Diamond detector for high rate monitors of fast neutrons beams

A fast neutron detection system suitable for high rate measurements is presented. The detector is based on a commercial high purity single crystal diamond (SDD) coupled to a fast digital data acquisition system. The detector was tested at the ISIS pulsed spallation neutron source. The SDD event signal was digitized at 1 GHz to reconstruct the deposited energy (pulse amplitude) and neutron arrival time; the event time of flight (ToF) was obtained relative to the recorded proton beam signal t0. Fast acquisition is needed since the peak count rate is very high (~800 kHz) due to the pulsed structure of the neutron beam. Measurements at ISIS indicate that three characteristics regions exist in the biparametric spectrum: i) background gamma events of low pulse amplitudes; ii) low pulse amplitude neutron events in the energy range Edep = 1.5-7 MeV ascribed to neutron elastic scattering on 12C; iii) large pulse amplitude neutron events with En < 7 MeV ascribed to 12C(n,α)9Be and 12C(n,n')3α.