Amplitude of vortical turbulence in crossed fields in mass-separator at optimum parameters

It is well known from numerous numerical simulations (see, for example, [1]) and from experiments (see, for example [2]) that electron density nonuniformity in kind of discrete vortices are long-living structures. In experiments [2] a rapid re-organization of discrete electron density nonuniformity has been observed in the spatial distribution of vorticity in pure electron plasma when a discrete vortex has been immersed in an extended distribution of the background vorticity. In plasma lens [311] for high-current ion beam focusing, in mass-separator [12-16], in nuclear fusion [17-19] and in plasma-optical device for the elimination of droplets in cathodic ARC plasma coating [20], a vortical turbulence has been excited in crossed radial electrical and longitudinal magnetic fields [21-23] by gradient of external magnetic field or by gradient of plasma density. This turbulence is a distributed vorticity. In this paper the amplitude of the vortex saturation in cylindrical radially inhomogeneous plasma in crossed radial electric and axial magnetic fields in the mass-separator [14] for the optimal parameters are investigated theoretically. It is shown that as the parameters tend to the optimal ones the amplitude of excited vortices tends to zero. This allows to specify a range of parameters of the experimental setup for which the vortical turbulence is suppressed. Excitation of the vortices in the approximation of strongly magnetized electrons and weakly magnetized ions is studied analytically. Plasma is distributed inhomogeneously in radial direction and is a cylinder of finite length, placed in a magnetic field of short coil. It has been shown in [6] that the system is unstable relatively to excitation of oscillating fields in crossed fields. Excitation of the oscillation is realized as a result of a positive radial gradient of magnetic field of short coil and negative radial gradient of the plasma density. The ions drift on angle, , with a velocity Voi=eEor/miHi, Hi=eНо/mic, because the crossed configuration of radial electric, Eor, and longitudinal magnetic fields, Н0, is maintained in the separator. The perturbation of the plasma particle density leads to appearance of an electric field in the vicinity of the perturbation. Therefore, the crossed configuration of fields is realized in the vicinity of the perturbation. Thus, the dynamics of plasma particles is vortical in the field of perturbation. In this paper, the properties and the excitation of vortical perturbations in crossed fields in the massseparator are studied theoretically.