Nuclear Fusion ( IF 3.3 ) Pub Date : 2021-07-23 , DOI: 10.1088/1741-4326/ac108d Y. Ping 1 , P. Amendt 1 , K. Baker 1 , V.A. Smalyuk 1 , H. Chen 1 , S. Khan 1 , E.P. Hartouni 1 , D. Ho 1 , O. Jones 1 , O.N. Landen 1 , N. Lemos 1 , J. Lindl 1 , J. Moody 1 , A. Nikroo 1 , M. Rubery 1 , D.J. Schlossberg 1 , M. Stadermann 1 , D. Strozzi 1 , R. Tipton 1 , B. Woodworth 1 , P.J. Adrian 2 , B. Lahmann 2 , J. Frenje 2 , R. Petrasso 2 , C. Kong 3 , N. Rice 3 , C. Wild 4
In the laser-driven indirect drive scheme for inertial confinement fusion, the energy coupling efficiency from the hohlraum to the capsule is typically ∼10% due to limited capsule sizes in order to attain quasi-round implosions with currently available laser energy in cylindrical hohlraums. Recent experiments at the National ignition Facility (NIF) showed ∼30% energy coupling efficiency to aluminum capsules by using a rugby-shaped hohlraum to accommodate larger capsules. This paper reports the first experiment at the NIF demonstrating ∼30% energy coupling to a 3 mm-diameter high-energy-density carbon capsule in a rugby hohlraum with a two-shock laser pulse shape. By comparing the measured bang time with a simulated hydrodynamic scaling, ∼430 kJ coupling is inferred with 1.36 MJ laser drive. The symmetry of the hot spot was observed to be more oblate than simulations predicted. X-ray images taken at late time show strong emission at the laser entrance hole of the rugby hohlraum, indicating a closure earlier than expected, which could contribute to the oblate hot spot shape. Implementing wavelength detuning or modifying the hohlraum shape to tune the symmetry in future experiments would allow symmetric implosions while maintaining the high energy coupling.
中文翻译:
在 NIF 上的金色橄榄球空腔中,高密度碳胶囊的能量耦合效率达到 30%
在惯性约束聚变的激光驱动间接驱动方案中,由于胶囊尺寸有限,从空腔到胶囊的能量耦合效率通常为~10%,以便在圆柱形空腔中利用当前可用的激光能量实现准圆形内爆。最近在国家点火装置 (NIF) 进行的实验表明,通过使用橄榄球形状的空腔来容纳更大的胶囊,铝胶囊的能量耦合效率约为 30%。这篇论文报告了 NIF 的第一个实验,展示了约 30% 的能量耦合到橄榄球空腔中的 3 mm 直径高能量密度碳胶囊,具有两次冲击激光脉冲形状。通过将测量的爆炸时间与模拟的流体动力学标度进行比较,可以推断约 430 kJ 的耦合与 1.36 MJ 的激光驱动。观察到热点的对称性比模拟预测的更扁。后期拍摄的 X 射线图像显示,橄榄球空腔的激光入口孔处有强发射,表明关闭时间早于预期,这可能有助于形成扁圆的热点形状。在未来的实验中实施波长失谐或修改空腔形状以调整对称性将允许对称内爆,同时保持高能量耦合。