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

The Path Toward a Linear Collider

Barry BarishHEP 2005

Lisbon, Portugal 23-July-05

22-July-05 HEP 2005 - 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).


The Community then Self-Organized

Nov 13-15, 2004


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


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)



• 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)



• 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


Snowmass Workshop – Aug 2005


Snowmass – GDE Takes Over


Design Issues


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


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


Towards the ILC Baseline Design


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


rf bands:

L-band (TESLA) 1.3 GHz = 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

Specific Machine Realizations

Frequency dictates many of the design issues for LC


Cost Breakdown by Subsystem

cf31%

structures18%rf

12%

systems_eng8%

installation&test7%

magnets6%

vacuum4%

controls4%

cryo4%

operations4%

instrumentation2%

Civil

SCRF Linac


What Gradient to Choose?


TESLA Cavity

9-cell 1.3GHz Niobium Cavity

Reference design: has not been modified in 10 years

~1m


(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


Gradient

Results from KEK-DESY collaboration

must reduce spread (need more statistics)

single

-cell

measu

rem

ents

(in

nin

e-c

ell

cavit

ies)


How Costs Scale with Gradient?

Relative

Co

st

Gradient MV/m

2

0

$ lincryo

a Gb

G 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)


Gradient


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


New Cavity Design

More radical concepts potentially offer greater benefits.

But require time and major new infrastructure to develop.

28 cell Super-structure

Re-entrant

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

(Cornell)


Experimental Status

single cell


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


1 vs 2 Tunnels

• Tunnel must contain– Linac Cryomodule

– RF system

– Damping Ring Lines

• Save maybe $0.5M

• Issues– Maintenance

– Safety

– Duty Cycle


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


Parameters of Positron Sources

rep rate# of bunches per pulse

# of positrons per bunch

# of positrons per pulse

TESLA TDR 5 Hz 2820 2 · 1010 5.6 · 1013

NLC 120 Hz 192 0.75 · 1010 1.4 · 1012

SLC 120 Hz 1 5 · 1010 5 · 1010

DESY positron source

50 Hz 1 1.5 · 109 1.5 · 109


B=0.75 T5 mm gap

Conventional source

Undulator-based source

Positron source


Laser Compton Source





Fast Kicker Development


20 mrad ILC FF9 (x 4)

tuneupdump lines

ILC Strawman Layout

Mark Woodley


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)


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.


Test Facility at SLAC


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


Fermilab ILC SCRF Program


Test Facility at KEK


Beam Detector Interface

TauchiLCWS05


• 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


• 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


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

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

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