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PhD in Engineering and Applied Science
Candidate: Shayesteh Naghinajad
Abstract: A typical approach to 3D image reconstruction is computed tomography, which reconstructs the sought image based on a set of slice projections. Tomography relies on the Fourier slice theorem in 2D. In this thesis, an imaging technique based on the formulation of the Fourier slice theorem in 3D is proposed. In this way, a set of projections onto planes, defined as 2D Radon transform, is related to the 3D Fourier transform. After a suitable transformation of coordinates, by calculating the 3D inverse Fourier transform of projections, the 3D image of the scanned object is reconstructed [1]. The formulation developed is applied to the reconstruction of distribution of light emission of magnetically confined plasma in 3D, employing data provided by ENEA Frascati. This data includes visible light emission by both Hydrogen and Helium plasma, recorded within the framework of the PROTOSPHERA experiment. The analysis carried out enabled observation of the physics of the formation of the plasma torus. It was shown how the plasma torus grows in 5-8 ms from a kinked filament, due to the destabilization of the plasma centerpost (Figure 1). In addition, it was observed that the plasma torus rotates around the centerpost axis (Figure 2), in analogy with phenomena observed in Pulsar morphology [2].
[1] S. Naghinajad, A. Pau. "3D ultrasonic tomography for image reconstruction: an application to the plasma dynamics of PROTO-SPHERA." ECCOMAS YIC, Porto, June 19-21 2023.
[2] F. Alladio, P. Micozzi, L. Boncagni, P. Buratti, Y. Damizia, F. Filippi, G. Galatola Teka, F. Giammanco, E. Giovannozzi, M. Iafrati, A. Lampasi, S. Macera, P. Marsili, A. Pau, S. Naghinajad. "PROTO-SPHERA: a magnetic confinement experiment which emulates the jet + torus astrophysical plasmas." submitted
[3] F. Alladio P. Micozzi, L. Boncagni, P. Buratti, Y. Damizia, F. Filippi, G. Galatola Teka, F. Giammanco, E. Giovannozzi, M. Iafrati, A. Lampasi, S. Macera, P. Marsili, A. Pau, S. Naghinajad. "PROTO-SPHERA: a magnetic confinement experiment which emulates the jet + torus astrophysical plasmas." European Conference on Plasma Diagnostics, Crete, Greece, April 23-27 2023
Figure 1: Axonometries of the tomographic reconstruction of light emission density during the torus formation
Figure 1: Axonometries of the tomographic reconstruction of light emission density during the torus formation
Figure 2: Axonometries of the tomographic reconstruction of light emission density showing rotation of the torus
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