OLAV-III 1 Barry Barish OLAV-III Oak Ridge National Laboratory 12-July-11 The International Linear Collider A TeV Scale Lepton Collider 12-Julyl-11 ORNL

OLAV-III 22 Why a Linear Collider? Terascale science and how the ILC will complement the LHC? Why linear? What technology to employ? A thumbnail description of the ILC Reference Design and Costs? The ILC Vacuum Systems Present program and plans

12-Julyl-11 ORNL OLAV-III 33 Three Generations: Complementarity Discovery Of Charm Particles and 3.1 GeV Burt Richter Nobel Prize SPEAR at SLAC First generation

12-Julyl-11 ORNL OLAV-III 44 Rich History of Discovery DESY PETRA Collider Second generation

OLAV-III 55 Precision Measurements CERN’s LEP Collider set the stage for Terascale physics Reveal the origin of quark and lepton mass Produce dark matter in the laboratory Test exotic theories of space and time Third generation 12-Julyl-11 ORNL

OLAV-III 66 SPEAR PETRA LEP ENERGY YEAR TeV ILC GeV Fourth generation? Three Generations of Successful e + e - Colliders The Energy Frontier

12-Julyl-11 ORNL OLAV-III 77 Exploring the Terascale The tools The LHC –It will lead the way and has large reach –Quark-quark, quark-gluon and gluon-gluon collisions at TeV –Broadband initial state The ILC –A second view with high precision –Electron-positron collisions with fixed energies, adjustable between 0.1 and 1.0 TeV –Well defined initial state Together, these are our tools for the Terascale

12-Julyl-11 ORNL OLAV-III 88 Why e + e - collisions? Elementary particles Well-defined –energy –angular momentum Uses full COM energy Produces particles democratically Can mostly fully reconstruct events

12-Julyl-11 ORNL OLAV-III 9 Comparison: ILC and LHC ILC LHC Beam Particle : Electron x Positron Proton x Proton CMS Energy : 0.5 – 1 TeV 14 TeV Luminosity Goal : 2 x /cm 2 /sec 1 x10 34 /cm 2 /sec Accelerator Type : Linear Circular Storage Rings Technology : Supercond. RF Supercond. Magnet

12-Julyl-11 ORNL OLAV-III 10 LHC ILC e + e –  Z H Z  e + e –, H  b … Higgs event simulation comparison

12-Julyl-11 ORNL OLAV-III 11 Higgs Signal with LHC  Rare decay channel: BR~10 -3  Projected signal and background after data cuts to optimize signal to background  Background large: S/B  1:20, but can estimate from non signal areas CMS

12-Julyl-11 ORNL OLAV-III 12 Precision Higgs physics  Model-independent Studies mass absolute branching ratios total width spin top Yukawa coupling self coupling  Precision Measurements Garcia-Abia et al

12-Julyl-11 ORNL OLAV-III 13 Higgs Coupling-mass relation Remember - the Higgs is a Different! It is a zero spin particle that fills the vacuum It couples to mass; masses and decay rates are related

12-Julyl-11 ORNL OLAV-III 14 The linear collider will measure the spin of any Higgs it can produce by measuring the energy dependence from threshold ILC: Is it really the Higgs ? Measure the quantum numbers. The Higgs must have spin zero !

12-Julyl-11 ORNL OLAV-III 15 What can we learn from the Higgs? Precision measurements of Higgs coupling Higgs Coupling strength is proportional to Mass

12-Julyl-11 ORNL OLAV-III 16 e + e - : Studying the Higgs determine the underlying model SM 2HDM/MSSM Yamashita et al Zivkovic et al

12-Julyl-11 ORNL OLAV-III 17 Possible TeV Scale Lepton Colliders ILC < 1 TeV Technically possible ~ QUAD POWER EXTRACTION STRUCTURE BPM ACCELERATING STRUCTURES CLIC < 3 TeV Feasibility? Longer timescale Main beam – 1 A, 200 ns from 9 GeV to 1.5 TeV Drive beam - 95 A, 300 ns from 2.4 GeV to 240 MeV Muon Collider < 4 TeV FEASIBILITY?? Much longer timescale Much R&D Needed Neutrino Factory R&D + bunch merging much more cooling etc ILC CLIC Muon Collider

OLAV-III 18  E ~ (E 4 /m 4 R) Linear implies single pass cost Energy Circular Collider Linear Collider R Synchrotron Radiation R ~ 200 GeV < 5 nm vertical Low emittance (high brightness) machine optics Contain emittance growth Squeeze the beam as small as possible at collision point 12-Julyl-11 ORNL

OLAV-III 19 ILC – Underlying Technology Room temperature copper structures OR Superconducting RF cavities

12-Julyl-11 ORNL OLAV-III 20 SCRF Technology Recommendation The recommendation of ITRP was presented to ILCSC & ICFA on August 19, 2004 in a joint meeting in Beijing. 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). This led to the formation of the Global Design Effort (GDE) ICFA unanimously endorsed the ITRP’s recommendation on August 20, 2004 Strong international interest in developing SCRF technology

12-Julyl-11 ORNL OLAV-III 21 GDE -- Designing a Linear Collider Superconducting RF Main Linac

12-Julyl-11 ORNL OLAV-III 22 ILC Baseline Design Gev e+ e- Linear Collider Energy 250 Gev x 250 Gev Length km # of RF units 560 # of cryomodules1680 # of 9-cell cavities Detectors push-pull 2e34 peak luminosity 5 Hz rep rate, > 6000 bunches per cycle IP spots sizes:  x 350 – 620 nm;  y 3.5 – 9.0 nm

12-Julyl-11 ORNL OLAV-III 23 RDR Complete Reference Design Report (4 volumes) Executive Summary Physics at the ILC Accelerator Detectors

12-Julyl-11 ORNL OLAV-III 24 RDR Design Parameters Max. Center-of-mass energy500GeV Peak Luminosity~2x /cm 2 s Beam Current9.0mA Repetition rate5Hz Average accelerating gradient31.5MV/m Beam pulse length0.95ms Total Site Length31km Total AC Power Consumption~230MW

12-Julyl-11 ORNL OLAV-III 25 LHC --- Deep Underground

12-Julyl-11 ORNL OLAV-III 26 ILC --- Deep Underground

12-Julyl-11 ORNL OLAV-III 27 LHC --- Superconducting Magnet

12-Julyl-11 ORNL OLAV-III 28 ILC - Superconducting RF Cryomodule

12-Julyl-11 ORNL OLAV-III 29 Proposed Design changes for TDR RDRSB2009 Single Tunnel for main linac Move positron source to end of linac *** Reduce number of bunches factor of two (lower power) ** Reduce size of damping rings (3.2km) Integrate central region Single stage bunch compressor

ILC Vacuum Systems 12-Julyl-11 ORNL OLAV-III 30 ~ 80 km of beamline is under vacuum Challenges, but good experience base from other accelerators Most complex is the vacuum systems for 1680 cryomodules for main linac and other beam line systems These cryogenic units require separate vacuum systems for the beam line, the insulating vacuum and the waveguides.

Other vacuum challenges The lifetime of the electron source photocathode requires a vacuum in the range of a pico-Torr. The superconducting undulator for the positron source is a warm bore chamber with a very small aperture. Chambers for bending magnets in the damping rings and elsewhere require antechambers and photon absorbers for the synchrotron radiation. The presence of electron cloud in the positron damping ring and ions in the electron damping ring can seriously impact performance and requires mitigation. Beam-gas scattering in the beam delivery must be limited to reduce backgrounds in the experimental detectors. 12-Julyl-11 ORNL OLAV-III 31

12-Julyl-11 ORNL OLAV-III 32 The ILC SCRF Cavity - Achieve high gradient (35MV/m); develop multiple vendors; make cost effective, etc - Focus is on high gradient; production yields; cryogenic losses; radiation; system performance

12-Julyl-11 ORNL OLAV-III 33 Global Plan for SRF R&D Year Phase TDP-1TDP-2 Cavity Gradient in v. test to reach 35 MV/m  Yield 50%  Yield 90% Cavity-string to reach 31.5 MV/m, with one- cryomodule Global effort for string assembly and test (DESY, FNAL, INFN, KEK) System Test with beam acceleration FLASH (DESY), NML (FNAL) STF2 (KEK, test start in 2013) Preparation for Industrialization Production Technology R&D

12-Julyl-11 ORNL OLAV-III 34 Cavity Gradient Milestone Achieved 2010 Milestone TDR Goal

12-Julyl-11 ORNL OLAV-III 35 Test Facilities: FLASH SCRF accelerator tests

12-Julyl-11 ORNL OLAV-III 36 TTF/FLASH 9mA Experiment

Example Experimental Results Flat gradient solution achieved –4.5 mA beam Characterisation of solution by scanning beam current –model benchmarking Beam Current (mA) Gradient change over 400us (%) Gradient Tilts vs Beam Current (ACC7) Intended working point ~2.5% 12-Julyl-11 ORNL OLAV-III 37

FLASH: Stability 15 consecutive studies shifts (120hrs), and with no downtime Time to restore 400us bunch- trains after beam-off studies: ~10mins Energy stability with beam loading over periods of hours: ~0.02% Individual cavity “tilts” equally stable Energy stability over 3hrs with 4.5mA ~0.02% pk-pk 9 Feb Julyl-11 ORNL OLAV-III 38

ILC Cryomodules There are ∼ 20 km of cryomodules in the main linac and another ∼ 1.6 km of modules in the sources and bunch compressors. Each cryomodule has separate vacuum systems for the accelerating structures, the insulating vacuum and the transmission waveguides. 12-Julyl-11 ORNL OLAV-III 39 ILC Cryomodule cross-section

ILC Cryomodules The structure vacuum vessel holds the niobium cavities and is at 2K cryogenic temperature, and this system must produce very low quantities of particulates as these can contaminate the cavities causing field emission and lowering the available gradient. The system must also be able to produce ultra-high vacuum at room temperature to eliminate the risk of residual gases condensing on the niobium walls during cooldown. 12-Julyl-11 ORNL OLAV-III 40

ILC Cryomodules The beamline vacuum is segmented into strings of m. –Each string has an insulating vacuum break and a port for valves and ion pumps. –Every other string has additional valves, pumps, leak detection, and vacuum diagnostics. –Each group of 4 strings (617 m) has cold vacuum isolation valves. 12-Julyl-11 ORNL OLAV-III 41

ILC Cryomodules Much of the transmission waveguide vacuum is at room temperature, but it must transition to helium temperatures at the couplers. In addition, the rf power being transmitted is very high, so multipactoring and arcing must be considered in the design. There is a valve for each coupler. Every cryomodule has an ion pump and titanium sublimation pump, and every 3 cryomodules have a turbomolecular pump, a scroll fore pump and a leak detector. 12-Julyl-11 ORNL OLAV-III 42

Electron Source The polarized electron source is a DC gun with a laser illuminated photocathode(GaAs/GaAsP) similar to the electron guns at SLAC and Jefferson Lab. To maintain photocathode lifetime, the pressure must be < 3×10 −11 torr. This is achieved by incorporating large ion pumps and non-evaporable getter (NEG) pumps. 12-Julyl-11 ORNL OLAV-III 43

12-Julyl-11 ORNL OLAV-III 44 Test Facilities: Cesr-TA eCloud broad accelerator applications

12-Julyl-11 ORNL OLAV-III 45 Mitigating Electron Cloud Simulations – electrodes; coating and/or grooving vacuum pipe Demonstration at CESR critical tests eCloud R&D

12-Julyl-11 ORNL OLAV-III 46

12-Julyl-11 ORNL OLAV-III 47 CesrTA - Wiggler Observations IWLC CERN, Geneva, Switzerland 0.002” radius Electrode  best performance

12-Julyl-11 ORNL OLAV-III 48 Field Region Baseline Mitigation Recommendation Alternatives for Further Investigation Drift*TiN CoatingSolenoid WindingsNEG Coating DipoleGrooves with TiN Coating Antechambers for power loads and photoelectron control R&D into the use of clearing electrodes. Quadrup ole* TiN Coating R&D into the use of clearing electrodes or grooves with TiN coating WigglerClearing Electrodes Antechambers for power loads and photoelectron control Grooves with TiN Coating Proposed ILC Mitigation Scheme

Beam Delivery System The beam delivery system transport requires special attention to limit backgrounds in the experimental detectors. In order to reduce the residual beam-gas scattering to acceptable levels, the line pressure near the interaction region needs to be <1 nTorr. The design is complicated by the requirement for small chamber diameters. The small chamber diameter and the low pressure require close spacing of the ion pumps, bake-outs and the use of NEG coated chambers.. 12-Julyl-11 ORNL OLAV-III 49

12-Julyl-11 ORNL OLAV-III 50 Test Facilities: ATF-2 large international collaboration

ATF2 Goals: A. Achievement of 37nm beam size A1) Demonstration of a new compact final focus system; –proposed by P.Raimondi and A.Seryi in 2000, A2) Maintenance of the small beam size –(several hours at the FFTB/SLAC) B. Control of the beam position B1) Demonstration of beam orbit stabilization with nano- meter precision at IP. –(The beam jitter at FFTB/SLAC was about 40nm.) B2) Establishment of beam jitter controlling technique at nano-meter level with ILC-like beam 12-Julyl-11 ORNL OLAV-III 51

12-Julyl-11 ORNL OLAV-III 52 ATF2 – Beam size/stability and kicker tests IPShintake Monitor Final Doublet

12-Julyl-11 ORNL OLAV-III 53 KEK ATF-2 Studies (Beam Sizes at Collision)

54 12-Julyl-11 ORNL OLAV-III

ATF / ATF2 After Earthquake? 12-Julyl-11 ORNL OLAV-III 55

12-Julyl-11 ORNL OLAV-III 56 Push – Pull Detector Concept Vibration stability will be one of the major criteria in eventual selection of a motion system design Both detectors without platformsBoth detectors with platforms

12-Julyl-11 ORNL OLAV-III 57 Interaction Region (old location) Break point for push-pull disconnect Provide reliable collisions of 5nm-small beams, with acceptable level of background, and be able to rapidly and efficiently exchange ~10kT detectors in a push-pull operation several times per year

OLAV-III 58 Final Reflections The energy frontier continues to be the primary tool to explore the central issues in particle physics The LHC at CERN will open the 1 TeV energy scale and we anticipate exciting new discoveries A companion lepton collider will be the logical next step, but such a machine has technical challenges and needs significant R&D and design now LHC results will inform the final design and even whether a higher energy options is needed, If so, this may also be possible, but on a longer time scale. 12-Julyl-11 ORNL