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Lead ( 208 P b) R adius Ex periment : PREX

Lead ( 208 P b) R adius Ex periment : PREX. Elastic Scattering Parity-Violating Asymmetry. E = 1 GeV ,. Z 0 : Clean Probe Couples Mainly to Neutrons. ( T.W. Donnelly, J. Dubach, I Sick ). F N (Q 2 ). Many applications: Nuclear Physics Neutron Stars

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Lead ( 208 P b) R adius Ex periment : PREX

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  1. Lead(208Pb) Radius Experiment: PREX Elastic Scattering Parity-Violating Asymmetry E = 1 GeV, Z0 : Clean Probe Couples Mainly to Neutrons ( T.W. Donnelly, J. Dubach, I Sick ) FN (Q2) • Many applications: • Nuclear Physics • Neutron Stars • Atomic Parity Violation • Heavy Ion Collisions Fundamental Nuclear Physics Combine with astophysics observations Is dense Neutron-rich matter exotic ? ( Dany Page ) PREX : precise measurement of the density -dependence of the symmetry energy.

  2. Beam Requirements See PREX web page for details. Run-averaged Helicity-correl. One-Day Avg Jitter @30 Hz Nominal 1 ppb 5 ppb 1.05 GeV 5 ppm Energy 1 ppm 200 ppb 50 – 100 uA 0.1 % Current 10, 20 um 10, 20 nm 2, 4 nm 0, 0 Positions (X,Y) 1.5, 5.0 nrad 1.5, 5.0 urad 0.3, 1.0 nrad 0, 0 Angles (X’ , Y’ ) 10-4 10-3 < 150 um -- Spot Size 100% longitudinal < 1% transverse Transverse Spin

  3. Targets I max (uA) raster comment 4 x 4 100 Production Target Lead / Diamond Danger of melting ! 5 4 x 4 Thin Lead (0.05 mm) Carbon Targets 100 N/A Thick, thin, super-thin, holey, and multi-foil optics Calibration targets To determine <angle> 4 x 4 20 Water Cell Removed after 3 days Tantalum Target 100 N/A (also an “empty target” position)

  4. Special Considerations See PREX web page for details • Complex Beam Setup and Run Plan (2 weeks) • Helicity Reversal Frequency : • Polarization ~100 Longitudinal • Collaboration Experts involved in Polarized Source Configuration • Beam Tune for Compton Polarimeter • Fast Feedback needed Shown on PREX wiki: prex.jlab.org 30, 120, 240 Hz. To be optimized and sometimes varied

  5. Special Considerations(cont.) • Beam modulation – new faster scheme • New “Double Wien” • Commissioning of new HRS Septum Magnets • Commissioning of Upgraded Moller Polarimeter • Commissioning of Upgraded Compton Polarimeter • High Radiation Levels • COO, RSAD, ESAD, and 3 OSPs available. New OSP Verify does not steer the beam. New OSP “User” beam -- pulsed Align new magnet New OSP hallaweb.jlab.org/parity/prex/docs/safety.html

  6. PREX Run Plan • Now until ~Mar 11 • Installations in progress • Commissioning Mar 11 - 24 • Detailed plan at prex.jlab.org (Wiki) • Production Mar 24 - May 25 Take data on Lead / Diamond target Periodic Auxiliary Measurements Moller, Q2 , Backgrounds Transverse Polarization Test Run ( 2.5 shifts ) Drink Champagne ! (after)

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