间接驱动的内爆不对称性随腔长和时间变化的研究

Variations of implosion asymmetry with hohlraum length and time in indirect-drive inertial confinement fusion

在激光间接驱动惯性约束聚变中,为达到高密度压缩以实现点火,对靶丸内爆对称性和黑腔辐射场均匀性有严格的要求.为了研究内爆不对称性随腔长和时间的变化,实验中采用了三种不同尺寸的黑腔,利用X光分幅相机观测了靶丸燃料区自发光,获得了压缩变形过程和椭圆度变化规律,初步判断了在三种腔型中腔长1700μm的黑腔较接近神光III原型装置内爆对称性要求.根据视角因子程序计算得到辐射流不对称性随时间变化情况,通过一个简化的解析模型推导出内爆形变不对称性随时间变化过程,与实验结果大致符合.由此进一步分析了黑腔辐射场不均匀性的演化导致内爆不对称性随腔长和时间变化的物理机制.

In order to achieve the high density compression in laser indirect-drive inertial confinement fusion, the implosion symmetry and hohlraum radiation uniformity are strictly required. To study the variations of implosion asymmetry with hohlraum length and time, three kinds of hohlraum lengths are adopted in experiment. X-ray emission from capsule fuel is measured by an X-ray framing camera. Based on measured capsule compression process and ellipticity variation, it is preliminarily judged that the medium hohlraum of 1700 μm long is the closest to implosion symmetry demand of Shenguang III prototype laser facility. Time-resolved implosion asymmetry is derived from a simplified analytic model, in which used is the time-resolved hohlraum radiation nonuniformity derived from a view-factor code. The derived results of the time-resolved implosion asymmetry are basically in agreement with experimental results. The physical mechanism for how hohlraum radiation nonuniformity evolution induces the variations of implosion asymmetry with hohlraum length and time is analyzed.