Physical Constants for Microwave Discharge.
Abstract
Physical characteristics of gas breakdown caused by high-powered microwaves were studied experimentally. Since conditions for initiating breakdown have been studied theoretically and experimentally, this study concentrated on characterizing the breakdown plasma. The characteristics measured were plasma size, strength of the pressure wave emanating from the discharge, and the ion current collected on an electrostatic probe inserted in the plasma. From these measurements it was possible to estimate the temperature of the plasma, the efficiency of the plasma as a microwave absorber, and the electron and ion densities in the plasma. The experiments were made at the SRI microwave facility, which uses a 250 kW X-band (9.375 GHz) transmitter for its microwave source. The microwave energy is focused into a vacuum vessel (a bell jar) using a horn feed and a parabolic reflector. In the vacuum vessel a reflecting plate serves both to focus the microwave energy above the plate and as a mount for instrumentation that measures the discharge region. Camera measurements of the discharge showed that the discharge regions formed in the antinodal regions above the reflecting plate and took the shape of small pancakes. The lowermost and largest discharge region was about 2 cm in diameter and 2 mm thick. It floated about 8.7 mm above the reflecting plate, so that its distance from midplasma to reflecting plate was 9.7 mm. This was slightly higher than the 8 mm calculated as the antinodal point of the 9.735 GHz wave. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 16, 1982
- Accession Number
- ADA125055
Entities
People
- G. August
- S. A. Damron
Organizations
- SRI International