Simulation of an off-line ion beam system at ISOLDE

On-line isotope separation (ISOL) is a technique in which the ion source of an electromagnetic mass-separator is coupled directly to an accelerator target with high energy protons (1.4 GeV at ISOLDE) so that a continuous beam of unstable nuclei emerges. These isotopes, produced by the driver beam and stopped in the target, are transported into the ion source as atoms by diffusion and effusion processes, where they get ionized and extracted by an applied potential. In order to facilitate testing and development of different ion source types at ISOLDE, a dedicated offline ion source is in development. This includes a standard ISOLDE target geometry directly coupled to a vacuum chamber. However, the initial version of the offline ion source shall be upgraded to accommodate mass separation in form of a quadrupole mass filter. In this work, the first version of the new beamline was defined and ion beam trajectories up to the quadrupole exit were simulated using the SIMION program to get first insights into parameters such as AC and DC voltages, frequency as well as kinetic energy, mass and the charge of the ions as well as finalize the design of the beamline.