低杂波注入对剥离气球模的作用

Influence of lower hybrid wave injection on peeling-ballooning modes

基于BOUT++代码研究了托卡马克高约束模等离子体中低杂波(LHW)注入对边缘台基区剥离气球模(P-B模)线性和非线性特性的影响.模拟中分别考虑了LHW驱动的常规主等离子体电流和刮削层螺旋电流丝(HCF)产生三维扰动磁场对P-B模的作用.线性结果表明,LHW驱动的主等离子体电流通过降低平衡的归一化压强梯度和磁剪切,使得线性环向模谱整体向高模数和低增长率的方向移动.非线性模拟表明,由于线性模谱的展宽,LHW驱动的主等离子体电流对P-B模不同模式具有整体的抑制效果,可以降低边缘局域模(ELM)造成的台基能量损失;LHW驱动HCF产生的三维扰动磁场可以通过增强不同模式之间的耦合,促进主模之外的其他模式增长来降低ELM造成的能量损失.研究发现,HCF产生的三维扰动磁场促进增长的P-B模式集中在较高模数,当P-B模的主导模式远离此模数区间,ELM能量损失降低更明显.研究结果有助于深入理解LHW控制ELM实验中的物理机制.

The high-confinement mode(H-mode)significantly enhances the energy and particle confinement in fusion plasma compared with the low-confinement mode(L-mode),and it is the basic operation scenario for ITER and CFETR.Edge localized mode(ELM)often appears in H-mode,helping to expel impurities to maintain a longer stable state.However,the particle burst and energy burst from ELM eruptions can severely damage the first wall of fusion device,so,it is necessary to control the ELM.Experiments on EAST tokamak and HL-2A tokamak have been conducted with ELM mitigation by lower hybrid wave(LHW),confirming the effect of LHW on ELMs,but the physical mechanism of ELM mitigation by LHW is still not fully understood.In this paper,the influences of LHW injection on the linear and nonlinear characteristics of peeling-ballooning mode(P-B mode)are investigated in the edge pedestal region of H-mode plasma in tokamak by using the BOUT++code.The simulations take into consideration both the conventional main plasma current driven by LHW and the three-dimensional perturbed magnetic field generated by the scrape-off layer helical current filament(HCF)on the P-B mode.The linear results show that the core plasma current driven by LHW moves the linear toroidal mode spectrum towards higher mode numbers and lower growth rates by reducing the normalized pressure gradient and magnetic shear of the equilibrium.Nonlinear simulations indicate that due to the broadening of the linear mode spectrum,the core current driven by LHW can reduce the pedestal energy loss caused by ELM through globally suppressing different toroidal modes of the P-B mode,and the three-dimensional perturbed magnetic field generated by LHW-driven HCF can reduce the energy loss caused by ELMs through promoting the growth of modes other than the main mode and enhancing the coupling between different modes.It is found in the study that the P-B mode promoted by the three-dimensional perturbed magnetic field generated by HCF has a mode number threshold,and when the dominant mode of the P-B mode is far from the mode number threshold driven by the three-dimensional perturbed magnetic field,the energy loss due to ELMs is more significantly reduced.These results contribute to a more in-depth understanding of the physical mechanism in ELM control experiment by LHW.