Experimental Verification of Predicted Oscillations near a Spin Resonance

The Chao matrix formalism allows analytic calculations of a beam’s polarization behavior inside a spin resonance. We recently tested its prediction of polarization oscillations occurring in a stored beam of polarized particles near a spin resonance. Using a $1.85 GeV/c$ polarized deuteron beam stored in COSY, we swept a new rf solenoid’s frequency rather rapidly through 400 Hz during 100 ms, while varying the distance between the sweep’s end frequency and the central frequency of an rf‐induced spin resonance. Our measurements of the deuteron’s polarization for sweeps ending near and inside the resonance agree with the Chao formalism’s predicted oscillations.