Chao Formalism & Kondratenko Crossing Tests

We recently started testing Chao's proposed new matrix formalism for describing the spin dynamics due to a single spin resonance; this seems to be the first generalization of the Froissart-Stora equation since it was published in 1960. The Chao matrix formalism allows one to calculate analytically the polarization's behavior inside a resonance, which is not possible using the Froissart-Stora equation. We recently tested some Chao formalism predictions using a 1.85 GeV/c polarized deuteron beam stored in COSY. We swept an rf dipole's frequency through 200 Hz while varying the distance from the sweep's end frequency to an rf-induced spin resonance's central frequency. While the Froissart-Stora formula can make no prediction in this case, the data seem to support the Chao formalism.We also started investigating the new Kondratenko method to preserve beam polarization during a spin resonance crossing; the method uses 3 rapid changes of the crossing rate near the resonance. With a proper choice of crossing parameters, Kondratenko Crossing may better preserve the polarization than simple fast crossing. We tested Kondratenko's idea using 2.1 GeV/c polarized protons stored in COSY; the frequency of a ferrite rf dipole was swept though an rf-induced spin resonance using Kondratenko's crossing shape. We have not yet observed a significant advantage of Kondratenko Crossing over simple fast crossing. We plan to study it further by choosing better crossing parameters and a smaller momentum spread.