Non-Uniformity of Heavy-Ion Beam Irradiation on a Direct-Driven Pellet in Inertial Confinement Fusion

Abstract

Heavy-ion-driven fusion (HIF) is a scheme to achieve inertial confinement fusion (ICF). Investigation of the non-uniformity of heavy-ion beam (HIB) irradiation is one of the key issues for ICF driven by powerful heavy-ion beams. Ions in HIB impinge on the pellet surface and deposit their energy in a relatively deep and wide area. Therefore, the non-uniformity of HIB irradiation should be evaluated in the volume of the deposition area in the absorber layer. By using the OK1 code with some corrections, the non-uniformity of heavy-ion beam irradiation for the different ion beams on two kinds of targets were evaluated in 12-beam, 20-beam, 60-beam and 120-beam irradiation schemes. The root-mean-square (RMS) non-uniformity value becomes σRMS = 8.39% in an aluminum mono-layer pellet structure and σRMS = 6.53% in a lead-aluminum layer target for the 12-uranium-beam system. The RMS non-uniformity for the lead-aluminum layer target was lower than that for the mono-layer target. The RMS and peak-to-valley (PTV) non-uniformities are reduced with the increase in beam number, and low at the Bragg peak layer.