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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] [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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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. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:11E134. [PMID: 27910475 DOI: 10.1063/1.4963152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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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Lee WR, Kim HS, Park MK, Lee JH, Kim KH. Synchronized operation by field programmable gate array based signal controller for the Thomson scattering diagnostic system in KSTAR. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:093505. [PMID: 23020374 DOI: 10.1063/1.4752408] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The Thomson scattering diagnostic system is successfully installed in the Korea Superconducting Tokamak Advanced Research (KSTAR) facility. We got the electron temperature and electron density data for the first time in 2011, 4th campaign using a field programmable gate array (FPGA) based signal control board. It operates as a signal generator, a detector, a controller, and a time measuring device. This board produces two configurable trigger pulses to operate Nd:YAG laser system and receives a laser beam detection signal from a photodiode detector. It allows a trigger pulse to be delivered to a time delay module to make a scattered signal measurement, measuring an asynchronous time value between the KSTAR timing board and the laser system injection signal. All functions are controlled by the embedded processor running on operating system within a single FPGA. It provides Ethernet communication interface and is configured with standard middleware to integrate with KSTAR. This controller has operated for two experimental campaigns including commissioning and performed the reconfiguration of logic designs to accommodate varying experimental situation without hardware rebuilding.
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Affiliation(s)
- W R Lee
- National Fusion Research Institute, Gwahangno 113, Daejeon 305-333, South Korea
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Jeong SH, Chang DH, Kim TS, In SR, Lee KW, Jin JT, Chang DS, Oh BH, Bae YS, Kim JS, Park HT, Watanabe K, Inoue T, Kashiwagi M, Dairaku M, Tobari H, Hanada M. First neutral beam injection experiments on KSTAR tokamak. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:02B102. [PMID: 22380259 DOI: 10.1063/1.3660254] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The first neutral beam (NB) injection system of the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak was partially completed in 2010 with only 1∕3 of its full design capability, and NB heating experiments were carried out during the 2010 KSTAR operation campaign. The ion source is composed of a JAEA bucket plasma generator and a KAERI large multi-aperture accelerator assembly, which is designed to deliver a 1.5 MW, NB power of deuterium at 95 keV. Before the beam injection experiments, discharge, and beam extraction characteristics of the ion source were investigated. The ion source has good beam optics in a broad range of beam perveance. The optimum perveance is 1.1-1.3 μP, and the minimum beam divergence angle measured by the Doppler shift spectroscopy is 0.8°. The ion species ratio is D(+):D(2)(+):D(3)(+) = 75:20:5 at beam current density of 85 mA/cm(2). The arc efficiency is more than 1.0 A∕kW. In the 2010 KSTAR campaign, a deuterium NB power of 0.7-1.5 MW was successfully injected into the KSTAR plasma with a beam energy of 70-90 keV. L-H transitions were observed within a wide range of beam powers relative to a threshold value. The edge pedestal formation in the T(i) and T(e) profiles was verified through CES and electron cyclotron emission diagnostics. In every deuterium NB injection, a burst of D-D neutrons was recorded, and increases in the ion temperature and plasma stored energy were found.
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Affiliation(s)
- S H Jeong
- Korea Atomic Energy Research Institute (KAERI), 989-111 Daedeokdaero, Yuseong-gu, Daejeon 305-353, South Korea.
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