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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.

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

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  1. 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

  2. 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.

  3. 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 .

  4. 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.

  5. 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.

  6. 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).

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