| Abstract: | The dominant wavelength range of edge impurity emissions moves from the visible range to the
vacuum ultraviolet (VUV) range, as heating power increasing in the Experimental Advanced
Superconducting Tokamak (EAST). The measurement provided by the existing visible
spectroscopies in EAST is not sufficient for impurity transport studies for high-parameters
plasmas. Therefore, in this study, a VUV spectroscopy is newly developed to measure edge
impurity emissions in EAST. One Seya-Namioka VUV spectrometer (McPherson 234/302) is
used in the system, equipped with a concave-corrected holographic grating with groove density
of 600 grooves mm–1. Impurity line emissions can be observed in the wavelength range of λ=50–700 nm, covering VUV, near ultraviolet and visible ranges. The observed vertical range
is Z=?350–350 mm. The minimum sampling time can be set to 5ms under full vertical
binning (FVB) mode. VUV spectroscopy has been used to measure the edge impurity emission
for the 2019 EAST experimental campaign. Impurity spectra are identified for several impurity
species, i.e., lithium (Li), carbon (C), oxygen (O), and iron (Fe). Several candidates for tungsten
(W) lines are also measured but their clear identification is very difficult due to a strong overlap
with Fe lines. Time evolutions of impurity carbon emissions of CII at 134.5nm and CIII at
97.7nm are analyzed to prove the system capability of time-resolved measurement. The
measurements of the VUV spectroscopy are very helpful for edge impurity transport study in the
high-parameters plasma in EAST. |
