ILC Conceptual Design

and R&D Status

Kaoru Yokoya, KEK

ICFA Seminar

Sep.29.2005, Daegu, Korea

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GDE (Global Design Effort)

Organization of GDE

• Director Barry Barish (Caltech)

• From each region (Asia, North Amer-

ica Europe)

◦ Regional Director

◦ Accelerator Design Leader

◦ Cost expert

◦ Civil engineering expert

◦ Communication

◦ 1 person from WWS

◦ Other accelerator physicists

• Present members 49 :

Europe 21,

North America 15,

Asia 12

2

Snowmass Workshop• 2nd WS following the 1st WS at KEK

• 2 week’s WS in parallel with Physics WS

• Participants over 600, Accelerator: ∼400

• Complete the BCD (Baseline

Configuration Document) by

end of 2005

• BCD describes the Design

Outline

• Snowmass is the 1st step to

BCD

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7 Subsystem Working Groups

WG1 Beam dynamicsWG2 Linac RFWG3a e+e− sourcesWG3b Damping RingWG4 Beam Delivery System (BDS)WG5 CavitiesWG6 Communications

6 Global Working Groups

GG1 ParametersGG2 InstrumentationGG3 Reliability/AvailabilityGG4 Civil engineeringGG5 Cost engineeringGG6 Options (γ-γ etc)

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Design Outline

• Accelerating gradient

• Positron generation scheme

• Shape & size of DR

• Number of bunch compressor stages

• Number of main tunnels

• Earth’s curvature

• Number of IPs and crossing angle

• Configuration layout of linac, DR,

etc. . . . . . . . . .

BCD will contain

• Description and reason of selection of BC (Baseline Configuration)

• together with description of AC (Alternative Configuration) which is

◦ still premature but may be completed in the near future◦ expected to give better performance and/or cost reduction

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Accelerating Gradient

• Energy reach = 1TeV

• Impact on the site length

• Conclusion at KEK WS

25MV/m in hand

35MV/m needs essential

work

45MV/m for ILC upgrade

• N. Walker’s summary in

LCWS2005(SLAC,

March)

30MV/m safe

35MV/m beaseline

40MV/m ambitius Site length vs. Gradient for 1TeV

Subject to many uncertainties

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Cavity Shape• Superconducting breakdown limit by magnetic field already reached

by recent technology

• Limit for TESLA-type cavity ∼41MV/m (operation grad. ∼35MV/m)

• Different shape required to exceed these values

Strong candidates : LL (Low Loss) type , Reentrant type

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Experimental Status(single cell)

JLab Single Crystal (2.2GHz)

∼44MV/m

Cornell Reentrant (1.3GHz)

47MV/m (pulsed) 1800 Oe

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Cornell-KEK Reentrant (1.3GHz)

Fabricated at Cornell Univ.

Surface-treated at KEK

51MV/m

10 8

10 9

10 10

10 11

0 10 20 30 40 50 60

Re-entrant single cell 10th

Qo(9th)Qo(10th)

Qo

Eacc[MV/m]

2005/09/06

Eacc=51.22MV/mQo=5.88e9

processing 36~38MV/m without X-r ayX-ray start from 40MV/mlimitation=runout liq. He(low-42% )

KEK LL 1.3GHz

46.5MV/m

2005.9.9

(These two results appeared after Snowmass)

⇒ Higher gradient established with single-cell cavities

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9-cell Cavity• Four 9-cell LL-type cavities (so-called ICHIRO) fabricated at

KEK, being tested

• No good results yet

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Snowmass Conclusion (not yet the final BCD)

500GeV stage 2nd stage (1TeV extension)

Baseline Alternative Baseline ultimate dream

Acc.Grad. 31.5(35) 36(40) 36(40)

Q0 (1010) 1.0(0.8) 1.0(0.8) 1.0(0.8)

Cavi.shape TESLA-typeLL/RE

super-structure

LL/RE

super-structure

single-crystal Nb

super-structure

‘31.5(35)’ means

• Adopt only the cavities over 35MV/m in vertical test（average over >∼37MV/m needed, taking into accountthe production yield)

• Prepare RF and cryo-system for 35MV/m

• but operate at 31.5MV/m

• Tunnel length to be computed using 31.5MV/m

• According to the baseline, the main linac length ∼41km for 1TeV

• Adding other components, the tunnel would be nearly 50km long

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Cavity Fabrication R&D for Cost Saving

Single Crystal (JLab)

• fabrication from large

grain/single crystal ingot

• May make electro-polishing

unnecessary

Nb-Cu Clad Cavity

(DESY,KEK)

• from a pipe of Nb-Cu clad• by hydro forming and

necking• save Nb and minimize

EBW (electron beam

welding) process

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Klystron• MBKs almost satisfy the specification : 10MW, 1.5ms, 65%

• Cost saving persued : sheet beam, inductive output tube, etc

Thales CPIToshiba

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Positron Production 3 shemes competingConventional sheme

Hit a few GeV electrons

on to target. Collect

positrons.

Undulator scheme

• Let >∼150GeV

electrons go thru

undulator to produce a

few 10’s GeV photons

• Bombard these

photons on a target.

Collect positrons.

-e

e+

AdiabaticMatchingDevice

IPto the

����

target

to

RingDamping

solenoids

Ti-alloy0.4 X0

250 GeV

undulator ~100 m

electronbeam

beamγ −

acceleratingstructure

E166 obtained polarized e+ from SLAC beam

Compton scheme

• Irradiate laser beam on a few GeV electrons in storage ring to

produce a few 10’s GeV photons

• Bombard these photons on a target. Collect positrons.

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15

Optical Cavity for Compton Scheme

• Store laser pulses in optical cavities (already in use for laser-wire)

• 30-cavity chain to reduce number of lasers

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Snowmass Conclusion on e+ Generation

• Baseline : undulator scheme

◦ Considered technically feasible

◦ Undulator location : end of linac (not seriously discussed)

◦ Advantage : polarized positron by using helical undulator

• Alternative : Compton scheme

• Backup for the baseline : conventional scheme

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Damping Ring

• Number of bunches 3000 (6000 desirable)

• 300ns interval in linac ⇒ total length ∼1ms → 300km

• Store compactly in DR

（circumference 20km → bunch interval ∼20ns, 6km → ∼6ns)

• Bunch by bunch extraction at 300ns interval (injection, too)

DR Linac

kicker field

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3 Candidates

6km

Dogbone• Dogbone (circumference 17km) share the tunnel with main linac

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Fast KickerDevelopment(KEK-ATF)

• Use commercial pulsar

• Test by kicking the ATF beam

• Excellent rerults :rise(fall) 3.6nsec,kick angle 80µrad、stability <0.75%

Measured Kick Angle

T.Naito

• Made 6km plan possible with

3000 bunches (still marginal

with 6000 bunches)

• Stability requirement may be

met by feed-forward 20

Snowmass Discussion on DR

• 6km plan seems to be preferred at present

◦ Extraction possible by KEK kicker

◦ No interference by main linac stray field

◦ Dynamic aperture larger than that of Dogbone

◦ Instabilities such as electron cloud / fast ion may be cured ?

� In case of severe instabilities or kicker limitation for 6000

bunches, 2 storied 6km rings may be constructed

• Final conclusion postponed to a mini-workshop (Nov.9-11 at

CERN)

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Bunch Compression

• DR bunch length a few 6mm

(present design 6mm)

• Shorter bunch (a few 100µm)

needed

• Combination of off-phase

linac and chicane (wiggler)

Snowmass Conclusionaccelerate

decelerate

delayadvance

z

E

off-phase linac chicane

• 6mm→300µm feasible with single stage

• 2-stage desirable for DR bunch 9mm and/or linac bunch 150µm

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• But 2-stage compressor is long and expensive（1.4km × 2）(1.4km includes acceleration of ∼7GeV). Net length ∼1.1km.

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Number of Main Linac Tunnels• Must accomodate

◦ RF system (klystron,

modulator?)

◦ Linac cryomodule

◦ 2 Damping Ring lines

(dogbone case）◦ Other beam transfer lines

� DR → Linac

� Positron → DR

(depending on layout &

e+ generation)

• 1 tunnel saves ∼300MEuro

(TESLA estimation)

• But subject to many

operation problems

• Snowmass Conclusion :

prefer 2 tunnelsTESLA Design

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Earth’s Curvature• Curved/kinked

◦ Shallow tunnel possible

(though a basin may make a shallow

and straight tunnel possible)

◦ Level survey easy

◦ Cryo-system easier

• Laser-straight

◦ Beam dynamics simpler

◦ Tunnel may be used for Multi-TeV

(but turned out no problem with

curved/kinked)

Snowmass → Conclusion postponed

curved

kinked

laser-straight

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Number of IPs and Crossing Angle

• Physicits obviously

prefer 2IP + 2detector

• counterargument :

cost only

Snowmass Conclusion

• Baseline: 2IP shifted

• Xing angle 2mrad &

20mrad

• Alternative:

◦ 2IP unshifted

◦ 1IP with push-pull

detectors

• No conclusion on 2

linacs angle (related to

multi-TeV)

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Energy Upgrade Senario

• No objection on 1st stage 500GeV, 2nd stage 1TeV

• Possible configuration at 1st stage

(A) Fill 1TeV tunnel and run at half gradient

(B) Linac at upstream in 1TeV tunnel

(C) Linac at downstream in 1TeV tunnel

(D) Only 500GeV tunnel constructed in phase 1

• (A) need not rebuild the production line but gradient upgradecannot be done

• (B) is preferred to (C) from beam dynamics

• (C) has an advantage of minimal 1st stage cost

Snowmass : Pending, but nobody prefered (A) and (C)

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The Most Preferred Plan as of Snowmass

PositronElectron

Main Linac

1st stage 2nd stage 2nd stage 1st stage

Main Linac

BC

BC

SR

SR

Undulator

DR DR

5GeV

Linac

5GeV

Linac

DR Damping ring

SR Spin rotator

BC Bunch compressor

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Schedule From Now

2005.Nov BCD Draft by GDE Executive Committee

2005.Dec Final BCD at GDE meeting at Frascati

2006.Jan Form CCB (Configuration Control Board) to controlpossible changes after BCD

2006.Mar GDE meeting at Bangalore (India) with physics WS

2006.Jun-Jul GDE meeting at Vancouber

2006.autumn GDE meeting in Asia

2006.年末 Complete RDR (Reference Design Report)(includes first cost estimation based on ‘sample sites’)

2007.Jan? 3rd ILC WS (in Europe)

2008-2009? Complete TDR (Technical Design Report)

? Site selection

Mid 2010’s Commissioning

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Test Facilities forSC Technology

• Test Facilities being build

◦ TTF (DESY)

◦ SMTF (FNAL)

◦ STF (KEK)

• Similar scale. Sum is ∼1% of

ILC 1 linac

• Aim at promoting technology

level of each region to par-

ticipate in the construction of

ILC main linacs.

• They are in collaboration

for cavity fabrication, surface

treatment, tests, cryomodule

design and fabrication, LLRF

development, etc.

TTF

SMTF

STF

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TTF2

• Built up to ACC5. BCP cavities only.

• VUV-FEL Spontaneous emission (30nm, Ee=450MeV) observed

(Dec.2004)

• Reached SASE saturation (Jan.2005)

• Next step

◦ Continue FEL studies in 2005

◦ Install ACC6(8 EP cavities, capable of 35MV/m) in spring?

2006, and reach 1GeV.

• Useful for ILC (30% time for ILC) though basically for FEL

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SMTF Superconducting Module & Test Facility

• FNAL Meson Experimental

Area

• Not an LC-dedicated facility

• ILC R&D

◦ cryomodule fabrication

◦ module test with upgraded

A0 injector

◦ establish 35MV/m

• Proton Driver and RIA (Rare

Isotope Accelerator) R&D

◦ v < c, 325MHz

• CW test area (for light

source)

◦ RF, cryogenics, controls

◦ 20MV/m CW

Collaboration of

• FNAL, ANL, BNL, JLab,

LBL, SNS, SLAC. . .

• DESY, INFN, KEK

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SMTF Schedule

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ATF2 at KEK• Extend ATF extraction line

to add Final Focus prototype

• Same optics scheme as ILC

Final Focus

• Squeeze down to ∼35nm

• Stabilize beam center to ∼2nm

• International collaboration from

beginning

IP

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Summary

• GDE actually started to design ILC

• Marvellous design progress in Snowmass Workshop

• Baseline Configuration Documents to be completed by 2005 end

• R&D on going in many respects.

Visit http://www.linearcollider.org/cms/

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