1. The Path Toward a Linear Collider Barry Barish HEP 2005 Lisbon, Portugal 23-July-05

2. 22-July-05 HEP 2005 - Barish 2 The ITRP Recommendation We recommend that the linear collider be based on superconducting rf technology –This recommendation is made with the understanding that we are recommending a technology, not a design. We expect the final design to be developed by a team drawn from the combined warm and cold linear collider communities, taking full advantage of the experience and expertise of both (from the Executive Summary).

3. 22-July-05 HEP 2005 - Barish 3 The Community then Self-Organized Nov 13-15, 2004

4. 22-July-05 HEP 2005 - Barish 4 The First ILC Meeting at KEK There were 220 participants divided among 6 working groups Working Group 1: Overall Design Working Group 2: Main Linac Working Group 3: Injector, including damping rings Working Group 4: Beam Delivery Systems, including collimator, final focus, etc. Working Group 5: Cavity design: higher gradients,.. Working Group 6: Strategic communication Each working group had three convenors, one from each region

5. The Global Design Effort Formal organization begun at LCWS 05 at Stanford in March 2005 when I became director of the GDE Technically Driven Schedule

6. 22-July-05 HEP 2005 - Barish 6 GDE – Near Term Plan Staff the GDE –Administrative, Communications, Web staff –Regional Directors (one per region) –Engineering/Costing Engineer (one per region) –Civil Engineer (one per region) –Key Experts for the GDE design staff from the world community –Fill in missing skills (later) Total staff size about 20 FTE (2005-2006)

7. 22-July-05 HEP 2005 - Barish 7 GDE – Near Term Plan Organize the ILC effort globally –First Step --- Appoint Regional Directors within the GDE who will serve as single points of contact for each region to coordinate the program in that region. (Gerry Dugan (North America), Fumihiko Takasaki (Asia), Brian Foster (Europe)) –Make Website, coordinate meetings, coordinate R&D programs, etc R&D Program –Coordinate worldwide R & D efforts, in order to demonstrate and improve the performance, reduce the costs, attain the required reliability, etc. (Proposal Driven to GDE)

8. 22-July-05 HEP 2005 - Barish 8 GDE – Near Term Plan Schedule Begin to define Configuration (Aug 05) Baseline Configuration Document by end of 2005 ----------------------------------------------------------------------- Put Baseline under Configuration Control (Jan 06) Develop Reference Design Report by end of 2006 Three volumes -- 1) Reference Design Report; 2) Shorter glossy version for non-experts and policy makers ; 3) Detector Concept Report

9. 22-July-05 HEP 2005 - Barish 9 Snowmass Workshop – Aug 2005

10. 22-July-05 HEP 2005 - Barish 10 Snowmass – GDE Takes Over

11. 22-July-05 HEP 2005 - Barish 11 Design Issues

12. 22-July-05 HEP 2005 - Barish 12 Starting Point for the GDE Superconducting RF Main Linac

13. 22-July-05 HEP 2005 - Barish 13 Some Key Near-Term Design Choices Accelerating Gradient Positron Production mechanism Design of Damping ring Site-specific considerations: One or two tunnels? Shallow or deep?, etc Total cost will be a key determining factor in our ability to get the ILC built. Therefore cost optimization of all systems is of primary importance

14. 22-July-05 HEP 2005 - Barish 14 Towards the ILC Baseline Design

15. 22-July-05 HEP 2005 - Barish 15 Parameters for the ILC E cm adjustable from 200 – 500 GeV Luminosity  ∫ Ldt = 500 fb -1 in 4 years Ability to scan between 200 and 500 GeV Energy stability and precision below 0.1% Electron polarization of at least 80% The machine must be upgradeable to 1 TeV

16. 22-July-05 HEP 2005 - Barish 16 rf bands: L-band (TESLA)1.3 GHz  = 3.7 cm S-band (SLAC linac) 2.856 GHz1.7 cm C-band (JLC-C)5.7 GHz0.95 cm X-band (NLC/GLC)11.4 GHz0.42 cm (CLIC)25-30 GHz0.2 cm Accelerating structure size is dictated by wavelength of the rf accelerating wave. Wakefields related to structure size; thus so is the difficulty in controlling emittance growth and final luminosity.  Bunch spacing, train length related to rf frequency  Damping ring design depends on bunch length, hence frequency Specific Machine Realizations Frequency dictates many of the design issues for LC

17. 22-July-05 HEP 2005 - Barish 17 Cost Breakdown by Subsystem Civil SCRF Linac

18. 22-July-05 HEP 2005 - Barish 18 What Gradient to Choose?

19. 22-July-05 HEP 2005 - Barish 19 TESLA Cavity 9-cell 1.3GHz Niobium Cavity Reference design: has not been modified in 10 years ~1m

20. 22-July-05 HEP 2005 - Barish 20 (Improve surface quality -- pioneering work done at KEK) BCPEP Several single cell cavities at g > 40 MV/m 4 nine-cell cavities at ~35 MV/m, one at 40 MV/m Theoretical Limit 50 MV/m Electro-polishing

21. 22-July-05 HEP 2005 - Barish 21 Gradient Results from KEK-DESY collaboration must reduce spread (need more statistics) single-cell measurements (in nine-cell cavities)

22. 22-July-05 HEP 2005 - Barish 22 How Costs Scale with Gradient? Relative Cost Gradient MV/m 35MV/m is close to optimum Japanese are still pushing for 40- 45MV/m 30 MV/m would give safety margin C. Adolphsen (SLAC)

23. 22-July-05 HEP 2005 - Barish 23 Gradient

24. 22-July-05 HEP 2005 - Barish 24 Evolve the Cavities Minor Enhancement Low Loss Design Modification to cavity shape reduces peak B field. (A small Hp/Eacc ratio around 35Oe/(MV/m) must be designed). This generally means a smaller bore radius Trade-offs (Electropolishing, weak cell-to-cell coupling, etc) KEK currently producing prototypes

25. 22-July-05 HEP 2005 - Barish 25 New Cavity Design More radical concepts potentially offer greater benefits. But require time and major new infrastructure to develop. 28 cell Super-structure Re-entrant single-cell achieved 45.7 MV/m Q 0 ~10 10 (Cornell)

26. 22-July-05 HEP 2005 - Barish 26 Experimental Status single cell

27. 22-July-05 HEP 2005 - Barish 27 ILC Siting and Civil Construction The design is intimately tied to the features of the site –1 tunnels or 2 tunnels? –Deep or shallow? –Laser straight linac or follow earth’s curvature in segments? GDE ILC Design will be done to samples sites in the three regions –North American sample site will be near Fermilab –Japan and Europe are to determine sample sites by the end of 2005

28. 22-July-05 HEP 2005 - Barish 28 1 vs 2 Tunnels Tunnel must contain –Linac Cryomodule –RF system –Damping Ring Lines Save maybe $0.5M Issues –Maintenance –Safety –Duty Cycle

29. 22-July-05 HEP 2005 - Barish 29 Fermilab ILC Civil Program A Fermilab Civil Group is collaborating with SLAC Engineers and soon with Japanese and European engineers to develop methods of analyzing the siting issues and comparing sites. The current effort is not intended to select a potential site, but rather to understand from the beginning how the features of sites will effect the design, performance and cost

30. 22-July-05 HEP 2005 - Barish 30 Parameters of Positron Sources rep rate # of bunches per pulse # of positrons per bunch # of positrons per pulse TESLA TDR5 Hz28202 · 10 10 5.6 · 10 13 NLC120 Hz1920.75 · 10 10 1.4 · 10 12 SLC120 Hz15 · 10 10 DESY positron source 50 Hz11.5 · 10 9

31. 22-July-05 HEP 2005 - Barish 31 B=0.75 T 5 mm gap Conventional source Undulator-based source Positron source

32. 22-July-05 HEP 2005 - Barish 32 Laser Compton Source

33. 22-July-05 HEP 2005 - Barish 33

34. 22-July-05 HEP 2005 - Barish 34

35. 22-July-05 HEP 2005 - Barish 35

36. 22-July-05 HEP 2005 - Barish 36 Fast Kicker Development

37. 22-July-05 HEP 2005 - Barish 37 20 mrad ILC FF9 (x 4) tuneup dump lines ILC Strawman Layout Mark Woodley

38. 22-July-05 HEP 2005 - Barish 38 Beam Delivery Systems -- Challenges Transport the high-energy beam from the end of the main linac to the interaction point Transport the post-collision spent beam and beamstralung to the dumps Provide collimation for control of backgrounds Provide machine protection systems for errant beams Provide collision point maintenance through the use of fast feedback systems (inter-train and intra-train)

39. 22-July-05 HEP 2005 - Barish 39 Accelerator Physics Challenges Develop High Gradient Superconducting RF systems –Requires efficient RF systems, capable of accelerating high power beams (~MW) with small beam spots(~nm). Achieving nm scale beam spots –Requires generating high intensity beams of electrons and positrons –Damping the beams to ultra-low emittance in damping rings –Transporting the beams to the collision point without significant emittance growth or uncontrolled beam jitter –Cleanly dumping the used beams. Reaching Luminosity Requirements –Designs satisfy the luminosity goals in simulations –A number of challenging problems in accelerator physics and technology must be solved, however.

40. 22-July-05 HEP 2005 - Barish 40 Test Facility at SLAC

41. 22-July-05 HEP 2005 - Barish 41 TESLA Test Facility Linac - DESY laser driven electron gun photon beam diagnostics undulator bunch compressor superconducting accelerator modules pre- accelerator e - beam diagnostics 240 MeV120 MeV16 MeV4 MeV

42. 22-July-05 HEP 2005 - Barish 42 Fermilab ILC SCRF Program

43. 22-July-05 HEP 2005 - Barish 43 Test Facility at KEK

44. 22-July-05 HEP 2005 - Barish 44 Beam Detector Interface Tauchi LCWS05

45. 22-July-05 HEP 2005 - Barish 45 Three concepts under study Typically requires factors of two improvement in granularity, resolution, etc. from present generation detectors Focused R&D program required to develop the detectors -- end of 2005 Detector Concepts will be used to simulate performance of reference design vs physics goals next year. Detector Concepts and Challenges

46. 22-July-05 HEP 2005 - Barish 46 The Machine Accelerator baseline configuration will be determined and documented (BCD) by the end of 2005 R&D program and priorities determined (proposal driven) Baseline configuration will be the basis of a reference design done in 2006 The Detector(s) Determine features, scope: one or two, etc (same time scale) Measure performance of the baseline design Beam delivery system and machine detector interfaces Define and motivate the future detector R&D program The GDE Plan

47. 22-July-05 HEP 2005 - Barish 47  The effort to make a global design for the linear collider is underway. choice of technology for main linac made the global design effort is underway baseline will be determined by the end of 2005 reference design next year (with costs) technical design will follow  We are on track produce a solid design and proposal to build an International Linear Collider within the next few years. Conclusions