况;提出射频电感耦合闭式等离子体用于电磁波衰减的方法并实验验证,基于等离子体覆盖金属平板的测量模型,在实验室内搭建了以金属板为衬底的弓形微波反射测试系统,研究了闭式等离子体对4～8 GHz频段范围内微波反射的作用特性,以及不同射频功率对微波反射的影响规律,并将实验测量与计算结果进行对比分析。实验表明,通过功率调节,电感耦合闭式等离子体对5.92～6.8 GHz频带电磁波具有明显的衰减作用。     

射频电感性耦合等离子体调谐基片自偏压特性

采用调节射频电感性耦合等离子体中基片电极与地之间的外部电路阻抗的方法,控制基片电极的射频自偏压。研究了调谐基片自偏压随外部调谐电容值的变化特征,得到了调谐基片射频自偏压随射频放电功率、气压的变化曲线。在一定放电参数区域内,调谐基片射频自偏压随调谐电容的变化曲线呈现跳变、双稳、迟滞现象。     

等离子体化学气相沉积氮化镓薄膜中的N2/TMG等离子体发射光谱分析

对电子回旋共振低温等离子体化学气相沉积工艺(ECR-PECVD)沉积GaN薄膜过程中的氮气和三甲基镓有机金属气体(TMG)混合气体等离子体发射光谱进行分析。结果表明TMG 在等离子体自加热条件下就发生离解,N₂/TMG混合气体ECR等离子体主要以Ga气体粒子和亚稳态氮分子为主。发射光谱特征谱线随微波功率变化分析表明：当微波功率高于400 W时,亚稳态氮分子浓度随着微波功率的增加而增加,而高激发态氮分子以及氮分子离子浓度却随着减少。     

真空中不同极化电磁波在微波等离子体喷流中的衰减特性实验研究

在真空环境中，利用空间反射电磁波测量装置，开展微波等离子体喷流对垂直和水平极化电磁波衰减的实验研究，分析不同极化电磁波在等离子体中衰减的影响因素.实验结果表明：以氩气为工质，真空室中微波等离子体喷流对垂直和水平极化电磁波具有显著的吸收效应.发生器流量、功率以及实验真空度对垂直极化电磁波在等离子体中的衰减影响明显.真空度和发生器功率对水平极化电磁波没有显著影响. 关键词： 等离子体中的电磁波 等离子体基本性质 电磁波     

大气压微波等离子体射流装置放电特性研究

基于同轴传输线结构设计了两种不同喷嘴结构的大气压微波等离子体射流(MW-APPJ)装置,其工作频率2.45 GHz,工作气体为氩气,分别研究了两种不同喷嘴结构对等离子体放电特性产生的影响。仿真结果表明,MW-APPJ在气体喷嘴处会产生高强度的电场,经过优化结构,实现在频率2.45 GHz下,喷嘴处的场强满足氩气电离的击穿场强阈值要求。同时,利用多物理场耦合仿真软件对装置的气流分布进行了稳态模拟,并通过实验对比分析了两种喷嘴结构下大气压氩等离子体射流的基本特性。实验结果表明,不同的喷嘴结构会影响等离子体装置的反射系数随输入功率的变化规律,但并不影响等离子体射流长度随输入功率的变化规律和反射功率随进气流量的变化规律;同时,在大气压下,稳态微波等离子体射流呈现出类金属性,等离子体中的电子只能在很薄的区域中吸收微波能量,因而造成微波的反射功率较大。     

真空环境中等离子体喷流对反射电磁波衰减的实验研究

在真空环境中，利用传输线测量装置，开展微波等离子体喷流对反射电磁波衰减的实验研究.实验结果表明，采用传输线测量方法能够有效地获得等离子体对反射电磁波的衰减；在5GHz附近，以氩气为工质，流量为52.5mg/s时，52W微波功率在真空环境中产生的等离子体喷流能对反射电磁波产生最大的衰减；增加微波功率、降低真空环境压强可以提高等离子体对反射电磁波的衰减；要使等离子体能够对反射电磁波产生最大的衰减，必须选取合适的发生器参数. 关键词： 电磁波在等离子体中的传输 等离子体基本过程 电磁波     

超光滑基片等离子体表面处理研究

通过对射频功率、反应室压强和处理时间等参量进行实验,系统研究了等离子体处理对基片表面状态的影响.结果表明,等离子体处理可以溅射去除加工变质层,降低表面粗糙度,提高基片表面洁净度和表面能.优化后的参量证实,经等离子处理的基片比未经等离子体处理的基片镀膜后损耗平均降低34.2 ppm,并且显示出良好的一致性.     

采用发射光谱和朗缪尔探针诊断低温低压氢等离子体

 使用发射光谱诊断法和Langmuir探针诊断法,测量了螺旋波激发等离子体化学气相沉积装置中产生的氢等离子体的发射光谱和电流-电压曲线。运用日冕模型和Druyvestey方法,对不同放电参数条件下激发态氢原子密度﹑等离子体密度及电子能量分布的变化规律进行了研究。结果表明：激发态氢原子密度随射频功率增大而增大,随工作气压的增大先增大,后缓慢下降。等离子体密度随射频功率增大线性增大,随工作气压的增加也是先增大,出现峰值后缓慢下降。电子平均能量随射频功率的变化是先增大,后达到平衡;随着工作气压的增大逐渐减小。两种诊断方法得到的结果基本相符。在低温低压等离子诊断中,两种诊断方法结合使用,可以得到更准确和更多的等离子体信息。     

大气压微波等离子体炬的仿真设计与实验

设计了一个低成本、高稳定性的基于BJ22矩形波导的微波等离子体炬源。整个系统由1～10 kW主频2.45 GHz的磁控管微波功率源、环形器、调谐器和微波反应腔体组成。通过特殊设计的调谐装置,在气体喷嘴处产生高幅值的电场强度,使工作气体电离形成大气压开放式微波等离子体炬。对影响电场强度的几个关键因素进行了仿真,得出各个参数对场强的影响规律;根据仿真参数设计了微波反应腔体,该系统可以在大气压下激发和维持开放的稳定氩气、氦气、氮气和空气等离子体炬。对等离子体炬的基本特性和基本参数进行了研究,验证了设计参数的正确性,讨论了其可扩展性及潜在的工业应用。     

射频功率对氢气与反式二丁烯的低压电感耦合等离子体的影响（英）

利用等离子体聚合技术制备的GDP壳层是目前ICF靶丸的主要烧蚀层材料。为了了解GDP薄膜沉积过程中的CH等离子体的状态,采用朗缪尔探针和质谱仪对C4H8/H2等离子体的组分和状态参数进行了诊断,并对等离子体的电子能量分布函数、电子密度、电子温度等进行了深入分析。同时讨论了等离子体状态与放电参数之间的关系。研究发现,射频功率对等离子体参数有明显的影响。从10 W到35 W,电子密度正比于射频功率。随着射频功率的增加,在两步电离机制作用下,电子温度和等离子体电势呈现先减小后增大的变化趋势。另外,在高气压下,质谱诊断中发现了大量的稳定的小质量碎片离子,这表明在高气压下等离子体气相中的离子碎片聚合反应被抑制。     

ECR-PECVD制备Si3N4薄膜沉积工艺的研究

由偏心静电单探针诊断了电子回旋共振等离子体增强化学汽相沉积(ECR-PECVD)反应室内等离子体密度的空间分布规律．结果表明在轴向位置Z=50cm处,直径Φ12cm范围内等离子体密度分布非常均匀．分析了等离子体密度径向均匀性对沉积速率均匀性和薄膜厚度均匀性的影响．讨论了沉积制备一定薄膜厚度的Si₃N₄薄膜的工艺重复性．研究了各种沉积工艺参数与Si₃N₄薄膜沉积速率的相互关系．得到了ECR-PECVD技术在沉积薄膜时的工 关键词：     

Edge Turbulence During Limiter Biasing Experiments in the TJ-II Stellarator

The influence of limiter biasing on plasma confinement, turbulence and plasma flows has been investigated in the TJ-II stellarator. Experimental results show that it is possible to modify global particle confinement and edge plasma parameters with both positive and negative biasing. Significant and minor modifications in the structure of plasma fluctuations have been observed during the transition to improved confinement regimes induced by limiter biasing. These results show evidence of electric field induced improved confinement via multiple mechanisms. The investigation of the relaxation of plasma potential and electric fields shows evidence of two different characteristic decay times.     

The effect of the use of different electrode materials for edge-plasma biasing on plasma density and floating potential modifications

The effect of the use of different electrode materials for edge-plasma biasing on plasma density and floating-potential profile modifications has been recently investigated on the CASTOR tokamak. Dependences of biasing current, edge plasma density and floating potential on biasing voltage have been measured. Induced relaxation events and fast (10–50) kHz oscillations are shown and surface changes of the biasing electrodes are discussed in the paper. Presented at the Workshop “Electric Fields, Structures and Relaxation in Edge Plasmas”, Tarragona, Spain, July 3–4, 2005.     

Laser-excited dust lattice waves in plasma crystals

Laser-excited waves in a two-dimensional dust plasma crystal have been observed experimentally in a parallel plate rf discharge. The measured dispersion relation is compared with theoretical models. Agreement is found with dust lattice waves, whereas deviations from dust acoustic waves exist. From the dispersion relation of a dust lattice wave the screening of the particles in the rf sheath is determined.     

Elektrische Charakterisierung von Hochfrequenz-Niederdruck-Gasentladungen

In recent years there has emerged significant interest in low pressure radio frequency (rf) glow discharges which are used widely particulary in IC fabrication. Various parameters of the rf glow discharge have been found to be useful for its electrical characterization; however, there is no uniformity and agreement. Extensive experimental investigations on various discharge systems have shown, that the self-bias on the rf driven electrode, the complex conductivity and the breakdown characteristic are preferable parameters of rf discharges. Advantageously the self-bias and the complex conductivity should be presented in dependence on the pressure and the applied rf voltage. The discharge current cannot be measured quite accurately due to currents via leaky capacitors and the deviations from a sinusoidal form of the current due to nonlinearities.     

Orbital motion of dust particles in an rf magnetron discharge. Ion drag force or neutral atom wind force

Microparticles with sizes up to 130 μm have been confined and the velocity and diameter of particles in a plasma trap of an rf magnetron discharge with an arc magnetic field have been simultaneously measured. The motion of the gas induced by electron and ion cyclotron currents has been numerically simulated using the Navier-Stokes equation. The experimental and numerical results confirm the mechanism of the orbital motion of dust particles in the magnetron discharge plasma that is associated with the orbital motion of the neutral gas accelerated by electron and ion drift flows in crossed electric and magnetic fields.     

Ion bombardment of amorphous silicon films during plasma-enhanced chemical vapor deposition in an rf discharge

The characteristics of ion and electron fluxes to the surface of a growing silicon film are investigated in various rf discharge regimes in silane at frequencies of 13.56 MHz and 58 MHz in plasma-enhanced chemical vapor-deposition (PECVD) apparatus. The energy spectra of the ions and electrons bombarding the growing film are measured. The electronic properties of films grown under various degrees of ion bombardment are studied. The correlation of these properties with the ion parameters in the rf discharge plasma during film growth is discussed. Zh. Tekh. Fiz. 68, 52–59 (February 1998)     

ECR-PECVD制备Si3N4薄膜的光学特性研究

本文研究了ECR-PECVD制备的Si₃N₄薄膜的光学特性.得到的Si₃N₄薄膜具有光致发光效应,在280℃沉积制备的Si₃N₄薄膜的光致发光波长为400nm,具有较好的单色性.测试分析了Si₃N₄薄膜对可见光、红外光具有较高的透射性能,Si₃N₄薄膜可作为红外光的增速减反射膜.     

Multifractal analysis of plasma turbulence in biasing experiments on Castor tokamak

Experiments as well as some stochastic models have shown that behaviour of the transport in the edge plasma in fusion devices should be considered as a multi-scale phenomenon. The multifractal statistics describes processes as a multiplicative cascade with a complex self-similarity. The multifractal analysis, which enables to clearly demonstrate the turbulent properties of plasma, was applied to fluctuating signals in the biasing experiments. The influence of the biasing parameters is shown. A comparison with other types of the analysis is illustrated, too. Presented at the Workshop “Electric Fields, Structures and Relaxation in Edge Plasmas”, Tarragona, Spain, July 3–4, 2005.     

Feasibility of rf plasma heating in the Globus-M spherical tokamak at frequencies above the ion cyclotron frequency

Feasibility of rf plasma heating in the Globus-M spherical tokamak at frequencies several times higher than the ion cyclotron frequency is considered. Results from a numerical analysis of this problem by using one-and two-dimensional codes are presented. It is shown that, for the plasma parameters attainable in this device, the single-pass absorption of fast magnetosonic waves reaches 60%. The energy is released near the plasma axis. The radiation resistance of a one-loop antenna should be close to 1 Ω. The design of an antenna that allows one to match the rf oscillator to the load is described. The parameters of the antenna resonator required for optimum operation of the antenna are given.