Runaway electron transport in stochastic toroidal magnetic fields

L. Carbajal, D. Del-Castillo-Negrete, J. J. Martinell

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Abstract

In this work, we study the transport and confinement properties of runaway electrons (RE) in the presence of magnetic fields with perturbations producing different levels of stochasticity. We use Kinetic Orbit Runaway Electron Code (KORC) [Carbajal et al., Phys. Plasmas 24, 042512 (2017) and del-Castillo-Negrete et al., Phys. Plasmas 25, 056104 (2018)] for simulating the full-orbit (FO) and guiding-center (GC) dynamics of RE in perturbed magnetic fields that exhibit magnetic islands. We extend previous works on this problem [Wingen et al., Nucl. Fusion 46, 941 (2006); Izzo et al., Nucl. Fusion 51, 063032 (2011); Papp et al., Nucl. Fusion 51, 043004 (2011); V. Izzo and P. Parks, Phys. Plasmas 24, 060705 (2017); and Sommariva et al., Nucl. Fusion 58, 016043 (2018)] by studying in detail full-orbit effects on the RE dynamics. We quantify FO effects on RE transport by performing one-to-one comparisons between FO and GC simulations. It is found that, for the magnetic field configurations considered, GC simulations predict twice the RE losses of FO simulations for 1 MeV and four times the RE losses of FO simulations for 25 MeV. Similarly, we show how different GC and FO dynamics of RE moving around magnetic islands can be, especially in the scenario where the RE Larmor radius is on the order of the size of the magnetic island. We also study the role of rotation of the magnetic islands on RE confinement, and we find that low-frequency toroidal rotation has no observable effect on RE transport in the cases considered. These results shed some light into the potential of avoidance or mitigation mechanisms based on magnetic perturbations.

Original languageEnglish
Article number032502
JournalPhysics of Plasmas
Volume27
Issue number3
DOIs
StatePublished - Mar 1 2020

Funding

This work was partially funded by the National Autonomous University of Mexico (UNAM) through the PAPIIT Project No. IN112118 and the DGTIC Project No. LANCAD-UNAM-DGTIC-104. L.C. was sponsored by the Mexican postdoctoral fellowship program of the CONACYT-SENER fund for energetic sustainability. D.d.-C.-N. was sponsored by the Office of Fusion Energy Sciences of the U.S. Department of Energy at Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. We thank the referees for their thorough review of this manuscript.

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