1. Lead ( 208 Pb) Radius Experiment : PREX E = 1 GeV, Elastic Scattering Parity-Violating Asymmetry PREX : precise measurement of the density -dependence of the symmetry energy. Z 0 : Clean Probe Couples Mainly to Neutrons Fundamental Nuclear Physics Many applications: 1.Nuclear Physics 2.Neutron Stars 3.Atomic Parity Violation 4.Heavy Ion Collisions Combine with astophysics observations Is dense Neutron-rich matter exotic ? F N (Q 2 ) ( Dany Page ) ( T.W. Donnelly, J. Dubach, I Sick )

2. Beam Requirements Energy Current Positions (X,Y) Angles (X, Y ) Spot Size Transverse Spin See PREX web page for details. Nominal Run-averaged Helicity-correl. One-Day Avg Jitter @30 Hz 1.05 GeV 1 ppb 5 ppb 5 ppm 50 – 100 uA 200 ppb 0.1 % 1 ppm 0, 0 2, 4 nm 10, 20 nm 10, 20 um 0, 0 0.3, 1.0 nrad 1.5, 5.0 nrad1.5, 5.0 urad < 150 um 10 -4 10 -3 -- 100% longitudinal < 1% transverse

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

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. Verify does not steer the beam. hallaweb.jlab.org/parity/prex/docs/safety.html New OSP Align new magnet User beam -- pulsed

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, Q 2, Backgrounds Transverse Polarization Test Run ( 2.5 shifts ) Drink Champagne ! (after)