ICRF heating and TAE modes in reactor relevatn JT-60U discharges

摘要

Second harmonic ICRF minority heating in deuterium negative shear discharges was found to efficently heat bulk plasmas inside the transport barrier. The tail ion stroed energy due to ICRF heating was comparable to that of a positive shear discharge. Toroidicity induced Alfven eigenmodes (TAE) were stable when a strong internal transport barrier was formed in the negative shear discharges. TAE modes (90-110kHz, n = 5-8) were observed only after the density profile had broadened, because of sequential partial collases. The behaviour of TAE modes in negative shear plasmas was analysed with the NOVA-K code. It was found that the stability of TAE modes is sensitive to the gap alignment just inside q_min and the calculations agree qualitatively with the experimental results. An n= 0/m = 1 mode (approx 40kHz), driven by ICRF heating, was observed over a much wider parameter range than TAE modes in negative shear discharges. High power ICRF heating of a 4 MA hot ion H mode discharge with a 15 cm gap between the antenna and the plasma was demonstrated. The antenna operating voltage and the power density satisfied the design base of the ITER antenna. Control of TAE modes through the toroidal rotation profile control was validated.