Plasma Dynamics

The pulsed dc discharge was produced in a 13 mm X 15 mm quartz tube of 75-cm length by passing a current ranging from 10 ma to 1200 ma through the tube for approx-1 imately 500 f.sec at a repetition rate of 200 sec. Helium pressures of 0.03-2.0 mm Hg were used in the experiments. Part of the discharge tube length was contained inside a 1 in. X 2 in. waveguide in such a manner that the tube and waveguide axes were nearly coincident. The discharge tube was mounted on the axis of a solenoid magnet that produced a magnetic field uniform to 1 per cent over the length of the discharge within the waveguide. The microwave radiation detector consisted of a 5500-mec local oscillator, a balanced crystal mixer, and a 30-mec IF amplifier of 10-mc bandwidth. Through control of the IF amplifier with a 1sec gating signal, the time resolution necessary for transient temperature measurements was achieved in the experiment. Making the transient process periodic through repetitive pulsing of the plasma and integrating the measurement over many pulses yielded an instrumental accuracy of approximately ±100 °K over the temperature range 300"-20,000oK. 4 The longitudinal magnetic field that could be applied to the plasma served to minimize the electron particle and energy decay in the afterglow arising from diffusion to