Ar. Piriz et S. Atzeni, HEAVY-ION FUSION-TARGETS WITH DIFFUSE SPHERICAL RADIATION CONVERTER, Nuovo cimento della Società Italiana di Fisica. A. Nuclei, particles and fields, 106(12), 1993, pp. 1893-1899
Spherically symmetric targets for indirect-drive heavy-ion fusion are
studied, in which the fusion capsule is enclosed in a low-density thic
k spherical shell, where the ion beams are stopped and their energy is
converted into thermal radiation. The thermal radiation then drives t
he implosion of the fusion capsule, with mininum hydrodynamic coupling
between the energy deposition region and the ablation layer. The cond
itions for effective hydrodynamic decoupling have been derived. It is
found that with the use of heavy ions with energy about or below 8 GeV
, the beam-to-fuel energy coupling efficiency can be as large as in fo
reseen conventional hohlraums. On the other hand, these targets only a
llow for a low dynamic range of pulse shaping, which results in rather
poor entropy shaping and modest fuel gain. Robust targets have been d
esigned, which achieve energy gain G approximate to 30, when driven by
shaped pulses of 12.5 MJ of 8.5 GeV Bi ions. Inclusion of a high-dens
ity pusher, which increases the fuel compression leads to higher gain
at lower beam energy, but two-dimensional simulations demonstrate the
extremely violent instability of the fuel-pusher interface.