An upgraded infrared （IR） imaging system which provides a wide field of view （FOV） has been installed on the Experimental Advanced Superconducting Tokamak （EAST） to monitor the surface temperatures on plasma fac...An upgraded infrared （IR） imaging system which provides a wide field of view （FOV） has been installed on the Experimental Advanced Superconducting Tokamak （EAST） to monitor the surface temperatures on plasma facing components. Modified magnetic topology induced by lower hybrid wave （LHW） can lead to the formation of striated heat flux （SHF} on divertor plates which can be clearly observed by IR camera. In this paper, LHW power modulation is applied to analyze the appearance of SHF. It is also demonstrated that deuterium （D） pellet injection and supersonic molecular beam injection （SMBI） can to some extent reduce the heat flux on the outer strike point （OSP）, but enhance the SHF on lower outer plates （LOP） of divertor. This may provide an optional approach to actively control the distribution of heat flux on diveror plates, which can protect materials from long duration high-heat flux.展开更多
In this work, electron cyclotron emission(ECE) is simulated by using the code SPECE to study the spatial localization of ECE measurement in EAST plasmas heated by lower hybrid wave(LHW).The results indicate that gener...In this work, electron cyclotron emission(ECE) is simulated by using the code SPECE to study the spatial localization of ECE measurement in EAST plasmas heated by lower hybrid wave(LHW).The results indicate that generally there are two emission layers for an individual frequency in plasmas with non-thermal electrons, and they are separately attributed to the thermal electrons and non-thermal electrons. The emission layer due to the thermal electrons is nearly identical to that for the case with Maxwellian distribution. The emission layer due to non-thermal electrons is well localized in the location of the non-thermal electrons. Even though the non-thermal emission layer is broader, the emission intensity is smaller than that from the thermal emission layer for the cases studied in this work. Localized electron temperature fluctuations can still be distinguished by ECE measurement as long as it does not coexist with the non-thermal electrons. Sawtooth inversion radii and tearing mode island location determined respectively by the ECE measurement and the soft x-ray measurement for a LHW-heated plasma show a good agreement, and this indicates that the ECE measurement in the plasma core region is not seriously polluted.展开更多
Study on the characters of energy confinement in both Ohmic and lower hybrid wave （LHW） discharges on EAST is conducted and the linear Ohmic confinement （LOC）, saturated ohmic confinement （SOC） and improved Ohmi...Study on the characters of energy confinement in both Ohmic and lower hybrid wave （LHW） discharges on EAST is conducted and the linear Ohmic confinement （LOC）, saturated ohmic confinement （SOC） and improved Ohmic confinement （IOC） regimes are investigated in this paper. It is observed that an improved confinement mode characterized by both a drop of IDa line intensity and an increase in line average density can be triggered by a gas puffing pulse.展开更多
The core impurity confinement properties are experimentally investigated in the Experimental Advanced Superconducting Tokamak(EAST)plasma heated by lower hybrid wave(LHW)and electron cyclotron resonance heating(ECRH)(...The core impurity confinement properties are experimentally investigated in the Experimental Advanced Superconducting Tokamak(EAST)plasma heated by lower hybrid wave(LHW)and electron cyclotron resonance heating(ECRH)(LHW+ECRH).It is shown that the impurity confinement time(τ_(imp))in the L-mode plasma jointly heated by LHW and ECRH is weakly dependent on electron density but strongly dependent on the heating power,thus it is shorter than that in LHW-only heated L-mode plasma with the similar plasma parameters.The combined heating of LHW and ECRH can reduce the collisionality and indicates a more effective heating method for coreτimp reduction and normalized poloidal beta(βP)^(im)provement.It should be emphasized that in this highβ_P operation window the small ELM regime can be accessed,and an L-mode levelτ_(imp)(40 ms-80 ms)and highβ_N(~1.7)can be obtained simultaneously.It means that this typical small ELMy H-mode regime has an advantage in avoiding the serious tungsten accumulation,and will be competitive in future long-pulse steady-state and high-performance operation with high-Z material plasma-facing components.展开更多
Lower hybrid wave （LHW）-plasma coupling and lower hybrid current drive （LHCD） experiments in divertor, including single-null and double-null, and limiter configurations were conducted systematically in EAST. A max...Lower hybrid wave （LHW）-plasma coupling and lower hybrid current drive （LHCD） experiments in divertor, including single-null and double-null, and limiter configurations were conducted systematically in EAST. A maximum power for launched LHW is 1.4 MW and the plasma current with LHCD is about 1 MA. It is indicated that the coupling is best in limiter configuration, then in single-null one, while worst in double-null one. Study in current drive efficiency by a least squares fit shows that there is no obvious difference in drive efficiency between the double-null and the single-null cases, whereas the efficiency is a slightly lower in the limiter case. The effect of plasma density on the current drive efficiency is due to the influence of density on impurity concentration.展开更多
Thermal behavior of the 2.45 GHz lower hybrid wave （LHW） antenna in EAST is investigated. The temperature distribution of the LHW antenna is obtained using the ANSYS code. The thermal stresses and displacements due ...Thermal behavior of the 2.45 GHz lower hybrid wave （LHW） antenna in EAST is investigated. The temperature distribution of the LHW antenna is obtained using the ANSYS code. The thermal stresses and displacements due to thermal loads are calculated. The tempera- tures measured by the thermocouples in the experiment are also presented. All the results of the simulation are discussed. The simulated results offer guidance for the design and manufacture of the antenna.展开更多
An additional lower hybrid wave （LHW） with a higher refractive index （N//） was investigated in the HT-7 tokamak to bridge the spectral gap. It was found that the spectral gap between the wave and the electrons in ...An additional lower hybrid wave （LHW） with a higher refractive index （N//） was investigated in the HT-7 tokamak to bridge the spectral gap. It was found that the spectral gap between the wave and the electrons in the outer region was bridged by the additional wave with a higher N// spectrum. The results showed that the sawteeth oscillation was suppressed by launching the additional wave, and that the power deposition profile was moved outwards and the current profile was broadened due to the application of the additional wave. Our study indicates that the spectral gap may be bridged by an additional wave with a higher N// spectrum in the outer region.展开更多
基金supported by National Natural Science Foundation of China(No.11275234)the National Magnetic Confinement Fusion Programof China(No.2014GB106001)
文摘An upgraded infrared （IR） imaging system which provides a wide field of view （FOV） has been installed on the Experimental Advanced Superconducting Tokamak （EAST） to monitor the surface temperatures on plasma facing components. Modified magnetic topology induced by lower hybrid wave （LHW） can lead to the formation of striated heat flux （SHF} on divertor plates which can be clearly observed by IR camera. In this paper, LHW power modulation is applied to analyze the appearance of SHF. It is also demonstrated that deuterium （D） pellet injection and supersonic molecular beam injection （SMBI） can to some extent reduce the heat flux on the outer strike point （OSP）, but enhance the SHF on lower outer plates （LOP） of divertor. This may provide an optional approach to actively control the distribution of heat flux on diveror plates, which can protect materials from long duration high-heat flux.
基金supported by National Natural Science Foundation of China (No. 11405211)the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technologysupported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2015GB101003 and 2015GB103002)
文摘In this work, electron cyclotron emission(ECE) is simulated by using the code SPECE to study the spatial localization of ECE measurement in EAST plasmas heated by lower hybrid wave(LHW).The results indicate that generally there are two emission layers for an individual frequency in plasmas with non-thermal electrons, and they are separately attributed to the thermal electrons and non-thermal electrons. The emission layer due to the thermal electrons is nearly identical to that for the case with Maxwellian distribution. The emission layer due to non-thermal electrons is well localized in the location of the non-thermal electrons. Even though the non-thermal emission layer is broader, the emission intensity is smaller than that from the thermal emission layer for the cases studied in this work. Localized electron temperature fluctuations can still be distinguished by ECE measurement as long as it does not coexist with the non-thermal electrons. Sawtooth inversion radii and tearing mode island location determined respectively by the ECE measurement and the soft x-ray measurement for a LHW-heated plasma show a good agreement, and this indicates that the ECE measurement in the plasma core region is not seriously polluted.
基金supported by the National Magnetic Confinement Fhsion Research Program of China （Nos. 2010GB106000 and 2010GB106001）, National Natural Science Foundation of China （No. 10721505）, and in part by the JSPS-CAS Core-University program in the field of ＇Plasma and Nuclear FUsion＇
文摘Study on the characters of energy confinement in both Ohmic and lower hybrid wave （LHW） discharges on EAST is conducted and the linear Ohmic confinement （LOC）, saturated ohmic confinement （SOC） and improved Ohmic confinement （IOC） regimes are investigated in this paper. It is observed that an improved confinement mode characterized by both a drop of IDa line intensity and an increase in line average density can be triggered by a gas puffing pulse.
基金the National Key Research and Development Program of China(Grant Nos.2018YFE031110 and 2017YFE0301205)the National Natural Science Foundation of China(Grant Nos.11905146,11775269,and 11805113)+1 种基金the Users with Excellence Program of Hefei Science Center,Chinese Academy of Sciences(Grant No.2019HSC-UE014)the Fund from the Shenzhen Clean Energy Research Institute,China。
文摘The core impurity confinement properties are experimentally investigated in the Experimental Advanced Superconducting Tokamak(EAST)plasma heated by lower hybrid wave(LHW)and electron cyclotron resonance heating(ECRH)(LHW+ECRH).It is shown that the impurity confinement time(τ_(imp))in the L-mode plasma jointly heated by LHW and ECRH is weakly dependent on electron density but strongly dependent on the heating power,thus it is shorter than that in LHW-only heated L-mode plasma with the similar plasma parameters.The combined heating of LHW and ECRH can reduce the collisionality and indicates a more effective heating method for coreτimp reduction and normalized poloidal beta(βP)^(im)provement.It should be emphasized that in this highβ_P operation window the small ELM regime can be accessed,and an L-mode levelτ_(imp)(40 ms-80 ms)and highβ_N(~1.7)can be obtained simultaneously.It means that this typical small ELMy H-mode regime has an advantage in avoiding the serious tungsten accumulation,and will be competitive in future long-pulse steady-state and high-performance operation with high-Z material plasma-facing components.
基金supported by National Natural Science Foundation of China (Nos. 10875149, 10928509 and 10805057)the National Magnetic confinement Fusion Science Program of China (2010GB105004)+1 种基金the Dean Foundation of Hefei Institute of Physical Science,Chinese Academy of Sciencepartly supported by Core University Program between China and Japan
文摘Lower hybrid wave （LHW）-plasma coupling and lower hybrid current drive （LHCD） experiments in divertor, including single-null and double-null, and limiter configurations were conducted systematically in EAST. A maximum power for launched LHW is 1.4 MW and the plasma current with LHCD is about 1 MA. It is indicated that the coupling is best in limiter configuration, then in single-null one, while worst in double-null one. Study in current drive efficiency by a least squares fit shows that there is no obvious difference in drive efficiency between the double-null and the single-null cases, whereas the efficiency is a slightly lower in the limiter case. The effect of plasma density on the current drive efficiency is due to the influence of density on impurity concentration.
基金supported by National Natural Science Foundation of China (No.10905069)
文摘Thermal behavior of the 2.45 GHz lower hybrid wave （LHW） antenna in EAST is investigated. The temperature distribution of the LHW antenna is obtained using the ANSYS code. The thermal stresses and displacements due to thermal loads are calculated. The tempera- tures measured by the thermocouples in the experiment are also presented. All the results of the simulation are discussed. The simulated results offer guidance for the design and manufacture of the antenna.
基金the Knowledge Innovation Program of the Chinese Academy of Sciences (No.075FCQ0127)National Natural Science Foundation of China (Nos.10575104,10805057)
文摘An additional lower hybrid wave （LHW） with a higher refractive index （N//） was investigated in the HT-7 tokamak to bridge the spectral gap. It was found that the spectral gap between the wave and the electrons in the outer region was bridged by the additional wave with a higher N// spectrum. The results showed that the sawteeth oscillation was suppressed by launching the additional wave, and that the power deposition profile was moved outwards and the current profile was broadened due to the application of the additional wave. Our study indicates that the spectral gap may be bridged by an additional wave with a higher N// spectrum in the outer region.
