Overcoming Intrinsic and Coupling Spin Resonances in the AGS

Abstract

In the Brookhaven AGS, polarized protons are accelerated from Gγ = 4.5 to Gγ = 46.5. During the acceleration, a total of 42 imperfection spin depolarization resonances and 7 intrinsic spin resonances are crossed. Currently, the depolarization at each imperfection spin resonance is overcome by a solenoid 5% snake and full spin flips are induced at 4 out of the 7 intrinsic resonances by the AGS rf dipole to avoid the polarization loss. No correction schemes are applied at the remaining 3 weak spin resonances. In addition, coupling spin resonances are also observed due to the solenoidal field of the snake and no correction is applied for these spin resonances other than keeping the horizontal and vertical betatron tunes separated. In order to achieve ⩾ 50% beam polarization out of AGS, all of those spin resonances need to be corrected. This paper proposes three correction methods to overcome the strong intrinsic spin resonances as well as the weak intrinsic spin resonances and the coupling spin resonances.