A new combined Doppler backscattering and cross-polarization scattering system for measurement of density and magnetic turbulence in the MAST-U spherical tokamak*

We report on the design and laboratory testing of a new combined Doppler backscattering (DBS) and cross-polarization scattering (CPS) diagnostic that is currently being installed on the MAST-U spherical tokamak at the Culham Centre for Fusion Energy in Oxfordshire, UK. This system will allow for simultaneous measurement of local density turbulence, flows, and magnetic turbulence. The systems are based on an eight channel millimeter wave source, where DBS and CPS share a probing beam. A DBS analysis module in OMFIT will also be presented, which will be used to analyze MAST DBS data from 2013 as well as to be the primary tool with which to analyze new MAST-U DBS data as it becomes available. Initial scoping and design of experiments to investigate the relationship between collisionality, confinement, and turbulent transport will be reported.