Beam-based alignment at the Cooler Synchrotron COSY as a prerequisite for an electric dipole moment measurement
The direct measurement of the Electric Dipole Moment (EDM) of protons and deuterons using a storage ring is based on a precise determination of the change of the polarization vector caused by the EDM. In order to reach highest accuracy, one has to know the exact trajectory through the magnets, especially the quadrupoles, to avoid the influence of magnetic fields on the polarization vector. Here, the development of a beam-based alignment technique is described that was developed and implemented at the COoler SYnchrotron (COSY) at Forschungszentrum Jülich. Well aligned quadrupoles permit one to absolutely calibrate the Beam Position Monitors (BPMs). The method is based on the fact that a particle beam, which does not pass through the center of a quadrupole, experiences a deflection. The precision reached by the method is approximately 40μm. This also implies some consequences for the design of a new high precision storage ring for EDM mesasurements.