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Filamentation instabilities of dynamic Z pinches and theta pinches

1990; IOP Publishing; Volume: 32; Issue: 10 Linguagem: Inglês

10.1088/0741-3335/32/10/001

1361-6587

А. И. Клеев, A. L. Velikovich,

Atomic and Molecular Physics

Filamentation instability, which develops mainly due to plasma acceleration in dynamic pinches, is studied using the ideal MHD model in the linear approximation. For the cases of implosion of a Z pinch, expansion of an inverse Z pinch, implosion of a theta pinch and magnetic flux compression by an annular plasma liner, exact solutions describing the growth of the azimuthal perturbations in a cold plasma are found. For a theta pinch geometry the Rayleigh-Taylor mode of filamentation instability is shown to be the dominating mode, its effective growth rate for large wavenumbers being given by the known expression (gk)12/. For an annular Z pinch or liner the effective growth rate of the dominating mode differs from this expression by a factor smaller than unity. The concept of an effective growth rate is found to be inapplicable to the development of filamentation instabilities in the course of implosion of a solid Z pinch: in this case perturbations do not propagate with the plasma particles, they converge to the axis faster than the pinch itself.