Ion cyclotron range of frequency heating on the Tokamak Fusion Test Reactor*

The complete ion cyclotron range of frequency (ICRF) heating system for the Tokamak Fusion Test Reactor (TFTR) [Fusion Tech. 21, 1324 (1992)], consisting of four antennas and six generators designed to deliver 12.5 MW to the TFTR plasma, has now been installed. Recently a series of experiments has been conducted to explore the effect of ICRF heating on the performance of low recycling, supershot plasmas in minority and nonresonant electron heating regimes. The addition of up to 7.4 MW of ICRF power to full size (R∼2.6 m, a∼0.95 m), helium‐3 minority, deuterium supershots heated with up to 30 MW of deuterium neutral‐beam injection has resulted in a significant increase in core electron temperature (ΔT_e=3–4 keV). Simulations of equivalent deuterium–tritium (D–T) supershots predict that such ICRF heating should result in an increase in β_α(0)∼30%. Direct electron heating has been observed and has been found to be in agreement with theory. The ICRF heating has also been coupled to neutral‐beam heated plasmas fueled by frozen deuterium pellets. In addition ICRF heated energetic ion tails have been used to simulate fusion alpha particles in high‐recycling plasmas. Up to 11.4 MW of ICRF heating has been coupled into a hydrogen minority, high‐recycling helium plasma and the first observation of the toroidal Alfvén eigenmode (TAE) instability driven by the energetic proton tail has been made in this regime.