Measurement Of Neutron Radius In Lead By Parity Violating Scattering Flash ADC DAQ

144 Pages·2015·3.53 MB·English

by  Ahmed Zafar

Syracuse University
SURFACE
Physics - Dissertations College of Arts and Sciences
6-2012
Measurement Of Neutron Radius In Lead By
Parity Violating Scattering Flash ADC DAQ
Ahmed Zafar
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Recommended Citation
Zafar, Ahmed, "Measurement Of Neutron Radius In Lead By Parity Violating Scattering Flash ADC DAQ" (2012).Physics -
Dissertations.Paper 120.
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ABSTRACT
This dissertation reports the experiment PREx, a parity violation experiment
which is designed to measure the neutron radius in 208Pb. PREx is performed in
hall A of Thomas Jefferson National Accelerator Facility from March 19th to June
21st. Longitudionally polarized electrons at energy 1 GeV scattered at and agnle
of θ = 5.8◦ from the Lead target. Beam corrected pairty violaing counting rate
lab
asymmetry is (A = 594 50(stat) 9(syst))ppb at Q2 = 0.009068GeV2.
corr
± ±
ThisdissertationalsopresentsthedetailsofFlashADCDataAcquisition(FADC
DAQ) system for Moller polarimetry in Hall A of Thomas Jefferson National Ac-
celerator Facility. The Moller polarimeter measures the beam polarization to high
precision to meet the specification of the PREx(Lead radius experiment). The
FADC DAQ is part of the upgrade of Moller polarimetery to reduce the systematic
error for PREx. The hardware setup and the results of the FADC DAQ analysis are
presented.
MEASUREMENT OF NEUTRON RADIUS IN LEAD BY PARITY
VIOLATING SCATTERING
Flash ADC DAQ
A Dissertation Presented to
The Faculty of the Department of Physics
of Syracuse University
In Partial Fulfillment
Of the Requirements for the Degree of
Doctor of Philosophy in Physics
by
Zafar Ahmed
June
2012
c Copyright by Zafar Ahmed 2012
(cid:13)
All Rights Reserved
Acknowledgements
I want to say thank you to Paul Souder, Robert Michaels, Richard Holmes, Brad
Swatzky, Sasha Glamazdin, Roman Pomatsalyuk, Eugene Chudakov, Kent Peskhe,
Krishna Kumar, Dustin Mcnulty, Bryan Moffit, Mark Dalton, Jon Musson and hall
A colleboration.
I also want to acknowledge all of my undergraduate, diploma and graduate
teachers.
iv
Dedicated to:
Professor Abdus Salam
v
TABLE OF CONTENTS
Page
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii
CHAPTER
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Weak Interaction and Parity Violation . . . . . . . . . . . . . . . 2
1.2 Neutron Skin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Weak Neutral Current . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 Parity Violating Asymmetry . . . . . . . . . . . . . . . . . . . . . 4
1.5 Neutron Density and Parity Violation . . . . . . . . . . . . . . . . 6
1.6 Analyzing Power . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.7 Uncertainties to Parity Violating Asymmetry . . . . . . . . . . . . 11
1.7.1 Coulomb Distortions . . . . . . . . . . . . . . . . . . . . . 11
1.7.2 Strangeness Correction . . . . . . . . . . . . . . . . . . . . 14
1.7.3 Inelastic Scattering . . . . . . . . . . . . . . . . . . . . . . 15
1.7.4 Parity Admixture . . . . . . . . . . . . . . . . . . . . . . . 17
1.7.5 Meson Exchange Current . . . . . . . . . . . . . . . . . . . 17
1.7.6 Dispersion correction . . . . . . . . . . . . . . . . . . . . . 17
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1.7.7 Surface Thickness . . . . . . . . . . . . . . . . . . . . . . . 17
1.7.8 Isospin Violation Correction . . . . . . . . . . . . . . . . . 18
1.7.9 Target Impurities . . . . . . . . . . . . . . . . . . . . . . . 18
1.8 Important Results of PREx . . . . . . . . . . . . . . . . . . . . . 18
1.8.1 Atomic Parity Non-Conservation . . . . . . . . . . . . . . 19
1.8.2 Nuclear Symmetry Energy . . . . . . . . . . . . . . . . . . 19
1.8.3 Neutron Density and Astro Physics . . . . . . . . . . . . . 20
1.9 Summary of Specific Responsibilities of the Author . . . . . . . . 20
2 Experimental Design . . . . . . . . . . . . . . . . . . . . . . . . 22
2.1 Accelerator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2 Polarized Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.1 Laser System . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2.2 Insertable Half Wave Plate . . . . . . . . . . . . . . . . . . 25
2.2.3 Pockels Cell and PITA effect . . . . . . . . . . . . . . . . . 25
2.2.4 Rotatable Half Wave Plate . . . . . . . . . . . . . . . . . . 28
2.2.5 Gal’s Cathode . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.3 Wien Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.4 Polarimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4.1 Mott Polarimeter . . . . . . . . . . . . . . . . . . . . . . . 35
2.4.2 Compton Polarimeter . . . . . . . . . . . . . . . . . . . . . 37
2.5 Beam Monitering . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.5.1 Strip Line Position Monitor . . . . . . . . . . . . . . . . . 40
2.5.2 Strip Line Current Monitor . . . . . . . . . . . . . . . . . 41
2.5.3 Cavity Monitors . . . . . . . . . . . . . . . . . . . . . . . . 41
2.5.4 Target and Beam Raster . . . . . . . . . . . . . . . . . . . 43
2.5.5 Beam Modulating . . . . . . . . . . . . . . . . . . . . . . . 47
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2.5.6 Luminosity Monitor . . . . . . . . . . . . . . . . . . . . . . 47
2.6 HRS and Septum Magnet . . . . . . . . . . . . . . . . . . . . . . 48
2.7 PREx Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3 Flash ADC DAQ and Analysis . . . . . . . . . . . . . . . . . . 53
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.2 Moller Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.3 Moller Polarimeter . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.3.1 Moller Target(Old) . . . . . . . . . . . . . . . . . . . . . . 58
3.3.2 Moller Spectrometer . . . . . . . . . . . . . . . . . . . . . 59
3.3.3 Moller Detector . . . . . . . . . . . . . . . . . . . . . . . . 60
3.4 Moller Polarimeter Upgrade . . . . . . . . . . . . . . . . . . . . . 61
3.4.1 New Moller Target . . . . . . . . . . . . . . . . . . . . . . 61
3.4.2 New Scintillators . . . . . . . . . . . . . . . . . . . . . . . 62
3.5 Flash ADC DAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.5.1 F-250 Flash ADC . . . . . . . . . . . . . . . . . . . . . . . 63
3.5.2 FADC Logical Signals for Moller . . . . . . . . . . . . . . . 65
3.5.3 FADC Data Acquiring Overview . . . . . . . . . . . . . . . 68
3.5.4 ROC, Flex IO and SD-FG Modules . . . . . . . . . . . . . 69
3.5.5 NIM Crate . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.5.6 FADC Data Events . . . . . . . . . . . . . . . . . . . . . . 70
3.5.7 Old DAQ and FADC Differences . . . . . . . . . . . . . . . 74
3.6 Moller Polarimeter Systematic Errors . . . . . . . . . . . . . . . . 77
3.6.1 LevChuk Effect . . . . . . . . . . . . . . . . . . . . . . . . 78
3.6.2 Targets Polarization Discrepancy . . . . . . . . . . . . . . 79
3.6.3 Target Saturation . . . . . . . . . . . . . . . . . . . . . . . 79
3.6.4 Analyzing Power . . . . . . . . . . . . . . . . . . . . . . . 80
viii
3.6.5 Target Temperature . . . . . . . . . . . . . . . . . . . . . . 82
3.7 FADC Analysis and Results . . . . . . . . . . . . . . . . . . . . . 83
3.7.1 Stability of FADC . . . . . . . . . . . . . . . . . . . . . . . 83
3.7.2 Spin Dance Result . . . . . . . . . . . . . . . . . . . . . . 84
3.7.3 Scaler and Data rate comparison . . . . . . . . . . . . . . 84
3.7.4 FADC and Old DAQ Delayed Time . . . . . . . . . . . . . 85
3.7.5 Data Triggers and Scalers Asymmetry . . . . . . . . . . . . 86
3.7.6 FADC and Old DAQ Raw Asymmetry . . . . . . . . . . . 86
4 PREx Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
4.2 Data Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
4.3 Counting Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
4.4 Integrating Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
4.5 Parity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4.6 Data Cuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
4.7 Raw Asymmetry . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
4.8 Passive Helicity Reversal . . . . . . . . . . . . . . . . . . . . . . . 96
4.9 Position Differences and Charge Asymmetry . . . . . . . . . . . . 96
4.10 Detector Pedestals . . . . . . . . . . . . . . . . . . . . . . . . . . 97
4.11 Linearity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
4.12 Dithering and Regression . . . . . . . . . . . . . . . . . . . . . . . 101
4.13 Carbon Background . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4.14 Transverse Asymmetry . . . . . . . . . . . . . . . . . . . . . . . . 105
4.15 Q2 Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
4.15.1 Beam Energy . . . . . . . . . . . . . . . . . . . . . . . . . 106
4.15.2 Target Coordinates . . . . . . . . . . . . . . . . . . . . . . 107
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