Test of prototype ITER vacuum ultraviolet spectrometer and its application to impurity study in KSTAR plasmas

To optimize the design of ITER vacuum ultraviolet (VUV) spectrometer, a prototype VUV spectrometer was developed. The sensitivity calibration curve of the spectrometer was calculated from the mirror reflectivity, the grating efficiency, and the detector efficiency. The calibration curve was consistent with the calibration points derived in the experiment using the calibrated hollow cathode lamp. For the application of the prototype ITER VUV spectrometer, the prototype spectrometer was installed at KSTAR, and various impurity emission lines could be measured. By analyzing about 100 shots, strong positive correlation between the O VI and the C IV emission intensities could be found.