Fusion neutron yield from a laser-irradiated heavy-water spray

The fusion neutron yield from a laser irradiated heavy water D2O spray target was studied. Heavy water droplets of about 150 nm diameter in the spray were exposed to 35 fs laser pulses at an intensity of 1 1019 W cm2. Due to the 10 50 times bigger size of the spray droplets compared to usual cluster sizes, deuterons are accelerated to considerably higher kinetic energies of up to 1 MeV. Neutrons are generated by the deuterons escaping from the plasma and initiating a fusion reaction within the surrounding cold plume of the spray jet. For each 0.6 J of laser pulse energy, 6 amp; 61620;103 neutrons are produced by about 1011 accelerated deuterons. This corresponds to a D d,n reaction probability of about 6 amp; 61620;10 8. Compared to cluster targets, the reaction probability in the spray target is found to be two orders of magnitude larger. This finding apparently is due to both the considerably higher deuteron energies and the larger effective target thickness in the spray target. The measured neutron yield per accelerated deuteron i.e., the D d,n reaction probability , is employed to compare and extrapolate the neutron emission characteristics from different target arrangements