Using a 104 MeV stored polarized proton beam and a full Siberian snake, we recently found evidence for a so-called “snake” depolarizing resonance. A full Siberian snake forces the spin tune ${\nu }_s$ to be a half integer. Thus, if the vertical betatron tune ${\nu }_y$ is set near a quarter integer, then the ${\nu }_s=n\pm 2{\nu }_y$ second-order snake resonance can depolarize the beam. Indeed, with a full Siberian snake, we found a deep depolarization dip when ${\nu }_y$ was equal to 4.756; moreover, when ${\nu }_y$ was changed to 4.781, the deep dip disappeared and the polarization was preserved.

• Received 19 December 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.2772