Experiments and analysis of backscatter for microwave propagation in a plasma

Summary form only given. Measurements and analysis of the absorption, reflection, and scattering of electromagnetic waves due to electron cyclotron absorption zones and the presence of modulated scatterers in a plasma are presented. Measurements using a modulated homodyne detection system have been made that are sensitive to the backscatter from a movable probe in the plasma. The phase sensitive system is used to measure the local k-spectrum in the inhomogeneous plasma and is compared with WKB (Wentzel-Kramers-Brillouin) theory. A 12-cm-diameter by 2-m laboratory plasma is produced by a 2.45-GHz microwave source. Wideband wave absorption of 30-50 dB due to the electron cyclotron resonance zone in the 1.5-3.0 GHz range is measured. Experiments examining the microwave scattering frequency sensitivity of modulation-launched magnetoacoustic modes from a ceramic encapsulated PIN diode and from a disc Langmuir probe scatterer have also been performed.