First MAST-U Equilibrium Reconstructions using the EFIT++ Code
The MAST-U spherical tokamak has extensive capabilities to produce and explore strongly shaped plasmas and alternative divertor configurations, especially the Super-X. Robust and accurate reconstructions of plasma equilibria are the foundation of many physics analyses, as well as being important intershot for informing operation of the tokamak. MAST-U is equipped with a range of magnetic sensors including 398 b-field sensors and 102 flux loops. In this work the GradShafranov equation for plasma equilibrium is solved using the EFIT++ code[1], which has been updated to provide routine magnetics only reconstructions during the first physics campaign. The results of the analysis show a good agreement with the magnetics data, and the quality of equilibrium reconstructions is further assessed by comparing with diagnostics not used as constraints. For example, in the divertor region there is good agreement between EFIT++ and strike point locations measured with Infra-Red thermography and Langmuir probes, and the divertor leg position measured with Multi-Wavelength Imaging. The next steps for analysis of MAST-U equilibria are discussed. This includes the first results and impact of adding additional constraints to the EFIT++ reconstructions of the electron pressure profile from Thomson Scattering, ion temperature from Charge Exchange and the magnetic pitch angle from the Motional Stark Effect system to the EFIT++ reconstructions.