Neutron capture in laser-fusion pellets

Investigating the feasibility of obtaining slow neutron fluencies sufficient for multiple-capture nucleosynthesis, we have applied a Monte Carlo technique to determine the moderation of neutrons in a superdense laser-energized fusion pellet. We studied pellets of varying chemical composition and structure ranging in size from $\ensuremath{\rho}R\ensuremath{\sim}1 \mathrm{to} 50$ g/${\mathrm{cm}}^{2}$ and found our results to be rather insensitive to the parametrization of the hydrodynamic motion. That is, the neutron spectra were largely unaffected by reasonable variations of peak density, time of disassembly, and shape of the density profile. A useful method of improving the ratio of moderated to unmoderated neutrons was to dilute the thermonuclear fuel with hydrogen and/or the addition of a beryllium reflector. We also calculated the ratio of fission, neutron capture, and ($n, p$) reactions in pellets seeded with traces of $^{238}\mathrm{U}$ target material.