Improved charge exchange spectroscopy on the Joint European Torus for ion temperature and rotation velocity profiles

The Joint European Torus (JET) edge charge exchange recombination spectroscopy diagnostic has recently been enhanced to extend its spatial coverage and improve its time resolution. Two identical periscopes have been installed on opposite ports so that they have perfectly symmetrical views of the edge plasma. This matched viewing geometry allows both the poloidal and toroidal components of the impurity ion rotation velocity to be accurately resolved. These measurements play a crucial role in the understanding of the physics of edge phenomena such as edge transport barrier formation and enhanced light microscopes. The diagnostic also has a more central view of the plasma with a third periscope that faces up towards the top of the vessel. This is a new configuration for the diagnostic and allows the poloidal rotation velocity profile to be measured further in towards the plasma core than previously possible. The new upward facing, core plasma viewing arrangement provides the advantage that the spatial evolution of the internal transport barrier can be tracked from its formation. An additional spectrometer-detector system doubles the total number of charge exchange recombination spectroscopy lines of sight that are analyzed and improves time resolution from 50 to 10 ms