H-Mode outside divertor free from peripheral disruption in Doublet III

The heating efficiency and the peripheral disruption of three distinctively different divertor configurtions were studied in Doublet III at a plasma current of 600 kA up to the neutral injection power of 7.5 MW. An outside divertor configuration with a good energy confinement (H-mode), which has a null point at the outside in the major radius and of which separatrix field lines divert to the outside wall, was observed. The discharges of the outside divertor configuration were free from the peripheral disruption characterized by H α / D α bursts and the stored energy was nearly proportional to the injection power up to 7.5 MW of NBI.