UC San Diego

Neutron time-of-flight (nTOF) detectors are commonly used for fast neutron detection on nuclear fusion plasma experiments in high energy density physics. The 4.6-kJ dense plasma focus (DPF) at UC San Diego can generate neutron yields of up to ~108. Two nTOF detectors radially situated at 1.3 m from the DPF are each composed of an EJ-204 plastic scintillator and an Hamamatsu R7724 photomultiplier tube. Several hundred experimental shots have been taken over the course of four different anode types. Of those, 203 shots with neutron data were selected to calibrate both nTOF detectors. A Be-activation detector generates absolute neutron yield data and has a lower detection limit of 1.1·106 neutrons. The latter is used to calibrate the signal areas in the nTOF data, and directly correlate those signal areas with the number of neutrons incident on the detector at its radius from the DPF. This preliminary analysis finds that the two nTOF detectors have approximate efficiencies of 8100 and 1700 photons per DD neutron, respectively. Further analysis can improve the correlation as well as investigate the cross-calibration between the two nTOF detectors more thoroughly.