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Laser Based Polarized e + e + Source for ILC 8th ACFA LCWS@ Daegu 11-14/Jul/2005 Tsunehiko OMORI (KEK)
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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.
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Today ’ s talk 2. Concept of Laser Based Polarized e + Source for ILC 1. Experiment at KEK-ATF
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Experiment at KEK-ATF 120 m Experiment done by Waseda-TMU-KEK collaboration ATF: Accelerator Test Facility for ILC built at KEK
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i) proof-of-principle demonstrations ii) accumulate technical informations: polarimetry, beam diagnosis, … Experiment@KEK
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-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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Ne+ = 3 x 10 4 /bunch Asym (expected) = 0.7%Pol(expected) = 80%
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polarized e + Measure e + polarization : use Bremsstrahlung -ray Pb conveter -ray E = 40 MeV calculation
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e + polarization (e + run :June ) e - spin in Iron e + beam spin non A(R)= +0.60± 0.25% A(L)= -1.15± 0.27% A(0)= -0.03± 0.26% preliminary results
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Summary of Experiment 1) The experiment was successful. High intensity short pulse polarized e + beam was firstly produced. Pol. ~ 80% 3) We established polarimetry of short pulse & high intensity -rays, positrons, and electrons. 2) We confirmed propagation of the polarization from laser photons -> -rays -> and pair created e + s & e - s.
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Concept of Laser Based polarized e + source for ILC Thanks to Many Freiends, Especially K. Moenig, J. Urakawa, K. Yokoya
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We had a conceptual design for a warm LC. ~ 100 bunches in ~ 300 nsec, bunch to bunch : ~2.8 nsec, 1.2x10 10 positrons/bunch, pol. ~ 54%. T. Omori et al., NIM A500 (2003) 232-252
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Conceptual Design
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Conceptual Design for warm LC T. Omori et al., NIM A500 (2003) 232-252 Ne + =1.2x10 10 /bunch Ne+/N =1.4%
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Is this applicable to a cold LC? Yes ! With New and Improved design Full use of slow repetition rate (5Hz)
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ILC requirements 2x10 10 e + /bunch (hard) 3000 bunches/train (hard) 5 Hz (we have time to store e + s) Strategy New: Design for cold LC (ILC) make positrons in 100 m sec. Electron storage ring, laser pulse stacking cavity : Re-use !!! positron stacking ring. Old: Design for warm LC make positrons at once. both electron & laser beams : single path Basic Idea: K. Moenig P. Rainer T. Omori et al., NIM A500 (2003) 232-252
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Laser Pulse Stacking Cavity Input laser (CO2 laser) Energy 10 mJ/bunch 2.8 nsec bunch spacing train length = 50 sec Cavity Enhancement Factor = 50 Laser pulse in cavity 500 mJ/bunch single bunch in a cavity
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Schematic View of Whole System Ne+/N = 0.5%
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Strategy 2 New: Design for cold LC (ILC) Ne + /N = 0.5 % Take Higher Energy e + s = better emittance (good both for stacking & damping) = Higher polarizaton (target: 80 %) Old: Design for warm LC Ne + /N = 1.4 % Pol e + = 54%
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Laser based scheme is good candidate of ILC polarized e + source. Summary of ILC source design We have new Idea make positrons in 100 m sec. Electron storage ring laser pulse stacking cavity positron stacking ring 2x10 10 e + /bunch x 3000 bunches @ 5Hz with high polarization (target 80%) Most of values are extrapolation from old design. We need detailed simulation.
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Slides to answer questions
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