Optical diagnostic to measure ion temperature and parallel velocity fluctuations on the Tokamak Fusion Test Reactor

A high-throughput, high-frequency charge exchange recombination spectroscopy diagnostic (HF-CHERS) has been developed to give localized measurements of ion temperature and parallel velocity microturbulence (T̃i,ṽ∥) in the plasma core of the Tokamak Fusion Test Reactor (TFTR). HF-CHERS uses an interference filter spectrometer to measure intensity fluctuations simultaneously over several wavelength intervals of the line shape of the n=8–7 transition of C+5 (529 nm). T̃i and ṽ∥ are deduced from the moments of the emitted line shape. Using the beam emission spectroscopy optics on TFTR, measurements are made with 1–2 μs time resolution and ≊2 cm spatial resolution. The initial implementation of the diagnostic is expected to be sensitive to temperature fluctuations of T̃/T≥1%.