Focusing behaviour of plasma lenses compared to conventional quadrupole systems

Abstract

Intense heavy ion beams focused to small spots are powerful tools to deposit a high specific deposition power in a target. A hot dense target plasma is formed which is available for further experimental investigation and to study beam-target interaction phenomena with relevance for the physics of inertial confinement (ICF) fusion. For a given set of beam parameters the minimum focused spot size is mainly limited by the focusing strength of the final lens system. Besides systems consisting of conventional quadrupoles also cylindrically symmetric, “active” plasma lenses have been built and tested at GSI attempting to overcome the limitations of quadrupole focusing. Superiour fine-focusing properties of plasma lenses have been demonstrated and a remarkable precision has been found. In this paper a quantitative comparison of the focusing strength of plasma lenses with conventional magnetic quadrupoles is presented.