HL—1装置杂质清除率的研究

本文比较了ECR,AC和TDC纯H_2放电清洗,TDC+ECR(AC)纯H_2组合放电清洗和ACH_2+Kr(Xe,Ne)混合气体放电清洗对HL-1装置真空壁的清洗效果;总结了1984—1989年度各种壁条件下,HL-1装置杂质平均清除率;从气体动力学方程出发,分析了实验结果。     

预试环中H_2及掺杂甲烷的辉光放电清洗

本文给出了在预试环中产生和维持辉光放电的基本参数、氢气(H_2)及氢气掺杂甲烷(H_2/CH_4)辉光放电清洗过程中的质谱分析结果以及氢气辉光放电清洗处理后的样品表面SIMS(二次离子质谱)结果,并进行了讨论。     

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。     

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建立了烘烤出气和辉光放电清洗(GDC)出气的物理模型,研究了装置器壁的烘烤出气和辉光放电清洗出气特点.烘烤出气是体出气,出气过程满足扩散方程;GDC出气是溅射脱附过程,它主要是器壁表面的溅射诱导出气.由此分析了HL-1M装置的烘烤出气和辉光放电清洗出气特点,得出了一些经验公式.     

托卡马克装置器壁锻炼及其机制分析

本文回顾了托卡马克装置器壁锻炼技术的发展,用有关的低压气体放电原子和分子过程结合器壁表面成分分析,讨论了清洗放电化学反应机制。     

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。     

HL-1装置中的等离子体与器壁相互作用

本文对HL-1装置欧姆加热放电时,等离子体—器壁相互作用进行了实验研究。质谱分析定性地指出,主要气相杂质H_2O来自零级表面化学反应,CH_4来自多步骤合成表面化学反应,CO(CO_2)则来自碰撞表面化学反应。收集探针的表面分析显示出,Mo,Cr和Ni等为主要的重杂质;蒙特卡罗模拟分析给出了氢粒子注入硅探针的特征深度和其动力温度的拟合直线关系式。     

常温下氢气声转动弛豫模型研究

氢气声弛豫过程主要由氢气分子的转动弛豫决定.然而,当前大部分声弛豫模型是基于气体分子的振动弛豫,并不适用于氢气.本文利用理想气体焓变与定压热容的关系,提出了一种基于氢气分子转动的弛豫模型,并讨论了转动弛豫和振动弛豫的相似与不同.该模型不仅适用于氢气,还能够和其他气体的振动弛豫模型相结合求解混合气体的声弛豫吸收谱和声速频谱.仿真结果表明,对于H_2,N_2/H_2,CO_2/H_2等气体,该模型生成的声速、声弛豫谱曲线与实验数据符合.本模型为包含氢气的混合气体声学探测提供了一个有效的理论模型.     

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开发了氢气甚高频(60MHz)容性耦合放电的PIC/MC模型.在模型中考虑了带电粒子(e,H+,H2+,H3+)与H2的21种碰撞反应过程,模拟了氢气甚高频放电射频电场和电势分布以及电子和氢离子(H+,H2+,H3+)粒子密度和平均能量分布,并与频率为13.56MHz的放电结果进行了比较.结果表明,相对于频率13.56MHz的放电,氢气甚高频放电等离子体电势增高,导致两电极附近的电场增强;另外,两鞘层厚度变窄并且电子和H3+离子平均能量减小,其总密度却增加.H3+离子为氢气甚高频放电空间的主要离子,H2+离子密度比H3+离子小约2～3个数量级.     

D2及高浓度H2／CH4辉光放电

D_2辉光放电实验的目的旨在进一步了解辉光放电清除水的机制,弄清辉光放电清洗时,高本底H_2与质谱仪中离子源反应生成H_2影响质谱仪分析的情况。实验是在FY-I装置(异形截面环流器)上进行的,装置结构见文献[2]。实验安排与预试环上进行的实验大致相同。重水(D_2O)在相对净化的氢纯化器内电解后,生成D_2(氘)经压电晶体阀控制输入。     

微晶硅薄膜沉积过程中的等离子体光学与电学特性研究

采用空间分辨光发射谱和傅里叶变换功率阻抗分析仪研究了衬底偏压和辉光功率对微晶硅薄膜沉积过程中的等离子体光学与电学特性的影响.研究表明：在交流偏压(AC)、悬浮(floating)、负直流加交流(-DC＋AC)偏压下,Hα发射强度空间分布规律相似,平均鞘层长度相等;正直流加交流(＋DC＋AC)偏压和接地(grounded)时Hα发射强度显著增强,并存在双峰(double layers)现象.增大功率,Hα发射强度也随着增大,并在17W与22W之间产生跳变.电学测试发现功率增大,等离子体电阻降低,电抗降低,电 关键词： 等离子体 光发射谱 衬底偏压 辉光功率     

石蜡液面离子风的研究

研究了常压空气中针-石蜡液面 50Hz 交流电晕放电离子风特性。交流电晕离子风能够引起液体石蜡 显著变形,随着电压升高,变形从漏斗状发展到盆状。在石蜡层厚度为 5mm 时,盆状变形最大,深度达到 5.3mm, 最大作用范围半径 18.8mm,变形产生的压强达到 48.9Pa,远远超过直流针-水电晕放电情况。随着电压升高,从 电晕放电过渡到流注放电时盆状变形依然存在,这一点明显不同于直流针-水电晕放电。研究表明交流电晕离子风 具有优良的驱动绝缘液体介质的巨大潜力。     

Nitrogen dissociation and its excitation/vibrational temperature with hydrogen admixture in 50 Hz DC discharge

Trace rare gas optical emission spectroscopy (TRG-OES) is carried out to determine the excitation temperature, vibrational temperature, dissociation fraction and nitrogen (N) atom density in 50?Hz active screen cage nitrogen plasma, as a function of discharge parameters (current density and fill pressure) and hydrogen concentrations. The excitation temperature is determined from Ar–I emission lines and is found to increase with hydrogen mixing. In a similar fashion, the vibrational temperature of second positive system is determined and found to have increasing trend with hydrogen addition. The dissociation fraction increases with hydrogen concentration up to 40% H₂ in the nitrogen plasma, so as the nitrogen atom density.     

Formation of reactive species in gliding arc discharges with liquid water

The effects of gas composition on gliding arc (glidarc) electrical discharge reactors with pure water have been studied. The glidarc reactors utilized AC electrical discharges with two different electrode configurations. In one case a set of two stainless steel electrodes connected to a single power supply was placed in the gas phase over the liquid surface (power=250–300 W, maximum voltage=12 kV). The second experimental arrangement utilized a reactor with a set of three stainless steel electrodes supplied by two identical high-voltage transformers, where the electrodes were placed over the water surface or with the water sprayed directly in the plasma formed between the electrodes (power=500–600 W, maximum voltage=12 kV). The variation of pH and conductivity and the formation of hydrogen peroxide, ozone, nitrate, and hydrogen were measured. The effects of the type of gas, including pure oxygen, pure nitrogen, and dry air, were determined.     

Optical emission spectroscopy of 50 Hz pulsed dc nitrogen–hydrogen plasma in the presence of active screen cage

The N₂-H₂ plasma gas mixture, generated in a 50?Hz pulsed dc discharge system with active screen cage, is characterized by optical emission spectroscopy (OES), as a function of gas pressure, the fractions of hydrogen and current density. The N₂ dissociation degree and N atomic density was measured with actinometery where argon gas is used as actinometer. It was shown that the increase in hydrogen fraction enhances the dissociation of N₂, until the maximum of 40%. The excitation temperature is determined from Ar-I emission line intensities by using the simple Boltzmann plot method. The dissociation fraction and excitation temperature is found to increase with hydrogen mixing in nitrogen plasma.     

超声喷流氩氢混合团簇特性研究

利用瑞利散射方法研究了超声喷流Ar-CH4混合团簇和超声喷流Ar-H2混合团簇的特性.通过测量不同混合比例和不同背压下所形成混合团簇的散射信号发现,当用Ar气和CH4的混合气体进行超声喷流时很容易形成Ar-CH4混合团簇,当Ar气含量为50%时混合团簇尺度最大且大于相同气压下纯Ar团簇尺度和纯CH4团簇尺度.实验发现,与纯H2团簇只能在低温条件下获得不同,常温下即可形成Ar-H2混合团簇,实现了常温下含氢团簇的获取,从而有效降低了制备成本.在H2含量大于40%时混合团簇开始形成并在60%时达到最大尺度.含氢(氘)混合团簇在氢(氘)团簇的基础上引入了更重的异核Ar元素,在激光氘团簇聚变实验中它将进一步加速氘离子从而获得更高的能量,并具有更高的中子产额和聚变效率.     

Cathode-sheath driven low-speed aerodynamic flow actuation using direct-current surface glow discharges

Flow actuation by a continuous/pulsed, direct-current (DC) surface glow discharge is explored. The discharge comprises an array of pin electrode pairs flush mounted on a dielectric actuator surface that lies adjacent to stagnant air. Strong electrostatic fields produced in the cathode sheath region of the discharge provides a motive force on the ions which in turn drag the background gas resulting in directed air flow from the anode to the cathode. The induced flow velocity is estimated by particle image velocimetry (PIV) at 10 Hz with TiO₂ seeding. For a pulsed DC discharge with peak power of 5 W per electrode pair, the induced flow velocity reaches peak values of about 1.7 m/s which is comparable to dielectric-barrier discharge (DBD) or corona discharge actuators. The actuation effect quantified by the magnitude of induced velocity increases as the pulse frequency increases from 0 to 1 kHz. The actuation effect decreases for further increase in frequency above 1 kHz. Decreased actuation effect at high frequency is accompanied by structural change in the discharge. At fixed frequency of 1 kHz, flow actuation effect is highest for a square wave pulse with a duty cycle of 50% indicating that pulsed DC discharges produces better actuation than continuous DC with a corresponding reduction in energy consumption.     

重频XeF蓝绿激光技术

 利用表面放电光泵浦技术,研制了重频XeF(C-A)激光器,运行频率达到10 Hz。研究了运行频率、气体流量对激光输出能量稳定性的影响,分析了影响输出稳定性的主要因素,实验结果表明,提高气流量可有效改善重频输出能量的稳定性。同时,还给出了优化实验条件下不同运行频率连续20个脉冲较为理想的输出结果。运行频率分别为1,2,5 Hz时,输出能量稳定性较好,输出能量大于4.0 J;气流量大于53 L/s时,10 Hz重频运行的输出稳定性已显著提高,平均输出能量也达到1.8 J。     

Two-stage electrostatic precipitator with co- and counter-flow particle prechargers

Lab-scale, two-stage electrostatic precipitation system comprising of precharging stage, in which PM2.5 particles are electrically charged, and collection stage, in which the charged particles are removed from the flowing gas by electric field, was investigated in this paper. Two types of electrostatic particle prechargers were compared with respect to the collection efficiency of the system: (1) co-flow precharger, in which ionic current was generated co-currently with the gas conveying the particles, and (2) counter-flow precharger, in which ionic current was generated oppositely to the flowing gas. In each case, the electrodes of precharger were supplied with DC or AC high-voltage in order to compare the effect of discharge mode on the collection efficiency of two-stage electrostatic precipitator. The collection stage was formed by two parallel-plate electrodes connected to DC high voltage source. Plate electrodes without discharge points (spikes) are corona-free electrodes, which prevent the collection stage from electrical discharges, and reduce the probability of back discharge ignition. The back discharge decreases collection efficiency of conventional electrostatic precipitators.It was concluded that the co-flow electrode configuration of the precharger, supplied with DC high voltage, has the highest total number collection efficiency for PM2.5 particles, higher than 95% and the mass collection efficiency larger than 99%. The counter-flow precharger provided only about 90% number collection efficiency of two-stage electrostatic precipitator. It was also shown that by AC electrode excitation, the collection efficiency of the system is lower than for DC supply. The two-stage electrostatic precipitators allowed obtaining higher fractional collection efficiency for PM2.5 particles than other conventional systems and can be recommended as highly effective devices for gas cleaning in power plants or cement industry.     

Effect of leakage transformer on laser power and mode pattern of CO2 laser excited by 60 Hz AC discharges

The 60 Hz AC discharges generated by a leakage transformer instead of an isolation one, which is usually used in the power supply of DC CO₂ laser, are employed as a pumping source in this experiment. The laser performance characteristics as functions of pressure and discharge current have been investigated. The maximum laser power is about 40 W at conditions of 18 Torr and 35 mA. The output power is not less than that of DC discharge at the same condition. In addition, the laser outputs of 60 Hz AC discharges obtained by different transformers such as a leakage type and an isolation one have been measured. It was found that the laser power obtained by the leakage transformer is saturated at the higher current compared with the isolation transformer.