Effect of a partial Siberian snake on an ‘‘rf-induced’’ depolarizing resonance

A recent experiment studied the effect of an rf solenoid magnet and a partial Siberian snake on a 120-MeV polarized proton beam. We measured the frequencies of the ‘‘rf-induced’’depolarizing resonance for different values of the snake strength; this frequency measurement determined the spin tune ${\nu }_{\mathrm{sp}}$, which is the number of spin processions in one turn around the ring. A 4% snake increased the frequency of the rf-induced depolarizing resonance by the predicted 11 kHz and thus shifted the spin tune by the predicted Δ${\nu }_{\mathrm{sp}}$=0.006 88±0.000 04; as expected the 4% snake also tilted the stable spin direction by more than 38° from the vertical.