Fast-ion D alpha diagnostic with 3D-supporting FIDASIM in the Large Helical Device

For understanding the physics of energetic particles, the deuterium experimental campaignsstarted in Large Helical Device (LHD) from March 2017. To investigate the behavior ofenergetic particles, a Fast-ion D Alpha (FIDA) diagnostic was installed on the LHD. In theFIDA diagnostic, the Doppler-shifted D alpha light from fast-neutrals are utilized as signals ofenergetic particles, where these fast-neutrals are produced by the charge exchange processbetween fast-ions in the plasma and actively injected neutrals by neutral beam (NB). Theadvantages of the FIDA diagnostic are the velocity and the spatially resolved measurement offast-ions at the crossing point between its line of sight (LOS) and the incident line of NB. Themost recent FIDASIM is enhanced to simulate signals produced in three-dimensional magneticconfigurations. The new version of FIDASIM uses the fast-ion distribution function producedby GNET as input to simulate FIDA signals at LHD. In order to validate the new version of thecode, measurements of radial profiles of fast-ions using the FIDA diagnostic are performed inmagnetohydrodynamic (MHD)-quiescent plasmas. The measured spectra are in good agreementwith the theoretical prediction by 3D-supporting FIDASIM at the center of the plasma(R = 3.5 m~3.7 m, reff/a99 = −0.28~0.05) on the LHD when the line averaged electron densityis ne_avg < 1.23 × 1019 m−3. On the other hand, the measured spectra are in disagreement withthe theoretical prediction by 3D-supporting FIDASIM at even the center of the plasma when theline averaged electron density is ne_avg ≥ 1.23 × 1019 m−3.
source:Citation Y. Fujiwara et al 2020 Nucl. Fusion 60 112014
source:https://doi.org/10.1088/1741-4326/abae84
identifier:0000-0003-2985-060X