Verification of Hot Plasma Theory for Microwave Propagation

An analysis is presented of an experimentally detected resonance at the second harmonic of the electron cyclotron frequency. Phase shift and attenuation measurements show reasonable agreement with the predictions of hot plasma theory. In this theory a dispersion relation is derived from a perturbation solution of the linearized collisionless Boltzmann equation with the velocity distribution function of the unperturbed plasma assumed to be Maxwellian. In the experiment 4-mm microwaves were propagated in the extraordinary mode (E ⊥ B0) across a highly ionized essentially uniform plasma of 10-cm diameter confined in a highly homogeneous (0.05%) magnetic field in the Model C Stellarator. Conditions existing for the measurements are: 5≲Te≲25 eV;ωp≲ω/2;10−5≲νcoll/ω<5×10−4;Ω≅ω/2 (Ω is the electron cyclotron frequency). Under these conditions multiple harmonic anomalies as detected by other investigators were not observed.