Studying High Pressure Matter with X-Ray Lasers

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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.