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
An internal transport barrier(ITB)can be formed on EAST in exploring high-parameter operation.Previous studies show that safety factor(q)profiles,Shafranov shift and magnetohydrodynamic behaviors could be helpful in I...An internal transport barrier(ITB)can be formed on EAST in exploring high-parameter operation.Previous studies show that safety factor(q)profiles,Shafranov shift and magnetohydrodynamic behaviors could be helpful in ITB formation by suppressing anomalous transport.Recently,electron density evolution with high resolution demonstrates that fishbone could be dominant in electron density ITB formation and sustainment.The power threshold is low in the fishbone condition and the electron density profile is determined by traits of fishbone.Simulation shows that the low-k ion mode is suppressed by fishbone.Direct measurement of turbulence in the inner region shows that the internal kink mode could sustain an electron temperature ITB by suppressing the trapped electron mode.The multi-scale interaction between the kink mode and turbulence by current could be key in sustaining high-electron-temperature long-pulse operation.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
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 the National Key R&D Program of China(No.2017YFE0301705)supported in part by the Key Program of Research and Development of Hefei Science Center,CAS(No.2019HSC-KPRD001)+1 种基金supported by National Natural Science Foundation of China(Nos.11975271 and 11675211)partly supported by the Collaborative Research Program of the Research Institute for Applied Mechanics,Kyushu University。
文摘An internal transport barrier(ITB)can be formed on EAST in exploring high-parameter operation.Previous studies show that safety factor(q)profiles,Shafranov shift and magnetohydrodynamic behaviors could be helpful in ITB formation by suppressing anomalous transport.Recently,electron density evolution with high resolution demonstrates that fishbone could be dominant in electron density ITB formation and sustainment.The power threshold is low in the fishbone condition and the electron density profile is determined by traits of fishbone.Simulation shows that the low-k ion mode is suppressed by fishbone.Direct measurement of turbulence in the inner region shows that the internal kink mode could sustain an electron temperature ITB by suppressing the trapped electron mode.The multi-scale interaction between the kink mode and turbulence by current could be key in sustaining high-electron-temperature long-pulse operation.
