Helical Configuration Produced in Gaseous Magnetoplasmas by the Gyro-Resonance Absorption of Microwaves

The nonuniform absorption of gyro-resonant microwave energy by an electron gas is used to produce the helical configuration in gaseous magnetoplasmas. This configuration is examined both theoretically and experimentally. Stability criteria for the existence of the helix and the dependence of the properties of the helix on the plasma parameters are derived from the two-fluid mangetohydrodynamic equations for electrons and ions. The experimental examination of the instability is accomplished by the use of a suitable diagnostic procedure using low power (≈ 50 μW), nonresonant microwave sensing signals. The detailed examination of the properties of the helical configuration verifies the theoretical predictions. Where it has been possible to measure the properties of the plasma discharge exactly, such as helix rotational frequency and discharge tube radius, excellent quantitative agreement between theory and experiment is found. Where it has only been possible to estimate the plasma parameters, such as electron temperature and longitudinal gradients, good qualitative agreement between theory and experiment is found.