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Deibele, C.

Paper Title Page
MOPAS050 Active Damping of the e-p Instability at the LANL PSR 548
 
  • R. C. McCrady, R. J. Macek, S. B. Walbridge, T. Zaugg
    LANL, Los Alamos, New Mexico
  • S. Assadi, C. Deibele, S. Henderson, M. A. Plum
    ORNL, Oak Ridge, Tennessee
  • J. M. Byrd
    LBNL, Berkeley, California
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  • M. T.F. Pivi
    SLAC, Menlo Park, California
 
  Funding: This work was supported by the United States Department of Energy under contracts DE-AC52-06NA25396 and W-7405-ENG-36.

A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos National Laboratory Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). Evidence obtained from these tests suggests that further improvement in performance is limited by beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizontal plane, which had no feedback. Here we describe the present system configuration, system optimization, results of several recent experimental tests, and results from studies of factors limiting its performance.

 
MOPAS080 A Digital Ring Transverse Feedback Low-Level RF Control System 617
 
  • A. K. Polisetti, S. Assadi, C. Deibele, J. C. Patterson
    ORNL, Oak Ridge, Tennessee
  • R. C. McCrady
    LANL, Los Alamos, New Mexico
  • M. J. Schulte
    UW-Madison, Madison, Wisconsin
 
  A digital wide-band system for damping ring instabilities in an accelerator is presented. With increased beam intensity, the losses of an accumulator ring tend to increase due to the onset of various instabilities in the beam. An analog feedback damper system has been implemented at Los Alamos National Laboratory. This analog system, while functional, has certain limitations and a lack of programmability, which can be overcome by a digital solution. A digital feedback damper system is being designed through a collaborative effort by researchers at Oakridge National Laboratory, Los Alamos National Laboratory, and the University of Wisconsin. This system, which includes analog-to-digital converters, field programmable gate arrays and digital-to-analog converters can equalize errors inherent to analog systems, such as dispersion due to amplifiers/cables, gain mismatches, and timing adjustments. The digital system features programmable gains and delays, and programmable equalizers that are implemented using digital FIR and comb filters. The flexibility of the digital system allows it to be customized to implement different configurations and extended to address other diagnostic problems.  
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.

 
WEXC01 Experimental Tests of a Prototype System for Active Damping of the E-P Instability at the LANL PSR 1991
 
  • C. Deibele, S. Assadi, V. V. Danilov, S. Henderson, M. A. Plum, A. K. Polisetti
    ORNL, Oak Ridge, Tennessee
  • J. M. Byrd
    LBNL, Berkeley, California
  • J. D. Gilpatrick, R. C. McCrady, J. F. Power, T. Zaugg
    LANL, Los Alamos, New Mexico
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  • M. T.F. Pivi
    SLAC, Menlo Park, California
  • M. J. Schulte, Z. P. Xie
    UW-Madison, Madison, Wisconsin
 
  Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract DE-AC05-00OR22725.

A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos Proton Storage Ring (PSR). This talk describes the system configuration, results of several experimental tests and studies of system optimization along with studies of the factors limiting its performance.

 
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WEPMS080 SRF Cavity Transient Beam Loading Detection - Simulation and Measurement 2517
 
  • Y. Zhang, I. E. Campisi, C. Deibele, J. Galambos, S. Henderson, Y. W. Kang, H. Ma, J. L. Wilson
    ORNL, Oak Ridge, Tennessee
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

Beam phase measurement based on detection of transient beam loading signal in a Superconducting (SC) cavity is utilized to setup the cavity synchronous phase. It has the potential to become a fast tune-up technique for a high intensity SC electron linac, as cavity phase could be determined precisely with only a few beam pulses. The paper introduces a transient detector study in the Spallation Neutron Source (SNS) proton linac, and discusses one of the major challenges - stochastic noise in the cavity RF system, which deteriorates the precision and increases the time needed for phase measurement with this technique. We analyze the influence of RF noise to the phase measurement in a simulation study with a beam-cavity model. Beam signal measurement with the cavity Low Level RF (LLRF) system and the initial experiment of prototype detectors are briefly introduced.

 
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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