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Optics for Skew Correction and Emittance Measurement

Optics for Skew Correction and Emittance Measurement. Leo Jenner This talk is going to look familiar if you were at the recent LC-ABD meeting in Manchester…. <x 2 > <xx’> <xy> <xy’> <xx’> <x ’2 > <x’y> <x’y’> <xy> <x’y> <y 2 > <yy’> <xy’> <x’y’> <yy’> <y ’2 >. = s.

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Optics for Skew Correction and Emittance Measurement

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  1. Optics for Skew Correction and Emittance Measurement Leo Jenner This talk is going to look familiar if you were at the recent LC-ABD meeting in Manchester…

  2. <x2> <xx’> <xy> <xy’> <xx’> <x’2> <x’y> <x’y’> <xy> <x’y> <y2> <yy’> <xy’> <x’y’> <yy’> <y’2> = s 4D symmetric beam matrix To minimise the vertical emittance, especially for a flat beam, it is desirable to remove any cross-plane (x-y) correlations/couplings Coupling terms

  3. Sources of Skew Linac is main source of skew in ILC Skew correction section comes immediately afterwards and is the first sub-system of BDS

  4. Ideal Skew Correction + Emittance Measurement Layout 4 orthogonal skew quadrupoles correct xy, x’y’, x’y, xy’ 4 wire scanners / laser wires for emittance measurement

  5. 4D measurement simulation – 6 wire scanners required Measured Emittance Input Emittance Perturbed Projected Emittance Unperturbed Projected Emittance High Rejection Factor with realistic measurement errors

  6. 2D Measurement simulation with 4 wires scanners Calculated projected emittance Only 4 scanners – shorter, cheaper Scan in x and y separately Coupling is inferred from difference between measured and expected emittance – it seems this is good enough! Unperturbed projected emittance

  7. Correction procedure • Perturb beam with skew quads • Measure beam parameters with scanners • Infer coupling • Calculate skew correction • Apply to skew quadrupoles • (Iterate)

  8. Skew Quad Scanning Scan quad strength around nominal value to find minimum Fit parabola Extract parameters

  9. Coupling Correction in Action Projected/Actual emittance Skew Quad Scan Number

  10. Application1: ATF2

  11. Application 2: ILC BDS Skew Section

  12. Summary and Future Plans • Use ‘real’ ILC errors • Investigate alternative 4D methods • Investigate 2D/4D and/or BPM method • Incorporate simulation of Laserwire • Tweaking of ATF2/ILC optics

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