HIGH-CURRENT PLASMA LENS

The static and dynamic characteristics of a high-current plasma lens (PL) with a two-component quasineutral plasma medium formed by a wide-aperture, repetitively pulsed ion beam and secondary electron emission have been investigated experimentally. Such a system provides magnetic isolation of electrons and ion beam focusing by means of uncompensated space charge electric fields. It is shown that careful selection of the magnetic field geometry, the number of lens electrodes, and the external potential distribution applied to them according to theoretical plasma-optics principles, allows the radial electric potential profile within the PL volume to be tailored widely. We show that there is a significant influence of the ion beam itself on the potential shape. Lens collective processes due to nonremovable radial gradients of the magnetic field in the ion beam focusing direction are investigated. It is shown that the conductivity mechanism and lens electrode leakage are connected with observed small-scaled turbulence. A theoretical analysis of the linear growth phase of an instability is presented and estimates made of the nonlinear variable potential amplitude.