Abstract
<sec>Radiative shock is an important phenomenon both in astrophysics and in inertial confinement fusion. In this paper, the radiation properties of X-ray heated radiatve shock in xenon is studied with the simulation method. The radiative shock is described by a one-dimensional, multi-group radiation hydrodynamics model proposed by Zinn [Zinn J 1973 <i> J. Comput. Phys.</i> <b>13</b> 569]. To conduct computation, the opacity and equation-of-state data of xenon are calculated and put into the model. The reliabilities of the model and the physical parameters of xenon are verified by comparing the temperature and velocity of the radiative shock calculated by the model with those measured experimentally. </sec><sec>The evolution of the radiative shock involves abundant physical processes. The core of the xenon can be heated up to 100 eV, resulting in a thermal wave and forming an expanding high-temperature-core. Shortly, the hydrodynamic disturbances reach the thermal wave front, generating a shock. As the thermal wave slows down, the shock gradually exceeds the high-temperature-core, forming a double-step distribution in the temperature profile. </sec><sec>The time evolution of the effective temperature of the radiative shock shows two maximum values and one minimum value, and the radiation spectra often deviate from blackbody spectrum. By analyzing the radiation and absorption properties at different positions of the shock, it can be found that the optical property of the shock is highly dynamic and can generate the above-mentioned radiation characteristics. When the radiative shock is just formed, the radiation comes from the shock surface and the shock precursor has a significant absorption of the radiation. As the shock temperature falls during expansion, the shock precursor disappears and the radiation inside the shock can come out owing to absorption coefficient decreases. When the shock becomes transparent, the radiation surface reaches the outside edge of the high-temperature-core. Then, the temperature of the high-temperature-core decreases further, making this region also optically thin, and the radiation from the inner region can come out. Finally, the radiation strength falls because of temperature decreasing. </sec>
Highlights
the radiation properties of X-ray heated radiatve shock in xenon is studied with the simulation method
The radiative shock is described by a one-dimensional, multi-group radiation hydrodynamics model proposed by
the physical parameters of xenon are verified by comparing the temperature and velocity of the radiative shock calculated by the model
Summary
基于超构材料的Cherenkov辐射 Cherenkov radiation based on metamaterials 物理学报. 超精细结构效应对辐射光谱圆极化特性的影响 Hyperfine structure effect on circular polarization of X-ray radiation 物理学报. 球几何中辐射源粒子抽样方法的改进 Modification of method of sampling radiation source particle in spherical geometry 物理学报. 非磁化冷等离子体柱中的模式辐射特性分析 Analysis of mode radiation characteristics in a non-magnetized cold plasma column 物理学报. 本文使用的氙气辐射不 透明度数据采用 DCA/UTA 不透明度程序计算 [29]. 该程序中原子的能级结构采用细致组态近似 (detailed configuration accounting, DCA), 在计算谱线 跃 迁 时 , 使 用 UTA(unresolved transition array) 统计模型近似考虑细致能级的谱线结构 [30,31]. 实验中分别测量了 0.1 和 0.2 个标准大气压 (atm) 下氙气中辐射激波 的平均速度和温度. Zinn 模型对 0.1 atm 氙气的计算中, 辐射激波 的温度在 1 ns 时达到最大值, 约为 20 eV (由 380— 460 nm 波段的辐射反推, 其他可见光波段的计 算结果差异不大), 在实验测量中这一数值约为 18 eV (文献 [17] 的图 3), 模拟计算 2—4 ns 的激 波平均速度为 63 km/s, 与实验测量值 65 km/s 也很接近. 征, 图 6 截取 1 μs (图 6(a)) 和 6 μs (图 6(b)) 两个 时刻氙气的对外辐射光谱 (实线), 并与相同等效温 度下的黑体辐射光谱 (虚线) 作比较. 对比发现这 两个时刻高温氙气的辐射光谱明显偏离黑体辐射 光谱, 且不同时刻辐射光谱的形状也不一致. 由于 计算模型使用多群近似, 每个能群内的辐射强度被 平均化处理, 计算的辐射光谱不能显示气体辐射的 精细结构, 但相对黑体辐射光谱的偏离是明显的
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