Lower-hybrid drift instability （LHDI） in a Harris current sheet including a uniform background distribution is investigated in linear local kinetic theory. It is found that the introduction of a uniform background d...Lower-hybrid drift instability （LHDI） in a Harris current sheet including a uniform background distribution is investigated in linear local kinetic theory. It is found that the introduction of a uniform background distribution reduces the growth rate and real frequency of LHDI at all wavelengths. Some physical explanations about the effects of the background distribution are provided.展开更多
The LHCD antenna that will be used in LH-2A is the original one used in LH-1M, which will be modified. We measured the feature of the antenna, including the reflection of main waveguide, VSWR, the phase shift between ...The LHCD antenna that will be used in LH-2A is the original one used in LH-1M, which will be modified. We measured the feature of the antenna, including the reflection of main waveguide, VSWR, the phase shift between the adjacent sub-waveguides and so on. The paper describes the measured results and spectrum calculation based on the measured parameters. From the works we can assess our antennas correctly, which will be useful in LHCD experiment on HL-2A in the years to come.展开更多
In this study, by employing a local fluid theory for warm plasma containing negative ions, an obliquely propagating electromagnetic instability in the lower hybrid frequency range driven by cross-field currents or rel...In this study, by employing a local fluid theory for warm plasma containing negative ions, an obliquely propagating electromagnetic instability in the lower hybrid frequency range driven by cross-field currents or relative drifts between electrons and ions was investigated. It is found that the growth rate of the lower-hybrid-drift instability （LHDI） can be controlled by appropriate selection of the propagation direction, the wave number and the relative population of the negative ions.展开更多
For the effect of the collisional dissipation of fast electrons driven by the lower-hybrid waves, a predictive simulation is made for the HT-7 plasma. The simulation results show that the dissipation of fast electrons...For the effect of the collisional dissipation of fast electrons driven by the lower-hybrid waves, a predictive simulation is made for the HT-7 plasma. The simulation results show that the dissipation of fast electrons counteracts the effect of radial diffusion to some extent, thereby making the lower-hybrid driven current profile closer to the power deposition profile. So, in the case of an off-axis lower-hybrid wave power launching, the dissipation is helpful in maintaining a center-hollowed current profile in lower hybrid current drive （LHCD） plasmas, and thus possibly maintains the desired reversed magnetic shear.展开更多
Anonlocal two-fluid formulation has been constructed for describing lowerhybrid drift instabilities in current-sheet configuration with a finite guide magnetic field in the context of magnetic reconnection.As a benchm...Anonlocal two-fluid formulation has been constructed for describing lowerhybrid drift instabilities in current-sheet configuration with a finite guide magnetic field in the context of magnetic reconnection.As a benchmark and verification,a class of unstable modes with multiple eigenstates are found by numerical solutions with guide field turned off.It is found that the most unstable modes are the electrostatic,short-wavelength perturbations in the lower-hybrid frequency range,with wave functions localized at the edge of the current sheet where the density gradient reaches its maximum.It is also found that there exist electrostatic modes located near the center of the current sheet where the current density is maximum.These modes are lowfrequency,long-wavelength perturbations.Attempts will bemade to compare the current results with those from kinetic theory in the near future since the validity of the fluid theory ultimately needs to be checked with the more fundamental kinetic theory.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National Natural Science Foundation of China(Nos.10775134,40336052)
文摘Lower-hybrid drift instability （LHDI） in a Harris current sheet including a uniform background distribution is investigated in linear local kinetic theory. It is found that the introduction of a uniform background distribution reduces the growth rate and real frequency of LHDI at all wavelengths. Some physical explanations about the effects of the background distribution are provided.
文摘The LHCD antenna that will be used in LH-2A is the original one used in LH-1M, which will be modified. We measured the feature of the antenna, including the reflection of main waveguide, VSWR, the phase shift between the adjacent sub-waveguides and so on. The paper describes the measured results and spectrum calculation based on the measured parameters. From the works we can assess our antennas correctly, which will be useful in LHCD experiment on HL-2A in the years to come.
基金supported by the National Natural Science Foundation of China(Nos.40336052,10375063)
文摘In this study, by employing a local fluid theory for warm plasma containing negative ions, an obliquely propagating electromagnetic instability in the lower hybrid frequency range driven by cross-field currents or relative drifts between electrons and ions was investigated. It is found that the growth rate of the lower-hybrid-drift instability （LHDI） can be controlled by appropriate selection of the propagation direction, the wave number and the relative population of the negative ions.
基金supportcd by National Natural Science Foundation of China(No.10425526)
文摘For the effect of the collisional dissipation of fast electrons driven by the lower-hybrid waves, a predictive simulation is made for the HT-7 plasma. The simulation results show that the dissipation of fast electrons counteracts the effect of radial diffusion to some extent, thereby making the lower-hybrid driven current profile closer to the power deposition profile. So, in the case of an off-axis lower-hybrid wave power launching, the dissipation is helpful in maintaining a center-hollowed current profile in lower hybrid current drive （LHCD） plasmas, and thus possibly maintains the desired reversed magnetic shear.
基金The authors acknowledge fruitful discussions with Liu Chen,and Yu Lin.This work was supported by Department of Energy(DOE)Grants No.DE-FG02-07ER54916(UC Irvine)and DE-FG02-05ER54826(Auburn University)NSF Grant No.ATM-0449606Los Alamos National Laboratory Subcontract No.50219-001-07.
文摘Anonlocal two-fluid formulation has been constructed for describing lowerhybrid drift instabilities in current-sheet configuration with a finite guide magnetic field in the context of magnetic reconnection.As a benchmark and verification,a class of unstable modes with multiple eigenstates are found by numerical solutions with guide field turned off.It is found that the most unstable modes are the electrostatic,short-wavelength perturbations in the lower-hybrid frequency range,with wave functions localized at the edge of the current sheet where the density gradient reaches its maximum.It is also found that there exist electrostatic modes located near the center of the current sheet where the current density is maximum.These modes are lowfrequency,long-wavelength perturbations.Attempts will bemade to compare the current results with those from kinetic theory in the near future since the validity of the fluid theory ultimately needs to be checked with the more fundamental kinetic theory.
