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As we enter the era of burning plasmas in next step devices such as ITER, the confinement of fusion born a-particles for sufficient duration that they impart their energy to the bulk fuel ions in order to maintain the thermonuclear burn is an important challenge in magnetically confined fusion. Fast ion driven plasma instabilities can cause significant redistribution and loss of the suprathermal energetic particle (EP) population, degrading performance. With dimensionless parameters such as the ratio of fast ion to thermal ion beta (Bfi/Bth ~50%) and the relative fast ion velocity to the Alfvén velocity (vfi/vA ~2) similar to those anticipated in ITER, the Mega Ampere Spherical Tokamak (MAST) provides the ideal place to study such instabilities. During periods of Neutral Beam Injection (NBI) heating, 'fishbone' instabilities are observed that coincide with a reduction to the fusion rate measured by drops in the neutron emission. Via experimental observations, fishbones are identified to be low frequency internal kink modes that burst in amplitude and chirp downwards in frequency and are synonymous with high power tokamak discharges on a wide range of devices around the world. This thesis provides a detailed analysis of what occurs during a single fishbone event. Experiments have been performed on MAST that have been interpreted using fast ion plasma physics codes. Modelling of the instability shows a resulting flux of fast ions away from the core, providing evidence at a fundamental level that they drive sufficient levels of anomalous fast ion transport to explain experimental observations. The diffusivity is shown to scale with mode amplitude, and the effect of altering other fishbone parameters within the scope of the experimental observations have been explained by identifying the extent of the fast ion population that is resonant with the mode. Resonant surfaces that sweep through phase space during the chirp are presented that coincide with populous domains of the EP distribution function; it is the gradients in this distribution function that define the drive and or damping of the instability. Via the use of synthetic diagnostics, changes to the radial profiles of neutron emissivity caused by a fishbone are shown to match those measured experimentally.

Experiments have been conducted to identify the fouling mechanism during the crossflow filtration of a model yeast fermentation broth of Vinyl Acetate particles suspended in a Bovine Serum Albumin (BSA) solution. These have been conducted with filter modules, to obtain quantitative data for the rate and the extent of flux decline due to membrane fouling, and with filter coupons, to obtain quantitative data for the build up of the fouling layer with each individual system and the mixed system. The data from the individual systems have been analysed and then used to determine their fouling mechanisms; this information has been used to predict the fouling mechanism for the mixed system. Finally, this prediction has been compared to the actual fouling mechanism determined by analysis of the mixed system data. For the model particulate suspension, the fouling was due to the build up of a cake layer, as with dead end filtration; however, fouling was limited by membrane scouring. For the model macromolecular solution, a four part fouling mechanism was identified: initially aggregates formed within the pores; the concentration at the membrane surface increased until protein came out of solution as strands; the strands disappeared causing increased aggregation in the pores; finally, a mesh formed on the membrane surface. For the mixed system, fouling was due to the formation of a particle cake on the membrane surface with protein aggregates forming in the pores. The fouling kinetics could be predicted by considering the results from the individual systems; however, the fouling mechanism could not be predicted without using visualisation experiments due to the interactions between the particles and the macromolecules.