H-mode investigations in DIII-D

DIII-D is a large tokamak (major radius R = 1.67 m, minor radius a = 0.67 m), capable of producing vertically elongated limiter and divertor plasmas with high plasma current at modest toroidal field (B/sub T/ = 2.2 T on axis). To date, maximum plasma currents achieved are 3.0 MA in limiter plasmas (elongation in excess of 2.0), 2.0 MA in divertor plasmas (elongation 1.9). The DIII-D divertor is a reactor-compatible open divertor design, with no separate divertor chamber and no coils in vacuum. The divertor plates are two toroidal bands of carbon tiles on the bottom of the vacuum vessel. Deuterium plasmas are heated by hydrogen neutral beams (75 keV, coinjection only) and electron cyclotron heating /1/. Power levels to date are 6 MW (beam) and 1.0 MW (ECH). H-mode discharges, H-mode thresholds, and Edge Localized Modes have been investigated for this system.