Author: Aleksandrov, A.V.
Paper Title Page
MO2A02 Increased Understanding of Beam Losses from the SNS Linac Proton Experiment 115
  • J. Galambos, A.V. Aleksandrov, M.A. Plum, A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  • E. Laface
    ESS, Lund, Sweden
  • V.A. Lebedev
    Fermilab, Batavia, USA
  The SNS Linac has been in operation for 6 years, with its power being gradually increased. A major operation goal is the decrease of beam loss. It has been recently suggested that intra- H–beam stripping contributes significantly to beam losses in an H linac. This was tested experimentally at SNS by accelerating a proton beam. Experimental analysis results are in good agreement with the theoretical estimates. In this paper we present the operational status and experience at the SNS linac, with emphasis on understanding beam loss in terms of intra-H–beam stripping.  
slides icon Slides MO2A02 [12.869 MB]  
THPB012 High Resolution Emittance Measurements at SNS Front End 870
  • A.P. Zhukov, A.V. Aleksandrov
    ORNL, Oak Ridge, Tennessee, USA
  Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
Spallation Neutron Source (SNS) linac accelerates an H beam from 2.5MeV up to 1GeV. Recently the emittance scanner in the MEBT (2.5 MeV) was upgraded. In addition to the slit - harp measurement we now can use a slit installed on the same actuator as the harp. In combination with a faraday cup located downstream in DTL part of the linac it represents a classical slit-slit emittance measurement device. While a slit – slit scan takes much longer time, it is immune to harp related problems such as wire cross talk and thus looks promising for accurate halo measurements. Time resolution of the new device seems to be sufficient to estimate amount of the beam in the chopper gap (the scanner is downstream of the chopper) and probably measure its emittance. The paper describes initial measurements with new device and some model validation data.
THPB013 Diagnostics Tools for Beam Halo Investigation in SNS Linac 873
  • A.V. Aleksandrov, W. Blokland, Y. Liu, C.D. Long, A.P. Zhukov
    ORNL, Oak Ridge, Tennessee, USA
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
Uncontrolled beam loss is the major concern in operation of a high intensity hadron linac. A low density cloud of particles with large oscillation amplitudes, so called halo, can form around the dense regular beam core. This halo can be direct or indirect cause of beam loss. There is an experimental evidence of halo growing in SNS linac and limiting further reduction of beam loss. A set of tools is being developed for detecting of the halo and investigating its origin and dynamics. The set includes high resolution emittance measurements in the injector, laser based emittance measurements at 1 GeV, and high resolution profile measurements along the linac. We will present our experience with useful measurement techniques and data analysis algorithms as well as current understanding of the halo dynamics in SNS linac.
THPB044 Plans for an Integrated Front-End Test Stand at the Spallation Neutron Source 954
  • M.S. Champion, A.V. Aleksandrov, M.T. Crofford, D. Heidenreich, Y.W. Kang, J. Moss, R.T. Roseberry, J.P. Schubert
    ORNL, Oak Ridge, Tennessee, USA
  Funding: Work performed at Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
A spare Radio-Frequency Quadrupole (RFQ) is presently being fabricated by industry with delivery to Oak Ridge National Laboratory planned in late 2012. The establishment of a test stand at the Spallation Neutron Source site is underway so that complete acceptance testing can be performed during the winter of 2012-2013. This activity is the first step in the establishment of an integrated front-end test stand that will include an ion source, low-energy beam transport (LEBT), RFQ, medium-energy beam transport, diagnostics, and a beam dump. The test stand will be capable of delivering an H ion beam of up to 50 mA with a pulse length of 1 ms and a repetition rate of 60 Hz or a proton beam of up to 50 mA, 100 μs, 1 Hz. The test stand will enable the following activities: complete ion source characterization; development of a magnetic LEBT chopper; development of a two-source layout; development of beam diagnostics; and study of beam dynamics of high intensity beam.