The optics of ISOLDE 3 — The new on-line mass separator at CERN

Abstract The optical design of the new ISOLDE 3 on-line separator at CERN is presented. This separator consists of a beam transfer section, a two-stage mass separator and a beam distribution system. The beam transfer section contains five electrostatic quadrupoles, while the mass separator consists of 90° and 60° magnetic sector fields with 1-m radii of deflection plus four electrostatic quadrupoles. The two dipoles of the separator are planned to operate at different electrostatic potentials which should eliminate all residual gas scattered ions as well as all ions formed by charge exchange processes in the acceleration region. The rather complex beam transport system can be matched to four different types of ion sources. Both magnets are intended to be equipped with surface coils. In addition to these coils, three electrostatic multipoles are foreseen which together should allow a sufficient correction of image aberrations for the four types of ion sources. The overall system is designed to achieve resolving powers which should allow separation of elements within one isobar at least for short-lived nuclei with high Q β values.