• H. Huang, L. Ahrens, M. Bai, K. A. Brown, C. J. Gardner, J. W. Glenn, F. Lin, A. U. Luccio, W. W. MacKay, T. Roser, S. Tepikian, N. Tsoupas, K. Yip, K. Zeno
  BNL, Upton, Long Island, New York

Dual partial snake scheme has provided polarized proton beams with 1.5*10¹¹ intensity and 65% polarization for RHIC spin program. To overcome the residual polarization loss due to horizontal resonances in the AGS, a new string of quadrupoles have been added. The horizontal tune can now be set in the spin tune gap generated by the two partial snakes, such that horizontal resonances are avoided. This paper presents the accelerator setup and preliminary results.

• T. V. Shaftan, J. Beebe-Wang, J. Bengtsson, G. Ganetis, W. Guo, R. Heese, H.-C. Hseuh, E. D. Johnson, V. Litvinenko, A. U. Luccio, W. Meng, S. Ozaki, I. Pinayev, S. Pjerov, D. Raparia, J. Rose, S. Sharma, J. Skaritka, C. Stelmach, N. Tsoupas, D. Wang, L.-H. Yu
  BNL, Upton, Long Island, New York

We present conceptual design of the NSLS-II injection system. The injection system consists of low-energy linac, booster and transport lines. We review the requirements on the injection system imposed by the storage ring design and means of meeting these requirements. We discuss main parameters and layout of the injection system components.

• M. Bai, A. U. Luccio, Y. Makdisi, P. H. Pile, T. Roser
  BNL, Upton, Long Island, New York

Full spin flip in the presence of full Siberian snake has been achieved by using an rf dipole or solenoid as spin flipper at IUCF and COSY. This technique requires one to change the snake configuration to move the spin tune away from half integer. However, this is not practical for an operational high energy polarized proton collider like RHIC where beam lifetime is sensitive to small betatron tune change. An new technique of achieving full spin flip with the spin tune staying at half integer is proposed. This paper presents the design of RHIC spin flipper along with simulation results.

• M. Bai, P. Cameron, H. Huang, A. U. Luccio, V. Ptitsyn, T. Roser, S. Tepikian
  BNL, Upton, Long Island, New York

Snake depolarizing resonances due to the imperfect cancellation of the accumulated perturbations on the spin precession between snakes were observed at the Relativistic Heavy Ion Collider~(RHIC). During the RHIC 2005 and 2006 polarized proton runs, we mapped out the spectrum of odd order snake resonance at Q_y=7/10. Here, Q_y is the beam vertical betatron tune. We also studied the beam polarization after crossing the 7/10th resonance as a function of resonance crossing rate. This paper reports the measured resonance spectrum as well as the results of resonance crossing.

The work was performed under the US Department of Energy Contract No. DE-AC02-98CH1-886, and with support of RIKEN(Japan) and RenaissanceTechnologies C orp.(USA)

• M. Bai, L. Ahrens, I. G. Alekseev, J. G. Alessi, J. Beebe-Wang, M. Blaskiewicz, A. Bravar, J. M. Brennan, K. A. Brown, D. Bruno, G. Bunce, J. J. Butler, P. Cameron, R. Connolly, T. D'Ottavio, J. DeLong, K. A. Drees, W. Fischer, G. Ganetis, C. J. Gardner, J. W. Glenn, T. Hayes, H.-C. Hseuh, H. Huang, P. F. Ingrassia, J. S. Laster, R. C. Lee, A. U. Luccio, Y. Luo, W. W. MacKay, Y. Makdisi, G. J. Marr, A. Marusic, G. T. McIntyre, R. J. Michnoff, C. Montag, J. Morris, P. Oddo, B. Oerter, J. Piacentino, F. C. Pilat, V. Ptitsyn, T. Roser, T. Satogata, K. Smith, S. Tepikian, D. Trbojevic, N. Tsoupas, J. E. Tuozzolo, M. Wilinski, A. Zaltsman, A. Zelenski, K. Zeno, S. Y. Zhang
  BNL, Upton, Long Island, New York
• D. Svirida
  ITEP, Moscow

The Relativistic Heavy Ion Collider~(RHIC) as the first high energy polarized proton collider was designed to provide polarized proton collisions at a maximum beam energy of 250GeV. It has been providing collisions at a beam energy of 100GeV since 2001. Equipped with two full Siberian snakes in each ring, polarization is preserved during the acceleration from injection to 100GeV with careful control of the betatron tunes and the vertical orbit distortions. However, the intrinsic spin resonances beyond 100GeV are about a factor of two stronger than those below 100GeV making it important to examine the impact of these strong intrinsic spin resonances on polarization survival and the tolerance for vertical orbit distortions. Polarized protons were accelerated to the record energy of 250GeV in RHIC with a polarization of 45\% measured at top energy in 2006. The polarization measurement as a function of beam energy also shows some polarization loss around 136GeV, the first strong intrinsic resonance above 100GeV. This paper presents the results and discusses the sensitivity of the polarization survival to orbit distortions.

• F. Lin, S.-Y. Lee
  IUCF, Bloomington, Indiana
• L. Ahrens, M. Bai, K. A. Brown, E. D. Courant, J. W. Glenn, H. Huang, A. U. Luccio, W. W. MacKay, T. Roser, N. Tsoupas
  BNL, Upton, Long Island, New York

Two partial helical dipole snakes were found to be able to overcome all imperfection and intrinsic spin resonances provided that the vertical betatron tunes were maintained in the spin tune gap near the integer 9. Recent vertical betatron tune scan showed that the two weak resonances at the beginning of the acceleration cycle may be the cause of polarization loss. This result has been confirmed by the vertical polarization profile measurement, and spin tracking simulations. Possible cure of the remaining beam polarization is discussed.

• M. Conte
  INFN Genova, Genova
• A. U. Luccio, W. W. MacKay
  BNL, Upton, Long Island, New York
• M. Pusterla
  Univ. degli Studi di Padova, Padova