The dependence of divertor power sharing on magnetic flux balance in near double-null configurations on Alcator C-Mod

Brunner, D.; Kuang, A. Q.; LaBombard, B.; Terry, J. L.

doi:10.1088/1741-4326/aac006

The dependence of divertor power sharing on magnetic flux balance in near double-null configurations on Alcator C-Mod

Journal Article · Fri May 11 00:00:00 EDT 2018 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/aac006· OSTI ID:1540539

^[1]; Kuang, A. Q. ^[2]; ^[2]; ^[2]

Massachusetts Institute of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center; OSTI
Massachusetts Institute of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center

We report management of power exhaust will be a crucial task for tokamak fusion reactors. Reactor concepts are often proposed with double-null divertors, i.e. having two magnetic separatrices in an up-down symmetric configuration. This arrangement is potentially advantageous since the majority of the tokamak exhaust power tends to flow to the outer pair of divertor legs at large major radius, where the geometry is favorable for spreading the heat over a large surface area and there is more room for advanced divertor configurations. Despite the importance, there have been relatively few studies of divertor power sharing in near double null configurations and no studies at the poloidal magnetic fields and scrape-off layer power widths anticipated for a reactor. Motivated by this need we have undertaken a systematic study on Alcator C-Mod, examining the effect of magnetic flux balance on the power sharing among the four divertor legs in near double-null plasmas. Ohmic L-modes at three values of plasma current and ICRF-heated enhanced D-alpha (EDA) H-modes and I-modes at a single value of plasma current are explored, producing poloidal magnetic fields of 0.42, 0.62 and 0.85 Tesla. For Ohmic L-modes and ICRF-heated EDA H-modes, we find that the point of equal power sharing between upper and lower divertors occurs remarkably close to a balanced double null. Power sharing amongst the outer (upper versus lower) and inner (upper versus lower) pairs of divertors can be described in terms of a logistic function of magnetic flux balance, consistent with heat flux mapping along magnetic field lines to the outer midplane. Power sharing between inner and outer legs is found to follow a Gaussian-like function of magnetic flux balance with non-zero power to the inner divertors at double null. The overall behavior of H-modes operated near double null and for I-modes operating to within one heat flux e-folding of double null are found similar to Ohmic L-modes, with a significant reduction of power on the inner divertor legs. The results are encapsulated in terms of empirically-informed analytic functions of magnetic flux balance. When combined with magnetic equilibrium control system specifications, these relationships can be used to specify the power flux handling requirements for each of the four divertor target plates.

View Accepted Manuscript (DOE)

Research Organization:: Massachusetts Institute of Technology (MIT), Cambridge, MA (United States)

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

Grant/Contract Number:: FC02-99ER54512; SC0014264

OSTI ID:: 1540539

Alternate ID(s):: OSTI ID: 22929422

Report Number(s):: NF-102297

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 7 Vol. 58; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

References (38)

Current Flow Parallel to the Field in a Scrape-Off Layer Harbour, P. J. Contributions to Plasma Physics, Vol. 28, Issue 4-5 https://doi.org/10.1002/ctpp.2150280424	journal	January 1988
PDX Divertor operation Owens, D. K.; Arunasalam, V.; Barnes, C. Journal of Nuclear Materials, Vol. 93-94 https://doi.org/10.1016/0022-3115(80)90324-4	journal	October 1980
The effect of divertor magnetic balance on H-mode performance in DIII-D Petrie, T. W.; Greenfield, C. M.; Grobener, R. J. Journal of Nuclear Materials, Vol. 290-293 https://doi.org/10.1016/S0022-3115(00)00492-X	journal	March 2001
Changes in edge and scrape-off layer plasma behavior due to variation in magnetic balance in DIII-D Petrie, T.; Watkins, J.; Baylor, L. Journal of Nuclear Materials, Vol. 313-316 https://doi.org/10.1016/S0022-3115(02)01459-9	journal	March 2003
Experimental investigation of transport phenomena in the scrape-off layer and divertor Labombard, B.; Goetz, J. A.; Hutchinson, I. Journal of Nuclear Materials, Vol. 241-243 https://doi.org/10.1016/S0022-3115(97)80037-2	journal	February 1997
Asymmetries in the divertor power loading in START Morel, K. M.; Counsell, G. F.; Helander, P. Journal of Nuclear Materials, Vol. 266-269 https://doi.org/10.1016/S0022-3115(98)00851-4	journal	March 1999
FIRE, a next step option for magnetic fusion Meade, D. M. Fusion Engineering and Design, Vol. 63-64 https://doi.org/10.1016/S0920-3796(02)00282-X	journal	December 2002
Spherical torus concept as power plants—the ARIES-ST study Najmabadi, F. Fusion Engineering and Design, Vol. 65, Issue 2 https://doi.org/10.1016/S0920-3796(02)00302-2	journal	February 2003
ARC: A compact, high-field, fusion nuclear science facility and demonstration power plant with demountable magnets Sorbom, B. N.; Ball, J.; Palmer, T. R. Fusion Engineering and Design, Vol. 100 https://doi.org/10.1016/j.fusengdes.2015.07.008	journal	November 2015
Plasma profiles and flows in the high-field side scrape-off layer in Alcator C-Mod Smick, N.; LaBombard, B.; Pitcher, C. S. Journal of Nuclear Materials, Vol. 337-339 https://doi.org/10.1016/j.jnucmat.2004.09.035	journal	March 2005
The dynamics and structure of edge-localized-modes in Alcator C-Mod Terry, J. L.; Cziegler, I.; Hubbard, A. E. Journal of Nuclear Materials, Vol. 363-365 https://doi.org/10.1016/j.jnucmat.2007.01.266	journal	June 2007
Heat load asymmetries in MAST De Temmerman, G.; Kirk, A.; Nardon, E. Journal of Nuclear Materials, Vol. 415, Issue 1 https://doi.org/10.1016/j.jnucmat.2010.10.003	journal	August 2011
Heat-flux footprints for I-mode and EDA H-mode plasmas on Alcator C-Mod Terry, J. L.; LaBombard, B.; Brunner, D. Journal of Nuclear Materials, Vol. 438 https://doi.org/10.1016/j.jnucmat.2013.01.029	journal	July 2013
Scaling of the power exhaust channel in Alcator C-Mod LaBombard, B.; Terry, J. L.; Hughes, J. W. Physics of Plasmas, Vol. 18, Issue 5 https://doi.org/10.1063/1.3566059	journal	May 2011
Surface thermocouples for measurement of pulsed heat flux in the divertor of the Alcator C-Mod tokamak Brunner, D.; LaBombard, B. Review of Scientific Instruments, Vol. 83, Issue 3 https://doi.org/10.1063/1.3689770	journal	March 2012
Divertor asymmetry and scrape-off layer flow in various divertor configurations in Experimental Advanced Superconducting Tokamak Liu, S. C.; Guo, H. Y.; Xu, G. S. Physics of Plasmas, Vol. 19, Issue 4 https://doi.org/10.1063/1.4707396	journal	April 2012
Edge-localized-modes in tokamaks Leonard, A. W. Physics of Plasmas, Vol. 21, Issue 9 https://doi.org/10.1063/1.4894742	journal	September 2014
20 years of research on the Alcator C-Mod tokamaka) Greenwald, M.; Bader, A.; Baek, S. Physics of Plasmas, Vol. 21, Issue 11 https://doi.org/10.1063/1.4901920	journal	November 2014
Pfirsch-Schluter currents in the JET divertor Schaffer, M. J.; Chankin, A. V.; Guo, H. Y. Nuclear Fusion, Vol. 37, Issue 1 https://doi.org/10.1088/0029-5515/37/1/I07	journal	January 1997
Variation of particle exhaust with changes in divertor magnetic balance Petrie, T. W.; Allen, S. L.; Brooks, N. H. Nuclear Fusion, Vol. 46, Issue 1 https://doi.org/10.1088/0029-5515/46/1/007	journal	December 2005
Comparison of radiating divertor behaviour in single-null and double-null plasmas in DIII-D Petrie, T. W.; Brooks, N. H.; Fenstermacher, M. E. Nuclear Fusion, Vol. 48, Issue 4 https://doi.org/10.1088/0029-5515/48/4/045010	journal	March 2008
I-mode: an H-mode energy confinement regime with L-mode particle transport in Alcator C-Mod Whyte, D. G.; Hubbard, A. E.; Hughes, J. W. Nuclear Fusion, Vol. 50, Issue 10 https://doi.org/10.1088/0029-5515/50/10/105005	journal	August 2010
Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma Smick, N.; LaBombard, B.; Hutchinson, I. H. Nuclear Fusion, Vol. 53, Issue 2 https://doi.org/10.1088/0029-5515/53/2/023001	journal	January 2013
Scaling of the tokamak near the scrape-off layer H-mode power width and implications for ITER Eich, T.; Leonard, A. W.; Pitts, R. A. Nuclear Fusion, Vol. 53, Issue 9 https://doi.org/10.1088/0029-5515/53/9/093031	journal	August 2013
Diagnostics and control for the steady state and pulsed tokamak DEMO Orsitto, F. P.; Villari, R.; Moro, F. Nuclear Fusion, Vol. 56, Issue 2 https://doi.org/10.1088/0029-5515/56/2/026009	journal	January 2016
Plasma Boundary Layer in Limiter and Divertor Tokamaks Keilhacker, M.; Lackner, K.; Behringer, K. Physica Scripta, Vol. T2B https://doi.org/10.1088/0031-8949/1982/T2B/022	journal	January 1982
Physics Aspects of the Compact Ignition Tokamak Post, D.; Houlberg, W.; Bateman, G. Physica Scripta, Vol. T16 https://doi.org/10.1088/0031-8949/1987/T16/011	journal	January 1987
Studies of EDA H-mode in Alcator C-Mod Greenwald, M.; Boivin, R.; Bonoli, P. Plasma Physics and Controlled Fusion, Vol. 42, Issue 5A https://doi.org/10.1088/0741-3335/42/5A/331	journal	May 2000
ELM characteristics in MAST Kirk, A.; Counsell, G. F.; Wilson, H. R. Plasma Physics and Controlled Fusion, Vol. 46, Issue 3 https://doi.org/10.1088/0741-3335/46/3/009	journal	February 2004
Thermographic study of heat load asymmetries during MAST L-mode discharges De Temmerman, G.; Delchambre, E.; Dowling, J. Plasma Physics and Controlled Fusion, Vol. 52, Issue 9 https://doi.org/10.1088/0741-3335/52/9/095005	journal	July 2010
An assessment of ion temperature measurements in the boundary of the Alcator C-Mod tokamak and implications for ion fluid heat flux limiters Brunner, D.; LaBombard, B.; Churchill, R. M. Plasma Physics and Controlled Fusion, Vol. 55, Issue 9 https://doi.org/10.1088/0741-3335/55/9/095010	journal	July 2013
Impurity screening behavior of the high-field side scrape-off layer in near-double-null configurations: prospect for mitigating plasma–material interactions on RF actuators and first-wall components LaBombard, B.; Kuang, A. Q.; Brunner, D. Nuclear Fusion, Vol. 57, Issue 7 https://doi.org/10.1088/1741-4326/aa6dd2	journal	May 2017
Physics and performance of the I-mode regime over an expanded operating space on Alcator C-Mod Hubbard, A. E.; Baek, S. -G.; Brunner, D. Nuclear Fusion, Vol. 57, Issue 12 https://doi.org/10.1088/1741-4326/aa8570	journal	October 2017
ITER: Physics basis Post, D. E. 1990 Plasma Science IEEE Conference Record - Abstracts https://doi.org/10.1109/PLASMA.1990.110570	conference	January 1990
The ARIES Advanced and Conservative Tokamak Power Plant Study Kessel, C. E.; Tillack, M. S.; Najmabadi, F. Fusion Science and Technology, Vol. 67, Issue 1 https://doi.org/10.13182/FST14-794	journal	January 2015
The ARIES-I Tokamak Reactor Study ^† Najmabadi, F.; Conn, R. W.; Bathke, C. G. Fusion Technology, Vol. 19, Issue 3P2A https://doi.org/10.13182/FST91-A29440	journal	May 1991
II. Device Description and General Physics Requirements Neilson, G. H. Fusion Technology, Vol. 21, Issue 3P1 https://doi.org/10.13182/FST92-A29892	journal	May 1992
ARC: A compact, high-field, fusion nuclear science facility and demonstration power plant with demountable magnets Sorbom, B. N.; Ball, J.; Palmer, T. R. arXiv https://doi.org/10.48550/arxiv.1409.3540	text	January 2014

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