• M. Bai, L. Ahrens, J.G. Alessi, J. Beebe-Wang, M. Blaskiewicz, A. Bravar, J.M. Brennan, 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. Glenn, T. Hayes, H.-C. Hseuh, H. Huang, P. Ingrassia, U. Iriso, 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, T. Nicoletti, P. Oddo, B. Oerter, O. Osamu, F.C. Pilat, V. Ptitsyn, T. Roser, T. Satogata, K. Smith, S. Tepikian, R. Tomas, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, K. Vetter, M. Wilinski, A. Zaltsman, A. Zelenski, K. Zeno, S.Y. Zhang
  BNL, Upton, Long Island, New York
• I.G. Alekseev, D. Svirida
  ITEP, Moscow

The Relativistic Heavy Ion Collider~(RHIC) provides not only collisions of ions but also collisions of polarized protons. In a circular accelerator, the polarization of polarized proton beam can be partially or fully lost when a spin depolarizing resonance is encountered. To preserve the beam polarization during acceleration, two full Siberian snakes were employed in RHIC to avoid depolarizing resonances. In 2003, polarized proton beams were accelerated to 100~GeV and collided in RHIC. Beams were brought into collisions with longitudinal polarization at the experiments STAR and PHENIX by using spin rotators. RHIC polarized proton run experience demonstrates that optimizing polarization transmission efficiency and improving luminosity performance are significant challenges. Currently, the luminosity lifetime in RHIC is limited by the beam-beam effect. The current state of RHIC polarized proton program, including its dedicated physics run in 2005 and efforts to optimize luminosity production in beam-beam limited conditions are reported.

• G.D. Wait, R.B. Armenta, M.J. Barnes, E.W. Blackmore, O. Hadary
  TRIUMF, Vancouver
• L. Ahrens, C.J. Gardner, W. Zhang
  BNL, Upton, Long Island, New York

The present AGS injection kickers at A5 location were designed for 1.5 GeV proton injection. Recent high intensity runs have pushed the transfer kinetic energy to 1.94 GeV, but with an imperfect matching in transverse phase space. Space charge forces result in both fast and slow beam size growth and beam loss as the size exceeds the AGS aperture. A proposed increase in the AGS injection energy to 2 GeV with adequate kick strength would greatly reduce the beam losses making it possible to increase the intensity from 70 TP (70 * 10¹² protons/s) to 100 TP. R&D studies are being undertaken by TRIUMF, in collaboration with BNL, to design two new kicker magnets for the AGS A10 location to provide an additional kick of 1.5 mrad to 2 GeV protons. TRIUMF has proposed a design for a 12.5 W transmission line kicker magnet with rise and fall times of 100 ns, 3% to 97% and field uniformity of ±3% over 90% of the aperture, powered by matched 12.5 W pulse-forming lines. This paper describes the present status of a prototype design including the results of detailed 2D and 3D electromagnetic modeling of a transmission line kicker magnet and PSpice time domain analysis of the magnetic kick strength.

• F.C. Pilat, L. Ahrens, M. Bai, D.S. Barton, J. Beebe-Wang, M. Blaskiewicz, J.M. Brennan, D. Bruno, P. Cameron, R. Connolly, T. D'Ottavio, J. DeLong, K.A. Drees, W. Fischer, G. Ganetis, C.J. Gardner, J. Glenn, M. Harvey, T. Hayes, H.-C. Hseuh, H. Huang, P. Ingrassia, U. Iriso, R.C. Lee, V. Litvinenko, Y. Luo, W.W. MacKay, G.J. Marr, A. Marusic, R.J. Michnoff, C. Montag, J. Morris, T. Nicoletti, B. Oerter, V. Ptitsyn, T. Roser, T. Russo, J. Sandberg, T. Satogata, C. Schultheiss, S. Tepikian, R. Tomas, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, K. Vetter, A. Zaltsman, K. Zeno, S.Y. Zhang, W. Zhang
  BNL, Upton, Long Island, New York

The 5th year of RHIC operations, started in November 2004 and expected to last till June 2005, consists of a physics run with Cu-Cu collisions at 100 GeV/u followed by one with polarized protons at 100 GeV. We will address here overall performance of the RHIC complex used for the first time as a Cu-Cu collider, and compare it with previous operational experience with Au, PP and asymmetric d-Au collisions. We will also discuss operational improvements, such as a ?* squeeze to 85cm in the high luminosity interaction regions from the design value of 1m, system improvements and machine performance limitations, such as vacuum pressure rise, intra-beam scattering, and beam beam interaction.

• V. Litvinenko, L. Ahrens, M. Bai, J. Beebe-Wang, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, R. Calaga, X.Y. Chang, A.V. Fedotov, W. Fischer, D. Kayran, J. Kewisch, W.W. MacKay, C. Montag, B. Parker, S. Peggs, V. Ptitsyn, T. Roser, A. Ruggiero, T. Satogata, B. Surrow, S. Tepikian, D. Trbojevic, V. Yakimenko, S.Y. Zhang
  BNL, Upton, Long Island, New York
• A. Deshpande
  Stony Brook University, Stony Brook
• M. Farkhondeh
  MIT, Middleton, Massachusetts

We present the designs of a future polarized electron-hadron collider, eRHIC* based on a high current super-conducting energy-recovery linac (ERL) with energy of electrons up to 20 GeV. We plan to operate eRHIC in both dedicated (electron-hadrons only) and parallel(with the main hadron-hadron collisions) modes. The eRHIC has very large tunability range of c.m. energies while maintaining very high luminosity up to 1034 cm-2 s-1 per nucleon. Two of the most attractive features of this scheme are full spin transparency of the ERL at all operational energies and the capability to support up to four interaction points. We present two main layouts of the eRHIC, the expected beam and luminosity parameter, and discuss the potential limitation of its performance.

*http://www.agsrhichome.bnl.gov/eRHIC/, Appendix A: Linac-Ring Option.

• C. Montag, L. Ahrens, P. Thieberger
  BNL, Upton, Long Island, New York

During beam acceleration at the Brookhaven accelerator complex, heavy ions are stripped off their electrons in several steps. Depending on the properties of the stripping foils, this process results in an increased energy spread and therefore longitudinal emittance growth. A tomographic phase space reconstruction technique has been applied to quantify the associated emittance growth for different stripping foil materials.

• J. Takano, M. Okamura
  RIKEN, Saitama
• L. Ahrens, M. Bai, K.A. Brown, C.J. Gardner, J. Glenn, H. Huang, A.U. Luccio, W.W. MacKay, T. Roser, S. Tepikian, N. Tsoupas
  BNL, Upton, Long Island, New York
• T. Hattori
  RLNR, Tokyo

A normal conducting helical dipole partial Siberian snake (Warm Snake) has been installed in the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL) for overcoming all of imperfection depolarizing resonances and reducing the transverse coupling resonances caused by the solenoidal Siberian snake which had been operated in AGS before the last polarized run. The polarized proton beam has been accelerated successfully with the warm snake and the polarization at extraction of the AGS was increased to 50% as opposed to 40% with the solenoidal snake. The magnetic field and beam trajectory in the warm snake was calculated by using the OPERA-3D/TOSCA software. We present optimization of the warm snake with beam during RUN5.

• H. Huang, L. Ahrens, M. Bai, A. Bravar, K.A. Brown, G. Bunce, E.D. Courant, C.J. Gardner, J. Glenn, R.C. Gupta, A.U. Luccio, W.W. MacKay, V. Ptitsyn, T. Roser, S. Tepikian, N. Tsoupas, E. Willen, A. Zelenski, K. Zeno
  BNL, Upton, Long Island, New York
• F. Lin
  IUCF, Bloomington, Indiana
• M. Okamura
  RIKEN/RARF/CC, Saitama
• J. Takano
  RIKEN, Saitama
• D.G. Underwood
  ANL, Argonne, Illinois
• J. Wood
  UCLA, Los Angeles, California

The RHIC spin program requires 2*10¹¹ proton/bunch with 70% polarization. As the injector to RHIC, AGS is the bottleneck for preserving polarization: there is not enough space in the ring to install a full snake to overcome the numerous depolarizing resonances. An ac dipole and a partial Siberian snake have been used to preserve beam polarization in the past. The correction with this scheme is not 100% since not all depolarizing resonances can be overcome. Recently, two helical snakes with double pitch design have been built and installed in the AGS. With careful setup of optics at injection and along the ramp, this combination can eliminate all depolarizing resonances encountered during acceleration. This paper presents the accelerator setup and preliminary results.

• C.J. Gardner, L. Ahrens, J.G. Alessi, J. Benjamin, M. Blaskiewicz, J.M. Brennan, K.A. Brown, C. Carlson, J. DeLong, J. Glenn, T. Hayes, W.W. MacKay, G.J. Marr, J. Morris, T. Roser, F. Severino, K. Smith, D. Steski, N. Tsoupas, A. Zaltsman, K. Zeno
  BNL, Upton, Long Island, New York

Copper ions for the 2005 run of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory are accelerated in the Tandem, Booster and AGS prior to injection into RHIC. The setup and performance of this chain of accelerators will be reviewed.