[Application of Extreme-Ultraviolet Ar Spectra Analysis in the Study of Divertor Impurity Screening in EAST Tokamak].

ABSTRACT

Divertor impurity injection on Tokamak is the most important means to achieve divertor impurity screening efficiency. In this paper, a fast-response extreme-ultraviolet (EUV) spectrometer is used to monitor the Ar emission lines during the EAST(Experimental Advanced Superconducting Tokamak)divertor Ar injection experiment. Based on the NIST(National Institute of Standards and Technology)atomic spectrum database, the emission lines from different ionized Ar ions in 2～50 nm wavelength range, e.g. Ar Ⅳ, Ar Ⅳ-Ⅺ and Ar ⅩⅣ-ⅩⅥ, are being identified. Ar ⅩⅥ 35.39 nm and Ar Ⅳ 44.22 nm with the ionization energy of 918.4 and 59.6 eV respectively are being monitored during the experiment with Ar puffing to observe the behavior of Ar impurities in different regions in plasmasimultaneously. The preliminary analysis on divertor impurity screening efficiency is carried outwith the time evolution of intensities of two Ar emission lines. The results of experiment puffing from the same gas puffing inlet (e. g. from lower outer target inlet) and withdifferent plasma configurations (e. g. lower single null, upper single null) show that the screening effect on the impurity injected from the divertor region is better thanfrom the main plasma region; the screening effect of lower divertor and particle pumping by internal cryopump installed in lower divertor is stronger than upper divertor.