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The E166 experiment Development of a polarized positron source for the ILC. Karim Laihem on behalf of the E-166 collaboration. LCWS06 Bangalore March 12th 2006. Outline. The goal of the E-166 experiment at SLAC The ATF Compton experiment at KEK Photon transmission polarimetry - PowerPoint PPT Presentation
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K. Laihem E166 collaboration
LCWS06 Bangalore March 12th 2006
The E166 experiment Development of a polarized positron source for the ILC.
Karim Laihem on behalf
of the E-166 collaboration
K. Laihem E166 collaboration
The goal of the E-166 experiment at SLAC
The ATF Compton experiment at KEK Photon transmission polarimetry
The helical undulator
The E-166 setup
Data taking
First results on photon and positron asymmetries
Outline
K. Laihem E166 collaboration
γ
e+
e-
e-
Undulator
Target
D1D2
D3
Gamma Diagnostic
Positron Diagnostic
e-Dump
e-Dump
46.6 GeV10 MeV
1 m
Energy spectrum
The goal of the E-166 experiment at SLAC
• Experimental Demonstration for polarized e+ production • Final focus test beam (FFTB) at SLAC with 46.6 GeV electrons• 1 m long helical undulator produces circular polarized photons
• Undulator radiation 0-10 MeV (Balakin & Mikhailichenko 1979)
• Conversion of photons to positrons in 0.2 X0 W-target
• Measurement of polarization of photons and positrons by Photon transmission method
K. Laihem E166 collaboration
Compton based Pol. e+ Generation
W- target
Separationmagnet
e+
e+
e-
E = 36±8 MeV104/bunch
Emax = 56MeV
Pol. -ray generation: M. Fukuda et al. PRL 91, 164801 (2003)
K. Laihem E166 collaboration
e+ polarization (e+ run )e- spin in Iron
e- spin in Iron
e- spin in Iron
e+ beam spin
e+ beam spin
e+ beam spinnon
A(R)= +0.60 ± 0.25%
A(L)= -1.18 ± 0.27%
A(0)= -0.02 ± 0.25%
T. Omori et al., arXiv:hep-ex/0508026 Phys. Rev. Lett. accepted
ATF-Compton
K. Laihem E166 collaboration
Summary of e+ Run and e- Run
e+ Run e- Run
abs. A= 0.90 ± 0.18% abs. A=0.89 ± 0.19%Pe+ = 73 ± 15(sta) ± 19(sys) Pe- = 72 ± 15(sta) ± 19(sys)
T. Omori et al., arXiv:hep-ex/0508026 PRL accepted
ATF-Compton
K. Laihem E166 collaboration
E166 setup in the FFTB
Positron Table
Gamma Table
TOP VIEWGamma Analyzing magnet
e+ Analyzing magnet
helical undulator
collimators
Positron Table
Gamma Table
~30 m
Undulator
SIDE VIEW
Dump magnets e- beam
Polarized photons productionphotons collimationPositrons diagphotons diag
K. Laihem E166 collaboration
y
z
xe- beam
Undulator photons
I1
I2
I1
I2
I1 = - I2
Helical winding where I1 and I2 are in opposite directions.
Helical winding:• z component of the induced magnetic field cancels• remaining magnetic field describes a helical profile
u
hcE
2
0
2
The helical undulator
mmu 4.2
K. Laihem E166 collaboration
Undulator photon “Energy and Polarization”
Undulator Photon energy spectrum Undulator Photon degree of polarization
1st H
arm
onic
1st H
arm
onic
2nd H
arm
onic
2nd H
arm
onic
K. Laihem E166 collaboration
The Positron production target
e+ Energy distribution (in and out the 0.5 X0 W target)
Positron Polarization profile created by the undulator photons (creation point)
Pola
rize
d
γ b
eam
From
the
Hel
ical
Und
ulat
or
e+
e+e+
e-e-
e-
0.5 X0 W (Tungsten) -> E166
X0 W (Tungsten) = 3.5 mm
Polarization transferin e+ e- pair creation
e+
e-
K. Laihem E166 collaboration
K. Laihem E166 collaboration
Positron and Gamma table at the FFTB (SLAC)
K. Laihem E166 collaboration
Photon transmission polarimetryPhoton transmission polarimetryTransmission
K. Laihem E166 collaboration
Positron Analyzing Power
Positron Energy
Ee+ (MeV)
Positron Polarisation
Pe+ (%)
Positron Asymmetry
δ (%)
Analyzing PowerAe
+ (%)
3 42 0.55 18.6
4 61 0.84 19.7
5 69 0.82 17.0
6 78 0.87 15.9
7 84 0.93 15.8
8 77 0.82 15.0
9 64 0.63 14.0
10 68 0.66 13.9
Expected asymmetriesand analyzing power versuspositron energy
G3 simulation basedon the experimentalsetup of the proposal
Most challenging task for E166 was to measure asymmetries ≤1% in the CsI - Calorimeter
V. Gharibyan
K. Laihem E166 collaboration
•What we have achieved in E166 ? (e+ and photon asymmetry)
Expected asymmetries [%]
(Geant3 Simulation)
Measured asymmetries [%]
AerogelAG2
W-SiGCAL
AerogelAG2
W-SiGCAL
3.54 3.22 3.50 3.52
Peter Schuler, Vahagn Gharibyan DESYWilliam Bugg. University of Tennessee
Positron Asymmetry
Photon AsymmetryR. Dollan, H. Kolanoski, T. Lohse, HU BerlinK. Laihem, S. Riemann, A. Schälicke, DESY, ZeuthenE-166 note, February 28, 2006
G. Alexander, E. Reinherz-Aronis, Tel Aviv Univ.E-166 note, Dec. 19,2005 and Feb. 19, 2006
K. Laihem E166 collaboration
We still need “Aγ“ !!!!The analyzing power
Okay !!!!
Okay !!!!
The asymmetry
Magnetization of theThe Iron core of the analyzing magnet
What about the e+ degree of polarization?What about the e+ degree of polarization?
Transmission
K. Laihem E166 collaboration
Field map Measurement at SLAC.
Figure 5: By with respect X position and Z position.
MERMAID field map calculation.
E166 spectrometer magnetic field study E166 spectrometer magnetic field study
K. Laihem E166 collaboration
E166_Geant4_Simulation
Figure 1: Synoptic scheme of the E166 e+/e- transportation system.. The present study concerns the region between the target up to the Point A, B and C (entrance of the spectrometer, exit of the spectrometer and reconversion target respectively).
K. Laihem E166 collaboration
E166_G4_SIM
Reconversion target C
Point B
Point A
-30 -20 -10 0 10 20 30 40
-2,0
-1,5
-1,0
-0,5
0,0
0,5
1,0
1,5
2,0
MERMAID (Correct geometry)
SLAC MERMAID plane Y=0 I = 150 A (Alexander) Measurement at SLAC plane Y=0 I = 150 A
By
[kG
]
X position [cm]
Spectrometer Current 180 A as an example
K. Laihem E166 collaboration
Summary table of the most relevant parameter for positrons at the reconversion target.
Spectrometer current. IS [A]
Lenscurrent
IL[A]
Positron Energy [MeV]
100 175 3,2
120 200 3,9
140 225 4,7
160 250 5,4
180 275 6
74%
68%
61%
53%
44%
EGS simulationJohn Sheppard
Qu
alit
ativ
e st
ud
y
Co
vere
d r
ang
e.
K. Laihem E166 collaboration
Polar
ized
γ b
eam
From
the
Helic
al
Undul
ator
e+
e+
e+ e
-e-
e-
0.5 X0 W (Tungsten) -> E166
X0 W (Tungsten) = 3.5 mm
TARGET
Gammas:
•GammaConversion
•ComptonScattering
•PhotoElectricEffect
Electrons and Positrons:
•MultipleScattering
•Ionisation
•Bremsstrahlung
Diagnostics (Polarimetry)Cross sections polarization dependent
What is needed in Geant4 for polarized Positron/Electrons studies ?
Polarization transfer to e-/e+
Polarization traking(depolarization effects ?)
MAGNETIC FIELD:
•Compton Scattering •Bhabha Scattering•Moller Scattering•Positron annihilation in Flight•..........
K. Laihem E166 collaboration
Summary and outlook
• E-166 had two excellent runs (June / September 2005).• Asymmetries measured at 6 positron energies. • The helical undulator fulfilled its task.• The analysis asymmetries in the expected range• It still takes some time to come up with a number for the
photon and positron polarization• More detailed Geant4 E-166 simulation work is in progress• The analysis is ongoing….
K. Laihem E166 collaboration
Thank you……