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

Ebrahimi, F.; Raman, R.

doi:10.1088/0029-5515/56/4/044002

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

Journal Article · Wed Mar 23 00:00:00 EDT 2016 · Nuclear Fusion

DOI:https://doi.org/10.1088/0029-5515/56/4/044002· OSTI ID:1258451

^[1]; Raman, R. ^[2]

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Princeton Univ., Princeton, NJ (United States)
Univ. of Washington, Seattle, WA (United States)

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.

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Research Organization:: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: SC0010565; AC02-09CH11466; FG02-99ER54519

OSTI ID:: 1258451

Alternate ID(s):: OSTI ID: 1243000

Journal Information:: Nuclear Fusion, Vol. 56, Issue 4; Related Information: The digital data for this paper can be found in http://arks.princeton.edu/ark:/88435/dsp011v53k0334.; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 15 works

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Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection Ebrahimi, F.; Raman, R. Nuclear Fusion, Vol. 56, Issue 4, 34.65 MB https://doi.org/10.11578/1354837	dataset	April 2016
Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection Ebrahimi, F.; Raman, R. Nuclear Fusion, Vol. 56, Issue 4, 34.65 MB https://doi.org/10.11578/1366481	dataset	April 2016
Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection Ebrahimi, F.; Raman, R. Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States) https://doi.org/10.11578/1562059	dataset	January 2016

Cited By (8)

Nonlinear reconnecting edge localized modes in current-carrying plasmas Ebrahimi, F. Physics of Plasmas, Vol. 24, Issue 5 https://doi.org/10.1063/1.4983631	journal	May 2017
Numerical study and optimization of the formation and sustainment of a coaxial helicity injection spheromak O'Bryan, J. B.; Romero-Talamás, C. A.; Woodruff, S. Physics of Plasmas, Vol. 25, Issue 11 https://doi.org/10.1063/1.5043299	journal	November 2018
Application of transient CHI plasma startup to future ST and AT devices Hammond, K. C.; Raman, R.; Jardin, S. C. Physics of Plasmas, Vol. 26, Issue 3 https://doi.org/10.1063/1.5087259	journal	March 2019
Three-dimensional plasmoid-mediated reconnection and the effect of toroidal guide field in simulations of coaxial helicity injection Ebrahimi, F. Physics of Plasmas, Vol. 26, Issue 9 https://doi.org/10.1063/1.5098482	journal	September 2019
Initial results from solenoid-free plasma start-up using Transient CHI on QUEST Kuroda, K.; Raman, R.; Hanada, K. Plasma Physics and Controlled Fusion, Vol. 60, Issue 11 https://doi.org/10.1088/1361-6587/aadcb7	journal	September 2018
Application of Townsend avalanche theory to tokamak startup by coaxial helicity injection Hammond, K. C.; Raman, R.; Volpe, F. A. Nuclear Fusion, Vol. 58, Issue 1 https://doi.org/10.1088/1741-4326/aa8fa4	journal	November 2017
Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection Ebrahimi, F.; Raman, R. Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States) https://doi.org/10.11578/1562059	dataset	January 2016
Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection Ebrahimi, F.; Raman, R. Nuclear Fusion, Vol. 56, Issue 4, 34.65 MB https://doi.org/10.11578/1354837	dataset	April 2016