ICRF mode conversion flow drive on Alcator C-Mod

摘要

We have carried out a detailed study of ion cyclotron range of frequency (ICRF) mode conversion (MC) flow drive on the Alcator C-Mod tokamak including its dependence on plasma and RF parameters. The flow drive efficiency is found to strongly depend on the ~3He concentration in D(~3He) plasmas, a key parameter separating the ICRF minority heating regime and MC regime. At +90° antenna phasing (waves in co-I_p direction) and dipole phasing (waves symmetrical in both directions), we find that △V_0 the change in the core toroidal rotation velocity, is in the co-I_p direction, increases with RF power and with I_p (opposite to the l/I_p intrinsic rotation scaling). The flow drive efficiency decreases at higher plasma density and also at higher antenna frequency. The observed flow drive efficiency in H-mode has been small due to the unfavourable density scaling. The flow drive effect at -90° phasing appears to be saturated or decrease at high RF power. The up-down asymmetry in the MC to the ion cyclotron wave may be the key to understand the flow drive mechanism.