Energetic electron transport in magnetic fields with island chains and stochastic regions

Kostadinova, E. G.; Orlov, D. M.; Koepke, M.; Skiff, F.; Austin, M. E.

doi:10.1017/S0022377823000879

Energetic electron transport in magnetic fields with island chains and stochastic regions

Journal Article · Mon Sep 04 00:00:00 EDT 2023 · Journal of Plasma Physics

DOI:https://doi.org/10.1017/S0022377823000879· OSTI ID:1998018

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This paper investigates energetic electron transport in magnetized toroidal plasmas with magnetic fields characterized by island chains and regions of stochastic field lines produced by coil perturbations. We report on experiments performed in the DIII-D tokamak, which utilize electron cyclotron heating and current drive pulses to ‘tag’ electron populations within different locations across the discharge. The cross-field transport of these populations is then inferred from electron cyclotron emission measurements and gamma emission signals from scintillator detectors. Two types of energetic particles are distinguished and discussed: non-relativistic suprathermal electrons and relativistic runaway electrons. The magnetic field topology in each discharge is reconstructed with field-line tracing codes, which are also used to determine the location and scale of magnetic islands and stochastic regions. Comparison of simulations and experiments suggests that suprathermal transport is suppressed when the tagging is performed at a smaller radial location than the location of the $q = 1$ island chain and enhanced otherwise. Here q is the safety factor. We further demonstrate that increasing the width of the stochastic region within the edge plasma yields enhancement of the suprathermal electron transport.

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Research Organization:: General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE; USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: FC02-04ER54698; FG02-05ER54809; FG02-97ER54415; SC0021405; SC0023061

OSTI ID:: 1998018

Alternate ID(s):: OSTI ID: 1993934

Journal Information:: Journal of Plasma Physics, Journal Name: Journal of Plasma Physics Journal Issue: 4 Vol. 89; ISSN 0022-3778

Publisher:: Cambridge University Press (CUP)Copyright Statement

Country of Publication:: United Kingdom

Language:: English

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