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Physics and performance of the I-mode regime over an expanded operating space on Alcator C-Mod.

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Title: Physics and performance of the I-mode regime over an expanded operating space on Alcator C-Mod.
Authors: A.E. Hubbard1 hubbard@psfc.mit.edu, S.-G. Baek1, D. Brunner1, A.J. Creely1, I. Cziegler2, E. Edlund1, J.W. Hughes1, B. LaBombard1, Y. Lin1, Z. Liu3,4, E.S. Marmar1, M.L. Reinke5, J.E. Rice1, B. Sorbom1, C. Sung6, J. Terry1, C. Theiler7, E.A. Tolman1, J.R. Walk1, A.E. White1
Source: Nuclear Fusion. Dec2017, Vol. 57 Issue 12, p1-1. 1p.
Subjects: Tokamaks, Plasma confinement, Plasma temperature, Particle range (Nuclear physics), Plasma density, Heat flux
Abstract: New results on the I-mode regime of operation on the Alcator C-Mod tokamak are reported. This ELM-free regime features high energy confinement and a steep temperature pedestal, while particle confinement remains at L-mode levels, giving stationary density and avoiding impurity accumulation. I-mode has now been obtained over nearly all of the magnetic fields and currents possible in this high field tokamak (Ip 0.55–1.7 MA, BT 2.8–8 T) using a configuration with B  ×  ∇B drift away from the X-point. Results at 8 T confirm that the L–I power threshold varies only weakly with BT, and that the power range for I-mode increases with BT; no 8 T discharges transitioned to H-mode. Parameter dependences of energy confinement are investigated. Core transport simulations are giving insight into the observed turbulence reduction, profile stiffness and confinement improvement. Pedestal models explain the observed stability to ELMs, and can simulate the observed weakly coherent mode. Conditions for I–H transitions have complex dependences on density as well as power. I-modes have now been maintained in near-DN configurations, leading to improved divertor power flux sharing. Prospects for I-mode on future fusion devices such as ITER and ARC are encouraging. Further experiments on other tokamaks are needed to improve confidence in extrapolation. [ABSTRACT FROM AUTHOR]
Copyright of Nuclear Fusion is the property of IOP Publishing and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
An: 126199468
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  Data: Physics and performance of the I-mode regime over an expanded operating space on Alcator C-Mod.
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  Data: <searchLink fieldCode="AR" term="%22A%2EE%2E+Hubbard%22">A.E. Hubbard</searchLink><relatesTo>1</relatesTo><i> hubbard@psfc.mit.edu</i><br /><searchLink fieldCode="AR" term="%22S%2E-G%2E+Baek%22">S.-G. Baek</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22D%2E+Brunner%22">D. Brunner</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22A%2EJ%2E+Creely%22">A.J. Creely</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22I%2E+Cziegler%22">I. Cziegler</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22E%2E+Edlund%22">E. Edlund</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22J%2EW%2E+Hughes%22">J.W. Hughes</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22B%2E+LaBombard%22">B. LaBombard</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Y%2E+Lin%22">Y. Lin</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Z%2E+Liu%22">Z. Liu</searchLink><relatesTo>3,4</relatesTo><br /><searchLink fieldCode="AR" term="%22E%2ES%2E+Marmar%22">E.S. Marmar</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22M%2EL%2E+Reinke%22">M.L. Reinke</searchLink><relatesTo>5</relatesTo><br /><searchLink fieldCode="AR" term="%22J%2EE%2E+Rice%22">J.E. Rice</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22B%2E+Sorbom%22">B. Sorbom</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22C%2E+Sung%22">C. Sung</searchLink><relatesTo>6</relatesTo><br /><searchLink fieldCode="AR" term="%22J%2E+Terry%22">J. Terry</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22C%2E+Theiler%22">C. Theiler</searchLink><relatesTo>7</relatesTo><br /><searchLink fieldCode="AR" term="%22E%2EA%2E+Tolman%22">E.A. Tolman</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22J%2ER%2E+Walk%22">J.R. Walk</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22A%2EE%2E+White%22">A.E. White</searchLink><relatesTo>1</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Nuclear+Fusion%22">Nuclear Fusion</searchLink>. Dec2017, Vol. 57 Issue 12, p1-1. 1p.
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  Data: <searchLink fieldCode="DE" term="%22Tokamaks%22">Tokamaks</searchLink><br /><searchLink fieldCode="DE" term="%22Plasma+confinement%22">Plasma confinement</searchLink><br /><searchLink fieldCode="DE" term="%22Plasma+temperature%22">Plasma temperature</searchLink><br /><searchLink fieldCode="DE" term="%22Particle+range+%28Nuclear+physics%29%22">Particle range (Nuclear physics)</searchLink><br /><searchLink fieldCode="DE" term="%22Plasma+density%22">Plasma density</searchLink><br /><searchLink fieldCode="DE" term="%22Heat+flux%22">Heat flux</searchLink>
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  Data: New results on the I-mode regime of operation on the Alcator C-Mod tokamak are reported. This ELM-free regime features high energy confinement and a steep temperature pedestal, while particle confinement remains at L-mode levels, giving stationary density and avoiding impurity accumulation. I-mode has now been obtained over nearly all of the magnetic fields and currents possible in this high field tokamak (Ip 0.55–1.7 MA, BT 2.8–8 T) using a configuration with B  ×  ∇B drift away from the X-point. Results at 8 T confirm that the L–I power threshold varies only weakly with BT, and that the power range for I-mode increases with BT; no 8 T discharges transitioned to H-mode. Parameter dependences of energy confinement are investigated. Core transport simulations are giving insight into the observed turbulence reduction, profile stiffness and confinement improvement. Pedestal models explain the observed stability to ELMs, and can simulate the observed weakly coherent mode. Conditions for I–H transitions have complex dependences on density as well as power. I-modes have now been maintained in near-DN configurations, leading to improved divertor power flux sharing. Prospects for I-mode on future fusion devices such as ITER and ARC are encouraging. Further experiments on other tokamaks are needed to improve confidence in extrapolation. [ABSTRACT FROM AUTHOR]
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  Data: <i>Copyright of Nuclear Fusion is the property of IOP Publishing and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1088/1741-4326/aa8570
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