Studying High Pressure Matter with X-Ray Lasers

恒星环境又热又密，导致在高温下产生电离物质，并且原子间距离足够近，以至于特定离子的束缚状态受到其邻居的强烈影响，从而减少了电离原子所需的能量(这种现象被称为电离势抑制)。类似的情况也出现在惯性约束聚变太空舱的中心。我们团队的研究最近表明，我们可以使用位于加州SLAC的世界上最强大的x射线激光来制造200万度的固体密度物质，然后对其进行探测，以准确地找出电离势的值。令人惊讶的是，我们发现这些值与半个多世纪以来广泛使用的标准理论完全不同。在从头算量子计算的帮助下，我们开始理解为什么会出现这种情况，但还需要做更多的工作。在这个项目中，该学生将在实验室中进行进一步的实验，以制造“微型恒星”，并开始在类似于太阳中心一半的条件下对原子性质进行基本的量子计算。这一结果也可能对通过惯性聚变技术生产几乎无限的能源的探索产生直接影响，该组织与美国国家点火设施有着密切的正式联系。

Stellar environments are hot and dense, leading to ionized matter at high temperatures, and with interatomic spacings sufficiently close that the bound states of a particular ion are strongly influenced by their neighbours, reducing the energy needed to ionize the atom (a phenomenon known as ionization potential depression. Similar circumstances arise in the centre of inertial confinement fusion capsules. Research within our group has recently shown that we can use the world's most powerful x-ray laser, based at SLAC California, to make solid density matter at 2 million degrees, and then probe it to find out exactly the value of the ionization potentials. Surprisingly we found that the values were completely at odds with the standard theory that has been in wide use for over half a century. With the aid of ab initio quantum calculations we are starting to understand why this is the case, but much more work needs to be done. In this project the student will be engaged in further experiments to make 'miniature stars' in the laboratory, as well as embark on fundamental quantum calculations of the properties of atoms under similar conditions to those that exist half way to the centre of the sun. The results could also have a direct impact on the quest to produce virtually limitless energy via inertial fusion techniques, and the group has strong formal links with the US National Ignition Facility.