ICRF mode conversion in three-ion species heating experiment and in flow drive experiment on the Alcator C-Mod tokamak

Abstract

In recent three-ion species (majority D and H plus a trace level of 3 He) ICRF heating experiments on Alcator C-Mod, double mode conversion on both sides of the 3 He cyclotron resonance has been observed using the phase contrast imaging (PCI) system. The MC locations are used to estimate the species concentrations in the plasma. Simulation using TORIC shows that with the 3 He level < 1%, most RF power is absorbed by the 3 He ions and the process can generate energetic 3 He ions. In mode conversion (MC) flow drive experiment in D( 3 He) plasma at 8 T, MC waves were also monitored by PCI. The MC ion cyclotron wave (ICW) amplitude and wavenumber k R have been found to correlate with the flow drive force. The MC efficiency, wave-number k of the MC ICW and their dependence on plasma parameters like T e0 have been studied. Based on the experimental observation and numerical study of the dispersion solutions, a hypothesis of the flow drive mechanism has been proposed.