Computational study of runaway electrons in MST tokamak discharges with applied resonant magnetic perturbation

B. S. Cornille; M. T. Beidler; S. Munaretto; B. E. Chapman; D. Del-Castillo-Negrete; N. C. Hurst; J. S. Sarff; C. R. Sovinec

doi:10.1063/5.0087314

Computational study of runaway electrons in MST tokamak discharges with applied resonant magnetic perturbation

B. S. Cornille, M. T. Beidler, S. Munaretto, B. E. Chapman, D. Del-Castillo-Negrete, N. C. Hurst, J. S. Sarff, C. R. Sovinec

Plasma Theory and Modeling

Research output: Contribution to journal › Article › peer-review

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Abstract

A numerical study of magnetohydrodynamics (MHD) and tracer-particle evolution investigates the effects of resonant magnetic perturbations (RMPs) on the confinement of runaway electrons (REs) in tokamak discharges conducted in the Madison Symmetric Torus. In computational results of applying RMPs having a broad toroidal spectrum but a single poloidal harmonic, m = 1 RMP does not suppress REs, whereas m = 3 RMP achieves significant deconfinement but not the complete suppression obtained in the experiment [Munaretto et al., Nuclear Fusion 60, 046024 (2020)]. MHD simulations with the NIMROD code produce sawtooth oscillations, and the associated magnetic reconnection can affect the trajectory of REs starting in the core region. Simulations with m = 3 RMP produce chaotic magnetic topology over the outer region, but the m = 1 RMP produces negligible changes in field topology, relative to applying no RMP. Using snapshots of the MHD simulation fields, full-orbit relativistic electron test particle computations with KORC show ≈ 50 % loss from the m = 3 RMP compared to the 10 %-15 % loss from the m = 1 RMP. Test particle computations of the m = 3 RMP in the time-evolving MHD simulation fields show correlation between MHD activity and late-time particle losses, but total electron confinement is similar to computations using magnetic-field snapshots.

Original language	English
Article number	052510
Journal	Physics of Plasmas
Volume	29
Issue number	5
DOIs	https://doi.org/10.1063/5.0087314
State	Published - May 1 2022

Funding

This article has been authored in part by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The publisher acknowledges the U.S. government license to provide public access under the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). M.T.B. and D.D-C.-N. were sponsored by the U.S. Department of Energy, Office of Science, Office of Advanced Scientific Computing Research, and Office of Fusion Energy Science, Scientific Discovery through the Advanced Computing (SciDAC) program at Oak Ridge National Laboratory, which is operated by UT-Batelle, LLC. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility located at Lawrence Berkeley National Laboratory, operated under Contract No. DE-AC02–05CH11231 using NERSC Award No. FES-ERCAP0016989. This research also used the computational resources and assistance of the UW-Madison Center For High Throughput Computing (CHTC) in the Department of Computer Sciences. The CHTC is supported by UW-Madison, the Advanced Computing Initiative, the Wisconsin Alumni Research Foundation, the Wisconsin Institutes for Discovery, and the National Science Foundation, and is an active member of the OSG Consortium, which is supported by the National Science Foundation and the U.S. Department of Energy’s Office of Science. The first author was supported by the U.S. Department of Energy, Office of Science, Office of Advanced Scientific Computing Research, Department of Energy Computational Science Graduate Fellowship under Award No. DE-FG02-97ER25308. Support for this research also came from the U.S. Department of Energy, Office of Science Award No. DE-SC0018001, as part of the Center for Tokamak Transient Simulation, and from Award Nos. DE-FC02-05ER54814, DE-SC0018266, and DE-SC0020245.

Funders	Funder number
Advanced Computing Initiative
Department of Energy Computational Science	DE-SC0018001, DE-SC0018266, DE-FC02-05ER54814, DE-FG02-97ER25308, DE-SC0020245
Wisconsin Institutes for Discovery
National Science Foundation
U.S. Department of Energy
Wisconsin Alumni Research Foundation
Office of Science
Advanced Scientific Computing Research
Fusion Energy Sciences
Oak Ridge National Laboratory
Lawrence Berkeley National Laboratory	FES-ERCAP0016989, DE-AC02
College of Engineering, University of Wisconsin-Madison

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abstract = "A numerical study of magnetohydrodynamics (MHD) and tracer-particle evolution investigates the effects of resonant magnetic perturbations (RMPs) on the confinement of runaway electrons (REs) in tokamak discharges conducted in the Madison Symmetric Torus. In computational results of applying RMPs having a broad toroidal spectrum but a single poloidal harmonic, m = 1 RMP does not suppress REs, whereas m = 3 RMP achieves significant deconfinement but not the complete suppression obtained in the experiment [Munaretto et al., Nuclear Fusion 60, 046024 (2020)]. MHD simulations with the NIMROD code produce sawtooth oscillations, and the associated magnetic reconnection can affect the trajectory of REs starting in the core region. Simulations with m = 3 RMP produce chaotic magnetic topology over the outer region, but the m = 1 RMP produces negligible changes in field topology, relative to applying no RMP. Using snapshots of the MHD simulation fields, full-orbit relativistic electron test particle computations with KORC show ≈ 50 % loss from the m = 3 RMP compared to the 10 %-15 % loss from the m = 1 RMP. Test particle computations of the m = 3 RMP in the time-evolving MHD simulation fields show correlation between MHD activity and late-time particle losses, but total electron confinement is similar to computations using magnetic-field snapshots.",

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Computational study of runaway electrons in MST tokamak discharges with applied resonant magnetic perturbation

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