Spectral Analysis in EUV Range for Study of Core Impurity Behavior in HL-2A

Abstract

Extreme ultraviolet (EUV) spectroscopy has been developed for impurity diagnostics in HL-2A tokamak. The EUV spectrometer consists of an entrance slit, a holographic varied-line-space (VLS) grating, a back-illuminated charge-coupled device (CCD) and a laser light source for optical alignment. Spectral lines in wavelength region of 20-500 Å observed from HL-2A plasmas were analyzed to study the impurity behavior. Spectral and temporal resolutions used for the analysis were 0.19 Å at CV (2×33.73 Å) and 6 ms, respectively. It was found that carbon, oxygen and iron impurities were usually dominant in the HL-2A plasma. They almost disappeared when the siliconization was carried out. Although the EUV spectra were entirely replaced by the silicon emissions just after the siliconization, the emissions were considerably decreased with accumulation of discharges. Aluminum and neon were externally introduced into the HL-2A plasma based on laser blow-off (LBO) and supersonic molecular beam injection (SMBI) techniques for a trial of the impurity transport study, respectively. The preliminary result is presented for time behavior of EUV spectral lines.