At the EAST tokamak, the ion temperature(T_(i)) is observed to be clamped around 1.25 keV in electron cyclotron resonance(ECR)-heated plasmas, even at core electron temperatures up to 10 keV(depending on the ECR heati...At the EAST tokamak, the ion temperature(T_(i)) is observed to be clamped around 1.25 keV in electron cyclotron resonance(ECR)-heated plasmas, even at core electron temperatures up to 10 keV(depending on the ECR heating power and the plasma density). This clamping results from the lack of direct ion heating and high levels of turbulence-driven transport. Turbulent transport analysis shows that trapped electron mode and electron temperature gradient-driven modes are the most unstable modes in the core of ECR-heated H-mode plasmas. Nevertheless, recently it was found that the T_(i)/T_(e)ratio can increase further with the fraction of the neutral beam injection(NBI) power, which leads to a higher core ion temperature(Ti0). In NBI heating-dominant H-mode plasmas, the ion temperature gradient-driven modes become the most unstable modes.Furthermore, a strong and broad internal transport barrier(ITB) can form at the plasma core in high-power NBI-heated H-mode plasmas when the T_(i)/T_(e)ratio approaches ~1, which results in steep core Teand Tiprofiles, as well as a peaked neprofile. Power balance analysis shows a weaker Teprofile stiffness after the formation of ITBs in the core plasma region, where Ticlamping is broken,and the core Tican increase further above 2 keV, which is 80% higher than the value of Ticlamping in ECR-heated plasmas. This finding proposes a possible solution to the problem of Ticlamping on EAST and demonstrates an advanced operational regime with the formation of a strong and broad ITB for future fusion plasmas dominated by electron heating.展开更多
A long pulse electron cyclotron resonance heating（ECRH）system has been developed to meet the requirements of steady-state operation for the EAST superconducting tokamak,and the first EC wave was successfully injecte...A long pulse electron cyclotron resonance heating（ECRH）system has been developed to meet the requirements of steady-state operation for the EAST superconducting tokamak,and the first EC wave was successfully injected into plasma during the 2015 spring campaign.The system is mainly composed of four 140 GHz gyrotron systems,4 ITER-Like transmission lines,4 independent channel launchers and corresponding power supplies,a water cooling,control ＆inter-lock system etc.Each gyrotron is expected to deliver a maximum power of 1 MW and be operated at 100-1000 s pulse lengths.The No.1 and No.2 gyrotron systems have been installed.In the initial commissioning,a series of parameters of 1 MW 1 s,900 k W 10 s,800 k W 95 s and650 k W 753 s have been demonstrated successfully on the No.1 gyrotron system based on calorimetric dummy load measurements.Significant plasma heating and MHD instability suppression effects were observed in EAST experiments.In addition,high confinement（H-mode）discharges triggered by ECRH were obtained.展开更多
In 2021,EAST realized a steady-state long pulse with a duration over 100 s and a core electron temperature over 10 keV.This is an integrated operation that resolves several key issues,including active control of wall ...In 2021,EAST realized a steady-state long pulse with a duration over 100 s and a core electron temperature over 10 keV.This is an integrated operation that resolves several key issues,including active control of wall conditioning,long-lasting fully noninductive current and divertor heat/particle flux.The fully noninductive current is driven by pure radio frequency(RF)waves with a lower hybrid current drive power of 2.5 MW and electron cyclotron resonance heating of 1.4 MW.This is an excellent experimental platform on the timescale of hundreds of seconds for studying multiscale instabilities,electron-dominant transport and particle recycling(plasma-wall interactions)under weak collisionality.展开更多
低杂波电流驱动(Lower Hybrid Current Drive,LHCD)是托卡马克的主要辅助加热与电流驱动方式之一,研究表明,低杂波在刮削层内的边界寄生效应会显著降低低杂波电流驱动效率。其中,边界密度涨落引起的波散射会导致刮削层内的低杂波波谱变...低杂波电流驱动(Lower Hybrid Current Drive,LHCD)是托卡马克的主要辅助加热与电流驱动方式之一,研究表明,低杂波在刮削层内的边界寄生效应会显著降低低杂波电流驱动效率。其中,边界密度涨落引起的波散射会导致刮削层内的低杂波波谱变化,从而改变低杂波功率沉积位置和电流驱动效率。本文使用全波解方法研究全超导托卡马克(Experimental Advanced Superconducting Tokamak,EAST)装置上刮削层内密度涨落导致的低杂波波散射,重点分析不同特征的低频电子密度涨落对波散射的影响。模拟结果表明:密度波包(blob)引起的散射导致低杂波功率流的空间结构的改变,blob造成的背向散射比前向散射更明显;blob内的密度涨落大小主要影响波场扰动幅度,blob的半径主要影响波散射的空间范围,多个blob造成的全场扰动显著增加。展开更多
The blob properties in I-mode and ELM-free H-mode plasmas compared to L-mode have been investigated on the EAST tokamak,including the blob detection rate Nb,sizeδb,lifetimeτb and radial velocity vr,b.The blob proper...The blob properties in I-mode and ELM-free H-mode plasmas compared to L-mode have been investigated on the EAST tokamak,including the blob detection rate Nb,sizeδb,lifetimeτb and radial velocity vr,b.The blob properties in L-mode and I-mode are similar,and those in ELM-free H-mode are different to them.The blob Nbis smaller whileτbis larger in H-mode.The experimental blob sizeδband velocity scalings vr,b-δb show a good agreement with the theoretical models.The variation in blob properties during the L-I and H-L transitions,and their relations to the scrape-off layer(SOL)density,edge and SOL turbulence,and SOL collisionality are discussed.The suppression of the edge(inside the last closed flux surface)turbulence is not reflected in the blob behavior,while the blob detection rate shows a correlation with the SOL density and its low-frequency(3–50 kH z)fluctuations.In addition,the blob detection rate is found to increase with the divertor collisionalityΛdiv,indicating a dependence of blob behavior onΛdiv.The differences in blob detection rates among the three operating regimes might be due to their different SOL densities and collisionalities.The investigation contributes to understanding the influences of edge and SOL plasma parameters on the blob behavior.展开更多
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/...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 ke V,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.展开更多
The efficiency of lower hybrid current drive （LHCD） for limiter and divertor con- figurations in the EAST tokamak is investigated using hot electrical conductivity theory and experimental formulas. The results indic...The efficiency of lower hybrid current drive （LHCD） for limiter and divertor con- figurations in the EAST tokamak is investigated using hot electrical conductivity theory and experimental formulas. The results indicate that the efficiency of current drive in divertor geometry is slightly higher than that in limiter one. To interpret the experimental results, the GENRAY code is applied to calculate the propagation and absorption of the lower hybrid wave （LHW） in different configurations. The numerical results show that the variation in the parallel refractive index （N//） between the two configurations is quite large. Transformer recharging experiments were also successfully conducted in EAST. By means of the Karney-Fisch method, the absorption index （α） and the upshift factor of refraction （β） for the LHW are obtained. In addition, the maximum recharging efficiency in EAST is about 4% in the divertor configuration, with a line-averaged electron density of ne_av=0.7×10^19m^-3展开更多
In recent EAST experiments,current profile broadening characterized by reduced internal inductance has been achieved by utilizing radio-frequency current drives(RFCD).In contrast to previous density scan experiments,w...In recent EAST experiments,current profile broadening characterized by reduced internal inductance has been achieved by utilizing radio-frequency current drives(RFCD).In contrast to previous density scan experiments,which showed an outward shift of the current density profile of lower hybrid current drive(LHCD)in higher plasma density,the core electron temperature(T_(e)(0))is found to affect the LHCD current profile as well.According to equilibrium reconstruction,a significant increase in on-axis safety factor(q0)from 2.05 to 3.41 is observed by careful arrangement of RFCD.Simulations using ray-tracing code GENRAY and Fokker–Planck code CQL3D have been performed to thoroughly analyze the LHCD current profile,revealing the sensitivity of the LHCD current profile to T_(e)(0).The LHCD current density tends to accumulate in the plasma core with higher current drive efficiency benefiting from higher T_(e)(0).With a lower T_(e)(0),the LHCD current profile broadens due to off-axis deposition of power density.The sensitivity of the power deposition and current profile of LHCD to T_(e)(0)provides a promising way to effectively optimize current profile via control of the core electron temperature.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
The optimized synergy conditions between electron cyclotron current drive （ECCD） and lower hybrid current drive （LHCD） with normal parameters of the EAST tokamak are studied by using the C3PO/LUKE code based on th...The optimized synergy conditions between electron cyclotron current drive （ECCD） and lower hybrid current drive （LHCD） with normal parameters of the EAST tokamak are studied by using the C3PO/LUKE code based on the under- standing of the synergy mechanisms so as to obtain a higher synergistic current and provide theoretical reference for the synergistic effect in the EAST experiment. The dependences of the synergistic effect on the parameters of two waves （lower hybrid wave （LHW） and electron cyclotron wave （ECW））, including the radial position of the power deposition, the power value of the LH and EC waves, and the parallel refractive indices of the LHW （Nr） are oresented and discussed.展开更多
基金supported by National Natural Science Foundation of China(No.12135015)the Users with Excellence Program of Hefei Science Center,CAS(No.2021HSCUE012)+3 种基金the National Key R&D Program of China(No.2022Y FE03010003)the Major Science and Technology Infrastructure Maintenance and Reconstruction Projects of the Chinese Academy of Sciences 2021the Special Funds for Improving Conditions for Scientific Research in National Scientific Institutions 2022the China Scholarship Council。
文摘At the EAST tokamak, the ion temperature(T_(i)) is observed to be clamped around 1.25 keV in electron cyclotron resonance(ECR)-heated plasmas, even at core electron temperatures up to 10 keV(depending on the ECR heating power and the plasma density). This clamping results from the lack of direct ion heating and high levels of turbulence-driven transport. Turbulent transport analysis shows that trapped electron mode and electron temperature gradient-driven modes are the most unstable modes in the core of ECR-heated H-mode plasmas. Nevertheless, recently it was found that the T_(i)/T_(e)ratio can increase further with the fraction of the neutral beam injection(NBI) power, which leads to a higher core ion temperature(Ti0). In NBI heating-dominant H-mode plasmas, the ion temperature gradient-driven modes become the most unstable modes.Furthermore, a strong and broad internal transport barrier(ITB) can form at the plasma core in high-power NBI-heated H-mode plasmas when the T_(i)/T_(e)ratio approaches ~1, which results in steep core Teand Tiprofiles, as well as a peaked neprofile. Power balance analysis shows a weaker Teprofile stiffness after the formation of ITBs in the core plasma region, where Ticlamping is broken,and the core Tican increase further above 2 keV, which is 80% higher than the value of Ticlamping in ECR-heated plasmas. This finding proposes a possible solution to the problem of Ticlamping on EAST and demonstrates an advanced operational regime with the formation of a strong and broad ITB for future fusion plasmas dominated by electron heating.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Nos.2011GB102000,2012GB103000 and 2015GB103000)
文摘A long pulse electron cyclotron resonance heating（ECRH）system has been developed to meet the requirements of steady-state operation for the EAST superconducting tokamak,and the first EC wave was successfully injected into plasma during the 2015 spring campaign.The system is mainly composed of four 140 GHz gyrotron systems,4 ITER-Like transmission lines,4 independent channel launchers and corresponding power supplies,a water cooling,control ＆inter-lock system etc.Each gyrotron is expected to deliver a maximum power of 1 MW and be operated at 100-1000 s pulse lengths.The No.1 and No.2 gyrotron systems have been installed.In the initial commissioning,a series of parameters of 1 MW 1 s,900 k W 10 s,800 k W 95 s and650 k W 753 s have been demonstrated successfully on the No.1 gyrotron system based on calorimetric dummy load measurements.Significant plasma heating and MHD instability suppression effects were observed in EAST experiments.In addition,high confinement（H-mode）discharges triggered by ECRH were obtained.
基金the National Key R&D Program of China(No.2022YFE03010003)National Natural Science Foundation of China(No.12275309).
文摘In 2021,EAST realized a steady-state long pulse with a duration over 100 s and a core electron temperature over 10 keV.This is an integrated operation that resolves several key issues,including active control of wall conditioning,long-lasting fully noninductive current and divertor heat/particle flux.The fully noninductive current is driven by pure radio frequency(RF)waves with a lower hybrid current drive power of 2.5 MW and electron cyclotron resonance heating of 1.4 MW.This is an excellent experimental platform on the timescale of hundreds of seconds for studying multiscale instabilities,electron-dominant transport and particle recycling(plasma-wall interactions)under weak collisionality.
基金supported by the National Key R&D Program of China(Nos.2022YFE03020004,2017YFE0301300,2018YFE0303104 and 2019YFE03030000)the Major Science and Technology Infrastructure Maintenance and Reconstruction Projects of the Chinese Academy of Sciences+3 种基金National Natural Science Foundation of China(Nos.12275313,11922513,12005004 and U19A20113)the Institute of Energy,Hefei Comprehensive National Science Center(No.GXXT-2020-004)the Anhui Provincial Natural Science Foundation(No.2008085QA38)the Users with Excellence Program of Hefei Science Center,Chinese Academy of Sciences(No.2020HSC-UE009)。
文摘The blob properties in I-mode and ELM-free H-mode plasmas compared to L-mode have been investigated on the EAST tokamak,including the blob detection rate Nb,sizeδb,lifetimeτb and radial velocity vr,b.The blob properties in L-mode and I-mode are similar,and those in ELM-free H-mode are different to them.The blob Nbis smaller whileτbis larger in H-mode.The experimental blob sizeδband velocity scalings vr,b-δb show a good agreement with the theoretical models.The variation in blob properties during the L-I and H-L transitions,and their relations to the scrape-off layer(SOL)density,edge and SOL turbulence,and SOL collisionality are discussed.The suppression of the edge(inside the last closed flux surface)turbulence is not reflected in the blob behavior,while the blob detection rate shows a correlation with the SOL density and its low-frequency(3–50 kH z)fluctuations.In addition,the blob detection rate is found to increase with the divertor collisionalityΛdiv,indicating a dependence of blob behavior onΛdiv.The differences in blob detection rates among the three operating regimes might be due to their different SOL densities and collisionalities.The investigation contributes to understanding the influences of edge and SOL plasma parameters on the blob behavior.
基金the National Key R&D Program of China(Nos.2017YFE0300500 and 2017YFE0300503)the Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228).
文摘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 ke V,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.
基金supported by National Natural Science Foundation of China (Nos.10875149, 10928509 and 10805057)the National Magnetic Confinement Fusion Science Program of China (No.2010GB105004)
文摘The efficiency of lower hybrid current drive （LHCD） for limiter and divertor con- figurations in the EAST tokamak is investigated using hot electrical conductivity theory and experimental formulas. The results indicate that the efficiency of current drive in divertor geometry is slightly higher than that in limiter one. To interpret the experimental results, the GENRAY code is applied to calculate the propagation and absorption of the lower hybrid wave （LHW） in different configurations. The numerical results show that the variation in the parallel refractive index （N//） between the two configurations is quite large. Transformer recharging experiments were also successfully conducted in EAST. By means of the Karney-Fisch method, the absorption index （α） and the upshift factor of refraction （β） for the LHW are obtained. In addition, the maximum recharging efficiency in EAST is about 4% in the divertor configuration, with a line-averaged electron density of ne_av=0.7×10^19m^-3
基金supported by the National MCF Energy R&D Program of China (No. 2019YFE0304000)National Natural Science Foundation of China (Nos. 12005262 and 11975274)+3 种基金the Anhui Provincial Natural Science Foundation (No. 2108085J06)the Users with Excellence Program of Hefei Science Center CAS (Nos. 2021HSC-UE018 and 2020HSC-UE011)the External Cooperation Program of Chinese Academy of Sciences (No. 116134KYSB20180035)the Science Foundation of Institute of Plasma Physics, Chinese Academy of Sciences (No. DSJJ-2021-04)
文摘In recent EAST experiments,current profile broadening characterized by reduced internal inductance has been achieved by utilizing radio-frequency current drives(RFCD).In contrast to previous density scan experiments,which showed an outward shift of the current density profile of lower hybrid current drive(LHCD)in higher plasma density,the core electron temperature(T_(e)(0))is found to affect the LHCD current profile as well.According to equilibrium reconstruction,a significant increase in on-axis safety factor(q0)from 2.05 to 3.41 is observed by careful arrangement of RFCD.Simulations using ray-tracing code GENRAY and Fokker–Planck code CQL3D have been performed to thoroughly analyze the LHCD current profile,revealing the sensitivity of the LHCD current profile to T_(e)(0).The LHCD current density tends to accumulate in the plasma core with higher current drive efficiency benefiting from higher T_(e)(0).With a lower T_(e)(0),the LHCD current profile broadens due to off-axis deposition of power density.The sensitivity of the power deposition and current profile of LHCD to T_(e)(0)provides a promising way to effectively optimize current profile via control of the core electron temperature.
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 the National Magnetic Confinement Fusion Science Program of China(Grant Nos.2011GB102000,2012GB103000,2013GB106001,and2015GB102003)the National Natural Science Foundation of China(Grant Nos.11175206 and 11305211)+1 种基金the JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics(Grant No.11261140328)the Fundamental Research Funds for the Central Universities of China(Grant No.JZ2015HGBZ0472)
文摘The optimized synergy conditions between electron cyclotron current drive （ECCD） and lower hybrid current drive （LHCD） with normal parameters of the EAST tokamak are studied by using the C3PO/LUKE code based on the under- standing of the synergy mechanisms so as to obtain a higher synergistic current and provide theoretical reference for the synergistic effect in the EAST experiment. The dependences of the synergistic effect on the parameters of two waves （lower hybrid wave （LHW） and electron cyclotron wave （ECW））, including the radial position of the power deposition, the power value of the LH and EC waves, and the parallel refractive indices of the LHW （Nr） are oresented and discussed.
