Moderate energy metal ion beam focusing by a high-current plasma lens

Some features of the electrostatic plasma lens as applied to the focusing of moderate-energy, high-current, wide-aperture metal ion beams have been investigated and are described here. Static characteristics within the plasma lens volume have been explored. It is shown that when the potentials applied to the lens electrodes are held constant, the electric field increase with increasing ion beam current is limited by the increase of the potential in the paraxial region of the beam. Some estimates are made of the limiting static electric fields that can be obtained in the plasma lens, based on a quasi-neutral, two-component plasma model with anomalous electron mobility, where it is assumed that the anomalous mobility is caused by the absence of electron correlations when vortex-like structures appear in the hydrodynamically unstable plasma. The results of a theoretical analysis are compared with experimental data. Some results of experiments on the focusing of high-current, large area, heavy metal ion beams are also presented.