Study on the impact of N/Ne impurity seeding on neutrals in HL-2A tokamak

Abstract

Impurity seeding is the major technology for divertor power exhaust. In this work, the impact of N and Ne impurity seeding on the behavior of neutrals in the divertor region was systematically studied based on the HL-2A tokamak. The results demonstrated a strong correlation between the target deuterium molecular density and the target electron temperature after N/Ne impurity seeding. In addition, it was found that deuterium atoms played a more important role in reducing the electron temperature of the target after the Ne impurity injection at Te <15 eV than that of N seeding. Moreover, the deuterium radiation atom excitation channel was stronger after the Ne impurity injection than the N impurity. It was also found that the N impurity radiation in the divertor can reach several times of the Ne impurity radiation under the high upstream density conditions. The core effective charge number Zeff was larger after the Ne impurity injection than N impurity injection, indicating that the Ne impurity was more likely to dilute the plasma.