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

PAC 05 - Barish2 Why e + e - Collisions? elementary particles well-defined –energy, –angular momentum uses full COM energy produces particles democratically can mostly fully reconstruct events

16-May-05PAC 05 - Barish3 A Rich History as a Powerful Probe

16-May-05PAC 05 - Barish4 The Energy Frontier

16-May-05PAC 05 - Barish5 Why a TeV Scale? Two parallel developments over the past few years ( the science & the technology) –The precision information e + e - and 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 ~ TeV ILC and the LHC science.

16-May-05PAC 05 - Barish6 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

16-May-05PAC 05 - Barish7 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 ~ TeV LC and the LHC science.

16-May-05PAC 05 - Barish8 Linear Collider Spin Measurement LHC should discover the Higgs The linear collider should measure its spin LHC/ILC Complementarity The process e + e –  HZ can be used to measure the spin of a 120 GeV Higgs particle. The Higgs must be spin zero

16-May-05PAC 05 - Barish9 Extra Dimensions Linear collider LHC/ILC Complementarity Map extra dimensions: study the emission of gravitons into the extra dimensions, together with a photon or jets emitted into the normal dimensions.

16-May-05PAC 05 - Barish10 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.

16-May-05PAC 05 - Barish11 GLC GLC/NLC Concept 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 MW Periodic Permanent Magnet (PPM) klystrons arranged in groups of 8, followed by 2032 SLED-II rf pulse compression systems

16-May-05PAC 05 - Barish12 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.

16-May-05PAC 05 - Barish13 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.

16-May-05PAC 05 - Barish14 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

16-May-05PAC 05 - Barish15 International Technology Review Panel

16-May-05PAC 05 - Barish16 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

16-May-05PAC 05 - Barish17 ITRP Schedule of Events Six Meetings –RAL (Jan 27, ) –DESY (April 5,6 2004) –SLAC (April 26, ) –KEK (May 25, ) –Caltech (June 28,29, ) –Korea (August 11,12,13) –ILCSC / ICFA (Aug 19) –ILCSC (Sept 20) Tutorial & Planning Site Visits Deliberations Exec. Summary Final Report Recommendation

16-May-05PAC 05 - Barish18 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

16-May-05PAC 05 - Barish19 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.

16-May-05PAC 05 - Barish20 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.

16-May-05PAC 05 - Barish21 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

16-May-05PAC 05 - Barish22 The Community then Self-Organized Nov 13-15, 2004

16-May-05PAC 05 - Barish23 The First ILC Meeting at KEK

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

16-May-05PAC 05 - Barish25 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 ( )

16-May-05PAC 05 - Barish26 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 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

16-May-05PAC 05 - Barish27 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)

16-May-05PAC 05 - Barish28 Starting Point for the GDE Superconducting RF Main Linac

16-May-05PAC 05 - Barish29 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-May-05PAC 05 - Barish30 Experimental Test Facility - KEK Prototype Damping Ring for X-band Linear Collider Development of Beam Instrumentation and Control

16-May-05PAC 05 - Barish31 Final Focus Test Faclity - SLAC

16-May-05PAC 05 - Barish32 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

16-May-05PAC 05 - Barish33 Towards the ILC Baseline Design

16-May-05PAC 05 - Barish34 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

16-May-05PAC 05 - Barish35 Cost Breakdown by Subsystem Civil SCRF Linac

16-May-05PAC 05 - Barish36 RF SC Linac Challenges Energy: 500 GeV, upgradeable to 1000 GeV 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. 1 m Risk Cost~Theoretical Max

16-May-05PAC 05 - Barish37 (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

16-May-05PAC 05 - Barish38 Gradient Results from KEK-DESY collaboration must reduce spread (need more statistics) single-cell measurements (in nine-cell cavities)

16-May-05PAC 05 - Barish39 New Cavity Shape for Higher Gradient? TESLA Cavity 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) Alternate Shapes

16-May-05PAC 05 - Barish40 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

16-May-05PAC 05 - Barish41 Positron Source Large amount of charge to produce Three concepts: –undulator-based (TESLA TDR baseline) –‘conventional’ –laser Compton based

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16-May-05PAC 05 - Barish45 Strawman Final Focus

16-May-05PAC 05 - Barish46 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. Conclusions