Simulation of decays and secondary ion losses in a betabeam decay ring

Radioactive ions injected into the decay ring of aBetabeam neutrino facility will constitute a continuoussource of decay products distributed around the ring.Secondary ions from beta decays will differ in chargestate from the primary ions and will follow widely offmomentumorbits. In the racetrack configuration of thering, they will be mismatched in the long straights and mayacquire large amplitudes, but the great majority of losseswill be in the arcs. We describe here a comprehensivemodel of ion decay, secondary ion tracking, and loss detection,which has been implemented in the tracking andsimulation code Accsim. Methods have been developed toaccurately follow ion trajectories at large momentum deviationsas well as to detect their impact coordinates on vacuumchamber walls and possibly inside magnetic elements.Using secondary-ion data from Accsim and postprocessingwith Mathematica, we have implemented afollow-on simulation in FLUKA with a 3D geometry ofdecay ring components and physics models for ion interactionsin matter, allowing radiological studies and in particularthe visualization and analysis of heat deposition in thedipole magnets which is a critical design factor for the ring.In our simulations we have also implemented absorber elementswhich are intended to localize the majority of lossesoutside of the dipoles.These studies provide estimates of ring performance (interms of loss concentration and management), the effectivenessof absorbers, and the implications for successfulsuperconducting dipole operation.