Development of Charge Exchange Spectroscopy in LHD

Charge exchange spectroscopy is widely used in fusion plasma research as a method for measuring ion temperature distribution and plasma flow velocity. In the LHD, charge exchange spectroscopy has been applied to observe impurity density distribution, hydrogen/deuterium isotope ratio distribution, and distortion of the ion velocity distribution function using multiple systems that employ high-throughput spectrometers, multi-channel optical fibers, and high-speed image detectors. In the measurement of the hydrogen/deuterium ratio, we succeeded in the analysis by combining it with velocity distribution measurement using a conventional system. In the measurement of the ion velocity distribution function, we were able to grasp the overall situation by combining one with high spatial resolution and a system with high temporal resolution.