Oblique injection of EC ordinary waves in a Tokamak plasma

Summary A detailed analysis of the propagation and damping of ordinary waves in the electron cyclotron frequency range in a Tokamak-like stratified plasma is given. The waves are supposed to be launched from the low-magnetic-field side of the machine in the meridian plane, with an angle, with respect to the perpendicular at the launching point, to the toroidal magnetic field. In this first part of the paper the emphasis, is on the WKB analysis of the process,i.e. on the study of the local-dispersion relation, first in the cold case and then taking full account of finite-Larmor-radius effects. A thorough study of the intricacies presented by both cold and hot dispersions around the Preinhaelter, and Kopecky critical angle of injection is made. This complicated behaviour has not been analysed in previous works on the subject.

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Riassunto Si presenta un’analisi molto dettagliata della propagazione e dell’assorbimento di onde ordinarie con frequenza vicina alla frequenza ciclotronica degli elettroni in un plasma stratificato che simula la geometria, del Tokamak. Si suppone che l’onda venga lanciata dalla parte esterna della macchina, nel piano meridiano, ma obliquamente rispetto alla normale alle linee di forza del campo toroidale nella posizione di lancio. In questa prima parte del lavoro si pone l’accento sull’analisi locale, di tipo WKB, del fenomeno, vale a dire sulle caratteristiche delle dispersioni e si studia prima di tutto la dispersione fredda e poi quella piú completa basata sull’equazione di Vlasov. Si studia in grande dettaglio il comportamento intricato di entrambe le dispersioni nell’intorno del valore critico di Preinhaelter e Kopecky dell’angolo d’iniezione. Questo andamento complicato della dispersione non era stato studiato nei lavori esistenti sull’argomento.

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Резюме Проводится подробный анализ распространения и затухания обыкновенных волн в области электронной циклотронной частоты в стратифицированной плазме Токамака. Прелполагается, что волны запускаются со стороны слабого магнитного поля машины в меридианной плоскости под углом к перпендикуляру в точке запуска к тороидаляному магнитному полю. В первой части статьи проводится ВКБ анализ процесса,. т.е. исследуется локальное дисперсионное соотношение, сначала в холодном случае, а затем, учитывая эффекты, связанные с конечным ларморовским радиусом. Особое внимание уделяется трудностям, связанным с холодной и горячей дисперсиями вокруг критического угла инжектирования Преннхалтера и Копецкого. Это сложное поведение не было проанализировано в предыдущих работах на эту тему.

     

紧凑型L波段磁绝缘线振荡器的粒子模拟

采取减小阴极杆半径和长度、阴阳极间隙、叶片的长度和厚度及慢波结构周期的办法构造了一种紧凑型磁绝缘线性振荡器（MILO），并用2.5维全电磁PIC方法对这一器件进行了粒子模拟研究。该装置主频为1.9GHz，饱和后平均输出功率达5.4GW，束波转换效率达12％。紧凑型MILO结构能避免电击穿，电子束发射的对称性较易控制。     

Dynamics of plasma channel in a parallel-plate plasma gun

Lumped parameter models for describing dynamics of the plasma channel in a parallel-plate plasma gun are compared with the experimental results obtained from two plasma guns with different rail geometries. Comparison between the experiments and the numerical calculations reveals that the lumped parameter models can be utilized to describe the dynamic motion of the plasma channel quite well. Parametric study shows that minimizing the line inductance and increasing the charging voltage on a capacitor as well as minimizing the gas injection time for reducing the mass of the plasma channel are the key factors to increase the flow velocity of the plasma jet ejected from the plasma gun.     

Experiments on the injection of dust jets into plasma

An experimental technique for studying the injection of dust jets into the plasma of a glow discharge in air is developed. The velocity and flight time of a dust jet are measured under different initial conditions. It is shown that the propagation of dust grains in plasma is accompanied by self-contraction instability along and across the discharge, which leads to dust agglomerization and clusterization.     

双阳极回旋管磁控注入电子枪设计

对真实磁场进行拟合,根据电子光学原理以及绝热压缩理论,运用EGUN软件,设计了工作模式为TE34,19的170 GHz回旋管双阳极磁控注入电子枪。最终得到的电子注速度比约为1.3,速度零散小于3%。分析了调节磁场位置、阴阳极间距、阳极间距等因素对电子注性能的影响。结果表明:电子注的速度比和速度零散对于这些影响因子的变化比较敏感,随着阴阳极间距以及阳极间距的增加,速度比逐渐减小,速度零散先减小后增大。设计的双阳极电子枪已应用于整管实验中。     

Oblique angle deposition of TiO2 thin films prepared by electron-beam evaporation

Optical, structural and photocatalytic properties of TiO₂ thin films obliquely deposited on quartz glass substrate using an electron-beam evaporation method were investigated. The photocatalytic activity of the films was evaluated by photodecomposition of methylene blue. An increase in incident deposition angle increased the porosity and surface roughness of the TiO₂ films. As a result, the photocatalytic activity was enhanced with incident deposition angle up to 60°. However, a further increase in incident deposition angle to 75° reduced the photocatalytic activity due to a lack of the crystalline phase.     

New mode of operating a magnetized coaxial plasma gun for injecting magnetic helicity into a spheromak

By operating a magnetized coaxial plasma gun continuously with just sufficient current to enable plasma ejection, large gun-voltage spikes (approximately 1 kV) are produced, giving the highest sustained voltage approximately 500 V and highest sustained helicity injection rate observed in the Sustained Spheromak Physics Experiment. The spheromak magnetic field increases monotonically with time, exhibiting the lowest fluctuation levels observed during formation of any spheromak (B/B>/=2%). The results suggest an important mechanism for field generation by helicity injection, namely, the merging of helicity-carrying filaments.     

Decay of plasma cluster accelerated by coaxial gun

In this paper the decay of air cluster accelerated into the vacual tube is studied. The time dependence of electron density and electron temperature is introduced and the influence of various recombination processes is discussed. The observed plasma decay shows an exponential law, and is for various gun regimes independent and may be explained by ambipolar diffusion to the tube walls.     

The effect of a non-minimally coupled scalar field upon classical thermodynamics

It is known that a scalar field that is non-minimally coupled to the geometry implies a varying gravitational “constant” G_eff, and hence a violation of the continuity equations, $\text{T}\text{?}{}^{\mathrm{ik}}{}_{\mathrm{;k}}\text{≠ 0}$, where $\text{T}\text{?}{}_{\mathrm{ij}}$ is the uncorrected energy-momentum tensor. This in turn upsets classical thermodynamics. 3he simplest resolution of this difficulty is to multiply all energetic quantities by $\text{G}{}_{\mathrm{<mtext>eff</mtext>}}\text{G}{}_{\mathrm{<mtext>N</mtext>}}$, where G_N is the newtonian gravitational constant. This modified thermodynamics is applied to the scalar-field version of the cosmological model of Zee, for which it is shown to cause restoration of the symmetry above some critical temperature T_c close to the Planck temperature. We also illustrate how the second law of thermodynamics is always obeyed, correcting a recent discussion by Davies.     

Effect of a magnetic field upon the gunn effect in InSb

For times less than 2.5 nsec after the application of an electric field pulse in n-type InSb at 77°K, a sharp drop in the current occurs for electric fields > 600 V/cm. This drop has been previously interpreted as the occurrence of the Gunn effect in InSb due to intervalley transfer. A transverse magnetic field produces an appreciable decrease in the threshold for the instability.     

Some methods of electron-beam entry into a dense gas

A system is considered of pumping a laser with an electron beam that moves relative to the active medium. The problem of planar two-dimensional gas flow through a bounded heat-releasing medium, a problem analogous to that of rectilinear motion of a beam with constant velocity, is solved analytically. It is proposed to admit an electron beam into a dense gas through aerodynamic ports. The effect of perturbations induced by the beam passage on the flow of gas in an aerodynamic port with a rarefaction wave is analyzed.Translated from Trudy Ordena Lenina Fizicheskogo Institute im. P. N. Lebedeva AN SSSR, Vol. 145, pp. 160–171, 1984.     

Interacting electrons in a two-dimensional disordered environment: effect of a zeeman magnetic field

The effect of a Zeeman magnetic field coupled to the spin of the electrons on the conducting properties of the disordered Hubbard model is studied. Using the determinant quantum Monte Carlo method, the temperature- and magnetic-field-dependent conductivity is calculated, as well as the degree of spin polarization. We find that the Zeeman magnetic field suppresses the metallic behavior present for certain values of interaction and disorder strength and is able to induce a metal-insulator transition at a critical field strength. It is argued that the qualitative features of magnetoconductance in this microscopic model containing both repulsive interactions and disorder are in agreement with experimental findings in two-dimensional electron and hole gases in semiconductor structures.     

毫米波回旋速调管磁控注入电子枪模拟计算

介绍了毫米波回旋速调管磁控注入电子枪的结构与特点。电子枪提供的电子束流性能直接影响到回旋速调管的总体参数,为保证整管的效率和输出功率,利用电子枪模拟程序对电子轨迹进行模拟计算,研究了电极形状、磁场分布以及电子轨迹与电子注参量的影响,并为磁控注入电子枪的设计提供了理论依据。     

Performance evaluation of self-breakdown-based single-gap plasma cathode electron gun

This paper presents the experimental studies on self-breakdown-based single-gap plasma cathode electron (PCE) gun (5–20 kV/50–160 A) in argon, gas atmosphere and its performance evaluation based on particle-in-cell (PIC) simulation code ‘OOPIC-Pro’. The PCE-Gun works in conducting phase (low energy, high current) of pseudospark discharge. It produces intense electron beam, which can propagate more than 200 mm in the drift space region without external magnetic field. The profile of this beam in the drift space region at different breakdown conditions (i.e., gas pressures and applied voltages) has been studied and the experimental results are compared with simulated values. It is demonstrated that ～30% beam current is lost during the propagation possibly due to space charge neutralization and collisions with neutral particles and walls.     

A steady-state fluid model of the coaxial plasma gun

The plasma layer in a coaxial plasma gun is considered as a shock front driven by expanding magnetic fields. Analytical steady-state solutions of the fluid equations yield the plasma properties, allowing the scaling of plasma focus devices.