Public Abstract

DE-SC0023061: Modeling Plasma Response to Non-Axisymmetric Magnetic Field Perturbations in Tokamak Boundaries

Award Status: Active

Institution: Auburn University, Auburn, AL
UEI: DMQNDJDHTDG4
DUNS: 066470972

Most Recent Award Date: 08/28/2024
Number of Support Periods: 3
PM: Halfmoon, Michael

Current Budget Period: 06/01/2024 - 05/31/2025
Current Project Period: 06/01/2024 - 05/31/2027
PI: Kostadinova, Evdokiya

Supplement Budget Period: N/A

Public Abstract

Modeling Plasma Response to Non-Axisymmetric Magnetic Field Perturbations in Tokamak Boundaries Dr. Dmitri M. Orlov, UC San Diego (Principal Investigator) Dr. Evdokiya G. Kostadinova, Auburn University (Co-Investigator) Dr. Eric C. Howell, Tech-X Corp. (Co-Investigator) This project aims to investigate the plasma response to non-axisymmetric perturbation fields and the resulting transport of heat and particle fluxes in tokamak devices. Understanding plasma response to non-axisymmetric fields is crucial to maintaining good plasma confinement while preventing dangerous edge instabilities that can lead to disruptions and/or unacceptable heat and particle loads on the tokamak divertors. These studies are directly applicable to controlling H-mode edge plasma parameters and Edge Localized Mode (ELM) stability using small non-axisymmetric magnetic field perturbations. In this project, we plan to improve on previous modeling efforts by exploring four major objectives: 1) conduct realistic, multi-mode simulations of the applied fields and the plasma response, 2) develop a multi-ion MHD model of main-ion and impurity-ion effects on plasma response, 3) investigate transport across magnetic islands and regions of stochastic magnetic fields, and 4) develop single-particle and spectral models of anomalous diffusion of energetic particles. All models developed in the research will be validated against current experimental data and used to obtain predictions for future fusion devices. The multi-mode toroidal spectrum for the applied fields is generated using our trip3d suite of engineering quality 3D magnetic field perturbation descriptions for all major tokamaks currently performing 3D magnetic field and ELM suppression research. This allows us to compare the (no plasma) vacuum field solution to results from linear and nonlinear plasma response simulations to assess the role of the magnetic field topology in different configurations. The simulation predictions are further validated against data from heat and particle flux measurements, ECE-Imaging, and GRI diagnostics in DIII-D, KSTAR, and NSTX/NSTX-U discharges to identify limitations in different plasma response models. Nonlinear nimrod simulations will be used to model realistic applied 3D perturbations, including the full toroidal mode spectrum of the applied field (in place of a simplified single-helicity field) and all known error-field descriptions and error-field correction fields. The capabilities of such simulations will be further expanded by including multi-ion models to account for main-ion and impurity-ion effects on the plasma response. A Fractional Laplacian Spectral (fls) code will be used to understand the anomalous transport of energetic particles in fusion plasmas. The principal impact of this research is the ability to use physics-based criteria to design magnetic perturbation coils needed for ELM suppression while maintaining excellent plasma confinement and H-mode pedestal control in burning plasma devices, such as ITER and a fusion pilot plant (FPP). Additional benefits from this research lie in developing and validating plasma response codes, field-line tracing codes, and models for energetic particle transport. The project also includes training students and early-career scientists.

Modeling Plasma Response to Non-Axisymmetric Magnetic Field Perturbations in Tokamak Boundaries

Dr. Dmitri M. Orlov, UC San Diego (Principal Investigator)
Dr. Evdokiya G. Kostadinova, Auburn University (Co-Investigator)
Dr. Eric C. Howell, Tech-X Corp. (Co-Investigator)

This project aims to investigate the plasma response to non-axisymmetric perturbation fields and the resulting transport of heat and particle fluxes in tokamak devices. Understanding plasma response to non-axisymmetric fields is crucial to maintaining good plasma confinement while preventing dangerous edge instabilities that can lead to disruptions and/or unacceptable heat and particle loads on the tokamak divertors. These studies are directly applicable to controlling H-mode edge plasma parameters and Edge Localized Mode (ELM) stability using small non-axisymmetric magnetic field perturbations. In this project, we plan to improve on previous modeling efforts by exploring four major objectives: 1) conduct realistic, multi-mode simulations of the applied fields and the plasma response, 2) develop a multi-ion MHD model of main-ion and impurity-ion effects on plasma response, 3) investigate transport across magnetic islands and regions of stochastic magnetic fields, and 4) develop single-particle and spectral models of anomalous diffusion of energetic particles.

All models developed in the research will be validated against current experimental data and used to obtain predictions for future fusion devices. The multi-mode toroidal spectrum for the applied fields is generated using our trip3d suite of engineering quality 3D magnetic field perturbation descriptions for all major tokamaks currently performing 3D magnetic field and ELM suppression research. This allows us to compare the (no plasma) vacuum field solution to results from linear and nonlinear plasma response simulations to assess the role of the magnetic field topology in different configurations. The simulation predictions are further validated against data from heat and particle flux measurements, ECE-Imaging, and GRI diagnostics in DIII-D, KSTAR, and NSTX/NSTX-U discharges to identify limitations in different plasma response models. Nonlinear nimrod simulations will be used to model realistic applied 3D perturbations, including the full toroidal mode spectrum of the applied field (in place of a simplified single-helicity field) and all known error-field descriptions and error-field correction fields. The capabilities of such simulations will be further expanded by including multi-ion models to account for main-ion and impurity-ion effects on the plasma response. A Fractional Laplacian Spectral (fls) code will be used to understand the anomalous transport of energetic particles in fusion plasmas.

The principal impact of this research is the ability to use physics-based criteria to design magnetic perturbation coils needed for ELM suppression while maintaining excellent plasma confinement and H-mode pedestal control in burning plasma devices, such as ITER and a fusion pilot plant (FPP). Additional benefits from this research lie in developing and validating plasma response codes, field-line tracing codes, and models for energetic particle transport. The project also includes training students and early-career scientists.