Relaxation of pressure anisotropy due to Alfvén-ion-cyclotron fluctuations observed in ion-cyclotron-range-of-frequency–heated mirror plasmas

Abstract

Alfvén-ion-cyclotron modes are generated over a wide range of anisotropy parameter ${\mathrm{\beta }}_{\mathrm{\perp }}$(${\mathit{T}}_{\mathrm{\perp }}$/${\mathit{T}}_{\mathrm{\parallel }}$ ${)}^2$ in ICRF-heated central cell plasmas of the GAMMA 10 tandem mirror. The fluctuations are observed at a small driving force in the convectively unstable region predicted theoretically in an infinite plasma. Before reaching the β limit of ${\mathrm{\beta }}_{\mathrm{\perp }}$=3.52×(${\mathit{T}}_{\mathrm{\parallel }}$/${\mathit{T}}_{\mathrm{\perp }}$ ${)}^2$, above which the absolute instability is predicted, relaxation of pressure anisotropy is observed for the first time by use of an array of diamagnetic loops together with a Faraday cup and secondary-electron emission detectors.