Charge exchange spectroscopy system calibration for ion temperature measurement in KSTAR

Abstract

The charge exchange spectroscopy (CES) system including collection assemblies, lens design, and cassettes for the KSTAR experiment was installed to obtain profiles of the ion temperature and the toroidal rotation velocity from charge exchange emission between plasma ions and beam neutrals near the plasma axis by using a modulated neutral beam and a background system. We can measure the charge exchange spectra of an impurity line such as the 529 nm line of carbon VI to get ion temperature and rotation profiles in KSTAR. The CES and background systems will have absolute intensity and spectral calibrations using a calibrated source and various spectral lamps. The calibration was done inside the tokamak after all CES systems are installed and the optical systems are slid into the cassettes. This requires that the diagnostic systems are installed near the vacuum vessel inside the cryostat maintaining the superconducting state of the superconducting coils. Repeated spectral calibrations of the spectrometer and charge coupled device for CES will be made in the diagnostic room during the experimental campaign. We show a detailed description of the KSTAR CES system, how to calibrate, and the results of calibration.