Interaction of Intense rf Fields with Heated Air

Abstract

A model is formulated which predicts the characteristics of a short duration, intense microwave pulse propagating in initially heated, high-temperature air. The temporal and spatial evolution of the electron temperature and density throughout the plasma are specified upon incorporating certain kinetic processes involving N2, NO, and O for 4000°–5000°K air. In conjunction with measurements, field-induced ionization rates of initially heated 4500°K air are presented and found to be substantially greater than room temperature-to-4000°K ionization rates. The post breakdown recombination rate has also been found. The usual constant collision frequency assumption used in predicting rf breakdown levels is shown to be a good approximation.

On the microwave breakdown stability of a spherical hot spot in air

“…which is a reasonable approximation for temperatures less than 2000 K. When the temperature increases beyond 2000 K, substantial production of NO molecules occurs. These molecules have a lower threshold for ionization than O 2 and will eventually dominate the ionization process [10]. Thus, T = 2000 K is the upper limit for allowable temperatures in order for the model to be applicable in air.…”

“…These molecules have a lower threshold for ionization than O 2 and will eventually dominate the ionization process 10 . Thus, T = 2000 K is the upper limit for allowable temperatures in order for the model to be applicable in Air.…”