Tom Farley

University Of Liverpool

I am currently studying for a PhD under the supervision of Dr Fulvio Militello (CCFE) and Prof. James Bradley (Liverpool). I am studying plasma filaments – coherent filamentary structures that play a dominant role in turbulent cross-field particle transport in the tokamak scrape off layer (SOL). These intermittent structures propagate outwards far from the last closed flux surface (LCFS), widening the SOL and increasing particle transport towards the walls. In some cases filaments have been shown to be responsible for over 50% of the particles in the SOL. The properties of filaments, their dependence on plasma parameters and their origins and evolution must be understood in order to optimise SOL dynamics in order to minimise erosion of plasma facing surfaces and maximise the lifetime of a fusion reactor.

The compact, open design of MAST provides excellent capabilities to directly image and analyse these filaments using fast visible cameras. Individual filaments can be identified and tracked using the property that filaments are strongly field aligned. The paths of magnetic field lines generated from EFIT equilibria are projected onto camera images and regions where field lines are well aligned with high intensity structures in the images are labelled as filaments. This technique enables filament positions, dimensions, velocities and shapes to be measured in order to build up a better understanding of filament evolution and propagation.