K. LaihemE166 collaboration LCWS06 Bangalore March 12th 2006 The E166 experiment Development of a polarized positron source for the ILC. Karim Laihem on

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


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


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


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)


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


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


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


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


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


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-



Positron and Gamma table at the FFTB (SLAC)


Photon transmission polarimetryPhoton transmission polarimetryTransmission


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


•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) %


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


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


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).


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


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.


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•..........


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….


Thank you……


Backup…


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


IS= 100IL = 175

IS= 120IL = 200

IS= 140IL = 225

IS= 160IL = 250

IS= 180IL = 275

Current [A]


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


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.


Summary table of the most relevant parameter for positrons at the reconversion target.


Lenscurrent

IL[A]


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


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+


E166 Helical undulator parameters vs. TESLA, NLC parametersE166 Helical undulator parameters vs. TESLA, NLC parameters


eepol

pole

PnLPnL

PAPnLP

PnLPTT

TTL

eeLT polecomppairphot

)(

)( )(




Lenscurrent

IL[A]


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

Documents

K. LaihemE166 collaboration LCWS06 Bangalore March 12th 2006 The E166 experiment Development of a polarized positron source for the ILC. Karim Laihem on