Personal Perspectives on the ITRP Recommendation and on the Next Steps Toward the International Linear Collider

1. Personal Perspectives on the ITRP Recommendation and on the Next Steps Toward the International Linear Collider Barry Barish PAC Annual Meeting Knoxville, Tennessee 16-May-05

2. Why e+e- Collisions? • elementary particles • well-defined • energy, • angular momentum • uses full COM energy • produces particles democratically • can mostly fully reconstruct events PAC 05 - Barish

3. A Rich History as a Powerful Probe PAC 05 - Barish

4. The Energy Frontier PAC 05 - Barish

5. Why a TeV Scale? • Two parallel developments over the past few years (the science & the technology) • The precision information e+e- and n data at present energies have pointed to a low mass Higgs; Understanding electroweak symmetry breaking, whether supersymmetry or an alternative, will require precision measurements. • There are strong arguments for the complementarity between a ~0.5-1.0 TeV ILC and the LHC science. PAC 05 - Barish

6. Electroweak Precision Measurements e+e+ and neutrino scattering results at present energies strongly point to a low mass Higgs and an energy scale for new physics < 1TeV PAC 05 - Barish

7. Why a TeV Scale e+e- Accelerator? • Two parallel developments over the past few years (the science & the technology) • The precision information from LEP and other data have pointed to a low mass Higgs; Understanding electroweak symmetry breaking, whether supersymmetry or an alternative, will require precision measurements. • There are strong arguments for the complementarity between a ~0.5-1.0 TeV LC and the LHC science. PAC 05 - Barish

8. LHC/ILC Complementarity Linear Collider Spin Measurement The Higgs must be spin zero LHC should discover the Higgs The linear collider should measure its spin The process e+e–HZ can be used to measure the spin of a 120 GeV Higgs particle. PAC 05 - Barish

9. Linear collider LHC/ILC Complementarity Extra Dimensions Map extra dimensions: study the emission of gravitons into the extra dimensions, together with a photon or jets emitted into the normal dimensions. PAC 05 - Barish

10. Why a TeV Scale e+e- Accelerator? • Two parallel developments over the past few years (the science & the technology) • Designs and technology demonstrations have matured on two technical approaches for an e+e- collider that are well matched to our present understanding of the physics. PAC 05 - Barish

11. GLC/NLC Concept GLC • The main linacs operate at an unloaded gradient of 65 MV/m, beam-loaded to 50 MV/m. • The rf systems for 500 GeV c.m. consist of 4064 75 MW Periodic Permanent Magnet (PPM) klystrons arranged in groups of 8, followed by 2032 SLED-II rf pulse compression systems PAC 05 - Barish

12. TESLA Concept • The main linacs based on 1.3 GHz superconducting technology operating at 2 K. • The cryoplant, is of a size comparable to that of the LHC, consisting of seven subsystems strung along the machines every 5 km. PAC 05 - Barish

13. Which Technology to Chose? • Two alternate designs -- “warm” and “cold” had come to the stage where the show stoppers had been eliminated and the concepts were well understood. • A major step toward a new international machine required uniting behind one technology, and then working toward a unified global design based on the recommended technology. PAC 05 - Barish

14. ICFA/ILCSC Evaluation of the Technologies The Report Validates the Readiness of L-band and X-band Concepts BUT, IT DID NOT MAKE A CHOICE PAC 05 - Barish

15. International Technology Review Panel PAC 05 - Barish

16. The Charge to the International Technology Recommendation Panel General Considerations The International Technology Recommendation Panel (the Panel) should recommend a Linear Collider (LC) technology to the International Linear Collider Steering Committee (ILCSC). On the assumption that a linear collider construction commences before 2010 and given the assessment by the ITRC that both TESLA and JLC-X/NLC have rather mature conceptual designs, the choice should be between these two designs. If necessary, a solution incorporating C-band technology should be evaluated. Note -- We interpreted our charge as being to recommend a technology, rather than choose a design PAC 05 - Barish

17. ITRP Schedule of Events Tutorial & Planning • Six Meetings • RAL (Jan 27,28 2004) • DESY (April 5,6 2004) • SLAC (April 26,27 2004) • KEK (May 25,26 2004) • Caltech (June 28,29,30 2004) • Korea (August 11,12,13) • ILCSC / ICFA (Aug 19) • ILCSC (Sept 20) Site Visits Deliberations Recommendation Exec. Summary Final Report PAC 05 - Barish

18. Evaluate a Criteria Matrix • The panel analyzed the technology choice through studying a matrix having six general categories with specific items under each: • the scope and parameters specified by the ILCSC; • technical issues; • cost issues; • schedule issues; • physics operation issues; • and more general considerations that reflect the impact of the LC on science, technology and society PAC 05 - Barish

19. The 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). • The superconducting technology has several very nice features for application to a linear collider. They follow in part from the low rf frequency. PAC 05 - Barish

20. Some Features of SC Technology • The large cavity aperture and long bunch interval reduce the complexity of operations, reduce the sensitivity to ground motion, permit inter-bunch feedback and may enable increased beam current. • The main linac rf systems, the single largest technical cost elements, are of comparatively lower risk. • The construction of the superconducting XFEL free electron laser will provide prototypes and test many aspects of the linac. • The industrialization of most major components of the linac is underway. • The use of superconducting cavities significantly reduces power consumption. PAC 05 - Barish

21. The Technology Recommendation • The recommendation was presented to ILCSC & ICFA on August 19 in a joint meeting in Beijing. • ICFA unanimously endorsed the ITRP’s recommendation on August 20 PAC 05 - Barish

22. The Community then Self-Organized Nov 13-15, 2004 PAC 05 - Barish

23. The First ILC Meeting at KEK PAC 05 - Barish

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

25. GDE – Near Term Plan • Staff the GDE • Administrative, Communications, Web staff • Regional Directors (each region) • Engineering/Costing Engineer (each region) • Civil Engineer (each region) • Key Experts for the GDE design staff from the world community (please give input) • Fill in missing skills (later) Total staff size about 20 FTE (2005-2006) PAC 05 - Barish

26. 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 Conceptual Design Report by end of 2006 • Three volumes -- 1) Conceptual Design Report; 2) Shorter glossy version for non-experts and policy makers ; 3) Detector Concept Report PAC 05 - Barish

27. 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. • Make Website, coordinate meetings, collaborative R&D, 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) PAC 05 - Barish

28. Starting Point for the GDE Superconducting RF Main Linac PAC 05 - Barish

29. Parameters for the ILC • Ecm 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 PAC 05 - Barish

30. Experimental Test Facility - KEK • Prototype Damping Ring for X-band Linear Collider • Development of Beam Instrumentation and Control PAC 05 - Barish

31. Final Focus Test Faclity - SLAC PAC 05 - Barish

32. e- beam diagnostics e- beam diagnostics bunch compressor laser driven electron gun undulator photon beam diagnostics pre-accelerator superconducting accelerator modules TESLA Test Facility Linac - DESY 240 MeV 120 MeV 16 MeV 4 MeV PAC 05 - Barish

33. Towards the ILC Baseline Design PAC 05 - Barish

34. Specific Machine Realizations • rf bands: • L-band (TESLA) 1.3 GHz l = 3.7 cm • S-band (SLAC linac) 2.856 GHz 1.7 cm • C-band (JLC-C) 5.7 GHz 0.95 cm • X-band (NLC/GLC) 11.4 GHz 0.42 cm • (CLIC) 25-30 GHz 0.2 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 Frequency dictates many of the design issues for LC PAC 05 - Barish

35. Cost Breakdown by Subsystem Civil SCRF Linac PAC 05 - Barish

36. RF Accelerating Structures Accelerating structures must support the desired gradient in an operational setting and there must be a cost effective means of fabrication. ~17,000 accelerating cavities/500 GeV Current performance goal is 35 MV/m, (operating at 30 MV/m) Trade-off cost and technical risk. RF SC Linac ChallengesEnergy: 500 GeV, upgradeable to 1000 GeV ~Theoretical Max Cost 1 m Risk PAC 05 - Barish

37. Electro-polishing (Improve surface quality -- pioneering work done at KEK) BCP EP • 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 PAC 05 - Barish

38. Gradient Results from KEK-DESY collaboration must reduce spread (need more statistics) single-cell measurements (in nine-cell cavities) PAC 05 - Barish

39. New Cavity Shape for Higher Gradient? TESLA Cavity Alternate Shapes • A new cavity shape with a small Hp/Eacc ratio around • 35Oe/(MV/m) must be designed. • - Hp is a surface peak magnetic field and Eacc is the electric • field gradient on the beam axis. • - For such a low field ratio, the volume occupied by magnetic • field in the cell must be increased and the magnetic density • must be reduced. • - This generally means a smaller bore radius. • - There are trade-offs (eg. Electropolishing, weak cell-to-cell • coupling, etc) PAC 05 - Barish

40. Parameters of Positron Sources PAC 05 - Barish

41. Positron Source • Large amount of charge to produce • Three concepts: • undulator-based (TESLA TDR baseline) • ‘conventional’ • laser Compton based PAC 05 - Barish

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45. Strawman Final Focus PAC 05 - Barish

46. Conclusions • Remarkable progress in the past two years toward realizing an international linear collider: important R&D on accelerator systems definition of parameters for physics choice of technology start the global design effort funding agencies are engaged • Many major hurdles remain before the ILC becomes a reality (funding, site, international organization, detailed design, …), but there is increasing momentum toward the ultimate goal --- An International Linear Collider. PAC 05 - Barish