Polarized Electron Generation and Measurement at KEK: Advances in Laser-based Polarity Techniques

1. Polarized e+ Generation & Measurement at KEK Laser-based polarized e+ Tsunehiko OMORI (KEK) PESP 2004 at Mainz 07-09/Oct/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. Aug. 2004 International Technology Recommendation Panel choose cold technology for International Linear Collider: ILC.

4. 1) Conceptual Design : GLC We have a design for warm LC Simulation Study 10 CO2 lasers + High Current e- accelerator T. Omori et al., NIM A500 (2003) 232-252 2) Experiment@KEK

5. 1) Conceptual Design : ILC Basic Concept is OK for ILC. Simulation Study Design Study is now under way. 2) Experiment@KEK

6. 1) Conceptual Design : ILC Basic Concept is OK for ILC. Simulation Study Design Study is now under way. 2) Experiment@KEK Today’s talk

7. Experiment@KEK i) proof-of-principle demonstrations ii) accumulate technical informations: polarimetry, beam diagnosis, …

9. Experiment@KEK DT = 31 p sec. DT = 31 p sec. DT = 31 p sec.

10. Accelerator Test Facility@KEK 120 m

11. Experiment@KEK step 1) measure polarization of g-ray step 2) measure polarization of e+

12. step 1 Measure Polarization of g-ray

17. Measured Number of g-rays Ng = (1.1± 0.1)x106/bunch in 31 p sec

19. Measured Asymmetry g A= -0.93± 0.15 % A= 1.18± 0.15 % laser pol. = - 79 % laser pol. = + 79 %

20. 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

21. step 2 Measure Polarization of e+

22. Pol. e+ Production Now Under Way Design values Ng = 1 x 107 /bunch (with new laser) Ne+ = 3 x 104/bunch (Ee+ = 25 to 45 MeV) Pol. e+ = 77 % DT(rms) = 31 psec Can NOT measure each e+ Polarimetry ?

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

26. Current Situation Whole hardware: ready with small problems Data taking in April-June: Ng ≈ 1 x 107 /bunch : achieved Pol. e+ production and polarimetry : Preliminary Result

27. Measured Asymmetry: e+ preliminary e+ spin A= +0.71± 0.23 % e- spin in Iron e+ spin A= -1.1± 0.23 % e- spin in Iron

28. Problem what-we-want-to-do Fix e+ (laser) pol. Flip magnet pol. ) Calculate A ) Calculate A ) Calculate A reference: A=0 expected Liner

29. Problem what-we-want-to-do Fix e+ (laser) pol. Flip magnet pol. ) Calculate A ) Calculate A ) Calculate A reference: A=0 expected Liner reason: magnet pol. affect detector gain what-we-did Fix magnet pol. Flip e+ (laser) pol. ) Calculate A ) Calculate A Zero magnet current Not Equal No-polarization, due to residual magnetism Improved magnetic shield of the detector (summer)

30. Summary

31. Summary 1) Production of pol. g and pol. e+ i) Pol. g: finish 2002 M. Fukuda et al., PRL 91(2003)164801 ii) Pol. e+: now under way. 2) Polarimetry We established polarimetry of short pulse & high intensity g-ray. The same method can be applicable to polarimetry of e+. We got preliminary results. Next run in coming Autumn with improved detector. 3) Liner Collider : ILC Laser-Compton: option for pol. e+ source

32. Slides to Use Answering Questions

35. here here Capture = 4.1% Pol. = 77%

37. e- beam laser beam Head-on collision a pair of parabolic mirror

38. a collision section

39. 10 collision sections in total