Improved confinement in high-density H-modes via modification of the plasma boundary with lower hybrid wavesa)
Abstract
Injecting Lower Hybrid Range of Frequency (LHRF) waves into Alcator C-Mod's high-density H-mode plasmas has led to enhanced global energy confinement by increasing pedestal temperature and pressure gradients, decreasing the separatrix density, modifying the pedestal radial electric field and rotation, and decreasing edge turbulence. These experiments imply that edge LHRF can be used as an actuator to increase energy confinement via modification of boundary quantities. H98-factor increases of up to ~35% (e.g., H98 from 0.75 to 1.0) are seen when moderate amounts of LH power (PLH/Ptot~0.15) are applied to H-modes of densities $$\overline{n}$$e~3 × 1020 m–3, corresponding to values ~0.5 of the Greenwald density. However, the magnitude of the improvement is reduced if the confinement quality of the target H-mode plasma is already good (i.e., H98target ~ 1). Ray-tracing modeling and accessibility calculations for the LH waves indicate that they do not penetrate to the core. The LHRF power appears to be deposited in plasma boundary region, with a large fraction of the injected power increment appearing promptly on the outer divertor target. There is no evidence that the LH waves are driving current in these plasmas. The LHRF-actuated improvements are well correlated with suppressed pedestal density fluctuations in themore »
- Authors:
-
more »
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of York (United Kingdom)
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Ecole Polytechnique Federale Lausanne (Switzlerland)
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Publication Date:
- Research Org.:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Contributing Org.:
- C-Mod Team
- OSTI Identifier:
- 1547003
- Alternate Identifier(s):
- OSTI ID: 1228177
- Grant/Contract Number:
- FC02-99ER54512; AC02-09CH11466
- Resource Type:
- Journal Article: Accepted Manuscript
- Journal Name:
- Physics of Plasmas
- Additional Journal Information:
- Journal Volume: 22; Journal Issue: 5; Journal ID: ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Citation Formats
Terry, J. L., Reinke, M. L., Hughes, J. W., LaBombard, B., Theiler, C., Wallace, G. M., Baek, S. G., Brunner, D., Churchill, R. M., Edlund, E., Ennever, P., Faust, I., Golfinopoulos, T., Greenwald, M., Hubbard, A. E., Irby, J., Lin, Y., Parker, R. R., Rice, J. E., Shiraiwa, S., Walk, J. R., Wukitch, S. J., and Xu, P. Improved confinement in high-density H-modes via modification of the plasma boundary with lower hybrid wavesa). United States: N. p., 2015.
Web. doi:10.1063/1.4920964.
Terry, J. L., Reinke, M. L., Hughes, J. W., LaBombard, B., Theiler, C., Wallace, G. M., Baek, S. G., Brunner, D., Churchill, R. M., Edlund, E., Ennever, P., Faust, I., Golfinopoulos, T., Greenwald, M., Hubbard, A. E., Irby, J., Lin, Y., Parker, R. R., Rice, J. E., Shiraiwa, S., Walk, J. R., Wukitch, S. J., & Xu, P. Improved confinement in high-density H-modes via modification of the plasma boundary with lower hybrid wavesa). United States. https://doi.org/10.1063/1.4920964
Terry, J. L., Reinke, M. L., Hughes, J. W., LaBombard, B., Theiler, C., Wallace, G. M., Baek, S. G., Brunner, D., Churchill, R. M., Edlund, E., Ennever, P., Faust, I., Golfinopoulos, T., Greenwald, M., Hubbard, A. E., Irby, J., Lin, Y., Parker, R. R., Rice, J. E., Shiraiwa, S., Walk, J. R., Wukitch, S. J., and Xu, P. 2015.
"Improved confinement in high-density H-modes via modification of the plasma boundary with lower hybrid wavesa)". United States. https://doi.org/10.1063/1.4920964. https://www.osti.gov/servlets/purl/1547003.
@article{osti_1547003,
title = {Improved confinement in high-density H-modes via modification of the plasma boundary with lower hybrid wavesa)},
author = {Terry, J. L. and Reinke, M. L. and Hughes, J. W. and LaBombard, B. and Theiler, C. and Wallace, G. M. and Baek, S. G. and Brunner, D. and Churchill, R. M. and Edlund, E. and Ennever, P. and Faust, I. and Golfinopoulos, T. and Greenwald, M. and Hubbard, A. E. and Irby, J. and Lin, Y. and Parker, R. R. and Rice, J. E. and Shiraiwa, S. and Walk, J. R. and Wukitch, S. J. and Xu, P.},
abstractNote = {Injecting Lower Hybrid Range of Frequency (LHRF) waves into Alcator C-Mod's high-density H-mode plasmas has led to enhanced global energy confinement by increasing pedestal temperature and pressure gradients, decreasing the separatrix density, modifying the pedestal radial electric field and rotation, and decreasing edge turbulence. These experiments imply that edge LHRF can be used as an actuator to increase energy confinement via modification of boundary quantities. H98-factor increases of up to ~35% (e.g., H98 from 0.75 to 1.0) are seen when moderate amounts of LH power (PLH/Ptot~0.15) are applied to H-modes of densities $\overline{n}$e~3 × 1020 m–3, corresponding to values ~0.5 of the Greenwald density. However, the magnitude of the improvement is reduced if the confinement quality of the target H-mode plasma is already good (i.e., H98target ~ 1). Ray-tracing modeling and accessibility calculations for the LH waves indicate that they do not penetrate to the core. The LHRF power appears to be deposited in plasma boundary region, with a large fraction of the injected power increment appearing promptly on the outer divertor target. There is no evidence that the LH waves are driving current in these plasmas. The LHRF-actuated improvements are well correlated with suppressed pedestal density fluctuations in the 100–300 kHz range. Additionally, there is a correlation between the improved confinement and a drop in separatrix density, a correlation that is consistent with previous H-mode results with no LHRF.},
doi = {10.1063/1.4920964},
url = {https://www.osti.gov/biblio/1547003},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 22,
place = {United States},
year = {Mon May 18 00:00:00 EDT 2015},
month = {Mon May 18 00:00:00 EDT 2015}
}
Web of Science
Works referenced in this record:
High power lower hybrid current drive experiments in the Tore Supra tokamak
journal, November 2001
- Peysson, Y.; Team, Tore Supra
- Nuclear Fusion, Vol. 41, Issue 11
Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature
journal, June 2014
- Theiler, C.; Churchill, R. M.; Lipschultz, B.
- Nuclear Fusion, Vol. 54, Issue 8
Critical gradients and plasma flows in the edge plasma of Alcator C-Mod
journal, May 2008
- LaBombard, B.; Hughes, J. W.; Smick, N.
- Physics of Plasmas, Vol. 15, Issue 5
Modification of H-mode pedestal structure with lower hybrid waves on Alcator C-Mod
journal, May 2010
- Hughes, J. W.; Hubbard, A. E.; Wallace, G.
- Nuclear Fusion, Vol. 50, Issue 6
Density limits in toroidal plasmas
journal, July 2002
- Greenwald, Martin
- Plasma Physics and Controlled Fusion, Vol. 44, Issue 8
Effect of N2, Ne and Ar seeding on Alcator C-Mod H-mode confinement
journal, August 2011
- Reinke, M. L.; Hughes, J. W.; Loarte, A.
- Journal of Nuclear Materials, Vol. 415, Issue 1
Power requirements for superior H-mode confinement on Alcator C-Mod: experiments in support of ITER
journal, June 2011
- Hughes, J. W.; Loarte, A.; Reinke, M. L.
- Nuclear Fusion, Vol. 51, Issue 8
Lower hybrid heating and current drive on the Alcator C-Mod tokamak
journal, September 2009
- Wilson, J. R.; Parker, R.; Bitter, M.
- Nuclear Fusion, Vol. 49, Issue 11
Lithium coatings on NSTX plasma facing components and its effects on boundary control, core plasma performance, and operation
journal, November 2010
- Kugel, H. W.; Bell, M. G.; Schneider, H.
- Fusion Engineering and Design, Vol. 85, Issue 6
Modification of Current Profile, Toroidal Rotation and Pedestal by Lower Hybrid Waves in Alcator C-Mod
conference, January 2009
- Parker, R.; Bonoli, P. T.; Meneghini, O.
- RADIO FREQUENCY POWER IN PLASMAS: Proceedings of the 18th Topical Conference, AIP Conference Proceedings
Progress in quantifying the edge physics of the H mode regime in DIII-D
journal, December 2001
- Groebner, R. J.; Baker, D. R.; Burrell, K. H.
- Nuclear Fusion, Vol. 41, Issue 12
New insights on boundary plasma turbulence and the quasi-coherent mode in Alcator C-Mod using a Mirror Langmuir Probe
journal, May 2014
- LaBombard, B.; Golfinopoulos, T.; Terry, J. L.
- Physics of Plasmas, Vol. 21, Issue 5
Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod plasmas
journal, May 2009
- McDermott, R. M.; Lipschultz, B.; Hughes, J. W.
- Physics of Plasmas, Vol. 16, Issue 5
Effects of LHRF on toroidal rotation in Alcator C-Mod plasmas
journal, August 2013
- Rice, J. E.; Podpaly, Y. A.; Reinke, M. L.
- Nuclear Fusion, Vol. 53, Issue 9
High confinement/high radiated power H-mode experiments in Alcator C-Mod and consequences for International Thermonuclear Experimental Reactor (ITER) Q DT = 10 operation
journal, May 2011
- Loarte, A.; Hughes, J. W.; Reinke, M. L.
- Physics of Plasmas, Vol. 18, Issue 5
Chapter 2: Plasma confinement and transport
journal, December 1999
- Transport, ITER Physics Expert Group on Confin; Database, ITER Physics Expert Group on Confin; Editors, ITER Physics Basis
- Nuclear Fusion, Vol. 39, Issue 12
Design, and initial experiment results of a novel LH launcher on Alcator C-Mod
journal, September 2011
- Shiraiwa, S.; Meneghini, O.; Parker, R. R.
- Nuclear Fusion, Vol. 51, Issue 10
Recent Results of LHCD Experiments in EAST
journal, April 2011
- Ding, Bojiang; Kong, Erhua; Li, Miaohui
- Plasma Science and Technology, Vol. 13, Issue 2
Far-infrared polarimetry diagnostic for measurement of internal magnetic field dynamics and fluctuations in the C-MOD Tokamak (invited)
journal, October 2012
- Bergerson, W. F.; Xu, P.; Irby, J. H.
- Review of Scientific Instruments, Vol. 83, Issue 10
Development of the gas puff charge exchange recombination spectroscopy (GP-CXRS) technique for ion measurements in the plasma edge
journal, September 2013
- Churchill, R. M.; Theiler, C.; Lipschultz, B.
- Review of Scientific Instruments, Vol. 84, Issue 9
Variation of edge gradients with heat flux across L-H and H-L transitions in Alcator C-Mod
journal, April 2002
- Hubbard, A. E.; Carreras, B. A.; Boivin, R. L.
- Plasma Physics and Controlled Fusion, Vol. 44, Issue 5A
Operation of Alcator C-Mod with high-Z plasma facing components and implications
journal, May 2006
- Lipschultz, B.; Lin, Y.; Reinke, M. L.
- Physics of Plasmas, Vol. 13, Issue 5
Divertor IR thermography on Alcator C-Mod
journal, October 2010
- Terry, J. L.; LaBombard, B.; Brunner, D.
- Review of Scientific Instruments, Vol. 81, Issue 10
Edge energy transport barrier and turbulence in the I-mode regime on Alcator C-Mod
journal, May 2011
- Hubbard, A. E.; Whyte, D. G.; Churchill, R. M.
- Physics of Plasmas, Vol. 18, Issue 5
Edge profile stiffness and insensitivity of the density pedestal to neutral fuelling in Alcator C-Mod edge transport barriers
journal, August 2007
- Hughes, J. W.; LaBombard, B.; Terry, J.
- Nuclear Fusion, Vol. 47, Issue 8
Wall conditioning experiments on TFTR using impurity pellet injection
journal, November 1994
- Strachan, J. D.; Mansfield, D. K.; Bell, M. G.
- Journal of Nuclear Materials, Vol. 217, Issue 1-2
Hard x-ray diagnostic for lower hybrid experiments on Alcator C-Mod
journal, October 2006
- Liptac, J.; Parker, R.; Tang, V.
- Review of Scientific Instruments, Vol. 77, Issue 10
Power requirement for accessing the H-mode in ITER
journal, July 2008
- Martin, Y. R.; Takizuka, T.; Group, the ITPA CDBM H-mode Threshold Data
- Journal of Physics: Conference Series, Vol. 123
Magnetic Topology Changes Induced by Lower Hybrid Waves and their Profound Effect on Edge-Localized Modes in the EAST Tokamak
journal, June 2013
- Liang, Y.; Gong, X. Z.; Gan, K. F.
- Physical Review Letters, Vol. 110, Issue 23
Imaging of molybdenum erosion and thermography at visible wavelengths in Alcator C-Mod ICRH and LHCD discharges
journal, November 2013
- James, A. N.; Brunner, D.; Labombard, B.
- Plasma Physics and Controlled Fusion, Vol. 55, Issue 12