High performance H mode plasmas at densities above the greenwald limit

摘要

Densities of up to 40/100 above the Greenwald limit are reproducibly achieved in high confinement (H_ITER89P=2) ELMing H mode discharges. Simultaneous gas fuelling and divertor pumping were used to obtain these results. Confinement of these discharges, similar to moderate density H mode, is characterized by a stiff temperature profile, And is therefore sensitive to the density profile. A particle transport model is presented that explains the roles of Divertor pumping and geometry for access to high densities. The energy loss per ELM at high density is a factor of Five lower than the predictions of an earlier scaling, based on data from lower density discharges.