Helical core formation and evolution during current ramp-up in the high-field tokamak Alcator C-Mod

Wingen, Andreas; Wilcox, Robert S.; Delgado-Aparicio, L.; Granetz, R. S.; Houshmandyar, S.; Shiraiwa, S.; Cianciosa, Mark R.; Seal, Sudip K.

doi:10.1063/1.5083055

Helical core formation and evolution during current ramp-up in the high-field tokamak Alcator C-Mod

Journal Article · Mon Feb 04 00:00:00 EST 2019 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.5083055· OSTI ID:1494895

^[1]; ^[1]; Delgado-Aparicio, L. ^[2]; ^[3]; ^[4]; Shiraiwa, S. ^[3]; ^[1]; ^[1]

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Univ. of Texas, Austin, TX (United States)

We report that large, spontaneous m/n = 1/1 helical cores are predicted in tokamaks with extended regions of low- or reversed-magnetic shear profiles in a region within the q = 1 surface and an onset condition determined by constant (dp/dρ)/B$$2\atop{t}$$ along the threshold. These 3D modes occurred frequently in Alcator C-Mod during ramp-up when slow current penetration results in a reversed shear q-profile. The onset and early development of a helical core in C-Mod were simulated using a new 3D time-dependent equilibrium reconstruction, based on the ideal MHD equilibrium code VMEC. The reconstruction used the experimental density, temperature, and soft-X-ray fluctuations. The pressure profile can become hollow due to an inverted, hollow electron temperature profile caused by molybdenum radiation in the plasma core during the current ramp-up phase before the onset of sawteeth, which may also occur in ITER with tungsten. Lastly, based on modeling, it is found that a reverse shear q-profile combined with a hollow pressure profile reduces the onset condition threshold, enabling helical core formation from an otherwise axisymmetric equilibrium.

View Accepted Manuscript (DOE)

Research Organization:: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE; USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)

Grant/Contract Number:: AC02-09CH11466; AC05-00OR22725; FC02-99ER54512

OSTI ID:: 1494895

Alternate ID(s):: OSTI ID: 1511782

Journal Information:: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 2 Vol. 26; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

References (28)

A nonlinear two-fluid model for toroidal plasmas Sugiyama, L. E.; Park, W. Physics of Plasmas, Vol. 7, Issue 11 https://doi.org/10.1063/1.1308083	journal	November 2000
The quiescent H-mode regime for high performance edge localized mode-stable operation in future burning plasmasa) Garofalo, A. M.; Burrell, K. H.; Eldon, D. Physics of Plasmas, Vol. 22, Issue 5 https://doi.org/10.1063/1.4921406	journal	May 2015
Magnetic flux pumping in 3D nonlinear magnetohydrodynamic simulations Krebs, I.; Jardin, S. C.; Günter, S. Physics of Plasmas, Vol. 24, Issue 10 https://doi.org/10.1063/1.4990704	journal	October 2017
Electron critical gradient scale length measurements of ICRF heated L-mode plasmas at Alcator C-Mod tokamak Houshmandyar, S.; Hatch, D. R.; Horton, C. W. Physics of Plasmas, Vol. 25, Issue 4 https://doi.org/10.1063/1.5022180	journal	April 2018
Steepest-descent moment method for three-dimensional magnetohydrodynamic equilibria Hirshman, S. P. Physics of Fluids, Vol. 26, Issue 12 https://doi.org/10.1063/1.864116	journal	January 1983
MHD activity in JET hot ion H mode discharges Nave, M. F. F.; Ali-Arshad, S.; Alper, B. Nuclear Fusion, Vol. 35, Issue 4 https://doi.org/10.1088/0029-5515/35/4/I04	journal	April 1995
Tungsten as target material in fusion devices Naujoks, D.; Asmussen, K.; Bessenrodt-Weberpals, M. Nuclear Fusion, Vol. 36, Issue 6 https://doi.org/10.1088/0029-5515/36/6/I01	journal	June 1996
Snake-like phenomena in Tore Supra following pellet injection Pecquet, A. -L; Cristofani, P.; Mattioli, M. Nuclear Fusion, Vol. 37, Issue 4 https://doi.org/10.1088/0029-5515/37/4/I03	journal	April 1997
Role of sawtooth in avoiding impurity accumulation and maintaining good confinement in JET radiative mantle discharges Nave, M. F. F.; Rapp, J.; Bolzonella, T. Nuclear Fusion, Vol. 43, Issue 10 https://doi.org/10.1088/0029-5515/43/10/023	journal	September 2003
Chapter 1: Overview and summary Shimada, M.; Campbell, D. J.; Mukhovatov, V. Nuclear Fusion, Vol. 47, Issue 6 https://doi.org/10.1088/0029-5515/47/6/S01	journal	June 2007
V3FIT: a code for three-dimensional equilibrium reconstruction Hanson, James D.; Hirshman, Steven P.; Knowlton, Stephen F. Nuclear Fusion, Vol. 49, Issue 7 https://doi.org/10.1088/0029-5515/49/7/075031	journal	July 2009
JET snake magnetohydrodynamic equilibria Cooper, W. A.; Graves, J. P.; Sauter, O. Nuclear Fusion, Vol. 51, Issue 7 https://doi.org/10.1088/0029-5515/51/7/072002	journal	June 2011
On the formation and stability of long-lived impurity-ion snakes in Alcator C-Mod Delgado-Aparicio, L.; Sugiyama, L.; Granetz, R. Nuclear Fusion, Vol. 53, Issue 4 https://doi.org/10.1088/0029-5515/53/4/043019	journal	April 2013
NBI fast ion confinement in the helical core of MAST hybrid-like plasmas Pfefferlé, D.; Graves, J. P.; Cooper, W. A. Nuclear Fusion, Vol. 54, Issue 6 https://doi.org/10.1088/0029-5515/54/6/064020	journal	May 2014
Free boundary equilibrium in 3D tokamaks with toroidal rotation Cooper, W. A.; Brunetti, D.; Faustin, J. M. Nuclear Fusion, Vol. 55, Issue 6 https://doi.org/10.1088/0029-5515/55/6/063032	journal	May 2015
Sawtooth oscillations Wesson, J. A. Plasma Physics and Controlled Fusion, Vol. 28, Issue 1A https://doi.org/10.1088/0741-3335/28/1A/022	journal	January 1986
Controlling sawtooth oscillations in tokamak plasmas Chapman, I. T. Plasma Physics and Controlled Fusion, Vol. 53, Issue 1 https://doi.org/10.1088/0741-3335/53/1/013001	journal	November 2010
Snake perturbation during pellet injection in the EAST tokamak Yao, Xingjia; Hu, Jiansheng; Xu, Liqing Plasma Physics and Controlled Fusion, Vol. 58, Issue 10 https://doi.org/10.1088/0741-3335/58/10/105006	journal	August 2016
Impact of ideal MHD stability limits on high-beta hybrid operation Piovesan, P.; Igochine, V.; Turco, F. Plasma Physics and Controlled Fusion, Vol. 59, Issue 1 https://doi.org/10.1088/0741-3335/59/1/014027	journal	November 2016
Helical core reconstruction of a DIII-D hybrid scenario tokamak discharge Cianciosa, M.; Wingen, A.; Hirshman, S. P. Nuclear Fusion, Vol. 57, Issue 7 https://doi.org/10.1088/1741-4326/aa6f82	journal	May 2017
Role of a continuous MHD dynamo in the formation of 3D equilibria in fusion plasmas Piovesan, P.; Bonfiglio, D.; Cianciosa, M. Nuclear Fusion, Vol. 57, Issue 7 https://doi.org/10.1088/1741-4326/aa700b	journal	May 2017
Use of reconstructed 3D equilibria to determine onset conditions of helical cores in tokamaks for extrapolation to ITER Wingen, A.; Wilcox, R. S.; Seal, S. K. Nuclear Fusion, Vol. 58, Issue 3 https://doi.org/10.1088/1741-4326/aaa33d	journal	January 2018
Formation and Stability of Impurity “Snakes” in Tokamak Plasmas Delgado-Aparicio, L.; Sugiyama, L.; Granetz, R. Physical Review Letters, Vol. 110, Issue 6 https://doi.org/10.1103/PhysRevLett.110.065006	journal	February 2013
Self-Organized Stationary States of Tokamaks Jardin, S. C.; Ferraro, N.; Krebs, I. Physical Review Letters, Vol. 115, Issue 21 https://doi.org/10.1103/PhysRevLett.115.215001	journal	November 2015
Internal Kink Modes in Toroidal Plasmas with Circular Cross Sections Bussac, M. N.; Pellat, R.; Edery, D. Physical Review Letters, Vol. 35, Issue 24 https://doi.org/10.1103/PhysRevLett.35.1638	journal	December 1975
Persistent density perturbations at rational- q surfaces following pellet injection in the Joint European Torus Weller, A.; Cheetham, A. D.; Edwards, A. W. Physical Review Letters, Vol. 59, Issue 20 https://doi.org/10.1103/PhysRevLett.59.2303	journal	November 1987
Control of Neoclassical Tearing Modes by Sawtooth Control Sauter, O.; Westerhof, E.; Mayoral, M. L. Physical Review Letters, Vol. 88, Issue 10 https://doi.org/10.1103/PhysRevLett.88.105001	journal	February 2002
Magnetic flux pumping in 3D nonlinear magnetohydrodynamic simulations Krebs, I.; Jardin, S. C.; Günter, S. arXiv https://doi.org/10.48550/arxiv.1706.06672	text	January 2017

Cited By (2)

Experimental observations of an n = 1 helical core accompanied by a saturated m / n = 2/1 tearing mode with low mode frequencies in JT-60U Bando, T.; Matsunaga, G.; Takechi, M. Plasma Physics and Controlled Fusion, Vol. 61, Issue 11 https://doi.org/10.1088/1361-6587/ab4612	journal	October 2019
Destabilization of field-line localized density fluctuation with a 1/1 internal kink mode in the EAST tokamak Li, G. S.; Zhang, T.; Wu, M. F. Nuclear Fusion, Vol. 59, Issue 9 https://doi.org/10.1088/1741-4326/ab2a42	journal	July 2019

Similar Records

Identification of Mercier instabilities in Alcator C-Mod tokamak

Journal Article · Thu Nov 30 23:00:00 EST 2000 · Physics of Plasmas · OSTI ID:40205967

Use of reconstructed 3D equilibria to determine onset conditions of helical cores in tokamaks for extrapolation to ITER

Journal Article · Sun Jan 14 19:00:00 EST 2018 · Nuclear Fusion · OSTI ID:1375431

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Helical core formation and evolution during current ramp-up in the high-field tokamak Alcator C-Mod

Citation Formats

References (28)

Cited By (2)

Similar Records

Related Subjects