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Deng WC, Shi ZB, Shi PW, Yang ZC, Chen W, Huang M, Zhang F, Yu X, Jiang M, Wen J, Liang AS, Shen YQ, Zhou Y, Tong RH, Zhong WL. Preliminary results of the 105 GHz collective Thomson scattering system on HL-2A. Rev Sci Instrum 2023; 94:094701. [PMID: 37668510 DOI: 10.1063/5.0150123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Accepted: 08/17/2023] [Indexed: 09/06/2023]
Abstract
A 105 GHz collective Thomson scattering (CTS) diagnostic has been successfully developed for fast-ion measurements on the HL-2A tokamak, and it has been deployed during an experimental campaign. Enhanced signals exhibiting synchronous modulation characteristics have been observed across all CTS channels upon the launch of a modulated probe wave. Results show that the intensity of the CTS signal increases with Neutral Beam Injection (NBI) power and is proportional to neutron count, indicating that the scattering signal contains a contribution from fast ions. Compared with the signal without NBI, the enhanced scattering spectrum due to NBI is slightly wider than the predicted fast ion range. Such broadening might be attributed to the heating effects of the gyrotron.
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Affiliation(s)
- W C Deng
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z B Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - P W Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z C Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W Chen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - M Huang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - F Zhang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - X Yu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - M Jiang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - J Wen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - A S Liang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y Q Shen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y Zhou
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - R H Tong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W L Zhong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
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2
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Shen YQ, Yang ZC, Zhong WL, Jiang M, Shi ZB, Santos J, Shi PW, Tong RH, Xue GQ, Zhou Y, Wen J, Yu X, Deng WC, Wang S, Yang ZJ, Chen ZY, Li D, Zha XQ, Jin ZY, Xu X, Xu M. Plasma position measurements by O-mode and X-mode reflectometry systems in tokamak plasmas. Rev Sci Instrum 2023; 94:063505. [PMID: 37862534 DOI: 10.1063/5.0140390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 06/07/2023] [Indexed: 10/22/2023]
Abstract
Plasma Position Reflectometry (PPR) is planned to provide plasma position and shape information for plasma operation in future fusion reactors. Its primary function is to calibrate the drift of the magnetic signals due to the integral nature of magnetic measurement. Here, we attempt to measure plasma position using ordinary mode (O-mode) and extraordinary mode (X-mode) reflectometry systems on two tokamaks. A new physical model based on the phase shift is proposed to deduce the relative movement of the cut-off layer without density inversion. We demonstrate the plasma position measurements by absolute measurement from density profile inversion and relative measurement from phase shift. The combination of X-mode and O-mode reflectometers can minimize the limitations of single polarization reflectometry and further increase the accuracy of plasma position measurement. These results could provide an important technical basis for the further development of a real-time control system based on PPR.
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Affiliation(s)
- Y Q Shen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z C Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W L Zhong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - M Jiang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z B Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - J Santos
- Associação EURATOM/IST, Instituto de Plasmas e Fusão Nuclear-Laboratório Associado, Instituto Superior Técnico, 1049-001 Lisboa, Portugal
| | - P W Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - R H Tong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - G Q Xue
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
- Key Laboratory of Materials Modification by Beams of the Ministry of Education, School of Physics, Dalian University of Technology, Dalian 116024, China
| | - Y Zhou
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
- Department of Engineering Physics, Tsinghua University, Beijing 100084, China
| | - J Wen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - X Yu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W C Deng
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - S Wang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z J Yang
- International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics, State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Z Y Chen
- International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics, State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - D Li
- International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics, State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - X Q Zha
- International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics, State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Z Y Jin
- International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics, State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - X Xu
- International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics, State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - M Xu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
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3
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Shi PW, Yang ZC, Shi ZB, Xu LF, Deng WC, Jiang M, Chen W, Zhong WL, Wen J, Fang KR, Tong RH, Xue GQ, Yu X, Li YG, Ji XQ, Zhang YP, Yang QW, Xu M, Wang ZX, Duan XR. Development of solid state terahertz interferometer for the first plasma on HL-2M tokamak. Rev Sci Instrum 2021; 92:083509. [PMID: 34470419 DOI: 10.1063/5.0055072] [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: 04/25/2021] [Accepted: 07/26/2021] [Indexed: 06/13/2023]
Abstract
A solid state terahertz interferometer has been developed on the recent commissioned HL-2M tokamak. It can work in a wide frequency region of 220-325 GHz, and the terahertz wave is generated from a low frequency phase locked voltage controlled oscillator with the frequency multiplying technique. A phase processor based on field programmable gate array (FPGA) technology is designed for the heterodyne interferometer, and it contributes to real-time display of electron density. To extract phase information, a novel numerical algorithm related to fast Fourier transform is written on the FPGA chip and enables one to obtain phase shift without being affected by amplitude variation induced by plasma absorption or frequency modulation from the outer electromagnetic environment. The interferometer achieves minimum measurable electron density in the order of 1016 m-3. With the plasma diagnosis, electron density and low frequency tearing mode have been measured during the first experimental campaign.
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Affiliation(s)
- P W Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z C Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z B Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - L F Xu
- The Engineering and Technical College of Chengdu University of Technology, Leshan 614000, China
| | - W C Deng
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - M Jiang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W Chen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W L Zhong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - J Wen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - K R Fang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - R H Tong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - G Q Xue
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - X Yu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y G Li
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - X Q Ji
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y P Zhang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Q W Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - M Xu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z X Wang
- Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, China
| | - X R Duan
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
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4
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Wen J, Shi ZB, Zhong WL, Yang ZC, Yang ZJ, Wang B, Jiang M, Shi PW, Hillesheim JC, Freethy SJ, Shi P, Liang AS, Tong RH, Fang KR, Deng WC, Liu Y, Yang QW, Ding XT, Xu M. A remote gain controlled and polarization angle tunable Doppler backward scattering reflectometer. Rev Sci Instrum 2021; 92:063513. [PMID: 34243534 DOI: 10.1063/5.0043676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 05/15/2021] [Indexed: 06/13/2023]
Abstract
Remote control of the diagnostic systems is the basic requirement for the high performance plasma operation in a fusion device. This work presents the development of the remote control system for the multichannel Doppler backward scattering (DBS) reflectometers. It includes a remote controlled quasi-optical system and a remote intermediate frequency (IF) amplifier gain control system. The quasi-optical system contains a rotational polarizer, its polarization angle is tunable through a remote controlled motor, and it could combine the microwave beams with a wide frequency range into one focused beam. The remote IF gain control system utilizes the digital microcontroller (MCU) technique to regulate the signal amplitude for each signal channel. The gain parameters of amplifiers are adjustable, and the feedback of working status in the IF system will be sent to MCU in real time for safe operation. The gain parameters could be controlled either by the Ethernet remote way or directly through the local control interface on the system. Preliminary experimental results show the effectiveness of the remote controlled multichannel DBS system.
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Affiliation(s)
- J Wen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z B Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W L Zhong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z C Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z J Yang
- Huazhong University of Science and Technology, Wuhan 430074, China
| | - B Wang
- University of Electronic Science and Technology of China, Chengdu 610054, China
| | - M Jiang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - P W Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - J C Hillesheim
- Culham Centre for Fusion Energy, Abingdon, Oxon OX14 3DB, United Kingdom
| | - S J Freethy
- Culham Centre for Fusion Energy, Abingdon, Oxon OX14 3DB, United Kingdom
| | - P Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - A S Liang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - R H Tong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - K R Fang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W C Deng
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y Liu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Q W Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - X T Ding
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - M Xu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
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Fang KR, Shi ZB, Yang ZC, Jiang M, Zhong WL, Wen J, Shi PW, Li YG, Liu ZT, Liu Y, Ding XT, Yang QW, Xu M. An eight-channel correlation electron cyclotron emission diagnostic for turbulent electron temperature fluctuation measurement in HL-2A tokamak. Rev Sci Instrum 2019; 90:063503. [PMID: 31255033 DOI: 10.1063/1.5091453] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 05/20/2019] [Indexed: 06/09/2023]
Abstract
A new correlation electron cyclotron emission (CECE) diagnostic has recently been installed on the HL-2A tokamak in order to study electron temperature fluctuations. Eight radial locations are measured simultaneously through eight pairs of correlated channels. Multiplexers are employed in the intermediate frequency section instead of the conventional separated filter banks to meet strict cross-isolation specifications and lower insertion loss. Relative electron temperature fluctuations are observed by CECE for the first time on the HL-2A by using the spectral decorrelation method. The achieved minimum detectable fluctuation level is up to (T̃e/Te)min∼0.5%. When studying electron temperature fluctuations in the core region with gas puffing, the cross-power spectra show that the amplitude of the electron temperature fluctuation increases in a high temperature and low density plasma. Further analysis demonstrates that the electron temperature gradient ∇Te drives the electron temperature fluctuations together with electron heat transport.
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Affiliation(s)
- K R Fang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z B Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z C Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - M Jiang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W L Zhong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - J Wen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - P W Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y G Li
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z T Liu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y Liu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - X T Ding
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Q W Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - M Xu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
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Zhong WL, Shen Y, Zou XL, Gao JM, Shi ZB, Dong JQ, Duan XR, Xu M, Cui ZY, Li YG, Ji XQ, Yu DL, Cheng J, Xiao GL, Jiang M, Yang ZC, Zhang BY, Shi PW, Liu ZT, Song XM, Ding XT, Liu Y. Observation of Double Impurity Critical Gradients for Electromagnetic Turbulence Excitation in Tokamak Plasmas. Phys Rev Lett 2016; 117:045001. [PMID: 27494476 DOI: 10.1103/physrevlett.117.045001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Indexed: 06/06/2023]
Abstract
The impact of impurity ions on a pedestal has been investigated in the HL-2A Tokamak, at the Southwestern Institute of Physics, Chengdu, China. Experimental results have clearly shown that during the H-mode phase, an electromagnetic turbulence was excited in the edge plasma region, where the impurity ions exhibited a peaked profile. It has been found that double impurity critical gradients are responsible for triggering the turbulence. Strong stiffness of the impurity profile has been observed during cyclic transitions between the I-phase and H-mode regime. The results suggest that the underlying physics of the self-regulated edge impurity profile offers the possibility for an active control of the pedestal dynamics via pedestal turbulence.
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Affiliation(s)
- W L Zhong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - Y Shen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - X L Zou
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
| | - J M Gao
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - Z B Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - J Q Dong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
- Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - X R Duan
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - M Xu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - Z Y Cui
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - Y G Li
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - X Q Ji
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - D L Yu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - J Cheng
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - G L Xiao
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - M Jiang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - Z C Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - B Y Zhang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - P W Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - Z T Liu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - X M Song
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - X T Ding
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
| | - Yong Liu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, People's Republic of China
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7
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Jiang M, Shi ZB, Domier CW, Luhmann NC, Zhong WL, Chen W, Liu ZT, Ding XT, Yang QW, Zhang BY, Yang ZC, Shi PW, Liu Y, Fu BZ, Xu Y. Note: Upgrade of electron cyclotron emission imaging system and preliminary results on HL-2A tokamak. Rev Sci Instrum 2015; 86:076107. [PMID: 26233421 DOI: 10.1063/1.4927072] [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
The electron cyclotron emission imaging system on the HL-2A tokamak has been upgraded to 24 (poloidally) × 16 (radially) channels based on the previous 24 × 8 array. The measurement region can be flexibly shifted due to the independence of the two local oscillator sources, and the field of view can be adjusted easily by changing the position of the zoom lenses. The temporal resolution is about 2.5 μs and the achievable spatial resolution is 1 cm. After laboratory calibration, it was installed on HL-2A tokamak in 2014, and the local 2D mode structures of MHD activities were obtained for the first time.
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Affiliation(s)
- M Jiang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z B Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - 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
| | - W L Zhong
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W Chen
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z T Liu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - X T Ding
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Q W Yang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - B Y Zhang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z C Yang
- School of Physics and Chemistry, Xihua University, Chengdu 610039, China
| | - P W Shi
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y Liu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - B Z Fu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y Xu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
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