High energy density physics at AWE

AWE is tasked with supporting Continuous At Sea Deterrence (CASD) by certifying the performance and safety of the deterrent in the Comprehensive Test Ban Treaty (CTBT) era. Certification must be achieved by supplementing historical nuclear test data with use of computer calculations. AWE therefore regularly procures, installs and operates large supercomputers, and complements this with high end storage, network, visualisation and desktop systems that enable the supercomputers to be exploited effectively. This High Performance Computing (HPC) environment is useless without computer programmes or “codes” to run on it. Multi-physics algorithms are developed to solve the equations of compressible fluid flow coupled to transport algorithms and other required physics such as fusion burn. These state-of-the-art algorithms are in turn worthless without material property data. It is particularly challenging to obtain required material properties such as opacity and equation of state in the extreme conditions of interest. The requirements span timescales of many orders of magnitude and pressures up to Gigabars with temperatures ranging up to tens of millions of degrees. The regimes of hot dense matter (HDM) and warm dense matter (WDM) are pertinent, representing material that is heated while remaining at a density close to solid; similar conditions exist in the cores of large planets and in the sun. In some cases it is possible to harness the power of HPC to calculate the material properties but even if this is the case, it is always important to underpin calculated properties with measurements in appropriate conditions. Once the material property data have been incorporated into the multi-physics codes, meaningful calculations become possible. It is then necessary to carry out further experiments to validate the codes and indeed the designers who are using them. It turns out that an excellent way to meet many of the requirements for material property data an- to provide confidence in the validity of the algorithms is through experiments carried out on high power laser systems.