PREX Issues

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PREX Issues
2
Outline

• New issue souce systematics and Aug. 07 run.
• Update on old issues.
• Progress at SU

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Running With Other Halls

• Helicity-correlations with beam position much
  worse with high current operation in other halls.
• Possible causes
• Cathode (Hall B and C).
• Cross-talk in the linac (Hall C only)
• Depends on Laser set-up.
• Need realistic test to dermine of PREX must run
  alone

4
10 Day test run in Aug07

• Study cross-talk issues.
• Compton tests (Integration)
• Noise test with LUMI, 18 bet ADCs, etc.
• Detector (Use Moller spectrometer as test beam.

5
Compton-Biggest Issue

• New Hardware
• Green laser
• New photon and electron detectors
• Data analysis
• Rewrite code in C style
• Understand systematics
• Integration and Low energy
• Achieve good systematics (lt1) with integration.

6
Recent Compton Progress

• See later talks
• Observed Compton peak with FADC.
• Work at SU (see below).

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Integration test with IR light

• Need to take extended Compton data with electron
  analysis, conventional photon analysis, and
  integrated Compton analysis and ahcieve agreement
  better than 1.

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Plan for 850 MeV Compton

• Assume that some of the time the electron
  analysis will work need to get near enough beam
  to get half of spectrum
• Demonstrate linearity of photon detector response
  with coincidence data.
• Compute linearity with MC-effect of GDR neutron
  production?
• Show that integral and electron agree on good
  days.

9
Warm Septum

• Plan A
• NSF MRI Request submitted to SU, approved at
  Smith (Smith and SU will build the magnets).
• Plan B
• Build at JLab if proposal not funded.

Open issue Can the new magnet use the old Vacuum
system?? Other issues? Needs Focus at JLab.
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Need 100 ppm pair noise

• 18 bit ADCs have arrived.
• Can/should we use Qweak electroncs?
• Do we have difficult ground-loop problems?
• What is our pedestal noise with the new setup?
• Critical test lt100 ppm noise with LUMI.

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Target

• This spring, a 1/3 thickness Pb target with
  diamond cooling will be used in a Hall A
  experiment.
• This will test radiation damage of diamond
  cooling, radiation, etc.
• Is this a good opportunity for a LUMI test?
• Check cavity-stripline agreement?

12
Detector

• Only option thin quartz. Same as Qweak.
• Need to show narrow response to single electrons
  earlier test failed.
• Quartz PMT? More light, less neutrons.

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Other Issues (see memo)

• High Field Moller (Compton Cross-check) Eugene
• Detector Linearity
• Pole-tip Monte Carlo
• Management of large transverse beam asymmetry
• Angle measurement
• Low current running issues

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Compton analysis at SU

• Fix bugs
• Understand goofy runs
• Study line-shape systematics

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Fits to spectra look good
Tails now under control
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Difference between polyand dual exponential
Spike shows up where Dual exponential Has
discontinuity in 2nd derivative
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Noise in FADC

• To integrate, we must add 6x106 samples without
  adding too much noise.
• Following data looks promising, but issue is not
  trivial.
• Is there more noise running in the hall?

18
Bin half of one window
Pedestal noise Is not statistical. The ?2
gets Worse the longer The window
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Fanout adds noise
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Cavity Monitors Work in Progress

• Show great promise Resolution at least as good
  as stripline. (Redundancy).
• Gossip G0 had excellent performance10 ppm pulse
  pair width??
• Problems isolated
• Cross talk
• Oscillation

21
Difference between cavity and stripline position
for one slug
See oscillation In time (beat Frequency)
See the same In the current
22
Frequency of noise not stable
Plot every fourth point to slow observed
frequency and see long times