LCWS2005 at Stanford 18-22/Mar/2004

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Polarized e Generation Measurement at KEK
Laser-based polarized e
Tsunehiko OMORI (KEK)
LCWS2005 at Stanford 18-22/Mar/2004
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Collaboration
KEK
Y. Kurihara, T. Okugi, J. Urakawa, T.Omori
Tokyo Metropolitan Univ
A.Ohashi
Waseda Univ.
I.Yamazaki, K. Sakaue, T. Saito, R. Kuroda, M.
Washio, T. Hirose
National Institute of Radiological Sciences
M. Nomura, M. Fukuda
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Experiment_at_KEK
DT 31 p sec.
DT 31 p sec.
DT 31 p sec.
i) proof-of-principle demonstrations
ii) accumulate technical informations
polarimetry, beam diagnosis,
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Accelerator Test Facility_at_KEK
120 m
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g-ray Measured Asymmetry
A -0.93 0.15
A 1.18 0.15
laser pol. - 79
laser pol. 79
M. Fukuda et al., PRL 91(2003)164801
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Pol. g-ray Production
Done Mar. 2002
Ng 1 x 106 /bunch DT(rms) 31 psec Pol. g
88 (if laser pol. 100)
(measure Eg gt 21 MeV)
M. Fukuda et al., PRL 91(2003)164801
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Pol. e Production
Design values
Ng 1 x 107 /bunch (with new laser)
Ne 1 x 104/bunch (Ee 25 to 45 MeV) Pol.
e 80
DT(rms) 31 psec Can NOT measure each
e Polarimetry ?
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Measure e polarization use Bremsstrahlung
g-ray
g-ray
polarized e
E 40 MeV
Pb conveter
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Measurement and Cross-Check
Measurement
Fix e beam pol. (fix laser pol)
Flip e- spin in iron (Flip magnet pol.)
)
Calculate A
A(R)
R
)
Calculate A
A(L)
L
)
Calculate A
non (Liner)
A(0) A(0)0 expected
0
Cross-Check
Fix magnet pol.
Flip e beam pol.
)
Calculate A
A(P)
P
)
N
A(N)
Calculate A
Zero magnet current Not Equal No-polarization,
due to residual magnetism
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Leakage B Feild e trajectry Acceptance
Mag. Pol. P
e
CO2 Cherenkov
If e beam go just center of magnet -gt OK
Mag. Pol. N
e
CO2 Cherenkov
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Leakage B Feild e trajectry Acceptance
Mag. Pol. P
e
CO2 Cherenkov
If e beam go off center, trajectry near magnet
may be different when we flip magnet.
Mag. Pol. N
e
CO2 Cherenkov
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Acceptance Correction
Define A(TP,TN) (TP-TN)/(TPTN)
Fix magnet pol.
Sum e beam pol.
)
P
average transmission TP
non
)
N
average transmission TN
non
A(TP,TN) 0 from absorption in iron
Use A(TP,TN) for acceptance correction
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e polarization (e run) results

preliminary
Measurement
Fix e beam pol.
Flip magnet pol.
)
A(R) 0.16 0.28
R
)
A(L) -1.63 0.28
L
)
non (Liner)
A(0) -0.24 0.28
0
Cross-Check
Fix magnet pol.
Flip e baem pol.
)
A(P) 0.85 0.28
P
)
A(N) -0.93 0.28
N
Acceptance Correction
A(TP,TN) -0.57 0.17
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e polarization (e run) results

preliminary
Measurement
Acceptance Corrected by A(TP,TN)
Fix e beam pol.
Flip magnet pol.
)
R
A(R) 0.72 0.28
)
A(L) -1.07 0.28
L
)
A(0) 0.33 0.28
0
non (Liner)
Cross-Check
Fix magnet pol.
Flip e beam pol.
)
P
A(P) 0.85 0.28
)
A(N) -0.93 0.28
N
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e polarization (e run)
preliminary results
e beam spin
e- spin in Iron
A(R) 0.72 0.28
e beam spin
e- spin in Iron
A(L) -1.07 0.28
e beam spin non
e- spin in Iron
A(0) 0.33 0.28
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We did e- run, also.
e- run
e run
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e- polarization (e- run) results

Measurement
preliminary
Fix e- (laser) pol.
Flip magnet pol.
)
A(R) 0.81 0.28
R
)
A(L) -0.91 0.27
L
)
non (Liner)
0
A(0) -0.26 0.27
Cross-Check
Fix magnet pol.
Flip e- (laser) pol.
)
A(P) 0.76 0.27
P
)
A(N) -0.96 0.27
N
Acceptance Correction
A(TP,TN) -0.12 0.16 NO correction is
necessary
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e- polarization (e- run)
preliminary results
e- beam spin
e- spin in Iron
A(R) 0.81 0.28
e- beam spin
e- spin in Iron
A(L) -0.91 0.27
e- beam spin non
e- spin in Iron
A(0) -0.26 0.27
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Summary
1) We confirmed propagation of the
polarization from laser photons -gt g-rays -gt
pair created es e-s.
2) We established polarimetry of short pulse
high intensity g-rays, positrons, and electrons.
3) Measured value of asymmetries agreed with
expected value. ( 0.7 ) --gt We got e
polarization of 80