the path to an international linear collider barry barish triumpf seminar 15-april-05

The Path to an International Linear Collider

Barry BarishTRIUMPF Seminar

15-April-05

15-April-05 TRIUMPF 2

Features of e+e- Collisions

• elementary particles

• well-defined

– energy,

– angular momentum

• uses full COM energy

• produces particles democratically

• can mostly fully reconstruct events


A Rich History as a Powerful Probe


The Energy Frontier


2001: The Snowmass Workshop participants produced the statement recommending construction of a Linear Collider to overlap LHC running.

2001: HEPAP, ECFA, ACFA all issued reports endorsing the LC as the next major world project, to be international from the start

2002: The Consultative Group on High-Energy Physics of the OECD Global Science Forum executive summary stated as the first of its Principal Conclusions:

“The Consultative Group concurs with the world-wide consensus of the scientific community that a high-energy electron-positron collider is the next facility on the Road Map.

“There should be a significant period of concurrent running of the LHC and the LC, requiring the LC to start operating before 2015. Given the long lead times for decision-making and for construction, consultations among interested countries should begin at a suitably-chosen time in the near future.”

The Linear Collider


Understanding Matter, Energy, Space and Time:The Case for the Linear Collider

A summary of the scientific case for the e+ e- Linear Collider, representing a broad consensus of the particle

physics community.

April 2003: signed now by ~2700 physicists worldwide.:

“Consensus Document”

http://sbhepnt.physics.sunysb.edu/~grannis/ilcsc/lc_consensus.pdf )(To join this list, go to http://blueox.uoregon.edu/~lc/wwstudy/ )


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 ~0.5-1.0 TeV LC and the LHC science.


Electroweak Precision Measurements

LEP results strongly point to a low mass Higgs and an energy scale for new physics < 1TeV

0

2

4

6

10020 400

mH GeV

Excluded Preliminary

had =(5)

0.027610.00036

0.027470.00012

Without NuTeV

theory uncertainty

Winter 2003


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 ~0.5-1.0 TeV LC and the LHC science.


The 500 GeV Linear Collider Spin Measurement

LHC should discover the Higgs

The linear collider will measure the spin of any Higgs it can produce.

The process e+e– HZ can be used to measure the spin of a 120 GeV Higgs particle. The error bars are based on 20 fb–1 of luminosity at each point.

LHC/ILC Complementarity

The Higgs must have spin zero


Extra Dimensions

New space-time dimensions can be mapped by studying the emission of gravitons into the extra dimensions, together with a photon or jets emitted into the normal dimensions.

Linear collider

LHC/ILC Complementarity


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


main linacbunchcompressor

dampingring

source

pre-accelerator

collimation

final focus

IP

extraction& dump

KeV

few GeV

few GeVfew GeV

250-500 GeV

Linear Collider Concept


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


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 requires uniting behind one technology, and then make a unified global design based on the recommended technology.


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.


TESLA Cavity

• RF accelerator structures consist of close to 21,000 9-cell niobium cavities operating at gradients of 23.8 MV/m (unloaded as well as beam loaded) for 500 GeV c.m. operation.

• The rf pulse length is 1370 µs and the repetition rate is 5 Hz. At a later stage, the machine energy may be upgraded to 800 GeV c.m. by raising the gradient to 35 MV/m.


TESLA Single Tunnel Layout

• The TESLA cavities are supplied with rf power in groups of 36 by 572 10 MW klystrons and modulators.


• The JLC-X and NLC are essentially a unified single design with common parameters

• The main linacs are based on 11.4 GHz, room temperature copper technology.

GLCGLC/NLC Concept


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 4064 75 MW Periodic Permanent Magnet (PPM) klystrons arranged in groups of 8, followed by 2032 SLED-II rf pulse compression systems


GLC / NLC Concept

NLC

• Two parallel tunnels for each linac.

• For 500 GeV c.m. energy, rf systems only installed in the first 7 km of each linac.

• Upgrade to 1 TeV by filling the rest of each linac, for a total two-linac length of 28 km.


The Report Validates the Readiness of L-band and X-

band Concepts

ICFA/ILCSC Evaluation of the Technologies


TRC R1 Issues

L-Band: Feasibility for 500 GeV operation had been demonstrated, but 800 GeV with gradient of 35 MV/m requires a full cryomodule (9 or 12 cavities) and shown to have acceptable quench and breakdown rates with acceptable dark currents.

X-band: Demonstrate low group velocity accelerating structures with acceptable gradient, breakdown and trip rates, tuning manifolds and input couplers. Demonstrate the modulator, klystron, SLED-II pulse compressors at the full power required.

R1 issues pretty much satisfied by mid-2004


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


International Technology Review Panel


ITRP Schedule of Events • Six Meetings

– RAL (Jan 27,28 2004)

– DESY (April 5,6 2004)

– SLAC (April 26,27 2004)

– KEK (May 25,26 2004)

– Caltech (June 28,29,30 2004)

– Korea (August 11,12,13)

– ILCSC / ICFA (Aug 19)– ILCSC (Sept 20)

Tutorial & Planning

Site Visits

Deliberations

Exec. Summary Final Report

Recommendation


Evaluating the Criteria Matrix

• We 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

• We evaluated each of these categories with the help of answers to our “questions to the proponents,” internal assignments and reviews, plus our own discussions


Our Process• We studied and evaluated a large amount of

available materials

• We made site visits to DESY, KEK and SLAC to listen to presentations on the competing technologies and to see the test facilities first-hand.

• We have also heard presentations on both C-band and CLIC technologies

• We interacted with the community at LC workshops, individually and through various communications we received

• We developed a set of evaluation criteria (a matrix) and had each proponent answer a related set of questions to facilitate our evaluations.

• We assigned lots of internal homework to help guide our discussions and evaluations


What that Entailed

– We each traveled at least 75,000 miles

– We read approximately 3000 pages

– We had constant interactions with the community and with each other

– We gave up a good part of our “normal day jobs” for six months

– We had almost 100% attendance by all members at all meetings

– We worked incredibly hard to “turn over every rock” we could find.

from Norbert Holtkamp


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.


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.


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


What’s Next

• Organize the ILC effort globally

– Coordinate worldwide R & D efforts, in order to demonstrate and improve the performance, reduce the costs, attain the required reliability, etc.

– Undertake making a “global design” over the next few years for a machine that can be jointly implemented internationally.

– These goals are within reach and we fully expect to have an optimized design within a few years, so that we can undertake building the next great particle accelerator.


Fall 2002: ICFA created the International Linear Collider Steering Committee (ILCSC) to guide the process for building a Linear Collider. Asia, Europe and North America each formed their own regional Steering Groups (Jonathan Dorfan chairs the North America steering group).

Physics and Detectors Subcommittee (AKA WWS) Jim Brau, David Miller, Hitoshi Yamamoto, co-chairs (est. 1998 by ICFA as free standing group)

International Linear Collider Steering CommitteeMaury Tigner, chair

ParametersSubcommitteeRolf Heuer, chair

(finished)

Accelerator SubcommitteeGreg Loew, chair

Comunicationsand OutreachNeil Calder et al

Technology Recommendation Panel

Barry Barish, chair (finished)

Global Design Initiative

organization Satoshi Ozaki, chair (finished)

GDI central team site

evaluation Ralph Eichler,

chair

GDI central team director

search committee Paul Grannis,

chair


Starting Points for the ILC Design

33km47 km

TESLA TDR500 GeV (800 GeV)

US Options Study500 GeV (1 TeV)


Experimental Test Facility - KEK

• Prototype Damping Ring for X-band Linear Collider

• Development of Beam Instrumentation and Control


Evaluation: Technical Issues


TESLA Test Facility Linac

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


Attendees: Son (Korea); Yamauchi (Japan); Koepke (Germany); Aymar (CERN); Iarocci (CERN Council); Ogawa (Japan); Kim (Korea); Turner (NSF - US); Trischuk (Canada); Halliday (PPARC); Staffin (DoE – US); Gurtu (India)

Guests: Barish (ITRP); Witherell (Fermilab Director,)

“The Funding Agencies praise the clear choice by ICFA. This recommendation will lead to focusing of the global R&D effort for the linear collider and the Funding Agencies look forward to assisting in this process.

The Funding Agencies see this recommendation to use superconducting rf technology as a critical step in moving forward to the design of a linear collider.”

FALC is setting up a working group to keep a close liaison with the Global Design Initiative with regard to funding resources.

The cooperative engagement of the Funding Agencies on organization, technology choice, timetable is a very strong signal and encouragement.

Statement of Funding Agency (FALC) 17-Sept-04 @ CERN

The Birth of the

Global Design Effort

Linear Collider Workshop

Stanford, CAMarch-05


ILC Design Issues

First Consideration : Physics Reach

ILC Parameters

Energy Reach

2cm fill linac RFE b L G

Luminosity RF AC BS

cm y

PL

E


Parameter Space

nom low N lrg Y low P

N 1010 2 1 2 2

nb2820 5640 2820 1330

ex,ymm, nm 9.6, 40 10,30 12,80 10,35

bx,ycm, mm 2, 0.4 1.2, 0.2 1, 0.4 1, 0.2

sx,ynm 543, 5.7 495, 3.5 495, 8 452, 3.8

Dy18.5 10 28.6 27

dBS% 2.2 1.8 2.4 5.7

szmm 300 150 500 200

PbeamMW 11 11 11 5.3

L 1034 2 2 2 2

Range of parametersdesign to achieve 21034


Achieving Maximum Luminosity

nom low N lrg Y low P High L

N 1010 2 1 2 2 2

nb 2820 5640 2820 1330 2820

x,y m, nm 9.6, 40 10,30 12,80 10,35 10,30

x,y cm, mm 2, 0.4 1.2, 0.2 1, 0.4 1, 0.2 1, 0.2

x,y nm 543, 5.7 495, 3.5 495, 8 452, 3.8 452, 3.5

Dy 18.5 10 28.6 27 22

BS % 2.2 1.8 2.4 5.7 7

z m 300 150 500 200 150

Pbeam MW 11 11 11 5.3 11

L 1034 2 2 2 2 4.9!


Towards the ILC Baseline Design


e- Beam Transport XFEL

e- Damping Ring

HEP & XFEL Experiments

e- Main LINAC e+ Beam delivery e+ Main LINAC

e+ Damping Ringe- Sources e+ Beam Transport

e- Beam delivery

e+ Source

e- Switchyard XFEL

PreLinac

PreLinac

Beam DumpsDESY site Westerhorn

TESLA machine schematic view

Power Water & Cryogenic Plants

Machine cost distribution

Main LINAC Modules

Main LINAC RF System

Civil Engineering

MachineInfrastructure

X FELIncrementals

Damping Rings

HEP Beam Delivery

AuxiliarySystems

Injection System

1131

~ 33 km

587 546

336241 215

124 101 97

Million Euro

TESLA Cost Estimate3,136 M€ (no contingency, year 2000) + ~7000 person years


Gradient


(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)


New Cavity Shape for Higher Gradient?

TESLA Cavity

• A new cavity shape with a small Hp/Eacc ratio around35Oe/(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


Gradient vs Length

• Higher gradient gives shorter linac – cheaper tunnel / civil engineering– less cavities – (but still need same # klystrons)

• Higher gradient needs more refrigeration– ‘cryo-power’ per unit length scales as G2/Q0

– cost of cryoplants goes up!


Klystron Development

THALUS

CPITOSHIBA

10MW 1.4ms Multibeam Klystrons~650 for 500 GeV+650 for 1 TeV upgrade


Towards the ILC Baseline Design

Not cost drivers

But can be L performancebottlenecks

Many challenges!


Damping Rings

bunch train compression300km 20km

smaller circumference(faster kicker)

higher Iav


Beam Delivery System


Strawman Final Focus


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


Positron Source

• Large amount of charge to produce

• Three concepts:– undulator-based (TESLA TDR baseline)

– ‘conventional’ – laser Compton based


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

the path to an international linear collider barry barish triumpf seminar 15-april-05

Documents

lhc science

tev scale e e accelerator

process e e hz

tev lc

low mass higgs

higgsthe linear collider

energy scale

linear collidertriumpfapril