Aberrations due to solenoid focusing of a multiply charged high-current ion beam

Abstract

At the output of a laser ion source, a high current of highly charged ions with a large range of charge-states is available. The focusing of such a beam by magnetic elements causes a non-linear space-charge field to develop which can induce large aberrations and emittance growth in the beam. Simulation of the beam from the CERN laser ion source will be presented for an ideal magnetic and electrostatic system using a radially symmetric model. In addition, the 3D software KOBRA3 is used for the simulation of the solenoid line. The results of these simulations will be compared with experiments performed on the CERN laser ion source with solenoids (resulting in a hollow beam) and a series of gridded electrostatic lenses.

Status of the CO2 laser ion source at CERN

“…The current appears to be limited by the non-linear space charge forces [6] which are produced when the ion beams of different charge-state are separately focused by the magnetic field of the solenoid. In this case the ion beam quality is compromised and only a small fraction of the beam can be focused into the cup aperture.…”