Gamma-ray spectrometry, comprising NaI(Tl) and BGO detectors, is a routine JET diagnostic used for fast-ion and a-particle physics studies. Measurements of fusion-born a-particles in JET 'trace tritium' discharges showed that an upgrade of the Data Acquisition System (DAQ) is needed to improve the energy and temporal resolution of the g-ray measurements in high performance dd- and dt-discharges. The JET DAQ system for g-ray measurements based on conventional ADCs has a relatively low counting rate limit, about 50kHz. This limitation is linked to dead-time losses during the data collection, due to Pulse Height Analysis (PHA) and pile-up effects.