Neutron time-of-flight measurements on the national ignition facility

Summary form only given. Neutron time-of-flight (nToF) instruments are used to provide data on the performance of National Ignition Facility (NIF) fusion experiments. Detectors are located at 4.5 and 20 meters from the center of the target chamber with a 3.9 meter detector to be installed soon. These instruments are used to measure the total neutron emission, temperature of the fuel, time of peak emission (bang time), and areal density of the compressed fuel ρr). This talk will focus on data from the 20 meter detectors which are Xylene based liquid scintillators coupled to micro-channel plate photomultipliers. A figure of merit defined by the ratio of number of neutrons from 10 to 12 MeV divided by the number of neutrons between 13 and 15 MeV, called the down-scatter-ratio (DSR), is used to infer ρr. Analysis techniques using both time domain and energy domain data are discussed showing limitations and error analysis of both methods. Simulated data for an improved detector based on an organic crystal scintillator show that improvements to both scintillator decay and recording fidelity improve the precision of the DSR measurement.