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

2 General Overview 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, May 2006 Analyzer Magnetic Analysis K. Peter Schüler P e ≈ 0.07 ΔP e /P e < 0.05 (aim of proposal) electron polarization of the iron: M = manetization n = electron density μ B = Bohr magneton g‘ = magneto-mechanical factor

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

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

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

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

7 Pickup Coils for Flux Measurements: Positron AnalyzerPhoton Analyzer Δz (mm) r (mm) n (turns) Δz (mm) r (mm) n (turns) upstream x 40 = ** center x 38 = x 40 = 160 downstream x 40 = 160* x 40 = 160 dummy E166 Collaboration Meeting Princeton, May 2006 Analyzer Magnetic Analysis K. Peter Schüler (*) positron downstream became dysfuntional after Oct at SLAC (**) photon upstream was damaged already at DESY used 4 turns of special coil wire with 40 wire strands: externally wired in series for 4 x 40 = 160 turns max.

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

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

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

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

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

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