Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Plasma Physics
Monday–Friday, October 30–November 3 2023; Denver, Colorado
Session JP11: Poster Session IV:
BEAMS: Laser- and beam-plasma interactions
Fundamental: Measurements and analysis in fundamental plasma physics; Plasma Sheaths, Sources, and Shocks
MFE: Turbulence and transport in fusion plasmas; High Field Tokamaks
2:00 PM - 5:00 PM
Tuesday, October 31, 2023
Room: Plaza ABC
Abstract: JP11.00118 : Fluctuations in the near and far scrape-off layer of Alcator C-Mod*
Presenter:
Aurora D Helgeland
(The University of Norway)
Authors:
Aurora D Helgeland
(The University of Norway)
Sajidah Ahmed
(UiT The Arctic University of Norway)
Juan M Losada
(UiT The Arctic University of Norway)
Audun Theodorsen
(UiT The Arctic University of Norway)
Dan Brunner
(Commonwealth Fusion Systems)
Adam Q Kuang
(Commonwealth Fusion Systems)
Brian LaBombard
(Massachusetts Institute of Technology MIT)
James L Terry
(Massachusetts Institute of Technology MI)
Odd Erik Garcia
(UiT The Arctic University of Norway)
The probe measurements close to the separatrix reveal that the time scale of the duration of the fluctuations is significantly shorter than that measured in the far SOL. These near-SOL fluctuations are close to normally distributed resulting in small relative fluctuations. In the far SOL there is an order unity relative fluctuation level and the probability density for the fluctuations is a strongly skewed Gamma distribution. It is demonstrated that the fluctuations become increasingly intermittent as the line-averaged density increases. A novel time delay estimation technique applied to GPI data reveals that the large-amplitude far SOL fluctuations are associated with blob structures moving radially outwards. The radial blob velocity increases significantly with line-averaged density, leading to profile broadening and flattening.
The results presented here emphasizes the role of large-amplitude fluctuations for plasma-wall interactions, which is particularly strong as the empirical discharge density limit is approached.
*Work supported by Tromsø Research Foundation under grant number 19_SG_AT and the UiT Aurora Centre Program, UiT The Arctic University of Norway (2020). Alcator C-Mod data were generated and maintained under US Department of Energy awards DE-FC02-99ER54512 and DE-SC0014264. Support for A. Q. Kuang was provided by Commonwealth Fusion System under the grant number RPP-022. Support for J. L. Terry was provided by the US Department of Energy, Fusion Energy Sciences, award DE-SC0014251.
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