PPPS-2013: High current iron-free pulsed quadrupole lenses

Abstract

For the transfer of ions between synchrotrons or for the final focus on targets, pulsed iron free quadrupole lenses are well suited. For those applications an extremely high field gradient is needed, that cannot be achieved with standard magnets as they are limited by saturation of the iron yoke. Another option would be superconducting magnets. High current pulsed lenses are able to produce a similar gradient for a short time as the superconducting magnets without the complex cryogenic systems. At least one doublet is needed to focus the ion bunches in both x- and y-axes. The current needed to reach magnetic field gradients for typical beam energies of the SIS18 is about 400 kA. Therefore the pulse duration need to be a few 10 μsec long. It is achieved by discharging a capacitor bank through a spark gap. The pulse is then applied to the four conductors forming the quardupole, which are switched in series. Each conductor is built of many separate lead strands, which are drilled and isolated against each other. By this the impacts of the skin effect are compensated. The shape of the conductor equals a cos(2θ)-distribution with respect to their dimensions and the distance to the beam. For the protection of close-by beamline components the quadrupole is shielded by an electromagnetic barrier which is laminated to avoid eddy currents. The concept and simulations will be presented.