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Aleksandrov, A. V.

Paper Title Page
TUOCC01 Software Tools for Commissioning of the Spallation Neutron Source Linac 883
  • J. Galambos, A. V. Aleksandrov, C. K. Allen, S. Henderson, T. A. Pelaia, A. P. Shishlo, Y. Zhang
    ORNL, Oak Ridge, Tennessee
  • P. Chu
    SLAC, Menlo Park, California
  Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract DE-AC05-00OR22725.

The Accelerator Physics group at the Spallation Neutron Source (SNS) has developed numerous codes to assist in the beam commissioning, tuning, and operation of the SNS Linac. These codes have been key to meeting the beam commissioning milestones. For example, a recently developed code provides for rapid retuning of the superconducting Linac in case of RF stations going offline or coming online. Highlights of these "physics applications" will be presented.

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TUPAS073 New Design of the SNS MEBT Chopper Deflector 1817
  • A. V. Aleksandrov, C. Deibele
    ORNL, Oak Ridge, Tennessee
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

The chopper system for the Spallation Neutron Source (SNS) provides a gap in the beam for clean extraction from the accumulator ring. It consists of a pre-chopper in the low energy beam transport and a faster chopper in the medium energy beam transport (MEBT). The original "meander line" design of the MEBT chopper deflector was successfully tested with low power beam during the SNS linac commissioning but turned out to be unsuitable for high power beam operation due to poor cooling of the copper strip line through the dielectric substrate. We developed a new deflecting structure, with higher deflection efficiency and with rise and fall time easily customizable to match the available high voltage pulse generator. In this paper we describe design, implementation and beam tests results of the new MEBT chopper deflector.

TUPAS074 Performance of the SNS Front End and Linac 1820
  • A. V. Aleksandrov, S. Assadi, W. Blokland, P. Chu, S. M. Cousineau, V. V. Danilov, C. Deibele, J. Galambos, S. Henderson, D.-O. Jeon, M. A. Plum, A. P. Shishlo, M. P. Stockli, Y. Zhang
    ORNL, Oak Ridge, Tennessee
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H- injector, capable of producing one-ms-long pulses at 60 Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The 2.5 MeV beam from the Front End is accelerated to 86 MeV in the Drift Tube Linac, then to 185 MeV in a Coupled-Cavity Linac and finally to 1 GeV in the Superconducting Linac. With the completion of beam commissioning, the accelerator complex began operation in June 2006 and beam power is being gradually ramped up toward the design goal. Operational experience with the injector and linac will be presented including chopper performance, transverse emittance evolution along the linac, and the results of a beam loss study.

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.

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WEPMS074 Design and High Power Processing of RFQ Input Power Couplers 2505
  • Y. W. Kang, A. V. Aleksandrov, D. E. Anderson, M. S. Champion, M. T. Crofford, P. E. Gibson, T. W. Hardek, P. Ladd, M. P. McCarthy, D. Stout, A. V. Vassioutchenko
    ORNL, Oak Ridge, Tennessee
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

A RF power coupling system has been developed for future upgrade of input coupling of the RFQ in the SNS linac. The design employs two coaxial loop couplers for 402.5 MHz operation. Each loop is fed through a coaxial ceramic window that is connected to an output of a magic-T waveguide hybrid through a coaxial to waveguide transition. The coaxial loop couplers are designed, manufactured, and high power processed. Two couplers will be used in parallel to power the accelerating structure with up to total 800 kW peak power at 8% duty cycle. RF and mechanical properties of the couplers are discussed. Result of high power RF conditioning that is performed in the RF test facility of the SNS is presented.

THYKI02 Laser Stripping of H- beams: Theory and Experiments 2582
  • V. V. Danilov, A. V. Aleksandrov, S. Assadi, W. Blokland, S. M. Cousineau, C. Deibele, W. P. Grice, S. Henderson, J. A. Holmes, Y. Liu, M. A. Plum, A. P. Shishlo, A. Webster
    ORNL, Oak Ridge, Tennessee
  • I. Nesterenko
    BINP SB RAS, Novosibirsk
  • L. Waxer
    LJW, Saint Louis
  Funding: Research sponsored by LDRD Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy under Contract No. DE-AC05-00OR22725.

Thin carbon foils are used as strippers for charge exchange injection into high intensity proton rings. However, the stripping foils become radioactive and produce uncontrolled beam loss, which is one of the main factors limiting beam power in high intensity proton rings. Recently, we presented a scheme for laser stripping an H- beam for the Spallation Neutron Source ring. First, H- atoms are converted to H0 by a magnetic field, then H0 atoms are excited from the ground state to the upper levels by a laser, and the excited states are converted to protons by a magnetic field. In this paper we report on the first successful proof-of-principle demonstration of this scheme to give high efficiency (around 90%) conversion of H- beam into protons at SNS in Oak Ridge. The experimental setup is described, and comparison of the experimental data with simulations is presented. In addition, future plans on building a practical laser stripping device are discussed.

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THOAAB01 Longitudinal Beam Parameters Study in the SNS Linac 2608
  • A. Feschenko, L. V. Kravchuk, A. A. Menshov
    RAS/INR, Moscow
  • A. V. Aleksandrov, S. Assadi, J. Galambos, S. Henderson
    ORNL, Oak Ridge, Tennessee
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

SNS Linac utilizes several accelerating structures operating at two frequencies. CCL and SCL operate at 805 MHz while 402.5 MHz is used for RFQ and DTL. Beam transfer from the previous part of the accelerator to the subsequent one requires careful longitudinal matching to improve beam transmission and to minimize beam losses. Longitudinal beam parameters have been investigated with the help of three Bunch Shape Monitors installed in the intersegments of the first CCL Module. The results of bunch shape observations for different accelerator settings are presented. Longitudinal beam emittance has been measured and optimized. Longitudinal beam halo has been evaluated as well.

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