Electron-Beam Generated Air Plasma Measurements: Effect of Reduced Electric Field*

Measurements of electron density and momentum-transfer collision rate are discussed for plasma generated by an electron beam in air from 1 mT to 636 T as a function of the reduced electric field. A 100 keV electron source operating at a few mA is used to ionize air. A 10 GHz in-phase and quadrature microwave detector measures the electron number density and momentum-transfer collision rate. Optical emissions at 391.4 nm from N$_{2}^{+}$ provide an estimate of volumetric ionization profile along the microwave propagation path. Grids in the air-plasma test cell provide a means of imposing a reduced electric field, while the electron beam ionizes air. Results are discussed in the context of electron density as a function of reduced electric field and pressure.