Low pressure toroidal glow discharge in a radial magnetic field

By measuring the force acting on a flag suspended in a plasma flow the plasma velocity has been estimated. For case when η ? σ B²_r Kracík's theory has been verified experimentally.     

Low pressure toroidal glow discharge in the radial magnetic field

The behaviour of the plasma of a low pressure toroidal glow discharge in a radial magnetic field is studied experimentally. Results concerning the plasma velocity as a function of the magnetic field for different pressures are given.The author wishes to express his thanks to Prof. J. Kracík DrSc for valuable advice and suggestions and Mr. K. Kavalier for his active assistance.     

The influence of a transverse magnetic field on a subnormal glow discharge in air

In subnormal glow discharge under d.c. excitation at different pressure in a varying transverse magnetic field (0 to 30 G) some measurements have been carried out for various initial average tube currents. The voltage across the discharge increases and average tube current and residual current decreases in the magnetic field. With the help of Beckman’s expression [4] for the axial field and the electron density distribution in a transverse magnetic field the observed variation of current and voltage can be satisfactorily explained. The variation of axial electric field with transverse magnetic field can be represented to a fair degree of accuracy by the derived equation. The behaviour of residual current with magnetic field has been observed in these oscillations.     

The experimental investigation of a glow discharge in a toroidal tube

A glow discharge in a toroidal tube with axial discharge current is investigated. The investigation was carried out for a discharge as a whole, not for electrodal zones and the positive column separately. The volt-ampere characteristics for different pressures and Paschen's curves for different gases were measured. The curves obtained are compared with analogous ones for a cylindrical tube. The conditions for the existence of a glow discharge in a toroidal tube and the processes passing there are discussed on the basis of the measured curves. The experiments were carried out in air, helium, argon and neon.     

The effect of a longitudinal magnetic field on the plasma-dust structures in strata in a glow discharge

The plasma-dust structures in strata in a glow discharge exposed to a longitudinal magnetic field are studied in detail. In a weakly ordered structure, the angular velocity has a vertical gradient. A reversal of rotation of the structure in a magnetic field corresponding to the magnetization of electrons is found. With the help of the pair distribution function of particles, changes in the degree of order of the structure in the magnetic field are revealed. These changes correlate with changes in the angular velocity of rotation. To explain this effect, it is assumed that the dust structure is subjected to the action of ions in crossed electric and magnetic fields.     

Dusty plasma in the stratified glow discharge in moderate magnetic field

This article presents the experimental study of dust structures formed in striations of glow discharge in an external magnetic field of up to 10⁴ G, which was created using a cryomagnet. A magnetic field classification based on probe theory is described. In moderate magnetic field, we obtained stable dust structures. The corresponding experimental setup and the experiment itself are described in detail. Special attention was paid to the influence of magnetic field on the change of the diameter and inter‐particle distance of dusty cloud. And, we also determined the dependence of angular velocity of dust rotation on magnetic induction.     

The onset of rotational motion of dusty plasma structures in strata of a glow discharge in a magnetic field

An interpretation is given to the previously observed action of a magnetic field on the state of a dusty plasma structure in strata of a glow discharge. The conditions of previous experiments are analyzed, in which a nonuniform rotation and a change in the degree of order of a dusty plasma structure (the translational order), as well as a correlation between them, were revealed. Based on this analysis and on data in the literature on dusty plasmas in a magnetic field, a hypothesis is made that the reason for the rotation of the structure is the ion drag force. Additional experiments on the observation of the onset of rotational motion of a structure in “weak” and “strong” magnetic fields are conducted. It is shown that rotation reversal (and rearrangement of the order of the structure) is caused by changes in the direction of ionic flows—from internal regions of the structure to its periphery and vice versa—in the weak and strong magnetic fields. The results obtained agree qualitatively with the hypothesis adopted, as well as with the data of the two-dimensional theory of strata.     

Flux flow current-voltage characteristics and their magnetic field dependence in a type II superconductor

Experimental flux flow V-I characteristics are compared with our previous model which assumes flux motion is interrupted by local pinning interactions. Quantitative changes in these characteristics occur at the field at which the peak in the pinning force occurs.     

Roles of electric field on toroidal magnetic confinement

Theoretical research on the influence of electric field on toroidal magnetic confinement is surveyed. The static electric field is first described. A physical picture of the radial electric field generation and its influence on confinement are shown. Neoclassical effects as well as the non-classical processes are discussed. Emphasis is made on the connection with improved confinement. Convective cells with a nonuniform potential on the magnetic surface are also discussed. The roles of the fluctuating electric field are then reviewed. Recent progress in anomalous transport theory is addressed. Through these surveys, the impact of experiments using the heavy ion beam probes on modern plasma physics is illustrated     

Experimental study of the effect of a longitudinal magnetic field on the cathode parts of a glow discharge in helium

The effect of a longitudinal magnetic field on the electrical and optical properties of negative glow and the Faraday dark space of a glow discharge in helium is experimentally studied at a discharge current J_d=11 mA and a pressure of 100–150 Pa in the discharge chamber. An experimental setup is designed and described. A longitudinal electric field is found to be absent in the region of negative glow and the Faraday dark space in both the presence and the absence of the magnetic field. The magnetic field is shown to decrease the voltage of the glow discharge and to increase the total discharge luminosity and the intensities of some spectral lines by a factor of 10–12. The experimental results are explained.     

The effect of the anode dimensions on the characteristics of a hollow-cathode glow discharge

An analysis is made of the effect of the anode dimensions and the gas pressure on the possibility of achieving various conditions of burning of a hollow-cathode glow discharge (with negative or positive anode fall), and also with an anode plasma and an electrostatic double layer. Analytical relations that agree with experimental data are found for the voltage across the cathode sheath and the double layer as a function of the anode area and the pressure. Simple expressions are derived for the critical pressure below which no discharge of a particular kind is possible. Zh. Tekh. Fiz. 67, 43–47 (May 1997)     

Interference patterns in the current-voltage characteristics of superconductor films in longitudinal magnetic field

We present experimental evidence that the induced voltage in the current-induced-transition region in dirty superconductor films in longitudinal magnetic field reveals interference patterns as the applied current is changed.     

Experimental study on influence of cooling on glow discharge parameters

The influence of cooling of the discharge tube walls by the liquid nitrogen on some basic parameters of the neon glow discharge positive column is studied. By probe measurements, the longitudinal electrical fieldE _z, the electron concentrationn _e and the electron temperatureT _e are determined. The equation for determination of the radial profile of the relative electron concentration is derived and, on base of experimentally obtained quantities of the radial potentialV(r), this radial profile is computed.     

The effect of ion emission on the characteristics of a glow discharge with a hollow cathode

The effect of extraction of the ion current on the conditions for sustaining a low-pressure glow discharge with a hollow cathode, which is a topical problem for developing ion sources, is studied. It is shown that there exists a certain optimal level of the ion emission at which the energy efficiency reaches its maximum.     

Experimental evidence of a zonal magnetic field in a toroidal plasma

A zonal magnetic field is found in a toroidal plasma. The magnetic field has a symmetric bandlike structure, which is uniform in the toroidal and poloidal directions and varies radially with a finite wavelength of mesoscale, which is analogous to zonal flows. A time-dependent bicoherence analysis reveals that the magnetic field should be generated by the background plasma turbulence. The discovery is classified as a new kind of phenomenon of structured magnetic field generation, giving insight into phenomena such as dipole field generation in rotational planets.     

The influence of acoustic waves on the positive column of a glow discharge with standing striations

The influence was investigated of low-frequency standing acoustic waves on the positive column of a glow discharge in air and nitrogen in a regime in which spontaneous formation of standing striations readily occurs. Experimental information is presented proving that an acoustic wave of sufficient energy propagating along the discharge axis has a great influence on physical processes creating standing striations in a molecular gas.In conclusion the author would like to thank Prof. J. Kracík for his support and his interest in this work and Mr. P. Slovák for his assistance with the experimental work.