Upgrade of the edge Charge Exchange Recombination Spectroscopy system at the High Field Side of ASDEX Upgrade

Abstract

The upgrade of the high field side (HFS) edge charge exchange recombination spectroscopy (CXRS) system of ASDEX Upgrade is presented. This diagnostic provides temperature, rotation and radiance measurements of impurity species by taking advantage of the gas puff based CXRS technique (GP-CXRS). The system is formed by a fast piezoelectric valve, that injects thermal neutrals into the plasma, and two optical heads. The localized gas injection together with properly aligned lines of sights (LOS) lead to a high spatial resolution of 5–19 mm. Fast gas puff modulation allows a precise subtraction of the passive part of the signal. The existing poloidal optical head has been replaced with a new one to increase the radial resolution. The number of lines of sight (LOS) of the poloidal optical head has been increased from 8 to 16 covering around 7 cm of the plasma edge at the HFS. The same radial range is also viewed by a toroidal optical head. The neutral deposition, needed to calculate the impurity density profile, has been modelled using the FIDASIM code. A realistic gas puff geometry has been implemented in the code. The first measurements of impurity temperature, rotation and radiance utilizing the upgraded diagnostic are presented.