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Kobayashi T, Fujisawa A, Nagashima Y, Moon C, Yamasaki K, Nishimura D, Inagaki S, Shimizu A, Tokuzawa T, Ido T. Identification of nonlinear effects of background asymmetry on solitary oscillations in a cylindrical plasma. Sci Rep 2024; 14:12175. [PMID: 38806603 PMCID: PMC11133312 DOI: 10.1038/s41598-024-62969-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Accepted: 05/23/2024] [Indexed: 05/30/2024] Open
Abstract
A symmetry-breaking in rotational spatial pattern of quasi-periodic solitary oscillations is revealed with tomography measurement of plasma emission, simultaneously with background asymmetry in stationary plasma structure. Although the oscillatory pattern deformation is a natural course in the presence of asymmetry, elaborate analyses identify existence unfeatured nonlinear effects of the background asymmetry, i.e., its nonlinear couplings with harmonic modes of rotational symmetry, to produce non-harmonic mode to break the symmetry and cause the oscillatory pattern to be chaotic. The findings suggest the unrecognized fundamental process for plasmas to be turbulent.
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Affiliation(s)
- Taiki Kobayashi
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, 816-8580, Japan.
| | - Akihide Fujisawa
- Research Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga, 816-8580, Japan
- National Institute for Fusion Science, National Institute of Natural Sciences, Toki, 509-5292, Japan
| | - Yoshihiko Nagashima
- Research Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga, 816-8580, Japan
| | - Chanho Moon
- Research Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga, 816-8580, Japan
| | - Kotaro Yamasaki
- Graduate School of Advanced Science and Engineering, Hiroshima University, Higashihiroshima, 739-8527, Japan
| | - Daiki Nishimura
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, 816-8580, Japan
| | - Sigeru Inagaki
- Institute of Advanced Energy, Kyoto University, Uji, 611-0011, Japan
| | - Akihiro Shimizu
- Research Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, Japan
- National Institute for Fusion Science, National Institute of Natural Sciences, Toki, 509-5292, Japan
| | - Tokihiko Tokuzawa
- Research Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, Japan
- National Institute for Fusion Science, National Institute of Natural Sciences, Toki, 509-5292, Japan
| | - Takeshi Ido
- Research Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, Japan
- Research Center for Plasma Turbulence, Kyushu University, Kasuga, 816-8580, Japan
- National Institute for Fusion Science, National Institute of Natural Sciences, Toki, 509-5292, Japan
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2
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Yashin A, Teplova N, Zadvitskiy G, Ponomarenko A. Modelling of Backscattering off Filaments Using the Code IPF-FD3D for the Interpretation of Doppler Backscattering Data. SENSORS (BASEL, SWITZERLAND) 2022; 22:9441. [PMID: 36502138 PMCID: PMC9735465 DOI: 10.3390/s22239441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 11/26/2022] [Accepted: 11/30/2022] [Indexed: 06/17/2023]
Abstract
Filaments or blobs are well known to strongly contribute to particle and energy losses both in L- and H-mode, making them an important plasma characteristic to investigate. They are plasma structures narrowly localized across a magnetic field and stretched along magnetic field lines. In toroidal devices, their development is observed to take place in the peripheral plasma. Filament characteristics have been studied extensively over the years using various diagnostic techniques. One such diagnostic is the Doppler backscattering (DBS) method employed at the spherical tokamak Globus-M/M2. It has been observed that the DBS signal reacts to the backscattering from filaments. However, the DBS data have proven difficult to analyze, which is why modelling was undertaken using the code IPF-FD3D to understand what kind of information can be extrapolated from the signals. A circular filament was thoroughly investigated in slab geometry with a variety of characteristics studied. Apart from that, the motion of the filaments in the poloidal and radial directions was analyzed. Additionally, other shapes of filaments were presented in this work. Modelling for the real geometry of the Globus-M/M2 tokamak was performed.
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Affiliation(s)
- Alexander Yashin
- Plasma Physics Department, Peter the Great Saint Petersburg Polytechnic University, 195251 Saint Petersburg, Russia
- Plasma Research Laboratory, Ioffe Institute, 195251 Saint Petersburg, Russia
| | - Natalia Teplova
- Plasma Physics Department, Peter the Great Saint Petersburg Polytechnic University, 195251 Saint Petersburg, Russia
- Plasma Research Laboratory, Ioffe Institute, 195251 Saint Petersburg, Russia
| | | | - Anna Ponomarenko
- Plasma Physics Department, Peter the Great Saint Petersburg Polytechnic University, 195251 Saint Petersburg, Russia
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3
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Zhu Y, Chen Y, Yu JH, Domier C, Yu G, Liu X, Kramer G, Ren Y, Diallo A, Luhmann NC, Li X. System-on-chip approach microwave imaging reflectometer on DIII-D tokamak. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:113509. [PMID: 36461457 DOI: 10.1063/5.0099170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 09/08/2022] [Indexed: 06/17/2023]
Abstract
System-on-chip millimeter wave integrated circuit technology is used on the two-dimensional millimeter-wave imaging reflectometer (MIR) upgrade for density fluctuation imaging on the DIII-D tokamak fusion plasma. Customized CMOS chips have been successfully developed for the transmitter module and receiver module array, covering the 55-75 GHz working band. The transmitter module has the capability of simultaneously launching eight tunable probe frequencies (>0 dBm output power each). The receiver enclosure contains 12 receiver modules in two vertical lines. The quasi-optical local oscillator coupling of previous MIR systems has been replaced with an internal active frequency multiplier chain for improved local oscillator power delivery and flexible installation in a narrow space together with improved shielding against electromagnetic interference. The 55-75 GHz low noise amplifier, used between the receiver antenna and the first-stage mixer, significantly improves module sensitivity and suppresses electronics noise. The receiver module has a 20 dB gain improvement compared with the mini-lens approach and better than -75 dBm sensitivity, and its electronics noise temperature has been reduced from 55 000 K down to 11 200 K. The V-band MIR system is developed for co-located multi-field investigation of MHD-scale fluctuations in the pedestal region with W-band electron cyclotron emission imaging on DIII-D tokamak.
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Affiliation(s)
- Y Zhu
- Department of Electrical and Computer Engineering, University of California Davis, Davis, California 95616, USA
| | - Y Chen
- Department of Electrical and Computer Engineering, University of California Davis, Davis, California 95616, USA
| | - J-H Yu
- Department of Electrical and Computer Engineering, University of California Davis, Davis, California 95616, USA
| | - C Domier
- Department of Electrical and Computer Engineering, University of California Davis, Davis, California 95616, USA
| | - G Yu
- Department of Electrical and Computer Engineering, University of California Davis, Davis, California 95616, USA
| | - X Liu
- Department of Electrical and Computer Engineering, University of California Davis, Davis, California 95616, USA
| | - G Kramer
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - Y Ren
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - A Diallo
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - N C Luhmann
- Department of Electrical and Computer Engineering, University of California Davis, Davis, California 95616, USA
| | - X Li
- Department of Electrical and Computer Engineering, University of California Davis, Davis, California 95616, USA
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4
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Hong YH, Kim KY, Kim JH, Son SH, Lee HH, Eo HD, Kim MS, Hong SH, Chung CW. Two-dimensional measurements of the ELM filament using a multi-channel electrical probe array with high time resolution at the far SOL region in the KSTAR. NUCLEAR ENGINEERING AND TECHNOLOGY 2022. [DOI: 10.1016/j.net.2022.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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5
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W-Band Modular Antenna/Detector Array for the Electron Cyclotron Emission Imaging System in KSTAR. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12052431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A design of a modular antenna/detector array for the electron cyclotron emission (ECE) imaging system at the Korea Superconducting Tokamak Advanced Research (KSTAR) is proposed. The modular antenna/detector array is based on a unit antenna/detector module, which consists of an elliptical mini-lens, a dual-dipole antenna, an antenna balun, a low-noise amplifier, and a metal frame. The proposed modular antenna/detector array resolves the problem in the conventional antenna/detector array where one faulty channel requires the entire array to be removed for the service. With the proposed modular array, each channel module can be easily and independently removed and replaced without interference to the rest of the array, thus minimizing the interrupted service time for maintenance. Moreover, the unit channel modules can be efficiently updated under a variety of the tokamak operation conditions. The antenna/detector modules are optimized to have improved performance, and are tested in a W-band test setup, and consistently provide the gain increase by 10~20 dB as compared with the conventional antenna/detector array. A set of the proposed modular antenna/detector array is currently installed and tested in the KSTAR ECE imaging system, and will consistently produce the improved ECE imaging to monitor MHD instability activities under various plasma operation conditions.
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6
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Lee JE, Seo PH, Bak JG, Yun GS. A machine learning approach to identify the universality of solitary perturbations accompanying boundary bursts in magnetized toroidal plasmas. Sci Rep 2021; 11:3662. [PMID: 33574460 PMCID: PMC7878480 DOI: 10.1038/s41598-021-83192-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 01/28/2021] [Indexed: 11/09/2022] Open
Abstract
Experimental observations assisted by 2-D imaging diagnostics on the KSTAR tokamak show that a solitary perturbation (SP) emerges prior to a boundary burst of magnetized toroidal plasmas, which puts forward SP as a potential candidate for the burst trigger. We have constructed a machine learning (ML) model based on a convolutional deep neural network architecture for a statistical study to identify the SP as a boundary burst trigger. The ML model takes sequential signals detected from 19 toroidal Mirnov coils as input and predicts whether each temporal frame corresponds to an SP. We trained the network in a supervised manner on a training set consisting of real signals with manually annotated SP locations and synthetic burst signals. The trained model achieves high performances in various metrics on a test data set. We also demonstrated the reliability of the model by visualizing the discriminative parts of the input signals that the model recognizes. Finally, we applied the trained model to new data from KSTAR experiments, which were never seen during training, and confirmed that the large burst at the plasma boundary that can fatally damage the fusion device always involves the emergence of SP. This result suggests that the SP is a key to understanding and controlling of the boundary burst in magnetized toroidal plasmas.
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Affiliation(s)
- J E Lee
- Pohang University of Science and Technology, Pohang, 37673, Korea
| | - P H Seo
- Pohang University of Science and Technology, Pohang, 37673, Korea
| | - J G Bak
- National Fusion Research Institute, Daejeon, 34133, Korea
| | - G S Yun
- Pohang University of Science and Technology, Pohang, 37673, Korea.
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7
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Sabot R, Giacalone JC, Nam Y, Berne A, Brun C, Elbèze D, Faisse F, Gargiulo L, Kim M, Lee W, Lotte P, Park HK, Santraine B, Yun G. Development of Microwave Imaging Diagnostics for WEST Tokamak. JOURNAL OF FUSION ENERGY 2019. [DOI: 10.1007/s10894-019-00216-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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8
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Sabot R, Nam Y, Brun C, Elbèze D, Faisse F, Gargiulo L, Kim M, Lee W, Lotte P, Park HK, Yun G. Integration of an Electron Cyclotron Imaging diagnostic system on the WEST tokamak. EPJ WEB OF CONFERENCES 2019. [DOI: 10.1051/epjconf/201920303011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
An Electron Cyclotron Emission Imaging (ECEI) diagnostic system for the WEST tokamak has been developed under the UNIST-WEST collaboration. This diagnostic system is designed to overcome accessibility and thermomechanical constraints for long pulse operation. The first O-mode channel will be installed in the first trimester of 2019 to probe the low field side (LFS) of the WEST plasma. Two large metallic reflective mirrors are installed inside the duct which is being used for maintenance access. They are suspended on a rail to facilitate mirror manipulation. The ex-vessel optical system (lens, detection array, etc.) is housed in a compact optical enclosure that fits in a tight free space between the port flange and tokamak access lobby. The design emphasized reproducibility of the precise alignment between in-vessel mirrors and optical enclosure since the both elements must be removed during shutdown period for maintenance access. The overall optical system was fully tested at UNIST last year. The test results demonstrated that the imaging optics can full access at any radial position on the LFS. The 2D beam pattern measurements were consistent with the design values.
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Zhu Y, Ye Y, Yu JH, Tobias B, Pham AV, Wang Y, Luo C, Domier CW, Kramer G, Ren Y, Diallo A, Nazikian R, Chen M, Yu G, Luhmann NC. Liquid crystal polymer receiver modules for electron cyclotron emission imaging on the DIII-D tokamak. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:10H120. [PMID: 30399858 DOI: 10.1063/1.5035373] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Accepted: 05/30/2018] [Indexed: 06/08/2023]
Abstract
A new generation of millimeter-wave heterodyne imaging receiver arrays has been developed and demonstrated on the DIII-D electron cyclotron emission imaging (ECEI) system. Improved circuit integration, improved noise performance, and enhanced shielding from out-of-band emission are made possible by using advanced liquid crystal polymer (LCP) substrates and monolithic microwave integrated circuit (MMIC) receiver chips. This array exhibits ∼15 dB additional gain and >30× reduction in noise temperature compared to previous generation ECEI arrays. Each LCP horn-waveguide module houses a 3 × 3 mm GaAs MMIC receiver chip, which consists of a low noise millimeter-wave preamplifier, balanced mixer, and IF amplifier together with a local oscillator multiplier chain driven at ∼12 GHz. A proof-of-principle partial LCP instrument with 5 poloidal channels was installed on DIII-D in 2017, with a full proof-of-principle system (20 poloidal × 8 radial channels) installed and commissioned in early 2018. The enhanced shielding of the LCP modules is seen to greatly reduce the sensitivity of ECEI signals to out-of-band microwave noise which has plagued previous ECEI studies on DIII-D. The LCP ECEI system is expected to be a valuable diagnostic tool for pedestal region measurements, focusing particularly on electron temperature evolution during edge localized mode bursting.
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Affiliation(s)
- Y Zhu
- University of California Davis, Davis, California 95616, USA
| | - Y Ye
- University of California Davis, Davis, California 95616, USA
| | - J-H Yu
- University of California Davis, Davis, California 95616, USA
| | - B Tobias
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - A-V Pham
- University of California Davis, Davis, California 95616, USA
| | - Y Wang
- University of California Davis, Davis, California 95616, USA
| | - C Luo
- University of California Davis, Davis, California 95616, USA
| | - C W Domier
- University of California Davis, Davis, California 95616, USA
| | - G Kramer
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - Y Ren
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - A Diallo
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - R Nazikian
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - M Chen
- University of California Davis, Davis, California 95616, USA
| | - G Yu
- University of California Davis, Davis, California 95616, USA
| | - N C Luhmann
- University of California Davis, Davis, California 95616, USA
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10
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Trigger mechanism for the abrupt loss of energetic ions in magnetically confined plasmas. Sci Rep 2018; 8:2804. [PMID: 29434239 PMCID: PMC5809513 DOI: 10.1038/s41598-018-21128-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 01/30/2018] [Indexed: 12/04/2022] Open
Abstract
Interaction between a quasi-stable stationary MHD mode and a tongue-shaped deformation is observed in the toroidal plasma with energetic particle driven MHD bursts. The quasi-stable stationary 1/1 MHD mode with interchange parity appears near the resonant rational surface of q = 1 between MHD bursts. The tongue-shaped deformation rapidly appears at the non-resonant non-rational surface as a localized large plasma displacement and then collapses (tongue event). It curbs the stationary 1/1 MHD mode and then triggers the collapse of energetic particle and magnetic field reconnection. The rotating 1/1 MHD mode with tearing parity at the q = 1 resonant surface, namely, the MHD burst, is excited after the tongue event.
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11
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Bae MK, Pitts R, Bak J, Hong SH, Kim H, Lee H, Kang I, Chung KS. Type I ELM filament heat fluxes on the KSTAR main chamber wall. NUCLEAR MATERIALS AND ENERGY 2017. [DOI: 10.1016/j.nme.2017.04.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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12
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Nagayama Y, Ito N, Kuwahara D, Tsuchiya H, Yamaguchi S. Development of 2-D horn-antenna millimeter-wave imaging device (HMID) for the plasma diagnostics. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2017; 88:044703. [PMID: 28456234 DOI: 10.1063/1.4980150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The two-dimensional (2-D) Horn-antenna Millimeter-wave Imaging Device (HMID) has been developed for the O-mode Microwave Imaging Reflectometry (O-MIR) in the Large Helical Device (LHD). The detectable frequency range of the HMID is 23-33 GHz, which corresponds to the cutoff electron density of 0.8-1.5 × 1019 m-3 in the O-MIR. The HMID is a 2-D imaging device that improves on the horn-antenna mixer array, which had been developed for the X-mode MIR in the LHD. In the HMID, the signal (RF) wave from the horn antenna is transmitted to the microstrip line by the finline transmitter, and this is mixed by the double-balanced-mixer with the local oscillation wave that is fed by a coaxial cable. By using the HMID, the MIR optical system can be significantly simplified.
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Affiliation(s)
- Y Nagayama
- National Institute for Fusion Science, National Institute for Natural Sciences, Toki 509-5292, Japan
| | - N Ito
- National Institute of Technology, Ube College, Ube 755-8555, Japan
| | - D Kuwahara
- Tokyo University of Agriculture and Technology, Koganei 184-8588, Japan
| | - H Tsuchiya
- National Institute for Fusion Science, National Institute for Natural Sciences, Toki 509-5292, Japan
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13
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Nam YB, Park HK, Lee W, Yun GS, Kim M, Sabot R, Elbeze D, Lotte P, Shen J. Compact ECEI system with in-vessel reflective optics for WEST. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:11E135. [PMID: 27910691 DOI: 10.1063/1.4962941] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
An electron cyclotron emission imaging (ECEI) diagnostic system for WEST (W Environment for Steady state Tokamak) is under development to study the MHD instabilities affected by tungsten impurities. The system will provide 2-D Te fluctuation images (width × height = ∼18 cm × ∼ 34 cm at low field side and ∼13 cm × ∼ 39 cm at high field side) from a poloidal cross section with high spatial (≤1.7 cm) and temporal (≤2 μs) resolutions. While the key concept and electronic structure are similar to that of prior ECEI systems on other tokamak devices such as KSTAR, DIII-D, or ASDEX-U, part of the imaging optics have to be placed inside the vacuum vessel in order to resolve issues on limited installation space and longer beam path to the detector position. The in-vessel optics consisting of two large curvature-radius mirrors are expected to withstand the extreme heating on long-pulse operation scenario (∼1000 s). The out-vessel optical housing is constructed as compact as possible to remove easily from the installation site in case of necessity. Commissioning of the system is scheduled on the second experimental WEST campaign end of 2017.
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Affiliation(s)
- Y B Nam
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, South Korea
| | - H K Park
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - W Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - G S Yun
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, South Korea
| | - M Kim
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - R Sabot
- CEA, IRFM, F-13108 Saint Paul lez Durance, France
| | - D Elbeze
- CEA, IRFM, F-13108 Saint Paul lez Durance, France
| | - P Lotte
- CEA, IRFM, F-13108 Saint Paul lez Durance, France
| | - J Shen
- CEA, IRFM, F-13108 Saint Paul lez Durance, France
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14
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Abrupt onset of tongue deformation and phase space response of ions in magnetically-confined plasmas. Sci Rep 2016; 6:36217. [PMID: 27796370 PMCID: PMC5087079 DOI: 10.1038/srep36217] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 10/12/2016] [Indexed: 11/10/2022] Open
Abstract
An abrupt onset of the new tongue-shaped deformation of magnetic surface in magnetized plasmas, which was conjectured in since the 1960s but has not been observed, is experimentally identified just before an abrupt onset of a large-scale collapse event. Two novel properties of the event are identified. First, the transition of symmetry of perturbation (rather than a growth of linearly unstable MHD modes) was found to be a key for the onset of abrupt collapse, i.e., the transition of symmetry gives a new route to the collapse from stable state. Second, as a phase-space response of ions, the distortion from Maxwell-Boltzmann distribution of epithermal ions was observed for the first time.
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15
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Choi MJ, Park HK, Yun GS, Nam YB, Choe GH, Lee W, Jardin S. Post calibration of the two-dimensional electron cyclotron emission imaging instrument with electron temperature characteristics of the magnetohydrodynamic instabilities. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:013506. [PMID: 26827320 DOI: 10.1063/1.4940030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 01/05/2016] [Indexed: 06/05/2023]
Abstract
The electron cyclotron emission imaging (ECEI) instrument is widely used to study the local electron temperature (Te) fluctuations by measuring the ECE intensity IECE ∝ Te in tokamak plasmas. The ECEI measurement is often processed in a normalized fluctuation quantity against the time averaged value due to complication in absolute calibration. In this paper, the ECEI channels are relatively calibrated using the flat Te assumption of the sawtooth crash or the tearing mode island and a proper extrapolation. The 2-D relatively calibrated electron temperature (Te,rel) images are reconstructed and the displacement amplitude of the magnetohydrodynamic modes can be measured for the accurate quantitative growth analysis.
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Affiliation(s)
- M J Choi
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - H K Park
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - G S Yun
- Pohang University of Science and Technology, Pohang, Gyeongbuk 790-784, South Korea
| | - Y B Nam
- Pohang University of Science and Technology, Pohang, Gyeongbuk 790-784, South Korea
| | - G H Choe
- Pohang University of Science and Technology, Pohang, Gyeongbuk 790-784, South Korea
| | - W Lee
- Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea
| | - S Jardin
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
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16
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Yun GS, Lee W, Choi MJ, Lee J, Kim M, Leem J, Nam Y, Choe GH, Park HK, Park H, Woo DS, Kim KW, Domier CW, Luhmann NC, Ito N, Mase A, Lee SG. Quasi 3D ECE imaging system for study of MHD instabilities in KSTAR. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:11D820. [PMID: 25430233 DOI: 10.1063/1.4890401] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A second electron cyclotron emission imaging (ECEI) system has been installed on the KSTAR tokamak, toroidally separated by 1/16th of the torus from the first ECEI system. For the first time, the dynamical evolutions of MHD instabilities from the plasma core to the edge have been visualized in quasi-3D for a wide range of the KSTAR operation (B0 = 1.7∼3.5 T). This flexible diagnostic capability has been realized by substantial improvements in large-aperture quasi-optical microwave components including the development of broad-band polarization rotators for imaging of the fundamental ordinary ECE as well as the usual 2nd harmonic extraordinary ECE.
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Affiliation(s)
- G S Yun
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - W Lee
- Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea
| | - M J Choi
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - J Lee
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - M Kim
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - J Leem
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Y Nam
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - G H Choe
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - H K Park
- Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea
| | - H Park
- School of Electrical Engineering, Kyungpook National University, Daegu 702-701, Korea
| | - D S Woo
- School of Electrical Engineering, Kyungpook National University, Daegu 702-701, Korea
| | - K W Kim
- School of Electrical Engineering, Kyungpook National University, Daegu 702-701, Korea
| | - C W Domier
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, USA
| | - N C Luhmann
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, USA
| | - N Ito
- KASTEC, Kyushu University, Kasuga-shi, Fukuoka 812-8581, Japan
| | - A Mase
- Ube National College of Technology, Ube-shi, Yamaguchi 755-8555, Japan
| | - S G Lee
- National Fusion Research Institute, Daejeon 305-333, Korea
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17
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Nam YU, Zoletnik S, Lampert M, Kovácsik Á, Wi HM. Edge electron density profiles and fluctuations measured by two-dimensional beam emission spectroscopy in the KSTAR. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:11E434. [PMID: 25430341 DOI: 10.1063/1.4894839] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Beam emission spectroscopy (BES) system in Korea Superconducting Tokamak Advanced Research (KSTAR) has recently been upgraded. The background intensity was reduced from 30% to 2% by suppressing the stray lights. This allows acquisition of the relative electron density profiles on the plasma edge without background subtraction from the beam power modulation signals. The KSTAR BES system has its spatial resolution of 1 cm, the temporal resolution of 2 MHz, and a total 32 channel (8 radial × 4 poloidal) avalanche photo diode array. Most measurements were done on the plasma edge, r/a ∼ 0.9, with 8 cm radial measurement width that covers the pedestal range. High speed density profile measurements reveal temporal behaviors of fast transient events, such as the precursors of edge localized modes and the transitions between confinement modes. Low background level also allows analysis of the edge density fluctuation patterns with reduced background fluctuations. Propagation of the density structures can be investigated by comparing the phase delays between the spatially distributed channels.
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Affiliation(s)
- Y U Nam
- National Fusion Research Institute, Daejeon, South Korea
| | - S Zoletnik
- Wigner RCP Institute for Particle and Nuclear Physics, Budapest, Hungary
| | - M Lampert
- Wigner RCP Institute for Particle and Nuclear Physics, Budapest, Hungary
| | - Ákos Kovácsik
- Institute of Nuclear Techniques, Budapest Technical University, Budapest, Hungary
| | - H M Wi
- National Fusion Research Institute, Daejeon, South Korea
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18
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Liu JX, Milbourne T, Bitter M, Delgado-Aparicio L, Dominguez A, Efthimion PC, Hill KW, Kramer GJ, Kung C, Kubota S, Kasparek W, Lu J, Pablant NA, Park H, Tobias B. Alternative optical concept for electron cyclotron emission imaging. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:11D802. [PMID: 25430215 DOI: 10.1063/1.4884902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The implementation of advanced electron cyclotron emission imaging (ECEI) systems on tokamak experiments has revolutionized the diagnosis of magnetohydrodynamic (MHD) activities and improved our understanding of instabilities, which lead to disruptions. It is therefore desirable to have an ECEI system on the ITER tokamak. However, the large size of optical components in presently used ECEI systems have, up to now, precluded the implementation of an ECEI system on ITER. This paper describes a new optical ECEI concept that employs a single spherical mirror as the only optical component and exploits the astigmatism of such a mirror to produce an image with one-dimensional spatial resolution on the detector. Since this alternative approach would only require a thin slit as the viewing port to the plasma, it would make the implementation of an ECEI system on ITER feasible. The results obtained from proof-of-principle experiments with a 125 GHz microwave system are presented.
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Affiliation(s)
- J X Liu
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
| | - T Milbourne
- Department of Physics, College of William and Mary, Williamsburg, Virginia 23185, USA
| | - M Bitter
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | | | - A Dominguez
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - P C Efthimion
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - K W Hill
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - G J Kramer
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - C Kung
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - S Kubota
- Department of Physics, University of California Los Angeles, Los Angeles, California 90095, USA
| | - W Kasparek
- Department of Electrical Engineering, University of Stuttgart, Stuttgart, Germany
| | - J Lu
- Department of Physics, Chongqing University, Chongqing 400044, China
| | - N A Pablant
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - H Park
- Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea
| | - B Tobias
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
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19
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Classen IGJ, Domier CW, Luhmann NC, Bogomolov AV, Suttrop W, Boom JE, Tobias BJ, Donné AJH. Dual array 3D electron cyclotron emission imaging at ASDEX Upgrade. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:11D833. [PMID: 25430246 DOI: 10.1063/1.4891061] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In a major upgrade, the (2D) electron cyclotron emission imaging diagnostic (ECEI) at ASDEX Upgrade has been equipped with a second detector array, observing a different toroidal position in the plasma, to enable quasi-3D measurements of the electron temperature. The new system will measure a total of 288 channels, in two 2D arrays, toroidally separated by 40 cm. The two detector arrays observe the plasma through the same vacuum window, both under a slight toroidal angle. The majority of the field lines are observed by both arrays simultaneously, thereby enabling a direct measurement of the 3D properties of plasma instabilities like edge localized mode filaments.
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Affiliation(s)
- I G J Classen
- FOM-Institute DIFFER, Dutch Institute for Fundamental Energy Research, 3430 BE Nieuwegein, The Netherlands
| | - C W Domier
- Department of Applied Science, University of California at Davis, Davis, California 95616, USA
| | - N C Luhmann
- Department of Applied Science, University of California at Davis, Davis, California 95616, USA
| | - A V Bogomolov
- FOM-Institute DIFFER, Dutch Institute for Fundamental Energy Research, 3430 BE Nieuwegein, The Netherlands
| | - W Suttrop
- Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, 85748 Garching, Germany
| | - J E Boom
- Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, 85748 Garching, Germany
| | - B J Tobias
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - A J H Donné
- FOM-Institute DIFFER, Dutch Institute for Fundamental Energy Research, 3430 BE Nieuwegein, The Netherlands
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20
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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. PHYSICAL REVIEW LETTERS 2014; 113:115001. [PMID: 25259985 DOI: 10.1103/physrevlett.113.115001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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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21
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Lee J, Yun GS, Lee JE, Kim M, Choi MJ, Lee W, Park HK, Domier CW, Luhmann NC, Sabbagh SA, Park YS, Lee SG, Bak JG. Toroidal mode number estimation of the edge-localized modes using the KSTAR 3-D electron cyclotron emission imaging system. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:063505. [PMID: 24985817 DOI: 10.1063/1.4883180] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A new and more accurate technique is presented for determining the toroidal mode number n of edge-localized modes (ELMs) using two independent electron cyclotron emission imaging (ECEI) systems in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The technique involves the measurement of the poloidal spacing between adjacent ELM filaments, and of the pitch angle α* of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that α* is nearly constant and thus well-defined at the midplane edge. Estimates of n obtained using two ECEI systems agree well with n measured by the conventional technique employing an array of Mirnov coils.
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Affiliation(s)
- J Lee
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - G S Yun
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - J E Lee
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - M Kim
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - M J Choi
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - W Lee
- Pohang University of Science and Technology, Pohang 790-784, South Korea
| | - H K Park
- Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea
| | - C W Domier
- University of California at Davis, Davis, California 95616, USA
| | - N C Luhmann
- University of California at Davis, Davis, California 95616, USA
| | - S A Sabbagh
- Columbia University, New York, New York 10027, USA
| | - Y S Park
- Columbia University, New York, New York 10027, USA
| | - S G Lee
- National Fusion Research Institute, Daejeon 305-333, South Korea
| | - J G Bak
- National Fusion Research Institute, Daejeon 305-333, South Korea
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22
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Tobias BJ, Austin ME, Boom JE, Burrell KH, Classen IGJ, Domier CW, Luhmann NC, Nazikian R, Snyder PB. ECE-imaging of the H-mode pedestal (invited). THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:10E329. [PMID: 23126987 DOI: 10.1063/1.4733742] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A synthetic diagnostic has been developed that reproduces the highly structured electron cyclotron emission (ECE) spectrum radiated from the edge region of H-mode discharges. The modeled dependence on local perturbations of the equilibrium plasma pressure allows for interpretation of ECE data for diagnosis of local quantities. Forward modeling of the diagnostic response in this region allows for improved mapping of the observed fluctuations to flux surfaces within the plasma, allowing for the poloidal mode number of coherent structures to be resolved. In addition, other spectral features that are dependent on both T(e) and n(e) contain information about pedestal structure and the electron energy distribution of localized phenomena, such as edge filaments arising during edge-localized mode (ELM) activity.
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Affiliation(s)
- B J Tobias
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA.
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23
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Nam Y, Lee W, Yun GS, Park HK, Elbeze D, Segui JL, Sabot R, Chenevoix JP. Design of the reflective optics for Tore Supra ECEI system. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:10E318. [PMID: 23126976 DOI: 10.1063/1.4732852] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A 2D electron cyclotron emission (ECE) imaging system for Tore Supra is under design for studying the MHD physics of the magnetically confined plasma such as sawteeth, tearing modes, and turbulent fluctuations. Complex beam path due to the tight access in Tore Supra led to the design of reflective optics made of 6 or more large cylindrical∕flat mirrors. The total path length of the ECE beam is about 11 m, including almost 4 m inside the vacuum vessel. The imaging property of the optics has been estimated using the Gaussian beam simulation and ray transfer analysis. The possible setups for the optical alignment of the diagnostic and the operation scenarios with single- or dual-array measurement system are discussed.
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Affiliation(s)
- Y Nam
- Department of Physics, POSTECH, Pohang, Gyeongbuk 790-784, South Korea
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24
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Yun G, Lee W, Choi M, Lee J, Choe G, Park H, Domier C, Luhmann N, Donné AJH, Lee J, Park S, Joung M, Bae Y, Jeon Y, Yoon S. Visualization of core and edge MHD instabilities in 2D using ECEI. EPJ WEB OF CONFERENCES 2012. [DOI: 10.1051/epjconf/20123203002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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