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Lead Target

Lead Target. D. J. Margaziotis HAPPEX Collaboration Meeting 12-1-06. Lead Target Status. Pb target intended for E06-007: 208 Pb(e,e’p) 207 Tl Scheduled to run in 2007: Officially, starting April 27 Unofficially (more likely but not confirmed), starting ~February 24 E06-007:

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Lead Target

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  1. Lead Target D. J. Margaziotis HAPPEX Collaboration Meeting 12-1-06

  2. Lead Target Status • Pb target intended for E06-007: 208Pb(e,e’p)207Tl • Scheduled to run in 2007: • Officially, starting April 27 • Unofficially (more likely but not confirmed), starting ~February 24 • E06-007: • Study correlations and relativistic effects in nuclear medium • Measure cross sections for low-lying 207Tl states for pm < 500 MeV/c • Extract ATL for pm < 300 MeV/c • Quasi-elastic xB=1 conditions, perpendicular kinematics • Fixed q=1.0 GeV/c, =0.433 GeV; Q2=0.81 (GeV/c)2 • I = 100 µA

  3. Past Hall A Experience with Pb • Test #1 • 0.5 mm Pb foil in “beer can” cell with flowing LH2 cooling • 3 foils, at 45°, 1” apart. • First upstream foil survived I = 60 µA, with only horizontal raster • Expect single foil could take I > 60 µA with 4 x 4 mm2 raster • Test #2 • Single-slot target-ladder block designed for PREX experiment • 0.5 mm Pb foil “sandwiched” between two 0.15 mm diamond foils • Actively cooled – cryogen through block • Successfully tested with up to I = 80 µA • Calculations indicate OK with I = 100 µA • Difficulty with knowing beam spot position relative to target center • Conclusion: Pb target is feasible for I ≤ 100 µA

  4. Simulations for Target Choice • Best available Hall A resolution will not cleanly separate low-lying Tl states • Peak extraction through peak fitting necessary • A successful peak fitting procedure was developed • GEANT simulations to assess attainable Em resolution • GEANT assumed Em profile and location of states are known • Both target configurations simulated • Result: Lead-Diamond sandwich preferred solution • Peak fitting works well even with modest number of counts to be fitted provided the line shape is known well. • Em profile will be determined experimentally by measuring a clean peak from 209Bi

  5. Weighted sum Effect of Target Thickness-GEANT 0.5 mm Pb-No diamond sandwich 0.1 mm Pb-No diamond sandwich GEANT shows good peak extraction possible given good statistics Weighted sum

  6. Choice of Pb Foil Thickness-GEANT pm = 100 MeV/c missing mass spectra 0.1 mm Pb sandwich 0.2 mm Pb sandwich • 0.1 mm foil count rates too low • 0.2 mm Pb is a good compromise between resolution and statistics • 0.17 mm is effective thickness of 0.15 mm Pb foils at 30°

  7. Present Plan for E06-007 Pb Target • Single-slot target ladder block • Similar design to previously tested target block (Test #2) • Design details TBD (by target group) • Have requested active cryo-cooling • Pb sandwich: • 0.15 mm 208Pb foil • 2 x 0.15 mm diamond foils • Positioned at 30° toward HRS-p • Bi sandwich: • 0.20 mm 209Bi foil – measure line shape of a clean lead-like peak • 2 x 0.15 mm diamond foils • Positioned at 30° toward HRS-p • Other targets on ladder: • Carbon (thickness TBD) – for background studies • BeO • Beam Current: 100 µA

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