Spin manipulation of 1.94 GeV/c polarized protons stored in the COSY cooler synchrotron

We recently studied spin flipping of a 1.94 GeV/c vertically polarized proton beam at COSY in Jülich, Germany. We swept an rf-dipole’s frequency through an rf-induced spin resonance to flip the beam’s polarization direction. After determining the resonance’s frequency, we varied the dipole’s strength, frequency range, and frequency ramp time. At the rf-dipole’s maximum strength, and optimum frequency range and ramp time, we measured a spin-flip efficiency of 99.3%±0.1%. This result indicates that an rf dipole may allow efficient spin flipping in high energy proton rings.