轴向流对Z箍缩等离子体稳定性的影响

The effect of axial flow on the stability in the Z-pinch

利用理想磁流体力学(MHD)模型对有轴向流参与的Z箍缩等离子体不稳定性进行了分析.对可压缩平板等离子体模型的色散关系进行了推导,讨论了三种不同等离子体状态下的不稳定性增长率.结果显示,等离子体的可压缩性对磁瑞利-泰勒/开尔文-亥姆霍兹(MRT/KH)杂化不稳定性有抑制作用,改善了轴向剪切流对长波长扰动的影响.分析了不同轴向流速度分布对系统稳定性的影响.结果表明,对于峰值相同的不同轴向流,其对不稳定性的抑制效果只依赖于扰动集中区域内速度剪切的大小,与其他位置的速度剪切无关.

A linear analysis of the ideal magnetohydrodynamic （MHD） stability of the Z-pinch is presented in which plasma flows are included in the equilibrium. Compressibility is introduced into MHD equations via the acoustic velocity of the plasma. It is found that, compressibility can stabilize the magneto-Rayleigh-Taylor/ Kelvin-Helmhohz （MRT/KH） instability, and this allows the sheared axial flow mitigate MRT instability far more effectively. Therefore, on the early stage of the implosion, because the temperature of the plasma is not high, the compressible model is much more suitable than the incompressible one. Different flow profiles have also been investigated, and it shows that the mitigation effect of the axial flow only depends on the magnitude of the velocity shear where the perturbations concentrate.