Thin Quartz Cerenkov DetectorR&D

Dustin McNultyIdaho State University

mcnudust@isu.edu

Thanks to: Carlos Bula, Brady Lowe

May 20, 2014

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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

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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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