Spatiotemporal evolution of runaway electrons from synchrotron images in Alcator C-Mod

Tinguely, R. A.; Granetz, R. S.; Hoppe, M.; Embréus, O.

doi:10.1088/1361-6587/aae6ba

Spatiotemporal evolution of runaway electrons from synchrotron images in Alcator C-Mod

Journal Article · Thu Oct 25 00:00:00 EDT 2018 · Plasma Physics and Controlled Fusion

DOI:https://doi.org/10.1088/1361-6587/aae6ba· OSTI ID:1609301

^[1]; Granetz, R. S. ^[2]; ^[3]; ^[3]

Massachusetts Institute of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center; OSTI
Massachusetts Institute of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
Chalmers University of Technology, Gothenburg (Sweden)

We report in the Alcator C-Mod tokamak, relativistic runaway electron (RE) generation can occur during the flattop current phase of low density, diverted plasma discharges. Due to the high toroidal magnetic field (B₀ = 5.4 T), RE synchrotron radiation is measured by a wide-view camera in the visible wavelength range (λ ≈ 400–900 nm). In this paper, a statistical analysis of over one thousand camera images is performed to investigate the plasma conditions under which synchrotron emission is observed in C-Mod. In addition, the spatiotemporal evolution of REs during one particular discharge is explored in detail via a thorough analysis of the distortion-corrected synchrotron images. To accurately predict RE energies, the kinetic solver CODE is used to evolve the electron momentum-space distribution at six locations throughout the plasma: the magnetic axis and flux surfaces q = 1, 4/3, 3/2, 2, and 3. These results, along with the experimentally-measured magnetic topology and camera geometry, are input into the synthetic diagnostic SOFT to simulate synchrotron emission and detection. Interesting spatial structure near the surface q = 2 is found to coincide with the onset of a locked mode and increased MHD activity. Furthermore, the RE density profile evolution is fit by comparing experimental to synthetic images, providing important insight into RE spatiotemporal dynamics.

View Accepted Manuscript (DOE)

Research Organization:: Massachusetts Institute of Technology (MIT), Cambridge, MA (United States)

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

Grant/Contract Number:: FC02-99ER54512

OSTI ID:: 1609301

Alternate ID(s):: OSTI ID: 23001677

Report Number(s):: PPCF-102117

Journal Information:: Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 12 Vol. 60; ISSN 0741-3335

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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