Enhanced core charge exchange recombination spectroscopy system on Joint European Torus

Charge exchange spectroscopy is a key diagnostic on the Joint European Torus for radial profiles of ion temperature, toroidal rotation, and impurity densities. This article describes the current status and the improvements made over the last five years. The current system consists of two periscopes looking at one of the two banks of neutral heating beams, ≅90 optical fibers defining viewing directions, and seven spectrometers with charge-coupled device (CCD) cameras. The upgrade has involved replacement of the two periscopes and windows, a doubling of the number of optical fibers (plasma viewing directions), new cameras for the existing spectrometers, improvements to the throughput and long-term stability of the five existing spectrometers, and the addition of two new high-throughput spectrometers with their CCD cameras from ORNL. This work has culminated in improved spatial resolution, increased sensitivity of all the plasma viewing channels (for some by a factor of ∼3 or more), and enhanced time resolution from 50 to around 10 ms