RHIC SPIN FLIPPER COMMISSIONING

An ac dipole with horizontally oriented oscillating mag-netic field (spin flipper) was installed in RHIC to reverse the spin direction in the presence of two full Siberian snakes, thereby reducing the systematic errors for the spin physics experiments in RHIC. With two full snakes, the spin vector completes one full precession around the ver-tical direction in two revolutions, and the spin depolariza-tion resonances due to the machine imperfections and beta-tron oscillations are eliminated. Since the spin flipper pro-vides an oscillating horizontal dipole field, a “spin reso-nance ” can occur if the spin flipper frequency is placed in the neighborhood of the spin precession frequency [1, 2, 3]. By slowly sweeping the spin flipper frequency across the spin precession frequency, a full spin flip can be achieved. This paper reports the results of the RHIC spin flipper com-missioned during the RHIC 2002 polarized proton run. By running the spin flipper at a slightly different configuration, one can also measure the spin precession tune.