CH薄膜非平衡辐射烧蚀的特性

用一维多群辐射输运流体力学RDMG程序数值模拟研究了在神光-II黑腔辐射源条件下,非平衡辐射烧蚀CH薄膜的过程,给出了与平衡辐射烧蚀不同的烧蚀图像,得到了非平衡辐射烧蚀相关的数值定律。     

CH薄膜非平衡辐射烧蚀的特性

 用一维多群辐射输运流体力学RDMG程序数值模拟研究了在神光-II黑腔辐射源条件下，非平衡辐射烧蚀CH薄膜的过程，给出了与平衡辐射烧蚀不同的烧蚀图像，得到了非平衡辐射烧蚀相关的数值定律。     

Recombination properties of Rydberg nonequilibrium plasma created by dye laser

Ultracold Rydberg plasma formed by a dye laser has been studied theoretically. Recombination properties in the presence of three-body collisions in hydrogen-like plasma have been investigated. We have shown that the existing calculation models for three-body recombination (Thomson model, diffusion approximation, and modified diffusion approximation) work only in the high-electron-temperature region—more than or equal to 1 eV. When the electron temperature is substantially less 1 eV, we have found the strong dependence of process probability on the energy of free particle. As a result, there is a drastic slowdown recombination in the region, where the three-body recombination dominates. Another reason for this slowdown of the recombination deals with the increment nonideality parameter. Effect of slowdown of recombination with free-body collisions can be reduced to the situation when the thermal equilibrium is set earlier than the ionization equilibrium, and, hence, the formation of metastable structure is possible in the plasma. Also this effect can cause the inverse population on Rydberg levels.     

Effect of a magnetic field on the radiation emitted by a nonequilibrium hydrogen and deuterium plasma

Radiative transfer in a nonequilibrium plasma in an external electric field is considered. The system of kinetic equations determining the populations of atomic levels is written taking into account the combination of collision and radiative processes and is solved together with the kinetic equation for photon of various frequencies, which are emitted and absorbed in the radiative transitions from the states of the continuous and discrete spectra. The shape of spectral lines is determined from the solution of the quantum-mechanical problem on the emission of an atom in the electric field of the plasma and an external magnetic field, taking the Doppler effect into consideration. The developed approach is used in the model calculation of radiative transfer under the conditions corresponding to the edge plasma in a tokamak, which is simulated by a homogeneous plane layer of a deuterium plasma. It is shown that the joint action of the external magnetic field and the electric plasma fields considerably affects the spectral and integrated characteristics of the radiation.     

Spontaneous radiative dissociation in molecular hydrogen

The spontaneous radiative dissociations of the discrete vibrational levels of the B¹Σ⁺_u electronic states of H₂, HD and D₂ of the C¹Π_u electronic state of H₂ into the vibrational continuum of the ground X¹Σ⁺_g state are calculated as a function of the emission wavelength. The fluorescent spectra of HD in the Lyman system and of H₂ in the Werner system resulting from an excitation source uniform in wavelength are predicted. The vibrational radiative lifetimes are tabulated as are the fractions of radiative decays that lead to dissociation. The effects of centrifugal distortion are discussed briefly. An appendix describes a sum rule used to check the numerical accuracy of the calculations.     

Effect of convection and heat conduction on the laser gain in a nonequilibrium recombinational hydrogen wall plasma

The effect of a conducting body with a large heat capacity on the thermal state of a hydrogen plasma in the boundary surface layer is analyzed. It is shown that, under certain conditions, the energy accumulated in the plasma within the boundary layer can be efficiently transferred to the conducting body; this leads to plasma overcooling. The mathematical model of plasma incorporates mechanisms for convective heat exchange and heat conduction. The possibility is analyzed of the existence of nonequilibrium recombination states with inverse population in the overcooled wall plasma. It is shown that the maximum gain (a few tenths of cm^?1) on hydrogen nuclei is achieved at the 3-2 transition for the following initial parameters: the plasma pressure is 1–3 atm, the plasma temperature is 0.5 eV, the tungsten surface temperature is 300 K, and the body radius is 0.5–1.0 m.     

Tailoring silicon radiative properties

We study several schemes to enhance the emission of radiation of silicon surfaces in the infrared. First, we investigate the emission pattern of microscale lamellar gratings ruled on doped silicon which is substantially modified due to the excitation of surface plasmons. In addition to their remarkable spectral selectivity, those sources emit 50% more than a plane interface of bulk doped silicon. An interferential antireflection system similar to a Salisbury screen is also considered. This broadband emitter allows a significant enhancement of the total emitted power compared to the plane interface. These results may have broad applications in sensing and radiative cooling.     

Nonergodicity and nonequilibrium properties of asperomagnets

The nonequilibrium properties of asperomagnetic systems are studied for the example of the alloy Ni-23 at.% Mn. It is shown that the appearance of a de Almeida-Thouless phase, characterized by astronomic equilibration times t _max≫10¹⁵ s, is preceded by the formation of a Gabay-Toulouse phase, for which t _max is comparable to experimental times. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 149–153 (10 August 1997)     

Monochromatic and mean radiative properties of astrophysical plasma mixtures in nonlocal thermodynamic equilibrium regime

Radiative-hydrodynamics and radiative transfer simulations of astrophysical plasmas require the determination of radiative properties. However, most of the plasma radiative properties are calculated assuming the plasma in coronal equilibrium or local thermodynamic equilibrium regimes that is often not the case for many scenarios. In this work, we present nonlocal thermodynamic equilibrium calculations of radiative opacities of Fe and S and of an astrophysical plasma mixture for temperatures larger than 100 eV. We also analyze the departure from local thermodynamic equilibrium simulations.     

Observation of double radiative capture on pionic hydrogen

We report the first observation of double radiative capture on pionic hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC spectrometer and detected gamma-ray coincidences following pi(-) stops in liquid hydrogen. We found the branching ratio for double radiative capture to be [3.05+/-0.27(stat)+/-0.31(syst)]x10(-5). The measured branching ratio and angle-energy distributions support the theoretical prediction of a dominant contribution from the pipi-->gammagamma annihilation mechanism.     

Optical properties of nonequilibrium low-dimensional systems

The optical properties of low-dimensional carrier systems ("quantum wire" type) driven away from equilibrium are studied. The frequency and wave-vector-dependent dielectric function of a quasi-one-dimensional electron system under the action of an exciting external pumping source is derived. The optical responses of the system are obtained in terms of its nonequilibrium thermodynamic state, the latter characterized resorting to a nonequilibrium statistical ensemble formalism.     

Nonclassical transport in a nonequilibrium laser plasma

The onset of a nonequilibrium distribution function in a plasma produced by laser radiation at fluxes I - 10¹⁴ W/cm² is considered. The model employed takes consistent account of the nonlocality of the electron distribution at large density and temperature gradients, the demaxwellizing effect of the external hf field of the laser, and the nondiffusion of the transport in the high-energy part of the electron-distribution spectrum. Numerical solution of the corresponding kinetic equations shows that establishment of a nonequilibrium electron distribution in the corona suppresses the heat transport substantially. Good agreement is obtained between the kinetic value of the heat flux and the phenomenological value needed to reconcile the hydrodynamicsimulation results with the experimental data.Quantum Radiophysics Division, Lebedev Physics Institute. Translated from Preprint No. 179 of the Ledebev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.     

双温度氩-氮等离子体热力学和输运性质计算

获得覆盖较宽温度和压力范围内的等离子体热力学和输运性质是开展等离子体传热和流动过程数值模拟的必要条件.本文通过联立Saha方程、道尔顿分压定律以及电荷准中性条件求解等离子体组分;采用理想气体动力学理论计算等离子体热力学性质;基于Chapman-Enskog方法求解等离子体输运性质.利用上述方法计算了压力为0.1, 1.0和10.0 atm (1 atm=101325 Pa),电子温度在300—30000 K范围内,非局域热力学平衡(电子温度不等于重粒子温度)条件下氩-氮等离子体的热力学和输运性质.结果表明压力和非平衡度会影响等离子体中各化学反应过程,从而对氩-氮等离子体的热力学及输运性质有较大的影响.在局域热力学平衡条件下,计算获得的氩-氮等离子体输运性质和文献报道的数据符合良好.     

Oscillation interaction in a nonequilibrium magnetoactive plasma

Kharkov State University: Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 31, No. 6, pp. 675–679, June, 1988.     

Optical properties in nonequilibrium phase transitions

An open question about the dynamical behavior of materials is how phase transition occurs in highly nonequilibrium systems. One important class of study is the excitation of a solid by an ultrafast, intense laser. The preferential heating of electrons by the laser field gives rise to initial states dominated by hot electrons in a cold lattice. Using a femtosecond laser pump-probe approach, we have followed the temporal evolution of the optical properties of such a system. The results show interesting correlation to nonthermal melting and lattice disordering processes. They also reveal a liquid-plasma transition when the lattice energy density reaches a critical value.     

Small radiative Z-pinch with low-Z plasma

Gas-puff Z-pinch research at the IPP Prague is briefly reviewed. The XUV and soft x-ray measurements performed with several elements from carbon to argon are summarized and scaled with atomic numbers. A coupling of driver and load parameters for optimum generation of K-shell radiation of the mentioned elements is discussed using simple considerations.     

Calculation of the Lyman-α asymmetry in a dense,partially-ionized hydrogen plasma

The asymmetry of the hydrogen resonance line Lyman-α is calculated. The electron perturbers are treated by the impact approximation and the ion perturbers by the quasistatic approximation. Contributions to the quasi-static ion broadening from first- and second-order asymmetry terms are included in the calculations, i.e. contributions from the quadrupolar ion-atom interaction and the quadratic Stark effect.The asymmetry at small separations from the line centre is unaffected by the inclusion of the second-order correction and remains slightly larger than the experimentally determined asymmetry. At larger separations from the line centre, the inclusion of the second-order correction causes a decrease in asymmetry due primarily to the quadratic Stark effect. For these larger separations from the line centre, rather poor agreement is obtained between theory and the experimental results of Boldt and Cooper.     

Narrow-band model for nonequilibrium air plasma radiation

A band model is developed for the prediction of radiative transfer in air plasma applications under equilibrium and non-equilibrium conditions. For non-equilibrium applications, the medium is described by rotational–translational and vibrational temperatures but the populations of electronic states can be arbitrary. A specific formulation of the statistical narrow-band (SNB) model is developed for optically thick electronic systems of diatomic molecules when their populations are described by an electronic temperature. Model parameters, deduced from line by line calculations in the Voigt regime, are shown to be also convenient for arbitrary distribution of molecular electronic populations. This model is then complemented to include optically thin electronic systems and the continuum radiation through the simple box model, and line by line calculations for atomic lines. Several tests including equilibrium, non-equilibrium, uniform, and non-uniform conditions show the ability of this hybrid model to provide accurate and efficient solutions for radiative transfer problems in air plasmas.