H-modes on COMPASS-D with high-power ECRH

Abstract

Recent high-power electron-cyclotron resonance heating (ECRH) H-mode experiments on COMPASS-D have used fundamental high-power ECRH to access high densities. Within the operating range set by the H-mode density threshold and ECRH accessibility, H-mode power thresholds are significantly higher than expected from ITER scalings, and show a contrary dependence on density. Energy confinement is somewhat lower than that suggested by the present ITER scalings, but correction for incomplete RF absorption may be needed. Complex H-mode and ELM behaviour is observed.