The study of plasma physics covers a huge range of scales and applications. It is core to the development of laboratory experiments such as fusion power, new light sources and the next generation of particle accelerators. On the largest scales it is fundamental to our understanding of astrophysics. CCP-Plasma was established in 2007 with the aim of pooling the collective expertise across these disparate subjects and developing core plasma physics simulation codes, and training packages, for UK science. CCP-Plasma includes staff from UK universities, UKAEA, Culham, RAL and AWE. A full list can be found on the Members page.
The UK has a long history of research in high intensity laser plasma interactions through the Central Laser Facility and the associated university groups. In the last decade developments in the fields of relativistically intense laser pulses and the fast igniter fusion concepts have challenged computational plasma physics. Plasmas with such intense electromagnetic fields must be described by a fully kinetic model of the particle distribution function in 7 dimensions (3 space, 3 momentum and time). Computational models exist, both via Monte Carlo 'particle' methods and via continuum approximations of the electron distribution function. In the fast igniter concept a 'long' laser pulse is used to compressed fuel that is then ignited by a relativistic 'short' pulse. Point design for these targets requires the coupling of relativistic kinetic models with long time-scale radiation hydrodynamics codes. These in turn may require input from equation of state calculations of dense plasmas and detailed modeling of shock propagation via MD techniques. Both particle and continuum methods parallelise via domain decomposition and, with some caveats on load balancing, the existing models scale well to very large machines. The CCP-Plasma projects include the development of 2D and 3D models to meet the application needs within the UK for the study of exciting applications in laser driven fusion energy, compact electron and ion accelerators and novel techniques to improve the efficiency of X-ray light sources.
Magnetically Confined Plasmas
Magnetic fusion researchers in the next decade will work towards the grand scientific challenge of understanding plasma turbulence. This subject is important for fusion, as turbulence dominates the performance limiting loss rates of heat and particles. Progress towards understanding and controlling plasma turbulence will assist in optimising the performance of fusion devices and may be exploited in the international fusion experiment ITER that is soon to start construction in France. UK scientists are engaged in plasma turbulence studies, developing several UK codes and collaborating with the authors of codes originally developed in Europe and the US. Gyrokinetic codes in the UK successfully exploit current supercomputers and scale efficiently to 1,000-10,000 cores. Software effort will be required both to ensure that the code algorithms maximally exploit the available hardware, and to improve multi-dimensional data visualisation that is so valuable for developing understanding. Modelling for the scientific challenges of fusion science is likely to contribute to progress in other areas of plasma physics such as solar physics and astrophysics.
Figure 1 (i) Electrostatic potential perturbations in a local flux tube gyrokinetic code. (ii) Contour plot of the perturbed electrostatic potential in the poloidal plane during the linear phase of a global gyrokinetic simulation.
Astrophysical and Space Plasmas
The computational challenges for space and astrophysics are similar to those outlined above in laboratory plasmas. CCP-Plasma is working on 3D PIC codes that can be used for particle acceleration and wave damping studies in space plasmas. At the fluid level CCP-Plasma members are working on shock capturing schemes, including GR metrics, and radiation hydrodynamics codes. The exchange of ideas, algorithms and codes between the laboratory plasma community and space and astrophysics community is planned to lead to a suite of core plasma simulation codes, documented and maintained within the UK which will benefit both research and PhD/PDRA training programmes.