V. A. Anferov

Siberian snake experiments at the IUCF Cooler Ring

Recent polarized proton beam experiments in the IUCF Cooler Ring found an evidence for a second-order snake depolarizing resonance, when the vertical betatron tune was inadvertently set near a quarter-integer. We have also studied the possibility of spin-flipping the beam polarization in the presence of a full Siberian snake using an RF solenoid. By varying the rf solenoids ramp time and frequency range, we reached a spin-flip efficiency of about 97%.

rf driven stable spin-flipping motion of a stored polarized beam

The traditional method of spin-flipping a stored polarized beam is based on slowly crossing an rf induced depolarizing resonance. This paper discusses a novel approach where the polarization reversal is achieved by trapping the beam polarization into a stable spin-flipping motion on top of the rf induced resonance at a half-revolution frequency.

99.9% Spin‐Flip Efficiency in the Presence of a Strong Siberian Snake

We recently studied the spin-flipping efficiency of an rf-dipole magnet using a 120-MeV horizontally polarized proton beam stored in the Indiana University Cyclotron Facility Cooler Ring, which contained a nearly full Siberian snake. We flipped the spin by ramping the rf dipoles frequency through an rf-induced depolarizing resonance. By adiabatically turning on the rf dipole, we minimized the beam loss. After optimizing the frequency ramp parameters, we used 100 multiple spin flips to measure a spin-flip efficiency of 99.63+/-0.05%. This result indicates that spin flipping should be possible in very-high-energy polarized storage rings, where Siberian snakes are certainly needed and only dipole rf-flipper magnets are practical.

Spin-flipping a stored polarized proton beam with an rf dipole

Frequent polarization reversals, or spin-flips, of a stored polarized high-energy beam may greatly reduce systematic errors of spin asymmetry measurements in a scattering asymmetry experiment. We studied the spin-flipping of a 120 MeV horizontally-polarized proton beam stored in the IUCF Cooler Ring by ramping an rf-dipole magnet’s frequency through an rf-induced depolarizing resonance in the presence of a nearly-full Siberian snake. After optimizing the frequency ramp parameters, we used multiple spin-flips to measure a spin-flip efficiency of 86.5±0.5%. The spin-flip efficiency was apparently limited by the rf-dipole’s field strength. This result indicates that an efficient spin-flipping a stored polarized beam should be possible in high energy rings such as RHIC and HERA where Siberian snakes are certainly needed and only dipole rf-flipper-magnets are practical.