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Galdon-Quiroga J, Birkenmeier G, Oyola P, Lindl H, Rodriguez-Gonzalez A, Anda G, Garcia-Munoz M, Herrmann A, Kalis J, Kaunert K, Lunt T, Refy D, Rohde V, Rueda-Rueda J, Sochor M, Tal B, Teschke M, Videla M, Viezzer E, Zoletnik S. First measurements of an imaging heavy ion beam probe at the ASDEX Upgrade tokamak. Rev Sci Instrum 2024; 95:013504. [PMID: 38206100 DOI: 10.1063/5.0175720] [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: 09/08/2023] [Accepted: 12/18/2023] [Indexed: 01/12/2024]
Abstract
The imaging heavy ion beam probe (i-HIBP) diagnostic has been successfully commissioned at ASDEX Upgrade. The i-HIBP injects a primary neutral beam into the plasma, where it is ionized, leading to a fan of secondary (charged) beams. These are deflected by the magnetic field of the tokamak and collected by a scintillator detector, generating a strike-line light pattern that encodes information on the density, electrostatic potential, and magnetic field of the plasma edge. The first measurements have been made, demonstrating the proof-of-principle of this diagnostic technique. A primary beam of 85/87Rb has been used with energies ranging between 60 and 72 keV and extracted currents up to 1.5 mA. The first signals have been obtained in experiments covering a wide range of parameter spaces, with plasma currents (Ip) between 0.2 and 0.8 MA and on-axis toroidal magnetic field (Bt) between 1.9 and 2.7 T. Low densities appear to be critical for the performance of the diagnostic, as signals are typically observed only when the line integrated density is below 2.0-3.0 × 1019 m-2 in the central interferometer chord, depending on the plasma shape. The strike line moves as expected when Ip is ramped, indicating that current measurements are possible. Additionally, clear dynamics in the intensity of the strike line are often observed, which might be linked to changes in the edge profile structure. However, the signal-to-background ratio of the signals is hampered by stray light, and the image guide degradation is due to neutron irradiation. Finally, simulations have been carried out to investigate the sensitivity of the expected signals to plasma density and temperature. The results are in qualitative agreement with the experimental observations, suggesting that the diagnostic is almost insensitive to fluctuations in the temperature profile, while the signal level is highly determined by the density profile due to the beam attenuation.
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Affiliation(s)
- J Galdon-Quiroga
- Department of Atomic, Molecular and Nuclear Physics, University of Seville, Seville, Spain
| | - G Birkenmeier
- Max Planck Institute for Plasma Physics, Garching, Germany
- TUM School of Natural Sciences, Physics Department, Technical University of Munich, 85748 Garching, Germany
| | - P Oyola
- Department of Atomic, Molecular and Nuclear Physics, University of Seville, Seville, Spain
| | - H Lindl
- Max Planck Institute for Plasma Physics, Garching, Germany
- TUM School of Natural Sciences, Physics Department, Technical University of Munich, 85748 Garching, Germany
| | - A Rodriguez-Gonzalez
- Department of Atomic, Molecular and Nuclear Physics, University of Seville, Seville, Spain
| | - G Anda
- Centre for Energy Research, Budapest, Hungary
| | - M Garcia-Munoz
- Department of Atomic, Molecular and Nuclear Physics, University of Seville, Seville, Spain
| | - A Herrmann
- Max Planck Institute for Plasma Physics, Garching, Germany
| | - J Kalis
- Max Planck Institute for Plasma Physics, Garching, Germany
- TUM School of Natural Sciences, Physics Department, Technical University of Munich, 85748 Garching, Germany
| | - K Kaunert
- Max Planck Institute for Plasma Physics, Garching, Germany
| | - T Lunt
- Max Planck Institute for Plasma Physics, Garching, Germany
| | - D Refy
- Centre for Energy Research, Budapest, Hungary
| | - V Rohde
- Max Planck Institute for Plasma Physics, Garching, Germany
| | - J Rueda-Rueda
- Department of Atomic, Molecular and Nuclear Physics, University of Seville, Seville, Spain
| | - M Sochor
- Max Planck Institute for Plasma Physics, Garching, Germany
| | - B Tal
- Max Planck Institute for Plasma Physics, Garching, Germany
| | - M Teschke
- Max Planck Institute for Plasma Physics, Garching, Germany
| | - M Videla
- Department of Atomic, Molecular and Nuclear Physics, University of Seville, Seville, Spain
| | - E Viezzer
- Department of Atomic, Molecular and Nuclear Physics, University of Seville, Seville, Spain
| | - S Zoletnik
- Centre for Energy Research, Budapest, Hungary
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2
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Estrada T, Hidalgo C. H-mode transition in the TJ-II stellarator plasmas. Philos Trans A Math Phys Eng Sci 2023; 381:20210229. [PMID: 36587823 DOI: 10.1098/rsta.2021.0229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 05/09/2022] [Indexed: 06/17/2023]
Abstract
Since the first H-mode transitions were observed in TJ-II plasmas in 2008, an extensive experimental effort has been done aiming at better physics understanding of confinement transitions. In this article, an overview of the main findings related to the L-H transition in TJ-II is presented including how the radial electric field is driven, what are the possible mechanisms for turbulence suppression and what are the related temporal and spatial scales that can impact the transition. The trigger of the L-H transition in TJ-II plasmas is found to be more correlated with the development of fluctuating [Formula: see text] flows than with steady-state [Formula: see text] effects, pointing to the role played by zonal flows in mediating the transition. Experimental evidence supporting the predator-prey relationship between turbulence and flows as the basis for the L-H transition, found for the first time in TJ-II, reinforces this conclusion. Besides, the reduction in the turbulent transport at the transition is detected at the barrier region but also in a wider radial range with weak or even zero [Formula: see text] flow shear, which points to other mechanisms beyond the turbulence suppression by local sheared flows. This article is part of a discussion meeting issue 'H-mode transition and pedestal studies in fusion plasmas'.
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Affiliation(s)
- Teresa Estrada
- Laboratorio Nacional de Fusión, CIEMAT, 28040 Madrid, Spain
| | - Carlos Hidalgo
- Laboratorio Nacional de Fusión, CIEMAT, 28040 Madrid, Spain
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Kawachi Y, Sasaki M, Kosuga Y, Terasaka K, Nishizawa T, Yamada T, Kasuya N, Moon C, Inagaki S. Spatiotemporal dynamics of high-wavenumber turbulence in a basic laboratory plasma. Sci Rep 2022; 12:19799. [PMID: 36509803 DOI: 10.1038/s41598-022-23559-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 11/02/2022] [Indexed: 12/14/2022] Open
Abstract
High-spatial resolution observation of high-wavenumber broadband turbulence is achieved by controlling the magnetic field to be relatively low and measuring with a azimuthally arranged multi-channel Langmuir array in a basic laboratory plasma. The observed turbulence consists of narrowband low-frequency fluctuations and broadband high-frequency turbulent fluctuations. The low-frequency fluctuations have a frequency of about 0.7 times the ion cyclotron frequency and a spatial scale of 1/10 of the ion inertial scale. In comparison, high-frequency fluctuations have a higher frequency than the ion cyclotron frequency and spatial scales of 1/10-1/40 of the ion inertial scale. Two-dimensional correlation analysis evaluates the spatial and temporal correlation lengths and reveals that the high-wavenumber broadband fluctuations have turbulent characteristics. The measurements give us further understanding of small scale turbulence in space and fusion plasmas.
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4
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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5
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Qiu H, Xiao D, Wu J, Wu S, Zhong C, Li X, Peng X, Yuan Y, Cai Q, Chang J, Hu T, Hu Z, Zhu Y. Initial measurement of ion nonextensive parameter with geodesic acoustic mode theory. Sci Rep 2022; 12:3412. [PMID: 35233047 PMCID: PMC8888714 DOI: 10.1038/s41598-022-07295-0] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 02/16/2022] [Indexed: 11/09/2022] Open
Abstract
The consideration of nonextensivity effects is crucial to the accurate diagnosis of plasma parameters; common plasma nonextensive parameters include electron nonextensive parameter and ion nonextensive parameter, and the former can be measured, while the ion nonextensive parameter cannot be measured yet. Here we show the measurement of ion nonextensive parameter of plasma based on the theory of nonextensive geodesic acoustic modes. We assume that the plasma to be measured can be described by nonextensive statistical mechanics, and on this basis, the nonextensive geodesic acoustic mode theory is established. Utilizing this theory, we have measured the ion nonextensive parameter [Formula: see text] which cannot be diagnosed even by a nonextensive single electric probe. Our research points out that the proposed measurement method of ion nonextensive parameter may play a role in plasma diagnosis and will help us to grasp the nonextensivity of plasma more precisely. We hope the proposed method of ion nonextensive parameter diagnosis based on the nonextensive geodesic acoustic mode theory can be the starting point of more complex ion nonextensive parameter diagnosis methods. In addition, the measurement of ion nonextensive parameter is closely related to the study of various plasma waves, instabilities, turbulence and abnormal transport, and a defined and quantitative test of nonextensive geodesic acoustic mode theory will bound up deeply with such developments.
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Affiliation(s)
- Huibin Qiu
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China. .,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China.
| | - Donghua Xiao
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Junjie Wu
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Shengfa Wu
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Chengjie Zhong
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Xiaobin Li
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Xingkun Peng
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Youlong Yuan
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Qilong Cai
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Jinming Chang
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Tianyi Hu
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Zuozhi Hu
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
| | - Yuqing Zhu
- Jiangxi Province Key Laboratory of Fusion and Information Control, Department of Physics, Nanchang University, Nanchang, 330031, China.,NCU-ASIPP Magnetic Confinement Fusion Joint Lab, Institute of Fusion Energy and Plasma Application, Nanchang University, Nanchang, 330031, China
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6
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Melnikov A. Evolution of Heavy Ion Beam Probing from the Origins to Study of Symmetric Structures in Fusion Plasmas. Symmetry (Basel) 2021; 13:1367. [DOI: 10.3390/sym13081367] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The overview discusses development of the unique fusion plasma diagnostics—Heavy Ion Beam Probing (HIBP) in application to toroidal magnetic plasma devices. The basis of the HIBP measurements of the plasma electric potential and processing of experimental data are considered. Diagnostic systems for probing plasma in tokamaks TM-4, TJ-1, TUMAN-3M and T-10, stellarators WEGA, TJ-II and Uragan-2M are presented. Promising results of the HIBP projects for various existing modern machines, such as TCV, TCABR, MAST, COMPASS, GLOBUS-M2, T-15 MD and W7-X and the international fusion tokamak reactor ITER are given. Results from two machines with similar size and plasma parameters, but with different types of the magnetic con-figuration: axisymmetric tokamak T-10 and helically symmetric stellarator TJ-II are compared. The results of studies of stationary potential profiles and oscillations in the form of quasimonochromatic and broadband fluctuations, turbulent particle flux, fluctuations of density and poloidal magnetic field are presented. The properties of symmetric structures—zonal flows and geodesic acoustic modes of plasma oscillations as well as Alfvén Eigenmodes excited by fast particles from neutral beam injection heating are described. General trends in the behavior of electric potential and turbulence in magnetized fusion plasmas are revealed.
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Ido T, Fujisawa A, Takemura K, Kobayashi TK, Nishimura D, Kasuya N, Fukuyama A, Moon C, Yamasaki K, Inagaki S, Nagashima Y, Yamada T. Conceptual design of heavy ion beam probes on the PLATO tokamak. Rev Sci Instrum 2021; 92:053553. [PMID: 34243249 DOI: 10.1063/5.0041814] [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: 12/25/2020] [Accepted: 05/05/2021] [Indexed: 06/13/2023]
Abstract
Heavy ion beam probe (HIBP) systems have been designed for the new tokamak, PLATO [A. Fujisawa, AIP Conf. Proc. 1993, 020011 (2018)]. The designs have been completed, and the installations are in progress. Two HIBPs are being installed in toroidal sections 180° apart to investigate long-range correlations in the toroidal direction. Each HIBP consists of an injection beamline and a detection beamline as usual. Yet, one of the HIBPs is equipped with an additional detection beamline; the measurement positions of its two detection beamlines can be placed on almost the same magnetic surface yet at poloidal angles that differ by ∼180°. The use of three detection beamlines allows us to investigate spatial asymmetry and long-range correlations in both the toroidal and poloidal directions, simultaneously. The detected beam intensity is expected to be enough for turbulence measurements in almost the entire plasma region when the electron density is up to 1 × 1019 m-3 by selecting appropriate ion species for the probe beam. Each detector has three channels 10 mm apart, allowing measurement of local structures of micro-scale turbulence. Therefore, using the HIBPs on the PLATO tokamak will enable both local and global properties of plasma turbulence to be investigated, simultaneously.
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Affiliation(s)
- T Ido
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
| | - A Fujisawa
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
| | - K Takemura
- Department of Applied Energy, Nagoya University, Furocho, Chikusa, Nagoya 464-8603, Japan
| | - T-K Kobayashi
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
| | - D Nishimura
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
| | - N Kasuya
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
| | - A Fukuyama
- Department of Nuclear Engineering, Kyoto University, Nisikyo-ku, Kyoto 615-8540, Japan
| | - C Moon
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
| | - K Yamasaki
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
| | - S Inagaki
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
| | - Y Nagashima
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
| | - T Yamada
- Faculty of Arts and Science, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
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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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9
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Veranda M, Bonfiglio D, Cappello S, Chacòn L, Escande DF, di Giannatale G. Helical magnetic self-organization of plasmas in toroidal pinches with transport barriers formation. EPJ Web Conf 2020. [DOI: 10.1051/epjconf/202023000013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Nonlinear MHD modeling of toroidal pinch configurations for hot plasma magnetic confinement describes several features of the helical self-organization process, which is observed in both reversed-field pinches and tokamaks. It can also give a hint on why transport barriers are formed, by far one of the more interesting observations in experiments. The work tackles these two topics, helical self-organization and transport barriers formation - adding further information and examples to the results already presented in [Veranda, et al, Nucl.Fus. 60 016007 (2020)]. Regarding the topic of helical self-organization, a synthesis of the results obtained by a 3D nonlinear viscoresistive magnetohydrodynamics model will be presented. Modelling predicts a technique to “channel” reversed-field pinches into a chosen macroscopic helical shape and also predicts that the features of such helical self-organization, studied in the RFX-mod experiment in Padova, depend on two parameters only: plasma dissipation coefficients and edge radial magnetic field. They can be exploited to calm the natural tendency of reversed-field pinches to a “sawtoothing” dynamics, i.e. by decreasing visco-resistive dissipation and using helical edge fields not resonating with the plasma safety factor. Regarding the MHD description of the process of formation of transport barriers by magnetic chaos healing, we will describe the computation of Lagrangian structures, hidden in the weakly stochastic behaviour of magnetic field lines, acting as barriers to the transport. The radial position of such structures is observed to correspond to higher gradients of magnetic field lines connection length to the edge: this provides a further indication of their possible role in the formation of electron temperature barriers.
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10
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Nishizawa T, Almagri AF, Anderson JK, Goodman W, Pueschel MJ, Nornberg MD, Ohshima S, Sarff JS, Terry PW, Williams ZR. Direct Measurement of a Toroidally Directed Zonal Flow in a Toroidal Plasma. Phys Rev Lett 2019; 122:105001. [PMID: 30932630 DOI: 10.1103/physrevlett.122.105001] [Citation(s) in RCA: 1] [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: 12/25/2018] [Revised: 02/16/2019] [Indexed: 06/09/2023]
Abstract
Zonal flow appears in toroidal, magnetically confined plasmas as part of the self-regulated interaction of turbulence and transport processes. For toroidal plasmas having a strong toroidal magnetic field, the zonal flow is predominately poloidally directed. This Letter reports the first observation of a zonal flow that is toroidally directed. The measurements are made just inside the last closed flux surface of reversed field pinch plasmas that have a dominant poloidal magnetic field. A limit cycle oscillation between the strength of the zonal flow and the amplitude of plasma potential fluctuations is observed, which provides evidence for the self-regulation characteristic of drift-wave-type plasma turbulence. The measurements help advance understanding and gyrokinetic modeling of toroidal plasmas in the pursuit of fusion energy.
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Affiliation(s)
- T Nishizawa
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - A F Almagri
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J K Anderson
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - W Goodman
- Electrical Engineering Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M J Pueschel
- Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712, USA
| | - M D Nornberg
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - S Ohshima
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - J S Sarff
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - P W Terry
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Z R Williams
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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11
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Shimizu A, Fujisawa A, Ohshima S, Nakano H, Minami T, Isobe M, Okamura S, Matsuoka K. Density profile measurement with a heavy ion beam probe in a toroidal plasma of the compact helical system. Rev Sci Instrum 2018; 89:113507. [PMID: 30501308 DOI: 10.1063/1.5039571] [Citation(s) in RCA: 2] [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: 05/09/2018] [Accepted: 10/19/2018] [Indexed: 06/09/2023]
Abstract
A possibility of electron density measurements with heavy ion beam probes (HIBPs) has been demonstrated, along with their capability to measure the potential and magnetic field. A method has been proposed to reconstruct the electron density profile [A. Fujisawa et al., Rev. Sci. Instrum. 74, 3335 (2003)]. In the method, the profile of secondary beam currents is converted into a local density profile by taking into account local brightness and so-called path integral effects which mean the effect of beam attenuation along the beam orbit. Here the article presents the HIBP measurement of the electron density profile after the proposed method was first applied on the real experimental data of compact helical system plasmas. In the real application, the hollow density and the peaked profiles are successfully obtained with sufficiently high temporal resolution (a few ms), in accordance with the electron density profile measured with Thomson scattering for electron cyclotron resonance heating and neutral beam injection plasmas.
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Affiliation(s)
- A Shimizu
- National Institute for Fusion Science, Oroshi, Toki, Gifu 509-5292, Japan
| | - A Fujisawa
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-Kohen, Kasuga 816-8580, Japan
| | - S Ohshima
- Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - H Nakano
- National Institute for Fusion Science, Oroshi, Toki, Gifu 509-5292, Japan
| | - T Minami
- Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - M Isobe
- National Institute for Fusion Science, Oroshi, Toki, Gifu 509-5292, Japan
| | - S Okamura
- National Institute for Fusion Science, Oroshi, Toki, Gifu 509-5292, Japan
| | - K Matsuoka
- National Institute for Fusion Science, Oroshi, Toki, Gifu 509-5292, Japan
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12
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Nishizawa T, Almagri AF, Goodman W, Ohshima S, Sarff JS. Development of a multi-channel capacitive probe for electric field measurements with fine spatial and high time resolution. Rev Sci Instrum 2018; 89:10J118. [PMID: 30399956 DOI: 10.1063/1.5035093] [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: 04/12/2018] [Accepted: 06/07/2018] [Indexed: 06/08/2023]
Abstract
A capacitive probe [Tan et al., Rev. Sci. Instrum. 88, 023502 (2017)] is one of a few diagnostics that is directly sensitive to the plasma potential. Using this diagnostic technique, a Multi-channel Linear Capacitive Probe (MLCP) is developed for turbulence measurements. The MLCP has 10 spatial channels and provides 9 points of radial electric field measurements simultaneously with a spatial step of 7 mm. A new readout circuit and a correction technique for low frequency attenuation are also developed to achieve the required spatial and time resolution. A performance test of the MLCP using a reversed field pinch plasma confirms that the MLCP resolves sub-centimeter structures of the equilibrium radial electric field profile and fluctuations up to 680 kHz.
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Affiliation(s)
- T Nishizawa
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - A F Almagri
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - W Goodman
- Electrical Engineering Department, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - S Ohshima
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - J S Sarff
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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13
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Abstract
Inhomogeneous drift-wave turbulence can be modeled as an effective plasma where drift waves act as quantumlike particles and the zonal-flow velocity serves as a collective field through which they interact. This effective plasma can be described by a Wigner-Moyal equation (WME), which generalizes the quasilinear wave-kinetic equation (WKE) to the full-wave regime, i.e., resolves the wavelength scale. Unlike waves governed by manifestly quantumlike equations, whose WMEs can be borrowed from quantum mechanics and are commonly known, drift waves have Hamiltonians very different from those of conventional quantum particles. This causes unusual phase-space dynamics that is typically not captured by the WKE. We demonstrate how to correctly model this dynamics with the WME instead. Specifically, we report full-wave phase-space simulations of the zonal-flow formation (zonostrophic instability), deterioration (tertiary instability), and the so-called predator-prey oscillations. We also show how the WME facilitates analysis of these phenomena, namely, (i) we show that full-wave effects critically affect the zonostrophic instability, particularly its nonlinear stage and saturation; (ii) we derive the tertiary-instability growth rate; and (iii) we demonstrate that, with full-wave effects retained, the predator-prey oscillations do not require zonal-flow collisional damping, contrary to previous studies. We also show how the famous Rayleigh-Kuo criterion, which has been missing in wave-kinetic theories of drift-wave turbulence, emerges from the WME.
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Affiliation(s)
- Hongxuan Zhu
- Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544, USA.,Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - Yao Zhou
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - D E Ruiz
- Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185, USA
| | - I Y Dodin
- Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544, USA.,Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
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14
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Kobayashi T, Sasaki M, Ido T, Kamiya K, Miura Y, Nagashima Y, Ida K, Inagaki S, Fujisawa A, Itoh SI, Itoh K. Quantification of Turbulent Driving Forces for the Geodesic Acoustic Mode in the JFT-2M Tokamak. Phys Rev Lett 2018; 120:045002. [PMID: 29437414 DOI: 10.1103/physrevlett.120.045002] [Citation(s) in RCA: 1] [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: 10/06/2017] [Revised: 11/29/2017] [Indexed: 06/08/2023]
Abstract
We investigate spatial structures of turbulence and turbulent transport modulated by the geodesic acoustic mode (GAM), from which the excitation mechanism of the GAM is discussed. The GAM is found to be predominantly excited through a localized Reynolds stress force, rather than the dynamic shearing force. The evaluated growth rate is larger than the linear damping coefficients and is on the same order of magnitude as the effective growth rate evaluated from time evolution in the GAM kinetic energy.
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Affiliation(s)
- T Kobayashi
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - M Sasaki
- Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580, Japan
| | - T Ido
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - K Kamiya
- National Institutes for Quantum and Radiological Science and Technology, Naka 311-0193, Japan
| | - Y Miura
- Japan Atomic Energy Agency, Naka 311-0193, Japan
| | - Y Nagashima
- Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580, Japan
| | - K Ida
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580, Japan
| | - S Inagaki
- Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580, Japan
| | - A Fujisawa
- Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580, Japan
| | - S-I Itoh
- Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580, Japan
| | - K Itoh
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580, Japan
- Institute of Science and Technology Research, Chubu University, Kasugai 487-8501, Japan
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15
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Nakata M, Nunami M, Sugama H, Watanabe TH. Isotope Effects on Trapped-Electron-Mode Driven Turbulence and Zonal Flows in Helical and Tokamak Plasmas. Phys Rev Lett 2017; 118:165002. [PMID: 28474924 DOI: 10.1103/physrevlett.118.165002] [Citation(s) in RCA: 3] [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: 11/11/2016] [Indexed: 06/07/2023]
Abstract
Impacts of isotope ion mass on trapped-electron-mode (TEM)-driven turbulence and zonal flows in magnetically confined fusion plasmas are investigated. Gyrokinetic simulations of TEM-driven turbulence in three-dimensional magnetic configuration of helical plasmas with hydrogen isotope ions and real-mass kinetic electrons are realized for the first time, and the linear and the nonlinear nature of the isotope and collisional effects on the turbulent transport and zonal-flow generation are clarified. It is newly found that combined effects of the collisional TEM stabilization by the isotope ions and the associated increase in the impacts of the steady zonal flows at the near-marginal linear stability lead to the significant transport reduction with the opposite ion mass dependence in comparison to the conventional gyro-Bohm scaling. The universal nature of the isotope effects on the TEM-driven turbulence and zonal flows is verified for a wide variety of toroidal plasmas, e.g., axisymmetric tokamak and non-axisymmetric helical or stellarator systems.
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Affiliation(s)
- Motoki Nakata
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan The Graduate University for Advanced Studies, Toki 509-5292, Japan
| | - Masanori Nunami
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan The Graduate University for Advanced Studies, Toki 509-5292, Japan
| | - Hideo Sugama
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan The Graduate University for Advanced Studies, Toki 509-5292, Japan
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16
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Ida K, Miura Y, Ido T, Nagashima Y, Shinohara K. Studies of Radial Electric Field Formation and Its Effect on Fluctuations and Transport Barriers in the JFT-2M Tokamak. Fusion Science and Technology 2017. [DOI: 10.13182/fst06-a1091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [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)
- K. Ida
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 507-5292, Japan
| | - Y. Miura
- Japan Atomic Energy Research Institute, Naka Fusion Research Establishment, Mukouyama 801-1 Naka City, Ibaraki 311-0193, Japan
| | - T. Ido
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 507-5292, Japan
| | - Y. Nagashima
- Research Institute for Applied Mechanics, Kyushu University, Japan
| | - K. Shinohara
- Japan Atomic Energy Research Institute, Naka Fusion Research Establishment, Mukouyama 801-1 Naka City, Ibaraki 311-0193, Japan
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17
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Affiliation(s)
- A. I. Kislyakov
- Ioffe Physical-Technical Institute of Russian Academy of Sciences 194021, St. Petersburg, Russia
| | - A. J. H. Donné
- Association EURATOM-FOM, FOM Institute for Plasma Physics Rijnhuizen Partner in the Trilateral Euregio Cluster, P.O. Box 1207, NL-3430 BE, Nieuwegein, The Netherlands
| | - L. I. Krupnik
- Institute of Plasma Physics, NSC KIPT, 310108, Kharkov, Ukraine
| | - S. S. Medley
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543
| | - M. P. Petrov
- Ioffe Physical-Technical Institute of Russian Academy of Sciences 194021, St.-Petersburg, Russia
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18
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Kakati B, Pradhan S, Dhongde J, Semwal P, Yohan K, Banaudha M. Edge transport and fluctuation induced turbulence characteristics in early SST-1 plasma. Fusion Engineering and Design 2017. [DOI: 10.1016/j.fusengdes.2016.12.041] [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] [Indexed: 11/16/2022]
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19
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Inagaki S, Kobayashi T, Kosuga Y, Itoh SI, Mitsuzono T, Nagashima Y, Arakawa H, Yamada T, Miwa Y, Kasuya N, Sasaki M, Lesur M, Fujisawa A, Itoh K. A Concept of Cross-Ferroic Plasma Turbulence. Sci Rep 2016; 6:22189. [PMID: 26917218 PMCID: PMC4768185 DOI: 10.1038/srep22189] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 02/08/2016] [Indexed: 11/18/2022] Open
Abstract
The variety of scalar and vector fields in laboratory and nature plasmas is formed by plasma turbulence. Drift-wave fluctuations, driven by density gradients in magnetized plasmas, are known to relax the density gradient while they can generate flows. On the other hand, the sheared flow in the direction of magnetic fields causes Kelvin-Helmholtz type instabilities, which mix particle and momentum. These different types of fluctuations coexist in laboratory and nature, so that the multiple mechanisms for structural formation exist in extremely non-equilibrium plasmas. Here we report the discovery of a new order in plasma turbulence, in which chained structure formation is realized by cross-interaction between inhomogeneities of scalar and vector fields. The concept of cross-ferroic turbulence is developed, and the causal relation in the multiple mechanisms behind structural formation is identified, by measuring the relaxation rate and dissipation power caused by the complex turbulence-driven flux.
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Affiliation(s)
- S Inagaki
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580, Japan.,Research Center for Plasma Turbulence, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580 Japan
| | - T Kobayashi
- National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-city, Gifu 509-5292, Japan
| | - Y Kosuga
- Institute for Advanced Study, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, 812-8581, Fukuoka Japan
| | - S-I Itoh
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580, Japan.,Research Center for Plasma Turbulence, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580 Japan
| | - T Mitsuzono
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580, Japan
| | - Y Nagashima
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580, Japan.,Research Center for Plasma Turbulence, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580 Japan
| | - H Arakawa
- Teikyo University, 6-22 Misaki-machi, Omuta-city, Fukuoka 836-8505, Japan
| | - T Yamada
- Faculty of Arts and Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Y Miwa
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580, Japan
| | - N Kasuya
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580, Japan.,Research Center for Plasma Turbulence, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580 Japan
| | - M Sasaki
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580, Japan.,Research Center for Plasma Turbulence, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580 Japan
| | - M Lesur
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580, Japan
| | - A Fujisawa
- Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580, Japan.,Research Center for Plasma Turbulence, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580 Japan
| | - K Itoh
- Research Center for Plasma Turbulence, Kyushu University, 6-1 Kasuga-Koen, Kasuga-city, Fukuoka 816-8580 Japan.,National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-city, Gifu 509-5292, Japan
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20
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Hillesheim JC, Delabie E, Meyer H, Maggi CF, Meneses L, Poli E. Stationary Zonal Flows during the Formation of the Edge Transport Barrier in the JET Tokamak. Phys Rev Lett 2016; 116:065002. [PMID: 26918997 DOI: 10.1103/physrevlett.116.065002] [Citation(s) in RCA: 3] [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: 10/21/2015] [Indexed: 06/05/2023]
Abstract
High spatial resolution Doppler backscattering measurements in JET have enabled new insights into the development of the edge Er. We observe fine-scale spatial structures in the edge Er well with a wave number krρi≈0.4-0.8, consistent with stationary zonal flows, the characteristics of which vary with density. The zonal flow amplitude and wavelength both decrease with local collisionality, such that the zonal flow E×B shear increases. Above the minimum of the L-H transition power threshold dependence on density, the zonal flows are present during L mode and disappear following the H-mode transition, while below the minimum they are reduced below measurable amplitude during L mode, before the L-H transition.
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Affiliation(s)
- J C Hillesheim
- CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom
| | - E Delabie
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - H Meyer
- CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom
| | - C F Maggi
- CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom
| | - L Meneses
- Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
| | - E Poli
- Max-Planck-institut fur Plasmaphysik, Garching, Germany
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21
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Hsu PC, Diamond PH, Tobias SM. Nonperturbative mean-field theory for minimum enstrophy relaxation. Phys Rev E Stat Nonlin Soft Matter Phys 2015; 91:053024. [PMID: 26066265 DOI: 10.1103/physreve.91.053024] [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: 11/21/2014] [Indexed: 06/04/2023]
Abstract
The dual cascade of enstrophy and energy in quasi-two-dimensional turbulence strongly suggests that a viscous but otherwise potential vorticity (PV) conserving system decays selectively toward a state of minimum potential enstrophy. We derive a nonperturbative mean field theory for the dynamics of minimum enstrophy relaxation by constructing an expression for PV flux during the relaxation process. The theory is used to elucidate the structure of anisotropic flows emerging from the selective decay process. This structural analysis of PV flux is based on the requirements that the mean flux of PV dissipates total potential enstrophy but conserves total fluid kinetic energy. Our results show that the structure of PV flux has the form of a sum of a positive definite hyperviscous and a negative or positive viscous transport of PV. Transport parameters depend on zonal flow and turbulence intensity. Turbulence spreading is shown to be related to PV mixing via the link of turbulence energy flux to PV flux. In the relaxed state, the ratio of the PV gradient to zonal flow velocity is homogenized. This homogenized quantity sets a constraint on the amplitudes of PV and zonal flow in the relaxed state. A characteristic scale is defined by the homogenized quantity and is related to a variant of the Rhines scale. This relaxation model predicts a relaxed state with a structure which is consistent with PV staircases, namely, the proportionality between mean PV gradient and zonal flow strength.
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Affiliation(s)
- Pei-Chun Hsu
- CASS and Department of Physics, University of California San Diego, La Jolla, California 92093-0424, USA
| | - P H Diamond
- CASS and Department of Physics, University of California San Diego, La Jolla, California 92093-0424, USA
| | - S M Tobias
- Department of Applied Mathematics, University of Leeds, Leeds, LS2 9JT, United Kingdom
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22
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Matsuo K, Iguchi H, Okamura S, Matsuoka K. Investigation of a high spatial resolution method based on polar coordinate maximum entropy method for analyzing electron density fluctuation data measured by laser phase contrast. Rev Sci Instrum 2012; 83:013501. [PMID: 22299945 DOI: 10.1063/1.3673636] [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] [Indexed: 05/31/2023]
Abstract
Laser phase contrast is a powerful diagnostic method to determine the spatial distribution of electron density fluctuations in magnetically confined plasmas, although its applicability depends on magnetic field configurations. The spatial resolution of fluctuations is linked with the resolution of the propagation direction that is derived from the two-dimensional spectral analysis of the wavenumber for the fluctuations. The method was applied to fluctuation measurements in a compact helical system. In order to improve the resolution of the propagation direction with a relatively small number of data points, the maximum entropy method with polar coordinates was employed. A spatial resolution of the order of 1 cm was obtained, which is satisfactory in a plasma with a 20 cm minor radius.
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Affiliation(s)
- K Matsuo
- Fukuoka Institute of Technology, Fukuoka, Japan
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23
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Inagaki S, Tokuzawa T, Itoh K, Ida K, Itoh SI, Tamura N, Sakakibara S, Kasuya N, Fujisawa A, Kubo S, Shimozuma T, Ido T, Nishimura S, Arakawa H, Kobayashi T, Tanaka K, Nagayama Y, Kawahata K, Sudo S, Yamada H, Komori A. Observation of long-distance radial correlation in toroidal plasma turbulence. Phys Rev Lett 2011; 107:115001. [PMID: 22026678 DOI: 10.1103/physrevlett.107.115001] [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: 07/09/2010] [Indexed: 05/31/2023]
Abstract
This Letter presents the discovery of macroscale electron temperature fluctuations with a long radial correlation length comparable to the plasma minor radius in a toroidal plasma. Their spatiotemporal structure is characterized by a low frequency of ∼1-3 kHz, ballistic radial propagation, a poloidal or toroidal mode number of m/n=1/1 (or 2/1), and an amplitude of ∼2% at maximum. Nonlinear coupling between the long-range fluctuations and the microscopic fluctuations is identified. A change of the amplitude of the long-range fluctuation is transmitted across the plasma radius at the velocity which is of the order of the drift velocity.
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Affiliation(s)
- S Inagaki
- Research Institute for Applied Mechanics, Kyushu University, Fukuoka 816-8580, Japan
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24
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Manz P, Ramisch M, Stroth U. Long-range correlations induced by the self-regulation of zonal flows and drift-wave turbulence. Phys Rev E 2011; 82:056403. [PMID: 21230598 DOI: 10.1103/physreve.82.056403] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 10/08/2010] [Indexed: 11/07/2022]
Abstract
By means of a unique probe array, the interaction between zonal flows and broad-band drift-wave turbulence has been investigated experimentally in a magnetized toroidal plasma. Homogeneous potential fluctuations on a magnetic flux surface, previously reported as long range correlations, could be traced back to a predator-prey-like interaction between the turbulence and the zonal flow. At higher frequency the nonlocal transfer of energy to the zonal flow is dominant and the low-frequency oscillations are shown to result from the reduced turbulence activity due to this energy loss. This self-regulation process turns out to be enhanced with increased background shear flows.
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Affiliation(s)
- P Manz
- Center for Energy Research, University of California at San Diego, San Diego, California 92093, USA
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25
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Sokolov V, Wei X, Sen AK. Experimental Observation of Zonal Flow and Its Scalings in Axisymmetric Magnetic Field. Fusion Science and Technology 2011. [DOI: 10.13182/fst11-a11596] [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)
- V. Sokolov
- Plasma Research Laboratory, Columbia University 1300 Mudd Bldg., 500W, 120th Street, New York, NY, 10027,
| | - X. Wei
- Plasma Research Laboratory, Columbia University 1300 Mudd Bldg., 500W, 120th Street, New York, NY, 10027,
| | - A. K. Sen
- Plasma Research Laboratory, Columbia University 1300 Mudd Bldg., 500W, 120th Street, New York, NY, 10027,
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26
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Yamada T, Itoh SI, Inagaki S, Nagashima Y, Kasuya N, Kamataki K, Arakawa H, Kobayashi T, Yagi M, Fujisawa A, Itoh K. Observation of quasi-two-dimensional nonlinear interactions in a drift-wave streamer. Phys Rev Lett 2010; 105:225002. [PMID: 21231392 DOI: 10.1103/physrevlett.105.225002] [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: 09/16/2010] [Indexed: 05/30/2023]
Abstract
A streamer, which is a bunching of drift-wave fluctuations, and its mediator, which generates the streamer by coupling with other fluctuations, have been observed in a cylindrical magnetized plasma. Their radial structures were investigated in detail by using the biphase analysis. Their quasi-two-dimensional structures were revealed to be equivalent with a pair of fast and slow modes predicted by a nonlinear Schrödinger equation based on the Hasegawa-Mima model.
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Affiliation(s)
- T Yamada
- Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan.
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27
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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. Rev Sci Instrum 2010; 81:10E137. [PMID: 21033998 DOI: 10.1063/1.3496980] [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] [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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28
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Ghim Kim YC, Field AR, Zoletnik S, Dunai D. Calculation of spatial response of 2D beam emission spectroscopy diagnostic on MAST. Rev Sci Instrum 2010; 81:10D713. [PMID: 21033906 DOI: 10.1063/1.3479037] [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] [Indexed: 05/30/2023]
Abstract
The beam emission spectroscopy (BES) turbulence diagnostic on MAST is to be upgraded in June 2010 from a one-dimensional trial system to a two-dimensional imaging system (8 radial×4 poloidal channels) based on a newly developed avalanche photodiode array camera. The spatial resolution of the new system is calculated in terms of the point spread function to account for the effects of field-line curvature, observation geometry, the finite lifetime of the excited state of the beam atoms, and beam attenuation and divergence. It is found that the radial spatial resolution is ∼2-3 cm and the poloidal spatial resolution ∼1-5 cm depending on the radial viewing location. The absolute number of detected photons is also calculated, hence the photon noise level can be determined.
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Affiliation(s)
- Young-Chul Ghim Kim
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP, United Kingdom
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29
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Itoh K, Sugama H, Watanabe TH, Yamagishi O, Toda S, Kasuya N, Kanno R, Nunami M. Microinstabilities, Turbulent Transport, and Structure Formation in Helical Plasmas. Fusion Science and Technology 2010. [DOI: 10.13182/fst10-a10812] [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)
- K. Itoh
- National Institute for Fusion Science, Toki 509-5292, Japan
| | - H. Sugama
- National Institute for Fusion Science, Toki 509-5292, Japan
| | - T.-H. Watanabe
- National Institute for Fusion Science, Toki 509-5292, Japan
| | - O. Yamagishi
- National Institute for Fusion Science, Toki 509-5292, Japan
| | - S. Toda
- National Institute for Fusion Science, Toki 509-5292, Japan
| | - N. Kasuya
- National Institute for Fusion Science, Toki 509-5292, Japan
| | - R. Kanno
- National Institute for Fusion Science, Toki 509-5292, Japan
| | - M. Nunami
- National Institute for Fusion Science, Toki 509-5292, Japan
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30
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Terasaka K, Yoshimura S, Ogiwara K, Aramaki M, Tanaka MY. Experimental studies on ion acceleration and stream line detachment in a diverging magnetic field. Phys Plasmas 2010; 17:072106. [PMID: 20838424 PMCID: PMC2931599 DOI: 10.1063/1.3457139] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Accepted: 06/04/2010] [Indexed: 05/29/2023]
Abstract
The flow structure of ions in a diverging magnetic field has been experimentally studied in an electron cyclotron resonance plasma. The flow velocity field of ions has been measured with directional Langmuir probes calibrated with the laser induced fluorescence spectroscopy. For low ion-temperature plasmas, it is concluded that the ion acceleration due to the axial electric field is important compared with that of gas dynamic effect. It has also been found that the detachment of ion stream line from the magnetic field line takes place when the parameter |f(ci)L(B)∕V(i)| becomes order unity, where f(ci), L(B), and V(i) are the ion cyclotron frequency, the characteristic scale length of magnetic field inhomogeneity, and the ion flow velocity, respectively. In the detachment region, a radial electric field is generated in the plasma and the ions move straight with the E×B rotation driven by the radial electric field.
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31
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Sokolov V, Wei X, Sen AK. Feedback assisted experimental studies of zonal-flow saturation and scalings. Phys Rev Lett 2010; 104:025002. [PMID: 20366603 DOI: 10.1103/physrevlett.104.025002] [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: 04/10/2008] [Indexed: 05/29/2023]
Abstract
The unique complementary roles of ion acoustic damping and zonal-flow (ZF) shearing in the saturation of ion temperature gradient modes (ITG) has been experimentally demonstrated using stabilizing and destabilizing feedback techniques. This was done in the context of experimental studies of ZF scalings over a wide parameter range. Furthermore, the scaling of ZF amplitude with that of ITG via increasing ITG drive through increasing ion temperature gradient via rf heating reveals an expected monotonic behavior.
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Affiliation(s)
- V Sokolov
- Plasma Research Laboratory, Columbia University, New York, New York 10027, USA
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32
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Liu AD, Lan T, Yu CX, Zhao HL, Yan LW, Hong WY, Dong JQ, Zhao KJ, Qian J, Cheng J, Duan XR, Liu Y. Characterizations of low-frequency zonal flow in the edge plasma of the HL-2A tokamak. Phys Rev Lett 2009; 103:095002. [PMID: 19792802 DOI: 10.1103/physrevlett.103.095002] [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: 01/18/2009] [Indexed: 05/28/2023]
Abstract
A low-frequency (<4 kHz), poloidally and toroidally symmetrical potential structure that peaks near zero frequency is observed in the edge plasma of the HL-2A tokamak. The axisymmetry structure exhibits a radial coherence length less than 1 cm. These characteristics are consistent with the theoretically predicted low-frequency zonal flows (LFZF). The radial wave-number frequency spectra of the LFZF show that the LFZF packets propagate both outwards and inwards. The geodesic acoustic mode (GAM) is found to coexist with the LFZF, and the LFZF is found to modulate the GAM and ambient turbulence with in-phase and antiphase relations, respectively, through an envelope analysis.
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Affiliation(s)
- A D Liu
- CAS Key Laboratory of Basic Plasma Physics, and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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33
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Ohshima S, Ido T, Shimizu A, Nishiura M, Nakano H. Measurements of spatial structure of plasma potential and density fluctuations by multichannel heavy ion beam probe on large helical device. Rev Sci Instrum 2008; 79:10F320. [PMID: 19044633 DOI: 10.1063/1.2981177] [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] [Indexed: 05/27/2023]
Abstract
Heavy ion beam probe (HIBP) on large helical device is currently equipped with three channel detectors, which can observe three spatial points simultaneously inside the plasma with resolution of approximately 10 mm. The beam trajectories and observation point location are calculated numerically and optimized allowing for the identification of the mode structure in multichannel (up to 9) HIBP measurements. The calculations show that the radial and poloidal wavenumbers can be identified by proper changing and choosing of the beam energy and trajectory.
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Affiliation(s)
- Shinsuke Ohshima
- National Institute for Fusion Science, 322-6, Oroshi-cho, Toki, Gifu 509-5292, Japan.
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34
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Schmitz L, Wang G, Hillesheim JC, Rhodes TL, Peebles WA, White AE, Zeng L, Carter TA, Solomon W. Detection of zonal flow spectra in DIII-D by a dual-channel Doppler backscattering system. Rev Sci Instrum 2008; 79:10F113. [PMID: 19044597 DOI: 10.1063/1.2953675] [Citation(s) in RCA: 11] [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] [Indexed: 05/27/2023]
Abstract
Doppler backscattering (DBS) has been successfully used to measure the E x B flow velocity and local intermediate wavenumber density fluctuation levels in the DIII-D tokamak. Depending on the launch angle and the frequency of the probing beam, the signal backscattered from the plasma cut-off layer is sensitive to density fluctuations at a specific perpendicular wavenumber (1 < or = k(perpendicular rho(s)) < or = 4). Due to the localization and high time resolution for poloidal flow measurements, DBS is well suited to detect stationary and time-dependent shear flows [zonal flows (ZFs)]. We present a novel scheme to measure ZF spectra using a dual-channel DBS system capable of simultaneously probing two minor radii separated by a distance of 0.2 cm < Delta r < 3 cm. Frequency spectra of geodesic acoustic modes and low frequency ZFs (f or = 10 kHz) have been obtained for 0.6 < r/a < 0.95.
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Affiliation(s)
- L Schmitz
- UCLA Physics and Astronomy Department, Los Angeles, California 90095-1547, USA
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35
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Xu XQ, Xiong Z, Gao Z, Nevins WM, McKee GR. TEMPEST simulations of collisionless damping of the geodesic-acoustic mode in edge-plasma pedestals. Phys Rev Lett 2008; 100:215001. [PMID: 18518611 DOI: 10.1103/physrevlett.100.215001] [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: 05/30/2007] [Revised: 09/28/2007] [Indexed: 05/26/2023]
Abstract
The fully nonlinear (full-f) four-dimensional TEMPEST gyrokinetic continuum code correctly produces the frequency and collisionless damping of geodesic-acoustic modes (GAMs) and zonal flow, with fully nonlinear Boltzmann electrons for the inverse aspect ratio scan and the tokamak safety factor q scan in homogeneous plasmas. TEMPEST simulations show that the GAMs exist in the edge pedestal for steep density and temperature gradients in the form of outgoing waves. The enhanced GAM damping may explain experimental beam emission spectroscopy measurements on the edge q scaling of the GAM amplitude.
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Affiliation(s)
- X Q Xu
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
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36
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Watanabe TH, Sugama H, Ferrando-Margalet S. Reduction of turbulent transport with zonal flows enhanced in helical systems. Phys Rev Lett 2008; 100:195002. [PMID: 18518454 DOI: 10.1103/physrevlett.100.195002] [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: 02/12/2008] [Indexed: 05/26/2023]
Abstract
Gyrokinetic Vlasov simulations of the ion temperature gradient turbulence are performed in order to investigate effects of helical magnetic configurations on turbulent transport and zonal flows. The obtained results confirm the theoretical prediction that helical configurations optimized for reducing neoclassical ripple transport can simultaneously reduce the turbulent transport with enhancing zonal-flow generation. Stationary zonal-flow structures accompanied with transport reduction are clearly identified by the simulation for the neoclassically optimized helical geometry. The generation of the stationary zonal flow explains a physical mechanism for causing the confinement improvement observed in the inward-shifted plasma in the Large Helical Device [O. Motojima, Nucl. Fusion 43, 1674 (2003)].
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Affiliation(s)
- T-H Watanabe
- National Institute for Fusion Science Toki, Gifu, Japan
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37
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Hamada Y, Watari T, Yamagishi O, Nishizawa A, Narihara K, Kawasumi Y, Ido T, Kojima M, Toi K. Change of zonal flow spectra in the JIPP T-IIU tokamak plasmas. Phys Rev Lett 2007; 99:065005. [PMID: 17930839 DOI: 10.1103/physrevlett.99.065005] [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: 10/05/2006] [Revised: 04/09/2007] [Indexed: 05/25/2023]
Abstract
When Ohmically heated low-density plasmas are additionally heated by higher-harmonics ion-cyclotron-range-of frequency heating, heated by neutral beam injection, or strongly gas puffed, the intensity of zonal flows in the geodesic acoustic mode frequency range in the tokamak core plasma decreases sharply and that of low-frequency zonal flow grows drastically. This is accompanied by a damping of the drift wave propagating in the electron diamagnetic drift direction, turbulence by trapped electron mode (TEM), and the increase of the mode propagating to ion diamagnetic drift direction (ITG). In the half-radius region, TEM and high-frequency zonal flows remain intense in both OH and heated phases. ITG and low-frequency zonal flows grow in heated plasmas, suggesting a strong coupling between ITG and low-frequency zonal flow.
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Affiliation(s)
- Y Hamada
- National Institute for Fusion Science, Toki, 509-5292, Japan
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38
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Fujisawa A, Itoh K, Shimizu A, Nakano H, Ohshima S, Iguchi H, Matsuoka K, Okamura S, Minami T, Yoshimura Y, Nagaoka K, Ida K, Toi K, Takahashi C, Kojima M, Nishimura S, Isobe M, Suzuki C, Akiyama T, Nagashima Y, Itoh SI, Diamond PH. Experimental evidence of a zonal magnetic field in a toroidal plasma. Phys Rev Lett 2007; 98:165001. [PMID: 17501426 DOI: 10.1103/physrevlett.98.165001] [Citation(s) in RCA: 7] [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: 11/01/2006] [Indexed: 05/15/2023]
Abstract
A zonal magnetic field is found in a toroidal plasma. The magnetic field has a symmetric bandlike structure, which is uniform in the toroidal and poloidal directions and varies radially with a finite wavelength of mesoscale, which is analogous to zonal flows. A time-dependent bicoherence analysis reveals that the magnetic field should be generated by the background plasma turbulence. The discovery is classified as a new kind of phenomenon of structured magnetic field generation, giving insight into phenomena such as dipole field generation in rotational planets.
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Affiliation(s)
- A Fujisawa
- National Institute for Fusion Science, Oroshi-cho, Toki-shi 509-52, Japan
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39
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Affiliation(s)
- Chang-Mo Ryu
- Department of physics, POSTECH, Pohang 790-784, Korea
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40
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Okamura S, Akiyama T, Fujisawa A, Ida K, Iguchi H, Isobe M, Kado S, Minami T, Nagaoka K, Nakamura K, Nishimura S, Matsuoka K, Matsushita H, Nakano H, Ohshima S, Oishi T, Shimizu A, Suzuki C, Takahashi C, Toi K, Yoshimura Y, Yoshinu M. Improved Confinement and Related Physics Study in the Compact Helical System. Fusion Science and Technology 2007. [DOI: 10.13182/fst07-a1286] [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)
- S. Okamura
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - T. Akiyama
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - A. Fujisawa
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - K. Ida
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - H. Iguchi
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - M. Isobe
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - S. Kado
- The University of Tokyo, High-Temperature Plasma Center, 5-1-5 Kashiwanoha, Kashiwa, Chiba 227-8568, Japan
| | - T. Minami
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - K. Nagaoka
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - K. Nakamura
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - S. Nishimura
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - K. Matsuoka
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - H. Matsushita
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - H. Nakano
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - S. Ohshima
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - T. Oishi
- The University of Tokyo, Graduate School of Engineering, Department of Quantum Engineering and System Science Hongo 7-3-1, Tokyo 113-8656, Japan
| | - A. Shimizu
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - C. Suzuki
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - C. Takahashi
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - K. Toi
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - Y. Yoshimura
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
| | - M. Yoshinu
- National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292, Japan
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41
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Xia H, Shats MG, Punzmann H. Strong ExB shear flows in the transport-barrier region in H-mode plasma. Phys Rev Lett 2006; 97:255003. [PMID: 17280363 DOI: 10.1103/physrevlett.97.255003] [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: 07/31/2006] [Indexed: 05/13/2023]
Abstract
We report the first experimental observation of stationary zonal flow in the transport-barrier region of the H-mode plasma. Strong peaks in Er shear mark the width of this region. A strong m = n = 0 low-frequency (f < 0.6 kHz) zonal flow is observed in regions of increased Er, suggesting a substantial contribution of zonal flow to the spatial modulation of Er radial profiles. Radial localization of the zonal flow is correlated with a region of zero magnetic shear and low-order (7/5) rational surfaces.
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Affiliation(s)
- H Xia
- Plasma Research Laboratory, Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200, Australia.
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42
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Gupta DK, Fonck RJ, McKee GR, Schlossberg DJ, Shafer MW. Detection of zero-mean-frequency zonal flows in the core of a high-temperature tokamak plasma. Phys Rev Lett 2006; 97:125002. [PMID: 17025976 DOI: 10.1103/physrevlett.97.125002] [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: 03/24/2006] [Indexed: 05/12/2023]
Abstract
A low-frequency, spectrally broad (Deltaf approximately 10 kHz) poloidal flow structure that peaks near zero frequency is observed in time-resolved measurements of the turbulence velocity field in the core region (r/a approximately 0.6-0.9) of DIII-D tokamak plasmas. These flows exhibit a long poloidal wavelength (low m) and a short radial coherence length comparable to the ambient turbulence decorrelation length. Characteristics of these observed poloidal flows are consistent with the theoretically predicted residual or zero-mean-frequency zonal flows.
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Affiliation(s)
- D K Gupta
- University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA
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43
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Krämer-Flecken A, Soldatov S, Koslowski HR, Zimmermann O. Properties of geodesic acoustic modes and the relation to density fluctuations. Phys Rev Lett 2006; 97:045006. [PMID: 16907585 DOI: 10.1103/physrevlett.97.045006] [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: 01/27/2006] [Indexed: 05/11/2023]
Abstract
The geodesic acoustic mode (GAM) is a high frequency branch of zonal flows, which is observed in toroidal plasmas. Because of toroidal curvature effects, density fluctuations are excited, which are investigated with the O-mode correlation reflectometer at TEXTOR. This Letter reports on the poloidal distribution of GAM induced density fluctuation and compares them with theoretical predictions. The influence of the GAM flows on the ambient turbulence is studied, too.
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Affiliation(s)
- A Krämer-Flecken
- Institut für Plasmaphysik, Forschungszentrum Jülich GmbH, EURATOM Association, D-52425 Jülich, Germany
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44
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Zhao KJ, Lan T, Dong JQ, Yan LW, Hong WY, Yu CX, Liu AD, Qian J, Cheng J, Yu DL, Yang QW, Ding XT, Liu Y, Pan CH. Toroidal symmetry of the geodesic acoustic mode zonal flow in a tokamak plasma. Phys Rev Lett 2006; 96:255004. [PMID: 16907314 DOI: 10.1103/physrevlett.96.255004] [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: 02/24/2006] [Revised: 04/28/2006] [Indexed: 05/11/2023]
Abstract
The toroidal symmetry of the geodesic acoustic mode (GAM) zonal flows is identified with toroidally distributed three step Langmuir probes at the edge of the HuanLiuqi-2A (commonly referred to as HL-2A) tokamak plasmas for the first time. High coherence of both the GAM and the ambient turbulence for the toroidally displaced measurements along a magnetic field line is observed, in contrast with the high coherence of the GAM but low coherence of the ambient turbulence when the toroidally displaced measurements are not along the same field line. The radial and poloidal features of the flows are also simultaneously determined. The nonlinear three wave coupling between the high frequency turbulent fluctuations and the flows is demonstrated to be a plausible formation mechanism of the flows.
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Affiliation(s)
- K J Zhao
- Southwestern Institute of Physics, P.O. Box 432, Chengdu, China
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45
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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. Phys Rev Lett 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] [What about the content of this article? (0)] [Affiliation(s)] [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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46
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Hamada Y, Watari T, Nishizawa A, Narihara K, Kawasumi Y, Ido T, Kojima M, Toi K. Streamers in the JIPP T-llU tokamak plasmas. Phys Rev Lett 2006; 96:115003. [PMID: 16605833 DOI: 10.1103/physrevlett.96.115003] [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: 06/15/2005] [Indexed: 05/08/2023]
Abstract
It is shown that the low-density Ohmically heated tokamak plasmas have streamerlike eddies at the outer region at normalized minor radius of about 0.7 and high-frequency zonal flows of large amplitudes in the core. The amplitudes of the eddies ePhi/kT(e) and n(e)/n(e) are of order of 0.5, similar to that of blobs in the tokamak plasma boundary. The waveforms are featured by pulses of complex shape with sharp fronts, similar to the results of streamer simulations by Garbet et al.. The time constant of the fronts is also in agreement with the simulation. The radial span of the eddies is estimated to be much larger than the poloidal span.
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Affiliation(s)
- Y Hamada
- National Institute for Fusion Science, Toki 509-5292, Japan
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47
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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. Phys Rev Lett 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] [What about the content of this article? (0)] [Affiliation(s)] [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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48
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Shats MG, Xia H, Punzmann H. Spectral condensation of turbulence in plasmas and fluids and its role in low-to-high phase transitions in toroidal plasma. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 71:046409. [PMID: 15903796 DOI: 10.1103/physreve.71.046409] [Citation(s) in RCA: 4] [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: 08/18/2004] [Indexed: 05/02/2023]
Abstract
Transitions from turbulence to order are studied experimentally in thin fluid layers and in magnetically confined toroidal plasma. It is shown that turbulence self-organizes through the mechanism of spectral condensation in both systems. The spectral redistribution of the turbulent energy leads to the reduction in the turbulence level, generation of coherent flow, reduction in the particle diffusion, and increase in the system's energy. The higher-order state in the plasma is sustained via the non-local spectral coupling of the linearly unstable spectral range to the large-scale mean flow. Spectral condensation of turbulence is discussed in terms of its role in the low-to-high confinement transitions in toroidal plasma which show similarity with phase transitions.
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Affiliation(s)
- M G Shats
- Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia
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49
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Abstract
A theory for describing collisionless long-time behavior of zonal flows in helical systems is presented and its validity is verified by gyrokinetic-Vlasov simulation. It is shown that, under the influence of particles trapped in helical ripples, the response of zonal flows to a given source becomes weaker for lower radial wave numbers and deeper helical ripples while a high-level zonal-flow response, which is not affected by helical-ripple-trapped particles, can be maintained for a longer time by reducing their bounce-averaged radial drift velocity. This implies a possibility that helical configurations optimized for reducing neoclassical ripple transport can simultaneously enhance zonal flows which lower anomalous transport.
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Affiliation(s)
- H Sugama
- National Institute for Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Japan
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