Special Lecture- ATF

The unique test facility for ILC with a low emittance beam.

Junji Urakawa, KEKILC School at KEK

2006.5.27

1. History and Machine introduction2. Machine performance3. R&D Programs and ATF24. Highlight Studies in Extraction Line

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ATF Collaboration History

• ATF Construction and R&D’s have been started with SLAC from 1993.

• From 1997 International collaboration was started for the R&D’s with Damping Ring. Many overseas institutes were involved.

• ATF MoU was established on 1st Aug. 2005. New organized ATF international collaboration has be

en started. (20 Institutes or more were signed.) 1st ICB meeting in Snowmass, 1st TB meeting at KEK on Dec..2nd TB meeting will be scheduled in May after ILC schoo

l.• From 2008, ATF2 : the final focus test beam line, will

be operated.

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1. Usually schedule of ATF machine operation is divided to two blocks of operating time per year with about four months summer long shutdown. One block is from mid. of Oct. to Dec., and the other is from mid. of Jan. to mid. of June. Since there are many collaborators, we proposed two meetings of TB per year in Dec. and May for review and recommendation of the research programs at ATF.

2. Requests to new proposal : Purpose, Research method, Period of the research, Manpower, Budget plan etc. should be reviewed for the approval. See Template for the new proposal (see http://atf.kek.jp/).

3. Member of ATF operation group : Shift leader is responsible for the safety and should be KEK staff. Since ATF operation group is responsible for beam tuning, making a good beam and required beam by R&D group, ATF operation group can involve many physicists and engineers from overseas countries and, young scientists and engineers can learn how to make the good beam.

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Assignment of the ATF Beam Time

TB:ApprovedStudies

~2/3

SP:ApprovedStudies

Beam Tuning

Maintenance

Typical ~22 weeks/yearAbout 20 % of total will be used for the maintenance and the beam tuning.It is estimated by current results.

Guideline for approved studied by SP.1. Short term study2. No conflict with approved studies by TB and ICB.3. Test study for new proposal4. SP can accept until two shifts/weekbut it depends on the situation of studies.

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Schedule of ATF operation, TB meeting and Long shutdown

Feb Apr Jun Aug Oct Dec Feb Apr Jun

JFY NEXT JFY

ATF Summer shutdown 22 beam weeks / 32 weeks Summer

Beam (KEK power contract) Shutdown

ScheduleUpgrade / MaintenanceInstallation

May Dec. MayTB meeting TB meeting TB meeting

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Mission of ATF

1. Establish the technologies associated with producing the electron beams of the quality required for ILC.

2. Provide such beams to ATF2 in a stable and reliable manner.

3. Serve the mission of providing the young scientists and engineers with training opportunities of participating in R&D programs for advanced accelerator technologies.

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Introduction ATFAccelerator Test Facility

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Machine performanceLook at experimental measurement results.

Multi-bunch electron beam generation

Gun cavity

High quality Multi-bunch beam is generated.1 ~ 20 bunches / pulse, 2.8ns spacing~ 2 x 1010 electrons / bunch

-0.5

0.0

0.5

1.0

1.5

-1 10-8 0 1 10-8 2 10-8 3 10-8 4 10-8 5 10-8 6 10-8 7 10-8

RF gun beam at 80MeV

Wal

l cu

rren

t m

on

ito

r at

80M

eV

Time [sec]

-0.5

0.0

0.5

1.0

1.5

-1 10-8 0 1 10-8 2 10-8 3 10-8 4 10-8 5 10-8 6 10-8 7 10-8

RF gun beam at 80MeV

Wal

l cu

rren

t m

on

ito

r at

80M

eV

Time [sec]

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Laser wire scanner in DR for X & Y scan, for single/multi-bunch

TEM00 wireTEM00 wire

TEM01 wireTEM01 wire

Two optical cavity chamberTwo optical cavity chamberFor X-wire and Y-wireFor X-wire and Y-wire

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Possibility of 1pm-rad y

Kubo's simulation:BPM offset error should be < 0.1

mm. (“BBA”)Then, εy ~ 2 pm will be achieved.

Magnet re-alignment, < 30 μm.Then, εy ~ 1 pm will be achieved.

Optics model should be good.Quad strength error should be < 0.5(?) %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

mit

tanc

e [1

0-1

2]

bunch intensity [electrons/bunch]

GLC Design

Measured in DR

Single bunch

Beam dynamics study

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High power pulsed laser-wire location

cw laser-wire and pulsed laser locationwith optical cavity

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Maximum energy 1.28 GeV (γ=2500)

Beam emittance

Vertical (1.5 ± 0.25) 10-11 m rad

Horizontal (1.4 ± 0.3) 10-9 m rad

Bunch Length ~9mm (30 ps)

Single bunch population 2.0 1010

Energy Spread 0.08%

Typical Beam Parameters in Damping Ring

Beam Scrubbing of DR, example

60~70mA (20bunch, 3train);1.3~1.5x10-6 pa --> 1.0~1.1x10-6 pa

- 210mA possible

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R&D Programs and ATF2• 1. kicker study for extraction of ILC-like bunch spacing.1. kicker study for extraction of ILC-like bunch spacing. Multi-pole component of kicker and septum is under study.• 2. Fast rise/fall strip-line kicker study for ILC Damping Ring.kicker study for ILC Damping Ring. <3ns rise/fall is under study.• 3. High resolution Ring-BPM for more small vertical emittance.3. High resolution Ring-BPM for more small vertical emittance. application of digital signal process is under study.• 4. Coherent Synchrotron Radiation(CSR) study. development of CSR detection is underway.• 5. Cavity BPMs.5. Cavity BPMs. nm resolution BPMs, PAL-BPM at ATF2, IP-BPM at ATF2.• 6. Laser Wire beam size monitor.6. Laser Wire beam size monitor. Fast sweep LW at EXT-line, Shintake-monitor at ATF2.• 7. Fast orbit feedback for ILC collision point.7. Fast orbit feedback for ILC collision point. digital feedback method is under development.• 8. Many other instrumentation(ODR, XSR, LW@DR) 8. Many other instrumentation(ODR, XSR, LW@DR) • 9. S-band RF-gun study for stable injection into ATF-DR.9. S-band RF-gun study for stable injection into ATF-DR.• 10. Pol. positron generation R&D based on Compton scattering.10. Pol. positron generation R&D based on Compton scattering.• 11. Fast Ion Instability Measurement

• 12. Multi-bunch Instability Study

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7 ‘y’ BPMs: 3 upgraded & 4 original

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

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32.7cm : correspondto rise/fall time of2.2nsecFast pulse PS :<1nses<3.2nsec

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Construction plan of ATF2

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Highlight Studies in Extraction Line • Stable beam extraction from DR

– Kick angle compensation for multi-bunch, Double kicker system

– Multi bunch extraction with ILC like beam spacing (2005~)

– 3 bunch extraction with 150ns spacing by 300ns flat-top double kicker.

• Instrumentation developments

– Beam size monitors

Optical Diffraction Monitor, Wire scanners (Tungsten, Carbon), Laser wire (UK, 2005~)

– Nano meter resolution Beam position monitors : Cavity BPM

• Intra-train beam feedback

– FONT (UK) / FEATHER (KEK)

– Feed-forward to Extraction line from DR (UK, 2006~)

• Other R&D

– Polarized positron generation

Compton scattering with electron beam and polarized laser

– Stabilization of components , Straightness monitor, StaFF (UK, 2006~)

• More new R&D in ATF will be proposed.

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Two sets of triplets (z ~ 6m):

SLAC/US/UK tripletKEK triplet

Plan to test each individually – then connect (2006)

Present results from both!

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Generic Cavity BPM Design: TM11-mode Selective Coupler

• Dipole frequency: 11.424 GHz• Dipole mode: TM11

• Coupling to waveguide: magnetic• Beam x-offset couple to y port

• Sensitivity: 1.6mV/nC/m (1.6109V/C/mm)

• Couple to dipole (TM11) only

• Does not couple to TM01

–Low Q with narrow cavity gap

–May need to damp TM01

–OR, use stainless steel to lower Q

signal

signal

Z. Li

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FFTB IP C-band cavity BPM triplet – this is the way to test BPM performance…

T. Shintake - 1998

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• Move one BPM at a time with movers• Extract BPM phase, scale, offset as well as beam motion by linear

regression of BPM reading against mover + all other BPM readings.

Calibration - SLAC

250 pulse sequence

+/-

20

um r

ange

of

mot

ion

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Move BPM in 1 um Steps

SLAC – upstream triplet – 17 nm resolution

resi

dua

l

Development of Cavity BPM - KEK• System

– Three Cavity BPMs developed in KEK

– Mover system with an active stabilization using an optical interferometer

– Analog down conversion and phase detection electronics

PerformanceResolution of the BPM: 17nmActive mover stabilizes the system better than the resolution

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ATF Laser-wire•Goal: •At ATF, we will aim to measure micron-scale electron spot-sizes with green (532 nm) light.

• Aim at intra-train (fast) scan for 150 ns bunch spacing.

• The final spot-size measurable at ILC will have implications for the length and layout of the BDS diagnostics section. • The ATF/ATF2 results will be crucial to determine the technical boundaries.

pulsed laser-wire location

BESSY, DESY, Oxford, Royal Holloway, UCL, CCLRC, KEK, Kyoto, SLAC

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ATF-LW Vacuum Chamber

Built atOxfordDO +Workshop

VacuumTestedAt DL

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ATF Laser-wire

Vacuum chamber built in Oxford and Installed in ATF extractionLine in December 2006.

Laser lighttransported toIP, but nocollisions yet seen; probablya detector issue.

New run plannedFor April 06.

Designingdiagnosticsinsertionat Oxford

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LW Practical Considerations

f1 geometry is challenging• Limitations from power• Limitations from angle• Surface optical quality• Alignment tolerance

f1 Lens design is challenging• Limitations from power• Limitations from ghost images• Alignment tolerance• Lens currently under construction

2nd LC Review, 7/28/2005 38

Feedback On Nanosecond Timescales (3)

Adjustable-gap kicker

BPM ML11X

Feedback

SuperfastBPM processor

Superfastamplifier

BPM ML12X

BPM ML13X

Aim:

TOTAL latency

< 20 ns

Oxford, DESY, CCLRC, KEK, Tokyo Metropolitan, SLAC

ATF extraction line beam direction

2nd LC Review, 7/28/2005 39

FONT3: Results (June 3 2005):Delay-loop feedback w. latency 23 ns

56ns bunchtrain

FB on

FB + delay loop on23ns

200um

2nd LC Review, 7/28/2005 40

FONT1,2,3: Summary67 ns

54 ns

23 nsEven fast enough for CLIC intra-train FB!May also be used at ILC

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FPGA

DAC

DAC

ADC

ADC

ADC

ADC

Differential To

singleAIN4

AIN3

AIN2

AIN1

AOUT1

AOUT2RAM

Clock circuit

JTAGcircuit

USBcircuit

UARTcircuit

IN Power Jack & switch

5v 2.5v ? v3.3v

JTAG connector

Serial connector

USBconnector

Flash/EEPROM

Clk IN

Differential To

single

Differential To

single

Differential To

single

FONT4: Digital FB Processor Module (Dabiri Khah)

Latency goal 100ns

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Q-BPM for ATF2 by PAL

Beam signal test : OKQBPM with Cu-beam chamberAre under fabrication by PAL.

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Design of ATF2 IP-BPM

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Prospect of ATF • ATF International R&D will generate

necessary results for ILC, especially how to control high quality beam, develop many kinds of advanced instrumentation, educate young accelerator physicists and engineers.

• ILC like beam which means 20 bunches with bunch spacing about 300nsec, in the future.

• Realization of about 35nm beam for long period.

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2005.3.9

From US, EU, Russia, China, Korea, India and Japanese Univ.,Many young physicists and engineers are learning and developing advanced accelerator technologies for ILC project.

ATF Control Room