Acceleration of Polarized Protons and Deuterons at COSY

Abstract

At the cooler synchrotron COSY, protons and deuterons are accelerated up to 3.65 GeV/c. Vertically polarized proton beams with more than 70% polarization have been delivered in recent years to internal as well as to external experiment areas at different momenta up to the maximum momentum of COSY. In a strong‐focusing synchrotron like COSY, imperfection and intrinsic resonances cause polarization losses during acceleration. The existing magnet system of COSY allows to overcome all imperfection resonances by exciting adiabatic spin flips without polarization losses. A tune‐jump system consisting of two fast quadrupoles has been developed to handle intrinsic resonances in COSY. This magnet system is being successfully utilized at all intrinsic resonances in the momentum range of COSY. For the acceleration of vertically polarized deuterons, additional correction provisions are not necessary to preserve polarization during acceleration because depolarizing resonances are not crossed in the momentum range of COSY at ordinary transversal betatron tunes. In future upgrades we are planning to install spin rotators to provide longitudinally polarized beam to internal as well as to external experiments. Such devices can also be used as Siberian snake to overcome depolarizing resonances. Since strong first order depolarizing resonances are crossed in COSY, it will be possible to study snake resonances in detail. In particular the behavior of the spin field and the mechanism of polarization loss during snake resonance crossing are of major interest for high energy polarized beam acceleration. In this paper the status of the polarized beam acceleration at COSY is presented and the upgrade plans are discussed.