HIGH-GAIN DT TARGETS FOR HEAVY-ION BEAM FUSION

In a parametric study of reactor size DT targets driven by beams of heavy ions it was found that spark ignition and high energy gains can be achieved in four-layer single-shell targets irradiated by a non-shaped box pulse of 10 GeV Bi-209 ions. With an input energy of E(in) congruent-to 6 MJ delivered in t(in) less than or similar 10 ns, one-dimensional energy gains of G greater than or similar to 400 are possible in the optimum cases. It is shown that, to obtain spark ignition and high energy gain, two conditions must be necessarily met: (1) a high enough implosion velocity, U(infinity) greater than or similar to 6.2 x 10(7) OMEGA-1/2 cm/s, must be reached, and (2) the fuel compression must be accomplished with a low enough pusher/fuel mass ratio, M(p)/M(DT) less than or similar 5-7 (OMEGA is a dimensionless parameter determined by the density distribution in the compressed target core). It was found also that when the [rhoDELTAr] of the cold part of the compressed fuel is congruent-to 2-5 g/cm2, the main portion of the fuel is ignited owing to the heating by 14 MeV neutrons emitted from the central hot region.