Measurements of the Effect of a Thin Plasma Layer on the Near Field of an Aperture Antenna

Abstract

Measurements of the X-band microwave attenuation produced by a high-density air plasma slab coating an aperture antenna were performed. The plasma was produced in a rectangular shock tube using the conical driving technique. Measured shock velocities varied from 2.4 to 5.0 mm/μ sec at initial pressures of 10–50 Torr. Plasma slabs with a thickness of 3.175 and 12.7 mm were utilized in the experiments. Attenuation measurements are in reasonable agreement with impedance sheet theoretical predictions. Additional measurements were made of the effectiveness of sulfur hexafluoride as a plasma alleviant in a high-temperature oxidizing environment. Significant reduction in microwave attenuation was observed for high-temperature air plasmas containing small mole fractions of sulfur hexafluoride.