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Title: A multi-machine scaling of halo current rotation

Halo currents generated during unmitigated tokamak disruptions are known to develop rotating asymmetric features that are of great concern to ITER because they can dynamically amplify the mechanical stresses on the machine. This paper presents a multi-machine analysis of these phenomena. More specifically, data from C-Mod, NSTX, ASDEX Upgrade, DIII-D, and JET are used to develop empirical scalings of three key quantities: the machine-specific minimum current quench time, $$ \newcommand{\tauCQ}{\tau_{{\rm CQ}}} \tauCQ$$; the halo current rotation duration, $$ \newcommand{\trot}{t_{{\rm rot}}} \newcommand{\tr}{{\rm tr}} \trot$$ ; and (3) the average halo current rotation frequency, $$ \newcommand{\favg}{\langle f_{{\rm h}} \rangle} \favg$$ . These data reveal that the normalized rotation duration, $$ \newcommand{\tauCQ}{\tau_{{\rm CQ}}} \newcommand{\trot}{t_{{\rm rot}}} \newcommand{\tr}{{\rm tr}} \trot/\tauCQ$$ , and the average rotation velocity, $$ \newcommand{\vavg}{\langle {v}_{{\rm h}} \rangle} \vavg$$ , are surprisingly consistent from machine to machine. Furthermore, comparisons between carbon and metal wall machines show that metal walls have minimal impact on the behavior of rotating halo currents. Finally, upon projecting to ITER, the empirical scalings indicate that substantial halo current rotation above $$ \newcommand{\favg}{\langle \,f_{{\rm h}} \rangle} \favg=20$$ Hz is to be expected. More importantly, depending on the projected value of $$ \newcommand{\tauCQ}{\tau_{{\rm CQ}}} \tauCQ$$ in ITER, substantial rotation could also occur in the resonant frequency range of 6–20 Hz. In conclusion, the possibility of damaging halo current rotation during unmitigated disruptions in ITER cannot be ruled out.
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [3] ;  [5]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Culham Science Centre, Abingdon (United Kingdom)
  4. MIT Plasma Science and Fusion Center, Cambridge, MA (United States)
  5. Max-Planck-Institut fur Plasmaphysik, Garching (Germany)
Publication Date:
Grant/Contract Number:
633053; EP/I501045; AC02-09CH11466; FC02-04ER54698; FG02-94ER54232
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 1; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org:
USDOE
Contributing Orgs:
JET Contributors
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamak; disruptions; halo currents
OSTI Identifier:
1414931

Myers, C. E., Eidietis, N. W., Gerasimov, S. N., Gerhardt, S. P., Granetz, R. S., Hender, T. C., and Pautasso, G.. A multi-machine scaling of halo current rotation. United States: N. p., Web. doi:10.1088/1741-4326/aa958b.
Myers, C. E., Eidietis, N. W., Gerasimov, S. N., Gerhardt, S. P., Granetz, R. S., Hender, T. C., & Pautasso, G.. A multi-machine scaling of halo current rotation. United States. doi:10.1088/1741-4326/aa958b.
Myers, C. E., Eidietis, N. W., Gerasimov, S. N., Gerhardt, S. P., Granetz, R. S., Hender, T. C., and Pautasso, G.. 2017. "A multi-machine scaling of halo current rotation". United States. doi:10.1088/1741-4326/aa958b.
@article{osti_1414931,
title = {A multi-machine scaling of halo current rotation},
author = {Myers, C. E. and Eidietis, N. W. and Gerasimov, S. N. and Gerhardt, S. P. and Granetz, R. S. and Hender, T. C. and Pautasso, G.},
abstractNote = {Halo currents generated during unmitigated tokamak disruptions are known to develop rotating asymmetric features that are of great concern to ITER because they can dynamically amplify the mechanical stresses on the machine. This paper presents a multi-machine analysis of these phenomena. More specifically, data from C-Mod, NSTX, ASDEX Upgrade, DIII-D, and JET are used to develop empirical scalings of three key quantities: the machine-specific minimum current quench time, $ \newcommand{\tauCQ}{\tau_{{\rm CQ}}} \tauCQ$; the halo current rotation duration, $ \newcommand{\trot}{t_{{\rm rot}}} \newcommand{\tr}{{\rm tr}} \trot$ ; and (3) the average halo current rotation frequency, $ \newcommand{\favg}{\langle f_{{\rm h}} \rangle} \favg$ . These data reveal that the normalized rotation duration, $ \newcommand{\tauCQ}{\tau_{{\rm CQ}}} \newcommand{\trot}{t_{{\rm rot}}} \newcommand{\tr}{{\rm tr}} \trot/\tauCQ$ , and the average rotation velocity, $ \newcommand{\vavg}{\langle {v}_{{\rm h}} \rangle} \vavg$ , are surprisingly consistent from machine to machine. Furthermore, comparisons between carbon and metal wall machines show that metal walls have minimal impact on the behavior of rotating halo currents. Finally, upon projecting to ITER, the empirical scalings indicate that substantial halo current rotation above $ \newcommand{\favg}{\langle \,f_{{\rm h}} \rangle} \favg=20$ Hz is to be expected. More importantly, depending on the projected value of $ \newcommand{\tauCQ}{\tau_{{\rm CQ}}} \tauCQ$ in ITER, substantial rotation could also occur in the resonant frequency range of 6–20 Hz. In conclusion, the possibility of damaging halo current rotation during unmitigated disruptions in ITER cannot be ruled out.},
doi = {10.1088/1741-4326/aa958b},
journal = {Nuclear Fusion},
number = 1,
volume = 58,
place = {United States},
year = {2017},
month = {12}
}