High-current, large volume glow plasma production using pulse modulator

Abstract

Glow discharge plasma was produced with large current up to 150 A using a pulse modulator or a capacitor discharge in dry air (N/sub 2/:O/sub 2/=8:2) or pure nitrogen gas. Rogowski profile electrodes having 107 mm diameter were set in the discharge chamber. The gap length of the electrodes was changed from 1 mm to 20 mm in various gas pressures 1-20 torr. The voltage-current characteristics of the glow in dry air at pressure of 10 torr was successfully obtained in wide current range from 20 mA to 150 A. The glow voltage was almost constant until the whole surface of the cathode was covered with glow, i.e., until the discharge current became 3.7 A under our experimental condition. The voltage increased with increasing current from 3.7 A. The electron density in positive column of the high-current glow discharge were obtained to be 4.9/spl times/10/sup 11/ cm/sup -3/ from calculation based on swarm data. This value is close to the electron density 3/spl times/10/sup 11/ cm/sup -3/ measured with Langmuir probe. The high-current glow discharge plasma was successfully produced with 35 /spl mu/s duration at 1 kHz repetition rate using a pulse modulator. Temperature rise during 10 /spl mu/s pulse glow discharge was obtained to almost 250 K by spectroscopic measurements.