Neutron diagnostics for laser fusion experiments

Three different neutron diagnostic instruments used to acquire data for judging the performance of D-T filled laser-fusion targets are described. Large scintillation detectors and a neutron activation system are used to measure the number of 14-MeV reaction neutrons emitted from a target, and a 45-meter neutron time-of-flight spectrometer is used to determine the fuel ion temperature. The scintillation detectors are used for neutron yields above ten thousand per shot, and neutron activation by the Cu(n,2n)-63Cu-62 reaction is used as an additional diagnostic device for yields above one hundred million per shot. Application of these techniques to laser-fusion measurements data taken at the Argus laser facility, and neutron diagnostics being prepared for the Shiva facility are discussed. Comparison of experimental yield data obtained for a number of laser-fusion targets show that neutron yield values obtained by the neutron systems and alpha-particle yields by TOF methods are in good agreement.