Dynamic symmetry of indirectly driven inertial confinement fusion capsules on the National Ignition Facilitya)
Dynamic symmetry of indirectly driven inertial confinement fusion capsules on the National Ignition Facilitya)
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DOI：
10.1063/1.4876609
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发表时间：
2014-05
影响因子：
2.2
通讯作者：
R. Town;D. Bradley;A. Kritcher;O. Jones;J. R. Rygg;R. Tommasini;M. Barrios;L. Benedetti;L. B. Hopki
中科院分区：
文献类型：
--
作者：
R. Town;D. Bradley;A. Kritcher;O. Jones;J. R. Rygg;R. Tommasini;M. Barrios;L. Benedetti;L. B. Hopki
为了实现点火使用惯性约束聚变，重要的是控制增长的低模式的不对称性，因为胶囊被压缩。了解热点和周围燃料层形状随时间的演变对优化内爆性能至关重要。在美国国家点火装置（NIF）上进行了一项研究内爆过程中不对称性来源和量化对称性的设计和实验活动。I. Moses等人，等离子体16，041006（2009）]。我们已经构建了一个大型的模拟数据库，在不同的时间间隔应用的不对称性。对数据库的分析表明，需要测量和控制内爆过程中的热点形状、面密度分布和对称性摆动。最后滞止期间热点的形状是用自发射的时间分辨成像来测量的，并且关于滞止时燃料形状的信息可以从康普顿射线照相术获得[R. Tommasini等人，等离子体18，056309（2011）]。在NIF上首次测量了充气和低温燃料分层胶囊的二维飞行X射线照片，以推断胶囊上辐射驱动的对称性。这些结果已被用来修改黑腔的几何形状和波长调谐，以改善飞行中内爆的对称性。我们还扩大了我们的冲击计时能力，通过增加额外的镜子内的再入锥，允许同时测量冲击对称性在三个位置上的一个单一的拍摄，提供不对称信息勒让德模式4。通过诊断的形状几乎每一步的内爆，我们估计，形状通常减少约50%的点火实验中的融合产额。
In order to achieve ignition using inertial confinement fusion it is important to control the growth of low-mode asymmetries as the capsule is compressed. Understanding the time-dependent evolution of the shape of the hot spot and surrounding fuel layer is crucial to optimizing implosion performance. A design and experimental campaign to examine sources of asymmetry and to quantify symmetry throughout the implosion has been developed and executed on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)]. We have constructed a large simulation database of asymmetries applied during different time intervals. Analysis of the database has shown the need to measure and control the hot-spot shape, areal density distribution, and symmetry swings during the implosion. The shape of the hot spot during final stagnation is measured using time-resolved imaging of the self-emission, and information on the shape of the fuel at stagnation can be obtained from Compton radiography [R. Tommasini et al., Phys. Plasmas 18, 056309 (2011)]. For the first time on NIF, two-dimensional inflight radiographs of gas-filled and cryogenic fuel layered capsules have been measured to infer the symmetry of the radiation drive on the capsule. These results have been used to modify the hohlraum geometry and the wavelength tuning to improve the inflight implosion symmetry. We have also expanded our shock timing capabilities by the addition of extra mirrors inside the re-entrant cone to allow the simultaneous measurement of shock symmetry in three locations on a single shot, providing asymmetry information up to Legendre mode 4. By diagnosing the shape at nearly every step of the implosion, we estimate that shape has typically reduced fusion yield by about 50% in ignition experiments.