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Optimized tomography methods for plasma emissivity reconstruction at the ASDEX Upgrade tokamak

Optimized tomography methods for plasma emissivity reconstruction at the ASDEX Upgrade tokamak
Optimized tomography methods for plasma emissivity reconstruction at the ASDEX Upgrade tokamak
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.
0034-6748
1-17
Odstrčil, T.
69f6a622-d274-4c2b-a255-a41baeb40d07
Putterich, T.
e74afaec-5392-4d84-913a-2140da49aba2
Odstrčil, M.
b297d3ec-ed42-4709-9f90-7af79d0644c7
Gude, A.
e38c1dc9-529e-4c7a-a39c-63190d979e95
Igochine, V.
30107c59-38d5-4378-95c6-07e1f1d7f4ba
Stroth, U.
280fd36f-bf74-4d36-a69c-7993c1669893
Odstrčil, T.
69f6a622-d274-4c2b-a255-a41baeb40d07
Putterich, T.
e74afaec-5392-4d84-913a-2140da49aba2
Odstrčil, M.
b297d3ec-ed42-4709-9f90-7af79d0644c7
Gude, A.
e38c1dc9-529e-4c7a-a39c-63190d979e95
Igochine, V.
30107c59-38d5-4378-95c6-07e1f1d7f4ba
Stroth, U.
280fd36f-bf74-4d36-a69c-7993c1669893

Odstrčil, T., Putterich, T., Odstrčil, M., Gude, A., Igochine, V. and Stroth, U. (2016) Optimized tomography methods for plasma emissivity reconstruction at the ASDEX Upgrade tokamak. Review of Scientific Instruments, 87 (123505), 1-17. (doi:10.1063/1.4971367).

Record type: Article

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.

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More information

Accepted/In Press date: 18 November 2016
e-pub ahead of print date: 15 December 2016
Additional Information: ASDEX Upgrade Team
Organisations: Optoelectronics Research Centre

Identifiers

Local EPrints ID: 405703
URI: http://eprints.soton.ac.uk/id/eprint/405703
ISSN: 0034-6748
PURE UUID: f292a1ec-51f0-45fb-8905-170d5d649143

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Date deposited: 10 Feb 2017 16:56
Last modified: 15 Mar 2024 04:35

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Contributors

Author: T. Odstrčil
Author: T. Putterich
Author: M. Odstrčil
Author: A. Gude
Author: V. Igochine
Author: U. Stroth

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