Beam purification by selective trapping in the transfer line of an ISOL target unit

A new target and ion source unit has been developed at CERN-ISOLDE with the aim of delivering isobarically clean beams of short lived neutron-rich Cd and Zn. A quartz insert in the transfer line allows the retention and the decay of alkali contaminants by controlling its temperature from 308 °C to 792 °C. This paper presents the design of this transfer line. New alkali suppression factors are deduced from 80Rb, 8Li, 46K and 126,142Cs yield measurements. The enthalpy of adsorption for Rb and Cs is calculated from 80Rb and 126Cs suppression factors. The yield of 77Ga and 96Sr are presented.