| Popis: |
There are two important specific features in the stability analysis of dynamic Z pinches and plasma liners. First, the unperturbed state is itself time dependent, so that the time dependence of the perturbations cannot be taken in the form exp(Γ ·t)and it is not obvious which parameters should be used to characterize the growth instead of the conventional exponential growth rate. Second, the RT instability (see review by Kull, 1991) now comes into play. Indeed, plasma is imploded (accelerated) by the pressure due to the azimuthal magnetic field in a dynamic Z pinch or liner. Thus, the plasma, in its own frame of reference, represents a “heavy fluid,” which is supported by a “massless fluid” (i.e., by the magnetic field) in the gravitational fieldg = —awherea is its acceleration, and this configuration inevitably exhibits the RT instability. In this respect, Z pinches are quite similar to other systems in which plasma or solid objects are electromagnetically accelerated, including rail guns and other electromagnetic guns, and also to laser fusion systems of plasma acceleration, where the high-temperature, low-density plasma corona acts as a “light fluid.” |
