EAST超导托卡马克装置真空室壁处理的研究

壁处理技术被广泛应用于托卡马克装置上,以降低装置本底杂质水平,改善器壁的再循环.自2008年起,EAST面向等离子体的第一壁采用全碳材料,由于特殊的石墨晶体多孔结构,具有高放气率以及对H₂O,H₂等杂质气体的高吸附性,从而使等离子体放电前期的装置真空室壁处理尤为关键.本文介绍了EAST装置真空室壁处理的实验系统,并研究了装置烘烤与不同工作气体及工作参数下的直流辉光放电清洗对杂质粒子的清除效果.实验结果表明:EAST装置真空室在经过长时问的前期壁处理后,显著地降低了真空室内壁的出气率与本底杂质浓度,这对随后进行的等离子体放电实验非常有必要.     

H_2辉光放电清洗时轰击器壁的离子能量测量与分析

一、引言 辉光放电是清洗锻炼环流器真空室器壁的有效手段。H_2辉光放电时,氢离子轰击器壁与器壁中的C和O发生化学反应,生成CH_4,H_2O等气体;同时,这些离子提供能量使得吸附在器壁表面的杂质气体脱附,从而被泵出真空室外,达到清洗锻炼的目的。由于辉光放电时,离子轰击的能量较高,会引起一定的溅射沉积。我们在模拟真空室(六通装置)进行了辉光放电,对各种参数下的离子能量进行了测量,从中找出了离子能量与极间电压(阳极与器壁之间的电压)、放电电流、以及气压、离子流密度之间的某些关系。     

氦、氢直流辉光清洗对杂质的清除实验

直流辉光放电清洗在现代聚变装置上应用非常广泛,如JT－60U,JET,TFTR等。HL－1M装置是单层真空室结构,其材料为00Cr18Ni10Ti不锈钢和石墨孔栏,石墨覆盖整个真空室内壁表面的6％,使用2套超高真空机组抽气。因此真空室内可能有金属杂质Cr,Ni等,主要来源于器壁;还含有杂质Si,B等,主要来源于器壁的原位沉积处理,如硅化[直流辉光放电清洗（GDC）（SiH4 He)],硼化[GDC(C2B10H12 He)]等。而目前运行的聚变装置中主要是来源于石墨的低Z杂质（C和O等）,对第一壁进行He、H2、H2O等。由此可知,真空室器壁内表层的吸附物大致为金属氧化物、非金属氧化物、碳氢化合物、氢氧化合物等,为了更好地控制密度和真空壁条件达到清除其杂质的目的,我们分别用He,H2对真空室器壁进行直流辉光放电清洗。     

间隙绝缘电极辉光放电实验观察

实验研究了 ITER H₂/He 辉光放电壁处理(GDC)系统的电极合理的间隙绝缘参数及标定辉光过程中 沉积在电极头部的热负载。进行了 H₂/He 击穿电压特性试验,在 ITER GDC 预期的壁离子电流密度条件下研究了 H₂/He 辉光放电电压和试验电极上热负荷与压强的关系、试验电极启辉耐受特性、试验电极温度与热负荷的关系 以及在不同区域辉光放电的气压特性。介绍了 H₂/He 放电期间在电极及其附近区域的溅射和沉积的检测结果以及 对间隙绝缘的影响。为 ITER 辉光放电壁处理系统的设计和运行提供参考。      

亚辉光放电在HL—1装置的应用

本文简述亚辉光放电在HL-1装置上的应用。实验表明,这是一种安全、简便有效的清洗和碳化手段,它可以弥补磁控清洗放电和碳化的不足之处,并为HL-1M装置器壁锻炼提供了先行试验。     

HL—1M托卡马克装置的DC辉光放电清洗

本文简要叙述了ＨＬ－１Ｍ的ＤＣ辉光放电清洗技术和放电结果。实验表明，类似ＨＬ－１Ｍ托卡马克装置的真空室，经过烘烤，Ｔａｙｌｏｒ放电和ＤＣ放电清洗后，有可能得到高品质的等离子体。     

HL-2M 装置初始等离子体放电阶段的直流辉光放电清洗系统研制

基于 HL-2M 托卡马克初始等离子体放电的工程需求,设计并研制了直流辉光放电清洗系统,包括电 极、馈线、电源、控制以及监测等关键部件和辅助子系统。研制完成后开展了系统装配和工程调试,并投入到首 次等离子体放电。实验结果表明,该直流辉光放电系统运行稳定、可靠,且此辉光放电清洗显著降低了真空室本 底杂质浓度,能满足 HL-2M 装置初始等离子体放电的壁条件需求。     

HL-2A托卡马克装置真空系统

介绍了HL 2A装置真空系统研制。它由真空主抽气系统、抽气偏滤器、直流辉光放电清洗系统组成。主抽气系统提供了装置真空室从大气到高真空、烘烤除气、直流辉光放电清洗所需要的抽气能力。抽气偏滤器初步实现了托卡马克放电过程中边缘粒子的抽运与控制;直流辉光放电清洗系统保证了装置良好的真空器壁条件。介绍了这些系统的初步运行情况,并给出了其测试结果。HL 2A装置首轮物理实验运行时真空室极限真空度达到4.6×10-6Pa,12h总漏放气率为1.8×10-5Pa·m3·s-1。     

大气压介质阻挡辉光放电中放电电流的测量与分析

介质阻挡放电产生的低温等离子体具有广泛的应用前景而成为研究热点。文章利用平行平板介质阻挡放电装置,在流动的氦气中实现了大气压均匀辉光放电,得到了大气压下的均匀等离子体。利用电学方法将放电电流从总电流中分离出来,从而得到了辉光放电的放电电流。通过分析放电电流、外加电压、气隙上电压以及壁电荷电量之间的相互关系,可以研究气体放电过程中壁电荷积累的微观动力学行为。实验结果表明壁电荷主要是在放电电流脉冲持续期间积累的,但电流脉冲结束后,由于气隙电压没有改变极性,壁电荷还会逐渐积累,气隙电压改变极性后,壁电荷量随时间减小。这些结果对壁电荷在介质阻挡辉光放电中作用的深入研究和大气压介质阻挡辉光放电的工业应用具有重要意义。     

HL-2A装置真空系统

现代核聚变实验装置要求的真空系统必须实现以下主要功能：（1）装置真空室的零部件及总体抽空和检漏；（2）真空室的烘烤除气（H2O）；（3）辉光放电清洗和面对等离子体部件的锻炼及原位处理；（4）边缘粒子的抽运与控制；（5）等离子体放电实验运行。     

Glow discharge cleaning of vacuum switch tubes

To clean the surfaces of parts inside a vacuum-switch tube (VST) the authors propose a technique which generates a glow discharge between the inner electrodes and the copper grid surrounding it. Photographic observation reveals that the glow discharge spreads out and cleans the whole surface inside the VST. A breakdown test between the inner electrodes shows the effect of the cleaning with this technique. Higher breakdown voltage between the inner electrodes is attained by performing this glow discharge cleaning in argon rather than hydrogen gas. The difference of the cleaning effect seems to be attributed to that of the energy transfer from ion species to the adsorbed molecules and microprotrusions on the surfaces     

用于辉光放电清洗的LCC谐振变换器仿真

针对辉光放电清洗系统中气体击穿之后对电源的恒流要求，提出用LCC谐振变换器的新方案，以改进辉光放电清洗电源方案，增加电源方案储备。利用软件工具选取参数范围、辅助理解拓扑特性以及验证方案。分析了LCC传递函数中主要参数品质因数QL和串并联电容比A对电路增益以及谐振器件应力的影响，设计了合理的参数取值。根据参数取值，利用MATLAB仿真表明，电源的闭环仿真输出达到额定值，LCC拓扑能满足辉光放电清洗电源的参数要求。LCC谐振变换器的电流归一化曲线表现出良好的恒流特性，适合设计成电流源。     

Time dependent argon glow discharge treatment of Al-alloy samples

Aluminium alloy ultra-high vaccum system provides a convenient tool to access the UHV region due to short pump down time, its reduced weight, low cost etc. For UHV systems, aluminium and its alloys are preferred materials to stainless steel. A cylincrical discharge chamber of SS 304 with various ports on it, evacuated by turbomolecular pumping unit is used in the experimental system. A hollow cathode de glow discharge in argon for different time durations is used to treat chemically cleaned ASA 6063 aluminium alloy samples, keeping all other parameters constant. The scanning electron microscope (SEM) is used to examine processed surfaces and to study topographical features. The energy dispersive microanalysis by X-rays (EDX) is used to determine the elemental composition of the samples. The results indicate the physical sputtering taking place in Ar GDC. The etched area increases with discharge time duration. The EDX spectrum shows the inconsistency in weight percentage of various elements of Al-alloy.     

HL-2M初始等离子体放电阶段的辉光放电清洗系统电极的设计与分析

针对 HL-2M 装置初始等离子体放电阶段所需的直流辉光放电清洗系统的电极进行了设计。对辉光 放电清洗系统在不同工况下的系统负载进行了分析和拟定,并确定了电极结构设计分析标准。根据系统电极的结 构特点并结合系统负载规范与分析标准,依据不同的失效模式对电极进行了失效分析。分析结果表明,此针对初 始等离子体放电的电极设计能可靠安全运行,满足设计需求。     

The influence of a radial magnetic field on current-voltage characteristics of toroidal glow discharge

The present paper deals with the influence of a radial magnetic field on different regions of the toroidal glow discharge and with the subsequent changes of the current-voltage characteristics. From the above it is clear that when studying the influence of a transverse magnetic field on the glow discharge it is necessary to understand that the discharge is not a homogeneous unit and the change of current-voltage characteristics involves the total sum of changes of the properties in different regions of the discharge.     

Subnormal Glow Discharge Detection of Optical and Microwave Radiation

Commercial indicator lamp glow discharge tubes in the subnormal glow mode exhibit variable frequency tuned filter video response to optical and microwave radiation. Sensitivity to optical radiation can be particularly increased by using such devices in the subnormal rather than abnormal glow. These phenomena are discussed in terms of physical electronics and an equivalent circuit. A comparison is made of abnormal and subnormal glow mode properties. It is hoped that this model can lead to glow discharge lamp design for specific circuit applications involving subnormal glow mode characteristics. Relationships between glow discharge detector physical and electronic parameters are derived.     

Spectroscopic and chemical reactivity analysis of D-Myo-Inositol using quantum chemical approach and its experimental verification

Glow discharge conditioning (GDC) has long been accepted as one of the basic wall conditioning techniques for achieving ultrahigh vacuum in an unbaked chamber. As a part of this fundamental experimental study, a test chamber has been fabricated from stainless steel 304 L with its inner surface electropolished on which a detailed investigation has been carried out. Both helium and hydrogen gases have been employed as discharge cleaning medium. The discharge cleaning was carried out at 0.1 A /m ² current density with working pressure maintained at 1.0 × 10 ^-2 mbar. It was experimentally observed that the pump-down time to attain the base pressure ~10 ^-8 mbar was reduced by 62% compared to the unbaked chamber being pumped to this ultimate vacuum. The results were similar irrespective of whether the discharge cleaning medium is either hydrogen or helium. It was also experimentally established that a better ultimate vacuum could be achieved as compared to theoretically calculated ultimate vacuum with the help of discharge cleaning.