Adiabatic partial Siberian snake turn-on with no beam depolarization

A recent experiment in the IUCF cooler ring studied the adiabatic turn-on of a partial Siberian snake at 370 MeV, where the spin tune, ${\ensuremath{\nu}}_{\mathit{s}}$ is 21/2 for all snake strengths. The snake consisted of two rampable warm solenoid magnets in series with a superconducting solenoid; this combination allowed varying the snake strength between about 0 and 25% at 370 MeV. We measured the beam polaraization after varying the snake either 1, 2, or 10 times; we found with good precision that no polarization was lost. This supports the conjecture that a Siberian snake can be ramped adiabatically at an energy where the spin tune is a half integer.