Accurate and efficient plasma models are essential to understand and control experimental devices. Existing magnetohydrodynamic or kinetic models are nonlinear and computationally intensive and can be difficult to interpret, while often only approximating the true dynamics. In this work, data-driven techniques recently developed in the field of fluid dynamics are leveraged to develop interpretable reduced-order models of plasmas that strike a balance between accuracy and efficiency. In particular, dynamic mode decomposition (DMD) is used to extract spatio-temporal magnetic coherent structures from the experimental and simulation datasets of the helicity injected torus with steady inductive (HIT-SI) experiment. Three-dimensional magnetic surface probes from the HIT-SI experiment are analyzed, along with companion simulations with synthetic internal magnetic probes. A number of leading variants of the DMD algorithm are compared, including the sparsity-promoting and optimized DMD. Optimized DMD results in the highest overall prediction accuracy, while sparsity-promoting DMD yields physically interpretable models that avoid overfitting. These DMD algorithms uncover several coherent magnetic modes that provide new physical insights into the inner plasma structure. These modes were subsequently used to discover a previously unobserved three-dimensional structure in the simulation, rotating at the second injector harmonic. Finally, using data from probes at experimentally accessible locations, DMD identifies a resistive kink mode, a ubiquitous instability seen in magnetized plasmas.
Kaptanoglu, A. A., et al. "Characterizing magnetized plasmas with dynamic mode decomposition." Physics of Plasmas, vol. 27, no. 3, Mar. 2020. https://doi.org/10.1063/1.5138932
Kaptanoglu, A. A., Morgan, K. D., Hansen, C. J., & Brunton, S. L. (2020). Characterizing magnetized plasmas with dynamic mode decomposition. Physics of Plasmas, 27(3). https://doi.org/10.1063/1.5138932
Kaptanoglu, A. A., Morgan, K. D., Hansen, C. J., et al., "Characterizing magnetized plasmas with dynamic mode decomposition," Physics of Plasmas 27, no. 3 (2020), https://doi.org/10.1063/1.5138932
@article{osti_1608227,
author = {Kaptanoglu, A. A. and Morgan, K. D. and Hansen, C. J. and Brunton, S. L.},
title = {Characterizing magnetized plasmas with dynamic mode decomposition},
annote = {Accurate and efficient plasma models are essential to understand and control experimental devices. Existing magnetohydrodynamic or kinetic models are nonlinear and computationally intensive and can be difficult to interpret, while often only approximating the true dynamics. In this work, data-driven techniques recently developed in the field of fluid dynamics are leveraged to develop interpretable reduced-order models of plasmas that strike a balance between accuracy and efficiency. In particular, dynamic mode decomposition (DMD) is used to extract spatio-temporal magnetic coherent structures from the experimental and simulation datasets of the helicity injected torus with steady inductive (HIT-SI) experiment. Three-dimensional magnetic surface probes from the HIT-SI experiment are analyzed, along with companion simulations with synthetic internal magnetic probes. A number of leading variants of the DMD algorithm are compared, including the sparsity-promoting and optimized DMD. Optimized DMD results in the highest overall prediction accuracy, while sparsity-promoting DMD yields physically interpretable models that avoid overfitting. These DMD algorithms uncover several coherent magnetic modes that provide new physical insights into the inner plasma structure. These modes were subsequently used to discover a previously unobserved three-dimensional structure in the simulation, rotating at the second injector harmonic. Finally, using data from probes at experimentally accessible locations, DMD identifies a resistive kink mode, a ubiquitous instability seen in magnetized plasmas.},
doi = {10.1063/1.5138932},
url = {https://www.osti.gov/biblio/1608227},
journal = {Physics of Plasmas},
issn = {ISSN 1070-664X},
number = {3},
volume = {27},
place = {United States},
publisher = {American Institute of Physics (AIP)},
year = {2020},
month = {03}}
PLASMA 2007: International Conference on Research and Applications of Plasmas; 4th German-Polish Conference on Plasma Diagnostics for Fusion and Applications; 6th French-Polish Seminar on Thermal Plasma in Space and Laboratory, AIP Conference Proceedingshttps://doi.org/10.1063/1.2909159