Regularization of soft-X-ray imaging in the DIII-D tokamak

Wingen, A.; Shafer, M. W.; Unterberg, E. A.; Hill, J. C.; Hillis, D. L.

doi:10.1016/j.jcp.2015.02.040

Title: Regularization of soft-X-ray imaging in the DIII-D tokamak

Journal Article · Mon Mar 02 00:00:00 EST 2015 · Journal of Computational Physics

DOI:https://doi.org/10.1016/j.jcp.2015.02.040· OSTI ID:1185689

Wingen, A. ^[1]; Shafer, M. W. ^[1]; Unterberg, E. A. ^[1]; Hill, J. C. ^[1]; Hillis, D. L. ^[1]

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

We developed an image inversion scheme for the soft X-ray imaging system (SXRIS) diagnostic at the DIII-D tokamak in order to obtain the local soft X-ray emission at a poloidal cross-section from the spatially line-integrated image taken by the SXRIS camera. The scheme uses the Tikhonov regularization method since the inversion problem is generally ill-posed. The regularization technique uses the generalized singular value decomposition to determine a solution that depends on a free regularization parameter. The latter has to be chosen carefully, and the so called {\it L-curve} method to find the optimum regularization parameter is outlined. A representative test image is used to study the properties of the inversion scheme with respect to inversion accuracy, amount/strength of regularization, image noise and image resolution. Moreover, the optimum inversion parameters are identified, while the L-curve method successfully computes the optimum regularization parameter. Noise is found to be the most limiting issue, but sufficient regularization is still possible at noise to signal ratios up to 10%-15%. Finally, the inversion scheme is applied to measured SXRIS data and the line-integrated SXRIS image is successfully inverted.

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Research Organization:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

Grant/Contract Number:: AC05-00OR22725

OSTI ID:: 1185689

Alternate ID(s):: OSTI ID: 1252799

Journal Information:: Journal of Computational Physics, Vol. 289, Issue C; ISSN 0021-9991

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 14 works

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References (17)

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First results of the 2D gas electron multiplier in the dominant electron heating scenario on EAST Li, Erzhong; Qu, H.; Hu, L. Nuclear Fusion, Vol. 59, Issue 10 https://doi.org/10.1088/1741-4326/ab36bb	journal	August 2019
Diagnosing Forward Operator Error Using Optimal Transport Puthawala, Michael A.; Hauck, Cory D.; Osher, Stanley J. Journal of Scientific Computing, Vol. 80, Issue 3 https://doi.org/10.1007/s10915-019-00989-0	journal	July 2019
Tomography diagnostic of plasma radiated power on the spherical tokamak Globus-M Sladkomedova, A. D.; Alekseev, A. G.; Bakharev, N. N. Review of Scientific Instruments, Vol. 89, Issue 8 https://doi.org/10.1063/1.5039801	journal	August 2018
Reconstruction of radiation profiles near the plasma boundary using an infrared imaging video bolometer in KSTAR Jang, Juhyeok; Peterson, Byron J.; Oh, Seungtae Review of Scientific Instruments, Vol. 89, Issue 10 https://doi.org/10.1063/1.5038904	journal	October 2018
Application of the Tikhonov tomography method for the gas electron multiplier (GEM) system on experimental advanced superconducting tokamak Cordella, F.; Claps, G.; Pacella, D. Review of Scientific Instruments, Vol. 90, Issue 9 https://doi.org/10.1063/1.5111481	journal	September 2019
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