1
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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. Rev Sci Instrum 2022; 93:113509. [PMID: 36461457 DOI: 10.1063/5.0099170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 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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2
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Na YS, Seo J, Lee Y, Choi G, Park M, Park S, Yi S, Wang W, Yoo MG, Cha M, Kim B, Lee YH, Han H, Kim B, Lee C, Kim S, Yang S, Byun CS, Kim HS, Ko J, Lee W, Hahm TS. Observation of a new type of self-generated current in magnetized plasmas. Nat Commun 2022; 13:6477. [PMID: 36309494 PMCID: PMC9617975 DOI: 10.1038/s41467-022-34092-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [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: 04/13/2022] [Accepted: 10/12/2022] [Indexed: 11/21/2022] Open
Abstract
A tokamak, a torus-shaped nuclear fusion device, needs an electric current in the plasma to produce magnetic field in the poloidal direction for confining fusion plasmas. Plasma current is conventionally generated by electromagnetic induction. However, for a steady-state fusion reactor, minimizing the inductive current is essential to extend the tokamak operating duration. Several non-inductive current drive schemes have been developed for steady-state operations such as radio-frequency waves and neutral beams. However, commercial reactors require minimal use of these external sources to maximize the fusion gain, Q, the ratio of the fusion power to the external power. Apart from these external current drives, a self-generated current, so-called bootstrap current, was predicted theoretically and demonstrated experimentally. Here, we reveal another self-generated current that can exist in a tokamak and this has not yet been discussed by present theories. We report conclusive experimental evidence of this self-generated current observed in the KSTAR tokamak. Fusion devices like tokamaks require plasma current to generate magnetic field for plasma confinement. Here the authors report an observation of a self-generated anomalous current that contributes up to 30% of the total current in the fusion plasma at KSTAR.
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Affiliation(s)
- Yong-Su Na
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea.
| | - Jaemin Seo
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea.,Princeton University, Princeton, NJ, 08544, USA
| | - Yoonji Lee
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea
| | - Gyungjin Choi
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea
| | - Minseo Park
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea.,Korea Institute of Fusion Energy, Daejeon, 305-333, Republic of Korea
| | - Sangjin Park
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea
| | - Sumin Yi
- Korea Institute of Fusion Energy, Daejeon, 305-333, Republic of Korea
| | - Weixing Wang
- Princeton Plasma Physics Laboratory, Princeton, NJ, 08540, USA
| | - Min-Gu Yoo
- Princeton Plasma Physics Laboratory, Princeton, NJ, 08540, USA.,General Atomics, San Diego, CA, 85608, USA
| | - Minsoo Cha
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea
| | - Beomsu Kim
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea
| | - Young-Ho Lee
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea.,Korea Institute of Fusion Energy, Daejeon, 305-333, Republic of Korea
| | - Hyunsun Han
- Korea Institute of Fusion Energy, Daejeon, 305-333, Republic of Korea
| | - Boseong Kim
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea.,Korea Institute of Fusion Energy, Daejeon, 305-333, Republic of Korea
| | - Chanyoung Lee
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea.,Korea Institute of Fusion Energy, Daejeon, 305-333, Republic of Korea
| | - SangKyeun Kim
- Princeton University, Princeton, NJ, 08544, USA.,Princeton Plasma Physics Laboratory, Princeton, NJ, 08540, USA
| | - SeongMoo Yang
- Princeton Plasma Physics Laboratory, Princeton, NJ, 08540, USA
| | - Cheol-Sik Byun
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea.,Korea Institute of Fusion Energy, Daejeon, 305-333, Republic of Korea
| | - Hyun-Seok Kim
- Korea Institute of Fusion Energy, Daejeon, 305-333, Republic of Korea
| | - Jinseok Ko
- Korea Institute of Fusion Energy, Daejeon, 305-333, Republic of Korea
| | - Woochang Lee
- Korea Institute of Fusion Energy, Daejeon, 305-333, Republic of Korea
| | - Taik Soo Hahm
- Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea
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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] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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4
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Lee GH, Lee JS, Kim DH, Nashuha SH, Kim MJ, Min BC, Lee JH, Lee WC, Yun GS, Kim TG, Kim BT, Choi HC, Park HK, In YK, Kim KW. W-Band Modular Antenna/Detector Array for the Electron Cyclotron Emission Imaging System in KSTAR. Applied Sciences 2022; 12:2431. [DOI: 10.3390/app12052431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [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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5
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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6
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Choi MJ, Bardōczi L, Kwon JM, Hahm TS, Park HK, Kim J, Woo M, Park BH, Yun GS, Yoon E, McKee G. Effects of plasma turbulence on the nonlinear evolution of magnetic island in tokamak. Nat Commun 2021; 12:375. [PMID: 33446658 PMCID: PMC7809268 DOI: 10.1038/s41467-020-20652-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [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: 05/11/2020] [Accepted: 12/08/2020] [Indexed: 12/03/2022] Open
Abstract
Magnetic islands (MIs), resulting from a magnetic field reconnection, are ubiquitous structures in magnetized plasmas. In tokamak plasmas, recent researches suggested that the interaction between an MI and ambient turbulence can be important for the nonlinear MI evolution, but a lack of detailed experimental observations and analyses has prevented further understanding. Here, we provide comprehensive observations such as turbulence spreading into an MI and turbulence enhancement at the reconnection site, elucidating intricate effects of plasma turbulence on the nonlinear MI evolution. Magnetic reconnection and plasma turbulence occur in atmospheric and magnetized laboratory plasmas. Here the authors report evolution of magnetic islands and plasma turbulence in tokamak plasmas using high resolution 2D electron cyclotron emission diagnostics.
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Affiliation(s)
- Minjun J Choi
- Korea Institute of Fusion Energy, Daejeon, 34133, Republic of Korea.
| | - Lāszlo Bardōczi
- General Atomics, P.O. Box 85608, San Diego, CA, 92186-5608, USA
| | - Jae-Min Kwon
- Korea Institute of Fusion Energy, Daejeon, 34133, Republic of Korea
| | - T S Hahm
- Seoul National University, Seoul, 08826, Republic of Korea
| | - Hyeon K Park
- Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Jayhyun Kim
- Korea Institute of Fusion Energy, Daejeon, 34133, Republic of Korea
| | - Minho Woo
- Korea Institute of Fusion Energy, Daejeon, 34133, Republic of Korea
| | - Byoung-Ho Park
- Korea Institute of Fusion Energy, Daejeon, 34133, Republic of Korea
| | - Gunsu S Yun
- Pohang University of Science and Technology, Pohang, Gyeongbuk, 37673, Republic of Korea
| | - Eisung Yoon
- Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - George McKee
- General Atomics, P.O. Box 85608, San Diego, CA, 92186-5608, USA
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7
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Lee GH, Kim DH, Mohyuddin W, Kumar S, Choi HC, Kim KW. Wideband bended CPS‐to‐microstrip transition for millimeter‐wave antenna‐detector module. Micro & Optical Tech Letters 2020; 62:1991-1996. [DOI: 10.1002/mop.32255] [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: 04/22/2019] [Accepted: 01/08/2020] [Indexed: 10/24/2023]
Abstract
AbstractIn this article, the design of a new compact transition with two bended structures for millimeter‐wave (W/F‐band) antenna‐detector module is presented. The millimeter‐wave antenna is a dual dipole antenna fed by a coplanar stripline (CPS). Due to small size of the antenna‐detector, the CPS line impedance tends to be very high (~160 Ω). The down‐converted broadband microwave signal in the CPS is channeled to a 50 Ω microstrip line using a CPS‐to‐microstrip line transition (balun). If the start frequency of the transition is low, the conventional straight balun tends to be very long. In order to reduce transition length, the transition with bended parts while optimizing the impedance tapering based on the analytical formulas (conformal mapping) is chosen. In the proposed transition design, a transition with two bends in 120° is designed and implemented. The measured results show the maximum insertion loss of 1.5 dB in the frequency range of 1.8 to 17.8 GHz. Also, the return loss of the proposed transition is greater than 10 dB from 1.8 to 20 GHz.
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Affiliation(s)
- Gwan Hui Lee
- School of Electronics Engineering Kyungpook National University Daegu Republic of Korea
| | - Dong Hwi Kim
- School of Electronics Engineering Kyungpook National University Daegu Republic of Korea
| | - Wahab Mohyuddin
- Research Institute for Microwave and Millimeter‐Wave Studies, National University of Sciences and Technology Islamabad Pakistan
| | - Sachin Kumar
- School of Electronics Engineering Kyungpook National University Daegu Republic of Korea
| | - Hyun Chul Choi
- School of Electronics Engineering Kyungpook National University Daegu Republic of Korea
| | - Kang Wook Kim
- School of Electronics Engineering Kyungpook National University Daegu Republic of Korea
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8
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Yang Z, Zhou J, Pan X, Cao J, Yu G, Domier C, Zhu Y, Chang F, Zhang Z, Gao Y, Luhmann N, Xie X. Development of intelligent control module for the J-TEXT electron cyclotron emission imaging system. Fusion Engineering and Design 2020. [DOI: 10.1016/j.fusengdes.2020.111494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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9
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Lee DJ, Lee W, Park HK, Kim TG. A large-aperture strip-grid beam splitter for partially combined two millimeter-wave diagnostics on Korea Superconducting Tokamak Advanced Research. Rev Sci Instrum 2019; 90:014703. [PMID: 30709233 DOI: 10.1063/1.5066611] [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: 10/16/2018] [Accepted: 12/13/2018] [Indexed: 06/09/2023]
Abstract
A large-aperture beam splitter has been developed for simultaneous operation of two millimeter-wave diagnostics employing different probe beams in the frequency and polarization, microwave imaging reflectometer (∼85 GHz X-mode), and collective scattering system (300 GHz O-mode), on the Korea Superconducting Tokamak Advanced Research device. The beam splitter was designed based on a polarizer concept (i.e., grid of metal strips on a thin dielectric sheet), and this can be an optimal solution for these two diagnostics. Fabrication of the strips with uniform sub-millimeter width and spacing on a large dielectric sheet was achieved with an etching technique, and the laboratory test results on the reflection and transmission ratio are in good agreement with design values.
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Affiliation(s)
- D J Lee
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - W Lee
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - H K Park
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - T G Kim
- School of Electronics Engineering, Kyungpook National University, Daegu 41566, South Korea
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10
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Mohyuddin W, Kim DH, Choi HC, Kim KW. Comparative Study of Square and Circular Loop Frequency Selective Surfaces for Millimeter-Wave Imaging Diagnostics Systems. Sensors (Basel) 2018; 18:E3079. [PMID: 30217059 DOI: 10.3390/s18093079] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 08/16/2018] [Accepted: 09/10/2018] [Indexed: 12/01/2022]
Abstract
A design method of large-sized square-loop and circular-loop frequency selective surface (FSS) filters for protection of mm-wave imagining receivers is presented. Due to fine cell structure requirements, the performance of the FSS structures at mm-wave frequencies can be significantly affected by fabrication tolerances, especially involved with large-size panel fabrication. Through a comprehensive parametric variation study on the performance of square-loop and circular-loop FSS structures, it is found that the circular-loop FSS structure performs much less sensitively to the fabrication tolerances, thereby producing better and consistent performances with given design values. As a design example, square-loop and circular-loop notch filters resonating at 105 GHz were designed and the performances were evaluated with multiple prototypes. The resonant frequencies of the implemented circular-loop FSS filters deviated by only about 0.5 GHz from the accurate designed value, which can be easily adjusted in the design process. The implemented square-loop and circular loop FSS filters provided low-loss in the pass-band and high rejection of 23 dB at the resonant frequency with good oblique angle performance.
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11
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Mohyuddin W, Woo DS, Choi HC, Kim KW. A practical double-sided frequency selective surface for millimeter-wave applications. Rev Sci Instrum 2018; 89:024703. [PMID: 29495816 DOI: 10.1063/1.5023406] [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] [Indexed: 06/08/2023]
Abstract
Analysis, design, and implementation of a practical, high-rejection frequency selective surface (FSS) are presented in this paper. An equivalent circuit model is introduced for predicting the frequency response of the FSS. The FSS consists of periodic square loop structures fabricated on both sides of the thin dielectric substrate by using the low-cost chemical etching technique. The proposed FSS possesses band-stop characteristics and is implemented to suppress the 170 GHz signal with attenuation of more than 45 dB with insensitivity to an angle of incident plane wave over 20°. Good agreement is observed among calculated, simulated, and measured results. The proposed FSS filter can be used in various millimeter-wave applications such as the protection of imaging diagnostic systems from high spurious input power.
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Affiliation(s)
- Wahab Mohyuddin
- School of Electronics Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, South Korea
| | - Dong Sik Woo
- Department of Aviation Information and Communications Engineering, Kyungwoon University, 730 Gangdong-ro, Sandong-myeon, Gumi 39160, South Korea
| | - Hyun Chul Choi
- School of Electronics Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, South Korea
| | - Kang Wook Kim
- School of Electronics Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, South Korea
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12
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Chen C, Sun S, Ji X, Yin Z. Development of a real time magnetic island identification system for HL-2A tokamak. Rev Sci Instrum 2017; 88:083510. [PMID: 28863647 DOI: 10.1063/1.4997958] [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: 06/07/2023]
Abstract
A novel real time magnetic island identification system for HL-2A is introduced. The identification method is based on the measurement of Mirnov probes and the equilibrium flux constructed by the equilibrium fit (EFIT) code. The system consists of an analog front board and a digital processing board connected by a shield cable. Four octal-channel analog-to-digital convertors are utilized for 100 KHz simultaneous sampling of all the probes, and the applications of PCI extensions for Instrumentation platform and reflective memory allow the system to receive EFIT results simultaneously. A high performance field programmable gate array (FPGA) is used to realize the real time identification algorithm. Based on the parallel and pipeline processing of the FPGA, the magnetic island structure can be identified with a cycle time of 3 ms during experiments.
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Affiliation(s)
- Chao Chen
- State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Shan Sun
- State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Xiaoquan Ji
- Southwestern Institute of Physics, Chengdu 610041, People's Republic of China
| | - Zejie Yin
- State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei 230026, People's Republic of China
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13
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Lee JE, Yun GS, Lee W, Kim MH, Choi M, Lee J, Kim M, Park HK, Bak JG, Ko WH, Park YS. Solitary perturbations in the steep boundary of magnetized toroidal plasma. Sci Rep 2017; 7:45075. [PMID: 28338046 DOI: 10.1038/srep45075] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 02/20/2017] [Indexed: 11/08/2022] Open
Abstract
Solitary perturbations (SPs) localized both poloidally and radially are detected within ~100 μs before the partial collapse of the high pressure gradient boundary region (called pedestal) of magnetized toroidal plasma in the KSTAR tokamak device. The SP develops with a low toroidal mode number (typically unity) in the pedestal ingrained with quasi-stable edge-localized mode (QSM) which commonly appears during the inter-collapse period. The SPs have smaller mode pitch and different (often opposite) rotation velocity compared to the QSMs. Similar solitary perturbations are also frequently observed before the onset of complete pedestal collapse, suggesting a strong connection between the SP generation and the pedestal collapse.
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14
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Kim DH, Mohyuddin W, Woo DS, Choi HC, Kim KW. Design of a 75-140 GHz high-pass printed circuit board dichroic filter. Rev Sci Instrum 2017; 88:034704. [PMID: 28372442 DOI: 10.1063/1.4977935] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A new high-performing PCB (Printed Circuit Board) dichroic filter, which can be used for the KSTAR (Korea Superconducting Tokamak Advanced Research) electron cyclotron emission imaging system, is proposed. The current dichroic filter consists of a triangular lattice array of circular holes on the 6-mm thick metal plate, while circular hole spacing limitation caused relatively narrow passband (∼20 GHz). On the other hand, the proposed PCB dichroic filter utilizes the inexpensive commercial PCB fabrication process with a flexible adjustment of circular hole spacing. Therefore, the proposed PCB dichroic filter provides significantly wider passband (∼60 GHz with 0.84 dB insertion loss) with much reduced weight and expense. Also, it is shown that a steep skirt property can be obtained with the thick PCB filter substrate. The design process, fabrication, and measurement results of the new PCB dichroic filter are described.
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Affiliation(s)
- Dong Hwi Kim
- School of Electronics Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, 41566 Daegu, South Korea
| | - Wahab Mohyuddin
- School of Electronics Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, 41566 Daegu, South Korea
| | - Dong Sik Woo
- Department of Aviation Information and Communications Engineering, Kyungwoon University, 730, Gangdong-ro, Sandong-myeon, 39160 Gumi, South Korea
| | - Hyun Chul Choi
- School of Electronics Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, 41566 Daegu, South Korea
| | - Kang Wook Kim
- School of Electronics Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, 41566 Daegu, South Korea
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15
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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. Rev Sci Instrum 2016; 87:11E135. [PMID: 27910691 DOI: 10.1063/1.4962941] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [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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16
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Lee W, Leem J, Yun GS, Park HK, Ko SH, Wang WX, Budny RV, Luhmann NC, Kim KW. Ion gyroscale fluctuation measurement with microwave imaging reflectometer on KSTAR. Rev Sci Instrum 2016; 87:11E134. [PMID: 27910475 DOI: 10.1063/1.4963152] [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: 06/06/2023]
Abstract
Ion gyroscale turbulent fluctuations with the poloidal wavenumber kθ ∼ 3 cm-1 have been measured in the core region of the neutral beam (NB) injected low confinement (L-mode) plasmas on Korea superconducting tokamak advanced research. The turbulence poloidal wavenumbers are deduced from the frequencies and poloidal rotation velocities in the laboratory frame, measured by the multichannel microwave imaging reflectometer. Linear and nonlinear gyrokinetic simulations also predict the unstable modes with the normalized wavenumber kθρs ∼ 0.4, consistent with the measurement. Comparison of the measured frequencies with the intrinsic mode frequencies from the linear simulations indicates that the measured ones are primarily due to the E × B flow velocity in the NB-injected fast rotating plasmas.
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Affiliation(s)
- W Lee
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - J Leem
- Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea
| | - G S Yun
- Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea
| | - H K Park
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - S H Ko
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - W X Wang
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - R V Budny
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - N C Luhmann
- University of California at Davis, Davis, California 95616, USA
| | - K W Kim
- Kyungpook National University, Daegu 41566, South Korea
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17
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Nam YB, Lee DJ, Lee J, Kim C, Yun GS, Lee W, Park HK. New compact and efficient local oscillator optic system for the KSTAR electron cyclotron emission imaging system. Rev Sci Instrum 2016; 87:11E130. [PMID: 27910535 DOI: 10.1063/1.4961290] [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] [Indexed: 06/06/2023]
Abstract
Electron cyclotron emission imaging (ECEI) diagnostic on Korean Superconducting Tokamak Advanced Research utilizes quasi-optical heterodyne-detection method to measure 2D (vertical and radial) Te fluctuations from two toroidally separated poloidal cross section of the plasma. A cylindrical lens local oscillator (LO) optics with optical path length (OPL) 2-2.5 m has been used in the current ECEI system to couple the LO source to the 24 vertically aligned array of ECE detectors. For efficient and compact LO optics employing the Powell lens is proposed so that the OPL of the LO source is significantly reduced from ∼2.0 m to 0.4 m with new optics. The coupling efficiency of the LO source is expected to be improved especially at the edge channels. Results from the optical simulation together with the laboratory test of the prototype optics will be discussed in this paper.
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Affiliation(s)
- Y B Nam
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, South Korea
| | - D J Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - J Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - C Kim
- Pennsylvania State University, Old Main, State College, Pennsylvania 16801, USA
| | - G S Yun
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, South Korea
| | - W Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - H K Park
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
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18
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Pan XM, Yang ZJ, Ma XD, Zhu YL, Luhmann NC, Domier CW, Ruan BW, Zhuang G. Design of the 2D electron cyclotron emission imaging instrument for the J-TEXT tokamak. Rev Sci Instrum 2016; 87:11E106. [PMID: 27910430 DOI: 10.1063/1.4959875] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A new 2D Electron Cyclotron Emission Imaging (ECEI) diagnostic is being developed for the J-TEXT tokamak. It will provide the 2D electron temperature information with high spatial, temporal, and temperature resolution. The new ECEI instrument is being designed to support fundamental physics investigations on J-TEXT including MHD, disruption prediction, and energy transport. The diagnostic contains two dual dipole antenna arrays corresponding to F band (90-140 GHz) and W band (75-110 GHz), respectively, and comprises a total of 256 channels. The system can observe the same magnetic surface at both the high field side and low field side simultaneously. An advanced optical system has been designed which permits the two arrays to focus on a wide continuous region or two radially separate regions with high imaging spatial resolution. It also incorporates excellent field curvature correction with field curvature adjustment lenses. An overview of the diagnostic and the technical progress including the new remote control technique are presented.
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Affiliation(s)
- X M Pan
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Z J Yang
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - X D Ma
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Y L Zhu
- School of Physics, University of Science and Technology of China, Anhui 230026, China
| | - N C Luhmann
- Davis Millimeter Wave Research Center, University of California, Davis, California 95616, USA
| | - C W Domier
- Davis Millimeter Wave Research Center, University of California, Davis, California 95616, USA
| | - B W Ruan
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - G Zhuang
- State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
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19
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Lee J, Yun GS, Choi MJ, Kwon JM, Jeon YM, Lee W, Luhmann NC, Park HK. Nonlinear Interaction of Edge-Localized Modes and Turbulent Eddies in Toroidal Plasma under n=1 Magnetic Perturbation. Phys Rev Lett 2016; 117:075001. [PMID: 27563970 DOI: 10.1103/physrevlett.117.075001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Indexed: 06/06/2023]
Abstract
The effect of static n=1 resonant magnetic perturbation (RMP) on the spatial structure and temporal dynamics of edge-localized modes (ELMs) and edge turbulence in tokamak plasma has been investigated. Two-dimensional images measured by a millimeter-wave camera on the KSTAR tokamak revealed that the coherent filamentary modes (i.e., ELMs) are still present in the edge region when the usual large scale collapse of the edge confinement, i.e., the ELM crash, is completely suppressed by n=1 RMP. Cross-correlation analyses on the 2D images show that (1) the RMP enhances turbulent fluctuations in the edge toward the ELM-crash-suppression phase, (2) the induced turbulence has a clear dispersion relation for wide ranges of wave number and frequency, and (3) the turbulence involves a net radially outward energy transport. Nonlinear interactions of the turbulent eddies with the coexisting ELMs are clearly observed by bispectral analysis, which implies that the exchange of energy between them may be the key to the prevention of large scale crashes.
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Affiliation(s)
- Jaehyun Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Gunsu S Yun
- Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Minjun J Choi
- National Fusion Research Institute, Daejeon 34133, Republic of Korea
| | - Jae-Min Kwon
- National Fusion Research Institute, Daejeon 34133, Republic of Korea
| | - Young-Mu Jeon
- National Fusion Research Institute, Daejeon 34133, Republic of Korea
| | - Woochang Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | | | - Hyeon K Park
- Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
- National Fusion Research Institute, Daejeon 34133, Republic of Korea
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20
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Lee W, Park HK, Lee DJ, Nam YU, Leem J, Kim TK. Design of a collective scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research. Rev Sci Instrum 2016; 87:043501. [PMID: 27131668 DOI: 10.1063/1.4944834] [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: 06/05/2023]
Abstract
The design characteristics of a multi-channel collective (or coherent) scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research (KSTAR), which is planned to be installed in 2017, are given in this paper. A few critical issues are discussed in depth such as the Faraday and Cotton-Mouton effects on the beam polarization, radial spatial resolution, probe beam frequency, polarization, and power. A proper and feasible optics with the 300 GHz probe beam, which was designed based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wavenumbers up to 24 cm(-1). The upper limit corresponds to the normalized wavenumber kθρe of ∼0.15 in nominal KSTAR plasmas. To detect the scattered beam power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed.
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Affiliation(s)
- W Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - H K Park
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - D J Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - Y U Nam
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - J Leem
- Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea
| | - T K Kim
- Kyunpook National University, Daegu 41566, South Korea
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21
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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. Rev Sci Instrum 2016; 87:013506. [PMID: 26827320 DOI: 10.1063/1.4940030] [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: 11/04/2015] [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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22
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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. Rev Sci Instrum 2014; 85:11D833. [PMID: 25430246 DOI: 10.1063/1.4891061] [Citation(s) in RCA: 2] [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] [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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