Author: Evans, N.J.
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Foil R&D and Temperature Measurements at the SNS  
  • N.J. Evans
    ORNL RAD, Oak Ridge, Tennessee, USA
  The SNS uses charge exchange injection during the accumulation of the accelerated beam in the ring. At a beam power of 1.2 MW, the stripping foil lasts for many weeks, sometimes months. However, given the upgrade to 2.8 MW, it is important to know the current temperature of the foil in order to estimate its lifetime for the new beam power and beam size. This paper will discuss the foil R&D and experimental temperature measurements of a stripper foil, exposed to current operating conditions of the SNS accelerator.  
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Characterization and Analysis of Nanocrystalline Diamond as Stripper Foils  
  • L.V. Saturday, P.D. Rack
    University of Tennessee, Knoxville, USA
  • D.P. Briggs, P.D. Rack, S.T. Retterer
    CNMS, Oak Ridge, USA
  • N.J. Evans, C.F. Luck
    ORNL RAD, Oak Ridge, Tennessee, USA
  • L.L. Wilson
    ORNL, Oak Ridge, Tennessee, USA
  Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.
The 1.4 MW Spallation Neutron Source (SNS) uses nanocrystalline diamond (NCD) foils to strip 1 GeV H ions to protons during injection into the accumulator ring. The SNS Proton Power Upgrade will double the power deposited into the NCD foils by increasing the beam current by 50% and linac energy by 30%. This makes understanding the failure modes of the NCD foils increasingly important. In this work we report on experiments using a 30 keV, 5 mA electron gun capable of simulating SNS PPU time structure and energy deposition in NCD foils. We analyze changes to the foil with an RGA, FLIR camera, faraday cup, high definition photography, SEM, and Raman spectroscopy. We examine failure mechanisms for foils subjected to equivalent PPU conditions. Preliminary results have shown characteristic signs of foil thinning and different failure mechanisms between the electron gun and SNS beam line. Additionally, membrane cantilever structures have been synthesized and characterized to understand the material properties of the NCD. Finally, finite element thermal simulations of the suspended diamond foils have been performed, which will be used to assess and direct future foil modifications.
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