ILC Project

Kaoru Yokoya

KEK

KEK Theory MeetingMarch 3, 2005

1

ICFA Decision

ICFA chose Superconducting Technology at ICHEP04 Beijingfollowing the recommendation of ITRP

ITRP Report lists advantages of SC

• Simpler operation

◦ Large cavity aperture ⇒ less sensitive to ground motion

◦ Large bunch distance ⇒ inter-bunch feedback

• Lower risk of main linac

• XFEL provides prototype

• Industrialization underway

• Less power consumption

2

The ITRP Report also states

• 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

What has to be done

• Form international collaboration structure

• Decide design choices and details

• Industrial design

• Cost reduction

3

Official Time Schedule

2004.8 Adopted ‘Cold’ at ICHEP, Beijing

2004.11 1st ILC Workshop at KEK

2005.2 Decide the director and location of Central GDI

2005. Establish Regional GDIs

2005.8 2nd ILC Workshop at Snowmass. Decide design outline

(acc.gradient, 1/2 tunnel, dogbone/small DR,

e+generation etc)

2005 end Complete CDR

2007 end Complete TDR, role of regions, start site selection

2008 Decide the site, budget approval

2009 Ground breaking

2014 Commissioning starts

4

Can TESLA be the baseline?

Yes, but still many alternatives remain after the SC/NC decision

• Accelerating gradient: 35MV/m or higher ?

• Tunnel: Single or double (or triple) ?

• Damping ring: dogbone or small ?

• Positron production: undulator or conventional ?

• Crossing angle: zero or small or large ?

5

Gradient

Result of questionnaire in WG5 in 1st ILC Workshop

25MV/m Technology in hand

35MV/m Needs essential work

45MV/m Future upgrade

6

7

Tentative 500 GeV Linac Parameters versus GradientTESLA USSC 30 MV/m 35 MV/m 40 MV/m

Ecms (GeV) 500 500 500 500 500N 1010 2.00 2.00 2.00 2.00 2.00Nb 2820 2820 2820 2820 2820Tsep (ns) 336.9 336.9 307.7 295.4 270.8Buckets 1.3GHz 438 438 400 384 352Iave (A) 0.0095 0.0095 0.0104 0.0108 0.0118Gradient MV/m 23.4 28.0 30.0 35.0 40.0Cavities/10MW klys 36 30 24 20 16Q0 1010 1.00 1.00 1.50 1.00 0.70Qext 106 2.50 2.99 2.93 3.28 3.44Tfill (us) 420.0 502.7 491.9 550.9 577.1Trf (ms) 1.37 1.45 1.36 1.38 1.34frep (Hz) 5 5 5 5 5Linac overhead 0 5% 5% 5% 5%Total no of cavities 20592 18096 16656 14240 12480Total no of klystrons 572 603 694 712 780Active 2 linac length (km) 21.6 18.7 17.3 14.8 12.9Total 2 linac length (km) 30.0 27.0 23.5 20.1 17.9Pb (MW) 11.3 11.3 11.3 11.3 11.3Pac (linacs) (MW) 94 105 104 121 142Luminosity 1034/cm2/s 3.0 2.6 2.0 2.0 2.0

8

Higher Gradient

• Must reach 1TeV

• Gradient gives an

impact on the site

length

• Presumably not an

issue for US and

Europe, but

• Is an issue for Japan.

• A few candidates>∼45km in Japan,

but prefer higher

gradient for flexibility

of site selectionSite length vs. Gradient for 1TeV

9

10

1/2 Tunnels?

• TESLA design adopts single

tunnel, accomodating

◦ Klystron

◦ Linac cryomodule

◦ 2 Damping Ring lines

• TESLA says

◦ Save cost ∼300MEuro

◦ Double tunnel has ground

motion problem

• But many problems of

operation

• Not a big impact on overall

design

11

Positron Production

-e

e+

AdiabaticMatchingDevice

IPto the

target

to

RingDamping

solenoids

Ti-alloy0.4 X0

250 GeV

undulator ~100 m

electronbeam

beamγ −

acceleratingstructure

Pros

• Polarized positron

• Single target

Cf: X-band e+ source requires 3

targets

• Better emittance of created

e+ beam

Cons

• Complex commiss./operation

(e+/e− operation coupled)

• Low energy operation

• IP energy spread of e− beam

0.05% ⇒ 0.15%

12

Conventional Positron Production

• Hit electrom beam on target rather than photon.

• Can decouple e+/e− beams

• Thick target (several rad length) ⇒ more energy deposit

• TESLA rejected the conventional method since the design start,

because of the large pulse charge (40 times X-band)

• But, later turned out 1ms pulse is long enough to prevent stress

accumulation.

• US estimation says comparable to X-band

• Target damage test being proposed at KEKB

◦ Ring total charge ∼ 10µC, close to TESLA pulse charge◦ Extraction in 10µs by existing abort system

(Extraction in 1ms requires advanced kickers)

• No polarized positron

13

Damping Ring

Problems of the Dogbone design

(a) Commissioning/operation

◦ DR commissioning only after linac completion◦ No DR tuning during linac repair

(b) Stray field from linac can disturb beam extraction from DR.

O(µTesla) matters.

(c) The long straight sections

◦ Space-charge force (Coulomb force within a bunch)◦ Long wiggler section needed ⇒beam stability range

(d) Fast kicker (<∼20ns) needed for injection/extraction

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• (a)+(b) (coming from sharing tunnel) can be partially solved by

in the 500GeV stage (But not in 1TeV stage)

• Space-charge problem is solved by ‘coupling bump’ in theoreti-

cal/computer level

• Kicker under development at DESY (data as of Apr.2004)

spec. measuredRise time (10%-90%) 8ns 4.9nsMicro pulse rep rate 3MHz 2MHzMacro pulse rep rate 5Hz 5HzAmplitude stability 0.05% 1.2% (0.2% with 30 kickers)

Residual kick 0.5% 2.75%

15

Alternative Design of DR Is a smaller ring possible?

• Compress more the bunch interval

• Main motivation is to avoid interference with linac

• but not the cost issue

Numerous ideas on injection/extraction

• Stripline kicker

New kicker to be tested at

ATF by summer 2005

• Fourier kicker

N−1∑

k=0

ei(ω0+k∆ω)t

16

Difficulties of Small DR

• Even more ambitious kickers required

• Collective instabilities harder (higher beam current)

Also, note:

• We are going to adopt 35MV/m as baseline

• TESLA 35MV/m (800GeV) requires 4886 bunches (11.5ns in

DR), not 2820 bunches (20ns)

• Even more bunches preferred at higher gradient

(in order not to loose power efficiency)

17

Crossing Angle

• Basically no big difference from warm design

• except for items related to the bunch distance

◦ No bunch-to-bunch interference

◦ IP fast feedback easier

• Three different designs

Original TESLA zero crossing angle

GLC small angle (7mrad)

→ bunch-bunch interference (warm collider)

NLC large angle (20mrad)

• 2nd IP: e+e− and γ-γ compatible?

• Linac orientation is another issue

18

Energy Upgrade Senario

Assume the gradient G is established by construction start

Senario 1500GeV

1TeV>=

G

G G'

• 1 stage cheaper

• possible gradient improve-

ment in 2nd stage

• Can accomodate dogbone DR

in the empty half in 1st stage

Senario 2500GeV

1TeV

G/2

G

• Do not need to close the pro-

duction line in industries for

2nd stage

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Parameter Subcommittee

• Formed under ILCSC in Apr.2003

• Members

S.Komamiya, D.Son (Asia)

R.Heuer (chair), F.Richard (Europe)

P.Grannis, M.Orglia (N.America)

• Report Sep.2003

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• Energy

◦ 500GeV (at any energy 200GeV ≤ ECM ≤ 500GeV)

◦ Upgradable to ∼1TeV

◦ Energy stability ≤ 0.1%

◦ Calibration run needed at 90GeV

(L can be lower, long shutdown acceptable)

• Luminosity

◦ ∫ Leqdt ≥ 500fb−1 in first four years of running (year zero for

commissioning not included)

(Leq: 500GeV-equivalent value using L ∝ ECM)

◦ Design luminosity by year 4

◦ After first 4 years,∫ Leqdt ≥ 1ab−1 in 2 years (option)

◦ For ECM upgrade,∫ Leqdt >∼ 1ab−1 in 3-4 years

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• P(e+)≥ 80%

• IPs

◦ 2IPs of similar energy reach and luminosity should be planned

◦ One IP must be compatible with γ-γ

◦ 2IP switch within a few % time loss

• Options

◦ e−e−

◦ P(e+)>∼50% for ECM ≥50GeV

◦ GigaZ: L >∼ several ×1033/cm2/s

◦ WW threshold: L >∼ several ×1033/cm2/s

Energy calibration <∼ a few 10−5

◦ γ-γ: L 30-50% of e+e−

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History of SLClate 1970’ proposal

Oct 1983 construction starts

mid-1987 construction ends

Apr.1989 first Z0 event

1992 SLD data taking start (pol beam av.22%)

1983 flat beam, strained lattice (pol ∼62%)

1994-5 damping ring chamber and FF optics improved

1995 thin strained lattice (pol ∼80%)

mid-1998 end of run

damping ring

damping ring

e-

e+

SLAC

arc

collision

point

e+target

23

Design and Final Parameters of SLC

Design Achieved Units

Beam charge 7.2×1010 4.2×1010 e±/bunch

Rep. rate 180 120 Hz

DR εx 3.0×10−5 3.0×10−5 m·radDR εy 3.0×10−5 0.3×10−5 m·radFF εx 4.2×10−5 5.5×10−5 m·radFF εy 4.2×10−5 1.0×10−5 m·radIP σx 1.65 1.4 µm

IP σy 1.65 0.7 µm

Pinch factor HD 2.2 2.2

Luminosity 6×1030 3×1030 /cm2/sec

EPAC2000, Vienna ’SLC- The End Game’, R.Assmann et.al.

24

History of SLC Luminosity

LINAC1998, Monterey, CA, ’SLC Final Performance and Lessons’, N.Phinney

25

Can ILC Do Better than SLC?

• Most problems in SLC were related to alignment/control/diagnosticsrather than acceleration issues

• Remarkable progress on these issues through SLC and after SLC

◦ Diagnostics devices, many of them non-destructivewire scanner, laser wire, bunchlength, cavity BPM

◦ Progress in computer simulation

◦ Feedback systempulse-to-pulse fdbk, collision fdbk, algorithm

◦ Progress in tuning algorithm

• Wakefield effects much weaker than in SLC (true even withwarm collider)

◦ Wakefield affects the accuracy of simulation

◦ When SLC was designed, the linac beam was known to beunstable under signle-bunch beam breakup.

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• There are still some beam dynamics problems pending. . .

◦ electron cloud and fast ion instabilities in DR

(Note: electron cloud was known before KEKB construction)

◦ stray field effects on DR

◦ banana control

but these are less serious than the predicted beam breakup at

SLC

• We will have more experience if ATF2 is constructed

27

Asian Organization for ILC Research

Working groups (same structure as in the ILCWS)

WG1 Overall design K. Kubo

WG2 RF H. Hayano

WG3 Injectors M. Kuriki

WG4 Beam Delivery System T. Sanuki

WG5 Cavities K. Saito

? Facility A. Enomoto

? Site R. Sugahara

Japan LC Office

F. Takasaki (chair), K. Yokoya, H. Hayano, N. Toge, S. Yamashita

28

Research in Asia

• Active participation from China and Korea

• Existing facilities and technology base(workshops in the labs, SC technology for nuclear fusion, etc.)

• Working Groups formed

• Many from China/Korea are visiting/going to visit KEK

• Possible production of components

IHEP contact person PAL Task Force Team

(Head) Won NAMKUNG

WG1 GAO Jie Jin-hyuk CHOI, Moo-yun CHO

WG2 CHI Yun-long Jong-seok OH, Won-ha HWANG

WG3 PEI Guo-xi Sung-ju PARK, Eun-san KIM

WG4 Wang Jiu-qing Jung-yun HUANG, Hee-seock LEE

WG5 ZHAO Sheng-chu Sang-ho KIM, Young-uk SOHN

29

Critical Reaserch Areas

• Establishment of the technology for acceleratinggradient 35MV/m

◦ Technologies for cost reduction

◦ Technologies for mass production

• Pursuit of possible higher accelerating gradient

◦ Larger operational margin of gradient

◦ Wider possibility of site selection

• Beam technology development using KEK-ATF

◦ Unique storage ring to reach ILC emittance

◦ Make full use of ATF capabilities

30

Remaining Problems on SC Technology (H. Hayano)

• Reliability of cavity gradient >35MV/m

• Complexity and cost of input coupler

• Rigidity of cavity-jacket relating to Lorentz detuning

• Reliability of tuner mechanism, Reliability of Piezo in cold

• Cavity alignment after cooling down

• Cost optimization of RF Waveguide System

• Cost optimization of cryomodule

31

Development of Higher Gradient

• Single-cell test soon

• 9-cell cavity design done. Fabrication started.

• Individual vertical test of four 9-cell cavities by Sep.2005

◦ Just in time for CDR completion

◦ In existing facilities (AR east)

◦ If expected performance not obtained,

⇒ change to slower plan for ILC 2nd stage

• Cryomodule test by end of 2006 ⇒ STF Phase 1

• Industrial design by TDR

32

STFSuperconducting RF Test Facility

• Linac R&D building for

JPARC

• Emptied by summer 2005

• 93m tunnel underground

• Reuse existing facilities

◦ Refregerator from AR east

◦ Power supply and

modulator

33

34

STF Phase 1 (2005-2006)

• Crymodule for 4 45MV/m cavities

• Crymodule for 4 35MV/m cavities

• RF source and cryogenic system (mostly recycled)

• Electron beam and its diagnostics system

• Synthetic test of 35MV/m & 45MV/m cryomodules with beam

and in parallel

• Construct cavity treatment facility in KEK

(can fabricate cavities also for overseas use and non-ILC use)

• Nb-Cu clad and seamless cavity fabrication for cost reduction

35

Targets of STF Phase 1

• Stable and reliable gradient 35MV/m with reasonable yield rate.

• Establish feasibility of 45MV/m

• KEK SC engineering experience

• First step to the industrialization

36

STF Phase 2 (2007-2009) still uncertain

• 3 Cryomodules each containing 12 cavities (35 or 45MV/m)

• Reinforcement of RF and cryogenic systems

• Synthetic test with a beam

Targets

• Industrial design

• Establish Asisn/Japanese technology for ILC component pro-

duction

37

Extension of ATF Extraction Line : ATF2• Stable collision of 5nm beams is essential in ILC

• SLAC-FFTB realized 60nm beam by ∼1997

• Extension of ATF extraction line can produce ∼35nm beam

This beam size itself is not a big progress but, with nanoBPM

technology being developed at ATF, a stabilization test down to

nanometer is possible

Time Scale

• Very useful for ILC design even after TDR

◦ Final Focus Design work will continue after ILC ground break-

ing (under constraints such as total length and crossing an-

gle)

• Can experience tuning work (Minimize ILC commissioning time)

38

39

Purposes of ATF2

(A) Small beam size

(A1) Obtain σy ∼35nm(Note: The principles of chromaticity correction are differentbetween FFTB and ILC)

(A2) Maintain for long time

(B) Stabilization of beam center

(B1) Down to <∼2nm by nanoBPM (cavity BPM)

(B2) Bunch-to-bunch feedback of ILC-type beam (∼300nm inter-val) when fast kicker extraction is ready

But technological ones are not all. . . ATF2 should be

• World center of beam-handling technology

• Recruit/education center for new comers

as the present ATF is.

40

International Collaboration on ATF2

• Design study going on by international collaboration

◦ Mini-workshops: Dec.11 at KEK, Jan.5 at SLAChttp://www-conf.slac.stanford.edu/mdi/ATF2.htm

◦ Submit proposal to PAC in May

◦ Complete the design by BDIR workshop in June

• Budget

◦ Total ≈ 3.0 Oku Yen (floor, beamline, diagnostics)

◦ Desirable to share the expense among Asia, North America,Europe

◦ Basic agreements with SLAC

• Present plan

◦ Floor construction in summer 2006

◦ Start operation in Jan.2007

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