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Calibration of MUSE Scattered Particle ScintillatorsOctober 4, 2019Anne Flannery
This work is supported in parts by NSF PHY-1614773
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A. Flannery - Calibration of MUSE scattered-particle scintillators
Outline
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Introduction to Muse
SPS Detectors Overview
Calibration of SPS
Concluding Statement
A. Flannery - Calibration of MUSE scattered-particle scintillators
What is the radius of the proton?
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Mesick, Katherine. (2015). The MUSE Experiment: Studying the Proton Radius Puzzle with muon-proton Elastic Scattering. 091. DOI: 10.22323/1.226.0091.
Introduction to Muse
A. Flannery - Calibration of MUSE scattered-particle scintillators
MUon Proton Scattering experiment
Muse Setup
• an experiment which attempts to address the proton radius puzzle through muon-proton and electron-proton scattering measurements in the same experiment
Target
STT
SPS Walls
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220 cm
Electron, muon beam
Momentum 115, 160, 210 MeV/c
Introduction to Muse
A. Flannery - Calibration of MUSE scattered-particle scintillators
Path of the scattered particle
The SPS bars are fast timing detectors for the experiment
STT University of Jerusalem
SPS Walls University of South Carolina
Target University of Michigan
Beam
Scattered-Particle Scintillators (SPS)
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SPS Detectors Overview
A. Flannery - Calibration of MUSE scattered-particle scintillators
How does a scintillator work?
• A charged particle passing through the bar deposits a certain amount of energy (minimum 2 MeVg-1cm2), causing photon emission.
• A photodectector receives a signal whose strength is determined by the amount of energy deposited.
• The photodetector sends this signal to a charge to digital converter (QDC).
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SPS Detectors Overview
Scintillator
Photodetector
Photodetector
QDC
Beam
A. Flannery - Calibration of MUSE scattered-particle scintillators
Where does the signal go, and what does it mean?
• A Na-22 source is used instead of the beam in order to calibrate SPS bars.
Na-22 Decay scheme7
Calibration of SPS
Na-22
511 keV 511 keV
1275 keV
A. Flannery - Calibration of MUSE scattered-particle scintillators
Three kinds of light-matter interaction
http://electrons.wikidot.com/pair-production-and-annihilation
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• Photoelectric effect (lowest energy)
• Compton scattering (medium energy)
• Pair-production (highest energy)
We use Compton scattering for the calibration method
discussed here
Calibration of SPS
Unlikely
Unlikely for 1275 KeV, and impossible for 511 KeV
A. Flannery - Calibration of MUSE scattered-particle scintillators
0 100 200Pulse Height (MQDC Channels)
0
500
1000
1500
Cou
nts
run701_BM00uData (z = 20 cm)Simulation (fit stat. 5)c = 17.8 keV/Channel
= 7.2 %α = 4.8 %β
Example Na-22 QDC Distribution
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Calibration of SPS
1062 keV0 keV 511 keV
A. Flannery - Calibration of MUSE scattered-particle scintillators
Na-22 Calibration for the SPS Bars
• A Na-22 source was placed at varying heights along the bar, in 20cm increments. Since the PMTs were on both the top and bottom of the bar, signal strength lowered as Na-22 source became further from either the up or the down PMT.
Closer Na-22 sourceFurther Na-22 Source
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Calibration of SPS
A. Flannery - Calibration of MUSE scattered-particle scintillators
Concluding Statement
• Future calibration methods will include room background source, especially focusing on the Compton edge for Thallium 208, which is ever-present for all bars. The following graph shows a QDC histogram which is already pedestal subtracted.
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Concluding Statement
0 200 400QDC geom. mean (Channel)
0
200
400
600
Cou
nts
mqdc_geom_single_SPSLR00
Th-208 Compton Edge
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