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Title: Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection

Abstract

A large-volume flux closure during transient coaxial helicity injection (CHI) in NSTX-U is demonstrated through resistive magnetohydrodynamics (MHD) simulations. Several major improvements, including the improved positioning of the divertor poloidal field coils, are projected to improve the CHI start-up phase in NSTX-U. Simulations in the NSTX-U configuration with constant in time coil currents show that with strong flux shaping the injected open field lines (injector flux) rapidly reconnect and form large volume of closed flux surfaces. This is achieved by driving parallel current in the injector flux coil and oppositely directed currents in the flux shaping coils to form a narrow injector flux footprint and push the injector flux into the vessel. As the helicity and plasma are injected into the device, the oppositely directed field lines in the injector region are forced to reconnect through a local Sweet-Parker type reconnection, or to spontaneously reconnect when the elongated current sheet becomes MHD unstable to form plasmoids. In these simulations for the first time, it is found that the closed flux is over 70% of the initial injector flux used to initiate the discharge. Furthermore, these results could work well for the application of transient CHI in devices that employ supermore » conducting coils to generate and sustain the plasma equilibrium.« less

Authors:
ORCiD logo [1];  [2]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Princeton Univ., Princeton, NJ (United States)
  2. Univ. of Washington, Seattle, WA (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1258451
Alternate Identifier(s):
OSTI ID: 1243000
Grant/Contract Number:  
SC0010565; AC02-09CH11466; FG02-99ER54519
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 56; Journal Issue: 4; Related Information: The digital data for this paper can be found in http://arks.princeton.edu/ark:/88435/dsp011v53k0334.; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Ebrahimi, F., and Raman, R. Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection. United States: N. p., 2016. Web. doi:10.1088/0029-5515/56/4/044002.
Ebrahimi, F., & Raman, R. Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection. United States. doi:10.1088/0029-5515/56/4/044002.
Ebrahimi, F., and Raman, R. Wed . "Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection". United States. doi:10.1088/0029-5515/56/4/044002. https://www.osti.gov/servlets/purl/1258451.
@article{osti_1258451,
title = {Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection},
author = {Ebrahimi, F. and Raman, R.},
abstractNote = {A large-volume flux closure during transient coaxial helicity injection (CHI) in NSTX-U is demonstrated through resistive magnetohydrodynamics (MHD) simulations. Several major improvements, including the improved positioning of the divertor poloidal field coils, are projected to improve the CHI start-up phase in NSTX-U. Simulations in the NSTX-U configuration with constant in time coil currents show that with strong flux shaping the injected open field lines (injector flux) rapidly reconnect and form large volume of closed flux surfaces. This is achieved by driving parallel current in the injector flux coil and oppositely directed currents in the flux shaping coils to form a narrow injector flux footprint and push the injector flux into the vessel. As the helicity and plasma are injected into the device, the oppositely directed field lines in the injector region are forced to reconnect through a local Sweet-Parker type reconnection, or to spontaneously reconnect when the elongated current sheet becomes MHD unstable to form plasmoids. In these simulations for the first time, it is found that the closed flux is over 70% of the initial injector flux used to initiate the discharge. Furthermore, these results could work well for the application of transient CHI in devices that employ super conducting coils to generate and sustain the plasma equilibrium.},
doi = {10.1088/0029-5515/56/4/044002},
journal = {Nuclear Fusion},
number = 4,
volume = 56,
place = {United States},
year = {2016},
month = {3}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 5 works
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Figures / Tables:

FIG. 1. FIG. 1.: Line drawing showing the main components in NSTX-U required for plasma start-up using CHI. The initial poloidal field, the injector-flux (shown by the blue ellipse), connecting the inner and outer divertor plates in the injector region is produced using the lower divertor coils (shown with numbers1,2). The primarymore » injector coil (PF1CL) and the flux shaping coils (PF2L and PF1AL) used in the simulations are shown with numbers 2, 3 and 5, respectively.« less

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Works referenced in this record:

Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection
dataset, April 2016

  • Ebrahimi, F.; Raman, R.
  • Nuclear Fusion, Vol. 56, Issue 4, 34.65 MB
  • DOI: 10.11578/1366481

Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection
dataset, April 2016

  • Ebrahimi, F.; Raman, R.
  • Nuclear Fusion, Vol. 56, Issue 4, 34.65 MB
  • DOI: 10.11578/1366481

Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection
dataset, April 2016

  • Ebrahimi, F.; Raman, R.
  • Nuclear Fusion, Vol. 56, Issue 4, 34.65 MB
  • DOI: 10.11578/1354837

Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection
dataset, January 2016

  • Ebrahimi, F.; Raman, R.
  • Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
  • DOI: 10.11578/1562059

Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection
dataset, April 2016

  • Ebrahimi, F.; Raman, R.
  • Nuclear Fusion, Vol. 56, Issue 4, 34.65 MB
  • DOI: 10.11578/1354837

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    Works referencing / citing this record:

    Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection
    dataset, April 2016

    • Ebrahimi, F.; Raman, R.
    • Nuclear Fusion, Vol. 56, Issue 4, 34.65 MB
    • DOI: 10.11578/1366481

    Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection
    dataset, April 2016

    • Ebrahimi, F.; Raman, R.
    • Nuclear Fusion, Vol. 56, Issue 4, 34.65 MB
    • DOI: 10.11578/1354837

    Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection
    dataset, January 2016

    • Ebrahimi, F.; Raman, R.
    • Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
    • DOI: 10.11578/1562059

      Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.