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Report from the GDE. Barry Barish ACFA Workshop EXCO, Daegu, Korea 11-July-05. The Energy Frontier. issued on Nov. 3, 2004 at the 9th Plenary ACFA.

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report from the gde
Report from the GDE

Barry Barish

ACFA Workshop

EXCO, Daegu, Korea



The Energy Frontier

ACFA Workshop - Barish


issued on Nov. 3, 2004 at the 9th Plenary ACFA

  • In August 2004, ICFA has decided on superconducting technology for the future linear collider (LC), by endorsing the resolution of the international technology recommendation panel (ITRP) created by ILCSC under ICFA. The ITRP report emphasizes the importance of world-wide unified approach as a single team to design the international linear collider (ILC).
  • ACFA has discussed various issues relating to ILC in the plenary meeting of ACFA at VECC, Kolkata in India on 2-3 Nov. 2004, and ACFA came to the following conclusions
    • ACFA welcomes the truly international nature of the decision on technology for the ILC. This sets the stage for international collaboration in the design efforts for the ILC.
    • ACFA reaffirms that the ILC, the next major high-energy physics project, should be realized by world-wide efforts. In such International collaboration ACFA and scientists in ACFA countries should play crucial and leading roles.
    • ACFA reconfirms the importance of hosting ILC in Asia, which will make high energy physics and accelerator science truly global.

ACFA Workshop - Barish


ACFA urges the Japanese Government to fully support the efforts of KEK and Japanese scientists to host the ILC in Japan.

    • ACFA reconfirms that KEK is the best suited institute in Asia for hosting the Central Team of GDI.
    • ACFA urges KEK to establish the Asian Regional Center for R&D in GDI and encourages other Asian countries to actively participate in GDI.
    • With ILC entering this important phase, ACFA urges Governments of Asian countries to support participation of their scientists in GDI.
  • ACFA feels that Asia has wide expertise in accelerator technology which can be directed to develop SCRF technology required for the ILC, and large trained manpower which can make major contributions to the ILC. Because ILC will pose major scientific and technical challenges, there will be several technological fallouts. ACFA therefore feels that by participating in the ILC not only the scientific community of the participating country but also its industry will benefit.

ACFA Workshop - Barish


The Community then Self-Organized

Nov 13-15, 2004

ACFA Workshop - Barish


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

ACFA Workshop - Barish

the global design effort

Formal organization begun at LCWS 05 at Stanford

in March 2005 when I became director of the GDE

The Global Design Effort

Technically Driven Schedule

gde near term plan
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)

ACFA Workshop - Barish

gde near term plan1
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), offered to 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)

ACFA Workshop - Barish

gde near term plan2
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

ACFA Workshop - Barish


Starting Point for the GDE

Superconducting RF Main Linac

ACFA Workshop - Barish

some key near term design choices
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

ACFA Workshop - Barish

towards the ilc baseline design
Towards the ILC Baseline Design

ACFA Workshop - Barish

parameters for the ilc
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

ACFA Workshop - Barish


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

ACFA Workshop - Barish

cost breakdown by subsystem
Cost Breakdown by Subsystem


SCRF Linac

ACFA Workshop - Barish

what gradient to choose
What Gradient to Choose?

ACFA Workshop - Barish

tesla cavity
TESLA Cavity


9-cell 1.3GHz Niobium Cavity

Reference design: has not been modified in 10 years

ACFA Workshop - Barish



(Improve surface quality -- pioneering work done at KEK)



  • 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

ACFA Workshop - Barish


Results from KEK-DESY collaboration

must reduce spread (need more statistics)

single-cell measurements (in nine-cell cavities)

ACFA Workshop - Barish

how costs scale with gradient
How Costs Scale with Gradient?

35MV/m is close to optimum

Japanese are still pushing for 40-45MV/m

30 MV/m would give safety margin

Relative Cost

Gradient MV/m

C. Adolphsen (SLAC)

ACFA Workshop - Barish

evolve the cavities minor enhancement
Evolve the CavitiesMinor 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

ACFA Workshop - Barish

new cavity design
New Cavity Design


28 cell Super-structure

More radical concepts potentially offer greater benefits.

But require time and major new infrastructure to develop.

single-cell achieved45.7 MV/m Q0 ~1010


ACFA Workshop - Barish

ilc siting and civil construction
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

ACFA Workshop - Barish

fermilab ilc civil program
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

ACFA Workshop - Barish

parameters of positron sources
Parameters of Positron Sources

ACFA Workshop - Barish




Conventional source

Undulator-based source

B=0.75 T

5 mm gap

ACFA Workshop - Barish

laser compton source
Laser Compton Source

ACFA Workshop - Barish

beam delivery systems challenges
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)

ACFA Workshop - Barish


ILC Strawman Layout


dump lines

20 mrad ILC FF9 (x 4)

Mark Woodley

ACFA Workshop - Barish

accelerator physics challenges
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.

ACFA Workshop - Barish

test facility at kek
Test Facility at KEK

ACFA Workshop - Barish


Test Facility at SLAC

ACFA Workshop - Barish


e- beam diagnostics

e- beam diagnostics

bunch compressor

laser driven electron gun


photon beam diagnostics


superconducting accelerator modules

TESLA Test Facility Linac - DESY

240 MeV

120 MeV

16 MeV

4 MeV

ACFA Workshop - Barish

fermilab ilc scrf program
Fermilab ILC SCRF Program

ACFA Workshop - Barish


ACFA Joint Linear Collider

Physics and Detector Working Group

  • “Our task is to continue studies on physics at the linear collider more precisely and more profoundly, taking into account progresses in our field, as well as on developments of detector technologies best suited for the linear collider experiment. As we know from past experiences, this will be enormously important to realize the linear collider.”
  • Akiya Miyamoto

ACFA Workshop - Barish

higgs coupling and extra dimensions
Higgs Coupling and Extra Dimensions
  • ILC precisely measures Higgs interaction strength with standard model particles.
  • Straight blue line gives the standard model predictions.
  • Range of predictions in models with extra dimensions -- yellow band, (at most 30% below the Standard Model
  • The models predict that the effect on each particle would be exactly the same size.
  • The red error bars indicate the level of precision attainable at the ILC for each particle
  • Sufficient to discover extra dimensional physics.

ACFA Workshop - Barish

beam detector interface
Beam Detector Interface



ACFA Workshop - Barish


The GDE Plan

  • 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 vs 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

ACFA Workshop - Barish