k. laiheme166 collaboration lcws06 bangalore march 12th 2006 the e166 experiment development of a...
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![Page 1: K. LaihemE166 collaboration LCWS06 Bangalore March 12th 2006 The E166 experiment Development of a polarized positron source for the ILC. Karim Laihem on](https://reader037.vdocuments.mx/reader037/viewer/2022103123/56649d5e5503460f94a3d646/html5/thumbnails/1.jpg)
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
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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
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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
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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)
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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
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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
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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
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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
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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
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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-
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K. Laihem E166 collaboration
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K. Laihem E166 collaboration
Positron and Gamma table at the FFTB (SLAC)
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K. Laihem E166 collaboration
Photon transmission polarimetryPhoton transmission polarimetryTransmission
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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
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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 Asymmetry
Is = 140 A(1.03 ± 0.08) %
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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
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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
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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).
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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
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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.
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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•..........
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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….
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K. Laihem E166 collaboration
Thank you……
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K. Laihem E166 collaboration
Backup…
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K. Laihem E166 collaboration
0 100 200 300 4000,000
0,001
0,002
0,003
0,004
0,005
0,006
0,007
0,008
0,009
0,010
0,011
Ispectro
= 100 A I
spectro = 120 A
Ispectro
= 140 A I
spectro = 160 A
Ispectro
= 180 A
Tra
nsm
issi
on (
Pat
h_03
)
ILENS
[A]
Figure 26. Transmission up to the reconversion target in terms of Signal (or energy) defined by equation 7.
Transmission up to the reconversion target (point C).
Reconversion target C
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K. Laihem E166 collaboration
IS= 100IL = 175
IS= 120IL = 200
IS= 140IL = 225
IS= 160IL = 250
IS= 180IL = 275
Current [A]
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K. Laihem E166 collaboration
100 120 140 160 180
3,0
3,5
4,0
4,5
5,0
5,5
6,0
Po
sitr
on
En
erg
y [M
eV
]
Spectrometer current IS [A]
Figure 33. Positron energy versus spectrometer current.
Positron energy versus spectrometer current
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K. Laihem E166 collaboration
100 120 140 160 180
160
180
200
220
240
260
280
300
320
340
360
380 E166_September_run
d(Target-Lens) = ???? "
E166_Geant4_SIM (Statistics) E166_Geant4_SIM (Signal)
d(Target-Lens) = 3"
I LEN
S[A
]
ISpectro
[A]
Figure 32Setting point “Lens current versus spectrometer current”. Comparison between the E166_G4_SIM and September run.
Setting points E166_G4_SIM versus E166 September run.
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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]
MaximumTransmissio
n(Statistics)
[%]
MaximumTransmission
(Signal) [%]
100 175 3,2 0.61 0.70
120 200 3,9 0.73 0.94
140 225 4,7 0.63 0.97
160 250 5,4 0.52 0.99
180 275 6 0.21 0.44
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K. Laihem E166 collaboration
Polarimeter setup
4 x 109 photons
4 x 105 e+
4 x 109 photons
4 x 107 photons ~ 500 TeV
5 x 104 phE5x106 phE
1.6 x 103 photons of total ~ 6 GeV
2 x 107 e+
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K. Laihem E166 collaboration
E166 Helical undulator parameters vs. TESLA, NLC parametersE166 Helical undulator parameters vs. TESLA, NLC parameters
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K. Laihem E166 collaboration
eepol
pole
PnLPnL
PAPnLP
PnLPTT
TTL
eeLT polecomppairphot
)(
)( )(
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K. Laihem E166 collaboration
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K. Laihem E166 collaboration
Spectrometer current. IS [A]
Lenscurrent
IL[A]
Positron Energy [MeV]
MaximumTransmission
(Statistics) [%]
MaximumTransmission
(Signal) [%]
100 175 3,2 0.61 0.70
120 200 3,9 0.73 0.94
140 225 4,7 0.63 0.97
160 250 5,4 0.52 0.99
180 275 6 0.21 0.44