| Optimization of X-mode electron cyclotron current drive in high-electron-temperature plasma in the EAST tokamak |
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| 作者姓名： | Hanlin WANG |
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| 作者单位： | 1. Institute of Plasma Physics, Chinese Academy of Sciences;2. University of Science and Technology of China;3. CEA, Institute for Magnetic Fusion Research;4. EPFL, Swiss Plasma Center |
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| 基金项目： | This work is supported by the National Key R&D Program of China (Nos. 2017YFE0300500 and 2017YFE0300503) and the Comprehensive Research Facility for Fusion Technology Program of China (No. 2018-000052-73-01-001228). |
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| 摘 要： | A discharge with electron temperature up to 14 keV has been achieved in EAST. Analysis of the electron cyclotron current drive(ECCD) efficiency at high electron temperature under EAST parameters is presented using C3PO/LUKE code. Simulation results show that the ECCD efficiency of X-mode increases with central electron temperature up to 10 keV and then starts to decrease above 10 keV, at a specific magnetic field and toroidal angle. The efficiency degradation is due to the presence of the third ...
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Optimization of X-mode electron cyclotron current drive in high-electron-temperature plasma in the EAST tokamak |
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| Affiliation: | 1. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China 2.University of Science and Technology of China, Hefei 230026, People's Republic of China 3. CEA, Institute for Magnetic Fusion Research, Saint-Paul-Lez-Durance F-13108, France 4. EPFL, Swiss Plasma Center, Lausanne 1018, Switzerland |
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| Abstract: | A discharge with electron temperature up to 14 keV has been achieved in EAST. Analysis of the electron cyclotron current drive (ECCD) efficiency at high electron temperature under EAST parameters is presented using C3PO/LUKE code. Simulation results show that the ECCD efficiency of X-mode increases with central electron temperature up to 10 keV and then starts to decrease above 10 keV, at a specific magnetic field and toroidal angle. The efficiency degradation is due to the presence of the third harmonic extraordinary (X3) downshifted absorption at the low field side (LFS); even the cold resonance of X3 mode is located outside the plasma. As the electron temperature increases from 5 to 20 keV, the X3 absorption increases from 0.9% to 96.4%. The trapping electron effect at the LFS produces a reverse Ohkawa current. The competition between the Fisch–Boozer current drive and the Ohkawa current drive results in a decrease in ECCD efficiency. ECCD efficiency optimization is achieved through two methods. One is to increase the toroidal angle, leading to X2 mode predominating again over X3 mode and the electron resonance domain of X2 mode moving far from the trapped/passing boundary. The second one is to increase the magnetic field to move away the X3 resonance layer from the plasma, hence less EC power absorbed by X3 mode. |
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