## Plasma Physics

For a fusion reactor to operate efficiently the plasma must operate at a sufficiently high pressure and energy confinement time, as well as preserving purity of the fuel. However, the pressure and confinement time of tokamak reactors are limited by instabilities in the fusion plasma. These instabilities need to be fully modelled and investigated to ensure that the new generation of fusion reactors currently planned and under construction can actually sustain a fusion reaction for the time required to produce significant amounts of energy, and there demonstrate the potential for fusion power.

One consequence of the instabilities in fusion plasmas is the occurrence of turbulent fluctuations, associated with significant transport of heat, momentum, and particles across the confining magnetic field. This effect severely limits the energy confinement time for a given machine size and therefore the performance and economy of a tokamak device.

Accurate calculations of turbulent transport are therefore vital for the design and operation of usable fusion power plans, and such calculations can only be achieved through detailed modelling, as it fills the space between experimental observations, which are expensive and difficult to acquire, and analytic theory, which cannot fully handle the nonlinearity of the problem. This modelling is already undertaken using computational simulation, however, to create the ultimate goal of computational fusion research, a numerical tokamak, we need access to much greater amounts of computational resources, ultimately requiring Exascale computing.