Probe wave system for studying excitation of Alfvén eigenmodes in the ion cyclotron range of frequency

Abstract

A probe wave system was constructed for studying the excitation of the Alfvén ion cyclotron ͑AIC͒ modes in the anchor cell of the GAMMA 10 tandem mirror. In the central cell, the AIC modes are spontaneously excited as axial eigenmodes due to the strong temperature anisotropy. In the anchor cell, the AIC modes were not observed though the anisotropy is the same as in the central cell. The axial profiles of the magnetic field strength and plasma parameters in the anchor cell are different from those in the central cell. Eigenmodes are excited externally in the AIC frequency range by injecting probe waves. This suggests the AIC modes are unstable in the anchor cell and grow to the detectable level when boundary conditions are realized.