Study of the tungsten sputtering source suppression by wall conditionings in the EAST tokamak

Abstract

The steady fusion plasma operation is constrained by tungsten (W) material sputtering issue in the EAST tokamak. In this work, the suppression of W sputtering source has been studied by advanced wall conditionings. It is also concluded that the W sputtering yield becomes more with increasing carbon (C) content in the main deuterium (D) plasma. In EAST, the integrated use of discharge cleanings and lithium (Li) coating has positive effects on the suppression of W sputtering source. In the plasma recovery experiments, it is suggested that the W intensity is reduced by approximately 60% with the help of ∼35 h Ion Cyclotron Radio Frequency Discharge Cleaning (ICRF-DC) and ∼40 g Li coating after vacuum failure. The first wall covered by Li film could be relieved from the bombardment of energetic particles, and the impurity in the vessel would be removed through the particle induced desorption and isotope exchange during the discharge cleanings. In general, the sputtering yield of W would decrease from the source, on the bias of the improvement of wall condition and the mitigation of plasma-wall interaction process. It lays important base of the achievement of high-parameter and long-pulse plasma operation in EAST. The experiences also would be constructive for us to promote the understanding of relevant physics and basis towards the ITER-like condition.