Measurements of neutron fluxes from tokamak plasmas using a compact neutron spectrometer

A compact neutron spectrometer based on the BC-501A liquid organic scintillator was applied to neutron measurements at the TUMAN-3M tokamak. The spectrometer was calibrated using measurements from the ion beam of the cyclotron accelerator. Neutron spectra were measured during discharges using a neutral deuterium beam injection into the TUMAN-3M D-plasma. An energy distribution of the neutrons from the plasma that hit the spectrometer was obtained from the measured BC-501A instrumental spectra by the DeGaSum code using detector response functions obtained in the course of the calibration. This allowed for the estimation of the 2.45 MeV neutron yield and the evaluation of both the time evolution of the DD fusion rate and the characteristic time of the injected deuterium slowing down in discharges with neutral beam injection heating.