Ti类氦Kα线在高温稠密等离子体中的漂移

采用离子球模型,通过自洽求解Dirac方程和Poisson方程,得到类氦Ti离子Kα线系的两条电偶极辐射光谱能量随不同等离子体环境的变化关系.同时分析了束缚电子交换能随等离子体环境的变化规律.结果表明：光谱能量漂移量随等离子体电子密度变化呈现出很好的线性关系.对此,拟合得到Ti类氦Kα线光谱能量漂移量随等离子体环境参数变化的公式,对探索高温高密度等离子体诊断方法具有一定意义. 关键词： 类氦离子 自洽场离子球模型 光谱漂移 等离子体诊断     

等离子体效应对类氦氖Kα线系电偶极辐射的影响

采用离子球模型，通过自洽求解Boltzmann方程和Poisson方程，得到类氦氖离子Kα线系的两条电偶极辐射光谱能量随等离子体环境的漂移.结果显示，Kα线系电偶极谱线随等离子体电子密度增大发生红移，红移量与等离子体电子密度有近似的正比关系；随着等离子体电子温度的降低，光谱红移对等离子体电子密度的敏感性增大.另外，所研究的两条谱线间的能量间隔随等离子体电子密度的增大而减小，减小量随等离子体电子密度的变化也呈现出近似的线性规律.值得注意的是，类氦氖Kα线系中两条电偶极谱线分别为互组合线与共振谱线，而其能量差就是1s2p(³P₁)的交换能，因此进一步发现能级中交换能将随等离子体环境变化的规律.所观察到的光谱红移和精细结构分裂在高密度等离子体中都有明显的变化，对探索高密度等离子体的诊断新方法有重要意义. 关键词： 光谱漂移 交换能 等离子体 类氦离子     

等离子体效应对类氦氖Kα线系电偶极辐射的影响

采用离子球模型,通过自洽求解Boltzmann方程和Poisson方程,得到类氦氖离子Kα线系的两条电偶极辐射光谱能量随等离子体环境的漂移.结果显示,Kα线系电偶极谱线随等离子体电子密度增大发生红移,红移量与等离子体电子密度有近似的正比关系;随着等离子体电子温度的降低,光谱红移对等离子体电子密度的敏感性增大.另外,所研究的两条谱线间的能量间隔随等离子体电子密度的增大而减小,减小量随等离子体电子密度的变化也呈现出近似的线性规律.值得注意的是,类氦氖Kα线系中两条电偶极谱线分别为互组合线与共振谱线,而其能量差就是1s2p(3P1)的交换能,因此进一步发现能级中交换能将随等离子体环境变化的规律.所观察到的光谱红移和精细结构分裂在高密度等离子体中都有明显的变化,对探索高密度等离子体的诊断新方法有重要意义.     

类氢氖在高温高密度等离子体中的光谱漂移

采用离子球模型,通过自洽求解Poisson方程和Dirac方程,得到氖的类氢离子低能级组态的能级能量随等离子体电子温度和电子密度的变化关系,进一步研究了等离子体电子温度和电子密度对光谱漂移的影响。结果表明：光谱漂移随着等离子体电子密度的增大而增大,随着电子温度的升高而减小;谱线精细结构分裂随着电子密度的增大而减小,随着电子温度的升高而增大。等离子体对束缚电子的屏蔽是决定光谱漂移的主要原因。这些变化规律不仅对等离子体光谱模拟结果产生影响,而且使实验上观测光谱的相对或绝对漂移成为可能,从而为高密度等离子体诊断的新方法提供了理论依据。     

类氢氖在高温高密度等离子体中的光谱漂移

 采用离子球模型,通过自洽求解Poisson方程和Dirac方程,得到氖的类氢离子低能级组态的能级能量随等离子体电子温度和电子密度的变化关系,进一步研究了等离子体电子温度和电子密度对光谱漂移的影响。结果表明：光谱漂移随着等离子体电子密度的增大而增大,随着电子温度的升高而减小;谱线精细结构分裂随着电子密度的增大而减小,随着电子温度的升高而增大。等离子体对束缚电子的屏蔽是决定光谱漂移的主要原因。这些变化规律不仅对等离子体光谱模拟结果产生影响,而且使实验上观测光谱的相对或绝对漂移成为可能,从而为高密度等离子体诊断的新方法提供了理论依据。     

带有射频偏压源的感性耦合Ar/O2/Cl2等离子体放电的混合模拟研究

在刻蚀工艺中,通常会在感性耦合等离子体源的下极板上施加偏压源,以实现对离子能量和离子通量的独立调控.本文采用整体模型双向耦合一维流体鞘层模型,在Ar/O₂/Cl₂放电中,研究了偏压幅值和频率对等离子体特性及离子能量角度分布的影响.研究结果表明:当偏压频率为2.26 MHz时,随着偏压的增加,除了Cl^-离子和ClO⁺离子的密度先增加后降低最后再增加外,其余带电粒子、O原子和Cl原子的密度都是先增加后基本保持不变最后再增加.当偏压频率为13.56和27.12 MHz时,除了Cl^-离子和Cl₂⁺离子外,其余粒子密度随偏压的演化趋势与低频结果相似.随着偏压频率的提高,在低偏压范围内(<200 V),由于偏压源对等离子体加热显著增加,导致了带电粒子、O原子和Cl原子的密度增加;而在高偏压范围内(>300 V),由于偏压源对等离子体加热先减弱后增强,导致除了Cl₂⁺离子和Cl^-     

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采用等离子体分层模型,利用WKB近似研究了离子回旋共振加热(ICRH)天线发射谱n||对离子回旋波在托卡马克等离子体的表面功率反射系数、吸收衰减的影响,数值模拟了不同天线发射谱n||条件下快波少数离子加热的效果.模拟结果表明,当其它实验参数一定时,ICRH天线发射合适的n||能提高天线与等离子体的耦合效率,增强少数离子加热的效果.     

德拜模型和自洽场离子球模型屏蔽效应的比较

本文分别用德拜模型和自洽场离子球模型研究了等离子体中类氦铝离子1snp [n=2-3](~1P_1)原子态的能级移动量随电子密度的变化规律,并对二者所计算的能级移动量进行了比较.结果表明:能级移动量随着耦合强度的增大而增大;当耦合强度为一定值时,能级移动量随着电子密度的升高而增大.当电子密度小于1.0×10~(23) cm~(-3)时,不同耦合强度下德拜模型和自洽场离子球模型所计算的能级移动量几乎是相同的.当电子密度大于1.0×10~(23) cm~(-3)时,随着耦合强度的增大,1s2p (~1P_1)原子态的德拜模型的能级移动量由小于自洽场离子球模型的能级移动量,逐渐转变为大于自洽场离子球模型的能级移动量;1s3p (~1P_1)原子态的德拜模型的能级移动量始终小于自洽场离子球模型的能级移动量.     

CH4/H2和CH4/He体系等离子体发射光谱分析

 在CH₄/H₂和CH₄/He和CH₄/He两种系统中,利用光学发射谱技术对螺旋波放电产生低压甲烷等离子体内活性粒子的光学发射特征进行了原位诊断。在实验中,两种体系下同时都测得的主要荷电粒子为CH,Ha,Hb,Hg以及H2等。研究了各实验参数对这些活性粒子CH, Ha,Hb以及Hg的发射光谱强度的影响。结果表明：在CH₄/H₂体系下,随着射频功率的增大,Ha,Hb,Hg以及CH基团的相对强度都随着增加,而当放电气压变化时它们都呈现先增大而后减小的趋势。在CH₄/He体系下,随射频功率的增加,Ha,Hb,Hg以及CH相对强度变化的总体趋势也都是先增加而后减小,当工作气压增加时,Ha,Hb以及Hg的相对强度变化也是呈现先增大而后减小,但CH基团的相对强度却是逐渐减小的;这些结果为等离子体沉积各种薄膜过程的理解及制备工艺参数的调整提供了参考。     

射频功率对辉光放电H2/C4H8等离子状态的影响

采用辉光放电技术和等离子体质谱诊断技术,研究了H₂/C₄H₈混合气体等离子体中正离子成分及主要正离子能量随射频功率的变化规律,并分析了H₂/C₄H₈混合气体主要的离解机理和形成过程.研究表明:随着射频功率的增加,碳氢碎片离子的浓度增加,在20 W时达到最大值,25 W后有所减小.当射频功率小于10 W时,H₂/C₄H₈混合气体等离子体中C₄H₉⁺相对浓度最大,当功率大于或等于10 W时,C₃H₃⁺相对浓度最大.随着射频功率的增大,碳氢碎片离子的能量逐渐增加.对H₂/C₄H₈混合气体等离子体的组成与能量进行的定性分析,将为H₂/C₄H₈混合气体辉光放电聚合物涂层工艺参数优化提供参考.     

Relativistic calculations of fine-structure energy levels of He-like Ar in dense plasmas

The fine-structure energy levels of 1s2s and 1s2p atomic states for the He-like Ar ion immersed in dense plasmas are calculated. The ion sphere model is used to describe the plasma screening effect on the tested ion. The influences of the hard sphere confinement and plasma screening on the fine-structure energy levels are investigated respectively. The calculated results show that the confined effect of the hard sphere on the fine-structure energy levels increases with decreasing hard sphere radius, and the plasma screening effect on the fine-structure energy levels increases with the increase of free electron density. In dense plasmas, the confined effect of the hard sphere on the fine-structure energy levels can be neglected generally, compared with the contribution from free electron screening. An interesting phenomenon about the energy level crossing is found among 1s2s(~1S_0) and 1s2p(~3P_(0,1)) atomic states. The results reported at the present work are useful for plasma diagnostics.     

Spectral lines in hot dense matter

An algorithm is presented for the computation of photoabsorption cross sections at arbitrary temperature and matter density. The “average atom” model is refined to give an approximaate account for the different ionization stages. The broadening of spectral lines is accounted for in a simple approximation. Calculations are presented for the beryllium and germanium plasmas in the frequency region of spectral lines.     

Spectral line shapes modeling in turbulent plasmas

In this work we investigate the influence of low frequency turbulence on Doppler spectral line shapes in magnetized plasmas. Low frequency refers here to fluctuations whose typical time scale is much larger than those characterizing the atomic processes, such as radiative decay, collisions and charge exchange. This ordering is in particular relevant for drift wave turbulence, ubiquitous in edge plasmas of fusion devices. Turbulent fluctuations are found to affect line shapes through both the spatial and time averages introduced by the measurement process. The profile is expressed in terms of the fluid fields describing the plasma. Assuming the spectrometer acquisition time to be much larger than the turbulent time scale, an ordering generally fulfilled in experiments, allows to develop a statistical formalism. We proceed by successively investigating the effects of density, fluid velocity and temperature fluctuations on the Doppler profile of a spectral line emitted by a charge exchange population of neutrals. Line shapes, and especially line wings are found to be affected by ion temperature or fluid velocity fluctuations, and can in some cases exhibit a power-law behavior. These effects are shown to be measurable with existing techniques, and their interpretation in each particular case would rely on already existing tools. From a fundamental point of view, this study gives some insights in the appearance of non-Boltzmann statistics, such as Lévy statistics, when dealing with averaged experimental data.     

Probing hot and dense laser-induced plasmas with ultrafast XUV pulses

In this Letter, we demonstrate the instantaneous creation of a hot solid-density plasma generated by focusing an intense femtosecond, high temporal contrast laser on an ultrathin foil (100 nm) in the 10(18) W/cm2 intensity range. The use of high-order harmonics generated in a gas jet, providing a probe beam of sufficiently short wavelengths to penetrate such a medium, enables the study of the dynamics of this plasma on the 100 fs time scale. The comparison of the transmission of two successive harmonics permits us to determine the electronic density and the temperature with accuracies better than 15%, never achieved up to this date in the regime of laser pulses at relativistic intensity.     

Ionization state and bound level populations in hot,dense plasmas

The ionization state and bound level populations in hot, dense plasmas are studied in the average atom approximation. Bound level energies are fixed self-consistently with the complete set of population numbers, using pre-existent Hartree-Fock calculations. We present a pressure- ionization scheme that gradually merges bound electrons into the continuum. To solve the nonlinear algebraic system of equations of the model, we have derived an efficient iterative algorithm. Results are shown for aluminum and iron.     

高温稠密等离子体的分子动力学模拟

将平均原子模型和密度泛函理论相结合,发展了一个计算高温稠密等离子体中离子之间平均相互作用势的理论模型. 利用平均原子模型考虑了高温稠密物质中电子的激发和密度效应对电子结构的影响,利用动能和交换相关能的局域密度泛函近似计算离子之间的平均相互作用. 基于发展的相互作用势模型,开展了分子动力学模拟,研究了高温稠密Al和Fe等离子体的状态方程.     

Spectral line formation in dense large-gradient plasma

The positions and profiles of x-ray spectral lines emitted from well characterized laserproduced plasmas have been investigated. The red shifts observed for higher members of the aluminum Lyman series are consistent with theoretical predictions of the line shifts in hot dense plasmas. The experimentally observed profiles of Al XIII Ly_a line are interpreted by modeling the radiative transport through plasma with large transverse gradients. The presented results originated from collaborative effort of the research groups from the Institute of Physics, Prague, University of Jena and University of Oxford. This work was supported by the Grant Agency of the Czech Republic under Grant No. 202/97/1186.