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Wang Z, Dai Z, Wang S. Nonlinear excitation of zonal flows by turbulent energy flux. Phys Rev E 2022; 106:035205. [PMID: 36266869 DOI: 10.1103/physreve.106.035205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 08/19/2022] [Indexed: 06/16/2023]
Abstract
The nonlinear excitation of zonal flows (ZFs) generated by the ion-temperature-gradient turbulence in a tokamak plasma is investigated by using the global gyrokinetic code nlt. It is found that ZFs are initially driven by the nonlinear self-interaction of the eigenmode. In the nonlinear saturation, the modulational instability becomes important, and its contribution to ZFs can finally be comparable to that of the self-interaction mechanism. More importantly, both types of nonlinear wave-wave interactions can be well described by the turbulent energy flux model.
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Affiliation(s)
- Zihao Wang
- Department of Engineering and Applied Physics, University of Science and Technology of China, Hefei 230026, China
| | - Zongliang Dai
- Department of Engineering and Applied Physics, University of Science and Technology of China, Hefei 230026, China
| | - Shaojie Wang
- Department of Engineering and Applied Physics, University of Science and Technology of China, Hefei 230026, China
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2
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FUJISAWA A. Review of plasma turbulence experiments. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2021; 97:103-119. [PMID: 33692227 PMCID: PMC8019855 DOI: 10.2183/pjab.97.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 12/21/2020] [Indexed: 06/12/2023]
Abstract
Understandings of turbulent plasma have been developed along with nuclear fusion research for more than a half century. Long international research has produced discoveries concerning turbulent plasma that allow us to notice the hidden nature and physics questions that could contribute to other scientific fields and the development of technologies. Guiding concepts have been established up to now that stimulate investigations on turbulent plasma. Research based on concepts concerning symmetry breaking and global linkage requires observing the entire field of plasma turbulence for an ultimate understanding of plasma. This article reviews the achievements as well as contemporary problems regarding turbulence experiments associated with strongly magnetized plasmas in the last and present century, and introduces forthcoming experimental issues, including new diagnostics and physics-oriented devices related to plasma turbulence.
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Affiliation(s)
- Akihide FUJISAWA
- Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan
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3
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Yan Z, McKee GR, Fonck R, Gohil P, Groebner RJ, Osborne TH. Observation of the L-H confinement bifurcation triggered by a turbulence-driven shear flow in a tokamak plasma. PHYSICAL REVIEW LETTERS 2014; 112:125002. [PMID: 24724655 DOI: 10.1103/physrevlett.112.125002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Indexed: 06/03/2023]
Abstract
Comprehensive 2D turbulence and eddy flow velocity measurements on DIII-D demonstrate a rapidly increasing turbulence-driven shear flow that develops ∼100 μs prior to the low-confinement (L mode) to high-confinement (H mode) transition and appears to trigger it. These changes are localized to a narrow layer 1-2 cm inside the magnetic boundary. Increasing heating power increases the Reynolds stress, the energy transfer from turbulence to the poloidal flow, and the edge flow shearing rate that then exceeds the decorrelation rate, suppressing turbulence and triggering the transition.
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Affiliation(s)
- Z Yan
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - G R McKee
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - R Fonck
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - P Gohil
- General Atomics, PO Box 85608, San Diego, California 92186-9784, USA
| | - R J Groebner
- General Atomics, PO Box 85608, San Diego, California 92186-9784, USA
| | - T H Osborne
- General Atomics, PO Box 85608, San Diego, California 92186-9784, USA
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4
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Schmitz L, Zeng L, Rhodes TL, Hillesheim JC, Doyle EJ, Groebner RJ, Peebles WA, Burrell KH, Wang G. Role of zonal flow predator-prey oscillations in triggering the transition to H-mode confinement. PHYSICAL REVIEW LETTERS 2012; 108:155002. [PMID: 22587261 DOI: 10.1103/physrevlett.108.155002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Indexed: 05/31/2023]
Abstract
Direct evidence of zonal flow (ZF) predator-prey oscillations and the synergistic roles of ZF- and equilibrium E×B flow shear in triggering the low- to high-confinement (L- to H-mode) transition in the DIII-D tokamak is presented. Periodic turbulence suppression is first observed in a narrow layer at and just inside the separatrix when the shearing rate transiently exceeds the turbulence decorrelation rate. The final transition to H mode with sustained turbulence and transport reduction is controlled by equilibrium E×B shear due to the increasing ion pressure gradient.
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Affiliation(s)
- L Schmitz
- University of California-Los Angeles, Los Angeles, California 90095, USA
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5
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Conway GD, Angioni C, Ryter F, Sauter P, Vicente J. Mean and oscillating plasma flows and turbulence interactions across the L-H confinement transition. PHYSICAL REVIEW LETTERS 2011; 106:065001. [PMID: 21405471 DOI: 10.1103/physrevlett.106.065001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Indexed: 05/30/2023]
Abstract
A complex interaction between turbulence driven E × B zonal flow oscillations, i.e., geodesic acoustic modes (GAMs), the turbulence, and mean equilibrium flows is observed during the low to high (L-H) plasma confinement mode transition in the ASDEX Upgrade tokamak. Below the L-H threshold at low densities a limit-cycle oscillation forms with competition between the turbulence level and the GAM flow shearing. At higher densities the cycle is diminished, while in the H mode the cycle duration becomes too short to sustain the GAM, which is replaced by large amplitude broadband flow perturbations. Initially GAM amplitude increases as the H-mode transition is approached, but is then suppressed in the H mode by enhanced mean flow shear.
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Affiliation(s)
- G D Conway
- EURATOM-Association IPP, Max-Plank-Institut für Plasmaphysik, D-85748, Garching, Germany
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6
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Ohshima S, Yamamoto S, Takeuchi M, Nagasaki K, Mizuuchi T, Okada H, Minami T, Kobayashi S, Hanatani K, Konoshima S, Sano F. Multichannel Langmuir probe for turbulence study in Heliotron J. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:10E137. [PMID: 21033998 DOI: 10.1063/1.3496980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
New multichannel Langmuir probe system was developed and installed to Heliotron J. The objective of the new probe is to characterize basic turbulence property and the resulting transport in advanced helical configuration. The probe developed here consists of four sets of triple probe and one pin for floating potential measurement. Initial experiments in neutral beam heating plasma were conducted and fluctuation profile of radial and poloidal electric fields and Reynolds stress were estimated. For precise evaluation of the electric fields and Reynolds stress, a technique to compensate radial change of tilt angle between probe array and magnetic surface was proposed and applied to the initial results obtained in edge region of Heliotron J where the complicated magnetic structure exists.
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Affiliation(s)
- S Ohshima
- Institute of Advanced Energy, Kyoto University, Kyoto 611-0011, Japan.
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7
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Holland C, Yu JH, James A, Nishijima D, Shimada M, Taheri N, Tynan GR. Observation of turbulent-driven shear flow in a cylindrical laboratory plasma device. PHYSICAL REVIEW LETTERS 2006; 96:195002. [PMID: 16803106 DOI: 10.1103/physrevlett.96.195002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Indexed: 05/10/2023]
Abstract
An azimuthally symmetric radially sheared plasma fluid flow is observed to spontaneously form in a cylindrical magnetized helicon plasma device with no external sources of momentum input. A turbulent momentum conservation analysis shows that this shear flow is sustained by the Reynolds stress generated by collisional drift turbulence in the device. The results provide direct experimental support for the basic theoretical picture of drift-wave-shear-flow interactions.
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Affiliation(s)
- C Holland
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, 92093-0417, USA
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8
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Gonçalves B, Hidalgo C, Pedrosa MA, Orozco RO, Sánchez E, Silva C. Role of turbulence on edge momentum redistribution in the TJ-II stellarator. PHYSICAL REVIEW LETTERS 2006; 96:145001. [PMID: 16712083 DOI: 10.1103/physrevlett.96.145001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2005] [Indexed: 05/09/2023]
Abstract
Radial profiles of the parallel-radial Reynolds stress component, proportional to the cross correlation between parallel and radial fluctuating velocities, have been measured in the plasma boundary region of the TJ-II stellarator. Experimental results show the existence of significant parallel turbulent forces at plasma densities above the threshold value to trigger perpendicular sheared flows. This finding provides the first experimental evidence of the role of parallel turbulence forces on edge momentum redistribution in fusion devices.
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Affiliation(s)
- B Gonçalves
- Associação Euratom-IST, Avenida Rovisco Pais, 1049-001 Lisbon, Portugal
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9
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Nagashima Y, Hoshino K, Ejiri A, Shinohara K, Takase Y, Tsuzuki K, Uehara K, Kawashima H, Ogawa H, Ido T, Kusama Y, Miura Y. Observation of nonlinear coupling between small-poloidal wave-number potential fluctuations and turbulent potential fluctuations in Ohmically heated plasmas in the JFT-2M tokamak. PHYSICAL REVIEW LETTERS 2005; 95:095002. [PMID: 16197220 DOI: 10.1103/physrevlett.95.095002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2004] [Indexed: 05/04/2023]
Abstract
Two types of electrostatic modes with small-poloidal wave numbers (approximately 1 and 10-15 kHz) are observed in the edge region of Ohmically heated plasmas in the JFT-2M tokamak. The envelope of the higher frequency coherent mode is modulated at the frequency of the lower frequency mode. A bispectral analysis revealed that a significant nonlinear coupling among the two types of fluctuations and the broadband background turbulent potential fluctuations occurs inside the last closed magnetic flux surface, suggesting that a nonlinear process such as the parametric-modulational instability is involved.
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Vianello N, Spada E, Antoni V, Spolaore M, Serianni G, Regnoli G, Cavazzana R, Bergsåker H, Drake JR. Self-regulation of E x B flow shear via plasma turbulence. PHYSICAL REVIEW LETTERS 2005; 94:135001. [PMID: 15903999 DOI: 10.1103/physrevlett.94.135001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2004] [Indexed: 05/02/2023]
Abstract
The momentum balance has been applied to the ExB flow in the edge region of a reversed field pinch (RFP) configuration. All terms, including those involving fluctuations, have been measured in stationary condition in the edge region of the Extrap-T2R RFP experiment. It is found that the component of the Reynolds stress driven by electrostatic fluctuations is the term playing the major role in driving the shear of the ExB flow to a value marginal for turbulent suppression, so that the results are in favor of a turbulence self-regulating mechanism underlying the momentum balance at the edge. Balancing the sheared flow driving and damping terms, the plasma viscosity is found anomalous and consistent with the diffusivity due to electrostatic turbulence.
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Affiliation(s)
- N Vianello
- Consorzio RFX, Associazione EURATOM-ENEA sulla fusione, C.so Stati Uniti 4, I-35127 Padova, Italy
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11
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Fujisawa A. Internal Transport Barrier and Bifurcation Phenomena in Stellarators. FUSION SCIENCE AND TECHNOLOGY 2004. [DOI: 10.13182/fst04-a544] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Akihide Fujisawa
- National Institute for Fusion Science, Oroshi-cho, Toki 509-5292, Japan
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12
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Xu GS, Wan BN, Song M, Li J. Direct measurement of poloidal long-wavelength E x B flows in the HT-7 tokamak. PHYSICAL REVIEW LETTERS 2003; 91:125001. [PMID: 14525366 DOI: 10.1103/physrevlett.91.125001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2003] [Indexed: 05/24/2023]
Abstract
The poloidal long-wavelength E x B time-varying flows were directly measured using a forked Langmuir probe in the HT-7 tokamak. Low-frequency (<10 kHz) E x B flows were observed at the plasma edge, which possess many of the characteristics of zonal flows, including a poloidal long-wavelength (k(theta)rho(i) approximately 0) and narrow radial extent (k(r)rho(i) approximately 0.1). The cross bicoherence of turbulent Reynolds stress indicates the existence of nonlinear three-wave coupling processes and the generation of low-frequency E x B flows. The estimated flow-shearing rate is of the same order of magnitude as the turbulence decorrelation rate and may thus regulate the fluctuation level and thereby the turbulence-driven transport.
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Affiliation(s)
- G S Xu
- Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, People's Republic of China
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13
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Jakubowski M, Fonck RJ, McKee GR. Observation of coherent sheared turbulence flows in the DIII-D Tokamak. PHYSICAL REVIEW LETTERS 2002; 89:265003. [PMID: 12484829 DOI: 10.1103/physrevlett.89.265003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2001] [Indexed: 05/24/2023]
Abstract
Time-resolved measurements of the turbulent density flow field in a tokamak plasma reveal low-frequency ( approximately 15 KHz), coherent oscillations in the poloidal flow, v(theta). These flow oscillations have a long poloidal wavelength (m<3) and narrow radial extent (k(r)rho(i) approximately 0.2). The estimated flow-shearing rate is of the same order of magnitude as the turbulence decorrelation rate and may thus regulate the turbulence amplitude. These features are consistent with theoretically predicted axisymmetric, self-regulating, sheared flows recognized as geodesic acoustic modes.
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Affiliation(s)
- M Jakubowski
- University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706-1687, USA
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14
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Moyer RA, Tynan GR, Holland C, Burin MJ. Increased nonlinear coupling between turbulence and low-frequency fluctuations at the L-H transition. PHYSICAL REVIEW LETTERS 2001; 87:135001. [PMID: 11580596 DOI: 10.1103/physrevlett.87.135001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2000] [Indexed: 05/23/2023]
Abstract
The nonlinear coupling between small scale high-frequency turbulence and larger scale lower-frequency fluctuations increases transiently in transitions to improved confinement in the DIII-D tokamak. This increase starts before the rapid turbulence suppression and E x B shear-flow development in the region that becomes the H-mode transport barrier/shear flow region. After the transition, the coupling returns to L-mode levels. These results are consistent with expectations for spontaneous transitions to improved confinement triggered by a turbulence-driven sheared flow.
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Affiliation(s)
- R A Moyer
- Mechanical and Aerospace Engineering Department, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
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