Analysis of Charge State Distribution by Non-Local Thermodynamic-Equilibrium Spin-Orbit-Split-Array Collisional Radiative Model

A collisional radiative model based on the spin-orbit-split-arrays is used to determine the charge state distribution of gold plasmas. The ab initio atomic structure code of Cowan and the spin-orbit-split-array model were used to calculate all the emission spectra of the different gold species, and a non-local thermodynamic-equilibrium model was coupled to calculate the ion populations at a given plasma density and electron temperature. The charge state distribution and other plasma parameters were determined by comparing the experimental spectra with the theoretical simulated soectra of gold plasmas.     

Analysis of asymmetry of the Dαemission spectra under the Zeeman effect in boundary region for D-D experiment on EAST tokamak

In 2015 campaign,deuterium atomic emission spectra(D_α)under the Zeeman effect in boundary region had been measured by a high resolution optical spectroscopic multichannel analysis(OSMA)system based on passive spectroscopy during the deuterium plasma discharge on EAST tokamak,and part of the works about the Zeeman effect on D_αspectra had already been done.However,the asymmetric phenomena of D_αemission spectra under the Zeeman effect were observed in process of analyzing the spectral data.To understand the asymmetric phenomena and acquire the useful local plasma information,an algorithm was proposed and used to analyze the asymmetry of the emission spectra under the Zeeman effect with all polarization components(πand±σ).In the algorithm,the neutral atoms were considered to follow the Maxwell distribution on EAST,and I+σ=I-σwas considered and set.Because of the line-averaged spectra along the viewing chord,the emission spectra were considered from two different regions:low-field side(LFS)and high-field side(HFS).Each spectral line was classified into three energy categories(the cold,warm,and hot)based on different atomic production processes in boundary recycling.The viewing angleθ(between the magnetic field B and the viewing chord),magnetic field B at two spectral emission positions(HFS and LFS)and the Doppler shift of all three energy categories of each spectral line were all considered in the algorithm.The effect of instrument function was also included here.The information of the boundary plasma were acquired,the reason for the asymmetric phenomena was discussed,and the boundary recycling during the discharge were studied in the paper.Based on fitting a statistical data of acquired fitting results,an important conclusion was acquired that the ratio of the spectral line intensity in HFS and LFS was proportional to the square of that of the corresponding magnetic field.     

X-ray spectra of high temperature tungsten plasma calculated with collisional radiative model

Tungsten is regarded as an important candidate of plasma facing material in international thermonuclear experimental reactor （ITER）, so the determination and modeling of spectra of tungsten plasma, especially the spectra at high temperature were intensely focused on recently. In this work, using the atomic structure code of Cowan, a collisional radiative model （CRM） based on the spin-orbit-split-arrays is developed. Based on this model, the charge state distribution of tungsten ions is determined and the soft X-ray spectra from high charged ions of tungsten at different temperatures are calculated. The results show that both the average ionization charge and line positions are well agreed with others calculations and measurements with discrepancies of less than 0.63% and 1.26%, respectively. The spectra at higher temperatures are also reported and the relationship between ion abundance and temperature is predicted in this work.     

Analysis of extreme ultraviolet spectral profiles of laser-produced Cr plasmas

Radiation from laser-produced plasmas was examined as a potential wavelength calibration source for spectrographs in the extreme ultraviolet(EUV) region.Specifically, the EUV emission of chromium(Cr) plasmas was acquired via spatiotemporally resolved emission spectroscopy.With the aid of Cowan and flexible atomic code(FAC) structure calculations,and a comparative analysis with the simulated spectra, emission peaks in the 6.5–15.0 nm range were identified as 3 p–4 d, 5 d and 3 p–4 s transition lines from Cr~(5+)–Cr~(10+)ions.A normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model were assumed for the spectral simulations, and used to estimate the electron temperature and density in the plasma.The results indicate that several relatively isolated emission lines of highly charged ions would be useful for EUV wavelength calibration.     

Characterization of the high—voltage pulsed discharge plasma of ammonia by emission spectroscopy

We have used optical emission spectroscopy to characterize the high-voltage pulsed discharge of ammonia.Ammonia was highly dissociated in the discharge at low pressures.More atomic nitrogen was generated as compared to the discharge of nitrogen gas at the same pressure of 0.8kPa.We discuss the elimination of the oxygen impurity in the ammonia discharge,and we estimate the time-dependent atomic excitation temperature and the electron density from the measured spectra.     

Influence of ambient pressure on properties and expansion of laser-induced plasma

A Nd:YAG pulsed laser is used to ablate HgCdTe target at different ambient pressures, the emission spectrum is detected by a time- and space-resolved diagnostic technique. It is found that the characteristics of time-resolved emission spectra are influenced by the pressure of background gas. A theoretical model is developed to investigate expansion mechanism of plasma, the time evolution of the propagation distances and the velocities of plasma plume are calculated by the model at pressures of 1.01×105, 1000, and 5 Pa, respectively. The calculated results are well consistent with the experimental data.     

Influence of ambient pressure on properties and expansion of laser-induced plasma

A Nd:YAG pulsed laser is used to ablate HgCdTe target at different ambient pressures, the emission spectrum is detected by a time- and space-resolved diagnostic technique. It is found that the characteristics of time-resolved emission spectra are influenced by the pressure of background gas. A theoretical model is developed to investigate expansion mechanism of plasma, the time evolution of the propagation distances and the velocities of plasma plume are calculated by the model at pressures of 1.01 × 105, 1000, and 5 Pa,respectively. The calculated results are well consistent with the experimental data.     

1.3 GHz单cell超导射频腔等离子体清洗放电研究(英文)

场致发射限制超导射频腔加速梯度增长。为了减少超导射频腔场致发射,在室温条件下,设计搭建了1.3GHz单cell超导射频腔等离子体清洗实验装置,开展等离子体清洗放电研究。使用CST软件模拟腔中的电磁场分布并且优化外部品质因数得到合适的放电条件。随着压强、前向功率和含氧量的变化,实验探讨了Ar/Ar-O₂放电的物理特征和电子激发温度的变化趋势。残余气体分析结果表明,Ar/O₂等离子体清洗能够消除腔体内表面的碳化物。Field emission limits the accelerating gradient increase in SRF cavities. In order to reduce field emission of SRF cavities, the plasma processing experimental setup of a 1.3 GHz single-cell SRF cavity is designed and built to carry out plasma processing discharge research at room temperature. The electromagnetic field distribution is simulated and the external quality factor is optimized to provide a suitable discharge condition using CST software. It is explored that the physical property of Ar/Ar-O₂ discharge and the variation trend of electron excitation temperature with the changes of pressure, forward power and O₂ content in experiment. The result of residual gas analysis indicates that Ar/O₂ plasma processing can eliminate the carbide of the inner surface of cavity.     

Analysis of the Zeeman effect on D_α spectra on the EAST tokamak

Based on the passive spectroscopy,the D_α atomic emission spectra in the boundary region of the plasma have been measured by a high resolution optical spectroscopic multichannel analysis(OSMA) system in EAST tokamak.The Zeeman splitting of the D_α spectral lines has been observed.A fitting procedure by using a nonlinear least squares method was applied to fit and analyze all polarization π and ±σ components of the D_α atomic spectra to acquire the information of the local plasma.The spectral line shape was investigated according to emission spectra from different regions(e.g.,low-field side and high-field side) along the viewing chords.Each polarization component was fitted and classified into three energy categories(the cold,warm,and hot components) based on different atomic production processes,in consistent with the transition energy distribution by calculating the gradient of the D_α spectral profile.The emission position,magnetic field intensity,and flow velocity of a deuterium atom were also discussed in the context.     

Rotational and Vibrational Temperatures of Atmospheric Double Arc Argon-Nitrogen Plasma

The spectroscopic technique is employed to study the emission of atmospheric argon-nitrogen plasma jet generated by an original dc double anode plasma torch. The molecular bands of the N^＋2 first negative system are observed at the torch exit and chosen to evaluate the rotational and vibrational temperatures in comparison with the simulated spectra. The excitation temperature （Texc ≈ 9600 K） is determined from the Boltzmann plot method. The results show that the rotational, vibrational, electron and kinetic temperatures are in good agreement with one another, which indicates that the core region of atmospheric double arc argon-nitrogen plasma jet at the torch exit is close to the local thermodynamic equilibrium state under our experimental conditions.     

激光诱导击穿空气等离子体时间分辨特性的光谱研究

空气等离子体的时间行为对空气环境下激光诱导等离子体形成过程的研究有重要意义.本文将纳秒Nd:YAG脉冲激光(1064 nm)聚焦于一个大气压的空气中,诱导其产生等离子体.利用具有纳秒时间分辨功能的PI-MAX-II型ICCD,采用时间分辨光谱方法,研究了大气环境下激光诱导等离子体的时间行为.大气环境下的激光诱导等离子体光谱广泛分布于300—900 nm范围内,并且是由带状光谱和线状光谱叠加而成的.根据美国国家标准与技术研究院原子发射谱线数据库,对等离子体光谱中的氧、氮、氢等元素的特征谱线进行了识别和归属.给出了激光诱导击穿大气等离子体光谱随时间演化的直观图像,根据空气等离子体发射谱线计算了等离子体电子温度和等离子体电子密度.这些结果对于提高在大气环境下进行的在线测量结果的准确性和精确性具有重要的科学意义.     

Micro-pinch formation and extreme ultraviolet emission of laser-induced discharge plasma

Extreme ultraviolet(EUV) source produced by laser-induced discharge plasma(LDP) is a potential technical means in inspection and metrology. A pulsed Nd:YAG laser is focused on a tin plate to produce an initial plasma thereby triggering a discharge between high-voltage electrodes in a vacuum system. The process of micro-pinch formation during the current rising is recorded by a time-resolved intensified charge couple device camera. The evolution of electron temperature and density of LDP are obtained by optical emission spectrometry. An extreme ultraviolet spectrometer is built up to investigate the EUV spectrum of Sn LDP at 13.5 nm. The laser and discharge parameters such as laser energy, voltage, gap distance,and anode shape can influence the EUV emission.     

Laser-induced plasmas in liquids for nanoparticle synthesis

Spatially and temporally resolved emission spectroscopy is used to study the major features of the onset and evolution of plasmas created by pulsed laser irradiation of targets immersed in liquids. It is shown that double pulse operation provides an enhanced rate of nanoparticle formation and increases the emission signal from the plasma atoms and ions owing to more efficient ablation of the target material. The main parameters (density of atoms, electron temperature and density) of laser-induced plasmas in liquids are estimated. The prospects of laser ablation in liquids as a method for producing nanoparticles are analyzed.     

短管螺旋波放电中等离子体参数测量和模式转化研究

对长度为45 cm的短放电管螺旋波放电等离子体进行了Langmuir探针、原子发射光谱以及集成电荷耦合检测器(ICCD)检测诊断,研究螺旋波等离子体的放电特性.Langmuir探针数据显示电子密度在射频功率增加过程中出现两次大幅增长,由此确认了放电模式的转换及螺旋波放电模式的出现.发射光谱测量结果与Langmuir探针测量的电子密度数据一致,发现Ar原子和Ar离子的谱线强度与放电模式变化有着密切相关性.而通过对不同放电模式的ICCD测量,获得射频功率吸收因放电模式转变而变化的方式,认为放电模式转换时电子行为和能量传递方式也发生着变化.     

基于连续谱的氩气纳秒脉冲放电中电子温度的研究

采用了一种针对针的放电结构,将其放置在一个高纯氩气的密闭腔室中,通过施加正极性的过电压产生可重复的大气压纳秒脉冲放电,并提出建立大气压放电的连续辐射模型来诊断氩气纳秒脉冲放电中的电子温度。实验利用电压和电流探头分别获取放电过程中的电压和电流波形图,其放电脉宽约为20 ns。通过消色差透镜、单色仪和ICCD等光学系统的组合来测量放电正柱区在不同时刻（0<t<20 ns）的时间分辨发射光谱。结果表明,放电中连续谱的强度随时间先增加（0<t<10 ns）后减小（10 ns<t<20 ns）,但是氩原子的谱线强度则随时间的增加而一直增大。研究表明连续谱强度与电子密度成正相关,因而电子密度随着时间也是先增加而后减小,这与放电电流的变化规律是完全一致的。根据连续谱模型拟合得到放电过程中（0<t<10 ns）的电子温度为(1.4±0.2) eV。随着驱动电压的下降（10 ns<t<20 ns）,电子温度逐步减小至0.9 eV。在0<t<10 ns中,激发态氩原子主要是由电子碰撞激发产生的,因而谱线强度随着电子密度的增加而增大。然后,随着电子温度的减小,Ar+₂复合反应速率激增,导致电子与离子的复合过程主导产生激发态氩原子,即谱线强度继续增大。通过加入0.5%的水蒸气以获取OH的振转光谱。实验发现,OH(A)的产生机制使其偏离玻尔兹曼平衡分布,本文采用了双温的OH(A-X)光谱模型来考察气体温度。在放电过程中,气体温度保持不变,大约为400 K。此外,水蒸气的加入使得短波长的连续谱发生显著增强。光谱分析认为H₂O在放电中能够解离产生H₂,继而与氩原子的亚稳态发生能量转移生成激发态H₂(a3Σ+_g)。H₂(a3Σ+_g)将会自发辐射跃迁到排除态H₂(b3Σ+_u),同时发射短波长的连续谱。由于短波长的连续谱对电子温度（T_e>1 eV）的响应较为灵敏,所以载气中少量的水蒸气将会对连续谱诊断电子温度带来较大的影响。     

Lichtemission gepulster Argon-Entladungen bei koaxialer Elektrodenanordnung

The spectrum of prompt and delayed light radiation was measured from a pulsed corona discharge in pure Argon. The prompt light consists of known Argon emission lines. The delayed radiation exhibits a band-like structure in the wavelength region between 300 and 400 nm and cannot be identified with known transitions in theA ^I orA ^II spectra. The decay time of this light is several orders of magnitude larger than that of the prompt component and is inversely proportional to the Argon pressure. Presumably Argon molecules in electronically excited states, which are mainly formed after the discharge, give rise to the delayed light and provide a mechanism to deexcite the metastable Argon atoms originating during the discharge.     

An Experimental and Theoretical Study of the Creation Plasma Process in dc Pulsed Discharges

An experimental study of the evolution along the creation process of the plasma parameters characterizing a dc pulsed Argon discharge has been developed. The diagnostic of these parameters is based on the I — V probe characteristic technique. The electron density evolution values so measured are in a good agreement with those obtained from a theoretical model of this process, so the validity of the assumptions involving the model are confirmed.     

发射光谱法对早期激光诱导铝合金等离子体诊断研究

对激光诱导等离子体参数进行诊断有多种方法,其中采用发射光谱法对其诊断是一种重要的方法。文中采用Nd∶YAG固态激光器,输出波长1 064 nm红外激光与铝合金样品相互作用,深入研究了铝合金等离子体产生早期(<1 μs)谱线轮廓、谱线强度、线背比、谱线半峰宽及位移等随时间演变规律。研究表明,激光与物质相互作用早期,电子数密度非常大,电子与离子及原子之间的相互作用非常强烈,谱线的Stark展宽效应非常明显,导致多重谱线重叠在一起,随时间演变,电子数密度及电子温度的降低,多重谱线的半峰宽越来越窄且谱线轮廓对称性越来越好。MgⅠ285.212 6 nm谱线强度早期逐渐增强,大约100 ns左右谱线强度达到最大值,然后谱线强度呈逐渐减小的趋势,这是由于等离子体产生早期,电子及离子占主导地位,故早期原子谱线强度较弱,随时间演变,电子与离子之间的复合,原子数密度逐渐增加,故原子谱线逐渐增强,达到最大值之后,由于等离子体激发温度的降低,故谱线强度逐渐减弱。以NIST波长位置为参考,等离子体产生的早期谱线发生了红移,连续背景强度随时间演变呈幂函数形式急剧递减,与之相反,谱线的连续背景强度与谱线强度相比,连续背景衰减的速度更为迅速,故导致谱线信背比随时间演变呈增大趋势,本研究对等离子体早期这些现象从理论角度进行了深入探讨。     

非平衡态Ti-H等离子体发射光谱的双温度诊断研究

单次脉冲工作的真空弧离子源,采用金属钛吸附氢形成的Ti-H固溶体作阴极,生成的等离子体同时包含金属钛和氢的成分,且在径向、横向以及时间尺度上都存在梯度,整个体系处于非平衡状态,不能用一个统一的温度来描述。假设由电子组成的子系统和由其他重粒子组成的子系统分别达到平衡,即Ti-H等离子体由电子温度和重粒子温度两个温度来描述,为双温度等离子体。采用Culdberg-Waage解离方程和Saha电离方程分别对系统中的分子解离和原子电离过程进行描述,结合等离子体电荷准中性条件,同时引入原子发射光谱这一无干扰的等离子体诊断方法,对Ti-H等离子体的温度和粒子数密度进行诊断。在MATLAB环境下,同时考虑金属Ti原子和一价Ti离子的电离,计算结果显示：根据谱线的斯塔克展宽确定的电子密度进行计算,除重粒子温度和氢气分子的数密度之外,其他的参数均可得到较准确的诊断结果;电子密度数值的准确性对计算结果有很大的影响;如果能够在计算之前确定重粒子温度,则可对Ti-H等离子体的温度和粒子数密度进行准确的定量分析。