• K.A. Brown, L. Ahrens, M. Bai, J. Beebe-Wang, M. Blaskiewicz, J.M. Brennan, D. Bruno, C. Carlson, R. Connolly, T. D'Ottavio, R. De Maria, K.A. Drees, W. Fischer, W. Fu, C.J. Gardner, D.M. Gassner, J.W. Glenn, Y. Hao, M. Harvey, T. Hayes, L.T. Hoff, H. Huang, J.S. Laster, R.C. Lee, V. Litvinenko, Y. Luo, W.W. MacKay, M. Mapes, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, S. Nemesure, B. Oerter, F.C. Pilat, V. Ptitsyn, G. Robert-Demolaize, T. Roser, T. Russo, P. Sampson, J. Sandberg, T. Satogata, V. Schoefer, C. Schultheiss, F. Severino, K. Smith, D. Steski, S. Tepikian, C. Theisen, P. Thieberger, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, G. Wang, M. Wilinski, A. Zaltsman, K. Zeno, S.Y. Zhang
  BNL, Upton, Long Island, New York

Since the last successful RHIC Au+Au run in 2007 (Run7), the RHIC experiments have made numerous detector improvements and upgrades. In order to benefit from the enhanced detector capabilities and to increase the yield of rare events in the acquired heavy ion data a significant increase in luminosity is essential. In Run7 RHIC achieved an average store luminosity of <L>=12x10²⁶ cm^-2 s^-1 by operating with 103 bunches (out of 110 possible), and by squeezing to β*=0.8 m. Our goal for this year's run, Run10, was to achieve an average of <L>=27x10²⁶ cm^-2 s^-1. The measures taken were decreasing β* to 0.6 m, and reducing longitudinal and transverse emittances by means of bunched-beam stochastic cooling. In addition we introduced a lattice to suppress intra-beam scattering (IBS) in both RHIC rings, upgraded the RF system, and separated transition crossings in both rings while ramping. We present an overview of the changes and the results in terms of Run10 increased instantaneous luminosity, luminosity lifetime, and integrated luminosity.

• C. Montag, L. Ahrens, M. Bai, J. Beebe-Wang, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, R. Connolly, T. D'Ottavio, K.A. Drees, A.V. Fedotov, W. Fischer, G. Ganetis, C.J. Gardner, J.W. Glenn, H. Hahn, M. Harvey, T. Hayes, H. Huang, P.F. Ingrassia, J.P. Jamilkowski, A. Kayran, J. Kewisch, R.C. Lee, D.I. Lowenstein, A.U. Luccio, Y. Luo, W.W. MacKay, Y. Makdisi, N. Malitsky, G.J. Marr, A. Marusic, M.P. Menga, R.J. Michnoff, M.G. Minty, J. Morris, B. Oerter, F.C. Pilat, P.H. Pile, E. Pozdeyev, V. Ptitsyn, G. Robert-Demolaize, T. Roser, T. Russo, T. Satogata, V. Schoefer, C. Schultheiss, F. Severino, M. Sivertz, K. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, A. Zaltsman, A. Zelenski, K. Zeno, S.Y. Zhang
  BNL, Upton, Long Island, New York

During the second half of Run-9, the Relativistic Heavy Ion Collider (RHIC) provided polarized proton collisions at two interaction points with both longitudinal and vertical spin direction. Despite an increase in the peak luminosity by up to 40%, the average store luminosity did not increase compared to previous runs. We discuss the luminosity limitations and polarization performance during Run-9.

• C. Montag, M. Blaskiewicz, J.M. Brennan, S. Tepikian
  BNL, Upton, Long Island, New York

During the acceleration process, heavy ion beams in RHIC cross the transition energy. When RHIC was colliding deuterons and gold ions during Run-8, lattices with different integer tunes were used for the two rings. This resulted in the two rings crossing transition at different times, which proved beneficial for the "Yellow" ring, the RF system of which is slaved to the "Blue" ring. For the symmetric gold-gold run in FY2010, lattices with different transition energies but equal tunes were implemented. We report the optics design concept as well as operational experience with this configuration.

• G. Wang, M. Blaskiewicz, V. Litvinenko
  BNL, Upton, Long Island, New York

We report recent progresses on analytical studies of Coherent Electron Cooling. The phase space electron beam distribution obtained from the 1D FEL amplifier is applied to an infinite electron plasma model and the electron density evolution inside the kicker is derived. We also investigate the velocity modulation in the modulator and obtain a closed form solution for the current density evolution for infinite homogeneous electron plasma.

• A. Hershcovitch, M. Blaskiewicz, J.M. Brennan, W. Fischer, C.J. Liaw, W. Meng
  BNL, Upton, Long Island, New York
• A.X. Custer, M.Y. Erickson, N.Z. Jamshidi, H.J. Poole
  PVI, Oxnard
• N. Sochugov
  Institute of High Current Electronics, Tomsk

Electron clouds, which can limit machine performance, have been observed in many accelerators including RHIC at BNL. They can be suppressed by low secondary electron yield beam pipe surfaces. Additional concern for the RHIC machine, whose vacuum chamber is made from relatively high resistivity 316LN stainless steel, is high wall resistivity that can result in unacceptably high ohmic heating for superconducting magnets. The high resistivity can be addressed with a copper (Cu) coating; a reduction in the secondary electron yield can be achieved with a TiN or amorphous carbon (a-C) coating. Applying such coatings in an already constructed machine is rather challenging. We started developing a robotic plasma deposition technique for in-situ coating of long, small diameter tubes. The technique entails fabricating a device comprising of staged magnetrons mounted on a mobile mole for deposition of about 5 μm (a few skin depths) of Cu followed by about 0.1 μm of a-C. As a first step, a 15-cm Cu cathode magnetron is being designed and fabricated, after which, 30-cm long sample of the RHIC pipe are to be Cu coated. Deposition rates and affects on RF resistivity are to be measured.

• V. Ptitsyn, M. Blaskiewicz, W. Fischer, R.C. Lee, S.Y. Zhang
  BNL, Upton, Long Island, New York

A fast transition instability presents a limiting factor for ion beam intensity in RHIC. Several pieces of evidence show that electron clouds play an important role in establishing the threshold of this instability. In RHIC Runs 7 and 8 dedicated measurements of the instability, using different beam instrumentation tools (Button BPM, Wall Current Monitor, transition monitors) were done in order to observe the instability development over hundreds turns. The papers presents and discusses the results of those measurements in time and frequency domains.

• G. Wang, M. Blaskiewicz, A.V. Fedotov, Y. Hao, J. Kewisch, V. Litvinenko, E. Pozdeyev, V. Ptitsyn
  BNL, Upton, Long Island, New York

We present our studies on various aspects of the beam dynamics in 'racetrack' design of the first stage electron-ion collider at RHIC (eRHIC), including transverse beam break up instabilities, electron beam emittance growth and energy loss due to synchrotron radiation, electron beam losses due to Touschek effects and residue gas scattering, beam-beam effects at the interaction region and emittance growth of ion beam due to electron bunch to bunch noises. For all effects considered above, no showstopper has been found.