Resonance cones in non-Maxwellian plasmas

Abstract

Resonance cones are studied experimentally in hot drifting plasmas and in various beam–plasma situations. In a drifting plasma the upstream–downstream asymmetry of the main cone is suitable for diagnostics of plasma drifts. The evaluation of electron temperature from the interference pattern is discussed in terms of the low-temperature–low-drift approximation (LTLDA) and by comparing with numerical kinetic theory calculations. In this way the range of applicability of this method is extended above the LTLDA. In a beam–plasma situation, the downstream resonance cone exhibits a new interference pattern, which can be attributed to resonant particle effects. The upstream resonance cone is only slightly affected and is found still applicable for Te and ne diagnostics. As a result of comparison with numerical calculations, in which the actual distribution function is used, the downstream interference pattern is proposed to be useful as a diagnostic method for obtaining the mean beam energy. The waves generated by the beam–plasma interaction are analyzed by digital cross-correlation techniques, and found to propagate obliquely to the magnetic field direction at the resonance cone angle.