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

22-July-05 HEP 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).

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

22-July-05 HEP 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

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

22-July-05 HEP 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 ( )

22-July-05 HEP 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)

22-July-05 HEP Barish 8 GDE – Near Term Plan Schedule Begin to define Configuration (Aug 05) Baseline Configuration Document by end of 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

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

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

22-July-05 HEP Barish 11 Design Issues

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

22-July-05 HEP 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

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

22-July-05 HEP 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

22-July-05 HEP Barish 16 rf bands: L-band (TESLA)1.3 GHz  = 3.7 cm S-band (SLAC linac) 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

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

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

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

22-July-05 HEP 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

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

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

22-July-05 HEP Barish 23 Gradient

22-July-05 HEP 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

22-July-05 HEP 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)

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

22-July-05 HEP 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

22-July-05 HEP 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

22-July-05 HEP 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

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

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

22-July-05 HEP Barish 32 Laser Compton Source

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22-July-05 HEP Barish 36 Fast Kicker Development

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

22-July-05 HEP 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)

22-July-05 HEP 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.

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

22-July-05 HEP 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

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

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

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

22-July-05 HEP 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

22-July-05 HEP 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

22-July-05 HEP 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