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GAMMA BASED POSITRON SOURCE OPTIONS FOR ILC Klaus Floettmann DESY

GAMMA BASED POSITRON SOURCE OPTIONS FOR ILC Klaus Floettmann DESY. Contents:. Basics of gamma based sources Status of work Who wants to Do What?. Conventional vs. Gamma Based Source. Photons 10-20 MeV. Primary Beam. Capture Optics. Target. thin target: 0.4 X 0.

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GAMMA BASED POSITRON SOURCE OPTIONS FOR ILC Klaus Floettmann DESY

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  1. GAMMA BASED POSITRON SOURCE OPTIONS FOR ILC Klaus Floettmann DESY KEK, Nov. 13-15, 2004

  2. Contents: • Basics of gamma based sources • Status of work • Who wants to Do What? KEK, Nov. 13-15, 2004

  3. Conventional vs. Gamma Based Source Photons 10-20 MeV Primary Beam Capture Optics Target thin target: 0.4 X0 Electrons 0.1-10 GeV thick target: 4-6 X0 KEK, Nov. 13-15, 2004

  4. Parameters of existing and planed positron sources KEK, Nov. 13-15, 2004

  5. The Problem: Target Heating KEK, Nov. 13-15, 2004

  6. Number of Positrons / Source Area • Example of the rotating target for TESLA: • 0.8 m diameter • 1250 revolutions per minute • 52 m/s on the circumference • 4 cm in a pulse train of 0.8 ms • Conceptual design for a rotating feed-through: • “A Megawatt Electron Positron Conversion Target – A Conceptual Design” 1st EPAC Rome 1988 KEK, Nov. 13-15, 2004

  7. Heat Capacity of the Target Material Low Z materials have a higher heat capacity (Dulong Petit Rule) but high Z materials give a higher positron yield. KEK, Nov. 13-15, 2004

  8. Positron Yield vs. Target Thickness for a Photon based Source "Structural Modeling of Tesla TDR Positron Target," Werner Stein, John C. Sheppard, July 2002 (SLAC-TN-03-043) KEK, Nov. 13-15, 2004

  9. Radiation Damage Material Test at BNL collaborative effort of SLAC and other labs NOTE: Gamma based sources produce significantly less neutrons than conventional sources. KEK, Nov. 13-15, 2004

  10. How to Increase the Capture Efficiency? • Increase the acceptance of the capture optics • requires a Predamping ring with large acceptance • Improve the positron emittance • photon based positron source with thin target KEK, Nov. 13-15, 2004

  11. Transverse momenta conventional source thin target source KEK, Nov. 13-15, 2004

  12. Comments concerning the DR design • Present situation: on energy acceptance is ok, off energy acceptance is too small • improve off energy acceptance • investigate possibilities to reduce the energy spread by scraping or removing correlations • Better communication between DR people and positron people is required • assumed positron distributions seem to be too pessimistic sometimes • realistic distributions should be used as input • Operation of a gamma based positron source without predamping ring should be possible KEK, Nov. 13-15, 2004

  13. Undulator Based Positron Source • Undulator length depends on the integration into the system, i.e. the distance between undulator exit and target which is required for the beam separation: • ~ 50-150 m KEK, Nov. 13-15, 2004

  14. Integration of the Source into the BDS of TESLA Auxiliary and Commissioning source “Conceptual Design of a Positron Pre-Accelerator for the TESLA Linear Collider” TESLA-99-14 “Conceptual Design of a Positron Injector for the TESLA Linear Collider” TESLA-00-12 KEK, Nov. 13-15, 2004

  15. Low energy operation 2.5 Hz operation 5 Hz operation KEK, Nov. 13-15, 2004

  16. Low energy operation nominal 5 Hz operation 2.5 Hz luminosity operation g scaling (fundamental) High-energy optimised source Low-energy optimised source NOTE: Higher currents are possible at lower energy if the source is integrated into the BDS (limited by DR) KEK, Nov. 13-15, 2004

  17. Auxiliary and Commissioning Source 500 MeV electron source provides low intensity (~1%) e+ source but same bunch train • commissioning source • standby source for MD when e- system is down • e-e- and gg physics options source KEK, Nov. 13-15, 2004

  18. Design of the Positron Preaccelerator KEK, Nov. 13-15, 2004

  19. The capture optics • low frequency (L-band) • large iris radius • long wave length x’ x’ x x KEK, Nov. 13-15, 2004

  20. Adiabatic Matching Device - AMD • Very basic design considerations by BINP Novosibirsk (internal report): • long pulse seems to be possible • problem is to achieve the required field quality KEK, Nov. 13-15, 2004

  21. NC High Gradient Cavities (solenoid focusing) Design by INR Troitsk KEK, Nov. 13-15, 2004

  22. Optical functions in the Separator Section • separation of photons, positrons and electrons • longitudinal collimation of the positron bunches • transverse collimation can be done in the solenoid section • aim for no particle loss during injection into DR KEK, Nov. 13-15, 2004

  23. NC Low Gradient Cavities (triplet focusing) Design by INR Troitsk KEK, Nov. 13-15, 2004

  24. Phase Space at the exit of the Preaccelerator KEK, Nov. 13-15, 2004

  25. Positron Transfer Line KEK, Nov. 13-15, 2004

  26. Acceleration to 5 GeV in SC Cavities KEK, Nov. 13-15, 2004

  27. Polarized Positron Sources For the production of polarized positrons circularly photons are required. • Methods to produce circularly polarized photons of 10-60 MeV are: • radiation from a helical undulator • Compton backscattering of laser light off an electron beam KEK, Nov. 13-15, 2004

  28. Why polarized positrons Physics potential beyond the scope of this workshop but we can gain a factor of two in the interaction rate (eff. luminosity) by using polarized electron and positron beams KEK, Nov. 13-15, 2004

  29. Polarization Transfer in Pair Production KEK, Nov. 13-15, 2004

  30. Current Current Super Conducting Design • Ribbon-wire wound in a double helix KEK, Nov. 13-15, 2004

  31. Polarization vs. Emission angle KEK, Nov. 13-15, 2004

  32. Model of the Prototype Helical Undulator at Daresbury KEK, Nov. 13-15, 2004

  33. Model of the Prototype Helical Undulator at Daresbury KEK, Nov. 13-15, 2004

  34. Compton Backscattering based Positron Source KEK, Nov. 13-15, 2004

  35. GLC Polarized Positron Source Design KEK, Nov. 13-15, 2004

  36. Multi Collision Point Layout KEK, Nov. 13-15, 2004

  37. GLC Collision Region 10 collision sections, with 20 collision points each: 200 collision points KEK, Nov. 13-15, 2004

  38. About 47 members from 17 institutions: Brunel, CERN, Cornell, DESY, Daresbury, Durham, Jefferson, Humboldt, KEK, Princeton, South Carolina, SLAC, Tel Aviv, Tokyo M.U., Tennessee, Wasada, Yerevan E-166 Demonstration Experiment for a Polarized Positron Source KEK, Nov. 13-15, 2004

  39. E-166 Demonstration Experiment for a Polarized Positron Source • Final Focus Test Beam (FFTB) at SLAC with 50 GeV Electrons. • 1 m long helical undulator produces circular polarized radiation of up to 10 MeV. KEK, Nov. 13-15, 2004

  40. Undulator Parameter for Polarized Positron Source KEK, Nov. 13-15, 2004

  41. Pulsed Undulator for E-166 • Inner diameter 0.89 mm • Magnetic field: 0.76 T • Pulsed current: 2.3 kA • Rate 30 Hz KEK, Nov. 13-15, 2004

  42. E-166 Demonstration Experiment for a Polarized Positron Source • Conversion of photons to positrons in 0.5 X0 Ti-target • Measurement of polarization of photons and positrons by Compton transmission method • Expected polarization ~50% KEK, Nov. 13-15, 2004

  43. E-166 Demonstration Experiment for a Polarized Positron Source • E166 is a demonstration of production ofpolarized positrons for future linear colliders • Uses the 50 GeV FFTB at SLAC • Approved by SLAC in June 2003 • All components or prototypes work properly • Installation of total experiment in FFTB tunnel in August 2004 • First data taking run in October 2004 • Second data taking in February 2005 KEK, Nov. 13-15, 2004

  44. Experiment@KEK KEK, Nov. 13-15, 2004

  45. Experiment@KEK KEK, Nov. 13-15, 2004

  46. Experiment@KEK • 1.) Production of polarized γ‘s and polarized e+ • pol. γ: finished 2002 • pol e+: underway • 2.) Polarimetry • polarimetry of short pulse & high intensity γ rays established • same method applicable for polarized positrons KEK, Nov. 13-15, 2004

  47. Who wants to Do What? (to be completed) • ASIA • contributions to E166 • conceptual design for a polarized positron source for ILC (simulation study)KEK: Y. Kurihara, T. Okugi, J. Urakawa, K. Yokoya, T. Omori Tokyo Metropolitan Univ.: K. Dobashi National Institute of Radiological Sciences: I. Sakai Waseda Univ.: T. Aoki, M. Washio, T. Hirose Sumitomo Heavy Industries: A. Tsunemi • experimental production of polarized positron at ATFKEK: Y. Kurihara, T. Okugi,  J. Urakawa, T.Omori Tokyo Metropolitan Univ.: A. Ohashi National Institute of Radiological Sciences: M. Nomura, M. Fukuda Waseda Univ.: I. Yamazaki, K. Sakaue, T. Saito, R. Kuroda, M. Washio, T. Hirose KEK, Nov. 13-15, 2004

  48. Who wants to Do What? (to be completed) • Europe • EuroTEV (s. talk by E. Elsen) • contributions to E166 • interest to continue work on preaccelerator: beam dynamics, structures, diagnostics INR Troitsk: V. Paramonov • synergies with FEL work at DESY: NC structure design, code development, beam dynamics KEK, Nov. 13-15, 2004

  49. Who wants to Do What? (to be completed) • USA • E166 SLAC, collaborators: John Sheppard et al. • conceptual positron source design SLAC, collaborators: John Sheppard et al. • material tests SLAC and collaborators: John Sheppard et al. • more from SLAC ?????? • beam dynamics simulations/experiment ANL: Wei Gei et al. Fermilab: Philippe Piot et al. KEK, Nov. 13-15, 2004

  50. Workshop Announcement 'Workshop on Positron Sources for the International Linear Collider‘ This workshop will discuss relevant issues for positron production for the ILC Daresbury Laboratory 11th to 13th April 2005 http://www.astec.ac.uk/id_mag/ID-Mag_Helical_ILC_Positron_Production_Workshop.htm KEK, Nov. 13-15, 2004

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