Thin Quartz Cerenkov DetectorR&D
Dustin McNultyIdaho State University
Thanks to: Carlos Bula, Brady Lowe
May 20, 2014
REU Summer 2014 Idaho State University'
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Ongoing Work at ISU for PREx and CREx
Quartz Cerenkov detector development• Cosmic ray tests
–Constructed baseline prototype detector–Constructed cosmic/beam test stand–Established counting Data Acquisition System (DAQ)
• Optical Monte Carlo Simulation–Using “qsim” framework: GEANT4, C++ based–Modeled precise geometry of cosmic test setup–Continuing to develop and refine.–Once benchmarked, will use to optimize detector design
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What is the size of a 208Pb nucleus (82p+126n)?
• What do we mean by size? The mass radius, the charge radius?
• PREx (Pb Radius Experiment) addresses this question in aunique way: Uses a “Weak” nuclear force probe to measure howmuch neutrons stick out past protons (The Neutron “skin”)
• CREx (Calcium Radius Experiment) performs samemeasurement but on 48Ca nucleus
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Fundamental Forces and the Standard Model
• Electromagnetism: Force mediated by γ exchange; Protonshave EM charge “+e” while neutrons have 0...
• Weak Nuclear: Force mediated by Z0 and W±; Neutrons have12 times more Qweak than protons
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PREx Measurement (Parity Violation)
• Uses ∼1 GeV elastically scattered electrons off 0.5 mm thickisotopically pure 208Pb target
• e− beam is longitudinally spin-polarized, target is unpolarized
• Measurement relies on the maximal parity-symmetry violatingnature of the Weak force
• e−’s dominant interaction is EM, but it can also interact viathe Weak force; but it only does so for one of the polarizationstates and not the other
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Jefferson Lab (Newport News, Virginia)
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Experimental Setup (Spectrometer & Detectors)
Target
Septum Q1 Q2
Dipole
Q3
VDCs
Quartz
Elastic
Inelastic
PREX Optics Schematic
• Thin quartz Cerenkov detectors with PMTs used to measurescattered electron flux
• Highly relativistic electrons travel faster than light travels throughthe quartz, thus creating Cerenkov radiation (UV light)
• High purity quartz necessary due to its extreme radiation hardness(maintains transparency during high doses of radiation)
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Baseline prototype Quartz Detector
• SolidWorks CAD based on PREX design• Quartz: Spectrosil 2000, 14×3.5×1.0(0.6) cm3, 45o
bevel on one end, optical polish all sides• Light guide: Anolux Miro-silver 4270AG, ...
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Baseline prototype Quartz Detector
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Cosmic Rays
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Cosmic/Beam Test Stand
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Initial Cosmic Test Results
Entries 1062
Mean 245
RMS 94.97
/ ndf 2χ 42.35 / 50
Lwidth 1.38± 14.63
MPV 1.7± 195.9
Integral 3.328e+02± 1.043e+04 GSigma 2.16± 26.09
ADC channel0 0.2 0.4 0.6 0.8 1
310×
Eve
nts
/10c
h
0
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50
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90Entries 1062
Mean 245
RMS 94.97
/ ndf 2χ 42.35 / 50
Lwidth 1.38± 14.63
MPV 1.7± 195.9
Integral 3.328e+02± 1.043e+04 GSigma 2.16± 26.09
= 0.388MeanRMS
= 0.133MPV
Gsigma
Quartz Proto-1 ADC LanGau Fit, run 243
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G4 Optical Simulation: qsim
• qsim framework developed by Seamus Riordan
• Geometry adapted to ISU cosmic test setup
• Additional realistic features implemented: muon anglesmearing, PMT QE, scintillator coinc. trigger
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Distribution of Photons/Muon Hitting PMT
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Comparison between Simulation and Experiment
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Summary and Plans
• Continued cosmic ray testing of baseline prototype
• Continued refinement of optical simulation by Carlos Bula
• New prototype design currently being developed by BradyLowe
• Plans to construct new prototype and test with cosmics nextmonth
• Planning for Late summer/early fall quartz detector beamtestat ISU using 12MeV HRRL electron beam
More info can be found at http://www.isu.edu/∼mcnudust
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