1
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Abstract
Slow solitary positive-potential peaks sustained by trapped electron deficit in a plasma with asymmetric ion velocity distributions are in principle asymmetric, involving a potential change across the hole. It is shown theoretically how to construct such asymmetric electron holes, thus providing fully consistent solutions of the one-dimensional Vlasov-Poisson equation for a wide variety of prescribed background ion velocity distributions. Because of ion reflection forces experienced by the hole, there is generally only one discrete slow hole velocity that is in equilibrium. Moreover the equilibrium is unstable unless there is a local minimum in the ion velocity distribution, in which the hole velocity then resides. For stable equilibria with Maxwellian electrons, the potential drop across the hole is shown to be Δϕ≃2/9f^{'''}T_{e}/e(eψ/m_{i})^{2}, where ψ is the hole peak potential, f^{'''} is the third derivative of the background ion velocity distribution function at the hole velocity, and T_{e} is the electron temperature. Potential asymmetry is small for holes of the amplitudes usually observed, ψ≲0.5T_{e}/e.
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Affiliation(s)
- I H Hutchinson
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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2
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Abstract
One-dimensional analysis is presented of solitary positive potential plasma structures whose velocity lies within the range of ion distribution velocities that are strongly populated: "slow" electron holes. It is shown that to avoid the self-acceleration of the hole velocity away from ion velocities it must lie within a local minimum in the ion velocity distribution. Quantitative criteria for the existence of stable equilibria are obtained. The background ion distributions required are generally stable to ion-ion modes unless the electron temperature is much higher than the ion temperature. Since slow positive potential solitons are shown not to be possible without a significant contribution from trapped electrons, it seems highly likely that such observed slow potential structures are indeed electron holes.
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Affiliation(s)
- I H Hutchinson
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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3
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Abstract
A detailed comparison is presented of analytical and particle-in-cell simulation investigation of the transverse instability, in two dimensions, of initially one-dimensional electron phase-space hole equilibria. Good quantitative agreement is found between the shift-mode analysis and the simulations for the magnetic field (B) threshold at which the instability becomes overstable (time oscillatory) and for the real and imaginary parts of the frequency. The simulation B threshold for full stabilization exceeds the predictions of shift-mode analysis by 20-30%, because the mode becomes substantially narrower in spatial extent than a pure shift. This threshold shift is qualitatively explained by the kinematic mechanism of instability.
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Affiliation(s)
- I H Hutchinson
- Plasma Science and Fusion Center, MIT, Cambridge, Massachusetts 02139, USA
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4
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Abstract
It is shown through multidimensional particle-in-cell simulations that at least in Maxwellian background plasmas the long-wavelength transverse instability of plasma electron holes is caused not by the previously proposed focusing of trapped particles but instead by kinematic jetting of marginally passing electrons. The mechanism is explained and heuristic analytic estimates obtained which agree with the growth rates and transverse wave numbers observed in the simulations.
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Affiliation(s)
- I H Hutchinson
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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5
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Hughes JW, Hubbard AE, Mossessian DA, LaBombard B, Biewer TM, Granetz RS, Greenwald M, Hutchinson IH, Irby JH, Lin Y, Marmar ES, Porkolab M, Rice JE, Snipes JA, Terry JL, Wolfe S, Zhurovich K. H-Mode Pedestal and L-H Transition Studies on Alcator C-Mod. Fusion Science and Technology 2017. [DOI: 10.13182/fst07-a1425] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [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)
- J. W. Hughes
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - A. E. Hubbard
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - D. A. Mossessian
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - B. LaBombard
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - T. M. Biewer
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - R. S. Granetz
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - M. Greenwald
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - I. H. Hutchinson
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - J. H. Irby
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - Y. Lin
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - E. S. Marmar
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - M. Porkolab
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - J. E. Rice
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - J. A. Snipes
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - J. L. Terry
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - S. Wolfe
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
| | - K. Zhurovich
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge Massachusetts 02139
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6
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Lipschultz B, LaBombard B, Terry JL, Boswell C, Hutchinson IH. Divertor Physics Research on Alcator C-Mod. Fusion Science and Technology 2017. [DOI: 10.13182/fst07-a1428] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [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)
- B. Lipschultz
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - B. LaBombard
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. L. Terry
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - C. Boswell
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - I. H. Hutchinson
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
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7
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Basse NP, Dominguez A, Edlund EM, Fiore CL, Granetz RS, Hubbard AE, Hughes JW, Hutchinson IH, Irby JH, LaBombard B, Lin L, Lin Y, Lipschultz B, Liptac JE, Marmar ES, Mossessian DA, Parker RR, Porkolab M, Rice JE, Snipes JA, Tang V, Terry JL, Wolfe SM, Wukitch SJ, Zhurovich K, Bravenec RV, Phillips PE, Rowan WL, Kramer GJ, Schilling G, Scott SD, Zweben SJ. Diagnostic Systems on Alcator C-Mod. Fusion Science and Technology 2017. [DOI: 10.13182/fst07-a1434] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [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)
- N. P. Basse
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - A. Dominguez
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - E. M. Edlund
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - C. L. Fiore
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - R. S. Granetz
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - A. E. Hubbard
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. W. Hughes
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - I. H. Hutchinson
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. H. Irby
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - B. LaBombard
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - L. Lin
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - Y. Lin
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - B. Lipschultz
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. E. Liptac
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - E. S. Marmar
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - D. A. Mossessian
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - R. R. Parker
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - M. Porkolab
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. E. Rice
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. A. Snipes
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - V. Tang
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. L. Terry
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - S. M. Wolfe
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - S. J. Wukitch
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - K. Zhurovich
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - R. V. Bravenec
- Fusion Research Center, University of Texas, Austin, Texas 78712
| | - P. E. Phillips
- Fusion Research Center, University of Texas, Austin, Texas 78712
| | - W. L. Rowan
- Fusion Research Center, University of Texas, Austin, Texas 78712
| | - G. J. Kramer
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - G. Schilling
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - S. D. Scott
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - S. J. Zweben
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
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8
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Bonoli PT, Parker R, Wukitch SJ, Lin Y, Porkolab M, Wright JC, Edlund E, Graves T, Lin L, Liptac J, Parisot A, Schmidt AE, Tang V, Beck W, Childs R, Grimes M, Gwinn D, Johnson D, Irby J, Kanojia A, Koert P, Marazita S, Marmar E, Terry D, Vieira R, Wallace G, Zaks J, Bernabei S, Brunkhorse C, Ellis R, Fredd E, Greenough N, Hosea J, Kung CC, Loesser GD, Rushinski J, Schilling G, Phillips CK, Wilson JR, Harvey RW, Fiore CL, Granetz R, Greenwald M, Hubbard AE, Hutchinson IH, Labombard B, Lipschultz B, Rice J, Snipes JA, Terry J, Wolfe SM. Wave-Particle Studies in the Ion Cyclotron and Lower Hybrid Ranges of Frequencies in Alcator C-Mod. Fusion Science and Technology 2017. [DOI: 10.13182/fst07-a1430] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [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)
- P. T. Bonoli
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - R. Parker
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - S. J. Wukitch
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - Y. Lin
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - M. Porkolab
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. C. Wright
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - E. Edlund
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - T. Graves
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - L. Lin
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. Liptac
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - A. Parisot
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - A. E. Schmidt
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - V. Tang
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - W. Beck
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - R. Childs
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - M. Grimes
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - D. Gwinn
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - D. Johnson
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. Irby
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - A. Kanojia
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - P. Koert
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - S. Marazita
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - E. Marmar
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - D. Terry
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - R. Vieira
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - G. Wallace
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. Zaks
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - S. Bernabei
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - C. Brunkhorse
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - R. Ellis
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - E. Fredd
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - N. Greenough
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - J. Hosea
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - C. C. Kung
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - G. D. Loesser
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - J. Rushinski
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - G. Schilling
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - C. K. Phillips
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - J. R. Wilson
- Princeton University, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | | | - C. L. Fiore
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - R. Granetz
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - M. Greenwald
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - A. E. Hubbard
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - I. H. Hutchinson
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - B. Labombard
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - B. Lipschultz
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. Rice
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. A. Snipes
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - J. Terry
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
| | - S. M. Wolfe
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139
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9
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Rice JE, Marmar ES, Bonoli PT, Granetz RS, Greenwald MJ, Hubbard AE, Hughes JW, Hutchinson IH, Irby JH, LaBombard B, Lee WD, Lin Y, Mossessian D, Snipes JA, Wolfe SM, Wukitch SJ. Spontaneous Toroidal Rotation in Alcator C-Mod Plasmas with No Momentum Input. Fusion Science and Technology 2017. [DOI: 10.13182/fst07-a1423] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [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)
- J. E. Rice
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - E. S. Marmar
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - P. T. Bonoli
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - R. S. Granetz
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - M. J. Greenwald
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - A. E. Hubbard
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - J. W. Hughes
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - I. H. Hutchinson
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - J. H. Irby
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - B. LaBombard
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - W. D. Lee
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - Y. Lin
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - D. Mossessian
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - J. A. Snipes
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - S. M. Wolfe
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
| | - S. J. Wukitch
- Massachusetts Institute of Technology, Plasma Science and Fusion Center, Cambridge, Massachusetts 02139-4307
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10
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Rice JE, Podpaly YA, Reinke ML, Mumgaard R, Scott SD, Shiraiwa S, Wallace GM, Chouli B, Fenzi-Bonizec C, Nave MFF, Diamond PH, Gao C, Granetz RS, Hughes JW, Parker RR, Bonoli PT, Delgado-Aparicio L, Eriksson LG, Giroud C, Greenwald MJ, Hubbard AE, Hutchinson IH, Irby JH, Kirov K, Mailloux J, Marmar ES, Wolfe SM. Effects of magnetic shear on toroidal rotation in tokamak plasmas with lower hybrid current drive. Phys Rev Lett 2013; 111:125003. [PMID: 24093268 DOI: 10.1103/physrevlett.111.125003] [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: 05/24/2013] [Indexed: 06/02/2023]
Abstract
Application of lower hybrid (LH) current drive in tokamak plasmas can induce both co- and countercurrent directed changes in toroidal rotation, depending on the core q profile. For discharges with q(0) <1, rotation increments in the countercurrent direction are observed. If the LH-driven current is sufficient to suppress sawteeth and increase q(0) above unity, the core toroidal rotation change is in the cocurrent direction. This change in sign of the rotation increment is consistent with a change in sign of the residual stress (the divergence of which constitutes an intrinsic torque that drives the flow) through its dependence on magnetic shear.
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Affiliation(s)
- J E Rice
- PSFC MIT, Cambridge, Massachusetts 02139, USA
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11
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Abstract
Large-scale particle-in-cell calculations of the plasma wake interactions of two negatively charged grains smaller than the Debye length are carried out using the coptic code over a wide range of subsonic plasma flow velocities. In plasmas with the temperature ratio T(e)/T(i)=100, it is found that a single grain's oscillatory wake disappears for flow Mach numbers M less than approximately 0.3, which is the parameter regime where Landau damping is expected to be strong. Neutral collisions suppress potential oscillations above M=0.3, but not the trailing attractive potential peak caused by ion focusing. The transverse (grain-aligning) force on a downstream particle in the wake of another is obtained rigorously from the code in three-dimensional simulations. It shows general agreement with the force that would be deduced from the single-grain wake potential gradient. Except for relatively large grains in the nonlinear collisional regime, the grain-aligning force is very small for slow flow.
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Affiliation(s)
- I H Hutchinson
- Plasma Science and Fusion Center and Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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12
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Abstract
The transverse force on a spherical charged grain lying in the plasma wake of another grain is analyzed to assess the importance of ion-drag perturbation, in addition to the wake-potential-gradient. The ion-drag perturbation is intrinsically one order smaller than the wake-potential force in the ratio of grain size (r(p)) to Debye length (λ(De)). So ion-drag perturbation is important only in nonlinear wakes. Rigorous particle-in-cell calculations of the force are performed in the nonlinear regime with two interacting grains. It is found that even for quite large grains, r(p)/λ(De)=0.1, the force is dominated by the wake-potential gradient. The wake-potential structure can then help explain the preferred alignment of floating dust grains.
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Affiliation(s)
- I H Hutchinson
- Plasma Science and Fusion Center and Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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13
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Ferrara M, Hutchinson IH, Wolfe SM. State Reconstruction and Noise Reduction by Kalman Filter in the Vertical Position Control on Alcator C-Mod. Fusion Science and Technology 2009. [DOI: 10.13182/fst09-a9251] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [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)
- M. Ferrara
- Massachusetts Institute of Technology Plasma Science and Fusion Center 190 Albany Street, Cambridge, Massachusetts 02139
| | - I. H. Hutchinson
- Massachusetts Institute of Technology Plasma Science and Fusion Center 190 Albany Street, Cambridge, Massachusetts 02139
| | - S. M. Wolfe
- Massachusetts Institute of Technology Plasma Science and Fusion Center 190 Albany Street, Cambridge, Massachusetts 02139
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14
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Ince-Cushman A, Rice JE, Reinke M, Greenwald M, Wallace G, Parker R, Fiore C, Hughes JW, Bonoli P, Shiraiwa S, Hubbard A, Wolfe S, Hutchinson IH, Marmar E, Bitter M, Wilson J, Hill K. Observation of self-generated flows in tokamak plasmas with lower-hybrid-driven current. Phys Rev Lett 2009; 102:035002. [PMID: 19257362 DOI: 10.1103/physrevlett.102.035002] [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: 06/27/2008] [Indexed: 05/27/2023]
Abstract
In Alcator C-Mod discharges lower hybrid waves have been shown to induce a countercurrent change in toroidal rotation of up to 60 km/s in the central region of the plasma (r/a approximately <0.4). This modification of the toroidal rotation profile develops on a time scale comparable to the current redistribution time (approximately 100 ms) but longer than the energy and momentum confinement times (approximately 20 ms). A comparison of the co- and countercurrent injected waves indicates that current drive (as opposed to heating) is responsible for the rotation profile modifications. Furthermore, the changes in central rotation velocity induced by lower hybrid current drive (LHCD) are well correlated with changes in normalized internal inductance. The application of LHCD has been shown to generate sheared rotation profiles and a negative increment in the radial electric field profile consistent with a fast electron pinch.
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Affiliation(s)
- A Ince-Cushman
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW16, Cambridge, Massachusetts 02139, USA
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15
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Abstract
The radiated power diagnostics for the Alcator C-Mod tokamak have been upgraded to measure two dimensional structure of the photon emissivity profile in order to investigate poloidal asymmetries in the core radiation. Commonly utilized unbiased absolute extreme ultraviolet (AXUV) diode arrays view the plasma along five different horizontal planes. The layout of the diagnostic set is shown and the results from calibrations and recent experiments are discussed. Data showing a significant, 30%-40%, inboard/outboard emissivity asymmetry during ELM-free H-mode are presented. The ability to use AXUV diode arrays to measure absolute radiated power is explored by comparing diode and resistive bolometer-based emissivity profiles for highly radiative L-mode plasmas seeded with argon. Emissivity profiles match in the core but disagree radially outward resulting in an underprediction of P(rad) of nearly 50% by the diodes compared to P(rad) determined using resistive bolometers.
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Affiliation(s)
- M L Reinke
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW17-225, Cambridge, Massachusetts 02139, USA
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16
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Hutchinson IH. Ion collection by oblique surfaces of an object in a transversely flowing strongly magnetized plasma. Phys Rev Lett 2008; 101:035004. [PMID: 18764261 DOI: 10.1103/physrevlett.101.035004] [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: 01/04/2008] [Indexed: 05/26/2023]
Abstract
The equations governing a collisionless obliquely flowing plasma around an ion-absorbing object in a strong magnetic field are shown to have an exact analytic solution even for an arbitrary (two-dimensional) object shape, when temperature is uniform, and diffusive transport can be ignored. The solution has an extremely simple geometric embodiment. It shows that the ion collection flux density to a convex body's surface depends only upon the orientation of the surface and provides the theoretical justification and calibration of oblique "Mach probes." The exponential form of this exact solution helps explain the approximate fit of this function to previous numerical solutions.
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Affiliation(s)
- I H Hutchinson
- Plasma Science and Fusion Center and Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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17
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18
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Lee WD, Rice JE, Marmar ES, Greenwald MJ, Hutchinson IH, Snipes JA. Observation of anomalous momentum transport in tokamak plasmas with no momentum input. Phys Rev Lett 2003; 91:205003. [PMID: 14683369 DOI: 10.1103/physrevlett.91.205003] [Citation(s) in RCA: 5] [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: 05/09/2003] [Indexed: 05/24/2023]
Abstract
Anomalous momentum transport has been observed in Alcator C-Mod tokamak plasmas through analysis of the time evolution of core impurity toroidal rotation velocity profiles. Following the L-mode to EDA (enhanced D(alpha)) H-mode transition, the ensuing cocurrent toroidal rotation velocity, which is generated in the absence of any external momentum source, is observed to propagate in from the edge plasma to the core. The steady state toroidal rotation velocity profiles are relatively flat and the momentum transport can be simulated with a simple diffusion model. Velocity profiles during edge localized mode free (ELM-free) H-modes are centrally peaked, which suggests the addition of inward momentum convection. In all operating regimes the observed momentum diffusivities are much larger than the neoclassical values.
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Affiliation(s)
- W D Lee
- Plasma Science and Fusion Center, MIT, Cambridge, Massachusetts 02139-4307, USA
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Hutchinson IH, Rice JE, Granetz RS, Snipes JA. Self-acceleration of a tokamak plasma during ohmic H mode. Phys Rev Lett 2000; 84:3330-3333. [PMID: 11019082 DOI: 10.1103/physrevlett.84.3330] [Citation(s) in RCA: 5] [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: 05/28/1999] [Indexed: 05/23/2023]
Abstract
Core plasma rotation is observed to change from counter direction to co-current direction during the transition from low (L) to high (H) confinement mode, in Alcator C-Mod plasmas that are heated purely Ohmically and, hence, have no momentum input. The changes of the toroidal velocities, deduced independently from impurity Doppler measurements and from magnetic perturbations associated with sawteeth, agree. The magnitude of the change is consistent with the previously documented scaling for rotation in ion cyclotron rf-heated H modes. The rotation in this Ohmic experiment is obviously not an rf effect but demonstrates unequivocally a transport effect accelerating the plasma.
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Affiliation(s)
- IH Hutchinson
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts
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Chung KS, Hutchinson IH. Kinetic theory of ion collection by probing objects in flowing strongly magnetized plasmas. Phys Rev A Gen Phys 1988; 38:4721-4731. [PMID: 9900938 DOI: 10.1103/physreva.38.4721] [Citation(s) in RCA: 122] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Kato K, Hutchinson IH. Nonthermal electron velocity distribution measured by electron cyclotron emission in Alcator C tokamak. Phys Rev Lett 1986; 56:340-343. [PMID: 10033162 DOI: 10.1103/physrevlett.56.340] [Citation(s) in RCA: 4] [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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