Speaker
Description
The fast-ion deuterium Balmer-alpha (FIDA) spectroscopy diagnostic has been operated on KSTAR tokamak. KSTAR FIDA diagnostic system consists of two tangential viewing arrays covering both blue-shifted and red-shifted fast-ion charge-exchange spectra. Since the tangential viewing FIDA is sensitive to the emission from the passing fast-ions, primarily generated by the tangential NBI on KSTAR, the current KSTAR FIDA system is suitable for the fast-ion profile measurements. FIDA measurements from various discharge scenarios. This study shows analysis results of the FIDA spectra profile from the high fast-ion fraction scenario (FIRE mode: fast-ion-regulated enhancement mode) and the ELMy H-mode discharges. FIDA signal-to-background ratio is high for the FIRE mode discharges, and it is insensitive to the appearance of the chirping EPM instabilities. In the case of ELMy H-mode, edge FIDA signal intensity changes as the ELM crash occurs. Peaks in the edge FIDA intensity are not synchronized with the ELM crash events. It can be significant evidence for the ion-cyclotron emission (ICE). On the one hand, FIDA intensity does not change significantly during the ELM suppression case, implying that fast-ion transport at the edge is not severe. To enhance the contrast of the FIDA spectrum, a coronagraph-like cold D blocking module is inserted into the spectrometer and is operated with a motorized focusing component. In addition, an oblique-view FIDA array has been installed to cover the fast-ion velocity-space close to the trapped or passing-trapped boundary region.
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