Charged-particle beam implosion of fusion targets

This paper discusses the calculated behavior of fusion targets consisting of solid shells filled with DT gas, irradiated by high power electron or ion beams. The current required for breakeven with gold shells is 500-1000 MA, independent of target radius and nearly independent of beam voltage in the 1/2-1 MeV range. Above 1 MeV the breakeven current increases because of the increased bremsstrahlung production by the beam electrons. By using a diamond ablator and a gold pusher, the breakeven current is reduced to 220 MA. The ion current required for breakeven (about 10 MA of protons) is independent of proton voltage above 10 MeV with gold shell targets. Below 10 MeV the range of the proton becomes too short for efficient coupling, and the required current increases, but the power does not. Various aspects of the symmetry and stability of the implosion are discussed. We find that the relatively long deposition lengths of electrons result in relatively small growths of the Rayleigh-Taylor instability during the acceleration of the pusher, resulting in a relatively stable implosion.