E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler General Overview Spin and Magnetization Field Distribution

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


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



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



CsI-Detector

e+ Analyzer

Pickup Coils

e+ Analyzer Analyzer

5

Field Distribution Modeling(Vector Fields OPERA-2d)



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)



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



(*) 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:



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:



10

Flux and Field Measurements: Results



Note: polarimetry was always done at full saturation over the central region (±60A)

Z = 0 (center)

11

Flux and Field Measurements:



No significant field difference seen between „upstream“ and „center“

Z = -20 mm

12

electron polarization of the iron



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:

13

Remaining Work



• repeat magnetic modeling with correct central field values as measured• choose finer mesh spacing • same for photon magnet• generate writeup

Documents

E166 Collaboration Meeting Princeton, 22-24 May 2006 Analyzer Magnetic Analysis K. Peter Schüler General Overview Spin and Magnetization Field Distribution