Behavior of high energy ions in the GAMMA 10 tandem mirror

In the GAMMA 10 tandem mirror, ion cyclotron range of frequency heating has been used effectively in the central cell. The ion temperature becomes sev eral keV and an ion beta value is a few %. Semiconductor detectors are used for measurement of high energy protons in both parallel and perpendicular directions to the magnetic field line. Observed pitch angle distribution pe aks near the cyclotron resonance layer and estimated pressure profile in th e axial direction is consistent with the profile from a diamagnetic loop ar ray. Strong temperature anisotropy can drive an Alfven ion cyclotron (AIC) mode unstable. In a typical discharge, the temporal evolution of the endlos s high energy ions has strong correlation with that of the AIC-mode amplitu de. The enhancement of the loss of high energy ions due to the AIC mode is suggested. (C) 1999 American Institute of Physics. [S0034-6748(99)53001-3].