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A large number of energetic particles (EPs) are generated in the heating process to obtain the high temperature plasma for fusion research. These EPs can resonantly excite various magnetohydrodynamic (MHD) instabilities, including the Alfvén eigenmodes (AEs) and the energetic particle modes (EPMs). The excitation of such MHD instabilities can lead to significant EP losses, which not only degrades the plasma confinement and heating efficiency, but also results in excessive heat loads and damage to plasma-facing components. In this work, the influences of key plasma parameters on the excitation and damping effect of EP-driven MHD instabilities in Heliotron J device are investigated for better understanding of the excitation and transport mechanism of EPs driven MHD in specific device, which is meaningful for achieving stable plasma operation in future fusion devices with different heating methods. In this work, the typical EPs driven MHD instabilities are observed using various diagnostic methods, such as magnetic probes, beam emission spectroscopy (BES), electron cyclotron resonance (ECE) radiometers, and interferometers. Combined with the simulation results from STELLGAP and FAR3D programs, the modulus, radial distribution, and spectral characteristics of different instabilities are analyzed in depth, revealing the evolutions of AEs and EPMs in the Heliotron J device under typical heating conditions. This study quantitatively reveals the driving and suppressing mechanisms of EP-driven instabilities by the electron density (ne), the electron temperature (Te), and the energetic/thermal particle specific pressure (βf/βth) in Heliotron J device, under the conditions of different electron cyclotron resonance heating (ECH) and neutral beam injection (NBI). The results show that different characteristics are obtained under the different magnetic field geometry conditions. The results show that an increase in electron density can reduce the instability intensity by about 40%–60%, and an increase in the specific pressure of energetic particles can double the modal growth rate, while an increase in the specific pressure of hot particles has an inhibitory effect of 20%–50% on the growth rate of the low order modes. These findings are useful for understanding the different effects of ECH and NBI on the EPs driven MHD instabilities, and they are also helpful for achieving stable operation by adjusting the heating system parameters in the stellarator-like devices in the future.
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图 1 FAR3D程序中(a)密度、(b)温度及(c)温度剖面的平衡参数设置
Figure 1. Parameter settings in the FAR3D code: (a) Plasma density; (b) temperature; (c) temperature profile.
图 2 STELLGAP代码中等离子体电流剖面参数设计
Figure 2. Plasma current profile parameter design in STELLGAP code.
图 4 (a) 主导模态n/m = 2/4和n/m = 2/3的本征函数幅值空间分布计算结果; (b) 实验中模态相对强度与径向归一化坐标的关系
Figure 4. (a) Eigenfunction of the dominant mode of n/m = 2/4 and n/m = 2/3 mode; (b) radial profiles of mode relative intensities from experiments.
图 5 在Heliotron J装置中剪切阿尔芬连续谱在Ip = 0 (a)和Ip = 2.0 kA (b)下的MHD平衡状态下的表现
Figure 5. Shear Alfvén continuum structure in MHD equilibrium at Ip = 0 (a) and Ip = 2.0 kA (b) in Heliotron J.
图 6 在高ECH条件下, 不同电子密度下功率谱密度的时间演化(a)—(d)及不稳定性强度随电子密度的变化(e)
Figure 6. Time evolution of the power spectral density at different electron densities (a)–(d) and the variation of instability intensity with electron density (e) at high ECH situation.
图 7 在3种磁场位型下, 随着快粒子比压(βf)的变化 (a), (d) n/m = 1/2模的增长率和频率; (b), (e) n/m = 2/3模的增长率和频率; (c), (f) n/m = 2/4模的增长率和频率
Figure 7. Under three magnetic field configurations, with the change of the fast particle beta (βf): (a), (d) Growth rate and the frequency of the n/m = 1/2; (b), (e) growth rate and the frequency of the n/m = 2/3; (c), (f) growth rate and the frequency of the n/m = 2/4 mode.
图 8 n/m = 1/2, n/m = 2和n/m = 2/3模在3种磁场构型下, 随着热粒子比压(βth)增大的增长率与频率的变化情况 (a), (d) LB; (b), (e) MB; (c), (f) HB
Figure 8. Growth rate (γ) and the frequency (f) of the n/m = 1/2, n/m = 2/4, and n/m = 2/3 mode in the three configurations with the change of thermal particle beta (βth): (a), (d) LB; (b), (e) MB; (c), (f) HB
内容 FAR3D STELLGAP 目标 模拟模式的时域演化、增长率、结构,
适用于AE、不稳定性分析等分析阿尔芬连续谱结构, 识别频率gap,
判断是否支持共振模式(如TAE)目标输入要求 VMEC平衡态+粒子参数等 仅需VMEC平衡态 物理机制 包括电阻、Landau阻尼、Geodesic acoustic waves、波-粒共振等 不含耗散机制, 仅考虑MHD连续谱结构 
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表 2 加热过程影响的关键等离子体参数表
Table 2. Critical plasma parameters modified during heating.
等离子体参数 直接影响的物理量 作用效果 电子密度 热比压(βth),
等离子体压强(Pe)电子密度升高会通过降低快粒子相对压强(βf/βth)、增强碰撞与Landau阻尼、改变
阿尔芬速度与共振条件等间接途径增强阻尼, 有助于抑制高能粒子驱动的不稳定性电子温度 粒子慢化时间(τ),
快粒子比压(βf)双重作用: 降低βf有助于抑制模态激发(增加稳定性),
削弱阻尼可能提升模态增长率(降低稳定性)
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