Upgrade of the FIDA Spectroscopy system at the NSTX-U Tokamak*

Fast-ion transport studies in spherical tokamaks like the National Spherical Torus Experiment Upgrade (NSTX-U) are of particular interest as these devices allow for high beta operation with fast-ion velocities well above the Alfven velocity. Here we present the design and first calibration results of upgrades to two existing double-slit Fast-Ion D-Alpha (FIDA) spectrometers and a new single channel Czerny-Turner FIDA spectrometer to be employed at the NSTX-U facility. First, the existing double-slit spectrometers have been refurbished by installing a newer scientific CMOS camera and replacing lenses that have been found to introduce scattered light. The spectrometers are now each able to handle 32 channels and utilize significant demagnification of the entrance slit to allow for camera operation with 10 ms time resolution. Secondly, the Czerny Turner type spectrometer uses a custom F/2.74 lens design for a single spatial channel and demonstrates excellent spectral resolution of ~0.1 nm, high photon throughput, and frame-rates near 9.5 kHz for detailed studies of the fast-ion confinement in NSTX-U. Synthetic spectra predicted with the TRANSP and FIDASIM codes show that the spectral ranges of these spectrometers will sufficiently cover FIDA, Halo, and beam emission in NSTX-U.