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Current Dependence of  y in ATF EXT (Summary of Study in 2000). S.Kuroda(KEK). Current dependence of  y was studied in 2000. Emittance is measured by 5 wire scanners(WS) in extraction(EXT) line of ATF. Before measurement, dispersion correction is done usually.

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current dependence of y in atf ext summary of study in 2000

Current Dependence of y in ATF EXT(Summary of Study in 2000)

S.Kuroda(KEK)

Current dependence of y was studied in 2000.

Emittance is measured by 5 wire scanners(WS)

in extraction(EXT) line of ATF.

Before measurement, dispersion correction is done usually.

Also coupling correction is done. But skew Q position is not ideal

( coupling correction skew Q is placed between WSs),

so the performance of the correction is ‘?’.

Nevertheless the measurement is done assuming x and y are

decoupled( 4D measurement is limited by the accuracy.

It sometimes give imaginary emittance.)

Mar.2000

Contents

1.Effect of Coupling Correction

2.Measurement in Coupling Resonance

3.Comparison with Damping Ring( DR ) Data

effect of coupling correction
Effect of Coupling Correction

Correction with

different Skew

setting

QK2X=0.8A

Emittance ratio is

current dependent.

QK2X=-0.2A

Emittance ratio seems

almost constant but

it’s due to large

Hhorizontal emittance

at high current.

effect of coupling correction 2
Effect of Coupling Correction(2)

Without

Coupling

Correction

Correction was

effective to some

extent.

Tilt Angle

In addition to x and y wire, each WS has u-wire

( tilted wire by 10 degree),which can be used to

measure tilt angle of the beam profile.

Finite amount of tilt angle was observed .

measurement in coupling resonance
Measurement in Coupling Resonance

On Coupling

EmitX is always

larger than emitY

somehow.

Off Coupling

Measurement error is so large to

say something definite from these

data.

comparison with dr data

EmitY

Comparison with DR Data

EmitX

Emittance in DR was measured by Laser Wire in 2004.

(PRL92(2004)054802, by courtesy of Y.Honda)

Clear difference between EXT and DR

( and also w and w/o correction) is clear in EmitY.

summary
Summary
  • We have observed current-dependent vertical emittance growth in EXT.
  • Coupling correction worked but still some amount of growth remained.( Skew Q position for the correction was not ideal. In ATF2, it will be improved.)
  • Comparing with the DR emittance, observed emittance growth cannot be explained by intra-beam scattering only.

We still observe y growth

in EXT(Mar.2007).