Development of tungsten diamond composites for nuclear fusion applications

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This project will focus on the analysis and development of tungsten diamond composites for fusion applicationsTechnical ContextITER divertor plasma facing components (PFCs) are engineered to withstand 10 MW m-2 of steady-state surface heating. For comparison, the value is approximately 1 MW m-2 for a spacecraft heat shield during re-entry, 10-80 MW m-2 for an arc welder, and 50-150 MW m-2 for a cryogenically cooled rocket engine nozzle. For the last 25 years, progress in fusion has largely relied on the use of fine grain graphite and carbon fiber composites in the high heat-flux regions, where the carbon technology was adapted from the fission and aerospace industries. More recently, the carbon surface has been enhanced with high performance tungsten thin films (10-200 microns) in order to increase erosion resistance. Over a similar timeframe, diamond from CVD has become readily available. A UKAEA led research programme from 2007-2010 included: (i) a 5 mm thick boron-doped plate prototype exposed to high heat-flux electron beam testing, and (ii) thin films exposed to plasma in several fusion devices.CVD diamond is of interest because diamond has many relevant properties that are often best-in-class compared to all other materials: -isotropic thermal conductivity 5 times higher than copper at room temperature,-very low thermal expansion,-the above combine to give diamond unparalleled thermal shock resistance,-sublimates instead of melting,-low chemical reactivity with hydrogen in a gas environment,-forms strong carbide chemical bonds with many metals, including tungsten,-high tensile strength, and-good resistance to neutron radiation damage.Objective The goal is to work on developing and analysing tungsten diamond composites. This will contribute to the development of a multi layered composite tungsten diamond material in order to:a) reduce chemical reactivity, b) increase the erosion resistance to physical sputtering,c) marginal improved ductility at elevated temperatures, andd) quasi-self-repairing, since the diamond erodes until a new tungsten layer if the surface film is lost.This project will work on developing tungsten diamond composites and potentially a multi-layer composite and test them under fusion relevant conditions. Experimental analysis techniques will be used to assess the quality of the novel material.