Siobhan Smith

University Of York

I am a PhD student based at Culham Centre for Fusion Energy (CCFE), supervised by Professor Howard Wilson York and Dr Stanislas Pamela at CCFE.

My project title is ‚ÄúSimulations of edge localised modes (ELMs) in MAST-U Super-X plasmas.”

Funding is provided by an EPSRC ICASE award and the EPSRC Fusion CDT.

Edge localised modes (ELMs) are magneto-hydrodynamic (MHD) instabilities that drive filamentary plasma eruptions in high confinement tokamak discharges. In future fusion reactors ELM heat fluxes will be reduced to ensure durability of divertor materials; peak heat fluxes from uncontrolled type-I ELMs are predicted to significantly damage the ITER Tungsten divertor plates so gaining an improved understanding of ELMs is important. The MAST-U tokamak will test a new divertor configuration, the Super-X, as a possible solution to lower the target heat fluxes. Additional PF coils in the divertor region will control the strike point radius length (R), at larger R the contact area of the plasma increases, which decreases the target heat flux. Flux expansion in the chamber is also possible, increasing the neutral interaction volume. The closed divertor design of the Super-X allows for retention of neutrals, this is important for attaining detachment whilst keeping impurities low in the core plasma. Plasma detachment can occur as the ion temperature is reduced due to the ion-neutral interaction. The characteristics of ELM divertor heat fluxes in the Super-X are unknown, particularly it is not known if the ELMs will burn through the detachment front. This project will investigate this making predictions for MAST-U before H-mode operation in 2019. The 3D nonlinear MHD code JOREK is used for the simulations; benchmarking of JOREK with another MHD code BOUT++ is also being done.