In the GAMMA 10 tandem mirror, ion cyclotron range of frequency heating has been used effectively in the central cell. The ion temperature becomes several 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 peaks near the cyclotron resonance layer and estimated pressure profile in the axial direction is consistent with the profile from a diamagnetic loop array. Strong temperature anisotropy can drive an Alfvén ion cyclotron ͑AIC͒ mode unstable. In a typical discharge, the temporal evolution of the endloss high energy ions has strong correlation with that of the AIC-mode amplitude. The enhancement of the loss of high energy ions due to the AIC mode is suggested.
GAMMA 10 experiments have advanced in high density experiments after the last IAEA fusion energy conference in 2000 where we reported the production of the high density plasma through use of ion cyclotron range of frequency heating at a high harmonic frequency and neutral beam injection in the anchor cells. However, the diamagnetic signal of the plasma decreased when electron cyclotron resonance heating was applied for the potential formation. Recently a high density plasma has been obtained without degradation of the diamagnetic signal and with much improved reproducibility than before. The high density plasma was attained through adjustment of the spacing of the conducting plates installed in the anchor transition regions. The potential confinement of the plasma has been extensively studied. Dependences of the ion confinement time, ion-energy confinement time and plasma confining potential on plasma density were obtained for the first time in the high density region up to a density of 4×1018 m−3.
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