Using Real-Time Nuclear Activation Detectors for Measuring DD-Neutron Yields on the NIF*

The NIF has 48 Real-Time Nuclear Activation Detectors (RTNADs) distributed around the target chamber capable of measuring DT neutron yields with high precision. In this work we extend this functionality to DD neutrons using a nuclear reaction that occurs in the detector's scintillator material. The corresponding decay of the activated material has a very short half life of 5 seconds which necessitates rapid data collection immediately following an experiment. In this regime, deadtime can be very high (>50%) adding significant uncertainty in the measurement. To combat this, we have developed a deadtime model that can self-consistently describe the measured data. Initial results show reasonable agreement with DD neutron yields from neutron time-of-flight spectrometers (nTOFs).