1. PREX / CREX Collaboration Meeting and Status
Oct 1 – 2, 2017
Report by Robert Michaels
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2. PREX and CREX Asymmetry is non-zero due to weak interaction.
208Pb
48Ca
PREX-I
PREX-II
CREX
PREX-I : PRL 108 (2012)
227 citations
Rn - Rp (fm)
Asymmetry is non-zero due to weak interaction.
Weak interaction “sees” neutrons (electromagnetic sees protons).
number of nucleons A
Neutron skin
Lead Nucleus
Can theory predict its size ? Rn Rp
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R. Michaels, Hall A Mtg, Oct 3, 2017

3. Engineering Progress -- Robin Wines
Skyshine shield
Target
Septum Magnet
collimator
HRS Quad 1
beam
Man-weeks design
24 Man-weeks engineering
(minus target)
Jessie Butler: ~70 days installation
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R. Michaels, Hall A Mtg, Oct 3, 2017

4. Target -- Silviu Covrig
Target group responsible
CFDFAC thermal calculations performed to understand and improve the design
port
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R. Michaels, Hall A Mtg, Oct 3, 2017

5. Radiation Simulation -- Ciprian Gal (UVa)
Shielding
Design
Target and Septum Region
HRS Q1
Skyshine shield
Skyshine shield
target
septum
plastic shield
HRS controls
New since ERR : Beam Dump being considered
(work in progress)
Beam dump
Need concrete shielding ?
R. Michaels, Hall A Mtg, Oct 3, 2017

6. Magnetic Shielding -- Jay Benesch
Confirmed that Al Gavalya’s shield design inside septum is good
Proposed a 3 mm thick conical carbon steel shield for HRS quad
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R. Michaels, Hall A Mtg, Oct 3, 2017

7. Integrating Detectors -- Dustin McNulty
Placed above the VDCs in HRS detector stack
Idaho State University
Quartz bar
PMT
Two (redundant) quartz bars, which intercept elastically scattered electrons.
We integrate this signal for our main signal.
Design similar to PREX-I. Beam tests at Mainz confirm simulation.
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R. Michaels, Hall A Mtg, Oct 3, 2017

8. GEMs -- Dustin McNulty Supplement the VDCs in HRS
Idaho State University
Supplement the VDCs in HRS
So we can do Q2 measurements at ~1 uA (rates high)
These are “small” 10 x 20 cm2
400 um pitch
Capitalizes on SBS developments (INFN / Uva)
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R. Michaels, Hall A Mtg, Oct 3, 2017

9. PREX/CREX Detectors -- Dustin McNulty
GEMs (3)
Quartz (2)
Quartz (2)
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R. Michaels, Hall A Mtg, Oct 3, 2017

10. “SAM” (Lumi monitor) -- Tao Ye
Stony Brook University
A source of extremely high rate  Establishes a “noise floor”
Corrections for beam noise are consistent with expected beam position monitor resolution.
BCM resolution 12 ppm
Result: SAM statistical level 60 ppm
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R. Michaels, Hall A Mtg, Oct 3, 2017

11. Other Topics at PREX/CREX Meeting Oct 1-2, 2017 at JLab
Software and Optics Seamus Riordan (Argonne) Ryan Richards (StonyBrook)
Detectors Tyler Kutz (StonyBrook)
Carlos Bula (Idaho St)
4K running Grigory Eremeev (Jlab)
Nonlinearities Devi Adhikari (Idaho St)
Moller Polarimeter Bill Henry (Temple)
Kerr Studies Fernando Araiza Gonzalez (StonyBrook)
Compton Polarimeter Juan Carlos Cornejo (CMU)
Polarized Source Joe Grames (Jlab)
Caryn Palatchi (Uva)
DAQ Status Bob Michaels (Jlab)
Scheduling Thia Keppel (Jlab)
Last page
R. Michaels, Hall A Mtg, Oct 3, 2017