Energy Resolution of LaBr3(Ce) Gamma-Ray spectrometer for Fusion Plasma Studies on JET

A new high efficiency, high resolution, fast G-ray spectrometer was recently installed at the JET tokamak. The spectrometer is based on a LaBr3(Ce) scintillator coupled to a photo multiplier tube. A digital data acquisition system is used to allow spectrometry with event rates in excess of 1MHz expected in future JET DT plasmas. However at the lower rates typical of present day experiments digitization can degrade the energy resolution of the system depending on the algorithms used for extracting pulse height information from the digitized pulses. In this paper the digital and analog spectrometry methods were compared for different experimental conditions. An algorithm based on pulse shape fitting was developed providing energy resolution equivalent to the traditional analog spectrometry method.
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