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Laser Based Polarized e + Source for ILC

Laser Based Polarized e + Source for ILC. Tsunehiko OMORI (KEK). 8th ACFA LCWS@ Daegu 11-14/Jul/2005. Why laser based?. i) Full energy/intensity e - beam is NOT necessary to produce positrons. Therefore, Electron and positron systems remain independent.

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Laser Based Polarized e + Source for ILC

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  1. Laser Based Polarized e+ Source for ILC Tsunehiko OMORI (KEK) 8th ACFA LCWS@Daegu 11-14/Jul/2005

  2. Why laser based? i) Full energy/intensity e- beam is NOT necessary to produce positrons. Therefore, Electron and positron systems remain independent. Easier development, easier commissioning, easier operation. ii) No problem of low energy operation of the collider.

  3. Today’s talk 1. Experiment at KEK-ATF 2. Concept of Laser Based Polarized e+ Source for ILC

  4. Experiment at KEK-ATF ATF: Accelerator Test Facility for ILC built at KEK Experiment done by Waseda-TMU-KEK collaboration 120 m

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

  6. 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

  7. Ne+ = 3 x 104/bunch Pol(expected) = 80% Asym (expected) = 0.7%

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

  9. e+ polarization (e+ run :June) preliminary results e+ beam spin e- spin in Iron A(R)= +0.60± 0.25% e+ beam spin e- spin in Iron A(L)= -1.15± 0.27% e+ beam spin non e- spin in Iron A(0)= -0.03± 0.26%

  10. Summary of Experiment 1) The experiment was successful. High intensity short pulse polarized e+ beam was firstly produced. Pol. ~ 80% 2) We confirmedpropagation of the polarization from laser photons -> g-rays -> and pair created e+s & e-s. 3) We established polarimetry of short pulse & high intensity g-rays, positrons, and electrons.

  11. Concept of Laser Based polarized e+ source for ILC Thanks to Many Freiends, Especially K. Moenig, J. Urakawa, K. Yokoya

  12. We had a conceptual design for a warm LC. ~ 100 bunches in ~ 300 nsec, bunch to bunch : ~2.8 nsec, 1.2x1010 positrons/bunch, pol. ~ 54%. T. Omori et al., NIM A500 (2003) 232-252

  13. Conceptual Design

  14. Conceptual Design for warm LC Ne+=1.2x1010/bunch Ne+/Ng=1.4% T. Omori et al., NIM A500 (2003) 232-252

  15. Is this applicable to a cold LC? Yes ! With New and Improved design Full use of slow repetition rate (5Hz)

  16. ILC requirements 2x1010 e+/bunch (hard) 3000 bunches/train (hard) 5 Hz (we have time to store e+s) Strategy Old: Design for warm LC make positrons at once. both electron & laser beams : single path T. Omori et al., NIM A500 (2003) 232-252 New: Design for cold LC (ILC) make positrons in 100 m sec. Electron storage ring, laser pulse stacking cavity : Re-use !!! positron stacking ring. Basic Idea: K. Moenig P. Rainer

  17. Laser Pulse Stacking Cavity Input laser (CO2 laser) Energy 10 mJ/bunch 2.8 nsec bunch spacing train length = 50 msec Laser pulse in cavity 500 mJ/bunch single bunch in a cavity Cavity Enhancement Factor = 50

  18. Schematic View of Whole System Ne+/Ng = 0.5%

  19. Strategy 2 Old: Design for warm LC Ne+/Ng = 1.4 % Pol e+ = 54% New: Design for cold LC (ILC) Ne+/Ng = 0.5 % Take Higher Energy e+s = better emittance (good both for stacking & damping) = Higher polarizaton (target: 80 %)

  20. Summary of ILC source design Laser based scheme is good candidate of ILC polarized e+ source. We have new Idea make positrons in 100 m sec. Electron storage ring laser pulse stacking cavity positron stacking ring 2x1010 e+/bunch x 3000 bunches @ 5Hz with high polarization (target 80%) Most of values are extrapolation from old design. We need detailed simulation.

  21. Slides to answer questions

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