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Details of Grant 

EPSRC Reference: EP/R034737/1
Title: Multiscale turbulent dynamics of tokamak plasmas
Principal Investigator: Wilson, Professor H
Other Investigators:
Phelps, Professor ADR Dickinson, Dr D Cziegler, Dr I
Ronald, Dr K Vann, Professor RG McMillan, Dr BF
Parra Diaz, Dr FI Cowley, Professor S Barnes, Dr M
Schekochihin, Professor A
Researcher Co-Investigators:
Dr PA Hill
Project Partners:
UK Atomic Energy Authority
Department: Physics
Organisation: University of York
Scheme: Programme Grants
Starts: 01 July 2018 Ends: 30 June 2023 Value (£): 4,349,473
EPSRC Research Topic Classifications:
Fusion Plasmas - Laser & Fusion
Plasmas - Technological
EPSRC Industrial Sector Classifications:
Energy
Related Grants:
Panel History:
Panel DatePanel NameOutcome
18 Apr 2018 Programme Grant Interviews - 19 and 20 April 2018 (Physical Sciences) Announced
Summary on Grant Application Form
Plasma turbulence underpins a wide range of phenomena, including the formation of stars and galaxies; the properties of the solar wind, and - the focus of this programme - the confinement of plasmas in tokamaks. It is complicated by feedback mechanisms that couple space and time scales spanning several orders of magnitude. The full problem is extremely challenging, and so to make progress for real world applications we must develop reduced models that capture the essential physics. The goal of our proposed programme is to address this by advancing our understanding of these multi-scale interactions at a fundamental science level. This will be achieved by coupling analytic theory, advanced computation and experimental capabilities, including the newly upgraded MAST-U tokamak.

Plasma turbulence is complicated by the fact that there are at least two types of interacting "fluids" - electrons and ions - and these are charged. Fluctuations in density therefore drive charge separation and hence fluctuations in the electrostatic field, while fluctuations in velocity drive currents and hence fluctuations in the magnetic field. These fields then couple the relative motions of the electron and ion "fluids". The situation is further complicated by the rich variety of waves that a magnetised plasma supports, and the resonances that exist when the phase velocity of a wave matches the particle velocity. To properly treat these resonances requires knowledge of the particle velocity distribution; this, in turn, requires either a kinetic or an advanced fluid approach - a daunting task.

Turbulence, typically at the millimetre-centimetre scale in tokamaks, interacts in a complex way with the global equilibrium profiles (density, temperature and flow gradients, for example), which are on the metre-scale. To quantify the complex, multi-scale feedback mechanisms between tokamak plasma turbulence and profiles, and so provide a predictive capability for the quasi-steady final states, we will address and integrate a number of topics. We will first learn how mean flows interact with electrostatic turbulence (ie neglecting fluctuations in the magnetic field), requiring coupling between fluctuations with characteristic scales ranging from the electron Larmor radius (sub-mm) through to the ion Larmor radius (few mm) and beyond (cm), to the system length scale of the profiles (m). Our new theory and simulations will inform experiments on MAST-U, exploiting two diagnostic instruments already planned for the device (beam emission spectroscopy and doppler back-scattering). It is likely there will be gaps in the wavelength range that these instruments can measure, so we anticipate a need to develop and install a new microwave imaging system. This will be designed using knowledge gained from the early phase of the programme, and deployed for further experiments towards the end.

Understanding of electromagnetic turbulence is less developed and new theoretical models will be required. Building on the knowledge gained from the electrostatic turbulence, we will seek to again understand the multi-scale interactions and feedbacks, including flows. However, now the situation is more complicated as electromagnetic turbulence can drive large scale currents, modifying the magnetic field which confines the plasma, and coupling into large scale electromagnetic modes.

A key motivation is to optimise tokamak plasmas for fusion performance, and this requires us to understand the impact of fast particles. These can drive turbulence directly through the instabilities they excite, or influence the turbulence driven by the thermal particles. Our simulations will assess the impact of the fast particles created by the neutral beam heating systems on MAST-U, and also the impact of energetic alpha particles from fusion reactions on future devices like ITER, as well as experiments planned on JET with the deuterium-tritium mix fusion fuel.

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Organisation Website: http://www.york.ac.uk