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.     

Optogalvanic Properties of the Ion Guide Source in the Recoil Nucleus Selective Photoionization

This consideration is a conjunction of two processes: generation of recoil products and selective detection. A new type of plasma is carried out. The electron energy function distribution of the ion-guide source plasma is calculated and discussed. The properties of a laser ionization scheme detecting recoil atoms are analyzed using an optogalvanic approach.

The Resonant Laser Ionization (RLI) in low temperature currentless plasma, formed by accelerated particle beam propagating through gas, will be used for the above mentioned separation. A tuned dye laser excites the studied atoms and the fast electrons ionize them. This process exceeds in cross-section the ionization from ground state which provides selectivity of IGS. The latter produces ions of almost all chemical elements. It can be used for investigating processes flowing in low temperature currentless plasma which presents a specific interest. These functions impart to the IGS the role of an Optogalvanic (OG) element, to be precise, of hollow cathode discharge used as an OG detector [1].

In this paper the IGS is analyzed as an OG detector in a quasi OG scheme. The investigation is a step simulating the IGS properties. The Electron Energy Distribution Function (EEDF) and the most important processes are analyzed and discussed as a first step in this field. The results obtained contribute to the efficiency of the RLI method.     

The Development and Application of Low Temperature Plasma Technology

The development and applications of low temperature plasma technology used in surface modification of materials are presented in this paper. Based on plasma sources and ion sources technology, multi-functions ion implantation and deposition technologies were developed and the related processes are also used to treat different products. The related technologies were translated into industrial productions supported by national research projects. Following the last development of international plasma researches, the standardization and internationalization processes of plasma technologies are executed in our center.     

甚高频激发容性耦合氩等离子体的电子能量分布函数的演变

甚高频激发的容性耦合等离子体由于离子通量和能量的相对独立可控而受到人们的关注. 本文采用朗缪尔探针诊断技术测量了40.68 MHz激发的容性耦合Ar等离子体的特性(如电子能量概率分布、电子温度和密度等)随宏观参量的演变情况. 实验结果表明, 电子能量概率分布随着气压的增加从双麦克斯韦分布逐步转变为单麦克斯韦分布并最终演变为Druyvesteyn分布, 而射频激发功率的增加促进了低能电子布居数的增强; 在从等离子体放电中心移向边界的过程中, 低能电子的布居数显著下降, 而高能电子的布居则有所上升; 放电极板间距的变化直接导致了等离子体中电子加热模式的转变. 另外, 我们也对等离子体中的高低能电子密度和温度的分配情况进行了讨论.     

High- and low-confinement modes in simple magnetized toroidal plasmas

Three-field simulations of interchange turbulence are presented for a simple magnetized toroidal plasma with a vertical magnetic field. The simulations show the presence of two turbulent regimes characterized by low (L) and high (H) confinement properties. We evaluate analytically the properties of the L regime, obtaining expressions for the plasma gradients and for the density and heat fluxes that agree well with the simulations. By increasing the plasma source strength or reducing the vertical magnetic field, a transition to a H regime occurs, in which a strong velocity shear limits the perpendicular transport with respect to the L scaling and the plasma profiles steepen. The analytic estimate of the transition condition is in accord with the simulations.     

Co x Ag1−x core–shell nanoparticles: magnetic and magneto-optical studies

The magneto-optical properties of 14-nm Co _x Ag_1?x core–shell nanoparticles (x=0.7, 0.8, and 0.35) deposited on different substrates are investigated at room temperature in the photon-energy range from 0.8 to 4.8 eV. Particles with low Ag content show spectra very similar to pure Co nanoparticles while particles with high Ag content have totally different features, where the Ag plasma edge dominates the spectra. The spectral features of the polar Kerr rotation depend on particle composition. The ageing process and development of an oxide layer influence the particles’ core–shell structures and magnetization curves. Co-rich particles exhibit lower resistance to the oxidation process as compared to Ag-rich ones. The quality of the nanoparticles was checked by transmission electron microscopy in respect of time scale.     

Thermodynamic characteristics of a metastable plasma

The equation of state is obtained for an ion-ion plasma which is stable with respect to recombination processes. The regions of thermodynamic stability of a nonideal plasma and of mixtures of such a plasma with an ideal plasma are determined by considering isotherms. It is shown that such a plasma-gas mixture possesses elastic properties.General Physics Institute, Russian Academy of Sciences, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 8–14, January, 1993.     

Atomic collision processes relevant for heavy ion beam probes

Atomic collision processes of fast Tl and Cs ions with particles in a high temperature fusion plasma are investigated. At low beam energies (<5 MeV), ion impact collisions and charge exchange processes can be neglected compared to electron ionization processes. At beam energies above 5 MeV and high plasma ion temperatures, collisions with ions start to contribute significantly to signal generation and attenuation. Also, collisions with the neutral background gas in the beamlines can attenuate the ion beam significantly and lower the signal level, if the vacuum pressure is above 10^-4 Torr. For the heavy ion beam probes operating today, only electron impact ionization processes are important and accurate predictions of the secondary signal level and electron density profile measurements are possible because of the good knowledge of electron impact ionization cross sections for Cs ⁺ and Tl⁺ ions     

Plasma oscillations in two-dimensional electron systems with a superstructure under Stark quantization conditions

The effect of quantizing electric field on plasma oscillations of two-dimensional electron gas in a system with a periodic potential has been theoretically investigated. The coupled-plasmon spectrum ω(q) is calculated for high temperatures (Δ ? T, where Δ is the conduction miniband width and T is temperature in energy units). The calculations are based on the quantum theory of plasma oscillations in the random-phase approximation, with allowance for the umklapp processes.     

Condensation effects of excitons

The theory of the electronic excitations in a highly excited semiconductor is presented. The relaxation processes, the formation of excitons and excitonic molecules, the interaction among the various forms of electronic excitations, as well as their optical and thermodynamical properties are analyzed. At low temperatures one expects condensations into the quantum statistically degenerate phases of the excitonic molecules and of the electron-hole plasma. The physical properties of these low temperature phases are investigated. Possibilities and previous attempts to observe the Bose-Einstein condensation in excitonic systems are discussed critically. The experimental observations of the electron-hole liquid phase transition are reviewed.     

Equilibrium properties of two-component classical plasmas

Two-component overall neutral classical Coulomb Gas is considered in the canonical ensemble for any value of the space dimensionality ν. The equilibrium properties, i.e. pair correlations and thermodynamic functions are investigated in two complementary ways. The first one is adequate in considering the low temperature range and uses the “molecular” interaction within a pair of unlike charges as a zero order starting point. On the other hand, the high-temperature fully ionized and translation-invariant plasma is considered within the nodal expression with respect to the classical plasma parameter. These two ways are possible through the use of effective temperature-dependent classical interaction for ν > 2. As a by-product, we obtain a unified treatment of the Coulomb Gas thermal properties with respect to dimensionality (integer or real). We also obtain a contrasting comparison with corresponding properties of the one component plasma model which are already known. In this analysis the ν = 2 two-component Coulomb Gas seems to be a landmark for the other TCP'₈. I do not consider degeneracy effects. I consider diffraction corrections in a first order expansion with respect to the Coulomb interaction, in the high-temperature range. The “Hydrogen atom” spectrum is explained for all ν. The long-range hypernetted chain resummation of the pair correlation functions asymptotic behavior does not hold for symmetrical (Z₁ = ?Z₂) plasmas; the corresponding onset of short-range order disappears when the plasma parameter increases. The modified long- and short-range behaviors of the pair correlation functions are then displayed with the canonical thermodynamics.     

Modulation instability of lower hybrid waves leading to cusp solitons in electron–positron(hole)–ion Thomas Fermi plasma

Following the idea of three‐wave resonant interactions of lower hybrid waves, it is shown that quantum‐modified lower hybrid (QLH) wave in electron–positron–ion plasma with spatial dispersion can decay into another QLH wave (where electron and positrons are activated, whereas ions remain in the background) and another ultra‐low frequency quantum‐modified ultra‐low frequency Lower Hybrid (QULH) (where ions are mobile). Quantum effects like Bohm potential and Fermi pressure on the lower hybrid wave significantly reshaped the dispersion properties of these waves. Later, a set of non‐linear Zakharov equations were derived to consider the formation of QLH wave solitons, with the non‐linear contribution from the QLH waves. Furthermore, modulational instability of the lower hybrid wave solitons is investigated, and consequently, its growth rates are examined for different limiting cases. As the growth rate associated with the three‐wave resonant interaction is generally smaller than the growth associated with the modulational instability, only the latter have been investigated. Soliton solutions from the set of coupled Zakharov and NLS equations in the quasi‐stationary regime have been studied. Ordinary solitons are an attribute of non‐linearity, whereas a cusp soliton solution featured by nonlocal nonlinearity has also been studied. Such an approach to lower hybrid waves and cusp solitons study in Fermi gas comprising electron positron and ions is new and important. The general results obtained in this quantum plasma theory will have widespread applicability, particularly for processes in high‐energy plasma–laser interactions set for laboratory astrophysics and solid‐state plasmas.     

Mass-spectroscopic study of the influence of nozzle material on high-pressure SF6 arcs

The interrupting capability of a gas-blast high-voltage circuit breaker (CB) is mainly determined by the self-induced pressure rise caused by the thermal arc energy, the composition of the arc plasma and the chemical reactions occuring during and after current interruption. We have studied the nozzle materials boron nitride (BN), quartz (SiO₂), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene (ETFE), polyethylene (PE) and epoxy resin (ER) with respect to their influence on these processes with the aid of a model circuit breaker (MCB). Direct measurements of the arc-induced pressure rise reveal that the portion of the arc energy available for the pressure rise varies greatly (20%–65%) with the properties of the nozzle material. Nozzle erosion is significantly higher for materials with high values (e.g. polymers). Therefore, the lifetime of polymer nozzles is considerably shorter than that of ceramic nozzles. We have investigated the influence of the nozzle material on the decomposition products formed in the arc discharge of our MCB by studying the composition and time dependence of these products. The MCB was directly attached to the time-of-flight mass spectrometer (TOFMS) with the aid of a molecular-beam sampling system, which allowed real-time measurements of the arced gas during and after current interruption, thus providing information on the ablation mechanism and on the reaction kinetics of vaporised nozzle material with dissociated SF₆. The most abundant long-lived reaction products are SF₄, SOF₂, C₂H₂, CO, and CS₂. Their formation rates have been determined as functions of the nozzle material. With respect to quantities and properties of decomposition products, ceramics are superior to polymers since they form only small concentrations of corrosive and toxic products.     

The motion of light interstitials in metals: Recent experiments

Recent theoretical considerations suggest, that at low temperatures the transport properties of light interstitials in metals are dominated by the interaction with the conduction electrons. After briefly surveying the state of the theory, experimental examples for the low and high temperature cases are presented. We begin with the low T regime and display first neutron scattering experiments on H trapped at O-impurities in Nb where a coherent tunneling state is observed. Its dependence on temperature and its properties in normal and superconducting Nb are discussed. Thereafter muon diffusion results in Al are examined. In Al, muon diffusion is observed via diffusion limited trapping and local properties of the impurity as well as long range diffusion are playing a role. Using a large variety of impurities it was possible to evaluate the diffusion coefficient over a large T-range. Muon motion in Al at accessible temperatures falls entirely in the hopping regime and constitutes an example for the high T regime of the theory.     

Phase Transition in a Vlasov-Boltzmann Binary Mixture

There are not many kinetic models where it is possible to prove bifurcation phenomena for any value of the Knudsen number. Here we consider a binary mixture over a line with collisions and long range repulsive interaction between different species. It undergoes a segregation phase transition at sufficiently low temperature. The spatially homogeneous Maxwellian equilibrium corresponding to the mixed phase, minimizing the free energy at high temperature, changes into a maximizer when the temperature goes below a critical value, while non homogeneous minimizers, corresponding to coexisting segregated phases, arise. We prove that they are dynamically stable with respect to the Vlasov-Boltzmann evolution, while the homogeneous equilibrium becomes dynamically unstable.     

Probing the microstructural evolution of polyviologen-silica hybrid nanopowders during intermediate processing using X-ray microtomography

Polyviologen polymers are potential template agents for hydrolytic sol–gel processing of silica particles. The resultant polyviologen-silica hybrid nanopowders are amorphous aggregates of roughly spherical shape, which can be harvested from the sol–gel solution and processed to green body products under different environmental conditions. A bench-top X-ray microtomography system, with a spatial resolution of 5 μm is used to produce three-dimensional images of the dynamic processing of the nanopowders. Various processing routes are imaged using a custom built environmental chamber where the temperature, atmospheric pressure, and compaction force can be controlled. This allows processes such as vacuum sintering and microwave sintering to be studied. The three-dimensional images reveal the axial and radial distributions of the molten polyviologen polymer within a matrix of agglomerates of the silica nanoparticles. Such observations are crucial to the optimisation of the processes that are used to produce the green body products so as to preserve desirable nano-intensive properties. PACS 82.35.Np; 87.59.-e; 81.07.Pr; 87.59.Bh     

Effect of humidity and holding temperature (in the range from −13 to +60°C) on the recrystallization and aging of strontium-doped KCl crystals after plastic deformation

The effect of humidity and temperature in the range from ?13 to +60°C on the processes of recrystallization and aging is studied upon holding of KCl crystals doped with 0.06 wt % Sr after plastic deformation. The crystals initially consist of a supersaturated solid solution. The presence of water is found to increase the rates of nucleation and growth of grains with twinned orientations with respect to the initial single crystal. Upon aging of these crystals in the presence of water vapor, strontium chloride crystalline-hydrate SrCl₂ 6H₂O forms along the boundaries of recrystallized grains and crack edges. This results not only in a decreased plastic deformation-induced increment in the hardness but also in decomposition of the crystals. It is found that varying the temperature in the range from ?13 to +25°C affects the recrystallization rate and aging processes much more weakly than does the presence of excess moisture. The most stable structure and properties are observed in the case where deformed crystals that are held at temperatures from ?13 to +25°C remain in a solid-solution state. The possible long-term conservation of the high hardness of deformed crystals owing to an additional postdeformation treatment is discussed.     

Study of the terahertz wave propagate in high temperature plasma band gap

In this paper, the phenomenon of band gap transmission in high temperature plasma is studied. Cold plasma has high pass property, so the low-frequency electromagnetic wave cannot penetrate plasma and propagate in it. Simulation results show that in high temperature plasma, a transmission peak will be produced in the low frequency band where the band gap is supposed to occur due to the influence of the external magnetic field and the electron temperature. Through the study of the frequency and the amplitude of the transmission peak, it is found that the frequency of the peak is related to the collision frequency and the magnetic field, and the amplitude of the peak is related to the electron temperature and the thickness of the plasma slab. The calculation formula of peak frequency is obtained by fitting the obtained data. The fitting formula is validated by the analytic solution, and the results show that the two methods are in good agreement.     

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利用EAST装置单道远红外HCN激光干涉仪测量了等离子体中心道(R=1.82m)线平均电子密度。通过充气加料连续提升主等离子体密度,首次在EAST装置上观察到偏滤器等离子体的三种不同状态：低再循环(偏滤器靶板处等离子体温度较高,密度较低),高再循环(偏滤器靶板处等离子体温度较低,密度较高)和脱靶(偏滤器靶板处等离子体温度和密度都很低)等离子体状态。分析了EAST偏滤器在这三种不同状态下的物理现象。     

EAST远红外激光干涉仪与密度爬升实验研究

利用EAST装置单道远红外HCN激光干涉仪测量了等离子体中心道(R=1.82m)线平均电子密度。通过充气加料连续提升主等离子体密度,首次在EAST装置上观察到偏滤器等离子体的三种不同状态：低再循环(偏滤器靶板处等离子体温度较高,密度较低),高再循环(偏滤器靶板处等离子体温度较低,密度较高)和脱靶(偏滤器靶板处等离子体温度和密度都很低)等离子体状态。分析了EAST偏滤器在这三种不同状态下的物理现象。