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E166 Collaboration MeetingPrinceton, 22-24 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 volumePhoton Analyzer: 50 mm dia. x 150 mm longPositron Analyzer: 50 mm dia. x 75 mm long
E166 Collaboration MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. Peter Schüler
Pe ≈ 0.07
ΔPe/Pe < 0.05 (aim of proposal)
electron polarization of the iron: M = manetization n = electron densityμB = Bohr magneton g‘ = magneto-mechanical factor
3
Spin and Magnetization
E166 Collaboration MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. 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‘ = 1.919 ± 0.002 for pure iron i.e. orbital effects contribute about 4%
Note: g‘ = 2 Ms / M = 1 (pure spin magnetization) γ = e/m g‘ = 1 Ms / M = 0 (pure orbit magnetization) γ = ½ (e/m)
4
Analyzer Magnets
E166 Collaboration MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. Peter Schüler
CsI-Detector
e+ Analyzer
Pickup Coils
e+ Analyzer Analyzer
5
Field Distribution Modeling(Vector Fields OPERA-2d)
E166 Collaboration MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. Peter Schüler
R = 0 mm
10
15
20Bz (T)
Z (mm)
longitudinal field distribution: Bz (R,Z)field drops gradually towards the ends: Leff / L < 1
center
end
6
Field Distribution in 2d(Vector Fields OPERA-2d)
E166 Collaboration MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. Peter Schüler
longitudinal field distribution: Bz (R,Z)
R (mm)
Z (mm)
7
Pickup Coils for Flux Measurements:
Positron Analyzer Photon Analyzer
Δz
(mm)
r
(mm)
n
(turns)
Δz
(mm)
r
(mm)
n
(turns)
upstream -20 24.25
4 x 40
= 160 -57.5 24.25 **
center 0 24.25
4 x 38
= 152 0 24.25
4 x 40
= 160
downstream 20 24.25
4 x 40
= 160* 57.5 24.25
4 x 40
= 160
dummy 0 0 0 0 0 0
E166 Collaboration MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. Peter Schüler
(*) positron downstream became dysfuntional after Oct. 2004 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 MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. 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 MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. Peter Schüler
10
Flux and Field Measurements: Results
E166 Collaboration MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. 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 MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. Peter Schüler
No significant field difference seen between „upstream“ and „center“
Z = -20 mm
12
electron polarization of the iron
E166 Collaboration MeetingPrinceton, 22-24 May 2006
Analyzer Magnetic AnalysisK. Peter Schüler
preliminary result for the e+ analyzer: (6.94 ± 0.17) %
0017.00694.00836.083.0LeffL
0.77 0.80 0.83 0.85 0.87 0.88 L/ effL
58 60 62 64 65 66 (mm) effL
25 20 15 10 5 0 (mm) R
02.083.0 L/ effL :mm 75 Llength physicalan shorter th is effLlength Effective
0006.00836.010272.910206.2
10785.1958.0
'
1'2
/10785.1
A 60 ; 0 Z100.0
016.0343.2²5912.0
385.1
²2/
/104
/10272.92
³/10206.2/
1962)(Scott ironpurefor0.0021.919g' with
002.0958.0'
1'2
'
1'2
max
2430
6maxmax
6max
max0
max00
70
24
30
ee
bee
eb
Ave
bebebee
Peff
P
M
g
gP
mAM
TeslaB
Teslam
Vs
RnBBBM
AmT
TeslaJoulem
e
mAZN
g
g
MsM
M
g
gM
MsMsMP
- and the nitty-gritty: