Fundamental and second harmonic hydrogen fast-wave heating on DIII-D

Ion cyclotron resonance heating (ICRH) with fast waves has been investigated on D3-D in both the fundamental hydrogen minority (32 MHz, 2.14 T) and second harmonic hydrogen majority (60 MHz, 1.97 T) regimes. The main purpose of these experiments was to characterize the fast wave coupling and propagation in preparation for upcoming fast wave current drive (FWCD) experiments. For the fundamental minority regime, the electron and ion heating, global confinement, and radiated power fraction are compared for ICRH and NBI discharges with Paux ∼ 1 MW. The ICRH experiments were conducted using a four strap antenna which was designed for current drive experiments. The antenna is fed by a single 2 MW 30--60 MHz transmitter. For ICRH experiments, either (0,0,0,0) or (0,π,0,π) phasing was used. The launched parallel index of refraction for (0,π,0,π) phasing is |n parallel | ∼ 21 at 32 MHz, and |n parallel | ∼ 11 at 60 MHz. 7 refs., 8 figs