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Goumiri IR, Rowley CW, Sabbagh SA, Gates DA, Boyer MD, Gerhardt SP, Kolemen E, Menard JE. Simultaneous feedback control of plasma rotation and stored energy on NSTX-U using neoclassical toroidal viscosity and neutral beam injection. Phys Plasmas 2017; 24:056101. [PMID: 28435207 PMCID: PMC5375958 DOI: 10.1063/1.4976853] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 11/21/2016] [Indexed: 06/07/2023]
Abstract
A model-based feedback system is presented enabling the simultaneous control of the stored energy through βn and the toroidal rotation profile of the plasma in National Spherical Torus eXperiment Upgrade device. Actuation is obtained using the momentum from six injected neutral beams and the neoclassical toroidal viscosity generated by applying three-dimensional magnetic fields. Based on a model of the momentum diffusion and torque balance, a feedback controller is designed and tested in closed-loop simulations using TRANSP, a time dependent transport analysis code, in predictive mode. Promising results for the ongoing experimental implementation of controllers are obtained.
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Affiliation(s)
- I R Goumiri
- Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - C W Rowley
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - S A Sabbagh
- Department of Applied Physics, Columbia University, New York, New York 10027, USA
| | - D A Gates
- Princeton Plasma Physics Laboratory, Princeton, New Jersrey 08544, USA
| | - M D Boyer
- Princeton Plasma Physics Laboratory, Princeton, New Jersrey 08544, USA
| | - S P Gerhardt
- Princeton Plasma Physics Laboratory, Princeton, New Jersrey 08544, USA
| | - E Kolemen
- Princeton Plasma Physics Laboratory, Princeton, New Jersrey 08544, USA
| | - J E Menard
- Princeton Plasma Physics Laboratory, Princeton, New Jersrey 08544, USA
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2
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Yang HL, Kwak JG, Oh YK, Park KR, Kim WC, Lee SG, Kim JY, Bae YS, Park YM, Kim HK, Chu Y, Park MK, Kim JS, In SR, Joung SH, Choe WH, Park HK, Hwang YS, Na YS, Park JG, Ahn JW, Park YS, Kwon M, Leuer JA, Eidietis NW, Hyatt AW, Walker M, Gorelov Y, Lohr J, Mueller D, Grisham LR, Sabbagh SA, Watanabe K, Inoue T, Sakamoto K, Oda Y, Kajiwara K, Ellis R, Hosea J, Delpech L, Hoang TT, Litaudon X, Namkung W, Cho MH. Overview of KSTAR Results in Phase-I Operation. Fusion Science and Technology 2017. [DOI: 10.13182/fst13-a19130] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- H. L. Yang
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - J. G. Kwak
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - Y. K. Oh
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - K. R. Park
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - W. C. Kim
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - S. G. Lee
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - J. Y. Kim
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - Y. S. Bae
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - Y. M. Park
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - H. K. Kim
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - Y. Chu
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - M. K. Park
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - J. S. Kim
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - S. R. In
- Korea Atomic Energy Research Insititute, Daeduk-Daero 989-111, Yuseong-gu, Daejeon, 305-353, Korea
| | - S. H. Joung
- Korea Atomic Energy Research Insititute, Daeduk-Daero 989-111, Yuseong-gu, Daejeon, 305-353, Korea
| | - W. H. Choe
- Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701, Korea
| | - H. K. Park
- Pohang Univ. of Science and Technology, 77 Cheongam-ro, Nam-gu, Pohang, Gyungbuk, 790-784, Korea
| | - Y. S. Hwang
- Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-742, Korea
| | - Y. S. Na
- Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-742, Korea
| | - J. G. Park
- Princeton Plasma Physics Lab., P.O. Box 451 Princetorn, NJ 08543-0451, USA
| | - J. W. Ahn
- Oak Ridge National Lab., 1 Bethal Valley Rd, OakRidge, TN37831, USA
| | - Y. S. Park
- Columbia Univ., James Forrestal Campus (EWA 244), P.O. Box 451, Princeton, NJ 08543, USA
| | - M. Kwon
- National Fusion Research Institute, 113 Gwahangno, Yusung-Gu, Daejeon, 305-333, Korea
| | - J. A. Leuer
- General Atomics, 3550 General Atomics Court, San Diego, CA 92121, USA
| | - N. W. Eidietis
- General Atomics, 3550 General Atomics Court, San Diego, CA 92121, USA
| | - A. W. Hyatt
- General Atomics, 3550 General Atomics Court, San Diego, CA 92121, USA
| | - M. Walker
- General Atomics, 3550 General Atomics Court, San Diego, CA 92121, USA
| | - Y. Gorelov
- General Atomics, 3550 General Atomics Court, San Diego, CA 92121, USA
| | - J. Lohr
- General Atomics, 3550 General Atomics Court, San Diego, CA 92121, USA
| | - D. Mueller
- Princeton Plasma Physics Lab., P.O. Box 451 Princetorn, NJ 08543-0451, USA
| | - L. R. Grisham
- Princeton Plasma Physics Lab., P.O. Box 451 Princetorn, NJ 08543-0451, USA
| | - S. A. Sabbagh
- Columbia Univ., James Forrestal Campus (EWA 244), P.O. Box 451, Princeton, NJ 08543, USA
| | - K. Watanabe
- Japan Atomic Energy Agency, 801-1 Mukoyama, Naka-city, Ibaraki-ken, 311-0193, Japan
| | - T. Inoue
- Japan Atomic Energy Agency, 801-1 Mukoyama, Naka-city, Ibaraki-ken, 311-0193, Japan
| | - K. Sakamoto
- Japan Atomic Energy Agency, 801-1 Mukoyama, Naka-city, Ibaraki-ken, 311-0193, Japan
| | - Y. Oda
- Japan Atomic Energy Agency, 801-1 Mukoyama, Naka-city, Ibaraki-ken, 311-0193, Japan
| | - K. Kajiwara
- Japan Atomic Energy Agency, 801-1 Mukoyama, Naka-city, Ibaraki-ken, 311-0193, Japan
| | - R. Ellis
- Princeton Plasma Physics Lab., P.O. Box 451 Princetorn, NJ 08543-0451, USA
| | - J. Hosea
- Princeton Plasma Physics Lab., P.O. Box 451 Princetorn, NJ 08543-0451, USA
| | - L. Delpech
- CEA, IFRM,13108 Saint-Paul-Lez-Durance, France
| | - T. T. Hoang
- CEA, IFRM,13108 Saint-Paul-Lez-Durance, France
| | - X. Litaudon
- CEA, IFRM,13108 Saint-Paul-Lez-Durance, France
| | - W. Namkung
- Pohang Univ. of Science and Technology, 77 Cheongam-ro, Nam-gu, Pohang, Gyungbuk, 790-784, Korea
| | - M. H. Cho
- Pohang Univ. of Science and Technology, 77 Cheongam-ro, Nam-gu, Pohang, Gyungbuk, 790-784, Korea
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3
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Liu Y, Sabbagh SA, Chapman IT, Gerasimov S, Gribov Y, Hender TC, Igochine V, Maraschek M, Matsunaga G, Okabayashi M, Strait EJ. Multimachine Data–Based Prediction of High-Frequency Sensor Signal Noise for Resistive Wall Mode Control in ITER. Fusion Science and Technology 2017. [DOI: 10.13182/fst15-207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Yueqiang Liu
- CCFE, Culham Science Centre, Abingdon, OX14 3DB, United Kingdom
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
- Chalmers University of Technology, Department of Earth and Space Science, SE-412 96 Gothenburg, Sweden
| | - S. A. Sabbagh
- Columbia University, Department of Applied Physics and Applied Mathematics, New York, New York 10027
| | - I. T. Chapman
- CCFE, Culham Science Centre, Abingdon, OX14 3DB, United Kingdom
| | - S. Gerasimov
- CCFE, Culham Science Centre, Abingdon, OX14 3DB, United Kingdom
| | - Y. Gribov
- ITER Organization, Route de Vinon sur Verdon, CS90046, 13067 St Paul Lez Durance Cedex, France
| | - T. C. Hender
- CCFE, Culham Science Centre, Abingdon, OX14 3DB, United Kingdom
| | - V. Igochine
- Max Planck Institute for Plasma Physics, Boltzmannstrasse 2, 85748 Garching, Germany
| | - M. Maraschek
- Max Planck Institute for Plasma Physics, Boltzmannstrasse 2, 85748 Garching, Germany
| | - G. Matsunaga
- Japan Atomic Energy Agency, 801-1, Mukouyama, Naka, Ibaraki 311-0193, Japan
| | - M. Okabayashi
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
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4
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Lee J, Yun GS, Lee JE, Kim M, Choi MJ, Lee W, Park HK, Domier CW, Luhmann NC, Sabbagh SA, Park YS, Lee SG, Bak JG. Toroidal mode number estimation of the edge-localized modes using the KSTAR 3-D electron cyclotron emission imaging system. Rev Sci Instrum 2014; 85:063505. [PMID: 24985817 DOI: 10.1063/1.4883180] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A new and more accurate technique is presented for determining the toroidal mode number n of edge-localized modes (ELMs) using two independent electron cyclotron emission imaging (ECEI) systems in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The technique involves the measurement of the poloidal spacing between adjacent ELM filaments, and of the pitch angle α* of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that α* is nearly constant and thus well-defined at the midplane edge. Estimates of n obtained using two ECEI systems agree well with n measured by the conventional technique employing an array of Mirnov coils.
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Affiliation(s)
- J Lee
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - G S Yun
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - J E Lee
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - M Kim
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - M J Choi
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - W Lee
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - H K Park
- Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea
| | - C W Domier
- University of California at Davis, Davis, California 95616, USA
| | - N C Luhmann
- University of California at Davis, Davis, California 95616, USA
| | - S A Sabbagh
- Columbia University, New York, New York 10027, USA
| | - Y S Park
- Columbia University, New York, New York 10027, USA
| | - S G Lee
- National Fusion Research Institute, Daejeon 305-333, South Korea
| | - J G Bak
- National Fusion Research Institute, Daejeon 305-333, South Korea
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5
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Maingi R, Kaye SM, Skinner CH, Boyle DP, Canik JM, Bell MG, Bell RE, Gray TK, Jaworski MA, Kaita R, Kugel HW, LeBlanc BP, Mansfield DK, Osborne TH, Sabbagh SA, Soukhanovskii VA. Continuous improvement of H-mode discharge performance with progressively increasing lithium coatings in the National Spherical Torus Experiment. Phys Rev Lett 2011; 107:145004. [PMID: 22107204 DOI: 10.1103/physrevlett.107.145004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Indexed: 05/31/2023]
Abstract
Lithium wall coatings have been shown to reduce recycling, improve energy confinement, and suppress edge localized modes in the National Spherical Torus Experiment. Here, we show that these effects depend continuously on the amount of predischarge lithium evaporation. We observed a nearly monotonic reduction in recycling, decrease in electron transport, and modification of the edge profiles and stability with increasing lithium. These correlations challenge basic expectations, given that even the smallest coatings exceeded that needed for a nominal thickness of the order of the implantation range.
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Affiliation(s)
- R Maingi
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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6
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Reimerdes H, Berkery JW, Lanctot MJ, Garofalo AM, Hanson JM, In Y, Okabayashi M, Sabbagh SA, Strait EJ. Evidence for the importance of trapped particle resonances for resistive wall mode stability in high beta tokamak plasmas. Phys Rev Lett 2011; 106:215002. [PMID: 21699306 DOI: 10.1103/physrevlett.106.215002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Indexed: 05/31/2023]
Abstract
Active measurements of the plasma stability in tokamak plasmas reveal the importance of kinetic resonances for resistive wall mode stability. The rotation dependence of the magnetic plasma response to externally applied quasistatic n=1 magnetic fields clearly shows the signatures of an interaction between the resistive wall mode and the precession and bounce motions of trapped thermal ions, as predicted by a perturbative model of plasma stability including kinetic effects. The identification of the stabilization mechanism is an essential step towards quantitative predictions for the prospects of "passive" resistive wall mode stabilization, i.e., without the use of an "active" feedback system, in fusion-alpha heated plasmas.
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Affiliation(s)
- H Reimerdes
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027-6902, USA
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7
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Berkery JW, Sabbagh SA, Betti R, Bell RE, Gerhardt SP, LeBlanc BP, Yuh H. Effect of collisionality on kinetic stability of the resistive wall mode. Phys Rev Lett 2011; 106:075004. [PMID: 21405523 DOI: 10.1103/physrevlett.106.075004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Indexed: 05/30/2023]
Abstract
The impact of collisionless, energy-independent, and energy-dependent collisionality models on the kinetic stability of the resistive wall mode is examined for high pressure plasmas in the National Spherical Torus Experiment. Future devices will have decreased collisionality, which previous stability models predict to be universally destabilizing. In contrast, in kinetic theory reduced ion-ion collisions are shown to lead to a significant stability increase when the plasma rotation frequency is in a stabilizing resonance with the ion precession drift frequency. When the plasma is in a reduced stability state with rotation in between resonances, collisionality will have little effect on stability.
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Affiliation(s)
- J W Berkery
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
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8
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Maingi R, Bell RE, Canik JM, Gerhardt SP, Kaye SM, Leblanc BP, Osborne TH, Bell MG, Fredrickson ED, Lee KC, Menard JE, Park JK, Sabbagh SA. Triggered confinement enhancement and pedestal expansion in high-confinement-mode discharges in the national spherical torus experiment. Phys Rev Lett 2010; 105:135004. [PMID: 21230781 DOI: 10.1103/physrevlett.105.135004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2010] [Indexed: 05/30/2023]
Abstract
We report observation of a new high performance regime in discharges in the National Spherical Torus Experiment, where the H mode edge "pedestal" temperature doubles and the energy confinement increases by 50%. The spontaneous transition is triggered by a large edge-localized mode, either natural or externally triggered by 3D fields. The transport barrier grows inward from the edge, with a doubling of both the pedestal pressure width and the spatial extent of steep radial electric field shear. The dynamics suggest that 3D fields could be applied to reduce edge transport in fusion devices.
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Affiliation(s)
- R Maingi
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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9
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Canik JM, Maingi R, Evans TE, Bell RE, Gerhardt SP, Leblanc BP, Manickam J, Menard JE, Osborne TH, Park JK, Paul SF, Snyder PB, Sabbagh SA, Kugel HW, Unterberg EA. On demand triggering of edge localized instabilities using external nonaxisymmetric magnetic perturbations in toroidal plasmas. Phys Rev Lett 2010; 104:045001. [PMID: 20366719 DOI: 10.1103/physrevlett.104.045001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2009] [Indexed: 05/29/2023]
Abstract
The application of nonaxisymmetric magnetic fields is shown to destabilize edge-localized modes (ELMs) during otherwise ELM-free periods of discharges in the National Spherical Torus Experiment (NSTX). Profile analysis shows the applied fields increased the temperature and pressure gradients, decreasing edge stability. This robust effect was exploited for a new form of ELM control: the triggering of ELMs at will in high performance H mode plasmas enabled by lithium conditioning, yielding high time-averaged energy confinement with reduced core impurity density and radiated power.
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Affiliation(s)
- J M Canik
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
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10
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Berkery JW, Sabbagh SA, Betti R, Hu B, Bell RE, Gerhardt SP, Manickam J, Tritz K. Resistive wall mode instability at intermediate plasma rotation. Phys Rev Lett 2010; 104:035003. [PMID: 20366652 DOI: 10.1103/physrevlett.104.035003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Indexed: 05/29/2023]
Abstract
Experimental observation of resistive wall mode (RWM) instability in the National Spherical Torus Experiment (NSTX) at plasma rotation levels intermediate to the ion precession drift and ion bounce frequencies suggests that low critical rotation threshold models are insufficient. Kinetic modifications to the ideal stability criterion yield a more complex relationship between plasma rotation and RWM stability. Good agreement is found between an experimental RWM instability at intermediate plasma rotation and the RWM marginal point calculated with kinetic effects included, by the MISK code. By self-similarly scaling the experimental plasma rotation profile and the collisionality in the calculation, resonances of the mode with the precession drift and bounce frequencies are explored. Experimentally, RWMs go unstable when the plasma rotation is between the stabilizing precession drift and bounce resonances.
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Affiliation(s)
- J W Berkery
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
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11
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Maingi R, Osborne TH, Leblanc BP, Bell RE, Manickam J, Snyder PB, Menard JE, Mansfield DK, Kugel HW, Kaita R, Gerhardt SP, Sabbagh SA, Kelly FA. Edge-localized-mode suppression through density-profile modification with lithium-wall coatings in the National Spherical Torus Experiment. Phys Rev Lett 2009; 103:075001. [PMID: 19792649 DOI: 10.1103/physrevlett.103.075001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Indexed: 05/28/2023]
Abstract
Reduction or elimination of edge localized modes (ELMs) while maintaining high confinement is essential for future fusion devices, e.g., the ITER. An ELM-free regime was recently obtained in the National Spherical Torus Experiment, following lithium (Li) evaporation onto the plasma-facing components. Edge stability calculations indicate that the pre-Li discharges were unstable to low-n peeling or ballooning modes, while broader pressure profiles stabilized the post-Li discharges. Normalized energy confinement increased by 50% post Li, with no sign of ELMs up to the global stability limit.
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Affiliation(s)
- R Maingi
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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12
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Diem SJ, Taylor G, Caughman JB, Efthimion PC, Kugel H, LeBlanc BP, Phillips CK, Preinhaelter J, Sabbagh SA, Urban J. Collisional damping of electron bernstein waves and its mitigation by evaporated lithium conditioning in spherical-tokamak plasmas. Phys Rev Lett 2009; 103:015002. [PMID: 19659154 DOI: 10.1103/physrevlett.103.015002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Indexed: 05/28/2023]
Abstract
The first experimental verification of electron Bernstein wave (EBW) collisional damping, and its mitigation by evaporated Li conditioning, in an overdense spherical-tokamak plasma has been observed in the National Spherical Torus Experiment (NSTX). Initial measurements of EBW emission, coupled from NSTX plasmas via double-mode conversion to O-mode waves, exhibited <10% transmission efficiencies. Simulations show 80% of the EBW energy is dissipated by collisions in the edge plasma. Li conditioning reduced the edge collision frequency by a factor of 3 and increased the fundamental EBW transmission to 60%.
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Affiliation(s)
- S J Diem
- Oak Ridge National Laboratory, Oak Ridge 37831, Tennessee, USA
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13
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Diem SJ, Taylor G, Caughman JB, Efthimion P, Kugel H, LeBlanc BP, Preinhaelter J, Sabbagh SA, Urban J, Wilgen J. Electron Bernstein wave emission based diagnostic on National Spherical Torus Experiment (invited). Rev Sci Instrum 2008; 79:10F101. [PMID: 19044588 DOI: 10.1063/1.2953592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
National Spherical Torus Experiment (NSTX) is a spherical tokamak (ST) that operates with n(e) up to 10(20) m(-3) and B(T) less than 0.6 T, cutting off low harmonic electron cyclotron (EC) emission widely used for T(e) measurements on conventional aspect ratio tokamaks. The electron Bernstein wave (EBW) can propagate in ST plasmas and is emitted at EC harmonics. These properties suggest thermal EBW emission (EBE) may be used for local T(e) measurements in the ST. Practically, a robust T(e)(R,t) EBE diagnostic requires EBW transmission efficiencies of >90% for a wide range of plasma conditions. EBW emission and coupling physics were studied on NSTX with an obliquely viewing EBW to O-mode (B-X-O) diagnostic with two remotely steered antennas, coupled to absolutely calibrated radiometers. While T(e)(R,t) measurements with EBW emission on NSTX were possible, they were challenged by several issues. Rapid fluctuations in edge n(e) scale length resulted in >20% changes in the low harmonic B-X-O transmission efficiency. Also, B-X-O transmission efficiency during H modes was observed to decay by a factor of 5-10 to less than a few percent. The B-X-O transmission behavior during H modes was reproduced by EBE simulations that predict that EBW collisional damping can significantly reduce emission when T(e)<30 eV inside the B-X-O mode conversion (MC) layer. Initial edge lithium conditioning experiments during H modes have shown that evaporated lithium can increase T(e) inside the B-X-O MC layer, significantly increasing B-X-O transmission.
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Affiliation(s)
- S J Diem
- Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543, USA
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14
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Solomon WM, Kaye SM, Bell RE, Leblanc BP, Menard JE, Rewoldt G, Wang W, Levinton FM, Yuh H, Sabbagh SA. Momentum-transport studies in high E x B shear plasmas in the National Spherical Torus Experiment. Phys Rev Lett 2008; 101:065004. [PMID: 18764464 DOI: 10.1103/physrevlett.101.065004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Indexed: 05/26/2023]
Abstract
Experiments have been conducted at the National Sperical Torus Experiment (NSTX) to study both steady state and perturbative momentum transport. These studies are unique in their parameter space under investigation, where the low aspect ratio of NSTX results in rapid plasma rotation with ExB shearing rates high enough to suppress low-k turbulence. In some cases, the ratio of momentum to energy confinement time is found to exceed five. Momentum pinch velocities of order 10-40 m/s are inferred from the measured angular momentum flux evolution after nonresonant magnetic perturbations are applied to brake the plasma.
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Affiliation(s)
- W M Solomon
- Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA.
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15
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Menard JE, Bell RE, Gates DA, Kaye SM, LeBlanc BP, Levinton FM, Medley SS, Sabbagh SA, Stutman D, Tritz K, Yuh H. Observation of instability-induced current redistribution in a spherical-torus plasma. Phys Rev Lett 2006; 97:095002. [PMID: 17026371 DOI: 10.1103/physrevlett.97.095002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2006] [Indexed: 05/12/2023]
Abstract
A motional Stark effect diagnostic has been utilized to reconstruct the parallel current density profile in a spherical-torus plasma for the first time. The measured current profile compares favorably with neoclassical theory when no large-scale magnetohydrodynamic instabilities are present in the plasma. However, a current profile anomaly is observed during saturated interchange-type instability activity. This apparent anomaly can be explained by redistribution of neutral beam injection current drive and represents the first observation of interchange-type instabilities causing such redistribution. The associated current profile modifications contribute to sustaining the central safety factor above unity for over five resistive diffusion times, and similar processes may contribute to improved operational scenarios proposed for ITER.
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Affiliation(s)
- J E Menard
- Princeton Plasma Physics Laboratory, Princeton, New Jersey, USA
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16
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Sabbagh SA, Bell RE, Menard JE, Gates DA, Sontag AC, Bialek JM, LeBlanc BP, Levinton FM, Tritz K, Yuh H. Active stabilization of the resistive-wall mode in high-beta, low-rotation plasmas. Phys Rev Lett 2006; 97:045004. [PMID: 16907583 DOI: 10.1103/physrevlett.97.045004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2006] [Indexed: 05/11/2023]
Abstract
The resistive-wall mode is actively stabilized in the National Spherical Torus Experiment in high-beta plasmas rotating significantly below the critical rotation speed for passive stability and in the range predicted for the International Thermonuclear Experimental Reactor. Variation of feedback stabilization parameters shows mode excitation or suppression. Stabilization of toroidal mode number unity did not lead to instability of toroidal mode number two. The mode can become unstable by deforming poloidally, an important consideration for stabilization system design.
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Affiliation(s)
- S A Sabbagh
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
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17
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Zhu W, Sabbagh SA, Bell RE, Bialek JM, Bell MG, LeBlanc BP, Kaye SM, Levinton FM, Menard JE, Shaing KC, Sontag AC, Yuh H. Observation of plasma toroidal-momentum dissipation by neoclassical toroidal viscosity. Phys Rev Lett 2006; 96:225002. [PMID: 16803317 DOI: 10.1103/physrevlett.96.225002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Indexed: 05/10/2023]
Abstract
Dissipation of plasma toroidal angular momentum is observed in the National Spherical Torus Experiment due to applied nonaxisymmetric magnetic fields and their plasma-induced increase by resonant field amplification and resistive wall mode destabilization. The measured decrease of the plasma toroidal angular momentum profile is compared to calculations of nonresonant drag torque based on the theory of neoclassical toroidal viscosity. Quantitative agreement between experiment and theory is found when the effect of toroidally trapped particles is included.
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Affiliation(s)
- W Zhu
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
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18
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Maingi R, Bell MG, Bell RE, Bush CE, Fredrickson ED, Gates DA, Kaye SM, Kugel HW, LeBlanc BP, Menard JE, Mueller D, Sabbagh SA, Stutman D, Taylor G, Johnson DW, Kaita R, Maqueda RJ, Ono M, Paoletti F, Paul SF, Peng YKM, Roquemore AL, Skinner CH, Soukhanovskii VA, Synakowski EJ. Characteristics of the first H-mode discharges in the national spherical torus experiment. Phys Rev Lett 2002; 88:035003. [PMID: 11801067 DOI: 10.1103/physrevlett.88.035003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2001] [Indexed: 05/23/2023]
Abstract
We report observations of the first low-to-high ( L-H) confinement mode transitions in the National Spherical Torus Experiment. The H-mode energy confinement time increased over reference discharges transiently by 100-200%, as high as approximately 100 ms. This confinement time is approximately 2 times higher than predicted by a multimachine scaling. Thus the confinement time of spherical tori has been extended to a record high value, leading to an eventual revision of confinement scalings. Finally, the power threshold for H-mode access is >10x higher than predicted by an international scaling from conventional aspect-ratio tokamaks, which could lead to new understanding of H-mode transition dynamics.
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Affiliation(s)
- R Maingi
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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19
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Chang Z, Park W, Fredrickson ED, Batha SH, Bell MG, Bell R, Budny RV, Bush CE, Janos A, Levinton FM, McGuire KM, Park H, Sabbagh SA, Schmidt GL, Scott SD, Synakowski EJ, Takahashi H, Taylor G, Zarnstorff MC. Off-Axis Sawteeth and Double-Tearing Reconnectionin Reversed Magnetic Shear Plasmas in TFTR. Phys Rev Lett 1996; 77:3553-3556. [PMID: 10062249 DOI: 10.1103/physrevlett.77.3553] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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20
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Lazarus EA, Navratil GA, Greenfield CM, Strait EJ, Austin ME, Burrell KH, Casper TA, Baker DR, DeBoo JC, Doyle EJ, Durst R, Ferron JR, Forest CB, Gohil P, Groebner RJ, Heidbrink WW, Hong R, Houlberg WA, Howald AW, Hsieh C, Hyatt AW, Jackson GL, Kim J, Lao LL, Lasnier CJ, Leonard AW, Lohr J, Maingi R, Miller RL, Murakami M, Osborne TH, Perkins LJ, Petty CC, Rettig CL, Rhodes TL, Rice BW, Sabbagh SA, Schissel DP, Scoville JT, Snider RT, Staebler GM, Stallard BW, Stambaugh RD, Stockdale RE, Taylor PL, Thomas DM, Turnbull AD, Wade MR, Wood R, Whyte D. Higher Fusion Power Gain with Current and Pressure Profile Control in Strongly Shaped DIII-D Tokamak Plasmas. Phys Rev Lett 1996; 77:2714-2717. [PMID: 10062027 DOI: 10.1103/physrevlett.77.2714] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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21
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Levinton FM, Zarnstorff MC, Batha SH, Bell M, Bell RE, Budny RV, Bush C, Chang Z, Fredrickson E, Janos A, Manickam J, Ramsey A, Sabbagh SA, Schmidt GL, Synakowski EJ, Taylor G. Improved confinement with reversed magnetic shear in TFTR. Phys Rev Lett 1995; 75:4417-4420. [PMID: 10059903 DOI: 10.1103/physrevlett.75.4417] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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22
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Nagayama Y, Yamada M, Sabbagh SA, Fredrickson ED, Manickam J, Bell M, Budny RV, Cavallo A, Janos AC, Mauel ME, McGuire KM, Navratil GA, Taylor G. Investigation of ballooning modes in high poloidal beta plasmas in the Tokamak Fusion Test Reactor*. ACTA ACUST UNITED AC 1993. [DOI: 10.1063/1.860692] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Nagayama Y, Sabbagh SA, Manickam J, Fredrickson ED, Bell M, Budny RV, Cavallo A, Janos AC, Mauel ME, McGuire KM, Navratil GA, Taylor G, Yamada M. Observation of ballooning modes in high-temperature tokamak plasmas. Phys Rev Lett 1992; 69:2376-2379. [PMID: 10046469 DOI: 10.1103/physrevlett.69.2376] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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24
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Jassby DL, Barnes CW, Bell MG, Bitter M, Boivin R, Bretz NL, Budny RV, Bush CE, Dylla HF, Efthimion PC, Fredrickson ED, Hawryluk RJ, Hill KW, Hosea J, Hsuan H, Janos AC, Jobes FC, Johnson DW, Johnson LC, Kamperschroer J, Kieras‐Phillips C, Kilpatrick SJ, LaMarche PH, LeBlanc B, Mansfield DK, Marmar ES, McCune DC, McGuire KM, Meade DM, Medley SS, Mikkelsen DR, Mueller D, Owens DK, Park HK, Paul SF, Pitcher S, Ramsey AT, Redi MH, Sabbagh SA, Scott SD, Snipes J, Stevens J, Strachan JD, Stratton BC, Synakowski EJ, Taylor G, Terry JL, Timberlake JR, Towner HH, Ulrickson M, von Goeler S, Wieland RM, Williams M, Wilson JR, Wong K, Young KM, Zarnstorff MC, Zweben SJ. High‐Qplasmas in the TFTR tokamak. ACTA ACUST UNITED AC 1991. [DOI: 10.1063/1.859988] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Nasrat HA, Ardawi MS, Sabbagh SA. Loss of growth hormone responsiveness to normal physiological stimuli during pregnancy. Gynecol Obstet Invest 1991; 32:148-52. [PMID: 1756993 DOI: 10.1159/000293017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The response of pituitary GH to acute hyperglycaemia induced by 75 g oral glucose load in 73 pregnant women at various stages of gestation was examined. According to the age of gestation, patients were grouped into three groups: less than 20 weeks, between 20-30 and more than 30 weeks. Plasma glucose, GH and C-peptide were measured at fasting and then at 30, 60, 120 and 180 min following the glucose load. There was a significant increase in plasma GH concentration with weeks of gestation. The results also showed a loss of the normal physiological suppressive effects of hyperglycaemia on GH secretion in tests performed after 20 weeks of gestation. Only in tests performed before 20 weeks, there was a significant negative correlation between plasma glucose and GH values. These findings are consistent with recent reports suggesting an almost complete suppression of pituitary GH secretion by a placental variant of GH. These changes in the dynamics of GH secretion suggest that, in pregnancy, GH plays a more significant role than was previously thought.
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Affiliation(s)
- H A Nasrat
- Department of Obstetrics and Gynaecology, King Abdulaziz University Hospital, Jeddah, Saudi Arabia
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Abstract
A 75 g oral glucose tolerance test (OGTT) was performed on 135 high-risk pregnant patients. When the current World Health Organization (WHO) criteria for the diagnosis of gestational-glucose tolerance were applied, 88 patients were considered normal, 11 had gestational diabetes, and 36 patients had impaired-glucose tolerance, respectively. The plasma glucose, insulin, and C-peptide levels during the OGTT were further studied in the 88 patients (who had normal results). Two metabolically distinct groups were identified; a group (n = 53) with a 2-hour plasma glucose less than or equal to 6.6 mmol/L (118.8 mg/dL), had a normal insulin and C-peptide pattern, and a second group (n = 35) who had 2-hour plasma glucose greater than 6.6 mmol/L displayed a glycemic, insulin, and C-peptide pattern similar to that of patients with gestational diabetes mellitus. The risks of macrosomic babies and operative delivery were significantly greater in the latter group. These results suggest that in our pregnant population, a group of patients with impaired glucose tolerance will be under-diagnosed using the current WHO criteria. Based on our results new criteria for gestational glucose intolerance are suggested for our population.
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Affiliation(s)
- H A Nasrat
- Department of Obstetrics and Gynecology, King Abdulaziz Univeristy Hospital, Jeddah, Saudi Arabia
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