Analysis of Target Implosion Irradiated by Proton Beam. I. : Beam Interaction With Target Plasma

概要

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Numerical simulations and analyses are given for the implosion of a hollow shell target driven by proton beams. The target consists of three layers of Pb, Al and DT. The Pb and Al layers play roles of a tamper and a pusher, respectively. The main part of the beam energy is deposited in the Al layer. But the process of deposition depends much on the distribution of incident angles and particle energies. As the Al layer is heated by proton beams, the layer expands and pushes the DT layer toward the target center. This kind of implosion motion is examined by using a similar solution for the slab model. To obtain an optimal velocity of the DT implosion, the optimal target size and optimal layer thicknesses are determined. The Rayleigh-Taylor instability accompanied by the implosion motion is investigated to be stable with respect to our target structure. The effect of inhomogeneities on implosion is shown to be severe. The fluctuation of the temperture in the Al layer must be less than 10% and the deviation of the pusher thickness from the average should be less than 4μm with a view to keeping a high target gain.