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

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

3. K. Floettmann KEK, Nov. 13-15, 2004 Conventional vs. Gamma Based Source Target Photons 10-20 MeV Electrons 0.1-10 GeV Primary BeamCapture Optics thin target: 0.4 X 0 thick target: 4-6 X 0

4. K. Floettmann KEK, Nov. 13-15, 2004 Parameters of existing and planed positron sources rep rate # of bunches per pulse # of positrons per bunch # of positrons per pulse TESLA/ILC5 Hz28202 · 10 10 5.6 · 10 13 NLC120 Hz192 0.75 · 10 10 1.4 · 10 12 SLC120 Hz1 5 · 10 10 DESY positron source 50 Hz1 1.5 · 10 9

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

6. K. Floettmann KEK, Nov. 13-15, 2004 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” 1 st EPAC Rome 1988

7. K. Floettmann KEK, Nov. 13-15, 2004 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.

8. K. Floettmann KEK, Nov. 13-15, 2004 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)

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

10. K. Floettmann KEK, Nov. 13-15, 2004 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

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

12. K. Floettmann KEK, Nov. 13-15, 2004 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

13. K. Floettmann KEK, Nov. 13-15, 2004 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

14. K. Floettmann KEK, Nov. 13-15, 2004 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

15. K. Floettmann KEK, Nov. 13-15, 2004 Low energy operation 5 Hz operation2.5 Hz operation

16. K. Floettmann KEK, Nov. 13-15, 2004 Low energy operation  scaling (fundamental) nominal 5 Hz operation 2.5 Hz luminosity operation 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)

17. K. Floettmann KEK, Nov. 13-15, 2004 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  physics options source

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

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

20. K. Floettmann KEK, Nov. 13-15, 2004 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

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

22. K. Floettmann KEK, Nov. 13-15, 2004 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

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

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

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

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

27. K. Floettmann KEK, Nov. 13-15, 2004 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

28. K. Floettmann KEK, Nov. 13-15, 2004 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

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

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

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

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

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

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

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

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

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

38. K. Floettmann KEK, Nov. 13-15, 2004 E-166 Demonstration Experiment for a Polarized Positron Source 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

39. K. Floettmann KEK, Nov. 13-15, 2004 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.

40. K. Floettmann KEK, Nov. 13-15, 2004 Undulator Parameter for Polarized Positron Source ParameterTESLAE-166 Length~150 m1 m Beam200 GeV50 GeV Period14 mm2.4 mm B-field0.7 T0.76 T Energy of first Harmonic 20 MeV9.6 MeV Positrons/bunch 3 · 10 10 2 · 10 7

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

42. K. Floettmann KEK, Nov. 13-15, 2004 E-166 Demonstration Experiment for a Polarized Positron Source Conversion of photons to positrons in 0.5 X 0 Ti-target Measurement of polarization of photons and positrons by Compton transmission method Expected polarization ~50%

43. K. Floettmann KEK, Nov. 13-15, 2004 E-166 Demonstration Experiment for a Polarized Positron Source E166 is a demonstration of production of polarized 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

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

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

46. K. Floettmann KEK, Nov. 13-15, 2004 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

47. K. Floettmann KEK, Nov. 13-15, 2004 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 ATF KEK: 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

48. K. Floettmann KEK, Nov. 13-15, 2004 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

49. K. Floettmann KEK, Nov. 13-15, 2004 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.

50. K. Floettmann KEK, Nov. 13-15, 2004 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 11 th to 13 th April 2005 http://www.astec.ac.uk/id_mag/ID-Mag_Helical_ILC_Positron_Production_Workshop.htm