Observation of Efficient Lower Hybrid Current Drive at High Density in Diverted Plasmas on the Alcator C-Mod Tokamak

Baek, S.  G.; Wallace, G.  M.; Bonoli, P.  T.; Brunner, D.; Faust, I.  C.; Hubbard, A.  E.; Hughes, J.  W.; LaBombard, B.; Parker, R.  R.; Porkolab, M.; Shiraiwa, S.; Wukitch, S.

doi:10.1103/physrevlett.121.055001

Observation of Efficient Lower Hybrid Current Drive at High Density in Diverted Plasmas on the Alcator C-Mod Tokamak

Journal Article · Fri Aug 03 00:00:00 EDT 2018 · Physical Review Letters

DOI:https://doi.org/10.1103/physrevlett.121.055001· OSTI ID:1541346

Baek, S. G. ^[1]; Wallace, G. M. ^[2]; Bonoli, P. T. ^[2]; Brunner, D. ^[2]; Faust, I. C. ^[3]; Hubbard, A. E. ^[2]; Hughes, J. W. ^[2]; LaBombard, B. ^[2]; Parker, R. R. ^[2]; Porkolab, M. ^[2]; Shiraiwa, S. ^[2]; Wukitch, S. ^[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
Massachusetts Institute of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center; Max Planck Institute for Plasma Physics, Munich (Germany)

Here, efficient lower hybrid current drive (LHCD) is demonstrated at densities up to $$\bar{n}_e$$ ≈ 1.5 x 10²⁰ m^–3 in diverted plasmas on the Alcator C-Mod tokamak by operating at increased plasma current - and therefore reduced Greenwald density fraction. This density exceeds the nominal “LH density limit” at $$\bar{n}_e$$ ≈ 1.0 x 10²⁰ m^–3 reported previously, above which an anomalous loss of current drive efficiency was observed. The recovery of current drive efficiency to a level consistent with engineering scalings is correlated with a reduction in density shoulders and turbulence levels in the far scrape-off layer. Concurrently, rf wave interaction with the edge and/or scrape-off-layer plasma is reduced, as indicated by a minimal broadening of the wave frequency spectrum measured at the plasma edge. These results have important implications for sustaining steady-state tokamak operation and indicate a pathway forward for implementing efficient LHCD in a reactor.

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

OSTI ID:: 1541346

Alternate ID(s):: OSTI ID: 1462787

Journal Information:: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 5 Vol. 121; ISSN 0031-9007

Publisher:: American Physical Society (APS)Copyright Statement

Country of Publication:: United States

Language:: English

References (36)

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
Current drive at plasma densities required for thermonuclear reactors Cesario, R.; Amicucci, L.; Cardinali, A. Nature Communications, Vol. 1, Issue 1 https://doi.org/10.1038/ncomms1052	journal	August 2010
Gas puff fueled H-mode discharges with good energy confinement above the Greenwald density limit on DIII-D Osborne, T. H.; Leonard, A. W.; Mahdavi, M. A. Physics of Plasmas, Vol. 8, Issue 5 https://doi.org/10.1063/1.1345504	journal	May 2001
Particle transport in the scrape-off layer and its relationship to discharge density limit in Alcator C-Mod LaBombard, B.; Boivin, R. L.; Greenwald, M. Physics of Plasmas, Vol. 8, Issue 5 https://doi.org/10.1063/1.1352596	journal	May 2001
Hard x-ray diagnostic for lower hybrid experiments on Alcator C-Mod Liptac, J.; Parker, R.; Tang, V. Review of Scientific Instruments, Vol. 77, Issue 10 https://doi.org/10.1063/1.2214695	journal	October 2006
Critical gradients and plasma flows in the edge plasma of Alcator C-Mod LaBombard, B.; Hughes, J. W.; Smick, N. Physics of Plasmas, Vol. 15, Issue 5 https://doi.org/10.1063/1.2838246	journal	May 2008
Lower hybrid current drive experiments on Alcator C-Mod: Comparison with theory and simulation Bonoli, P. T.; Ko, J.; Parker, R. Physics of Plasmas, Vol. 15, Issue 5 https://doi.org/10.1063/1.2904569	journal	May 2008
Absorption of lower hybrid waves in the scrape off layer of a diverted tokamak Wallace, G. M.; Parker, R. R.; Bonoli, P. T. Physics of Plasmas, Vol. 17, Issue 8 https://doi.org/10.1063/1.3465662	journal	August 2010
Review of recent experimental and modeling progress in the lower hybrid range of frequencies at ITER relevant parameters Bonoli, Paul T. Physics of Plasmas, Vol. 21, Issue 6 https://doi.org/10.1063/1.4884360	journal	June 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
Impact of SOL plasma profiles on lower hybrid current drive: Experimental evidence, mitigation and modeling approaches Shiraiwa, S.; Baek, S. G.; Faust, I. RADIO FREQUENCY POWER IN PLASMAS: Proceedings of the 21st Topical Conference, AIP Conference Proceedings https://doi.org/10.1063/1.4936481	conference	January 2015
Lower hybrid wave edge power loss quantification on the Alcator C-Mod tokamak Faust, I. C.; Brunner, D.; LaBombard, B. Physics of Plasmas, Vol. 23, Issue 5 https://doi.org/10.1063/1.4951736	journal	May 2016
Current relaxation time scales in toroidal plasmas Mikkelsen, D. R. Physics of Fluids B: Plasma Physics, Vol. 1, Issue 2 https://doi.org/10.1063/1.859146	journal	February 1989
Parametric instabilities due to lower-hybrid radio frequency heating of tokamak plasmas Porkolab, Miklos Physics of Fluids, Vol. 20, Issue 12 https://doi.org/10.1063/1.861825	journal	January 1977
Parametric excitation of ion-sound quasimodes during lower-hybrid heating experiments in tokamaks Takase, Yuichi Physics of Fluids, Vol. 26, Issue 10 https://doi.org/10.1063/1.864022	journal	January 1983
Spectral broadening of lower-hybrid waves by time-dependent density fluctuations Andrews, P. L. Physics of Fluids, Vol. 26, Issue 9 https://doi.org/10.1063/1.864444	journal	January 1983
Observation of parametric instabilities in the lower-hybrid range of frequencies in the high-density tokamak Takase, Y.; Porkolab, M.; Schuss, J. J. Physics of Fluids, Vol. 28, Issue 3 https://doi.org/10.1063/1.865070	journal	January 1985
Waveguide launching of lower hybrid waves Brambilla, M. Nuclear Fusion, Vol. 19, Issue 10 https://doi.org/10.1088/0029-5515/19/10/006	journal	October 1979
Measurement of the hot electrical conductivity in the PBX-M tokamak Giruzzi, G.; Barbato, E.; Bernabei, S. Nuclear Fusion, Vol. 37, Issue 5 https://doi.org/10.1088/0029-5515/37/5/I09	journal	May 1997
Transport-driven Scrape-Off-Layer flows and the boundary conditions imposed at the magnetic separatrix in a tokamak plasma LaBombard, B.; Rice, J. E.; Hubbard, A. E. Nuclear Fusion, Vol. 44, Issue 10 https://doi.org/10.1088/0029-5515/44/10/001	journal	September 2004
Lower hybrid current drive at high density in Alcator C-Mod Wallace, G. M.; Hubbard, A. E.; Bonoli, P. T. Nuclear Fusion, Vol. 51, Issue 8 https://doi.org/10.1088/0029-5515/51/8/083032	journal	July 2011
High-density H-mode operation by pellet injection and ELM mitigation with the new active in-vessel saddle coils in ASDEX Upgrade Lang, P. T.; Suttrop, W.; Belonohy, E. Nuclear Fusion, Vol. 52, Issue 2 https://doi.org/10.1088/0029-5515/52/2/023017	journal	January 2012
Experimental investigations of LHW–plasma coupling and current drive related to achieving H-mode plasmas in EAST Ding, B. J.; Kong, E. H.; Li, M. H. Nuclear Fusion, Vol. 53, Issue 11 https://doi.org/10.1088/0029-5515/53/11/113027	journal	October 2013
Lower hybrid current drive at high density on Tore Supra Goniche, M.; Basiuk, V.; Decker, J. Nuclear Fusion, Vol. 53, Issue 3 https://doi.org/10.1088/0029-5515/53/3/033010	journal	February 2013
On the physics guidelines for a tokamak DEMO Zohm, H.; Angioni, C.; Fable, E. Nuclear Fusion, Vol. 53, Issue 7 https://doi.org/10.1088/0029-5515/53/7/073019	journal	June 2013
High density LHRF experiments in Alcator C-Mod and implications for reactor scale devices Baek, S. G.; Parker, R. R.; Bonoli, P. T. Nuclear Fusion, Vol. 55, Issue 4 https://doi.org/10.1088/0029-5515/55/4/043009	journal	March 2015
ADX: a high field, high power density, advanced divertor and RF tokamak LaBombard, B.; Marmar, E.; Irby, J. Nuclear Fusion, Vol. 55, Issue 5 https://doi.org/10.1088/0029-5515/55/5/053020	journal	April 2015
Review of experiments on current drive in Tokamaks by means of RF waves Hooke, W. Plasma Physics and Controlled Fusion, Vol. 26, Issue 1A https://doi.org/10.1088/0741-3335/26/1A/312	journal	January 1984
Advances in modeling of lower hybrid current drive Peysson, Y.; Decker, J.; Nilsson, E. Plasma Physics and Controlled Fusion, Vol. 58, Issue 4 https://doi.org/10.1088/0741-3335/58/4/044008	journal	February 2016
Experimental and modeling uncertainties in the validation of lower hybrid current drive Poli, F. M.; Bonoli, P. T.; Chilenski, M. Plasma Physics and Controlled Fusion, Vol. 58, Issue 9 https://doi.org/10.1088/0741-3335/58/9/095001	journal	July 2016
Observation of Parametric Instabilities in Lower-Hybrid Radio-Frequency Heating of Tokamaks Porkolab, M.; Bernabei, S.; Hooke, W. M. Physical Review Letters, Vol. 38, Issue 5 https://doi.org/10.1103/PhysRevLett.38.230	journal	January 1977
Confining a Tokamak Plasma with rf-Driven Currents Fisch, Nathaniel J. Physical Review Letters, Vol. 41, Issue 13 https://doi.org/10.1103/PhysRevLett.41.873	journal	September 1978
Creating an Asymmetric Plasma Resistivity with Waves Fisch, N. J.; Boozer, A. H. Physical Review Letters, Vol. 45, Issue 9 https://doi.org/10.1103/PhysRevLett.45.720	journal	September 1980
Confining a Tokamak Plasma with rf-Driven Currents. Fisch, Nathaniel J. Physical Review Letters, Vol. 42, Issue 6 https://doi.org/10.1103/physrevlett.42.410.2	journal	February 1979
Wave-Particle Studies in the Ion Cyclotron and Lower Hybrid Ranges of Frequencies in Alcator C-Mod Bonoli, P. T.; Parker, R.; Wukitch, S. J. Fusion Science and Technology, Vol. 51, Issue 3 https://doi.org/10.13182/FST07-A1430	journal	April 2007
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

Cited By (5)

Lower hybrid wave absorption study to improve the calculation of energy confinement time in EAST Gu, X.; Shen, B.; Li, M. Physics of Plasmas, Vol. 25, Issue 9 https://doi.org/10.1063/1.5047226	journal	September 2018
Nonlinearity in parametric instabilities during the injection of lower hybrid waves into tokamak plasmas Liu, Zhiyuan; Gao, Zhe; Zhao, Aihui Physics of Plasmas, Vol. 26, Issue 4 https://doi.org/10.1063/1.5088553	journal	April 2019
Experimental evidence of lower hybrid wave scattering in Alcator C-Mod due to scrape off layer density fluctuations Martin, E. H.; Lau, C.; Wallace, G. M. Nuclear Fusion, Vol. 59, Issue 7 https://doi.org/10.1088/1741-4326/ab16a2	journal	May 2019
Summary of the 27th IAEA Fusion Energy Conference in the categories of EX/W, EX/D, and ICC Ida, K. Nuclear Fusion, Vol. 59, Issue 11 https://doi.org/10.1088/1741-4326/ab3811	journal	September 2019
Full-wave model for the lower hybrid wave electric field vector with synthetic turbulence on Alcator C-Mod Lau, C.; Martin, E. H.; Shiraiwa, S. Nuclear Fusion, Vol. 60, Issue 3 https://doi.org/10.1088/1741-4326/ab6481	journal	January 2020

Similar Records

Observation of Efficient Lower Hybrid Current Drive at High Density in Diverted Plasmas on the Alcator C-Mod Tokamak

Dataset · Thu Jan 17 23:00:00 EST 2019 · OSTI ID:1881223

Lower Hybrid Wave Induced SOL Emissivity Variation at High Density on the Alcator C-Mod Tokamak

Journal Article · Thu Dec 22 23:00:00 EST 2011 · AIP Conference Proceedings · OSTI ID:21612483

Lower hybrid wave edge power loss quantification on the Alcator C-Mod tokamak

Journal Article · Fri May 20 00:00:00 EDT 2016 · Physics of Plasmas · OSTI ID:1894447

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Fokker-Planck Model
Tokamaks
Vlasov model
current drive
gamma ray plasma measurements
microwave plasma measurements
radio-frequency measurements
wave-particle interactions
wave-wave
x-ray

Observation of Efficient Lower Hybrid Current Drive at High Density in Diverted Plasmas on the Alcator C-Mod Tokamak

Citation Formats

References (36)

Cited By (5)

Similar Records

Related Subjects