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 (Ti,v∥) 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). Ti and v∥ 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 T/T≥1%.