Development of gamma-ray spectrometers optimized for runaway electron bremsstrahlung emission in fusion devices

An optimized hard X-ray (HRX) spectrometer was designed to collect information from Bremsstrahlung emission in the MeV range runaway electrons (RE) generated during disruptions. The detector is based on a cerium doped lanthanum bromide scintillator crystal (LaBr3:Ce) coupled with a photomultiplier tube. The diagnostic allows for measurements of high hard X-ray fluxes in excess of 1 MHz with a wide dynamic range up to 20 MeV. The diagnostic was tested at the tokamak ASDEX Upgrade. The results achieved are promising and suggest the possibility of inferring information on the runaway electron energy distribution in tokamaks using deconvolution techniques.