Xuele Zhao, C. Sang, Qing-Gang Zhou
Mar 25, 2020
Plasma Physics and Controlled Fusion
The external Ne impurity seeding has been applied to reduce the heat flux to the divertor target as well as plasma temperature to prolong the lifetime of the EAST upper tungsten (W) target. The erosion of the W target during the Ne seeding in different divertor operation regimes has been assessed by using the semi-empirical formula, while the plasma background was provided by SOLPS modeling. The simulation results showed that the Ne impurity played a critical role in the W erosion, which depended strongly on the operation regimes. By increasing the Ne seeding rate, the discharge regime was varied from the attached to detached condition. During the attached regime, the insufficient seeded Ne impurity could reduce the heat flux to the target, but the erosion of the W target was obviously enhanced, which may shorten the target lifetime. By the sufficient impurity seeding, the detached condition could be achieved, and the W target erosion was obviously suppressed. The high-power discharge brings great challenge to the W target lifetime, and the erosion is mainly induced by Ne and D ions. The contribution of each species changes greatly with different Ne seeding rates. In addition, the lifetime of the EAST upper W divertor has also been evaluated in different operation regimes during high input power discharge.