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Varennes R, Garbet X, Vermare L, Sarazin Y, Dif-Pradalier G, Grandgirard V, Ghendrih P, Donnel P, Peret M, Obrejan K, Bourne E. Synergy of Turbulent Momentum Drive and Magnetic Braking. Phys Rev Lett 2022; 128:255002. [PMID: 35802431 DOI: 10.1103/physrevlett.128.255002] [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: 12/01/2021] [Revised: 02/17/2022] [Accepted: 06/10/2022] [Indexed: 06/15/2023]
Abstract
In absence of external torque, plasma rotation in tokamaks results from a balance between collisional magnetic braking and turbulent drive. The outcome of this competition and cooperation is essential to determine the plasma flow. A reduced model, supported by gyrokinetic simulations, is first used to explain and quantify the competition only. The ripple amplitude above which magnetic drag overcomes turbulent viscosity is obtained. The synergetic impact of ripple on the turbulent toroidal Reynolds stress is explored. Simulations show that the main effect comes from an enhancement of the radial electric field shear by the ripple, which in turn impacts the residual stress.
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Affiliation(s)
- R Varennes
- CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
| | - X Garbet
- CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
| | - L Vermare
- LPP, CNRS, Ecole polytechnique, 91128 Palaiseau, France
| | - Y Sarazin
- CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
| | | | | | - P Ghendrih
- CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
| | - P Donnel
- CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
| | - M Peret
- CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
| | - K Obrejan
- CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
| | - E Bourne
- CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
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2
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Affiliation(s)
- X. Garbet
- Association Euratom-CEA, CEA/DSM/DRFC CEA-Cadarache, 13108 Saint Paul Lez Durance (France) Tel. +33 (0)4 42 25 49 29
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3
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Mantica P, Corrigan G, Garbet X, Imbeaux F, Lonnroth J, Parail V, Tala T, Taroni A, Valisa M, Weisen H. Chapter 10: Core Transport Studies in JET. Fusion Science and Technology 2017. [DOI: 10.13182/fst08-a1750] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [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. Mantica
- Istituto di Fisica del Plasma, Euratom/ENEA-CNR Association, Via Cozzi 53, 20125 Milano, Italy
| | - G. Corrigan
- Culham Science Centre, EURATOM/UKAEA Fusion Association, Abingdon OX14 3DB, United Kingdom
| | - X. Garbet
- Association EURATOM-CEA, CEA Cadarache, 13108 St Paul-Lez-Durance, France
| | - F. Imbeaux
- Association EURATOM-CEA, CEA Cadarache, 13108 St Paul-Lez-Durance, France
| | - J. Lonnroth
- Association EURATOM-Tekes, Helsinki University of Technology, P.O. Box 2200, 02015 HUT, Finland
| | - V. Parail
- Culham Science Centre, EURATOM/UKAEA Fusion Association, Abingdon OX14 3DB, United Kingdom
| | - T. Tala
- Association EURATOM-TEKES, VTT, P.O. Box 1000, FIN-02044 VTT, Finland
| | - A. Taroni
- Former Member of the JET Joint Undertaking
| | - M. Valisa
- Consorzio RFX-Associazione Euratom-Enea sulla Fusione, I-35127 Padova, Italy
| | - H. Weisen
- EPFL, CRPP, Association EURATOM—Confederation Suisse, 1015 Lausanne, Switzerland
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4
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Dif-Pradalier G, Hornung G, Ghendrih P, Sarazin Y, Clairet F, Vermare L, Diamond PH, Abiteboul J, Cartier-Michaud T, Ehrlacher C, Estève D, Garbet X, Grandgirard V, Gürcan ÖD, Hennequin P, Kosuga Y, Latu G, Maget P, Morel P, Norscini C, Sabot R, Storelli A. Finding the elusive E×B staircase in magnetized plasmas. Phys Rev Lett 2015; 114:085004. [PMID: 25768769 DOI: 10.1103/physrevlett.114.085004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Indexed: 06/04/2023]
Abstract
Turbulence in hot magnetized plasmas is shown to generate permeable localized transport barriers that globally organize into the so-called "ExB staircase" [G. Dif-Pradalier et al., Phys. Rev. E, 82, 025401(R) (2010)]. Its domain of existence and dependence with key plasma parameters is discussed theoretically. Based on these predictions, staircases are observed experimentally in the Tore Supra tokamak by means of high-resolution fast-sweeping X-mode reflectometry. This observation strongly emphasizes the critical role of mesoscale self-organization in plasma turbulence and may have far-reaching consequences for turbulent transport models and their validation.
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Affiliation(s)
| | - G Hornung
- Department of Applied Physics, Ghent University, 9000 Gent, Belgium
| | - Ph Ghendrih
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - Y Sarazin
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - F Clairet
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - L Vermare
- Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau, France
| | - P H Diamond
- CASS and CMTFO, University of California at San Diego, San Diego, California 92093, USA
- WCI Center for Fusion Theory, NFRI, Daejeon 305-333, Korea
| | - J Abiteboul
- Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany
| | | | - C Ehrlacher
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - D Estève
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - X Garbet
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - V Grandgirard
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - Ö D Gürcan
- Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau, France
| | - P Hennequin
- Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau, France
| | - Y Kosuga
- Institute for Advanced Study, Kyushu University, Fukuoka 816-8580, Japan
| | - G Latu
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - P Maget
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - P Morel
- Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau, France
| | - C Norscini
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - R Sabot
- CEA, IRFM, F-13108 St. Paul-lez-Durance cedex, France
| | - A Storelli
- Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau, France
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5
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Orain F, Bécoulet M, Huijsmans GTA, Dif-Pradalier G, Hoelzl M, Morales J, Garbet X, Nardon E, Pamela S, Passeron C, Latu G, Fil A, Cahyna P. Resistive reduced MHD modeling of multi-edge-localized-mode cycles in Tokamak X-point plasmas. Phys Rev Lett 2015; 114:035001. [PMID: 25659004 DOI: 10.1103/physrevlett.114.035001] [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: 05/13/2014] [Indexed: 06/04/2023]
Abstract
The full dynamics of a multi-edge-localized-mode (ELM) cycle is modeled for the first time in realistic tokamak X-point geometry with the nonlinear reduced MHD code jorek. The diamagnetic rotation is found to be instrumental to stabilize the plasma after an ELM crash and to model the cyclic reconstruction and collapse of the plasma pressure profile. ELM relaxations are cyclically initiated each time the pedestal gradient crosses a triggering threshold. Diamagnetic drifts are also found to yield a near-symmetric ELM power deposition on the inner and outer divertor target plates, consistent with experimental measurements.
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Affiliation(s)
- F Orain
- CEA-IRFM, Cadarache, 13108 Saint-Paul-Lez-Durance, France
| | - M Bécoulet
- CEA-IRFM, Cadarache, 13108 Saint-Paul-Lez-Durance, France
| | - G T A Huijsmans
- ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 Saint-Paul-Lez-Durance, France
| | | | - M Hoelzl
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - J Morales
- CEA-IRFM, Cadarache, 13108 Saint-Paul-Lez-Durance, France
| | - X Garbet
- CEA-IRFM, Cadarache, 13108 Saint-Paul-Lez-Durance, France
| | - E Nardon
- CEA-IRFM, Cadarache, 13108 Saint-Paul-Lez-Durance, France
| | - S Pamela
- CCFE, Culham Science Centre, Oxon, Abingdon, Oxfordshire OX14 3DB, United Kingdom
| | - C Passeron
- CEA-IRFM, Cadarache, 13108 Saint-Paul-Lez-Durance, France
| | - G Latu
- CEA-IRFM, Cadarache, 13108 Saint-Paul-Lez-Durance, France
| | - A Fil
- CEA-IRFM, Cadarache, 13108 Saint-Paul-Lez-Durance, France
| | - P Cahyna
- Institute of Plasma Physics ASCR, Za Slovankou 1782/3, 182 00 Prague 8, Czech Republic
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6
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Bécoulet M, Orain F, Huijsmans GTA, Pamela S, Cahyna P, Hoelzl M, Garbet X, Franck E, Sonnendrücker E, Dif-Pradalier G, Passeron C, Latu G, Morales J, Nardon E, Fil A, Nkonga B, Ratnani A, Grandgirard V. Mechanism of edge localized mode mitigation by resonant magnetic perturbations. Phys Rev Lett 2014; 113:115001. [PMID: 25259985 DOI: 10.1103/physrevlett.113.115001] [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: 03/11/2014] [Indexed: 06/03/2023]
Abstract
A possible mechanism of edge localized modes (ELMs) mitigation by resonant magnetic perturbations (RMPs) is proposed based on the results of nonlinear resistive magnetohydrodynamic modeling using the jorek code, realistic JET-like plasma parameters and an RMP spectrum of JET error-field correction coils (EFCC) with a main toroidal number n=2 were used in the simulations. Without RMPs, a large ELM relaxation is obtained mainly due to the most unstable medium-n ballooning mode. The externally imposed RMP drives nonlinearly the modes coupled to n=2 RMP which produce small multimode relaxations, mitigated ELMs. The modes driven by RMPs exhibit a tearinglike structure and produce additional islands. Mitigated ELMs deposit energy into the divertor mainly in the structures ("footprints") created by n=2 RMPs, however, slightly modulated by other nonlinearly driven even harmonics. The divertor power flux during a ELM phase mitigated by RMPs is reduced almost by a factor of 10. The mechanism of ELM mitigation by RMPs proposed here reproduces generic features of high collisionality RMP experiments, where large ELMs are replaced by small, much more frequent ELMs or magnetic turbulence. Total ELM suppression was also demonstrated in modeling at higher RMP amplitude.
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Affiliation(s)
- M Bécoulet
- CEA, IRFM, 13108 Saint-Paul-Lez-Durance, France
| | - F Orain
- CEA, IRFM, 13108 Saint-Paul-Lez-Durance, France
| | - G T A Huijsmans
- ITER Organization, Route de Vinon-sur-Verdon, 13067 Saint-Paul-Lez-Durance, France
| | - S Pamela
- CCFE, Culham Science Centre, Oxon OX14 3DB, United Kingdom
| | - P Cahyna
- Institute of Plasma Physics ASCR, 182 00 Prague 8, Czech Republic
| | - M Hoelzl
- Max-Planck-Institut, 85748 Garching, Germany
| | - X Garbet
- CEA, IRFM, 13108 Saint-Paul-Lez-Durance, France
| | - E Franck
- Max-Planck-Institut, 85748 Garching, Germany
| | | | | | - C Passeron
- CEA, IRFM, 13108 Saint-Paul-Lez-Durance, France
| | - G Latu
- CEA, IRFM, 13108 Saint-Paul-Lez-Durance, France
| | - J Morales
- CEA, IRFM, 13108 Saint-Paul-Lez-Durance, France
| | - E Nardon
- CEA, IRFM, 13108 Saint-Paul-Lez-Durance, France
| | - A Fil
- CEA, IRFM, 13108 Saint-Paul-Lez-Durance, France
| | - B Nkonga
- Laboratoire de Mathématiques J.A. Dieudonné, UMR 7351, CNRS UNS, Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 02, France
| | - A Ratnani
- Laboratoire de Mathématiques J.A. Dieudonné, UMR 7351, CNRS UNS, Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 02, France
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7
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Strugarek A, Sarazin Y, Zarzoso D, Abiteboul J, Brun AS, Cartier-Michaud T, Dif-Pradalier G, Garbet X, Ghendrih P, Grandgirard V, Latu G, Passeron C, Thomine O. Unraveling quasiperiodic relaxations of transport barriers with gyrokinetic simulations of tokamak plasmas. Phys Rev Lett 2013; 111:145001. [PMID: 24138245 DOI: 10.1103/physrevlett.111.145001] [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: 09/25/2012] [Indexed: 06/02/2023]
Abstract
The generation and dynamics of transport barriers governed by sheared poloidal flows are analyzed in flux-driven 5D gyrokinetic simulations of ion temperature gradient driven turbulence in tokamak plasmas. The transport barrier is triggered by a vorticity source that polarizes the system. The chosen source captures characteristic features of some experimental scenarios, namely, the generation of a sheared electric field coupled to anisotropic heating. For sufficiently large shearing rates, turbulent transport is suppressed and a transport barrier builds up, in agreement with the common understanding of transport barriers. The vorticity source also governs a secondary instability--driven by the temperature anisotropy (T(∥)≠T(⊥)). Turbulence and its associated zonal flows are generated in the vicinity of the barrier, destroying the latter due to the screening of the polarization source by the zonal flows. These barrier relaxations occur quasiperiodically, and generically result from the decoupling between the dynamics of the barrier generation, triggered by the source driven sheared flow, and that of the crash, triggered by the secondary instability. This result underlines that barriers triggered by sheared flows are prone to relaxations whenever secondary instabilities come into play.
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Affiliation(s)
- A Strugarek
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France and Laboratoire AIM Paris-Saclay, CEA/Irfu Université Paris-Diderot CNRS/INSU, F-91191 Gif-sur-Yvette, France
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8
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Zarzoso D, Sarazin Y, Garbet X, Dumont R, Strugarek A, Abiteboul J, Cartier-Michaud T, Dif-Pradalier G, Ghendrih P, Grandgirard V, Latu G, Passeron C, Thomine O. Impact of energetic-particle-driven geodesic acoustic modes on turbulence. Phys Rev Lett 2013; 110:125002. [PMID: 25166813 DOI: 10.1103/physrevlett.110.125002] [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: 12/09/2012] [Indexed: 06/03/2023]
Abstract
The impact on turbulent transport of geodesic acoustic modes excited by energetic particles is evidenced for the first time in flux-driven 5D gyrokinetic simulations using the Gysela code. Energetic geodesic acoustic modes (EGAMs) are excited in a regime with a transport barrier in the outer radial region. The interaction between EGAMs and turbulence is such that turbulent transport can be enhanced in the presence of EGAMs, with the subsequent destruction of the transport barrier. This scenario could be particularly critical in those plasmas, such as burning plasmas, exhibiting a rich population of suprathermal particles capable of exciting energetic modes.
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Affiliation(s)
- D Zarzoso
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
| | - Y Sarazin
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
| | - X Garbet
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
| | - R Dumont
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
| | - A Strugarek
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France and Laboratoire AIM Paris-Saclay, CEA/Irfu Université Paris-Diderot CNRS/INSU, 91191 Gif-sur-Yvette, France
| | - J Abiteboul
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
| | | | | | - Ph Ghendrih
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
| | | | - G Latu
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
| | - C Passeron
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
| | - O Thomine
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
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9
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Futatani S, del-Castillo-Negrete D, Garbet X, Benkadda S, Dubuit N. Self-consistent dynamics of impurities in magnetically confined plasmas: turbulence intermittency and nondiffusive transport. Phys Rev Lett 2012; 109:185005. [PMID: 23215289 DOI: 10.1103/physrevlett.109.185005] [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: 03/30/2012] [Indexed: 06/01/2023]
Abstract
Self-consistent turbulent transport of high-concentration impurities in magnetically confined fusion plasmas is studied using a three-dimensional nonlinear fluid global turbulence model which includes ion-temperature gradient and trapped electron mode instabilities. It is shown that the impurity concentration can have a dramatic feedback in the turbulence and, as a result, it can significantly change the transport properties of the plasma. High concentration impurities can trigger strong intermittency that manifests in non-Gaussian heavy tails of the probability density functions of the E × B fluctuations and of the ion-temperature flux fluctuations. At the heart of this self-consistent coupling is the existence of inward propagating ion-temperature fronts with a sharp gradient at the leading edge that give rise to instabilities and avalanchelike bursty transport. Numerical evidence of time nonlocality (i.e., history dependence) in the delayed response of the flux to the gradient is presented.
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Affiliation(s)
- S Futatani
- ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul les Durance, France
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10
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Garbet X. Introduction to Drift Wave Turbulence Modelling. Fusion Science and Technology 2012. [DOI: 10.13182/fst12-a13503] [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)
- X. Garbet
- CEA, IRFM, F-13108 Saint Paul Lez Durance, France, Tel. +33 (0)4 42 25 49 29
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11
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Elbeze D, Guimarães-Filho Z, Molina D, Ségui JL, Benkadda S, Dubuit N, Garbet X, Sabot R. Study of high frequency MHD modes from ECE radiometer in Tore Supra. EPJ Web of Conferences 2012. [DOI: 10.1051/epjconf/20123203012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Muraglia M, Agullo O, Benkadda S, Yagi M, Garbet X, Sen A. Generation and amplification of magnetic islands by drift interchange turbulence. Phys Rev Lett 2011; 107:095003. [PMID: 21929248 DOI: 10.1103/physrevlett.107.095003] [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: 12/21/2010] [Indexed: 05/31/2023]
Abstract
We investigate the multiscale nonlinear dynamics of a linearly stable or unstable tearing mode with small-scale interchange turbulence using 2D MHD numerical simulations. For a stable tearing mode, the nonlinear beating of the fastest growing small-scale interchange modes drives a magnetic island with an enhanced growth rate to a saturated size that is proportional to the turbulence generated anomalous diffusion. For a linearly unstable tearing mode the island saturation size scales inversely as one-fourth power of the linear tearing growth rate in accordance with weak turbulence theory predictions. Turbulence is also seen to introduce significant modifications in the flow patterns surrounding the magnetic island.
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Affiliation(s)
- M Muraglia
- France-Japan Magnetic Fusion Laboratory, LIA 336 CNRS, 13397 Marseille Cedex 20, France
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13
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Nguyen C, Lütjens H, Garbet X, Grandgirard V, Lesur M. Existence of metastable kinetic modes. Phys Rev Lett 2010; 105:205002. [PMID: 21231240 DOI: 10.1103/physrevlett.105.205002] [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: 05/02/2010] [Indexed: 05/30/2023]
Abstract
The nonlinear evolution of resonantly driven systems, such as suprathermal particle driven modes in magnetically confined plasmas, is shown to strongly depend on the existence and nature of an underlying damping mechanism. When background resonant damping is present, subcritical states can take place. In particular, purely nonlinear steady-state regimes are found, whose destabilization threshold and saturation levels are calculated and validated using numerical simulations. This nonlinear behavior can be of relevance for acoustic modes in magnetically confined plasmas.
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Affiliation(s)
- C Nguyen
- Centre de Physique Théorique, CNRS-Ecole Polytechnique, Palaiseau, France.
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14
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Dif-Pradalier G, Diamond PH, Grandgirard V, Sarazin Y, Abiteboul J, Garbet X, Ghendrih P, Strugarek A, Ku S, Chang CS. On the validity of the local diffusive paradigm in turbulent plasma transport. Phys Rev E Stat Nonlin Soft Matter Phys 2010; 82:025401. [PMID: 20866867 DOI: 10.1103/physreve.82.025401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Indexed: 05/29/2023]
Abstract
A systematic, constructive and self-consistent procedure to quantify nonlocal, nondiffusive action at a distance in plasma turbulence is exposed and applied to turbulent heat fluxes computed from the state-of-the-art full- f, flux-driven gyrokinetic GYSELA and XGC1 codes. A striking commonality is found: heat transport below a dynamically selected mesoscale has the structure of a Lévy distribution, is strongly nonlocal, nondiffusive, scale-free, and avalanche mediated; at larger scales, we report the observation of a self-organized flow structure which we call the " E × B staircase" after its planetary analog.
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Affiliation(s)
- G Dif-Pradalier
- Center for Astrophysics and Space Sciences, UCSD, La Jolla, CA 92093, USA.
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15
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Villegas D, Guirlet R, Bourdelle C, Hoang GT, Garbet X, Sabot R. Experimental electron temperature gradient dependence of heavy impurity transport in fusion devices. Phys Rev Lett 2010; 105:035002. [PMID: 20867773 DOI: 10.1103/physrevlett.105.035002] [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: 03/19/2010] [Indexed: 05/29/2023]
Abstract
The turbulent impurity (nickel) transport dependence on the normalized electron temperature gradient has been analyzed in sawtooth-free electron cyclotron wave heated Tore Supra plasmas. In the core, our experimental analysis shows that the lower R/L((T)(e)), the lower the nickel diffusion coefficient. The latter decreases until the instability threshold is reached. The experimental threshold is in agreement with the one computed by a gyrokinetic model. Further out, R/L((T)(e)) plays no role in the impurity diffusion. This set of experimental results is consistent with a quasilinear gyrokinetic analysis.
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Affiliation(s)
- D Villegas
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
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16
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Garbet X. Introduction to Drift Wave Turbulence Modelling. Fusion Science and Technology 2010. [DOI: 10.13182/fst10-a9427] [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)
- X. Garbet
- CEA, IRFM, F-13108 Saint Paul Lez Durance, France, Tel. +33 (0)4 42 25 49 29, e-mail:
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17
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Futatani S, Garbet X, Benkadda S, Dubuit N. Reversal of impurity pinch velocity in tokamaks plasma with a reversed magnetic shear configuration. Phys Rev Lett 2010; 104:015003. [PMID: 20366368 DOI: 10.1103/physrevlett.104.015003] [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: 07/18/2009] [Indexed: 05/29/2023]
Abstract
Impurity transport in tokamak core plasmas is investigated with a three-dimensional fluid global code. It is shown that, in the presence of an internal transport barrier (ITB) created by a reversed magnetic shear configuration, one can obtain a reversal of the impurity pinch velocity which can change from the inward direction to the outward direction. This scenario is favorable for expelling impurities from the central region and decontaminating the core plasma. The mechanism of pinch reversal is attributed to a change of direction of the curvature pinch and to a modification of the dominant underlying instability caused by a change of the gradient of the ion temperature and consequently of the ITB formation.
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Affiliation(s)
- S Futatani
- International Institute for Fusion Science, CNRS-Université de Provence, Centre de St. Jérôme, Case 321, 13397 Marseille Cedex 20, France
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18
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Sandberg I, Benkadda S, Garbet X, Ropokis G, Hizanidis K, del-Castillo-Negrete D. Universal probability distribution function for bursty transport in plasma turbulence. Phys Rev Lett 2009; 103:165001. [PMID: 19905701 DOI: 10.1103/physrevlett.103.165001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Indexed: 05/28/2023]
Abstract
Bursty transport phenomena associated with convective motion present universal statistical characteristics among different physical systems. In this Letter, a stochastic univariate model and the associated probability distribution function for the description of bursty transport in plasma turbulence is presented. The proposed stochastic process recovers the universal distribution of density fluctuations observed in plasma edge of several magnetic confinement devices and the remarkable scaling between their skewness S and kurtosis K. Similar statistical characteristics of variabilities have been also observed in other physical systems that are characterized by convection such as the x-ray fluctuations emitted by the Cygnus X-1 accretion disc plasmas and the sea surface temperature fluctuations.
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Affiliation(s)
- I Sandberg
- National Technical University of Athens, Association Euratom-Hellenic Republic, Athens 15773, Greece and National Observatory of Athens, Institute for Space Applications and Remote Sensing, Penteli 15236, Greece
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19
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Muraglia M, Agullo O, Benkadda S, Garbet X, Beyer P, Sen A. Nonlinear dynamics of magnetic islands imbedded in small-scale turbulence. Phys Rev Lett 2009; 103:145001. [PMID: 19905575 DOI: 10.1103/physrevlett.103.145001] [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: 09/02/2008] [Indexed: 05/28/2023]
Abstract
The nonlinear dynamics of magnetic tearing islands imbedded in a pressure gradient driven turbulence is investigated numerically in a reduced magnetohydrodynamic model. The study reveals regimes where the linear and nonlinear phases of the tearing instability are controlled by the properties of the pressure gradient. In these regimes, the interplay between the pressure and the magnetic flux determines the dynamics of the saturated state. A secondary instability can occur and strongly modify the magnetic island dynamics by triggering a poloidal rotation. It is shown that the complex nonlinear interaction between the islands and turbulence is nonlocal and involves small scales.
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Affiliation(s)
- M Muraglia
- France-Japan Magnetic Fusion Laboratory, LIA 336 CNRS, Marseille, France
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20
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Dif-Pradalier G, Grandgirard V, Sarazin Y, Garbet X, Ghendrih P. Interplay between gyrokinetic turbulence, flows, and collisions: perspectives on transport and poloidal rotation. Phys Rev Lett 2009; 103:065002. [PMID: 19792575 DOI: 10.1103/physrevlett.103.065002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Revised: 04/15/2009] [Indexed: 05/28/2023]
Abstract
The impact of ion-ion collisions on confinement is investigated with the full-f and global gyrokinetic Gysela code through a series of nonlinear turbulence simulations for tokamak parameters. A twofold scan in the turbulence drive and in collisionality is performed, highlighting (i) a heat transport expressed in terms of critical quantities-threshold and exponent, (ii) a first evidence of turbulent generation of poloidal momentum, and (iii) the dominance of mean flow shear, mediated through the turbulent corrugation of the mean profiles, with regard to the oft-invoked zonal flow shear.
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Affiliation(s)
- G Dif-Pradalier
- Association Euratom-CEA, CEA/IRFM, F-13108 St. Paul-lez-Durance cedex, France
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21
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Gürcan OD, Garbet X, Hennequin P, Diamond PH, Casati A, Falchetto GL. Wave-number spectrum of drift-wave turbulence. Phys Rev Lett 2009; 102:255002. [PMID: 19659085 DOI: 10.1103/physrevlett.102.255002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Indexed: 05/28/2023]
Abstract
A simple model for the evolution of turbulence fluctuation spectra, which includes neighboring interactions leading to the usual dual cascade as well as disparate scale interactions corresponding to refraction by large scale structures, is derived. The model recovers the usual Kraichnan-Kolmogorov picture in the case of exclusively local interactions and midrange drive. On the other hand, when disparate scale interactions are dominant, a simple spectrum for the density fluctuations of the form |nk|2 proportional to k(-3)/(1+k2)2 is obtained. This simple prediction is then compared to, and found to be in fair agreement with, Tore Supra CO2 laser scattering data.
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Affiliation(s)
- O D Gürcan
- Laboratoire de Physique des Plasmas, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex, France.
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22
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Angelino P, Garbet X, Villard L, Bottino A, Jolliet S, Ghendrih P, Grandgirard V, McMillan BF, Sarazin Y, Dif-Pradalier G, Tran TM. Role of plasma elongation on turbulent transport in magnetically confined plasmas. Phys Rev Lett 2009; 102:195002. [PMID: 19518964 DOI: 10.1103/physrevlett.102.195002] [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: 09/26/2008] [Indexed: 05/27/2023]
Abstract
The theoretical study of plasma turbulence is of central importance to fusion research. Experimental evidence indicates that the confinement time results mainly from the turbulent transport of energy, the magnitude of which depends on the turbulent state resulting from nonlinear saturation mechanisms, in particular, the self-generation of coherent macroscopic structures and large scale flows. Plasma geometry has a strong impact on the structure and magnitude of these flows and also modifies the mode linear growth rates. Nonlinear global gyrokinetic simulations in realistic tokamak magnetohydrodynamic equilibria show how plasma shape can control the turbulent transport. Results are best described in terms of an effective temperature gradient. With increasing plasma elongation, the nonlinear critical effective gradient is not modified while the stiffness of transport is decreasing.
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Affiliation(s)
- P Angelino
- Association Euratom-CEA, CEA/DSM/IRFM, Cadarache, France
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23
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Casati A, Gerbaud T, Hennequin P, Bourdelle C, Candy J, Clairet F, Garbet X, Grandgirard V, Gürcan OD, Heuraux S, Hoang GT, Honoré C, Imbeaux F, Sabot R, Sarazin Y, Vermare L, Waltz RE. Turbulence in the TORE SUPRA tokamak: measurements and validation of nonlinear simulations. Phys Rev Lett 2009; 102:165005. [PMID: 19518721 DOI: 10.1103/physrevlett.102.165005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Indexed: 05/27/2023]
Abstract
Turbulence measurements in TORE SUPRA tokamak plasmas have been quantitatively compared to predictions by nonlinear gyrokinetic simulations. For the first time, numerical results simultaneously match within experimental uncertainty (a) the magnitude of effective heat diffusivity, (b) rms values of density fluctuations, and (c) wave-number spectra in both the directions perpendicular to the magnetic field. Moreover, the nonlinear simulations help to revise as an instrumental effect the apparent experimental evidence of strong turbulence anisotropy at spatial scales of the order of ion-sound Larmor radius.
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Affiliation(s)
- A Casati
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France.
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24
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Macor A, Goniche M, Artaud JF, Decker J, Elbeze D, Garbet X, Giruzzi G, Hoang GT, Maget P, Mazon D, Molina D, Nguyen C, Peysson Y, Sabot R, Ségui JL. Redistribution of suprathermal electrons due to fishbone frequency jumps. Phys Rev Lett 2009; 102:155005. [PMID: 19518643 DOI: 10.1103/physrevlett.102.155005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Revised: 11/12/2008] [Indexed: 05/27/2023]
Abstract
MHD instabilities driven by fast electrons identified as fishbonelike modes have been detected on Tore Supra during lower hybrid current drive discharges. Direct experimental evidence is reported of a novel feature: the regular redistribution of suprathermal electrons toward external tokamak regions which are correlated to periodic mode frequency jumps. Sharp drops of the electron temperature time trace are factually linked to the cyclical deterioration of the fast electron confinement.
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Affiliation(s)
- A Macor
- CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
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25
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Leconte M, Beyer P, Garbet X, Benkadda S. Control of transport-barrier relaxations by resonant magnetic perturbations. Phys Rev Lett 2009; 102:045006. [PMID: 19257433 DOI: 10.1103/physrevlett.102.045006] [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: 11/13/2008] [Indexed: 05/27/2023]
Abstract
Transport-barrier relaxation oscillations in the presence of resonant magnetic perturbations are investigated using three-dimensional global fluid turbulence simulations from first principles at the edge of a tokamak. It is shown that resonant magnetic perturbations have a stabilizing effect on these relaxation oscillations and that this effect is due mainly to a modification of the pressure profile linked to the presence of both residual magnetic island chains and a stochastic layer.
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Affiliation(s)
- M Leconte
- France-Japan Magnetic Fusion Laboratory, Université de Provence, Case 321, 13397 Marseille Cedex 20, France
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26
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Fuhr G, Beyer P, Benkadda S, Garbet X. Evidence from numerical simulations of transport-barrier relaxations in tokamak edge plasmas in the presence of electromagnetic fluctuations. Phys Rev Lett 2008; 101:195001. [PMID: 19113276 DOI: 10.1103/physrevlett.101.195001] [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: 03/27/2008] [Indexed: 05/27/2023]
Abstract
The dynamics of transport barriers in fusion plasmas is studied in the presence of electromagnetic fluctuations. The work is based on numerical simulations using a new three-dimensional electromagnetic fluid turbulence code (EMEDGE3D). In these simulations, the transport-barrier exhibits intermittent relaxation cycles. It is found that magnetic fluctuations have a negligible influence on the relaxation process while the magnetic activity is enhanced during these relaxations, in agreement with experimental observations.
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Affiliation(s)
- G Fuhr
- France-Japan Magnetic Fusion Laboratory, LIA 336 CNRS/UMR 6633, CNRS-Université de Provence, Case 321, 13397 Marseille Cedex 20, France
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27
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Smolyakov AI, Garbet X, Ottaviani M. Geodesic plasma compressibility effects on the magnetic islands in a tokamak. Phys Rev Lett 2007; 99:055002. [PMID: 17930763 DOI: 10.1103/physrevlett.99.055002] [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: 08/24/2006] [Indexed: 05/25/2023]
Abstract
It is shown that the stability of rotating magnetic islands in a tokamak plasma is affected by plasma compressibility related to the geodesic curvature in an inhomogeneous magnetic field. A robust contribution has been found to the Rutherford evolution equation. It is shown that the sign of the geodesic curvature contribution is opposite to the sign of the polarization term. It is suggested that this mechanism plays a crucial role in the stability of small scale magnetic islands.
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Affiliation(s)
- A I Smolyakov
- Association Euratom-CEA, CEA/DSM/DRFC, Centre de Cadarache, 13108 Saint Paul lez Durance, France
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28
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Mantica P, Van Eester D, Garbet X, Imbeaux F, Laborde L, Mantsinen M, Marinoni A, Mazon D, Moreau D, Hawkes N, Joffrin E, Kiptily V, Pinches S, Salmi A, Sharapov S, Thyagaraja A, Voitsekhovitch I, de Vries P, Zastrow KD. Probing internal transport barriers with heat pulses in JET. Phys Rev Lett 2006; 96:095002. [PMID: 16606270 DOI: 10.1103/physrevlett.96.095002] [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: 05/10/2005] [Indexed: 05/08/2023]
Abstract
The first electron temperature modulation experiments in plasmas characterized by strong and long-lasting electron and ion internal transport barriers (ITB) have been performed in JET using ion cyclotron resonance heating in mode conversion scheme. The ITB is shown to be a well localized narrow layer with low heat diffusivity, characterized by subcritical transport and loss of stiffness. In addition, results from cold pulse propagation experiments suggest a second order transition process for ITB formation.
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Affiliation(s)
- P Mantica
- Istituto di Fisica del Plasma P.Caldirola, Associazione Euratom-ENEA-CNR, Milano, Italy
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29
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Garbet X. Introduction to Drift Wave Turbulence Modelling. Fusion Science and Technology 2006. [DOI: 10.13182/fst06-a1131] [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)
- X. Garbet
- Association Euratom-CEA, CEA/DSM/DRFC CEA-Cadarache, 13108 Saint Paul Lez Durance (France) Tel. +33 (0)4 42 25 49 29, e-mail:
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30
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Beyer P, Benkadda S, Fuhr-Chaudier G, Garbet X, Ghendrih P, Sarazin Y. Nonlinear dynamics of transport barrier relaxations in tokamak edge plasmas. Phys Rev Lett 2005; 94:105001. [PMID: 15783490 DOI: 10.1103/physrevlett.94.105001] [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: 06/04/2004] [Indexed: 05/24/2023]
Abstract
A new mechanism for intermittent relaxations of transport barriers is found by using three dimensional fluid turbulence simulations. This mechanism is generic since it only requires a stationary E x B shear flow. It is found here that if the flow shear increases faster than linearly with heating power, the relaxation frequency decreases with power. An analytical study reveals that this nonlinear dynamics is governed by a time delay for effective velocity shear stabilization.
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Affiliation(s)
- P Beyer
- Equipe Dynamique des Systèmes Complexes, LPIIM, CNRS-Université de Provence, Centre de St. Jérôme, Case 321, 13397 Marseille Cedex 20, France
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31
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Hoang GT, Bourdelle C, Garbet X, Artaud JF, Basiuk V, Bucalossi J, Clairet F, Fenzi-Bonizec C, Gil C, Ségui JL, Travère JM, Tsitrone E, Vermare L. Parametric dependence of turbulent particle transport in tore supra plasmas. Phys Rev Lett 2004; 93:135003. [PMID: 15524729 DOI: 10.1103/physrevlett.93.135003] [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: 04/16/2004] [Indexed: 05/24/2023]
Abstract
Steady state full noninductive current tore supra plasmas offer a unique opportunity to study the local parametric dependence of particle pinch velocity, in order to discriminate among different theories. Magnetic field shear is found to generate an inward pinch which is dominant in the gradient region (normalized radius 0.3</=r/a</=0.6). In contrast, the direction of the pinch in the plasma core (r/a</=0.3) is correlated with the electron temperature gradient length. The results are in agreement with both the turbulent theoretical and computational predictions.
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Affiliation(s)
- G T Hoang
- Euratom-CEA Association, CEA/DSM/DRFC, CEA Cadarache F-13108, Saint-Paul-Lez-Durance, France
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32
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Garbet X. Introduction to Drift Wave Turbulence Modeling. Fusion Science and Technology 2004. [DOI: 10.13182/fst04-a501] [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)
- X. Garbet
- Association Euratom-CEA, CEA/DSM/DRFC CEA-Cadarache, 13108 Saint Paul Lez Durance (France) Tel. +33 (0)4 42 25 49 29, e-mail:
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33
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Giruzzi G, Imbeaux F, Ségui JL, Garbet X, Huysmans G, Artaud JF, Bécoulet A, Hoang GT, Litaudon X, Maget P, Saoutic B. New tokamak plasma regime with stationary temperature oscillations. Phys Rev Lett 2003; 91:135001. [PMID: 14525311 DOI: 10.1103/physrevlett.91.135001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2003] [Indexed: 05/24/2023]
Abstract
During noninductively driven discharges in the Tore Supra tokamak, steady sinusoidal oscillations of the central electron temperature, lasting as long as 2 min, have been observed for the first time. Having no helical structure, they cannot be ascribed to any known MHD instability. The most plausible explanation of this new phenomenon is that the plasma current density and the electron temperature evolve as a nonlinearly coupled predator-prey system. This interpretation is supported by the numerical solution of coupled resistive current diffusion and heat transport equations.
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Affiliation(s)
- G Giruzzi
- Association Euratom-CEA, CEA/DSM/DRFC, CEA/Cadarache, 13108 St. Paul-lez-Durance, France
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34
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Garbet X, Garzotti L, Mantica P, Nordman H, Valovic M, Weisen H, Angioni C. Turbulent particle transport in magnetized plasmas. Phys Rev Lett 2003; 91:035001. [PMID: 12906422 DOI: 10.1103/physrevlett.91.035001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2003] [Indexed: 05/24/2023]
Abstract
Particle transport in magnetized plasmas is investigated with a fluid model of drift wave turbulence. An analytical calculation shows that magnetic field curvature and thermodiffusion drive an anomalous pinch. The curvature driven pinch velocity is consistent with the prediction of turbulence equipartition theory. The thermodiffusion flux is found to be directed inward for a small ratio of electron to ion pressure gradient, and it reverses its sign when increasing this ratio. Numerical simulations confirm that a turbulent particle pinch exists. It is mainly driven by curvature for equal ion and electron heat sources. The sign and relative weights of the curvature and thermodiffusion pinches are consistent with the analytical calculation.
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Affiliation(s)
- X Garbet
- Association Euratom-CEA sur la Fusion, CEA Cadarache, 13108 St Paul-Lez-Durance, France
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35
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Hoang GT, Bourdelle C, Pégourié B, Schunke B, Artaud JF, Bucalossi J, Clairet F, Fenzi-Bonizec C, Garbet X, Gil C, Guirlet R, Imbeaux F, Lasalle J, Loarer T, Lowry C, Travère JM, Tsitrone E. Particle pinch with fully noninductive lower hybrid current drive in Tore Supra. Phys Rev Lett 2003; 90:155002. [PMID: 12732041 DOI: 10.1103/physrevlett.90.155002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2002] [Indexed: 05/24/2023]
Abstract
Recently, plasmas exceeding 4 min have been obtained with lower hybrid current drive (LHCD) in Tore Supra. These LHCD plasmas extend for over 80 times the resistive current diffusion time with zero loop voltage. Under such unique conditions the neoclassical particle pinch driven by the toroidal electric field vanishes. Nevertheless, the density profile remains peaked for more than 4 min. For the first time, the existence of an inward particle pinch in steady-state plasma without toroidal electric field, much larger than the value predicted by the collisional neoclassical theory, is experimentally demonstrated.
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Affiliation(s)
- G T Hoang
- Euratom-CEA Association, CEA/DSM/DRFC, CEA Cadarache, F-13108 Saint-Paul-Lez-Durance, France
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36
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Figarella CF, Benkadda S, Beyer P, Garbet X, Voitsekhovitch I. Transport reduction by rotation shear in tokamak-edge turbulence. Phys Rev Lett 2003; 90:015002. [PMID: 12570621 DOI: 10.1103/physrevlett.90.015002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2002] [Revised: 09/30/2002] [Indexed: 05/24/2023]
Abstract
Effects of externally imposed and self-generated poloidal flows on turbulent transport in the edge region of a tokamak are investigated using 3D nonlinear global simulations of resistive pressure-gradient-driven turbulence. Transport reduction is found to be due to synergetic changes in the fluctuation amplitude and in the dephasing of the fluctuations. A scaling of the fluctuation level and turbulent diffusivity with E x B flow shear strength is deduced from these simulations. These scalings agree with recent experimental observations on edge biasing as well as with analytical models.
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Affiliation(s)
- C F Figarella
- Equipe Dynamique des Systèmes Complexes, LPIIM, UMR 6633 CNRS-Université de Provence, Centre St. Jérôme, Case 321, 13397 Marseille Cedex 20, France
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37
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Eriksson LG, Fourment C, Fuchs V, Litaudon X, Challis CD, Crisanti F, Esposito B, Garbet X, Giroud C, Hawkes N, Maget P, Mazon D, Tresset G. Discharges in the JET tokamak where the safety factor profile is identified as the critical factor for triggering internal transport barriers. Phys Rev Lett 2002; 88:145001. [PMID: 11955153 DOI: 10.1103/physrevlett.88.145001] [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: 09/22/2000] [Revised: 11/28/2001] [Indexed: 05/23/2023]
Abstract
Joint European Torus discharges which demonstrate the critical role the safety factor profile, q, can play in the formation of internal transport barriers (ITB) are examined. In these discharges, the target parameters, including the E x B flows, were kept virtually the same, except for the q profile. In a discharge with a nonmonotonic q, an ITB was triggered whereas a discharge with monotone q made no such transition. Thus, there is strong evidence that the q profile was the critical factor for the triggering of an ITB. Possible interpretations of this finding are discussed.
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Affiliation(s)
- L-G Eriksson
- Association EURATOM-CEA sur la Fusion Contrôlée, CEA Cadarache, F-13108 St. Paul lez Durance, France
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38
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Hoang GT, Bourdelle C, Garbet X, Giruzzi G, Aniel T, Ottaviani M, Horton W, Zhu P, Budny RV. Experimental determination of critical threshold in electron transport on Tore Supra. Phys Rev Lett 2001; 87:125001. [PMID: 11580517 DOI: 10.1103/physrevlett.87.125001] [Citation(s) in RCA: 8] [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: 11/17/2000] [Indexed: 05/23/2023]
Abstract
In Tore Supra plasmas with fast wave electron heating, a critical threshold in the electron temperature gradient (inverted DeltaT(e)) is clearly observed, i.e., a finite value of inverted DeltaT(e) for which the turbulent heat diffusivity vanishes. The radial profile of this critical gradient is experimentally determined from a set of discharges characterized by similar plasma parameters with fast wave powers ranging from 0.75 to 7.4 MW. The dependence of the electron heat flux on the gradient length is found to be offset linearly. The offset term increases linearly with the ratio of the local magnetic shear to the safety factor.
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Affiliation(s)
- G T Hoang
- Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA, CEA Cadarache, 13108 Saint-Paul-lez-Durance, France
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39
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Beyer P, Benkadda S, Garbet X, Diamond PH. Nondiffusive transport in tokamaks: three-dimensional structure of bursts and the role of zonal flows. Phys Rev Lett 2000; 85:4892-4895. [PMID: 11102144 DOI: 10.1103/physrevlett.85.4892] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2000] [Indexed: 05/23/2023]
Abstract
Large scale transport events are studied in simulations of resistive ballooning turbulence in a tokamak plasma. The spatial structure of the turbulent flux is analyzed, indicating radially elongated structures (streamers) at the low field side which are distorted by magnetic shear at different toroidal positions. The interplay between self-generated zonal flows and transport events is investigated, resulting in significant modifications of the frequency and the amplitude of bursts. The propagation of bursts is studied in the presence of a transport barrier generated by a strong shear flow.
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Affiliation(s)
- P Beyer
- Equipe Dynamique des Systemes Complexes, LPIIM, CNRS-Universite de Provence, Centre de St. Jerome, Case 321, 13397 Marseille Cedex 20, France
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Hoang GT, Bourdelle C, Garbet X, Antar G, Budny RV, Aniel T, Basiuk V, Becoulet A, Devynck P, Lasalle J, Martin G, Saint-Laurent F. Internal transport barrier with ion-cyclotron-resonance minority heating on tore supra. Phys Rev Lett 2000; 84:4593-4596. [PMID: 10990748 DOI: 10.1103/physrevlett.84.4593] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2000] [Indexed: 05/23/2023]
Abstract
Recently, reversed magnetic shear operation was performed using only ion-cyclotron-resonance frequency minority heating (ICRH) during current ramp-up. A wide region of reversed magnetic shear has been obtained. For the first time, an electron internal transport barrier sustained by ICRH is observed, with a dramatical drop of density fluctuations. This barrier was maintained, on the current flat top, for about 2 s.
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Affiliation(s)
- GT Hoang
- Departement de Recherches sur la Fusion Controlee, Association Euratom-CEA, CEA Cadarache, 13108 Saint-Paul-lez-Durance, France
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Beyer P, Benkadda S, Garbet X. Proper orthogonal decomposition and galerkin projection for a three-dimensional plasma dynamical system. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 2000; 61:813-823. [PMID: 11046328 DOI: 10.1103/physreve.61.813] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/1999] [Revised: 09/27/1999] [Indexed: 05/23/2023]
Abstract
A general method by which to investigate nonlinear dynamical systems close to a stability threshold is presented. This method combines a proper orthogonal decomposition and a subsequent Galerkin projection. This technique is applied to three-dimensional resistive ballooning plasma fluctuations in a tokamak. The corresponding dynamical system belongs to a large family of convective fluid systems including Rayleigh-Benard convection. A proper orthogonal decomposition of the fluctuating signal obtained by numerical simulation shows that the relevant modes are close to the linear (global) modes. The Galerkin projection provides a low-dimensional system that allows the study of shear flow generation, its subsequent fluctuation reduction, and the evolution to oscillating states.
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Affiliation(s)
- P Beyer
- Equipe Dynamique des Systemes Complexes, LPIIM, CNRS-Universite de Provence, Centre de St. Jeroinsertion markme, Case 321, 13397 Marseille Cedex 20, France
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Benkadda S, Verga A, Sen A, Garbet X. Characterization of coherent structures in tokamak edge turbulence. Phys Rev Lett 1994; 73:3403-3406. [PMID: 10057372 DOI: 10.1103/physrevlett.73.3403] [Citation(s) in RCA: 2] [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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Garbet X, Laurent L, Mourgues F, Roubin JP, Samain A, Zou XL, Chinardet J. Ionic instability thresholds in tokamaks. ACTA ACUST UNITED AC 1992. [DOI: 10.1063/1.860479] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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