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E166 Collaboration Meeting Princeton, 22-24 May 2006

Analyzer Magnetic Analysis. (Status Report) P. Sch ü ler (DESY). General Overview Spin and Magnetization Field Distribution Modeling Results from Flux and Field Measurements Electron Polarization of the Iron Remaining Work. E166 Collaboration Meeting Princeton, 22-24 May 2006.

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E166 Collaboration Meeting Princeton, 22-24 May 2006

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  1. Analyzer Magnetic Analysis (Status Report) P. Schüler (DESY) • General Overview • Spin and Magnetization • Field Distribution Modeling • Results from Flux and Field Measurements • Electron Polarization of the Iron • Remaining Work E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  2. General Overview M = manetization n = electron density μB = Bohr magneton g‘ = magneto-mechanical factor electron polarization of the iron: Pe≈ 0.07 ΔPe/Pe < 0.05 (aim of proposal) error in e- polarization is dominated by knowledge in effective magnetization M along the photon trajectory: active volume Photon Analyzer: 50 mm dia. x 150 mm long Positron Analyzer: 50 mm dia. x 75 mm long E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  3. Spin and Magnetization g‘ = magneto-mechanical factor: obtained from Einstein - de Haas type experiments, related to gyromagnetic ratio: γ = (g‘/2) ∙ (e/m) Note: g‘ = 2  Ms / M = 1 (pure spin magnetization) γ = e/m g‘ = 1  Ms / M = 0 (pure orbit magnetization) γ = ½ (e/m) … and its ultimate implementation (Scott 1962) g‘ = 1.919 ± 0.002 for pure iron i.e. orbital effects contribute about 4% the principle E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  4. Analyzer Magnets  Analyzer e+ Analyzer Pickup Coils CsI-Detector e+Analyzer E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  5. end Field Distribution Modeling(Vector Fields OPERA-2d) Bz (T) 20 15 10 R = 0 mm Z (mm) center longitudinal field distribution: Bz (R,Z) field drops gradually towards the ends: Leff / L < 1 E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  6. Field Distribution in 2d(Vector Fields OPERA-2d) Z (mm) R (mm) longitudinal field distribution: Bz (R,Z) E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  7. Pickup Coils for Flux Measurements: used 4 turns of special coil wire with 40 wire strands: externally wired in series for 4 x 40 = 160 turns max. (*) positron downstream became dysfuntional after Oct. 2004 at SLAC (**) photon upstream was damaged already at DESY E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  8. Flux Measurements: measure voltage transients in pickup coils upon current reversals data taken by Zen - analyzed by Roman Positron Analyzer (-60  +60 amps) Photon Analyzer (-60  +60 amps) Sawtoothfrom Waveform Generator (for calibration of time base) E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  9. Flux Data: E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  10. Flux and Field Measurements: Results Z = 0 (center) Note:polarimetry was always done at full saturation over the central region (±60A) E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  11. Flux and Field Measurements: Z = -20 mm No significant field difference seen between „upstream“ and „center“ E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  12. electron polarization of the iron preliminary result for the e+ analyzer: (6.94 ± 0.17) % - and the nitty-gritty: E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

  13. Remaining Work • repeat magnetic modeling with correct • central field values as measured • choose finer mesh spacing • same for photon magnet • generate writeup E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler

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