MHD Equilibrium Reconstruction Using the Visible Light Tomographic Method with Laplacian Eigenfunction

Abstract

A tomographic method using tangential visible light is proposed for MHD equilibrium reconstruction via two processes. The first process is a tomographic method to estimate the last-closed-flux-surface (LCFS) in twodimensional poloidal cross-section using a single tangential camera image. Applying the Laplacian eigenfunction series expansion and L 1 regularization, we can reconstruct the LCFS from relatively sparse and noisy observations. The second method is a free-boundary tokamak equilibrium calculation using the TASK/EQU code, in which we use the estimated plasma surface information as the constraints for the equilibrium calculation. As a result, we develop a new method for identifying equilibrium states using visible light information.

A Bayesian formulation for perturbed current tomography in tokamaks

“…To describe the current perturbations in the plasma we need to choose a description of the internal state of the plasma. In older work, a continuum decomposition into a set of orthonormal eigenfunctions was common [14,15]. In more modern work the preference has been to adopt a pixel model of the plasma as it is more natural for line integrated measurements and has been shown to produce empirically superior results [4].…”