The Creation and Diagnosis of Solid-State Matter at Multi-TeraPascal Pressures

We aim to exploit our expertise in laser-induced dynamic compression and x-ray diffraction to make the first ever structural studies of solid matter above 1 TPa (10 megabars) using the JANUS, OMEGA, and National Ignition Facility (NIF) laser platforms in the US. At such pressures, the compression energy is sufficient to break all chemical bonds, providing a regime where new physics and chemistry are predicted to occur. By developing optimised target designs and x-ray diffraction facilities, we will collect high-quality diffraction data on nano-second timescales, and, aided by theory and computation, will determine the structures and phase transitions in a number of fundamental materials to an upper pressure of 3 TPa - almost 10 times higher than the maximum pressure attainable using static compression techniques. We plan to apply these developments to (1) studies of the structures and transitions in carbon (diamond) to 3 TPa, searching for transitions to the metallic BC8 phase, and the creation of super-hard metastable phases of carbon at ambient pressure; (2) studies of the 'simple' metals Na and Li to 3 TPa, searching for metal-insulator and insulator-metal transitions, and the appearance of electride structure-types as valence electrons and cores on neighbouring atoms are forced to overlap; and (3) studies of the onset of "cold-melting" and a liquid ground-state in lithium as a result of the relative enhancement of the zero-point energy at high compression.

The development of methods to create and probe solid matter above 1 TPa will have a direct impact on AWE plc, who are extremely interested in knowing how materials respond under compression to multi-megabar pressures. AWE are currently beginning the start-up phase of their ORION laser platform, and the development of an x-ray diffraction platform that could be utilised on this laser would have considerable impact on AWE's research programmes. Such work underpins the UK's nuclear deterrent.

This project will utilise high-powered laser platforms - including the multi-terrawatt National Ignition Facility (NIF). Students and postdocs working on this project will gain a unique set of skills, and, if funded, the project would result in the training of more young UK scientists in the use of multi-kJ nanosecond laser systems (OMEGA and NIF) than have been produced hitherto. We believe that the UK needs to invest in the training of the next generation of scientists who will be the users of these novel laser sources. We note that during the timescale of this project there is every expectation that NIF will achieve ignition (fusion energy gain). While the consequences of this are hard to judge in advance, the high-power laser community in the UK and Europe are fully expecting a strong push for laser fusion energy to follow. This has been given recent impetus by the memorandum of understanding signed by the UK to collaborate with AWE and LLNL to facilitate technical exchanges which could lead to the design, development and deployment of power plants based on laser fusion energy. Having young researchers directly trained in the use of the technology such as NIF and OMEGA will undoubtedly increase the UKs impact in this new field.