Electron Bernstein wave current drive on MAST-U (plasma strand project)

Supervisor: Roddy Vann (University of York)

The MAST-U tokamak is embarking on an ambitious world-first project to inject several megawatts in the microwave frequency range (typically 20-30 GHz) in order to heat the plasma and drive current using the resonant interaction between plasma electrons and so-called electron Bernstein waves. This technique has two key advantages over conventional electron cyclotron current drive: it can access very dense plasmas (typical in spherical tokamaks) and it has a much higher current drive efficiency.

The problem is that this technique is technically challenging. The electron Bernstein wave does not propagate in vacuum, so has to be stimulated in the plasma via a mode conversion process from an incident electromagnetic wave. This mode conversion process is not fully understood. Moreover, the electron Bernstein wave is rather exotic – it typically has a negative refractive index and is very short wavelength, making its simulation challenging.

The MAST-U microwave heating & current drive project requires effort spanning high performance simulations, plasma physics and high power engineering. Applications are encouraged from anywhere on this spectrum. Example projects might include first principles modelling of the mode conversion efficiency in the presence of nonlinear instabilities, the implementation of a real-time control system integrating with complementary diagnostics or the design and construction of an array of microwave launchers. The details of the project will be agreed to fit the highest-priority needs of the project and the skills of the applicant.

This studentship will be based at the University of York at least for the first year; thereafter it is likely that some extended periods would be spent at the Culham Centre for Fusion Energy in Oxfordshire.

This project provides the opportunity to develop a wide range of transferable skills, including programming, tokamak operation, electronic & microwave engineering and data analysis.

This project is offered by University of York. For further information please contact Roddy Vann (roddy.vann@york.ac.uk).

Figure above: An image from the SAMI diagnostic on MAST showing the O-mode to X-mode conversion windows as a function of viewing angles, through which we should have to aim in order to successfully inject a microwave heating beam into the overdense plasma on MAST-U.