Axial Flow Z-pinch Plasma Instabilities

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, the sheared axial flow can mitigate and even stabilize the Rayleigh-Taylor(RT) instability in a large wavenumber region (for normalized wavenumber K > 2.4), but it also makes Kelvin-Helmholtz (KH) instability grow fast. It is also found that, compressibility can stabilize the RT/KH instability, and this allows the sheared axial flow mitigate RT instability more effectively. Therefore, on the early stage of the implosion, because the temperature of the plasma is not very 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 is only depend on the magnitude of the velocity shear where the perturbations concentrate.