Irradiation uniformity of spherical heavy-ion-driven ICF targets

Estimates are presented for non-uniformity of energy deposition in spherical-shell ICF targets driven by beams of high-energy heavy ions. The principal consideration is shown to be the difference in penetration depth of ions entering at different angles relative to the surface of the sphere. Calculations are reported for 12-, 20-, and 32-beam symmetrical illumination. A rough assessment of required implosion symmetry indicates that a trade-off will exist between target gain and number of beams. A brief discussion of possible angular pressure-smoothing mechanisms is included.