Conceptual design, development and preliminary tests of a Compact Neutron Spectrometer for the JET experiment

The Compact Neutron Spectrometer (CNS) is a Joint European Torus (JET) Enhancement Project, devoted to measure the neutron emission spectra in different plasmas scenarios. The results obtained by CNS during next JET campaigns will contribute to the development of neutron spectrometers suitable for applications in the International Thermonuclear Experimental Reactor (ITER). The main components of the instrument are a liquid scintillation detector (BC501A) for neutron (n) and gamma-ray (¿) detection and a Digital Pulse Shape Discrimination (DPSD) acquisition system. The CNS will enable recording and discrimination of n and ¿ pulse height spectra up to total count rates of ~10⁶ s^-1. After unfolding the neutron spectra can be determined with energy resolution <2% at 14 MeV and <4% at 2.5 MeV. The work done in the last two years by ENEA-Frascati and Physikalisch-Technische Bundesanstalt (PTB) respectively in the assembly of DPSD and scintillation detector, along with the preliminary tests and results performed on both the components and the assembled spectrometer are presented.