Temperature and density profiles of electrons in a hollow cathode argon-arc discharge

Abstract

Measurements have been performed of radial radiation profiles of argon I and II lines in a hollow cathode, low-pressure, magnetically confined argon-arc discharge with currents of 15–60 A. The working pressure of the discharge was ∼10 -3 mm of Hg and the electron density was ∼10 19 m -3. From the radiation profiles, radial temperature and density profiles of the electrons have been calculated. For the calculations, we made use of Corono equilibrium formulae and we discuss how far these formulae give a good description of the excitation phenomena in the plasma. It appears that, in most cases, the decrease of the electron temperature is about 10 per cent per 10 mm or less and that the width at half-maximum value of the electron-density profile for a confined plasma is about 18 mm for an end-anode configuration situated at 1.2 m from the cathode, and 27 mm for a ringshaped anode situated near the cathode. These widths are roughly independent of the magnetic induction value between 3.75 × 10 -2 and 12.5 × 10 -2 T.