Heisenberg reputedly said on his death bed, When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first. Understanding turbulence remains a fundamental open question in physics that is nowadays accessible to high performance computing (HPC).Plasma (ionised gas) is the fourth state of matter that dominates our observable universe, and burns in stars through nuclear fusion reactions to produce energy and the elements. Laboratory experiments replicate these processes, aiming to harness terrestrial nuclear fusion for energy, and an advanced approach exploits toroidal magnetic fields to confine hot plasma at temperatures >100 million K. Fusion requires good confinement, and this is limited by collisions and plasma turbulence. Collisional processes cause an irreducible minimum plasma loss rate that is understood theoretically, but larger losses, due to turbulent processes, are observed in devices. Recent experiments find dramatically enhanced confinement regimes with higher core pressures, where losses are strongly reduced in localised regions of plasma, approximately to the level predicted by collisional theory. In the region of the internal transport barrier (ITB), turbulence is strongly suppressed. There is much scope for optimising fusion devices through controlling turbulence.Calculations of magnetised plasma turbulence parallelise efficiently, and recent advances in HPC permit high fidelity first principles based calculations. HPC is essential because of the high dimensionality of the problem (5-D in kinetic approaches) and the huge ranges of scales of the physics processes in space and time. This proposal is for scientists at UKAEA Culham, Edinburgh, Oxford, Warwick and York to exploit the EPSRC national supercomputer HECToR to perform magnetised plasma turbulence simulations using state-of-the-art kinetic and fluid models. Multiscale simulations, ideally suited to HECToR, will resolve fundamental plasma processes that span in space from the short length scale associated with particle gyration around the magnetic field (eg the ion Larmor radius rho_i ~O(5)mm) to the device minor radius a (~O(1)m), and in time from the lifetime of turbulent eddies (~O(10^-6)s) to the energy confinement time (~O(1s)). We will approach our objectives using complementary models: (i) coupling multiple local kinetic turbulence simulations self-consistently with a transport solver to track the slower evolution of macroscopic plasma properties, (ii) global kinetic simulations and (iii) applying the two-fluid-MHD plasma model to describe turbulence at scales between rho_i and a. The key scientific issues to be explored include: (1) probing the fundamental triggers for the suppression of turbulence and the onset of transport barriers(2) assessing the relative importance of turbulent fluctuations on different length scales, and probing the cascade of turbulent energy between these scales(3) comparing model predictions with experiments (including spherical tokamaks like the UK experiment MAST), and suggesting routes to optimise plasma performance in future devices (eg the next step burning plasma experiment ITER).This internationally leading project team is well placed to make unique contributions towards addressing these important and challenging scientific questions. Our proposed simulations will parallelise to exploit 1000s of computational cores efficiently, and indeed require access to a state of the art supercomputer like HECToR. The science tackled is relevant to fusion and astrophysics. Success in achieving these ambitious scientific objectives will address long standing grand challenges, and will have a high international impact.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Summary For a lot of academic and industrial research into nuclear energy, using NNUF and other facilities, it is important that neutron-irradiated material of known provenance is available. Getting samples irradiated in reactors is both time-consuming and expensive, and as much use as possible should be made of existing material. There is a wide range of surveillance and other samples in the UK, owned by organisations like the Nuclear Decommissioning Authority (NDA), EDF Energy and Rolls-Royce. Establishing either a central or distributed archive of a selection of this material that can be accessed by researchers has been identified as a priority by the UK Government's Nuclear Innovation and Research Advisory Board (NIRAB). The archive is the second item in the table of favoured investments in EPSRC's NNUF Phase 2 call. While the Irradiated Materials Archive Group (IMAG), comprising universities, National Nuclear Laboratory (NNL), UK Atomic Energy Authority (UKAEA), NDA and other stakeholders, has developed this concept, further work is required before the key stakeholders are in a position to decide if and how to proceed. Options could range from leaving the material where it presently is and having systems that enable individuals to ascertain the material and pedigree available, and request samples for their research, to bringing samples from locations in the UK to dedicated stores at Sellafield (higher activities) and UKAEA's Culham site (low-activity). It is, therefore, proposed that the archive is taken forward in two stages. Stage 1 is an option study and the subject of this proposal. At the end of Stage 1, key stakeholders - including EPSRC, the owners of the material and the managers of proposed stores - would decide whether to proceed and with which option. Stage 2 would require a new proposal for funding based on cost estimates established in Stage 1. However, an upper bound for the latter is indicated in this proposal. Important considerations in Stage 1 include: ascertaining what material samples are available and which are of interest to UK researchers; logistical issues including ownership and liability, transport and waste disposal; and the requirements for the archive database(s). An attractive option for the last of these may be for NDA and other owners of material to manage their own databases in a way that permits users to interrogate these and request samples. UKAEA, NNL and the University of Bristol (UoB) propose to undertake Stage 1 and produce an options appraisal for EPSRC and its NNUF Management Team, having consulted all stakeholders. This would take 19 months and require £524,000. Wide-ranging support for this proposal is confirmed by letters from Dame Sue Ion (first chair of NIRAB), the CEO of the Henry Royce Institute for Advanced Materials and AWE. The NDA has been consulted in the drafting of this proposal and expressed its willingness to collaborate in the project, as has Rolls-Royce in its letter of support. The US has had a national archive for some years and learning from its experience would be part of this project; a letter confirming the value of the archive is from the Director of Nuclear Science User Facilities at Idaho National Laboratory.