报告题目：Hybrid indirect-direct-drive ignition with double ablation fronts for inertial confinement fusion
报告人：范征锋博士 北京应用物理与计算数学研究所
报告时间 ：2012年12月13日（周四）下午14:30~16:00
报告地点：工学院1号实验楼210会议室 
主持人：段慧玲 特聘研究员

摘要：Recently, the National Ignition Facility (NIF) is able to deliver 1.9 MJ of 0.35-μm ultraviolet light at 500 TW. However, the National Ignition Campaign (NIC) experiments on it are facing challenges. Besides laser plasma instabilities (LPI), two major issues in implosion dynamics exist: (1) a strong rarefaction wave generated from the radiation ablating region seriously decreases the ablation pressure and limits the ability of increasing implosion velocity; (2) hydrodynamic instabilities are more severe than predicted causing hot spot asymmetry and material mixing. In this report, a new hybrid indirect-direct-drive ignition scheme is proposed: a cryogenic capsule encased in a hohlraum is first compressed by indirect-drive x-rays, and then accelerated and ignited by both direct-drive lasers and x-rays. The hybrid drive can create a double-ablation-front structure (consisting of a radiation ablation front and an electron ablation front) and a higher density plateau is formed between the two ablation fronts, which reduces the rarefaction at the radiation ablation front and greatly increases the drive pressure. As compared with conventional indirect drive, numerical simulations show that the hybrid drive can implode the capsule with a higher velocity (~4.4 × 107 cm/s) and a much lower convergence ratio (~25). It is also found that the hybrid-drive scheme is insensitive to the intrinsic low-mode drive asymmetries, and more importantly, it features low level of hydrodynamic instability growth, which benefits target fabrication and ignition robustness. Laser plasma instabilities need our further investigations in the future