Study on divertor heat flux of L-H transition with LHCD and NBI in EAST

Abstract

An infrared (IR)/visible endoscope system was built on the Experimental Advanced Superconducting Tokamak (EAST) in 2014. The temperature distributions of the lower divertor have been measured. Based on the IR data of EAST, the heat fluxes on the lower outer divertor were calculated with a code named DFLUX developed by ASIPP, aimed to research the heat fluxes on divertor under different auxiliary heating schemes. Peak heat fluxes of the lower outer divertor show a reduction of several hundred kilowatts during L-H transition and an increase of nearly 1MW/m2 during H-L transition, corresponding with the Dα signal, electron density and plasma stored energy under LHCD heating scheme(PLHCD∼1.9MW). The heat flux profile of lower outer divertor was broad before the first L-H transition and narrowed rapidly after L-H transition but without obvious change during the next L-H transitions. Narrower heat flux profile and higher heat flux than LHCD heating scheme were induced by NBI heating scheme (0.9MW at first and 1.7MW before L-H transition), with the heat flux profile narrowed after L-H transition. The study results can afford reference for the optimization of H-mode plasma discharge experiments on EAST.