Analysis of Cavity Gas Conditions in Heavy-Ion Beam Fusion Reactors

The limits on the cavity gas density required for beam propagation and condensation times for material vaporized by target explosions can determine the maximum repetition rate of heavy-ion fusion (HIF) driven reactors. If the ions are ballistically focused onto the target, the cavity gas must have a density below roughly 3 × 10¹²cm^-3 at the time of propagation; other propagation schemes may allow densities as high as 1 Torr or more. In some reactor designs, several kilograms of material may be vaporized from the target chamber walls by target-generated X rays, raising the average density in the cavity to 3 × 10¹⁸ cm^-3 or more. A one-dimensional combined radiation hydrodynamics and vaporization and condensation computer code has been used to simulate the vaporization and condensation of material in the target chambers of HIF reactors. Repetition rates in excess of 1 Hz are possible in the three types of target chambers studied. Means of increasing allowable repetition rates are discussed.