LMJ-PETAL laser装置的新不透明度测量原理
New opacity measurement principle for LMJ-PETAL laser facility
摘要：
星震学揭示了数千颗太阳型恒星的一些内部性质，但太阳地震声速十年来一直令人困惑，因为它与标准太阳模型（SSM）的预测不一致。对这种分歧的解释之一可能是在处理从太阳核心到表面的辐射传输。由于其他恒星也采用同样的框架，因此，为了确保温度T > 2 - 10 $^6$ K和密度$ρ$ > 0.2 g/cm $^3$时的能量传输，必须精确检查光子与每种物质相互作用截面的可靠性。在本文中，我们提出了一种新的技术，以达到在太阳辐射内部发现的温度和密度的域。该技术称为双烧蚀前沿（Double Ablation Front，简称DAF），其基于激光能量向X射线的高转换，这是由于在1.5 $\times$ 10 $^{15}$ W/cm $^2$和4 $\times$ 10 $^{15}$ W/cm $^2$之间的激光强度照射的缓和Z材料。除了电子前沿之外，这种高转换在缓和的Z材料中产生第二烧蚀前沿。在这两个前沿之间有一个密度和温度的平台，我们利用它来加热铁或氧化物的样品。第一次模拟实现的流体动力学代码CHIC表明，这种技术允许达到相当于一半的太阳辐射区的条件下，在时间和空间上都具有高稳定性。我们研究了测量铁和氧吸收光谱的可能性。
英文摘要：
Stellar seismology reveals some interior properties of thousands of solar-type stars but the solar seismic sound speed stays puzzling since a decade as it disagrees with the Standard Solar Model (SSM) prediction. One of the explanations of this disagreement may be found in the treatment of the transport of radiation from the solar core to the surface. As the same framework is used for other stars, it is important to check precisely the reliability of the interacting cross sections of photons with each species in order to ensure the energy transport for temperature T > 2 - 10$^6$ K and density $ρ$ > 0.2 g/cm$^3$. In this paper, we propose a new technique to reach the domain of temperature and density found in the solar radiative interior. This technique called the Double Ablation Front (DAF) is based on a high conversion of the laser energy into X-rays thanks to moderated Z material irradiated by laser intensity between 1.5 $\times$ 10$^{15}$ W/cm$^2$ and 4 $\times$ 10$^{15}$ W/cm$^2$. This high conversion creates, in addition to the electronic front a second ablation front in the moderated Z material. Between the two fronts there is a plateau of density and temperature that we exploit to heat a sample of iron or of oxide. The first simulations realized with the hydrodynamic code CHIC show that this technique allows to reach conditions equivalent to half the radiative zone of the Sun with high stability both in time and space. We examine the possibility to measure both iron and oxygen absorption spectra.
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