Polarized Positron Experiment at KEK-ATFPolarized Positron Experiment at KEK-ATF

JPSMeeting2005JPSMeeting2005

KEK ATF におけるパルス偏極陽電子生成３　　　　〜偏極陽電子生成とその偏極度測定〜

浦川順治、 @ 大森恒彦、奥木敏行、栗原良将、黒田隆之助 A 、斉藤卓 A 、坂上和之 A 、広瀬立成 A 、福田将史 B 、鷲尾方一 A

高エ研、早大理工総研 A 、放医研 B

Pol. e+ Production

N = 1 x 107 /bunch

T(rms) = 31 psecCan NOT measure each e+

Polarimetry ?

Design values

Ne+ = 1 x 104/bunch (Ee+ = 25 to 45 MeV)Pol. e+ ~ 80 %

polarized e+

Measure e+ polarization : use Bremsstrahlung -ray

Pb conveter

-ray

E = 40 MeV

Measurement and Cross-Check Measurement

Cross-Check

non (Liner)

)Calculate A

)Calculate A

)Calculate A

e+ beam pol.(laser pol)

e- spin in iron (magnet pol.)

Calculate A

Calculate A

magnet pol.e+ beam pol.

A(0) : A(0)=0

Zero magnet current Not Equal No-polarization, due to residual magnetism

))

A(R) : A(R)= ~ + 0.7 %

A(L) : A(L)= ~ - 0.7 %

A(P) : A(P)= ~ + 0.7 %

A(N) : A(N)= ~ - 0.7 %

R

L

0

P

N

expected value

(MC)

CO2 Cherenkov

CO2 Cherenkov

Leakage B Feild e+ trajectry Acceptance

Mag. Pol. = P

Mag. Pol. = N

e+

e+

If e+ beam go just center of ma

gnet -> OK

CO2 Cherenkov

CO2 Cherenkov

Leakage B Feild e+ trajectry Acceptance

Mag. Pol. = P

Mag. Pol. = N

e+

e+

If e+ beam go off center, trajectry near magnet

may be different when we flip magnet.

Acceptance Correction Define: A(TP,TN) = (TP-TN)/(TP+TN)

A(TP,TN) = 0 from absorption in iron

A(TP,TN) = 0 acceptance affected by B field

) average transmission TP

magnet pol. e+ beam pol.

non

)nonaverage transmission TN

Use A(TP,TN) for acceptance correction

P

N

Measurement

Cross-Check

non (Liner)

)))

e+ beam pol. magnet pol.

magnet pol.e+ baem pol.

))

e+ polarization (e+ run): results

A(R)= +0.16± 0.28%

A(L)= -1.63± 0.28%

A(0)= -0.24± 0.28%

R

L

A(P)= +0.85± 0.28%

A(N)= -0.93± 0.28%

A(TP,TN) = -0.57± 0.17%

Acceptance Correction

0

P

N

preliminary

Measurement

Cross-Check

non (Liner)

)))

e+ beam pol. magnet pol.

magnet pol.e+ beam pol.

))

e+ polarization (e+ run): results

A(R)= +0.72± 0.28%

A(L)= -1.07± 0.28%

A(0)= +0.33± 0.28%

A(P)= +0.85± 0.28%

A(N)= -0.93± 0.28%

Acceptance Corrected by A(TP,TN)

R

L

0

P

N

preliminary

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)= +0.72± 0.28%

A(L)= -1.07± 0.28%

A(0)= +0.33± 0.28%

preliminary results

W- target

Separationmagnet

e+

e+

e-

W- target

e+Separation

magnet

polarized

e-

e-

e+ run e- run

We did e- run, also.

Measurement

Cross-Check

non (Liner)

)))

e- beam pol. magnet pol.

magnet pol.e- beam pol.

))

e- polarization (e- run): results

A(R)= +0.81± 0.28%

A(L)= -0.91± 0.27%

A(0)= -0.26± 0.27%

A(P)= +0.76± 0.27%

A(N)= -0.96± 0.27%

A(TP,TN) = -0.12± 0.16% NO correction is necessary

Acceptance Correction

R

L

0

P

N

preliminary

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(L)= -0.91± 0.27%

A(0)= -0.26± 0.27%

A(R)= +0.81± 0.28%

preliminary results

Polarized Positron Experiment at KEK-ATFPolarized Positron Experiment at KEK-ATF

JPSMeeting2005JPSMeeting2005

まとめ1)レーザー光の偏極が、 γ 線へ、そし

て対生成された e+ と e- へと伝達されていく事が確認された。

2) 短パルス高強度の偏極 γ 線、 e+ 、 e- の偏極測定法が確立できた。

3) 陽電子の透過率のアシンメトリーは予想値である ~ 0.7 % に一致した。

--> 偏極度 ~80% の陽電子ビームが得られた。

ここで終わり。これから後はバックアップ

i) proof-of-principle demonstrations

ii) accumulate technical informations: polarimetry, beam diagnosis, …

Experiment@KEK

T = 31 p sec.T = 31 p sec.

T = 31 p sec.