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1
Spallation Neutron
A Study of Time Variation of Detector Uniformity
Kevin Chen4/9/15
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Muons creates spallation neutrons Neutrons captured by Gd targets, mean capture
time ~30s
Sp. n + Gd = ~8MeV photons
Find muon events by setting charge threshold (>10 000p.e.)
Take all events within 1ms of muon EH1-AD1 results with P14A dataset
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nGd capture
Exponential +Background fit
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z: -1.5 to 1.5m
r^2: 0 to 2.25m^2
Energy Distribution for Different Regions
Tails on edge of detector
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Before Uniformity Correction Dec '12 After Uniformity Correction
Nov '14
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Observed +/- 0.3% variation of detector uniformity over 2 years
Mean energy of outer regions increases over time, vice versa for inner regions
Percent Change from Dec '12 to Nov '14
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Next Steps:
Characterize trend of energy uniformity variation between Dec '12 and Nov '14
Repeat for all detectors Evaluate effect on 6MeV cut due to the
change in detector uniformity
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