ICRF heating in several regimes on TFTR

Over the past year, the two ICRF antennas on TFTR have been used to apply rf powers up to a level of 6 MW. Impurity generation at the antennas has continued to be negligible for the out-of-phase toroidal rf current strap array employed, even at the highest power levels where the average power density at one antenna has exceeded 10 MW/m². The higher operating power levels have supported explorations of all three plasma regimes of interest - the high-recycling gas-fueled regime, the low-recycling neutral-beam-heated supershot regime, and the low-recycling pellet-fueled regime. Noteworthy results include: ICRF sawtooth stabilization has been demonstrated in all three regimes; fusion reactivity has been significantly enhanced at approximately constant Q in the supershot regime; and efficient core heating at n_e(0) ≈ 2.4 × 10¹⁴ cm^-3 has been demonstrated in the pellet-fuelded regime. Extrapolations of these results to 12.5 MW operations in the D-T phase of TFTR, which is planned to provide relatively high β_α (approximately 0.5%) supershots in support of α physics studies and hot high density pellet-fueled regimes in support of ClT operations, are discussed briefly.