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LCWS2005 at Stanford 18-22/Mar/2004

Polarized e + Generation & Measurement at KEK. Laser-based polarized e +. Tsunehiko OMORI (KEK). LCWS2005 at Stanford 18-22/Mar/2004. Collaboration. KEK. Y. Kurihara, T. Okugi, J. Urakawa, T.Omori. Tokyo Metropolitan Univ. A.Ohashi. Waseda Univ.

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LCWS2005 at Stanford 18-22/Mar/2004

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  1. Polarized e+ Generation & Measurement at KEK Laser-based polarized e+ Tsunehiko OMORI (KEK) LCWS2005 at Stanford 18-22/Mar/2004

  2. 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

  3. Experiment@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, …

  4. Accelerator Test Facility@KEK 120 m

  5. g-rayMeasured 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

  6. 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 > 21 MeV) M. Fukuda et al., PRL 91(2003)164801

  7. 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 ?

  8. Measure e+ polarization : use Bremsstrahlung g-ray g-ray polarized e+ E = 40 MeV Pb conveter

  9. Measurement and Cross-Check Measurement Fix e+ beam pol. (fix laser pol) Flip e- spin in iron (Flip magnet pol.) ) Calculate A R A(R) ) Calculate A L A(L) ) Calculate A 0 non (Liner) A(0) : A(0)=0 expected Cross-Check Flip e+ beam pol. Fix magnet pol. ) Calculate A A(P) P ) N A(N) Calculate A Zero magnet current Not Equal No-polarization, due to residual magnetism

  10. Leakage B Feild e+ trajectry Acceptance Mag. Pol. = P e+ CO2 Cherenkov If e+ beam go just center of magnet -> OK Mag. Pol. = N e+ CO2 Cherenkov

  11. 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

  12. A(TP,TN) = 0 acceptance affected by B field Acceptance Correction Define: A(TP,TN) = (TP-TN)/(TP+TN) 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

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

  14. 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 Flip e+ beam pol. Fix magnet pol. ) P A(P)= +0.85± 0.28% ) A(N)= -0.93± 0.28% N

  15. 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%

  16. We did e- run, also. e- run e+ run

  17. e-polarization (e- run): results Measurement preliminary Fix e- (laser) pol. Flip magnet pol. ) R A(R)= +0.81± 0.28% ) L A(L)= -0.91± 0.27% ) non (Liner) 0 A(0)= -0.26± 0.27% Cross-Check Flip e- (laser) pol. Fix magnet pol. ) P A(P)= +0.76± 0.27% ) A(N)= -0.96± 0.27% N Acceptance Correction A(TP,TN) = -0.12± 0.16% NO correction is necessary

  18. 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%

  19. Summary 1) We confirmedpropagation of the polarization from laser photons -> g-rays -> pair created e+s & 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 %) --> We got e+ polarization of ~80%

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