Conceptual Design, Development and Preliminary Tests of a Compact Neutron Spectrometer for the JET Experiment

A Compact Neutron Spectrometer (CNS) has been developed to measure the neutron emission spectra in Joint European Torus (JET) fusion plasma experiments. The spectrometer, based on a liquid scintillation detector (BC501A), is equipped with a Digital Pulse Shape Discrimination (DPSD) acquisition system for neutron (n) and gamma-ray (γ) separation. The CNS enables recording the n and γ pulse height spectra (PHS) up to total count rates of ~10⁶ s^-1. Energy resolution, after PHS unfolding, will be <; 2% for 14 MeV neutrons and <; 4% for 2.5 MeV neutrons. The work done by ENEA-Frascati and Physikalisch-Technische Bundesanstalt (PTB) respectively in the assembly and test of DPSD and scintillation detector, along with the first results obtained by the spectrometer in JET plasma experiments are presented. The experience obtained with CNS in JET will contribute to the development of neutron spectrometers suitable for applications in the International Thermonuclear Experimental Reactor (ITER).