Evolution of 2D electron vortices structures in crossed ExH-fields high-current plasma lens

We describe formation, stable existence and dynamics of 2D electron vortices structures in crossed electric and magnetic fields. As has been shown earlier on, the example of high-current plasma lens, the disturbed motion of electrons in variable electric fields caused by the principally irremovable radial gradient of the magnetic field axial component is transformed into the set of single vortexes. The nonlinear differential equation of the electric potential describing such vortices structures has been received and its stationary solutions in the form of the single small scaled vortexes was found for different configurations of external magnetic fields. Here we describe formation and evolution of vortices structures by using computer simulations based on determined experimental conditions. It is shown that under initial small azimuthal disturbance of static potential some vortices are created, and then are joined into one single large vortex with amplitude that is limited. This structure is stable and drifts along the azimuth direction. Time of their appearance is approximately one-two periods of oscillation. The formation of such vortices structures can limit maximum values of space electrostatic fields in plasma optics and leads to failure of equipotentialization of H-field strength lines and may evoke additional spherical and momentum aberrations. This will affect characteristics of the focused ion beam. Result of calculations and estimations of maximum potential values, time of appearance, drift and rotate velocity of vortices structures are done.