ATLAS Tile Calorimeter: ITC Scintillator Tests
 
Responsible institutions:  Michigan State University
Responsible persons     :  R. Miller

Inter-Cryostat Scintillators

Tests of light collection were made using prototype scintillators with the dimensions of the innermost cell in the inter-cryostat position -6 mm thick x 365 mm long x 172 mm outer end x 136 mm inner end. The light was collected using 1 mm WLS fibers (Kuraray Y11), mirrored on one end. Half of the fibers were routed to one PMT, and half to another PMT. Another pair of scintillators above and below the test piece were used to trigger on cosmic muons. The signals from the PMT's were readout via ADC's. The figures below show the raw Pulse Height spectra and the distribution of sums and differences after pedestal subtraction and rescaling PMT2 to the same average as PMT1. We assume that the spectra are the sum of gaussian distributions corresponding to 1 photo-electron (pe), 2 pe, 3 pe,... n pe, etc., with weights given by a Poisson distribution of mean = {n}, and sigma = sqrt({n}). Then {n} is extracted from the sum and difference spectra: {n} = [mean(PMT1+PMT2)/sigma(PMT1-PMT2)]^2 Two configurations were tried: 1. WLS fiber along both sides
  • 6 fibers/side (ps)
  • 5 fibers/side (ps)
  • 4 fibers/side (ps)
  • 3 fibers/side (ps)
  • 2 fibers/side (ps)
  • 1 fibers/side (ps)
  • Uniformity scan (ps)
    • 2. Splitting the scintillator down the middle and putting WLS fiber between the pieces.
  • 6 fibers in the middle (ps)
  • 5 fibers in the middle (ps)
  • 4 fibers in the middle (ps)
  • 3 fibers in the middle (ps)
  • 2 fibers in the middle (ps)
  • Uniformity scan (ps)
    • The results are summarized in the following plot.
  • Light Yield vs number of fibers (ps)
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