1
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Mulholland P, Aleynikova K, Faber BJ, Pueschel MJ, Proll JHE, Hegna CC, Terry PW, Nührenberg C. Enhanced Transport at High Plasma Pressure and Subthreshold Kinetic Ballooning Modes in Wendelstein 7-X. Phys Rev Lett 2023; 131:185101. [PMID: 37977609 DOI: 10.1103/physrevlett.131.185101] [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: 02/17/2023] [Revised: 08/18/2023] [Accepted: 09/19/2023] [Indexed: 11/19/2023]
Abstract
High-performance fusion plasmas, requiring high pressure β, are not well understood in stellarator-type experiments. Here, the effect of β on ion-temperature-gradient-driven (ITG) turbulence is studied in Wendelstein 7-X (W7-X), showing that subdominant kinetic ballooning modes (KBMs) are unstable well below the ideal MHD threshold and get strongly excited in the turbulence. By zonal-flow erosion, these subthreshold KBMs (stKBMs) affect ITG saturation and enable higher heat fluxes. Controlling stKBMs will be essential to allow W7-X and future stellarators to achieve maximum performance.
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Affiliation(s)
- P Mulholland
- Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - K Aleynikova
- Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany
| | - B J Faber
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M J Pueschel
- Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
- Dutch Institute for Fundamental Energy Research, 5612 AJ Eindhoven, Netherlands
- Department of Physics and Astronomy, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - J H E Proll
- Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - C C Hegna
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - P W Terry
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - C Nührenberg
- Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany
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2
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Gates DA, Anderson D, Anderson S, Zarnstorff M, Spong DA, Weitzner H, Neilson GH, Ruzic D, Andruczyk D, Harris JH, Mynick H, Hegna CC, Schmitz O, Talmadge JN, Curreli D, Maurer D, Boozer AH, Knowlton S, Allain JP, Ennis D, Wurden G, Reiman A, Lore JD, Landreman M, Freidberg JP, Hudson SR, Porkolab M, Demers D, Terry J, Edlund E, Lazerson SA, Pablant N, Fonck R, Volpe F, Canik J, Granetz R, Ware A, Hanson JD, Kumar S, Deng C, Likin K, Cerfon A, Ram A, Hassam A, Prager S, Paz-Soldan C, Pueschel MJ, Joseph I, Glasser AH. Stellarator Research Opportunities: A Report of the National Stellarator Coordinating Committee. J Fusion Energ 2018. [DOI: 10.1007/s10894-018-0152-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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3
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Willensdorfer M, Cote TB, Hegna CC, Suttrop W, Zohm H, Dunne M, Strumberger E, Birkenmeier G, Denk SS, Mink F, Vanovac B, Luhmann LC. Field-Line Localized Destabilization of Ballooning Modes in Three-Dimensional Tokamaks. Phys Rev Lett 2017; 119:085002. [PMID: 28952752 DOI: 10.1103/physrevlett.119.085002] [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: 03/27/2017] [Indexed: 06/07/2023]
Abstract
Field-line localized ballooning modes have been observed at the edge of high confinement mode plasmas in ASDEX Upgrade with rotating 3D perturbations induced by an externally applied n=2 error field and during a moderate level of edge localized mode mitigation. The observed ballooning modes are localized to the field lines which experience one of the two zero crossings of the radial flux surface displacement during one rotation period. The localization of the ballooning modes agrees very well with the localization of the largest growth rates from infinite-n ideal ballooning stability calculations using a realistic 3D ideal magnetohydrodynamic equilibrium. This analysis predicts a lower stability with respect to the axisymmetric case. The primary mechanism for the local lower stability is the 3D distortion of the local magnetic shear.
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Affiliation(s)
- M Willensdorfer
- Max Planck Institute for Plasma Physics, 85748 Garching, Germany
| | - T B Cote
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - C C Hegna
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - W Suttrop
- Max Planck Institute for Plasma Physics, 85748 Garching, Germany
| | - H Zohm
- Max Planck Institute for Plasma Physics, 85748 Garching, Germany
| | - M Dunne
- Max Planck Institute for Plasma Physics, 85748 Garching, Germany
| | - E Strumberger
- Max Planck Institute for Plasma Physics, 85748 Garching, Germany
| | - G Birkenmeier
- Max Planck Institute for Plasma Physics, 85748 Garching, Germany
- Physik-Department E28, Technische Universität München, 85748 Garching, Germany
| | - S S Denk
- Max Planck Institute for Plasma Physics, 85748 Garching, Germany
- Physik-Department E28, Technische Universität München, 85748 Garching, Germany
| | - F Mink
- Max Planck Institute for Plasma Physics, 85748 Garching, Germany
| | - B Vanovac
- FOM-Institute DIFFER, Dutch Institute for Fundamental Energy Research, 5612 AJ Eindhoven, Netherlands
| | - L C Luhmann
- University of California at Davis, Davis, California 95616, USA
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4
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Nakajima N, Hudson SR, Hegna CC. Properties of Ballooning Modes in the Planar Axis Heliotron Configurations with a Large Shafranov Shift. Fusion Science and Technology 2017. [DOI: 10.13182/fst07-a1289] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [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)
- N. Nakajima
- National Institute for Natural Sciences, National Institute for Fusion Science, 322-6 Oroshi, Toki 509-5292, Japan
- The Graduate University for Advanced Studies, Department of Fusion Science, (SOKENDAI), 322-6 Oroshi Toki 509-5292, Japan
| | - S. R. Hudson
- Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543
| | - C. C. Hegna
- University of Wisconsin-Madison, Department of Engineering Physics, Madison, Wisconsin 53706
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5
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Pueschel MJ, Faber BJ, Citrin J, Hegna CC, Terry PW, Hatch DR. Stellarator Turbulence: Subdominant Eigenmodes and Quasilinear Modeling. Phys Rev Lett 2016; 116:085001. [PMID: 26967418 DOI: 10.1103/physrevlett.116.085001] [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: 10/30/2015] [Indexed: 06/05/2023]
Abstract
Owing to complex geometry, gyrokinetic simulations in stellarator geometry produce large numbers of subdominant unstable and stable, near-orthogonal eigenmodes. Here, results based on the full eigenmode spectrum in stellarator geometry are presented for the first time. In the nonlinear state of a low-magnetic-shear ion-temperature-gradient-driven case, a multitude of these modes are active and imprint the system. Turbulent frequency spectra are broadband as a consequence, in addition to a nonlinear, narrow signature at electron frequencies. It is shown that successful quasilinear, mixing-length transport modeling is possible in stellarators, where it is essential to account for all subdominant unstable modes.
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Affiliation(s)
- M J Pueschel
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - B J Faber
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J Citrin
- FOM Institute DIFFER, 3430 BE Nieuwegein, The Netherlands
- CEA, IRFM, F-13108 Saint Paul Lez Durance, France
| | - C C Hegna
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - P W Terry
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - D R Hatch
- Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712, USA
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6
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Nazikian R, Paz-Soldan C, Callen JD, deGrassie JS, Eldon D, Evans TE, Ferraro NM, Grierson BA, Groebner RJ, Haskey SR, Hegna CC, King JD, Logan NC, McKee GR, Moyer RA, Okabayashi M, Orlov DM, Osborne TH, Park JK, Rhodes TL, Shafer MW, Snyder PB, Solomon WM, Strait EJ, Wade MR. Pedestal bifurcation and resonant field penetration at the threshold of edge-localized mode suppression in the DIII-D Tokamak. Phys Rev Lett 2015; 114:105002. [PMID: 25815938 DOI: 10.1103/physrevlett.114.105002] [Citation(s) in RCA: 3] [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: 11/18/2014] [Indexed: 06/04/2023]
Abstract
Rapid bifurcations in the plasma response to slowly varying n=2 magnetic fields are observed as the plasma transitions into and out of edge-localized mode (ELM) suppression. The rapid transition to ELM suppression is characterized by an increase in the toroidal rotation and a reduction in the electron pressure gradient at the top of the pedestal that reduces the perpendicular electron flow there to near zero. These events occur simultaneously with an increase in the inner-wall magnetic response. These observations are consistent with strong resonant field penetration of n=2 fields at the onset of ELM suppression, based on extended MHD simulations using measured plasma profiles. Spontaneous transitions into (and out of) ELM suppression with a static applied n=2 field indicate competing mechanisms of screening and penetration of resonant fields near threshold conditions. Magnetic measurements reveal evidence for the unlocking and rotation of tearinglike structures as the plasma transitions out of ELM suppression.
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Affiliation(s)
- R Nazikian
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - C Paz-Soldan
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - J D Callen
- University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706-1609, USA
| | - J S deGrassie
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - D Eldon
- University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0417, USA
| | - T E Evans
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - N M Ferraro
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - B A Grierson
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - R J Groebner
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - S R Haskey
- Plasma Research Laboratory, Australian National University, Canberra, ACT 0200, Australia
| | - C C Hegna
- University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706-1609, USA
| | - J D King
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - N C Logan
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - G R McKee
- University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706-1609, USA
| | - R A Moyer
- University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0417, USA
| | - M Okabayashi
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - D M Orlov
- University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0417, USA
| | - T H Osborne
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - J-K Park
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - T L Rhodes
- University of California, Los Angeles, Los Angeles, California 90095, USA
| | - M W Shafer
- Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, Tennessee 37831, USA
| | - P B Snyder
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - W M Solomon
- Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451, USA
| | - E J Strait
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
| | - M R Wade
- General Atomics, PO Box 85608, San Diego, California 92186-5608, USA
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7
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Hershkowitz N, Severn GD, Baalrud SD, Hegna CC, Callen JD. Comment on "Ar+ and Xe+ velocities near the presheath-sheath boundary in an Ar/Xe discharge". Phys Rev Lett 2012; 108:139501. [PMID: 22540734 DOI: 10.1103/physrevlett.108.139501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Indexed: 05/31/2023]
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8
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Paz-Soldan C, Brookhart MI, Eckhart AT, Hannum DA, Hegna CC, Sarff JS, Forest CB. Stabilization of the resistive wall mode by a rotating solid conductor. Phys Rev Lett 2011; 107:245001. [PMID: 22243004 DOI: 10.1103/physrevlett.107.245001] [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: 08/11/2011] [Indexed: 05/31/2023]
Abstract
Stabilization of the resistive wall mode (RWM) by high-speed differentially rotating conducting walls is demonstrated in the laboratory. To observe stabilization intrinsic azimuthal plasma rotation must be braked with error fields. Above a critical error field the RWM frequency discontinuously slows (locks) and fast growth subsequently occurs. Wall rotation is found to reduce the locked RWM saturated amplitude and growth rate, with both static (vacuum vessel) wall locked and slowly rotating RWMs observed depending on the alignment of wall to plasma rotation. At high wall rotation RWM onset is found to occur at larger plasma currents, thus increasing the RWM-stable operation window.
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Affiliation(s)
- C Paz-Soldan
- Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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9
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Bongard MW, Fonck RJ, Hegna CC, Redd AJ, Schlossberg DJ. Measurement of peeling mode edge current profile dynamics. Phys Rev Lett 2011; 107:035003. [PMID: 21838369 DOI: 10.1103/physrevlett.107.035003] [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: 01/28/2011] [Indexed: 05/31/2023]
Abstract
Peeling modes, an instability mechanism underlying deleterious edge localized mode (ELM) activity in fusion-grade plasmas, are observed at the edge of limited plasmas in a low aspect ratio tokamak under conditions of high edge current density (J(edge) ∼ 0.1 MA/m2) and low magnetic field (B ∼ 0.1 T). They generate edge-localized, electromagnetic activity with low toroidal mode numbers n≤3 and amplitudes that scale strongly with measured J(edge)/B instability drive, consistent with theory. ELM-like field-aligned, current-carrying filaments form from an initial current-hole J(edge) perturbation that detach and propagate outward.
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Affiliation(s)
- M W Bongard
- Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA
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10
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Cole AJ, Callen JD, Solomon WM, Garofalo AM, Hegna CC, Lanctot MJ, Reimerdes H. Observation of peak neoclassical toroidal viscous force in the DIII-D tokamak. Phys Rev Lett 2011; 106:225002. [PMID: 21702606 DOI: 10.1103/physrevlett.106.225002] [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: 07/21/2010] [Indexed: 05/31/2023]
Abstract
Observation of a theoretically predicted peak in the neoclassical toroidal viscosity (NTV) force as a function of toroidal plasma rotation rate Ω is reported. The NTV was generated by applying n=3 magnetic fields from internal coils to low Ω plasmas produced with nearly balanced neutral beam injection. Locally, the peak corresponds to a toroidal rotation rate Ω(0) where the radial electric field E(r) is near zero as determined by radial ion force balance.
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Affiliation(s)
- A J Cole
- University of Wisconsin, Madison, Wisconsin 53706-1609, USA
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11
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Hegna CC, Callen JD, Cole AJ. Rotation Properties of Tokamak Plasmas. Fusion Science and Technology 2011. [DOI: 10.13182/fst11-a11705] [Citation(s) in RCA: 0] [Impact Index Per Article: 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)
- C. C. Hegna
- University of Wisconsin, Department of Engineering Physics, Madison, Wisconsin 53706
| | - J. D. Callen
- University of Wisconsin, Department of Engineering Physics, Madison, Wisconsin 53706
| | - A. J. Cole
- University of Wisconsin, Department of Engineering Physics, Madison, Wisconsin 53706
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12
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Baalrud SD, Hegna CC, Callen JD. Instability-enhanced collisional friction can determine the Bohm criterion in multiple-ion-species plasmas. Phys Rev Lett 2009; 103:205002. [PMID: 20365986 DOI: 10.1103/physrevlett.103.205002] [Citation(s) in RCA: 5] [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: 07/10/2009] [Indexed: 05/29/2023]
Abstract
A generalized Lenard-Balescu theory that accounts for instability-enhanced collective responses is used to calculate the collisional friction between ion species in the plasma-boundary transition region (presheath). Ion-ion streaming instabilities are shown to cause such a strong frictional force that the relative flow speed between ion species cannot significantly exceed the critical threshold value (DeltaV(c)) at which instability onset occurs. When combined with the Bohm criterion, this condition uniquely determines the flow speed of each ion species at the plasma-sheath boundary. For cold ions, DeltaV(c) --> 0 and each ion species leaves the plasma at a common system sound speed c(s).
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Affiliation(s)
- S D Baalrud
- Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706-1609, USA.
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13
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Baalrud SD, Callen JD, Hegna CC. Instability-enhanced collisional effects and Langmuir's paradox. Phys Rev Lett 2009; 102:245005. [PMID: 19659019 DOI: 10.1103/physrevlett.102.245005] [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: 04/05/2009] [Indexed: 05/28/2023]
Abstract
Anomalously fast equilibration of the electron distribution function to a Maxwellian in gas-discharge plasmas with low temperature and pressure, i.e., Langmuir's paradox, may be explained by electron scattering via an instability-enhanced collective response and hence fluctuations arising from convective ion-acoustic instabilities near the discharge boundaries.
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Affiliation(s)
- S D Baalrud
- Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706-1609, USA.
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14
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Abstract
Recent ideal magnetohydrodynamic (MHD) theory predicts that a perturbation evolving from a linear ballooning instability will continue to grow exponentially in the intermediate nonlinear phase at the same linear growth rate. This prediction is confirmed in ideal MHD simulations. When the Lagrangian compression, a measure of the ballooning nonlinearity, becomes of the order of unity, the intermediate nonlinear phase is entered, during which the maximum plasma displacement amplitude as well as the total kinetic energy continues to grow exponentially at the rate of the corresponding linear phase.
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Affiliation(s)
- P Zhu
- Center for Plasma Theory and Computation, University of Wisconsin-Madison, Madison, WI 53706, USA
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15
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Bergerson WF, Hannum DA, Hegna CC, Kendrick RD, Sarff JS, Forest CB. Observation of resistive and ferritic wall modes in a line-tied pinch. Phys Rev Lett 2008; 101:235005. [PMID: 19113564 DOI: 10.1103/physrevlett.101.235005] [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: 06/08/2008] [Indexed: 05/27/2023]
Abstract
The resistive wall mode is experimentally identified and characterized in a line-tied, cylindrical screw pinch when the edge safety factor is less than a critical value. Different wall materials have been used to change the wall time and show that the growth rates for the RWM scale with wall time and safety factor as expected by theory. The addition of a ferritic wall material outside the conducting shell leads to growth rates larger than the observed RWM and larger than theoretical predictions for the ferritic wall mode.
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Affiliation(s)
- W F Bergerson
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, USA
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16
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Zhu P, Schnack DD, Ebrahimi F, Zweibel EG, Suzuki M, Hegna CC, Sovinec CR. Absence of complete finite-Larmor-radius stabilization in extended MHD. Phys Rev Lett 2008; 101:085005. [PMID: 18764628 DOI: 10.1103/physrevlett.101.085005] [Citation(s) in RCA: 2] [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: 02/29/2008] [Indexed: 05/26/2023]
Abstract
The dominant finite-Larmour-radius (FLR) stabilization effects on interchange instability can be retained by taking into account the ion gyroviscosity or the generalized Ohm's law in an extended MHD model. However, recent simulations and theoretical calculations indicate that complete FLR stabilization of the interchange mode may not be attainable by ion gyroviscosity or the two-fluid effect alone in the framework of extended MHD. For a class of plasma equilibria in certain finite-beta or nonisentropic regimes, the critical wave number for complete FLR stabilization tends toward infinity.
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Affiliation(s)
- P Zhu
- Center for Plasma Theory and Computation, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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17
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Cole AJ, Hegna CC, Callen JD. Effect of neoclassical toroidal viscosity on error-field penetration thresholds in tokamak plasmas. Phys Rev Lett 2007; 99:065001. [PMID: 17930835 DOI: 10.1103/physrevlett.99.065001] [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: 03/12/2007] [Indexed: 05/25/2023]
Abstract
A model for field-error penetration is developed that includes nonresonant as well as the usual resonant field-error effects. The nonresonant components cause a neoclassical toroidal viscous torque that keeps the plasma rotating at a rate comparable to the ion diamagnetic frequency. The new theory is used to examine resonant error-field penetration threshold scaling in Ohmic tokamak plasmas. Compared to previous theoretical results, we find the plasma is less susceptible to error-field penetration and locking, by a factor that depends on the nonresonant error-field amplitude.
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Affiliation(s)
- A J Cole
- University of Wisconsin, Madison, Wisconsin 53706-1609, USA
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18
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Hegna CC, Hudson SR. Loss of second-ballooning stability in three-dimensional equilibria. Phys Rev Lett 2001; 87:035001. [PMID: 11461562 DOI: 10.1103/physrevlett.87.035001] [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: 03/13/2001] [Indexed: 05/23/2023]
Abstract
The effect of three-dimensional geometry on the stability boundaries of ideal ballooning modes is investigated. In particular, the relationship between the symmetry properties of the local shear and the magnetic curvature is addressed for quasisymmetric configurations. The presence of symmetry breaking terms in the local shear can produce localized ballooning instabilities in regions of small average magnetic shear which lower first-ballooning stability thresholds and can potentially eliminate the second stability regime.
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Affiliation(s)
- C C Hegna
- Department of Physics, University of Wisconsin, Madison, Wisconsin 53706-1687, USA
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19
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Hansen AK, Almagri AF, Craig D, Hegna CC, Prager SC, Sarff JS. Momentum transport from nonlinear mode coupling of magnetic fluctuations. Phys Rev Lett 2000; 85:3408-3411. [PMID: 11030908 DOI: 10.1103/physrevlett.85.3408] [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: 04/05/2000] [Indexed: 05/23/2023]
Abstract
A cause of observed anomalous plasma momentum transport in a reversed-field pinch is determined experimentally. Magnetohydrodynamic theory predicts that nonlinear interactions involving triplets of tearing modes produce internal torques that redistribute momentum. Evidence for the nonlinear torque is acquired by detecting the correlation of momentum redistribution with the mode triplets, with the elimination of one of the modes in the triplet, and with the external driving of one of the modes.
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Affiliation(s)
- AK Hansen
- University of Wisconsin Department of Physics,1150 University Avenue, Madison, Wisconsin 53706, USA
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20
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Chang Z, Callen JD, Fredrickson ED, Budny RV, Hegna CC, McGuire KM, Zarnstorff MC. Observation of nonlinear neoclassical pressure-gradient-driven tearing modes in TFTR. Phys Rev Lett 1995; 74:4663-4666. [PMID: 10058567 DOI: 10.1103/physrevlett.74.4663] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [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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Efthimion PC, Mansfield DK, Stratton BC, Synakowski E, Bhattacharjee A, Biglari H, Diamond PH, Goldston RJ, Hegna CC, McCune D, Rewoldt G, Scott S, Tang WM, Taylor G, Waltz RE, Wieland RM, Zarnstorff MC. Observation of temperature-dependent transport in the TFTR tokamak. Phys Rev Lett 1991; 66:421-424. [PMID: 10043803 DOI: 10.1103/physrevlett.66.421] [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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Hegna CC, Bhattacharjee A. Suppression of the tearing mode by energetic ions. Phys Rev Lett 1989; 63:2056-2059. [PMID: 10040751 DOI: 10.1103/physrevlett.63.2056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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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