High Density Plasma Production with Phase Controlled ICRF Antennas in the Gamma-10 Central Cell

This manuscript reports the high density plasma production with a pair of phase controlled ion-cyclotron range of frequency antennas in GAMMA 10. For the plasma production, the Radio Frequency (RF) power (~10 MHz) is coupled to the fast Alfvén wave in the central cell. The antenna-plasma coupling depends strongly on the antenna structure. In this study, according to the numerical prediction, a pair of double half-turn and Nagoya Type-III antennas is adopted for the excitation of the fast wave. The antennas are driven at the same frequency with controlling their phase difference. It is observed that an optimum phase difference exists in the present density range. The density increases with the RF power and the gas-fuelling rate, when the phase difference is set to the optimum value. The considerable increase in the density was obtained up to twice as large as the conventional value.