Transport and Turbulence Experiments in Three Regimes of a Magnetized Plasma

Abstract

The occurrence of turbulence and its influence on plasma viscosity have been investigated. A simple model of turbulence has been obtained by the balance of the growth of the combined Rayleigh‐Taylor and Kelvin‐Helmholtz instability with the damping by friction against the neutrals, by kinetic viscosity and by turbulent viscosity itself. In the experiment, a hollow cathode arc, three regimes can be distinguished: a kinetic, a frictional and a turbulent regime. By variations of the discharge parameters around a suitably chosen operating point, transitions between the three regimes are caused. It appears that the longitudinal drift velocity is also influenced by the turbulence. A dispersion relation for the large scale oscillation of the whole arc has been derived and checked experimentally.

Investigation of oscillations and anomalous transport in a hydrogen hollow cathode discharge by a spatially three-dimensional two-fluid model

“…The study of fluctuations and radial transport and their interrelations is an important topic in general plasma physics [1][2][3][4][5][6][7], in the field of low-temperature plasma physics [8][9][10][11][12][13][14][15][16][17][18][19][20] and in the field of nuclear fusion research [21][22][23][24][25][26]. In magnetized plasma experiments it is frequently found [5,27,28] that the radial particle transport largely exceeds the values predicted by classical or neoclassical theories [29][30][31], which describe the contributions to the particle transport induced by collisional processes.…”

“…In this paper we present a summary and overview of the experimental results and the modelling of a magnetized hollow cathode arc discharge burning in hydrogen. The plasma of a similar discharge burning in argon has been investigated previously [10][11][12][32][33][34][35][36][37][38]. In these papers it was found, that the hollow cathode may be nearly described as a point source for the plasma, where the charge carriers are produced mainly in the cathode fall and then stream with high axial drift velocities along the magnetic field axis towards the anode.…”

“…With increasing distance from the cathode axis the radial distributions of electron density and temperature broaden, while the maximum values decrease. Furthermore, low-frequency instabilities with small relative amplitudes have been found experimentally in this type of discharges [10][11][12]16] and a theoretical description of these instabilities was developed in terms of a linearized drift wave model [16,28].…”