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Status of experiment at KEK-ATF

Status of experiment at KEK-ATF. Hirotaka Shimizu Hiroshima University. Cavity-Compton Collaboration. KEK Hiroshima University Waseda University IHEP (China). Contents. Introduction - Proof of Principal Exp. at ATF - Improvement to Cavity-Compton Pulse laser stacking

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Status of experiment at KEK-ATF

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  1. Status of experimentat KEK-ATF Hirotaka Shimizu Hiroshima University

  2. Cavity-Compton Collaboration KEK Hiroshima University Waseda University IHEP (China)

  3. Contents • Introduction - Proof of Principal Exp. at ATF - • Improvement to Cavity-Compton • Pulse laser stacking • Current status • Summary

  4. Compton Scattering Proof of Principal Exp. at ATF Pair creation Metal Converter : Polarized Laser Laser Compton Experiment with Circler Polarized Laser [T.Okugi et al Jpn.J.Appl.Phys.35(1996)3677]

  5. Gamma-ray polarization measurement results γ Run ■Gamma-ray polarization =92±2% ■Monte-Carlo simulation result Pol =88% → Fukuda et al. PRL91(2003)164801

  6. Positron polarization measurement results e+ Run ■Positron polarization = 73±13% (A = 0.91±0.18%) ■Monte-Carlo simulation result Pol = 77% → Omori et al. PRL96(2006)114801

  7. Pol.γ-ray Experimental Set-Up of Ext. Compton 〜 10m Electron Beam Laser Beam Rep. Rate 3.12Hz 1.56Hz Energy 1.28GeV 2.33eV Table : Repetition Rate & Energy

  8. Results of Ext. Line Compton • Observed Polarization of γ-ray. ➾ good agreement with simulation tests • # of γ-ray/bunch : 1.0×106➾2.0×107 • Observed Polarization of Positron. ➾ also confirmed consistency ( >70% ) • Obtained # of e+/bunch :2.0×104 Proof-of-Principal Exp. Has Done !

  9. The “RDR” requirements for ILC positron source based on laser Compton scheme, Next Issue : Create High Intensity Positron

  10. Ideas for Compton Based Scheme ▻Compton Base ▻Ring Structure ▻Using Optical Cavity

  11. Tactics for the New R&D Electron Beam KEK-ATF provides 1.3GeV beam (714MHz RF)

  12. Tactics for the New R&D Electron Beam KEK-ATF provides 1.3GeV beam (714MHz RF) Laser 357MHz 10W mode-locked laser [λ=1064nm]

  13. Pulse Laser Stacking Distance : L Electron Beam 2L/c = 2.8ns Laser (Constraint for Cavity Length)

  14. L〜 420mm One of the most important point “Cavity Length Control”

  15. γ-ray IP in the Ring Electron Beam Laser

  16. ● Can start with existing/obtainable equipments ● Quick install with intermediate finesse cavity ● Accumulated skills of LW/X-ray source study groups （Cavity-Compton Collaboration） Tactics for the New R&D KEK-ATF Provides 1.3GeV e-beam 〜30MeVγ-ray is obtainable. It could be a required ILC e+ source !! 357MHz 10W mode-lock laser [λ=1064nm]

  17. First Run for Cavity-Compton All equipments are installed into the DR on 12th Sep. 2007. The first signal has found on 30th Jan. 2008. γ-ray detector (shared with LW) Cavity-Compton Setup (IP)

  18. Equipments and Summary

  19. End-Cap of Cavity (Mirror & Piezo mounted ) Laser Injection electron beam

  20. Mirror Housing Piezo Housing

  21. Leaf Spring

  22. Cavity Length Control using Piezo via Leaf Spring Dynamic Range : 〜5μm (short Piezo)

  23. Exp. Parameters

  24. Summary • Polarized positron source with laser Compton scheme is now ongoing. • Date sets analysis report -> Ushio’s talk • During this summer shutdown, :Improve for more stability ->Miyoshi’s talk • Future plan, :Install four mirror cavity (next Summer)

  25. L

  26. L Depends on the intrinsic cavity length of laser Phase Condition Timing Condition The Key Techniques - Pulse Laser Stacking - Waist Size

  27. L Depends on the intrinsic cavity length of laser Phase Condition Timing Condition The Key Techniques - Pulse Laser Stacking - Waist Size

  28. Tactics for the New R&D

  29. Top View of Mover Table X Z Y

  30. in Horizontal direction

  31. in Vertical direction

  32. Compton Scattering Introduction(Historical Background) Creating e+ with e-beam & laser are proposed [T.Okugi et al Jpn.J.Appl.Phys.35(1996)3677] Pair creation Metal Converter : Polarized Laser

  33. Studied following Subjects • Mover Table Scan (V and H) • Collision Timing Scan • Collision with Cavity Length Feed-Back • Phase Lock Loop Stability Test • Signal Intensity Check with Collimator • Signal Intensity Check with Local Bump ※subjects in blue font must be improved more in stability point of view → future study

  34. Experimental set up at Extraction Line Laser Beam : 2.33eV (532nm) , 1.56 Hz Electron Beam : 1.28GeV , 3.12 Hz ⇒ Obtained # of Gamma : 2×10^7/bunch

  35. Pol.γ-ray

  36. Gamma-Ray Creation (Compton Case) ? for gamma ray’s energy, • Able to create ～30MeV gamma rays ?for gamma ray’s polarization, • Polarization of Laser easily/precisely controlled with wave plate “Compton Scattering”

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