Interpulse plasmas of high power short pulse microwaves

Summary form only given. The properties of a plasma generated between the pulses (interpulse plasma) of high power (60-100 kW), short pulse (0.05-1.0 /spl mu/s) microwaves of 3 GHz are studied in a range of p/spl lambda/=10/sup -1/=10/sup 2/ Torr-cm, where p is the pressure and /spl lambda/ is the wavelength. Argon plasma is produced inside a cylindrical vessel with a characteristic diffusion length /spl sim/3 cm, and confined by a multicusp magnetic field. Interpulse plasmas have demonstrated unique properties/sup 1-3/ as compared to conventionally known afterglows. Some novel features include a delayed plasma build up which prolongs even after the end of the microwave pulse and a high electron temperature which persists even in the power off phase of the discharge. In this report, we present further results with focus on the characteristics of the build up over a wide pressure range. The peak value of the currents and the total optical intensity including their respective build up times show a minimum around 1 Torr. The pulse repetition frequency (10-500 Hz) has a negligible effect on the peak currents, build up time, growth and decay constants. Increase in pulse duration, however, has a finite influence on the discharge; the peak current and growth constant increases and the build up time decreases. The experimental observations are discussed in the light of theoretical considerations.