Development of 2.5MeV neutron spectrometer for helical deuterium plasma experiment

A neutron spectrometer with associated particles coincident time-of-flight technique is being developed for deuterium plasma experiments in a large helical fusion device. In this experiment, the energy resolution less than 7% and the detection efficiency larger than 10^-6 counts/neutron is required for the plasma diagnostics based on neutron spectrometry. The prototype spectrometer was partly assembled and the detector performance was experimentally checked at Fusion Neutron Source of Japan Atomic Energy Agency. By selecting the events with low energy loss from all coincident events in the radiator, the experimental results showed that the neutron spectrometer could achieve an energy resolution around 6.7% under a detection efficiency of 3.3×10^-7 counts/neutron for DD neutrons. To improve the detection efficiency, the configuration of the neutron spectrometer system was designed toward the DD plasma experiment at an existent large helical fusion device.