Fast-ion Dα spectroscopy diagnostic at KSTAR

• Published in: Review of scientific instruments 2021-04, Vol.92 (4), p.043504-043504
• Main Authors: Yoo, J. W., Kim, J., Lee, M. W., Kang, J., Ko, W.–H., Oh, S. G., Ko, J., Lee, J. H., Nam, Y. U., Jung, L., Park, B. H., Yoon, S. W.
• Format: Article
• Language: English
• Subjects: Charge coupled devices; Curved beams; Doppler effect; Neutral beams; Perturbation; Radiance; Scientific apparatus & instruments; Spectra; Spectrum analysis
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/5.0040559

A fast-ion Dα (FIDA) diagnostics system was installed for core and edge measurements on KSTAR. This system has two tangential FIDA arrays that cover both blue- and redshifted Dα lines (cold: 656.09 nm) in active views along the neutral beam 1 A centerline. The spectral band is 647–662.5 nm, and it covers the Doppler shift of the emission from the maximum energy of the neutral beam (100 keV). A curved filter strip with a motorized stage adequately prevents saturation of the electron multiplying charge-coupled device signal by the cold Dα line from the plasma edge. From comparisons of the measured spectra and FIDASIM modeling code, the FIDA spectra are well matched quantitatively. Moreover, the first measurements show that the FIDA radiance agrees with the neutron rate in the time trace during external heating and perturbation. In addition, responses are observed in the core FIDA radiance during the edge-localized mode cycle.