Runaway electrons and magnetic island confinement

Boozer, Allen H.

doi:10.1063/1.4960969

Runaway electrons and magnetic island confinement

Journal Article · Fri Aug 19 00:00:00 EDT 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4960969· OSTI ID:1328739

Boozer, Allen H. ^[1]

Columbia Univ., New York, NY (United States); Columbia University

The breakup of magnetic surfaces is a central feature of ITER planning for the avoidance of damage due to runaway electrons. Rapid thermal quenches, which lead to large accelerating voltages, are thought to be due to magnetic surface breakup. Impurity injection to avoid and to mitigate both halo and runaway electron currents utilizes massive gas injection or shattered pellets. The actual deposition is away from the plasma center, and the breakup of magnetic surfaces is thought to spread the effects of the impurities across the plasma cross section. The breakup of magnetic surfaces would prevent runaway electrons from reaching relativistic energies were it not for the persistence of non-intercepting flux tubes. These are tubes of magnetic field lines that do not intercept the walls. In simulations and in magnetic field models, non-intercepting flux tubes are found to persist near the magnetic axis and in the cores of magnetic islands even when a large scale magnetic surface breakup occurs. As long as a few magnetic surfaces reform before all of the non-intercepting flux tubes dissipate, energetic electrons confined and accelerated in these flux tubes can serve as the seed electrons for a transfer of the overall plasma current from thermal to relativistic carriers. The acceleration of electrons is particularly strong because of the sudden changes in the poloidal flux that naturally occur in a rapid magnetic relaxation. Furthermore, the physics of magnetic islands as non-intercepting flux tubes is studied. Expressions are derived for (1) the size of islands required to confine energetic runaway electrons, (2) the accelerating electric field in an island, (3) the increase or reduction in the size of an island by the runaway electron current, (4) the approximate magnitude of the runaway current in an island, and (5) the time scale for the evolution of an island.

View Accepted Manuscript (DOE)

Research Organization:: Columbia Univ., New York, NY (United States)

Sponsoring Organization:: USDOE; USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)

Grant/Contract Number:: FG02-03ER54696

OSTI ID:: 1328739

Alternate ID(s):: OSTI ID: 1302505
OSTI ID: 22599889

Journal Information:: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 8 Vol. 23; ISSN PHPAEN; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited By (7)

Test particles dynamics in the JOREK 3D non-linear MHD code and application to electron transport in a disruption simulation Sommariva, Cristian; Nardon, Eric; Hoelzl, Matthias arXiv https://doi.org/10.48550/arxiv.1704.08955	text	January 2017
Simulations of the effects of pre-seeded magnetic islands on the generation of runaway current during disruption on J-TEXT Jiang, Z. H.; Huang, J.; Tong, R. H. Physics of Plasmas, Vol. 26, Issue 6 https://doi.org/10.1063/1.5100093	journal	June 2019
Kink instabilities of the post-disruption runaway electron beam at low safety factor Paz-Soldan, C.; Eidietis, N. W.; Liu, Y. Q. Plasma Physics and Controlled Fusion, Vol. 61, Issue 5 https://doi.org/10.1088/1361-6587/aafd15	journal	March 2019
Test particles dynamics in the JOREK 3D non-linear MHD code and application to electron transport in a disruption simulation Sommariva, C.; Nardon, E.; Beyer, P. Nuclear Fusion, Vol. 58, Issue 1 https://doi.org/10.1088/1741-4326/aa95cd	journal	December 2017
Electron acceleration in a JET disruption simulation Sommariva, C.; Nardon, E.; Beyer, P. Nuclear Fusion, Vol. 58, Issue 10 https://doi.org/10.1088/1741-4326/aad47d	journal	August 2018
Observation of toroidal Alfvén eigenmode excited by energetic electrons induced by static magnetic perturbations in the EAST tokamak Chu, N.; Sun, Y.; Gu, S. Nuclear Fusion, Vol. 58, Issue 10 https://doi.org/10.1088/1741-4326/aad70c	journal	August 2018
Electron acceleration in a JET disruption simulation Sommariva, Cristian; Nardon, Eric; Beyer, Peter arXiv https://doi.org/10.48550/arxiv.1805.05655	text	January 2018

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