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Fedotov, A. V.

Paper Title Page
TUZAKI01 RHIC Plans Towards Higher Luminosity 709
 
  • A. V. Fedotov
    BNL, Upton, Long Island, New York
 
  Funding: Work supported by the U. S. Department of Energy under contract No. DE-AC02-98CH10886.

The Relativistic Heavy Ion Collider (RHIC) is designed to provide luminosity over a wide range of beam energies and species, including heavy ions, polarized protons, and asymmetric beam collisions. In the first seven years of operation there has been a rapid increase in the achieved peak and average luminosity, substantially exceeding design values. Work is presently underway to achieve the Enhanced Design parameters in about 2008. Planned major upgrades include the Electron Beam Ion Source (EBIS), the RHIC-II electron cooling upgrade, and construction of an electron-ion collider (eRHIC). We review the expected RHIC upgrade performance. Electron cooling and its impact on the luminosity at various collision energies both for heavy ions and protons are discussed in detail.

 
slides icon Slides  
TUPAS103 RHIC Challenges for Low Energy Operations 1877
 
  • T. Satogata, L. Ahrens, M. Bai, J. M. Brennan, D. Bruno, J. J. Butler, K. A. Drees, A. V. Fedotov, W. Fischer, M. Harvey, T. Hayes, W. Jappe, R. C. Lee, W. W. MacKay, G. J. Marr, R. J. Michnoff, B. Oerter, E. Pozdeyev, T. Roser, F. Severino, K. Smith, S. Tepikian, N. Tsoupas
    BNL, Upton, Long Island, New York
 
  Funding: Work supported by U. S. DOE under contract No DE-AC02-98CH1-886

There is significant interest in RHIC heavy ion collisions at c.m. energies of 5-50 GeV/u, motivated by a search for the QCD phase transition critical point. The low end of this energy range is well below the nominal RHIC injection c.m. energy of 19.6 GeV/u. There are several challenges that face RHIC operations in this regime, including longitudinal acceptance, magnet field quality, lattice control, and luminosity monitoring. We report on the status of work to address these challenges and include results from beam tests of low-energy RHIC operations with protons and gold.

 
WEOCKI03 Status of the R&D Towards Electron Cooling of RHIC 1938
 
  • I. Ben-Zvi, J. Alduino, D. S. Barton, D. Beavis, M. Blaskiewicz, J. M. Brennan, A. Burrill, R. Calaga, P. Cameron, X. Chang, K. A. Drees, A. V. Fedotov, W. Fischer, G. Ganetis, D. M. Gassner, J. G. Grimes, H. Hahn, L. R. Hammons, A. Hershcovitch, H.-C. Hseuh, D. Kayran, J. Kewisch, R. F. Lambiase, D. L. Lederle, V. Litvinenko, C. Longo, W. W. MacKay, G. J. Mahler, G. T. McIntyre, W. Meng, B. Oerter, C. Pai, G. Parzen, D. Pate, D. Phillips, S. R. Plate, E. Pozdeyev, T. Rao, J. Reich, T. Roser, A. G. Ruggiero, T. Russo, C. Schultheiss, Z. Segalov, J. Smedley, K. Smith, T. Tallerico, S. Tepikian, R. Than, R. J. Todd, D. Trbojevic, J. E. Tuozzolo, P. Wanderer, G. Wang, D. Weiss, Q. Wu, K. Yip, A. Zaltsman
    BNL, Upton, Long Island, New York
  • D. T. Abell, G. I. Bell, D. L. Bruhwiler, R. Busby, J. R. Cary, D. A. Dimitrov, P. Messmer, V. H. Ranjbar, D. S. Smithe, A. V. Sobol, P. Stoltz
    Tech-X, Boulder, Colorado
  • A. V. Aleksandrov, D. L. Douglas, Y. W. Kang
    ORNL, Oak Ridge, Tennessee
  • H. Bluem, M. D. Cole, A. J. Favale, D. Holmes, J. Rathke, T. Schultheiss, J. J. Sredniawski, A. M.M. Todd
    AES, Princeton, New Jersey
  • A. V. Burov, S. Nagaitsev, L. R. Prost
    Fermilab, Batavia, Illinois
  • Y. S. Derbenev, P. Kneisel, J. Mammosser, H. L. Phillips, J. P. Preble, C. E. Reece, R. A. Rimmer, J. Saunders, M. Stirbet, H. Wang
    Jefferson Lab, Newport News, Virginia
  • V. V. Parkhomchuk, V. B. Reva
    BINP SB RAS, Novosibirsk
  • A. O. Sidorin, A. V. Smirnov
    JINR, Dubna, Moscow Region
 
  Funding: Work done under the auspices of the US DOE with support from the US DOD.

The physics interest in a luminosity upgrade of RHIC requires the development of a cooling-frontier facility. Detailed cooling calculations have been made to determine the efficacy of electron cooling of the stored RHIC beams. This has been followed by beam dynamics simulations to establish the feasibility of creating the necessary electron beam. Electron cooling of RHIC at collisions requires electron beam energy up to about 54 MeV at an average current of between 50 to 100 mA and a particularly bright electron beam. The accelerator chosen to generate this electron beam is a superconducting Energy Recovery Linac (ERL) with a superconducting RF gun with a laser-photocathode. An intensive experimental R&D program engages the various elements of the accelerator: Photocathodes of novel design, superconducting RF electron gun of a particularly high current and low emittance, a very high-current ERL cavity and a demonstration ERL using these components.

 
slides icon Slides  
THPAS017 Numerical Algorithms for Modeling Electron Cooling in the Presence of External Fields 3549
 
  • G. I. Bell, D. L. Bruhwiler, A. V. Sobol
    Tech-X, Boulder, Colorado
  • I. Ben-Zvi, A. V. Fedotov, V. Litvinenko
    BNL, Upton, Long Island, New York
 
  Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-FG02-04ER84094.

The design of the high-energy cooler for the Relativistic Heavy Ion Collider (RHIC) recently adopted a non-magnetized approach. To prevent recombination between the fully stripped gold ions and co-propagating electrons, a helical undulator magnet has been proposed. In addition, to counteract space-charge defocusing, weak solenoids are proposed every 10m. To understand the effect of these magnets on the cooling rate, numerical models of cooling in the presence of external fields are needed. We present an approach from first principles using the VORPAL parallel simulation code. We solve the n-body problem by exact calculation of pair-wise collisions. Simulations of the proposed RHIC cooler are discussed, including fringe field and finite interaction time effects.

 
THPAS092 Electron Cooling in the Presence of Undulator Fields 3696
 
  • A. V. Fedotov, I. Ben-Zvi, D. Kayran, V. Litvinenko, E. Pozdeyev
    BNL, Upton, Long Island, New York
  • G. I. Bell, D. L. Bruhwiler, A. V. Sobol
    Tech-X, Boulder, Colorado
  • A. O. Sidorin, A. V. Smirnov
    JINR, Dubna, Moscow Region
 
  Funding: Work supported by the U. S. Department of Energy.

The traditional electron cooling system used in low-energy coolers employs an electron beam immersed in a longitudinal magnetic field. In the first relativistic cooler, which was recently commissioned at Fermilab, the friction force is dominated by the non-magnetized collisions between electrons and antiprotons. The design of the higher-energy cooler for Relativistic Heavy Ion Collider (RHIC) recently adopted a non-magnetized approach which requires a low temperature electron beam. However, to avoid significant loss of heavy ions due to recombination with electrons in the cooling section, the temperature of the electron beam should be very high. These two contradictory requirements are satisfied in the design of the RHIC cooler with the help of the undulator fields. The model of the friction force in the presence of an undulator field was benchmarked vs direct numerical simulations with an excellent agreement. Simulations of ion beam dynamics in the presence of such a cooler and helical undulator is discussed in detail, including recombination suppression and resulting luminosities.

 
THPAS093 High-Energy Electron Cooling Based on Realistic Six-Dimensional Distribution of Electrons 3699
 
  • A. V. Fedotov, I. Ben-Zvi, D. Kayran, E. Pozdeyev
    BNL, Upton, Long Island, New York
  • A. O. Sidorin, A. V. Smirnov
    JINR, Dubna, Moscow Region
 
  Funding: Work supported by the U. S. Department of Energy.

The low-energy electron cooling system is based on an electron beam immersed in a longitudinal magnetic field of a solenoid. The coupling of the horizontal and vertical motion allows representation of the friction force as a sum of the transverse and longitudinal components. The analytic treatment proceeds by allowing several approximations, for example, uniform transverse density distribution of electron beam and Maxwellian distribution in the velocity space. The high-energy electron cooling system for RHIC is unique compared to standard coolers. It requires bunched electron beam. Electron bunches are produced by an Energy Recovery Linac (ERL), and cooling is planned without a longitudinal magnetic field. To address the unique features of the RHIC cooler, a generalized 3-D treatment of the cooling force was introduced in the BETACOOL code which allows to calculate the friction force from an arbitrary six-dimensional distribution of the electrons. Results based on this treatment are compared to typical approximations. Simulations for the RHIC cooler based on a realistic electron distribution from the ERL are presented.

 
THPAS100 Collective Effects in the RHIC-II Electron Cooler 3717
 
  • E. Pozdeyev, I. Ben-Zvi, A. V. Fedotov, D. Kayran, V. Litvinenko, G. Wang
    BNL, Upton, Long Island, New York
 
  Funding: Work supported by U. S. DOE under contract No DE-AC02-98CH1-886

Electron cooling at RHIC-II upgrade imposes strict requirements on the quality of the electron beam at the cooling section. Beam current dependent effects such as the space charge, wake fields, CSR in bending magnets, trapped ions, etc., will tend to spoil the beam quality and decrease the cooling efficiency. In this paper, we estimate the defocusing effect of the space charge at the cooling section and describe our plan to compensate the defocusing space charge force by focusing solenoids. We also estimate the energy spread and emittance growth cased by wake fields. Finally, we discuss ion trapping in the electron cooler and consider different techniques to minimize the effect of ion trapping.