prex issues
DESCRIPTION
PREX Issues. Outline. New issue: souce systematics and Aug. 07 run. Update on old issues. Progress at SU. 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). - PowerPoint PPT PresentationTRANSCRIPT
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PREX Issues
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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
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10 Day test run in Aug07
• Study cross-talk issues.
• Compton tests (Integration)
• Noise test with LUMI, 18 bet ADC’s, etc.
• Detector (Use Moller spectrometer as test beam.
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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 (<1) with
integration.
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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.
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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 oldVacuum system?? Other issues? NeedsFocus at JLab.
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Need 100 ppm pair noise
• 18 bit ADC’s 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: <100 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?
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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 whereDual exponentialHas discontinuity in2nd 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?
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Bin half of one window
Pedestal noiseIs not statistical.The χ2 getsWorse 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 performance;10 ppm pulse pair width??
• Problems isolated– Cross talk– Oscillation
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Difference between cavity and stripline position for one slug
See oscillationIn time (beatFrequency)
See the sameIn the current
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Frequency of noise not stablePlot every fourth point to slow observed frequency and see long times