Commissioning and future plans for polarized protons in RHIC

Polarized protons were injected and accelerated in the clockwise ring of RHIC to commission the first full helical Siberian snake ever used in an accelerator. With the snake turned on, the stable spin direction is in the horizontal plane. Vertically polarized protons were injected with the snake off. The snake was adiabatically ramped to give a spin rotation of 180° around a horizontal rotation axis about 13° from the longitudinal. When the beam was accelerated from injection Gγ = 46.5 to Gγ = 48 the spin flipped sign as expected and polarization was preserved. At Gγ = 48 without the snake, no polarization was observed since several spin resonances were crossed. Eventually polarized beam was accelerated to Gγ = 55.7 (29.1 GeV). In the next proton running period we plan to run with two full helical snakes in each ring and collide both transversely and longitudinally polarized protons at an energy around 100 GeV per beam