Proton-boron-11 fusion reactions induced by heat-detonation burning waves

Proton-boron-11 is the clean fusion reaction par excellence, but it is very difficult to exploit it because of the very high ignition temperature of t his reaction and its moderate fusion yield. In this paper, a proposal is ma de to induce these reactions by a heat-detonation wave that expands across a compressed target. The front of the wave has a double-layer structure, wi th a first front driven by electron heat conduction and a second front heat ed by alpha-particle energy deposition. Both fronts create a hot plasma whe re the stopping power is dominated by ions. The wave is originated by an ig nitor triggered by an ultraintense lightning beam. This beam can be made of photons (laser), plasma (ramjets), or ions (proton beams, borane clusters) . Proton beam shots of 10(22) W/cm(2) and several GA for some picoseconds w ould be needed for this purpose. The supersonic propagation of the fusion w ave and the ignitor requirements are analyzed in this paper. The main concl usion is that the burning wave can only propagate if a substantial fraction of the radiation losses from the already burning fuel is reabsorbed in the colder fuel. It is calculated that for densities larger than few thousands g/cm(3) most of the bremsstrahlung radiation created in the hot plasma can be reabsorbed by the Compton effect in a region of 1 g/cm(2) optical thick ness of the surrounding compressed and cold fuel.