RHIC POLARIZED PROTON OPERATION IN RUN 12

Successful RHIC operation with polarized protons requires meeting demanding and sometimes competing goals for maximizing both luminosity and beam polarization. Run 12 consisted of four weeks of collisions with 100 GeV beams and five weeks colliding 255 GeV beams. We sought to fully integrate into operation the many systems that were newly commissioned in Run 11 as well as to enhance collider performance with incremental improvements throughout the acceleration cycle. Improvements to the luminosity were provided largely by increased intensity delivered by the polarized proton source. Increases in beam polarization came from improvements in both the injectors and in RHIC. OVERVIEW The Run 12 polarized proton run was divided between four weeks of physics at 100 GeV and five weeks of collisions at 255 GeV. At 100 GeV the stable spin direction at both interaction points (IPs 6 and 8) was vertical (no spin rotation), and for 255 GeV, longitudinally (achieved with helical dipole spin rotators on either side of each IP). Instantaneous, relative polarization measurements are made with carbon target polarimeters. The carbon polarimeter measurements are calibrated with a polarized atomic hydrogen jet target polarimeter (‘the Jet’), which is capable of absolute polarization measurements made continuously over a full eight hour store length. The store working point for both energies was between the 2/3 and 7/10 betatron resonances at (Qx,Qy) = (28.695, 29.685). Because 7/10 is also a strong spin depolarizing snake resonance, the vertical tune in both rings was lowered to 29.672 during the portion of the acceleration ramp between 100 GeV and 255 GeV, when depolarizing resonances are strongest [1]. The proximity to the 2/3 resonance makes tune, coupling and orbit feedback essential on every acceleration ramp [2]. Both programs benefitted from improvements in the injectors. In typical operation, the OPPIS source [3] delivers a factor of two or more higher intensity than is needed for