Thermodynamic and Transport Properties of Ablated Vapors of PTFE, Alumina, Perspex, and PVC in the Temperature Range 5000-30 000 K

Values of density, specific heat, enthalpy, sonic velocity, viscosity, thermal, and electrical conductivities have been calculated for the plasmas of PTFE, alumina, Perspex, and PVC for temperatures from 5000 to 30 000 K. Equilibrium particle concentrations and degrees of ionization are calculated using the minimization of Gibbs free energy, and transport properties are calculated using the Chapman-Enskog approximations.     

部分电离金属钛和银等离子体输运性质的计算

金属等离子体的组分为计算热力学、光学和辐射输运特性研究提供了基本的输入参数.为获得此参数,本文用部分电离等离子体模型,在考虑金属发生三次电离,以及电子与中性粒子的极化作用、离子与离子之间、电子与离子之间、电子与电子之间库仑相互作用下,计算得到了等离子体组分,进而用线性响应理论计算了金属钛和银的电导率.并与已有的实验数据进行了比较,验证了模型的可靠性.在此基础上进一步预测了密度在0.001—2.0 g/cm³、温度在1.5×10⁴—2.5×10^{4关键词： 等离子体 线性响应理论 电离度 输运系数}     

一种计算氩等离子物态方程的简单模型

将Thomas-Feimi统计模型电离势的数值结果进行函数逼近，给出一个便于近似数值求解的解析表达式和计算电离度的近似计算方法，计算了Ar元素LTE情况下的电离度和物态方程，结果与Saha模型的计算结果和实验结果符合较好.所提出的简单模型也适用于计算混合物物态方程，可以在电磁发射技术领域中的强电离等离子体中有广阔的应用前景. 关键词： 等离子体 物态方程 电离势 电离度     

Ionization Equiibrium and Composition of a Dense Partially Ionized Metal Plasma

In the present work we determine the ionization equilibrium of dense tungsten, aluminum and iron plasmas by solving the Saha equations with corrections due to non‐ideality. The lowering of the ionization potentials is calculated on the basis of effective potentials by taking screening and quantum effects into account (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical Properties of Model Moderately Coupled Plasmas

We review our approach to the modelling of optical properties of model moderately coupled plasmas. On the basis of the classical theory of moments the external and internal dynamic conductivities and the reflectivity coefficient of a model hydrogen moderately coupled plasma are determined using all known exact relations and sum rules. The sum rules which are the power frequency moments of the loss function are calculated using the Deutsch effective potential and the hypernetted chain equations. MD simulation data are used and numerical simulations are suggested (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Anomalous kinetics of plasmas in high-power radiation fields

Transport equations are obtained in the nine-moment approximation for plasmas in intense radiation fields where the amplitude of the electron oscillations in the electromagnetic field exceeds the thermal speed. It is shown that for plasmas with a high degree of ionization, Z, the electron thermal conductivity is higher by approximately a factor of Z. The change in the frictional force on electrons colliding with ions owing to the effect of the radiation field leads to the possibility of electron acceleration and to a change in the sign of the dc and low-frequency electrical conductivities. Zh. éksp. Teor. Fiz. 111, 478–495 (February 1997)     

Towards Stronger Coulomb Coupling in an Ultracold Neutral Plasma

Ultracold neutral plasmas are strongly coupled Coulomb systems that are generated by photoionizing lasercooled atoms close to the ionization threshold. The strong coupling parameter Γ is limited at times later than ～100 ns by disorder‐induced heating. A recent simulation predicted that higher values of Γ can be realized in ultracold neutral plasmas if the plasma ions are excited to higher ionization states. In this paper we present recent results from an experiment that increases the strong coupling of an ultracold neutral plasma by promoting the plasma ions to the second ionization state. Using laser‐induced fluorescence we map out the ion velocity distribution of the Ca⁺ ions in a partially doubly ionized plasma and show that the heating due to the second ionization depends on the timing of the second ionization laser pulses. We compare our results to MD simulations, which estimate that Γ increases from approximately 2.5 to 3.6. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

非理想氩等离子体电子密度和平均离化度理论研究

用SHM模型计算了非理想Ar等离子体在温度T为2.0eV、密度ρ为0.01~0.5g•cm-3的电子密度和平均离化度。研究了非理想Ar等离子体电子密度和平均离化度随温度、密度的变化规律,得到了在温度T为2.0eV、密度ρ为0.01~0.5g•cm-3非理想Ar等离子体的平均离化度小于0.5的结果。这表明非理想Ar等离子体的平均离化度非常低,大量的Ar仍然处于非电离状态。计算的结果还显示了平均离化度随等离子体密度ρ增加而减小的特征,并分析了减小的原因。     

氩等离子体物态方程的TF简化模型

对于高温高压下氩等离子体的电离度和物态方程,本文给出了一种基于Thomas-Feimi(TF)统计模型的简化计算新方法:首先将TF模型电离势的数值结果进行函数逼近,给出一个便于数值求解的计算电离度的近似计算方法,并由此计算了局部热动平衡下的氩等离子体在10～1000 eV高温范围内的物态方程.计算结果与国外报道的其他几种理论模型的计算结果均符合很好,与实验值也吻合较好.本文所提出的简单模型也适用于计算混合物物态方程,可以在电磁发射技术领域中的强电离等离子体中有更为广阔的应用前景.     

含温有界原子模型下电子与离子碰撞激发和电离截面的理论研究

采用扭曲波玻恩交换近似方法，在自由原子模型下计算了电子与离子碰撞激发、电离截面，计算值与实验一致；在含温有界平均原子模型下，系统研究了不同温度、密度等离子体中离子的电子碰撞直接电离截面，发现由于温度、密度效应导致离子的能级漂移，引起等离子体中离子的碰撞电离截面比自由原子情形发生较大变化. 关键词： 平均原子模型 扭曲波波恩交换近似 电离截面     

Elementary Many‐Particle Processes in Plasma Microfields

The effect of electric and magnetic plasma microfields on elementary many‐body processes in plasmas is considered. As detected first by Inglis and Teller in 1939, the electric microfield controls several elementary processes in plasmas as transitions, line shifts and line broadening. We concentrate here on the many‐particle processes ionization, recombination, and fusion and study a wide area of plasma parameters. In the first part the state of art of investigations on microfield distributions is reviewed in brief. In the second part, various types of ionization processes are discussed with respect to the influence of electric microfields. It is demonstrated that the processes of tunnel and rescattering ionization by laser fields as well as the process of electron collisional ionization may be strongly influenced by the electric microfields in the plasma. The third part is devoted to processes of microfield action on fusion processes and the effects on three‐body recombination are investigated. It is shown that there are regions of plasma densities and temperatures, where the rate of nuclear fusion is accelerated by the electric microfields. This effect may be relevant for nuclear processes in stars. Further, fusion processes in ion clusters are studied. Finally we study in this section three‐body recombination effects and show that an electric microfield influences the three‐body electron‐ion recombination via the highly excited states. In the fourth part, the distribution of the magnetic microfield is investigated for equilibrium, nonequilibrium, and non‐uniform magnetized plasmas. We show that the field distribution in a neutral point of a non‐relativistic ideal equilibrium plasma is similar to the Holtsmark distribution for the electrical microfield. Relaxation processes in nonequilibrium plasmas may lead to additional microfields. We show that in turbulent plasmas the broadening of radiative electron transitions in atoms and ions, without change of the principle quantum number, may be due to the Zeeman effect and may exceed Doppler and Stark broadening as well. Further it is shown that for optical radiation the effect of depolarization of a linearly polarized laser beams propagating through a magnetized plasma may be rather strong. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Composition and Thermodynamic Properties of Dense Alkali Metal Plasmas

In this work composition and thermodynamic properties of dense alkali metal plasmas (Li, Na) were investigated. Composition was derived by solving the Saha equations with corrections due to nonideality. The lowering of the ionization potentials was calculated on the basis of pseudopotentials by taking screening and quantum effects into account (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Radiation Emission of Fast Electrons in Collisions with “Ion‐Sphere” in Dense Plasmas

Radiative emission of fast electrons in collision with an “ion‐sphere” electron distribution in dense plasmas is under consideration. The electron structure of the ion sphere is calculated ab initio using self‐consistent solution of both bound and free electron distribution inside the sphere. Two radiation channels are included: emission of the colliding electron itself in static potential (conventional or static Bremsstrahlung) and the emission of “ion sphere” medium due to its polarization by the colliding electron (polarization Bremsstrahlung). The last one is calculated in the frame of local plasma density approximation. Interference between conventional and polarization Bremsstrahlung is taken into account. It is shown that spectral cross section of the process has characteristic features depending on plasma density and ionization stage of plasma ions. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Plasma–wall transition in the quasi‐neutral region of collisional and stationary plasmas in a magnetic field enclosed by totally absorbing walls

The structure of stationary electron–positive ion plasmas in spatially limited vessels is analysed with special emphasis on the plasma–wall transition using different physical models. Basic investigations are carried out in a two‐fluid model, which is supplemented by ionization and oblique magnetic fields. Collisions between the two particle species were taken into account, as well as the dependence of the collision frequency on the particle density. For the case of non‐vanishing magnetic fields, electrons are not assumed to be in Boltzmann equilibrium. The investigated one‐dimensional domain is limited by totally absorbing walls on each side. Stationary states are considered, in which ionization sources balance the wall losses. To also take into account kinetic effects, simulations in a quasi‐neutral hybrid model are performed. The hybrid model assumes the electrons as a fluid and treats the ions using a particle‐in‐cell (PIC) method. A new way of ensuring the Bohm criterion is used by removing those superparticles impeding the wall. When comparing the results, both models reveal differences, especially when ionization from a resting neutral gas or weakly magnetized plasmas is considered, causing a broadening of the ion distribution or anisotropy effects, respectively.     

Classical Molecular Dynamics Model for Coupled Two‐Component Plasmas – Ionization Balance and Time Considerations

The dynamic properties of ion‐electron two‐component plasmas (TCP) are studied by using classical molecular dynamics (MD) simulations. There is a variety of time dependent and structural results that MD is able to provide in complement to other methods, e.g., useful micro‐field sequences can be generated. The method deals with some specific difficulties: the mass ratio between ions and electrons enforces very small time‐steps appropriate to follow electrons motion while, ions must move significantly in order to build, self consistently, their spatial structure. This results in expensive simulations. Electron trajectories are trapped and de‐trapped with multiple electron collisions around ions resulting in the occurrence of quasi metastable bound electron states. An analysis of micro‐fields at neutral in a hydrogen plasma reveals the need to consider a complete hierarchy of time scales extended typically over 7 order of magnitude, i.e., from a time‐step: ～10^‐19s, to a time required to obtain statistical averages, ～10^‐11s. In order to extend the MD capabilities in representing real coupled plasmas a classical ionization/recombination process has been implemented allowing to follow the evolution of plasmas involving several ion stages and model the ionization balance. Here again TCP simulations deal with extended time‐scale providing information about relaxation of non equilibrium plasma states (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spectra—A model for K-shell spectroscopy

X-ray spectroscopy is a powerful tool for understanding the kinetics of highly ionized plasmas. Its usefulness depends on the accuracy of the model used in analyzing spectra. We have developed a computer code for modeling and analyzing plasmas which is highly accurate as well as fast and easy to use. It produces synthetic spectra for hydrogen-like and helium-like ions at arbitrary density and temperature. Populations are calculated from rate equations including all relevant collisional and radiative process. The level populations of the hydrogen, helium and lithium-like ionization stages are calculated explicitly; those of all other ionization stages are lumped into one level. The microfield distribution and the shape of the line profiles are determined using detailed calculations. The code includes graphics to plot line ratios and synthetic spectra, and to do on-line analysis of experiments. The usefulness of this technique is demonstrated by analyzing the spectra from three different experiments: a laser irradiated aluminum disk; a neon gas puff pinch; and a laser imploded gas microballon.     

全电离氢等离子体的电导率

主要研究了全电离等离子体的散射相移、传输截面和电导率.相移应用WKB方法计算,且计算结果与使用精确计算方法得到的结果非常一致,证明了所用计算方法的正确性和准确性.在对传输截面的计算中,观察到了形状共振,这种共振是由于半束缚态的消失产生的.电导率的计算应用了Chapman-Enskog方法,并与其它理论和实验结果进行了比较.     

Collective Grain Interactions for Constant Ionization Source

The dust screening and dust attraction in plasmas is considered for the constant ionization source. Both limits of linear and nonlinear screening are considered. It is shown that the non‐linear screening changes substantially the collective dust screening and collective dust attraction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of atom-atom collisions on the collisional-radiative ionization and recombination coefficients of hydrogen plasmas

The collisional-radiative recombination and ionization coefficients have been calculated for hydrogen plasmas of low ionization degree. The method consists in solving a coupled system of rate equations which not only accounts for the electronic but also for the atomic collision processes.     

Free Energy and Ionization in Dense Plasmas of the Light Elements

Padé approximations for the free energy of plasmas are given which take into account multiple ionization effects. The free energy landscape over the degrees of ionization is discussed. On the example of helium plasmas the possibility of two minima, i. e. two stable ionization states is shown.