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
We investigate the effects of kinetic ions on double-tearing modes(DTMs) using the gyrokinetic particle-in-cell simulation code GEM with a gyrokinetic ion/fluid electron hybrid model. It is found that the ion kinetic ...We investigate the effects of kinetic ions on double-tearing modes(DTMs) using the gyrokinetic particle-in-cell simulation code GEM with a gyrokinetic ion/fluid electron hybrid model. It is found that the ion kinetic effects can decrease the growth rate of the DTMs. This effect is more significant for stronger coupling of DTMs with smaller distance between the rational surfaces. Kinetic ions can also enhance the coupling effect between the two rational surfaces. Energy transfer analyses between particles and wave fields show that the stabilizing effect of kinetic ions comes mainly from the perpendicular magnetic drift of ions in the coupling region and around the outer rational surface.展开更多
The lower hybrid current drive is a potential candidate for sustaining plasma current in tokamak steady-state oper-ations,which could be used in China Fusion Engineering Test Reactor(CFETR)with input power up to a few...The lower hybrid current drive is a potential candidate for sustaining plasma current in tokamak steady-state oper-ations,which could be used in China Fusion Engineering Test Reactor(CFETR)with input power up to a few tens of megawatts.Such high input power could trigger the well-known parametric instabilities(PIs)at the plasma edge affect-ing the propagation and absorption of the lower hybrid pump waves.By analytically solving the nonlinear dispersion relation describing PIs,an explicit expression of the PI growth rate is obtained and analyzed in detail.It is found that pressure is the key parameter determining the PI characteristics.Ion sound quasi-mode is the dominant decay channel in the low-pressure regime,while the ion cyclotron quasi-mode(ICQM),as well as its harmonics,becomes dominant in the intermediate regime.In the high-pressure regime,only one mixed channel is found,which is related to Landau damping by free-streaming ions.Analytical expressions of growth rates of these decay channels are also obtained to show the parameter dependence at different pressure limits.The above analytical results are used to estimate the PIs on a typical profile of CFETR,and verified by corresponding numerical calculations.ICQM is found to be the strongest decay channel with a considerable growth rate for CFETR.展开更多
The effect of the wave accessibility condition on the lower hybrid cm＇rent drive in the experimental advanced superconductor Tokamak （EAST） plasma with H-mode operation is studied. Based on a simplified model, a mo...The effect of the wave accessibility condition on the lower hybrid cm＇rent drive in the experimental advanced superconductor Tokamak （EAST） plasma with H-mode operation is studied. Based on a simplified model, a mode conversion layer of the lower hybrid wave between the fast wave branch and the slow wave branch is proved to exist in the plasma periphery for typical EAST H-mode parameters. Under the framework of the lower hybrid wave simulation code （LSC）, the wave ray trajectory and the associated current drive are calculated numerically. The results show that the wave accessibility condition plays an important role on the lower hybrid current drive in EAST plasma. For wave rays with parallel refractive index n｜｜= 2.1 or n｜｜ = 2.5 launched from the outside midplane, the wave rays may penetrate the core plasma due to the toroida] geometry effect, while numerous reflections of the wave ray trajectories in the plasma periphery occur. However, low current drive efficiency is obtained. Meanwhile, the wave accessibility condition is improved if a higher confined magnetic field is applied. The simulation results show that for plasma parameters under present EAST H-mode operation, a significant lower hybrid wave current drive could be obtained for the wave spectrum with peak value n｜｜ = 2.1 if a toroidal magnetic field BT =2.5 T is applied.展开更多
The equilibrium reconstruction is important to study the tokamak plasma physical processes.To analyze the contribution of fast ions to the equilibrium,the kinetic equilibria at two time-slices in a typical H-mode disc...The equilibrium reconstruction is important to study the tokamak plasma physical processes.To analyze the contribution of fast ions to the equilibrium,the kinetic equilibria at two time-slices in a typical H-mode discharge with different auxiliary heatings are reconstructed by using magnetic diagnostics,kinetic diagnostics and TRANSP code.It is found that the fast-ion pressure might be up to one-third of the plasma pressure and the contribution is mainly in the core plasma due to the neutral beam injection power is primarily deposited in the core region.The fast-ion current contributes mainly in the core region while contributes little to the pedestal current.A steep pressure gradient in the pedestal is observed which gives rise to a strong edge current.It is proved that the fast ion effects cannot be ignored and should be considered in the future study of EAST.展开更多
Ion cyclotron resonance heating(ICRH),which can produce fast ions,is an important auxiliary heating method at EAST.To analyze the effect of ICRH-induced fast ions on the plasma pressure at EAST,simulations are perform...Ion cyclotron resonance heating(ICRH),which can produce fast ions,is an important auxiliary heating method at EAST.To analyze the effect of ICRH-induced fast ions on the plasma pressure at EAST,simulations are performed using TRANSP and TORIC codes.It is found that the ICRF-induced fast ion pressure cannot be negligible when the ICRF power is sufficiently high.The magnitude of the total ion pressure can be raised up to 60%of the total pressure as the input power rises above 3 MW.The pressure profile is also significantly modified when the resonant layer is changed.It is shown that by changing the wave frequency and antenna position,the total ion pressure profile can be broadened,which might provide an option for profile control at EAST.展开更多
In recent experiments on EAST,the electron temperature at the center can be raised to 9.7 ke V by injecting electron cyclotron(EC)and lower hybrid(LH)waves simultaneously.With such strong core electron heating,the rel...In recent experiments on EAST,the electron temperature at the center can be raised to 9.7 ke V by injecting electron cyclotron(EC)and lower hybrid(LH)waves simultaneously.With such strong core electron heating,the relativistic effect could play an important role in the interactions between the plasma and waves.In order to explore the relativistic effect on synergy between the EC and LH waves on EAST,ray-tracing/Fokker-Planck simulations are conducted to investigate electron heating for a typical discharge with a center electron temperature of 9.7 ke V.It is found that the relativistic effect can cause the EC wave to deposit its power deeper in the plasma core,where the synergy between the EC and LH waves occurs and enhances the absorption of the LH waves.As a result,a high center electron temperature can be achieved.展开更多
Using lower hybrid current drive (LHCD), improved confinement has been achieved on HT-6B tokamak. The particle confinement time was increased by 2- 6 times and the plasma-stored energy was doubled. Only obtainable in ...Using lower hybrid current drive (LHCD), improved confinement has been achieved on HT-6B tokamak. The particle confinement time was increased by 2- 6 times and the plasma-stored energy was doubled. Only obtainable in an electron density window of 0.3×1013- 1.5× 1013cm-3, the improvement was accompanied by suppression of the fast fluctuations and increment of the gradient of edge electron temperature with very low power threshold. An analysis shows that the improvement might be possibly caused by certain energetic electrons produced by LHCD.展开更多
The classical prompt loss of fast ions produced by minority ion cyclotron resonance heating(ICRH)is studied by a guiding center orbit following code in the Experimental Advanced Superconducting Tokamak(EAST).It is fou...The classical prompt loss of fast ions produced by minority ion cyclotron resonance heating(ICRH)is studied by a guiding center orbit following code in the Experimental Advanced Superconducting Tokamak(EAST).It is found that the loss of fast ions produced by ICRH mainly appears in both ends of the resonance layer,while the loss of fast ions in the middle resonance layer is very small.The dominant fast loss comes from trapped ions,rather than from passing ions.Controlling the location of resonance layer at the plasma core may be more beneficial to the EAST tokamak ICRH.In addition,the loss distribution of fast ions is studied.The results show that the fast ions are mainly lost near the midplane in the poloidal direction,but almost uniformly in the toroidal direction.Moreover,we investigate the dependence of fast ion loss on the ICRH power.The simulation results show that the loss fraction of fast ions in both ends of the resonance region increases with the ion cyclotron range of frequencies(ICRF)power,but barely affects the loss of fast ions in the middle region.展开更多
迄今为止,用低杂波驱动出等离子体电流,仍是有希望维持托卡马克稳态运行的途径之一.因此,研究低杂波在等离子体中的物理过程,仍是近年这方面理论和实验所关注的焦点.按照目前理论上的观点,低杂波在被等离子体完全吸收之前,通常要在其截...迄今为止,用低杂波驱动出等离子体电流,仍是有希望维持托卡马克稳态运行的途径之一.因此,研究低杂波在等离子体中的物理过程,仍是近年这方面理论和实验所关注的焦点.按照目前理论上的观点,低杂波在被等离子体完全吸收之前,通常要在其截止层和等离子体中心之间的区域往返传播多次,由于磁场剪切和环效应,低杂波的平行折射率 n将有较大的上移.n上移的大小,一般取决于低杂波环向模数 m 的变化,而波在传播过程中各物理量的变化是由一个常微分方程组——射线轨迹方程来描述的,因此,可以预想,初值和边界参数对方程组解的性质影响很大.下面我们将证明,由于托卡马克限制器的存在。展开更多
One-dimensional particle simulations have been conducted to study the interaction between a radio-frequency electrostatic wave and electrons with bouncing motion.It is shown that bounce resonance heating can occur at ...One-dimensional particle simulations have been conducted to study the interaction between a radio-frequency electrostatic wave and electrons with bouncing motion.It is shown that bounce resonance heating can occur at the first few harmonics of the bounce frequency(nω_(b),n=1,2,3,...).In the parameter regimes in which bounce resonance overlaps with Landau resonance,the higher harmonic bounce resonance may accelerate electrons at the velocity much lower than the wave phase velocity to Landau resonance region,enhancing Landau damping of the wave.Meanwhile,Landau resonance can increase the number of electrons in the lower harmonic bounce resonance region.Thus electrons can be efficiently heated.The result might be applicable for collisionless electron heating in low-temperature plasma discharges.展开更多
During edge localized modes(ELMs), the sheath evolution in front of the Experimental Advanced Superconducting Tokamak(EAST) upper divertor is studied to estimate the sputtered tungsten(W) atoms from the divertor targe...During edge localized modes(ELMs), the sheath evolution in front of the Experimental Advanced Superconducting Tokamak(EAST) upper divertor is studied to estimate the sputtered tungsten(W) atoms from the divertor target. A large potential drop across the sheath is formed during ELMs by compared with inter-ELMs, and the maximum of sheath potential drop can exceed one thousand of e V in current EAST operation. Due to the enhancement of the sheath potential drop during ELMs, the W physical sputtering yield from the deuterium(D) ions and the impurity ions on the upper divertor target is found to be significant. It is established that the sputtered W yield during ELMs is at least higher by an order of magnitude than inter-ELMs, and D ions and carbon(C) ions are the main ions governing the W production for the current H-mode with ELMs discharges. With increase in the pedestal electron temperature, the maximum of the D and C ion impact energy during ELMs shows a nearly linear increase, and the D ions have sufficient impact energy to cause the strong W physical sputtering. As a consequence, the D ions may dominate the sputtered W flux from the divertor target when the C concentration is controlled less than one percent for the higher heating power H-mode with ELM discharges in near future.展开更多
The sheaths of a plasma containing two species of positive ion generated in a low pressure discharge （- mTorr） are studied using a fluid model. It is shown analytically that for the weakly collisional presheath, as ...The sheaths of a plasma containing two species of positive ion generated in a low pressure discharge （- mTorr） are studied using a fluid model. It is shown analytically that for the weakly collisional presheath, as long as the ion-ion streaming instability is absent, each ion species enters the sheath satisfying each individual Bohm criterion. The fluid equations of electrons and ions, including the time derivative terms, are solved numerically to follow the temporal evolution of the plasma and sheath. Our numerical results show that in the parameter range explored, the ion-ion streaming instability is not observed, and each ion species has its own Bohm criterion independent of the relative concentrations of the two ion species. In addition, the RF sheath is studied numerically and the similar conclusion is drawn.展开更多
In tokamak plasma fueling, supersonic molecule beam injection(SMBI) with a higher fueling efficiency and a deeper penetration depth than the traditional gas puffing method has been developed and widely applied to many...In tokamak plasma fueling, supersonic molecule beam injection(SMBI) with a higher fueling efficiency and a deeper penetration depth than the traditional gas puffing method has been developed and widely applied to many tokamak devices.It is crucial to study the transport dynamics of SMBI to improve its fueling efficiency, especially in the high confinement regime. A new one-dimensional(1D) code of TPSMBI has also been developed recently based on a six-field SMBI model in cylindrical coordinate. It couples plasma density and heat radial transport equations together with neutral density transport equations for both molecules and atoms and momentum radial transport equations for molecules. The dominant particle collisional interactions between plasmas and neutrals, such as molecule dissociation, atom ionization and charge-exchange effects, are included in the model. The code is verified to be correct with analytical solutions and also benchmarked well with the trans-neut module of BOUT++ code. Time-dependent radial transport dynamics and mean profile evolution are studied during SMBI with the TPSMBI code in both slab and cylindrical coordinates. Along the SMBI path, plasma density increases due to particle fuelling, while plasma temperature decreases due to heat cooling. Being different from slab coordinate, the curvature effect leads to larger front densities of molecule and atom during SMBI in cylindrical coordinate simulation.展开更多
This research applies experimental measurements and NUBEAM,ONETWO and TRANSP modules to investigate the shine-through(ST)loss ratio and beam heating percentage of neutral beam injection on EAST.Measurements and simula...This research applies experimental measurements and NUBEAM,ONETWO and TRANSP modules to investigate the shine-through(ST)loss ratio and beam heating percentage of neutral beam injection on EAST.Measurements and simulations confirm that the ST loss ratio increases linearly with beam energy,and decreases exponentially with plasma density.Moreover,using the multi-step fitting method,we present analytical quantitative expressions of ST loss ratio and beam heating percentage,which are valuable for the high parameter long-pulse experiments of EAST.展开更多
In the 2016 EAST experimental campaign,a steady-state long-pulse H-mode discharge with an ITER-like tungsten divertor lasting longer than one minute has been obtained using only RF heating and current drive,through an...In the 2016 EAST experimental campaign,a steady-state long-pulse H-mode discharge with an ITER-like tungsten divertor lasting longer than one minute has been obtained using only RF heating and current drive,through an integrated control of the wall conditioning,plasma configuration,divertor heat flux,particle exhaust,impurity management,and effective coupling of multiple RF heating and current drive sources at high injected power.The plasma current（Ip - 0.45 MA） was fully-noninductively driven（Vloop 〈 0.0 V） by a combination of-2.5 MW LHW,-0.4 MW ECH and -0.8 MW ICRF.This result demonstrates the progress of physics and technology studies on EAST,and will benefit the physics basis for steady state operation of ITER and CFETR.展开更多
Particle-in-cell （PIC） simulation method has been proved to be a good candidate to study the interactions between plasmas and radio-frequency waves. However, for waves in the lower hybrid range of frequencies, a ful...Particle-in-cell （PIC） simulation method has been proved to be a good candidate to study the interactions between plasmas and radio-frequency waves. However, for waves in the lower hybrid range of frequencies, a full PIC simulation is not efficient due to its high computational cost. In this work, a gyro-kinetic electron and fully-kinetic ion （GeFi） particle simulation model is applied to study the propagations and mode conversion processes of lower hybrid waves （LHWs） in plasmas. With this method, the computational efficiency of LHW simulations is greatly increased by using a larger grid size and time step. The simulation results in the linear regime are validated by comparison with the linear theory.展开更多
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 MCF Energy R&D Program of China (Grant No. 2019YFE03060001)the National Key R&D Program of China (Grant No. 2017YFE0300406)+1 种基金the National Natural Science Foundation of China (Grant Nos. 11975272 and 11905257)supported by the SciDAC Center Advanced Tokamak Modeling Environment (AToM) (Grant No. DE-SC0017992)。
文摘We investigate the effects of kinetic ions on double-tearing modes(DTMs) using the gyrokinetic particle-in-cell simulation code GEM with a gyrokinetic ion/fluid electron hybrid model. It is found that the ion kinetic effects can decrease the growth rate of the DTMs. This effect is more significant for stronger coupling of DTMs with smaller distance between the rational surfaces. Kinetic ions can also enhance the coupling effect between the two rational surfaces. Energy transfer analyses between particles and wave fields show that the stabilizing effect of kinetic ions comes mainly from the perpendicular magnetic drift of ions in the coupling region and around the outer rational surface.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFE0300406 and 2019YFE00308050)the National Natural Science Foundation of China(Grant Nos.11975272,12175274,12005258,and 11705236)。
文摘The lower hybrid current drive is a potential candidate for sustaining plasma current in tokamak steady-state oper-ations,which could be used in China Fusion Engineering Test Reactor(CFETR)with input power up to a few tens of megawatts.Such high input power could trigger the well-known parametric instabilities(PIs)at the plasma edge affect-ing the propagation and absorption of the lower hybrid pump waves.By analytically solving the nonlinear dispersion relation describing PIs,an explicit expression of the PI growth rate is obtained and analyzed in detail.It is found that pressure is the key parameter determining the PI characteristics.Ion sound quasi-mode is the dominant decay channel in the low-pressure regime,while the ion cyclotron quasi-mode(ICQM),as well as its harmonics,becomes dominant in the intermediate regime.In the high-pressure regime,only one mixed channel is found,which is related to Landau damping by free-streaming ions.Analytical expressions of growth rates of these decay channels are also obtained to show the parameter dependence at different pressure limits.The above analytical results are used to estimate the PIs on a typical profile of CFETR,and verified by corresponding numerical calculations.ICQM is found to be the strongest decay channel with a considerable growth rate for CFETR.
基金Supported by the National Natural Science Foundation of China under Grant No 11347002the National Magnetic Confinement Fusion Science Program of China under Grant No 2013GB111000+2 种基金the Outstanding Youth Fund of Hunan Province Education Department of China under Grant No 12B107the JSPS-NRF-NSFC A3 Foresight Program in the field of Plasma Physics under Grant No 11261140328the National Research Foundation 2012K2A2A6000443
文摘The effect of the wave accessibility condition on the lower hybrid cm＇rent drive in the experimental advanced superconductor Tokamak （EAST） plasma with H-mode operation is studied. Based on a simplified model, a mode conversion layer of the lower hybrid wave between the fast wave branch and the slow wave branch is proved to exist in the plasma periphery for typical EAST H-mode parameters. Under the framework of the lower hybrid wave simulation code （LSC）, the wave ray trajectory and the associated current drive are calculated numerically. The results show that the wave accessibility condition plays an important role on the lower hybrid current drive in EAST plasma. For wave rays with parallel refractive index n｜｜= 2.1 or n｜｜ = 2.5 launched from the outside midplane, the wave rays may penetrate the core plasma due to the toroida] geometry effect, while numerous reflections of the wave ray trajectories in the plasma periphery occur. However, low current drive efficiency is obtained. Meanwhile, the wave accessibility condition is improved if a higher confined magnetic field is applied. The simulation results show that for plasma parameters under present EAST H-mode operation, a significant lower hybrid wave current drive could be obtained for the wave spectrum with peak value n｜｜ = 2.1 if a toroidal magnetic field BT =2.5 T is applied.
基金supported by National Key R&D Program of China under Grant No.2017YFE0300400National Natural Science Foundation of China under Grant Nos.11475220,11405218,11575248+1 种基金the National Magnetic Confinement Fusion Science Program of China under Contracts No.2014GB106001sponsored in part by Youth Innovation Promotion Association Chinese Academy of Sciences (Grant No.2016384)
文摘The equilibrium reconstruction is important to study the tokamak plasma physical processes.To analyze the contribution of fast ions to the equilibrium,the kinetic equilibria at two time-slices in a typical H-mode discharge with different auxiliary heatings are reconstructed by using magnetic diagnostics,kinetic diagnostics and TRANSP code.It is found that the fast-ion pressure might be up to one-third of the plasma pressure and the contribution is mainly in the core plasma due to the neutral beam injection power is primarily deposited in the core region.The fast-ion current contributes mainly in the core region while contributes little to the pedestal current.A steep pressure gradient in the pedestal is observed which gives rise to a strong edge current.It is proved that the fast ion effects cannot be ignored and should be considered in the future study of EAST.
基金The authors would like to thank Doctors Guosheng Xu,Damao Yao,and Yongliang Li for helpful discussionsThis work was supported by the National Key R&D Program of China(Nos.2017YFE0300400,2017YFE0300406)National Natural Science Foundation of China(Nos.11575239,11775265).
文摘Ion cyclotron resonance heating(ICRH),which can produce fast ions,is an important auxiliary heating method at EAST.To analyze the effect of ICRH-induced fast ions on the plasma pressure at EAST,simulations are performed using TRANSP and TORIC codes.It is found that the ICRF-induced fast ion pressure cannot be negligible when the ICRF power is sufficiently high.The magnitude of the total ion pressure can be raised up to 60%of the total pressure as the input power rises above 3 MW.The pressure profile is also significantly modified when the resonant layer is changed.It is shown that by changing the wave frequency and antenna position,the total ion pressure profile can be broadened,which might provide an option for profile control at EAST.
基金supported by the National Key R&D Program of China (No.2017YFE0300406)National Natural Science Foundation of China (Nos. 11 975 272, 12 075 276, 11 375 234, 11 805 133 and 12 005 258).
文摘In recent experiments on EAST,the electron temperature at the center can be raised to 9.7 ke V by injecting electron cyclotron(EC)and lower hybrid(LH)waves simultaneously.With such strong core electron heating,the relativistic effect could play an important role in the interactions between the plasma and waves.In order to explore the relativistic effect on synergy between the EC and LH waves on EAST,ray-tracing/Fokker-Planck simulations are conducted to investigate electron heating for a typical discharge with a center electron temperature of 9.7 ke V.It is found that the relativistic effect can cause the EC wave to deposit its power deeper in the plasma core,where the synergy between the EC and LH waves occurs and enhances the absorption of the LH waves.As a result,a high center electron temperature can be achieved.
文摘Using lower hybrid current drive (LHCD), improved confinement has been achieved on HT-6B tokamak. The particle confinement time was increased by 2- 6 times and the plasma-stored energy was doubled. Only obtainable in an electron density window of 0.3×1013- 1.5× 1013cm-3, the improvement was accompanied by suppression of the fast fluctuations and increment of the gradient of edge electron temperature with very low power threshold. An analysis shows that the improvement might be possibly caused by certain energetic electrons produced by LHCD.
基金supported by National Natural Science Foundation of China (No. 11805239)the Natural Science Foundation of Hunan Province (No. 2019JJ50011)
文摘The classical prompt loss of fast ions produced by minority ion cyclotron resonance heating(ICRH)is studied by a guiding center orbit following code in the Experimental Advanced Superconducting Tokamak(EAST).It is found that the loss of fast ions produced by ICRH mainly appears in both ends of the resonance layer,while the loss of fast ions in the middle resonance layer is very small.The dominant fast loss comes from trapped ions,rather than from passing ions.Controlling the location of resonance layer at the plasma core may be more beneficial to the EAST tokamak ICRH.In addition,the loss distribution of fast ions is studied.The results show that the fast ions are mainly lost near the midplane in the poloidal direction,but almost uniformly in the toroidal direction.Moreover,we investigate the dependence of fast ion loss on the ICRH power.The simulation results show that the loss fraction of fast ions in both ends of the resonance region increases with the ion cyclotron range of frequencies(ICRF)power,but barely affects the loss of fast ions in the middle region.
文摘迄今为止,用低杂波驱动出等离子体电流,仍是有希望维持托卡马克稳态运行的途径之一.因此,研究低杂波在等离子体中的物理过程,仍是近年这方面理论和实验所关注的焦点.按照目前理论上的观点,低杂波在被等离子体完全吸收之前,通常要在其截止层和等离子体中心之间的区域往返传播多次,由于磁场剪切和环效应,低杂波的平行折射率 n将有较大的上移.n上移的大小,一般取决于低杂波环向模数 m 的变化,而波在传播过程中各物理量的变化是由一个常微分方程组——射线轨迹方程来描述的,因此,可以预想,初值和边界参数对方程组解的性质影响很大.下面我们将证明,由于托卡马克限制器的存在。
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFE0300406)the National Natural Science Foundation of China(Grant Nos.11975272,12075276,11805133,11705236,and 11375234)。
文摘One-dimensional particle simulations have been conducted to study the interaction between a radio-frequency electrostatic wave and electrons with bouncing motion.It is shown that bounce resonance heating can occur at the first few harmonics of the bounce frequency(nω_(b),n=1,2,3,...).In the parameter regimes in which bounce resonance overlaps with Landau resonance,the higher harmonic bounce resonance may accelerate electrons at the velocity much lower than the wave phase velocity to Landau resonance region,enhancing Landau damping of the wave.Meanwhile,Landau resonance can increase the number of electrons in the lower harmonic bounce resonance region.Thus electrons can be efficiently heated.The result might be applicable for collisionless electron heating in low-temperature plasma discharges.
基金Project supported by the National Key R&D Program of China(Grant Nos.2017YFE0300400 and 2017YFE0301300)the National Natural Science Foundation of China(Grant Nos.11475223 and 11775257)+1 种基金the National Magnetic Confinement Fusion Science Program of China(Grant No.2015GB101003)partly supported by AHNSF of China(Grant No.1808085J07)
文摘During edge localized modes(ELMs), the sheath evolution in front of the Experimental Advanced Superconducting Tokamak(EAST) upper divertor is studied to estimate the sputtered tungsten(W) atoms from the divertor target. A large potential drop across the sheath is formed during ELMs by compared with inter-ELMs, and the maximum of sheath potential drop can exceed one thousand of e V in current EAST operation. Due to the enhancement of the sheath potential drop during ELMs, the W physical sputtering yield from the deuterium(D) ions and the impurity ions on the upper divertor target is found to be significant. It is established that the sputtered W yield during ELMs is at least higher by an order of magnitude than inter-ELMs, and D ions and carbon(C) ions are the main ions governing the W production for the current H-mode with ELMs discharges. With increase in the pedestal electron temperature, the maximum of the D and C ion impact energy during ELMs shows a nearly linear increase, and the D ions have sufficient impact energy to cause the strong W physical sputtering. As a consequence, the D ions may dominate the sputtered W flux from the divertor target when the C concentration is controlled less than one percent for the higher heating power H-mode with ELM discharges in near future.
文摘The sheaths of a plasma containing two species of positive ion generated in a low pressure discharge （- mTorr） are studied using a fluid model. It is shown analytically that for the weakly collisional presheath, as long as the ion-ion streaming instability is absent, each ion species enters the sheath satisfying each individual Bohm criterion. The fluid equations of electrons and ions, including the time derivative terms, are solved numerically to follow the temporal evolution of the plasma and sheath. Our numerical results show that in the parameter range explored, the ion-ion streaming instability is not observed, and each ion species has its own Bohm criterion independent of the relative concentrations of the two ion species. In addition, the RF sheath is studied numerically and the similar conclusion is drawn.
基金supported by the National Natural Science Foundation of China(Grant Nos.11575055,11375053,and 11475219)the National Magnetic Confinement Fusion Science Program of China(Grant Nos.2013GB111005,2014GB108004,and 2015GB110001)
文摘In tokamak plasma fueling, supersonic molecule beam injection(SMBI) with a higher fueling efficiency and a deeper penetration depth than the traditional gas puffing method has been developed and widely applied to many tokamak devices.It is crucial to study the transport dynamics of SMBI to improve its fueling efficiency, especially in the high confinement regime. A new one-dimensional(1D) code of TPSMBI has also been developed recently based on a six-field SMBI model in cylindrical coordinate. It couples plasma density and heat radial transport equations together with neutral density transport equations for both molecules and atoms and momentum radial transport equations for molecules. The dominant particle collisional interactions between plasmas and neutrals, such as molecule dissociation, atom ionization and charge-exchange effects, are included in the model. The code is verified to be correct with analytical solutions and also benchmarked well with the trans-neut module of BOUT++ code. Time-dependent radial transport dynamics and mean profile evolution are studied during SMBI with the TPSMBI code in both slab and cylindrical coordinates. Along the SMBI path, plasma density increases due to particle fuelling, while plasma temperature decreases due to heat cooling. Being different from slab coordinate, the curvature effect leads to larger front densities of molecule and atom during SMBI in cylindrical coordinate simulation.
基金Supported by the Collaborative Innovation Program of Hefei Science Center,CAS (Grant No.2019HSC-CIP015)the National Natural Science Foundation of China (Grant Nos.11875290,1170529,11875253,and 11975276)+2 种基金the Fundamental Research Funds for the Central Universities (Grant No.WK3420000004)the Anhui Provincial Natural Science Foundation (Grant No.2008085J04)the National Key Research and Development Program of China (Grant No.2019YFE03020004)。
文摘This research applies experimental measurements and NUBEAM,ONETWO and TRANSP modules to investigate the shine-through(ST)loss ratio and beam heating percentage of neutral beam injection on EAST.Measurements and simulations confirm that the ST loss ratio increases linearly with beam energy,and decreases exponentially with plasma density.Moreover,using the multi-step fitting method,we present analytical quantitative expressions of ST loss ratio and beam heating percentage,which are valuable for the high parameter long-pulse experiments of EAST.
基金supported by the National Magnetic Conlinement Fusion Science Program of China(Nos.2015GB102000 and 2015GB103000)
文摘In the 2016 EAST experimental campaign,a steady-state long-pulse H-mode discharge with an ITER-like tungsten divertor lasting longer than one minute has been obtained using only RF heating and current drive,through an integrated control of the wall conditioning,plasma configuration,divertor heat flux,particle exhaust,impurity management,and effective coupling of multiple RF heating and current drive sources at high injected power.The plasma current（Ip - 0.45 MA） was fully-noninductively driven（Vloop 〈 0.0 V） by a combination of-2.5 MW LHW,-0.4 MW ECH and -0.8 MW ICRF.This result demonstrates the progress of physics and technology studies on EAST,and will benefit the physics basis for steady state operation of ITER and CFETR.
基金supported by Science Foundation of Institute of Plasma Physics Chinese Academy of Sciences(No.Y35ETY1304)the JSPSNRF-NSFC A3 Foresight Program in the Field of Plasma Physics(No.11261140328)+1 种基金National ITER Plans Program of China(No.2013GB111002)National Natural Science Foundation of China(No.11105178)
文摘Particle-in-cell （PIC） simulation method has been proved to be a good candidate to study the interactions between plasmas and radio-frequency waves. However, for waves in the lower hybrid range of frequencies, a full PIC simulation is not efficient due to its high computational cost. In this work, a gyro-kinetic electron and fully-kinetic ion （GeFi） particle simulation model is applied to study the propagations and mode conversion processes of lower hybrid waves （LHWs） in plasmas. With this method, the computational efficiency of LHW simulations is greatly increased by using a larger grid size and time step. The simulation results in the linear regime are validated by comparison with the linear theory.
