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).– Cross-talk in the linac (Hall C only)

• Depends on Laser set-up.• Need realistic test to dermine of PREX

must run alone

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.

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.

Recent Compton Progress

• See later talks

• Observed Compton peak with FADC.

• Work at SU (see below).

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%.

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.

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.

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.

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?

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.

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

Compton analysis at SU

• Fix bugs

• Understand goofy runs

• Study line-shape systematics

Fits to spectra look good

Tails now under control

Difference between polyand dual exponential

Spike shows up whereDual exponentialHas discontinuity in2nd derivative

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?

Bin half of one window

Pedestal noiseIs not statistical.The χ2 getsWorse the longer The window

Fanout adds noise

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

Difference between cavity and stripline position for one slug

See oscillationIn time (beatFrequency)

See the sameIn the current

Frequency of noise not stablePlot every fourth point to slow observed frequency and see long times