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TRANSCRIPT
The Path Toward a Linear Collider
Barry BarishHEP 2005
Lisbon, Portugal 23-July-05
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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).
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The Community then Self-Organized
Nov 13-15, 2004
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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 Stanfordin March 2005 when I became director of the GDE
Technically Driven Schedule
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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)
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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), FumihikoTakasaki (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)
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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
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Snowmass Workshop – Aug 2005
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Snowmass – GDE Takes Over
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Design Issues
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main linacbunchcompressor
dampingring
source
pre-accelerator
collimation
final focus
IP
extraction& dump
KeV
few GeV
few GeVfew GeV
250-500 GeV
Starting Point for the GDE
Superconducting RF Main Linac
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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
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Towards the ILC Baseline Design
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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
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rf bands:
L-band (TESLA) 1.3 GHz λ = 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 rfaccelerating 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
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Cost Breakdown by Subsystem
cf31%
structures18%rf
12%
systems_eng8%
installation&test7%
magnets6%
vacuum4%
controls4%
cryo4%
operations4%
instrumentation2%
Civil
SCRF Linac
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What Gradient to Choose?
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TESLA Cavity
9-cell 1.3GHz Niobium Cavity
Reference design: has not been modified in 10 years
~1m
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(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
Electro-polishing
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Gradient
Results from KEK-DESY collaboration
must reduce spread (need more statistics)
single
-cel
l m
easu
rem
ents
(in
nin
e-ce
ll ca
vities
)
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How Costs Scale with Gradient?
Relative C
ost
Gradient MV/m
2
0
$ l inc ryo
a GbG Q
≈ +
35MV/m is close to optimum
Japanese are still pushing for 40-45MV/m
30 MV/m would give safety margin
C. Adolphsen (SLAC)
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Gradient
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Evolve the CavitiesMinor Enhancement
Low Loss Design
Modification to cavity shape reduces peak B field. (Asmall 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
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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 achieved45.7 MV/m Q0 ~1010
(Cornell)
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Experimental Status
single cell
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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
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1 vs 2 Tunnels• Tunnel must contain
– Linac Cryomodule– RF system– Damping Ring Lines
• Save maybe $0.5M
• Issues– Maintenance– Safety– Duty Cycle
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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
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Parameters of Positron Sources
1.5 · 1091.5 · 109150 HzDESY positron source
5 · 10105 · 10101120 HzSLC
1.4 · 10120.75 · 1010192120 HzNLC
5.6 · 10132 · 101028205 HzTESLA TDR
# of positrons per pulse
# of positrons per bunch
# of bunches per pulserep rate
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B=0.75 T5 mm gap
Conventional source
Undulator-based source
Positronsource
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Laser Compton Source
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Fast Kicker Development
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20 mrad ILC FF9 (x 4)
tuneupdump lines
ILC Strawman Layout
Mark Woodley
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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)
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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.
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Test Facility at SLAC
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TESLA Test Facility Linac - DESY
laser driven electron gun
photon beam diagnostics
undulatorbunch
compressor
superconducting accelerator modules
pre-accelerator
e- beam diagnostics
e- beam diagnostics
240 MeV 120 MeV 16 MeV 4 MeV
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Fermilab ILC SCRF Program
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Test Facility at KEK
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Beam Detector Interface
TauchiLCWS05
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• 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
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• 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
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The effort to make a global design for the linear collider is underway.
choice of technology for main linac madethe global design effort is underwaybaseline will be determined by the end of 2005reference 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