Electron-Beam Generated Air Plasma Measurement Details: I/Q Detector and Effect of Reduced Electric Field*

An in-phase (I) and quadrature (Q) microwave detector operating at 10 GHz is used to measure the electron number density and momentum-transfer collision rate of air plasma as a function of pressure from 1 mT to 636 T and reduced electric field. Raw measurements from the I/Q detector and the method to convert such measurement into electron number density and momentum transfer collision rate are discussed. Optical emissions at 391.4 nm from N$_{2}^{+}$ are used to quantify the volumetric ionization profile along the microwave propagation path. At low pressure a MAGIC code calculation provides the relative ionization profile. Results of electron number density and momentum-transfer collision rate are shown as a function of reduced electric field and pressure.