A key physics issue for achieving steady-state high-performance plasmas on EAST tokamak is to decrease beam-ion losses to improve plasma confinement during neutral beam injections(NBIs).To decrease the beam losses,pre...A key physics issue for achieving steady-state high-performance plasmas on EAST tokamak is to decrease beam-ion losses to improve plasma confinement during neutral beam injections(NBIs).To decrease the beam losses,previous counter-I_(p)NBI injections are upgraded to co-I_(p)injections.Analysis shows that due to the reversed direction of drift across the flux surfaces caused by the pitch angle,the beam prompt loss fraction decreases from about 49%to 3%after the upgrade.Moreover,because of the change of entire beam path,beam shine-through(ST)loss fraction for counter-I_(p)tangential and counter-I_(p)perpendicular injections is reversed to co-I_(p)tangential and co-I_(p)perpendicular injections,respectively.Due to the change in the initial trapped-confined beam ion fraction caused by the peaked pitch profiles,the losses induced by toroidal ripple field are also reversed after the upgrade.To further improve the beam-ion confinement under the present NBI layout,the amplitudes of toroidal field are increased from 1.75 to 2.20 T.Result shows that,due to the smaller orbit width and peaked pitch angle profile,the beam prompt loss power is lower with higher toroidal field.Due to the synergy of higher initial trapped-confined beam ion fraction and narrower Goldston-White-Boozer(GWB)boundary,the loss induced by ripple diffusion is higher with higher toroidal field.The combined effect of beam ST loss,prompt loss and ripple loss,contributes to the increase in beam ion density.The decrease in beam loss power enhances beam heating efficiency,especially the fraction of beam heating ions.Finally,comparison between simulation and measurement by^(235)U fission chamber(FC)indicates that the increase in neutron rate is mainly contributed by improvement of beam-ion confinement.This study can provide potential support for beam operation and high-T_(i)experiment on EAST tokamak.展开更多
2D fast-ion velocity-space distributions have been reconstructed from two-view fast-ion D-alpha(FIDA)measurements on experimental advanced superconducting tokamak(EAST).To make up for the sparse data and incomplete ve...2D fast-ion velocity-space distributions have been reconstructed from two-view fast-ion D-alpha(FIDA)measurements on experimental advanced superconducting tokamak(EAST).To make up for the sparse data and incomplete velocity-space coverage with the dual-view,we use nonnegativity and null-measurements as prior information to reconstruct the velocity distribution in experiments with co-and counter-current neutral beam injection.An improved reconstructed fast-ion distribution is achieved by combining the existing O-and B-port FIDA measurements with the proposed A-port FIDA view.To further improve the reliability of FIDA-based reconstructions on EAST,based on real multi-view FIDA measurements on EAST in the near future,various bases will be studied further.展开更多
基金supported by the National Key R&D Program of China(No.2019YFE03020004)National Natural Science Foundation of China(Nos.12175272 and 12347186)+3 种基金Anhui Provincial Natural Science Foundation(No.2008085J04)Anhui Provincial Key R&D Program(No.202104b11020003)Collaborative Innovation Program of Hefei Science Center,CAS(No.YZJJ2023QN17)State Key Laboratory of Advanced Electromagnetic Technology(No.AET 2024KF010)。
文摘A key physics issue for achieving steady-state high-performance plasmas on EAST tokamak is to decrease beam-ion losses to improve plasma confinement during neutral beam injections(NBIs).To decrease the beam losses,previous counter-I_(p)NBI injections are upgraded to co-I_(p)injections.Analysis shows that due to the reversed direction of drift across the flux surfaces caused by the pitch angle,the beam prompt loss fraction decreases from about 49%to 3%after the upgrade.Moreover,because of the change of entire beam path,beam shine-through(ST)loss fraction for counter-I_(p)tangential and counter-I_(p)perpendicular injections is reversed to co-I_(p)tangential and co-I_(p)perpendicular injections,respectively.Due to the change in the initial trapped-confined beam ion fraction caused by the peaked pitch profiles,the losses induced by toroidal ripple field are also reversed after the upgrade.To further improve the beam-ion confinement under the present NBI layout,the amplitudes of toroidal field are increased from 1.75 to 2.20 T.Result shows that,due to the smaller orbit width and peaked pitch angle profile,the beam prompt loss power is lower with higher toroidal field.Due to the synergy of higher initial trapped-confined beam ion fraction and narrower Goldston-White-Boozer(GWB)boundary,the loss induced by ripple diffusion is higher with higher toroidal field.The combined effect of beam ST loss,prompt loss and ripple loss,contributes to the increase in beam ion density.The decrease in beam loss power enhances beam heating efficiency,especially the fraction of beam heating ions.Finally,comparison between simulation and measurement by^(235)U fission chamber(FC)indicates that the increase in neutron rate is mainly contributed by improvement of beam-ion confinement.This study can provide potential support for beam operation and high-T_(i)experiment on EAST tokamak.
基金supported by National Natural Science Foundation of China(No.11975276)Anhui Provincial Natural Science Foundation(No.2008085J04)+3 种基金Anhui Provincial Key R&D Programmes(No.202104b11020003)the National Key Research and Development Program of China(No.2019YFE03020004)the Excellence Program of Hefei Science Center CAS(No.2021HSC-UE015)。
文摘2D fast-ion velocity-space distributions have been reconstructed from two-view fast-ion D-alpha(FIDA)measurements on experimental advanced superconducting tokamak(EAST).To make up for the sparse data and incomplete velocity-space coverage with the dual-view,we use nonnegativity and null-measurements as prior information to reconstruct the velocity distribution in experiments with co-and counter-current neutral beam injection.An improved reconstructed fast-ion distribution is achieved by combining the existing O-and B-port FIDA measurements with the proposed A-port FIDA view.To further improve the reliability of FIDA-based reconstructions on EAST,based on real multi-view FIDA measurements on EAST in the near future,various bases will be studied further.
