title: Optimized tomography methods for plasma emissivity reconstruction at the ASDEX Upgrade tokamak.
abstract: The soft X-ray (SXR) emission provides valuable insight into processes happening inside of high-temperature plasmas. A standard method for deriving the local emissivity profiles of the plasma from the line-of-sight integrals measured by pinhole cameras is the tomographic inversion. Such an inversion is challenging due to its ill-conditioned nature and because the reconstructed profiles depend not only on the quality of the measurements but also on the inversion algorithm used. This paper provides a detailed description of several tomography algorithms, which solve the inversion problem of Tikhonov regularization with linear computational complexity in the number of basis functions. The feasibility of combining these methods with the minimum Fisher information regularization is demonstrated, and various statistical methods for the optimal choice of the regularization parameter are investigated with emphasis on their reliability and robustness. Finally, the accuracy and the capability of the methods are demonstrated by reconstructions of experimental SXR profiles, featuring poloidal asymmetric impurity distributions as measured at the ASDEX Upgrade tokamak.
authors.affiliation: Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Odstrčil
authors.affiliation: Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Pütterich
authors.affiliation: Optoelectronic Research Center, University of Southampton, Southampton, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Odstrčil
authors.affiliation: Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Gude
authors.affiliation: Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Igochine
authors.affiliation: Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Stroth
authors.affiliation: Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany.