Loss of plasma scaling with magnetic field, pressure and discharge current in a CUSP confined plasma

Department of Physics, Bharathiar University, Coimbatore, 641046, India

Corresponding author: physics@as250.bharathi.ernet.in

Received: 8 April 1999
Revised: 22 January 2001
Accepted: 12 March 2001
Published online: 15 September 2001

Abstract

The confinement properties of a low beta argon discharge plasma in a spindle cusp magnetic field was investigated. Plasma was produced by ionisation collisions by the electrons which were produced by thermionic emission of electrons. The central problem involved with plasma confinement by a cusped magnetic field is the loss of particles along the flux lines. Electron and ion leak widths were studied in the ring and point cusps and measured over a range of magnetic field strengths (B), neutral pressures (P) and discharge currents (I_d). It was found that the leak width was reduced with increase in I_d and B. The ion leak widths were found to be larger than the electron leak widths. The normalised effect of magnetic field and pressure on ion and electron leak widths in cusps are reported, compared and discussed. The dependence of electron and ion leak widths on plasma densities were also studied. At very low pressures, high plasma densities and high magnetic field strengths, a quasineutrality condition was attained.