Non-neutral plasma compression to ultrahigh density

Abstract

Oscillations of a cold, homogeneous, non-neutral plasma spheroid are considered. A new class of purely compressional, large-amplitude, nonlinear oscillations is found. With a periodically time-varying external electrostatic quadrupole and a static magnetic field, such oscillations periodically can produce arbitrarily large plasma densities with only a modest swing in the applied quadrupole. In limiting cases, one- to three-dimensional plasma oscillations are true normal modes, requiring no variation of the applied quadrupole. For appropriate parameters, peak density is associated with a very ‘‘soft core,’’ so that an extremely high density is associated with a very modest size at minimum density. Further, cold-plasma stability is examined for these cases. For three-dimensional oscillations, all modes are stable. For two-dimensional oscillations, modes with intermediate axial wavelengths are not examined in detail. Long-axial-wavelength modes are found to be unstable only for small oscillation amplitudes. These modes are stable at sufficiently large oscillation amplitude. Those modes with a very short axial wavelength are always stable. Thus, it is very likely that extremely high densities may be produced in a compact system.