Density Distribution and Particle Diffusion in an Energetic Arc in a Magnetic Field

Abstract

The effects of magnetic field and pressure on the radial distribution of plasma density are investigated experimentally for an energetic arc of 10¹⁴ cm⁻³ density and 2×10⁵°K temperature in relation to the diffusion phenomena of plasma. Experiments are made in argon at pressures ranging from 3×10⁻² to 3×10⁻⁵ torr and 1000∼4000 gauss of the magnetic field strength. Classical and Bohm type’s diffusion coefficients were examined for two different states of plasma: One is with low ionization degree (<35%) and the other nearly fully ionized (>98%). The experimental results show that the e-folding length of the exponentially varying density-profile is inversely proportional to the magnetic field strength at 3×10⁻³ torr pressure, whereas to the square root of the strength at 3×10⁻⁵ torr pressure. This suggests that some types of turbulence would be produced in the fully ionized plasma of energetic arc.