1

Low Emittance Beam Generation in ATF

H. Hayano for the ATF collaborationH. Hayano for the ATF collaboration

BPM electronics improvement

emittance tuning

Laser wire beam size monitor

emittance measurement results

APAC2004 3/25/2004

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E=1.28GeVNe=1x1010 e-/bunch 1 ~ 20 bunchesRep=1.5HzX emit=2.5E-6( at 0 intensity) (1nm)

Y emit=2.5E-8( at 0 intensity) (10pm)

Accelerator Test Facility for e- source development of LC

Damping ring

Linac

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Low Emittance tuning

• Optics modeling by beam based way Q-magnet strength correction in model

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

• COD correction• Dispersion correction• Coupling correction horizontal kick to vertical response, then skew correct

or

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ATF Damping Ring BPMreference

plane

referenceplane

EBW

referenceplane

19.5 mm

ceramics

button (SUS304)

flange (A3003)HIP transitiontop block (Ti)

SMA connector

pin (Kovar)brazing (Ag-Cu)

brazing (Al)

Button BPM for Damping Ring

ø24mm

70mm

Button electrode assemblycross section of BPM camber

Electronics: single pass detection for 96 BPMs DC-50MHz BW, base line clip & charge ADC, min. resolution ~20µm

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Spectrum of DR BPM

Signal peak at ~ 1GHz

40

45

50

55

60

65

107 108 109 1010

[ ]Freqency Hz

DR button BPM beam signal spectrum 40 223/ out from m RG u cable

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BPM electronics improvement

Electronics: 40MHz - 1GHz BW, base line clip & low noise LF amp min. resolution ~2µm

ch 1

ch 2

ch 3

ch 4

calibration pulse

HPF 50MHz LPF1000MHzATT

LPF135MHz

Gain change

RF amp 40 ~ 1000MHzGain 28.5dB25dBm output

LF amp DC~ 155MHzGain 15dB19dBm output

Microwave diode detector 600 ~ 1000MHz

RF combiner

4-way splitter

-20dB

Improved BPM Circuit ( simplified diagram )

single bunch

multibunch

ch 2

ch 3

ch 4

SMA

SMA

SMA

SMA

SMA

QLA

QLA

QLA

QLA

gain change control flat

ch 1

ch 2

ch 3

ch 4

signal from BPM signal to charge ADC

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1

10

100

108 109 1010 1011

[ / ]Bunch Intensity electrons bunch

Existing circuit( )estimated by beam

Improved circuit( )estimated by calibration pulser

Resolution Improvement

Min. resolution ~ 2µm

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Vertical orbit Improvement

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

0 20 40 60 80 100

Y orbit before BPM improvement (26Nov2002)

BPM number

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

0 20 40 60 80 100

Y orbit after BPM improvement (20May2003)

BPMnumber

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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)

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)

BPMnumber

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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

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

BPMnumber

-200.0-150.0-100.0-50.0

0.050.0

100.0150.0200.0

0 20 40 60 80 100

dY by ZH2R 20May2003

BPMnumber

-200.0-150.0-100.0

-50.00.0

50.0100.0150.0200.0

0 20 40 60 80 100

dY by ZH4R 20May2003

BPMnumber

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Laser wire beam size monitor in DR

14.7µm laser wire for X scan 5.7µm for Y scan(whole scan: 15min for X,6min for Y)

300mW 532nm Solid-state LaserFed into optical cavity

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Laser wire block diagram

optical cavity resonance is kept by piezo actuator

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Beam profile by Laser wire

e2 = meas

2 - lw2

= e2 – [(p/p)]2 measured by Q-trim excitation

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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)

Bunch Intensity [electrons/bunch]

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Energy Spread by 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)

Bunch Intensity [electrons/bunch]

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Transverse Emittance by Laser wire

< 0.4% y/x emittance ratio

Y emittance =4pm at small 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 Emittance

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

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 Emittance

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

bunch intensity [electrons/bunch]

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Conclusion• BPM resolution improvement by new electronics by extending band width

minimum resolution is 2µm.

• Fine beam tuning using improved BPM Optics model and BPM offset were refined.

Beam parameters were improved.

• Laser wire beam size monitor development Precise beam size measurement in DR with non-destructive way.

• Low vertical emittance beam was generated and confirmed.

yn = 1.0x10-8 (4pm at 1.28GeV) vertical emittance at small intensity