Nonlinear microwave interactions and induced turbulence in magnetised laboratory plasma

Laboratory plasmas are being increasingly exploited in contemporary high-value, high-technology industries. At the same time, the harnessing of fusion energy to provide the world's energy needs in an environmentally safe, carbon-free way may be based on magnetically confined plasmas. One of the major methods used to heat fusion plasmas is to inject large amplitude microwaves and to excite various resonances in the plasma via mode conversion or via nonlinear processes. For example, the coupling of electromagnetic waves to kinetic modes such as electron Bernstein waves is one of the heating mechanisms and diagnostics proposed for the MAST Upgrade spherical Tokamak. To understand the induced turbulence and resulting currents and transport is a challenging task. An open question is the interplay between different length- and time-scales in magnetically confined plasma, and how small-scale turbulence influences large-scale currents and transport in the plasma via wave-particle interactions.

The project aims to undertake a theoretical and numerical investigation of nonlinear interaction between large amplitude microwaves and magnetised plasma and beams, as well as diagnostics of turbulent processes and transport in the plasma, supported by numerical simulations and theoretical modelling. The Atoms, Beams and Plasmas group has extensive experience in laboratory experiments using a linear plasma device, to study the interaction between microwaves and plasmas, and kinetic instabilities leading to radiation escaping the plasma. The ABP group has also pioneered microwave generation using relativistic electrons beams, with waves ranging from centimetres to sub-millimetres. These microwaves will be used both as a diagnostic and for studying wave-plasma interactions, including various scattering instabilities. The project will be carried out in close collaboration with the Culham Centre for Fusion Energy (CCFE), where diagnostics from experiments will be carried out and interpreted.