4D and 5D phase-space tomography using slowing-down physics regularization
Bo Simmendefeldt Schmidt, M. Salewski, D. Moseev, M. Baquero-Ruiz, Per Christian Hansen, J. Eriksson, O. Ford, G. Gorini, H. Järleblad, Ye. O. Kazakov, D. Kulla, S. Lazerson, Jacob Emil Mencke, D. Mykytchuk, M. Nocente, P. Zs. Pölöskei, M. Rud, A. Snicker, L. Stagner, S. Äkäslompolo
Abstract
Abstract We compute reconstructions of 4D and 5D fast-ion phase-space distribution functions in fusion plasmas from synthetic projections of these functions. The fast-ion phase-space distribution functions originating from neutral beam injection (NBI) at TCV and Wendelstein 7-X (W7-X) at full, half, and one-third injection energies can be distinguished and particle densities of each component inferred based on 20 synthetic spectra of projected velocities at TCV and 680 at W7-X. Further, we demonstrate that an expansion into a basis of slowing-down distribution functions is equivalent to regularization using slowing-down physics as prior information. Using this technique in a Tikhonov formulation, we infer the particle density fractions for each NBI energy for each NBI beam from synthetic measurements, resulting in six unknowns at TCV and 24 unknowns at W7-X. Additionally, we show that installing 40 LOS in each of 17 ports at W7-X, providing full beam coverage and almost full angle coverage, produces the highest quality reconstructions.