间接驱动冷冻双壳层点火靶的设计和分析

双壳层靶中,由于燃料被高Z壳层包裹,其点火方式要求燃料整体点火,不同于单壳层中心热斑点火。结合点火条件和对于其中物理过程的认识,设计了间接驱动的冷冻双壳层点火靶。利用冷冻的氘氚(DT)燃料,可适当提高双壳层靶的燃料装量,获得和NIF装置条件下中心热斑点火靶相当的放能。间接驱动下,X射线烧蚀并驱动外壳层碰撞内壳层,把能量传递给内壳层,进而压缩和点燃冷冻的DT燃料。壳层碰撞过程是能量传递的关键,通过调整内外壳层的质量比,提高了碰撞效率,相应地降低了靶丸点火的能量需求。一维数值模拟分析了该点火靶的内爆过程及定性分析了其中的流体力学不稳定性。同时,也指出了泡沫中形成的辐射冲击波对内壳层的预热效应,即辐射冲击波的致稳效应,能够很好地抑制内壳层外界面处的不稳定性发展,进而会减弱高Z内壳层和燃料的混合。

Design and analysis of indirect-drive cryogenic double-shell ignition targets

Due to the fuel surrounded by a high-Z pusher, the double-shell target differs from the cryogenic single-shell case, and it requires volume ignition of the whole fuel. In the paper, the ignition condition for the fuel surrounded by a high-Z pusher is analyzed, and an indirect-drive cryogenic double-shell ignition target is designed and analyzed, which releases a comparable energy to the hot-spot ignition target to be performed at National Ignition Facility (NIF). The collision between the outer and inner shell is the key in the energy transport. By adjusting the ratio of the mass between the two shells, the efficiency of the energy from the outer shell to the inner shell can be highly elevated, with a purpose of reducing the size of the target and the required energy to achieve ignition. For the double-shell ignition, a new preheating mechanism by the radiative shock is pointed out, which can help stabilize the Rayleigh-Taylor (RT) instability occurring at the outer surface of the inner shell. The preheat of radiative shock, as a potential effect in double-shell target, should be seriously realized and underlined.