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Title: Dynamics of MHD instabilities near a ferromagnetic wall

Abstract

We present that prospective fusion component testing and DEMO power reactor concepts are expected to employ low-activation ferritic steels because of their ability to withstand the high neutron flux of the reactor environment. However, theory suggests that ferromagnetic material may amplify certain external MHD instabilities. Using its ferromagnetic-resistive wall mode (FRWM) upgrade, the High Beta Tokamak-Extended Pulse (HBT-EP) experiment has observed approximately doubled growth rates when operating with a close-fitting ferromagnetic first wall, compared to operation with a stainless steel first wall. The presence of a ferromagnetic wall correlates with earlier disruptions, and FRWM growth rates increase with decreasing mode rotation, as expected due to the increased skin depth allowing greater mode interaction with the bulk ferromagnetic material. Finally, it is also seen that introducing low-n asymmetries into the toroidal distribution of ferromagnetic material, similar to the ITER test blanket module toroidal asymmetry, changes the phase preference of rotating modes; meanwhile, a similar change in purely conducting material does not significantly change the mode's phase preference.

Authors:
ORCiD logo [1];  [1];  [1]
  1. Columbia Univ., New York, NY (United States). Plasma Physics Laboratory
Publication Date:
Research Org.:
Columbia Univ., New York, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1485136
Grant/Contract Number:  
[FG02-86ER53222]
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
[ Journal Volume: 58; Journal Issue: 12]; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamaks; magnetohydrodynamics; plasma instabilities; ferromagnetic resistive wall mode

Citation Formats

Hughes, P. E., Levesque, J. P., and Navratil, G. A. Dynamics of MHD instabilities near a ferromagnetic wall. United States: N. p., 2018. Web. doi:10.1088/1741-4326/aade58.
Hughes, P. E., Levesque, J. P., & Navratil, G. A. Dynamics of MHD instabilities near a ferromagnetic wall. United States. doi:10.1088/1741-4326/aade58.
Hughes, P. E., Levesque, J. P., and Navratil, G. A. Mon . "Dynamics of MHD instabilities near a ferromagnetic wall". United States. doi:10.1088/1741-4326/aade58. https://www.osti.gov/servlets/purl/1485136.
@article{osti_1485136,
title = {Dynamics of MHD instabilities near a ferromagnetic wall},
author = {Hughes, P. E. and Levesque, J. P. and Navratil, G. A.},
abstractNote = {We present that prospective fusion component testing and DEMO power reactor concepts are expected to employ low-activation ferritic steels because of their ability to withstand the high neutron flux of the reactor environment. However, theory suggests that ferromagnetic material may amplify certain external MHD instabilities. Using its ferromagnetic-resistive wall mode (FRWM) upgrade, the High Beta Tokamak-Extended Pulse (HBT-EP) experiment has observed approximately doubled growth rates when operating with a close-fitting ferromagnetic first wall, compared to operation with a stainless steel first wall. The presence of a ferromagnetic wall correlates with earlier disruptions, and FRWM growth rates increase with decreasing mode rotation, as expected due to the increased skin depth allowing greater mode interaction with the bulk ferromagnetic material. Finally, it is also seen that introducing low-n asymmetries into the toroidal distribution of ferromagnetic material, similar to the ITER test blanket module toroidal asymmetry, changes the phase preference of rotating modes; meanwhile, a similar change in purely conducting material does not significantly change the mode's phase preference.},
doi = {10.1088/1741-4326/aade58},
journal = {Nuclear Fusion},
number = [12],
volume = [58],
place = {United States},
year = {2018},
month = {9}
}

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