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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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