Proton imaging of hohlraum plasma stagnation in inertial-confinement-fusion experiments
Proton imaging of hohlraum plasma stagnation in inertial-confinement-fusion experiments
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DOI：
10.1088/0029-5515/53/7/073022
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发表时间：
2013-07-01
期刊：
影响因子：
3.3
通讯作者：
Nikroo, A.
中科院分区：
文献类型：
--
作者：
Li, C. K.;Seguin, F. H.;Nikroo, A.
对从黑腔壁吹出的等离子体的空间结构和时间演化进行质子射线照相，揭示了填充气体如何压缩壁吹出、抑制等离子体射流形成并阻止等离子体在黑腔内部停滞。证明了自发产生的电场和磁场在黑腔动力学和胶囊内爆中的作用。由于能斯特效应，热通量会与磁场快速对流，其速度比膨胀壁吹出的等离子流体的对流速度快 10 倍（v(N) 类似于 10(v)）。这会抑制从激光束路径中的气体区域到周围冷气体的热传递，导致局部等离子体温度升高。实验表明，两种材料（气体和壁）的相互渗透是由于经典的瑞利-泰勒不稳定性而发生的，因为较轻的、减速的电离填充气体推动较重的、膨胀的金壁吹出。该实验提供了填充气体对 X 射线驱动内爆影响的物理见解，并将影响国家点火设施正在进行的点火实验。
Proton radiography of the spatial structure and temporal evolution of plasma blowing off from a hohlraum wall reveals how the fill gas compresses the wall blow-off, inhibits plasma jet formation and impedes plasma stagnation in the hohlraum interior. The roles of spontaneously generated electric and magnetic fields in hohlraum dynamics and capsule implosions are demonstrated. The heat flux is shown to rapidly convect the magnetic field due to the Nernst effect, which is shown to be similar to 10 times faster than convection by the plasma fluid from expanded wall blow-off (v(N) similar to 10(v)). This leads to inhibition of heat transfer from the gas region in the laser beam paths to the surrounding cold gas, resulting in a local plasma temperature increase. The experiments show that interpenetration of the two materials (gas and wall) occurs due to the classical Rayleigh-Taylor instability as the lighter, decelerating ionized fill gas pushes against the heavier, expanding gold wall blow-off. This experiment provides physics insight into the effects of fill gas on x-ray-driven implosions, and would impact the ongoing ignition experiments at the National Ignition Facility.