The role of neutrons in the performance of ICF targets

In most ICF target simulation calculations, alpha and other charged particles are assumed to be reabsorbed in the plasma whereas neutrons are often allowed to escape without interaction. However, in reactor-size targets, neutrons lose about the same amount of energy in the DT fuel as α-particles and can considerably influence the burn characteristics of the target and the reactor blanket performance. Results with a simple adiabatic model and time-dependent neutron transport calculations are presented. The total gain obtained for the HIBALL target is 157 for both the simple adiabatic model and the time-dependent neutron transport calculation. With the free neutron escape approximation the gain was calculated to be 179. Thus, neglecting the neutron fuel interaction overpredicts the pellet gain by about 15%. The strong moderation of the neutron has a marked influence on the blanket/breeding ratio. (author)