Reconstruction of soft x-ray emission in MAST Upgrade.

Abstract

Understanding the confinement of fast ions is crucial for plasma heating and non-inductive current drive, i.e., for the operation of a fusion reactor. Interactions between fast ions and magnetohydrodynamic instabilities can reduce the performance of fusion reactions. Measuring the spatial shape and amplitude is crucial for constraining numerical modeling of the interaction between fast ions and these instabilities. Soft x rays can be used to study these magnetic instabilities. In particular, SXR tomography is used to reconstruct the two-dimensional profile of the SXR emissivity requiring only line integrated measurements, thus providing the spatial structure of the instabilities. This work presents SXR tomography reconstruction performed on synthetic SXR emissions from the Mega Ampere Spherical Tokamak Upgrade device. The synthetic SXR emissions are derived from time dependent tokamak transport data analysis code (TRANSP/NUBEAM) simulations. Different tomographic reconstruction models are compared, and the effect of two additional fans of intersecting lines of sight on the reconstructions' performances is investigated. The additional intersecting lines of sight greatly improve the accuracy of the reconstructions.