1

Electron Accelerator System(ATF 2009)

K. Kubo (Most materials are from H. K. Kubo (Most materials are from H. HayanoHayano))

Multibunch photo-cathode RF-gunHigh gradient Linac

Damping RingExtraction Line

Final Focus Test LineInstrumentation

2

ATF Introduction

Final Focus lineIP; ~35 nm beam

ATF Linac

ATF Damping Ring

Extraction line

ATF IntroductionATF = Accelerator Test Facility,

Test Facility for Linear Colliders

• Test and demonstration of high quality (low emittance, stable) beam production

• Test and demonstration of the final focus scheme of Linear Colliders

• Development of various instrumentations

• etc.

ATF Linac• Beam Energy 1.3 GeV• Up to 4E10 e-/bunch (usually 1E10)• Up to 20 bunches/pulse• Rep. rate ~6.25 Hz (usually 3.125 or 1.5625 Hz)• Acceleration system

– RF frequency 2.856 MHz (S- band, same as SLAC)– 19 accelerating structures, 3 m long each

5

6

ATF Damping RingE=1.3GeVNe=1x1010 e-/bunch

1 ~ 20 bunchesγε x= 2.5E-6 ( at 0 intensity)

γεy < 2.5E-8 ( at 0 intensity)

Extraction line and Final Focus line (ATF2)

Final focal pointσy ~ 40 nm

FF lineEXT line

Test of final focus scheme of Linear Collider

Development of various instrumentationse.g. Beam position monitors, Beam size

monitors, Orbit feedback

8

Multibunch photo-cathode RF gun• For better MB injection into DR

generation of high quality multibunch

low emittance, low energy spread, high & flat intensity

• Cs2Te cathode• Laser system; 20 bunch, 2.8ns spacing, 266nm

Nd:YVO4 (1064nm) 357MHz mode-lock laser + amplifier

• Load-lock system for Cs2Te cathode block extra cathode blocks and evaporation chamber

• KEK built gun-cavityprecise machining and blazing by KEK machine center

9

RF-gun cavity & cathode block

Cathode block with CsTe coating

End plate with cathode blockCathode block

10

Multibunch photo-cathode RF-gun

11

Gun cavity, Loadlock & Laser system

Gun cavity

Seed Laser + Amplifier

Load-lock assembly

12

RF gun beam at 80MeV• Bunch Spacing

2.8 ns (8/2.856E6 s)• Beam Intensity

~1x1010/bunch• Normalized Emittance

εy= 4~7x10-6 rad.m• Bunch length

σz= 3 ~ 6 ps• Energy spread

dE/E = 2~3% full-width• Q.E. of CsTe cathode

16% initial, 2~3% with RF ON & constant over a week

Example of beam structure

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

-2 10-8 0 2 10-8 4 10-8 6 10-8 8 10-8

20 bunch beam from RFgun

Wal

l cur

rent

mon

itor

[V]

Time [sec]

~3x109

e-/bunch

13

ATF Linac regular unit1 Klystron + 1 SLED + 2 Acc. structures + wave guide, etc.

3 m Acc.

2-iris SLED

200

MW

200

MW

g)

TOSHIBA, E371280 MW4.5 sμ

3 m Acc.

14

Klystron power supply

Klystron

85MW klystron modulatorＰＦＮ

Trigger

THYRATRON

DE-QING TRIGGER

VDC POWER SUPPLY

15

RF pulse compression (SLED)

ATFで使用されているSLED空洞

SLED 空胴からの波を考えない入力波のSLED 結合部からの反射電圧

SLED 空胴から出てくる波 の電圧

SLED の合成電圧　

加速管中を通過する 電圧

ATF Linac: 4.5μs 1 μs

SLED = SLac Energy Doubler

16

Accelerator structure

S-band 2π/3 mode Disk Loaded Structure

D=35mm

t=~5mm

2a 2b

Time 0

Acc

. Fie

ld

350ps

17

regular unit rf waveform

3 m Acc.

2-iris SLED

200

MW

200

MW

Acc

eler

atin

g Fi

eld

(no

beam

load

ing)

34 MV/m

Energy gain with beam loading120 MeV 120 MeV

52 MV/m 52 MV/m34 MV/m

TOSHIBA, E3712

1st 2nd 3rd 4th

Klystron output rf power Reflection rf power from SLED+Acc.x2 Input rf power for left Acc. Input rf power for right Acc.

: : : :

80 MW4.5 sμ

3 m Acc.

Waveform of rf-power

18

Beam Loading

励起する電磁波の強さは

バンチの電荷量に比例する

ビームがつくった電磁波は空洞の共振モードで存在し続け、後方のバンチに減速力を与える。

Electric particles induce electro-magnetic fields in cavity.Accelerating resonance mode field survive long time and decelerate following particles.

Another point of view:Electric particles are accelerated, means they get energy from fields in the cavity.Field energy in cavity is reduced and following particles feel less acceleration.

Beam Loading

• Beam loading makes bunch by bunch energy difference in multibunch operation.

• The difference can exceed energy acceptance of following beam line (linac to ring transport line) and damping ring (about 1%)Beam loading compensation for mitigate

the effect.

20

ΔF Beam Loading compensation

後ろのバンチほど加速される

ビームローディングによって後ろのバンチほどエネルギーが下がる

Schematic explanation

regular RF

+-ΔF

Beam monitors in Licac

• Strip line BPM (beam position monitor)• Screen monitor (beam profile)• Beam current monitor• Streak camera (bunch length)

22

Linac stripline Beam Position Monitor

23

Screen monitor image

24

Beam current monitor

beam

beam

V

ビームダクト 絶縁ビームダクト 抵抗

Current trans Wall current monitor

25

Streak camera for bunch length measurement

掃引電極

slit MCP

掃引回路

掃引電極

光電面

レンズ

トリガー信号

加速電極スリット 蛍光面

蛍光面上のストリーク像

SpaceTime

MCPPhoto-cathode screen

Streak image

掃引波発生回路

OTR light

26

Damping Ring

Circumference 139 mE=1.3GeV

Old Extraction Line

27

B Combined function bending magnet

main Quad magnet

FOBO arc cell for low emittance

Defocus in horizontal plane: Reduce horizontal emittance and horizontal damping time

sextupole magnetssteering magnets

sub quad magnet

DR FOBO arc cell

photo

29

Injection/Extraction

QM

5R.1

(ZV

10R

)

QF5

2T

QM

10R

.1

QF5

3T

QD

52T

ZV51

T

QM

9R.1

QM

8R.1

QM

7R.1

QM

6R.1

ZH

50T

KIX

KII

BS

1X

BS

2X

BS

3X

BS

3T

BS

2T

BS

1T

Biμ

B0

Be

入射ビームリングのビーム

ヨーク

コイル(A ) コイル(B )

Septum magnet (DC)

L

C C

フェライト

電極

Kicker magnet (pulse)

extraction kickerinjection kicker

From Linac

EXT Line

Damped RF cavity

S. Sakanaka, et al., PAC1993, p1027

32

Low Emittance tuning• Optics modeling by beam based way

Q-magnet strength correction in model

• Beam based BPM offset measurementQ, SX trim excitation & bump orbit to orbit response

• COD correction• Dispersion correction• Coupling correction

horizontal kick to vertical response, then skew corrector

Alignment of magnets and Performance of BPM are essentially important.

33

Vertical Emittance history by 2004

Target Y emittance = 1.0 x 10-11 at 0 intensity(1% from X)

10-12

10-11

10-10

10-9

8/1/97 8/1/98 8/1/99 8/1/00 8/1/01 8/1/02 8/1/03 8/1/04

Single bunch emittance history

Y emittance (EXT wire, SR)Y emittance (LW)

Y e

mitt

ance

[rad

.m]

Date

RFg

un2µ

m B

PM

210m

A li

mit

DR

IonP

ump

20µm

BPME

XT

line

MB

ope

ratio

n

star

t MB

rad.

shie

ld

rad.

shie

ld

X e

mi c

onfir

med

GL

CT

A

rad.

shie

ld

refine beam tuning10-12

10-11

10-10

10-9

8/1/97 8/1/98 8/1/99 8/1/00 8/1/01 8/1/02 8/1/03 8/1/04

multibunch emittance history

Y emittance by Ext wire

Y emittance by LW

proj

ecte

d Y

em

ittan

ce [r

ad.m

]

Date

210m

A li

mit

2µm

BPM

RFg

un

DR

Ion

Pum

p

star

t MB

MB

ope

ratio

n

radi

atio

n sh

ield

radi

atio

n sh

ield

GL

CT

A

radi

atio

n sh

ield

Recent Vertical Emittance history

2008 - 2009

0

10

20

30

40

50

60

Nov/1/2007 Mar/1/2008 Jul/1/2008 Nov/1/2008 Mar/1/2009 Jul/1/2009

εy (pm) X-SR

SR-ILW

ε y (pm

)

Beam Monitors in Damping Ring

• Button BPM (96 BPMs in the ring)– One shot orbit– Averaged orbit (closed orbit). (Only 20 out of 96

BPMs now. To be improved.)– Turn-by-turn (Oscillation. Tunes.)

• SR (Synchrotron Radiation) monitors– Visible light

• profile (beam size)• interferometer (beam size)• streak camera (bunch length)

– X-ray profile (beam size)• Laser Wire monitor (beam size)

36

New clip-circuit modulefast base-line clip

~1GHz wide-band widthwith low noise

DR button BPM and New clip-circuit

37

Vertical dispersion Improvement

-15.0

-10.0

-5.0

0.0

5.0

10.0

15.0

0 20 40 60 80 100

Y dispersion before BPM improvement (26Nov2002)Y

dis

pers

ion

[mm

]

BPMnumber

-15.0

-10.0

-5.0

0.0

5.0

10.0

15.0

0 20 40 60 80 100

Y dispersion after BPM improvement (20May2003)

Y d

ispe

rsio

n [m

m]

BPMnumber

New Electronics

38

X to Y coupling Improvement

-200.0-150.0-100.0

-50.00.0

50.0100.0150.0200.0

0 20 40 60 80 100

dY by ZH2R 26Nov2002

dY[m

icro

n]

BPMnumber

-200.0-150.0-100.0

-50.00.0

50.0100.0150.0200.0

0 20 40 60 80 100

dY by ZH4R 26Nov2002

dY[m

icro

n]

BPMnumber

-200.0-150.0-100.0

-50.00.0

50.0100.0150.0200.0

0 20 40 60 80 100

dY by ZH2R 20May2003

dY[m

icro

n]

BPMnumber-200.0-150.0-100.0-50.0

0.050.0

100.0150.0200.0

0 20 40 60 80 100

dY by ZH4R 20May2003

dY[m

icro

n]

BPMnumber

New Electronics

39

Stored Beam – 10 minute time scale; ATF lifetime ~ few minutes

beam position read-out vs. beam intensity:

scattered plot : existing analog circuit.

line plot : digital read-out introduced for test.

aiming εy ~ 1 pm

Digital read-out

Analogue read-out

DR BPM resolution improvement by digital read-out system (SLAC, FNAL, KEK)

40

Beam oscillation measurement by TBT-BPM

Tune measurement with 4K memory

Slow oscillation meas.with 64k memory

41

42

Layout of the SR-interferometer

Synchrtron light Polarizer

Band pass filter

Double slit

f=600mmLens

Interferogram 7m

CCD

1.6.1997 T.Naito

a D

L L

1.3m

0

y

I = πaJ0{1+ exp[−(2πDaλL0

)2]• cos(2πDyλL )}

SR interference beam size monitor

Interference pattern

43

Beam image (x:39µm, y:7.3µm)X-ray SR beam size monitor(Tokyo Univ., KEK)

44

X-ray SR profiles

X profile Y profile

39.27 +/- 0.53 [μm] 7.30 +/- 0.12 [μm]

εxXSR = 1.8 x10-9 , εy

XSR = 1.1 x10-11

( ~ 3 x109 bunch intensity)

After subtracting dispersion effect

Laser wire beam size monitor in DR

Laser Wire

electron - photon collisions

electron beam

gamma-raysgamma-ray detector

Principle

46

Laser wire beam size monitor in DR

14.7µm laser wire for X scan5.7µm for Y scan(whole scan: 15min for X,6min for Y)

300mW 532nm Solid-state LaserFed into optical cavity

47

Laser wire block diagram

optical cavity resonance is kept by piezo actuator

48

Beam profile by Laser wire

σe2 = σmeas

2 - σlw2

εβ = σe2 – [η(Δp/p)]2 β:measured by Q-trim excitation

49

50

51

Single Bunch emittance

εx = 1.8x10-9 ( εxn = 4.5x10-6)

εy = 0.7x10-11(εyn = 1.7x10-8) at 9x109 intensity

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 2 109 4 109 6 109 8 109 1 1010

Horizontal Emittancex emittance (run B)x emittance (run D)simulation (0.4% coupling)

x e

mitt

ance

[10-9

]

bunch intensity [electrons/bunch]

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0 2 109 4 109 6 109 8 109 1 1010

Vertical Emittancey emittance (run B)y emittance (run D)simulation (0.4% coupling)

y e

mitt

ance

[10-1

2 ]

bunch intensity [electrons/bunch]

52

Bunch Length by SR monitor streak camera

15

20

25

30

35

40

0 2 109 4 109 6 109 8 109 1 1010 1.2 1010

bunch length(runD') [psec]bunch length(runE') [psec]bunch length(runF') [psec]simulation (0.4% coupling)simulation (6% coupling)simulation (3% coupling)

Bun

ch L

engt

h (r

ms)

[pse

c]

Bunch Intensity [electrons/bunch]

53

Energy Spreadby beam size monitor at EXT dispersive point

4.5 10-4

5.0 10-4

5.5 10-4

6.0 10-4

6.5 10-4

7.0 10-4

7.5 10-4

8.0 10-4

8.5 10-4

0 2 109 4 109 6 109 8 109 1 1010 1.2 1010

Energy Spread (runD)Energy Spread (run E)simulation (0.4% coupling)simulation (6% coupling)

Ene

rgy

Spre

ad

Bunch Intensity [electrons/bunch]

54

Multibunch Y Emittanceby Laser wire

Multibunch Projected Y emittance < 1% from X

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 2 109 4 109 6 109 8 109 1 1010

Vertical Emittance (Inc. Multibunch)

y emittance (single, runB)y emittance (single, runD)simulation (0.4% coupling)y emittance (20 bunch projected)

y e

mitt

ance

[10-1

2 ]

bunch intensity [electrons/bunch]

0.0 100

5.0 10-12

1.0 10-11

1.5 10-11

2.0 10-11

2.5 10-11

0 5 10 15 20

Multibunch Y emittance by LW (23April2004)

Y emittance (1.5E9 bunch intensity)Y emittance (4.6E9 bunch intensity)

Y e

mitt

ance

of e

ach

bunc

h [r

ad.m

]

bunch number

4.6x109 bunch intensity

1.5x109 bunch intensity

55

56

MB-BPM electronics

• Bunch by bunch, turn-by-turn acquisition8bit, 357MHz sampling, +/-250mV inputSum/diff circuit :

ATT for sum ch, ATT+19dB Amp. for diff. ch

three chassis : Fast S/H (RF) + S/H control (logic) + CAMAC interface

• Long memory128kB/ch --> 20bunch, 6.4k turnapplying FFT for each bunch,

then bunch oscillation and its phase can be observed

• Expected resolutioncentered beam : ~3µm at 1x1010 intensity (thermal noise resolution)1mm offset beam : ~16µm at 1x1010 intensity (bit resolution)

Fast kicker R&D (KEK,DESY,SLAC,LLNL)

Key technology for ILC damping ring

2005 - 2008Demonstration of very fast pulse kicker by using the electron beam in ATF damping ring.

R&D with several pulsers

2007〜Design of the beam extraction system by fast kicker

2009〜Trials of beam extraction

Rise time = 3.2ns(1%~100%)Fall time = 4.0ns(100%~1%)

ILC DR Injection/ extraction Kicker speed Limit of number of bunches

Bunch spacing in linac: ~300 nsCompressed in damping ring as short as possible

Circumference/bunch spacing = max. bunch number / pulse

Kicker field

Extract (inject) bunch by bunch using very fast kicker magnet.Kicker speed determine the bunch spacing

circumference/number of bunches

Bunch number may be limited by other effect: e.g. electron cloud instability in positron ring, fast ion instability in electron ring.

300 ns

extractionMain Linac

Damping Ring

Strip-line kicker

Auxiliary Septum Beam extraction trial

2008 DecemberInstalled in DR

2009 JanuaryFirst trial (2 weeks)

Postponed in June.Pulsers were broken when we fired for the beam extraction.System was removed from DR.

Fast Kicker hardware and Plan

Multi-bunch beam in ATF2

Multi-bunch in ATF2 by fast kicker30 bunches with 308 ns spacing60 bunches with 154 ns spacing

• Demonstrate the beam extraction• Check the reliability-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

-600 -400 -200 0 200 400 600 800

(Single bunch) x 3 Train Extraction

BP

M S

igna

l

Time (nsec)

154ns spacing

1↓1↓

2 >2 >

1) Ch1: 10 mV 50 ns 2) Ch1: 100 mV 50 ns Thy. Current 1 Amplitude Droop at 300ns

3 bunches, 154ns spacing

308ns pulse width

Present ATF kicker(Pulse magnet kicker system)

Bunch structure at ATF2 by Fast kicker

Cavity Compton ( R&D for Cavity Compton ( R&D for pol.epol.e++ ))All equipments are installed into the DR on 12th Sep. 2007.The first signal was detected on 30th Jan. 2008.All equipments are installed into the DR on 12th Sep. 2007.The first signal was detected on 30th Jan. 2008.

Cavity-Compton Setup (IP)

γ-ray detector (shared with LW)

62

EXT and FF Line beam diagnostics

Stripline BPMCavity BPMScreen monitorOTR monitorWire scannerLaser Interferometer

63

Tungsten (carbon) wire scanner

64

multibunch wire scannergamma detection system

65

66

OTR Monitor (SLAC)

( 76.6 µm , 9.5 µm )

beamtarget

microscope

67

ODR Monitor

ODR Target chamber

ODR Target Holder

Observation of visible light ODR

68

69

70

Cavity BPM

beam

cavitywave guide

Dipole mode RF field is induced by beam with offset.Field strength ~ proportional to offset.RF is extracted through slit and wave guide and detected.

TM 110 mode

Beam position monitors for ATF2, made by PAL (Korea)

photo by Toge

IP BPM test model

IP-BPM (KNU, KEK)R&D will be continued at ATF2. It should be re-installed.

Low Q IP-BPMKEK IP-BPM

Position sensitivity test performed, consistent with expectationBunch separation achieved in 154 ns interval

Beam test at ATF extraction line@0.7x10^10 e/bunch, dynamic range: 5 um

Achieved resolution8.72 +-0.28(stat) +-0.35(sys) nm

to 2nm Stabilization of Temperature, Stabilization of extracted beam

IP Beam Size Monitor (Tokyo, KEK)• Commissioning was started by Laser wire mode (horizontal scan).

• Searching the collision of laser and beam next slide

• Setup for Interference mode (vertical scan)• 2 and 8-degrees crossing will be done in this spring.• 30 and 174-degrees crossing will be done until next fall.

Scan range:

Crossing:

Beam size monitor for ATF2-IP(Tokyo Univ., KEK)

FFTB result

Result in FFTB at SLAC

Installation at ATF2-IP (2008/5)

by Terunuma

Experimental data of IP BSM

Not yet. . . . . . . . .

Post-IP Wire Scanner (SLAC)• FFTB carbon wire scanner was installed at post IP.

• Witting for a beam commissioning (next week)

• 10 micron Tungsten Wires (H, V and 45° scanning)• better signal for large initial beam sizes

• 5 micron Carbon Wires (V and +-1.3° scanning)

Oxford, Daresbury, QMUL, SLAC, KEK, DESY, CERN

Kicker BPM 1

Feedback

BPM processor

Driveamplifier

BPM 2

BPM 3

e-

History of latencyFONT1 (NLCTA) : 67nsFONT2 (NLCTA) : 54nsFONT3 (ATF) : 23ns

FONT : Fast feedback R&D

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

-600 -400 -200 0 200 400 600 800

(Single bunch) x 3 Train Extraction

BP

M S

igna

l

Time (nsec)

154ns spacing

3 bunches, 154ns spacing

FONT4, Digital feedback (ATF)

FONT (Re-installation) at ATF2Dedicated location at ATF2. • New beamline layout with three pickup BPMs (KEK) and

two Kickers (SLAC) are installed.• Commissioning will start in next week.

Pulsed Laser Wire R&D(RHUL, Oxford, KEK)

ILC design requirement:< 1 um laser wire scanner

2007/Jan

σ~8um2008/May

σ~3.8umRealize the 1 um beam size scanning in FY2008, by implementing improvements in the electron beam optics and improved laser diagnostics.

Pulsed Laser Wire at ATF2(Re-installation)

Dedicated location at ATF2.• Laser system is under moving to new hut.• Collision system in the beamline will be re-installed until

fall.

New location forLaser wire

Laser hut

ATF2 - LC Final Focus test

Goals of ATF2 project• Demonstration of the focusing method of ILC

– ~40 nm RMS vertical beam size– Will be confirmed using Shintake-monitor

• Demonstration of beam stabilization– ~2 nm vertical jitter– Feedback using nano-BPM (beam position monitor

with nano-meter resolution)

T.Tauchi, EPAC08

Hardware system at ATF2

86

ATF2 Construction Schedule

ATF2 Beam

Floor Refurbishment2007/8/20 2007/9/4

ATF2 construction

2007/9

2007/10

2007/12

ATF2 construction

2008/2 2008/9: new EXT

2008/5

International Contribution (1)ATF2 Q-magnet Setup

Concrete Base Stand (KEK)

FFTB mover (SLAC)

QBPM(Cavity BPM)(KEK,PAL)

Q magnet (KEK,SLAC,IHEP)

QBPM electronics(SLAC)

(2008/6)

International contribution (2)

High Availability PS (SLAC)

FF dipoles, quadrupoles (IHEP)Sextupoles (SLAC)

Infrastructures, Cables (KEK)

Magnet mover system andQBPM readout (SLAC)

International contribution (3)

Final Doublet systemMagnets and Movers(SLAC)Supports and Table (LAPP)

S-band BPM (KNU)

IP-BSM (Tokyo Univ.)

ATF2 beam line