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Chromaticity decay during injection – symmetry between horizontal and vertical decay

CERN, FiDeL meeting, 14 th February 2012 . Chromaticity decay during injection – symmetry between horizontal and vertical decay. Nicholas Aquilina TE-MSC-MDT Acknowledgements: E. Todesco. Scope of the study.

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Chromaticity decay during injection – symmetry between horizontal and vertical decay

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  1. CERN, FiDeL meeting, 14thFebruary 2012 Chromaticity decay during injection – symmetry between horizontal and vertical decay Nicholas Aquilina TE-MSC-MDT Acknowledgements: E. Todesco

  2. Scope of the study • To check if the chromaticity decays by the same amount in the horizontal and vertical plane • Correction is applied through the spool pieces • one corrector to correct for both planes

  3. Data used • Beam measurements performed during weeks 18 to 25 (during 2011) equivalent to fills 1755 to 1898 (45 cases) • In these measurements the spool pieces had the same current for all ramps • Full correction was obtained by using the lattice sextuples

  4. Results • From the measured chromaticity, the lattice sextupoles corrections were removed • Correction from the spool pieces was not removed (as it was the same for all cases) • Effectiveness of the spool correction was observed • Behaviour of the bare machine is also known

  5. Examples (1) • Chromaticity behaviour is stable (therefore the spool correction was enough to correct for the decay). This implies that the decay behaviour was symmetric

  6. Examples (2) • Chromaticity decays by the same amount in both planes

  7. Examples (3) • Decay in the horizontal plane is about 1 unit more than that in the vertical plane 4 units 3 units

  8. Examples (4) • Difference of 2 units is observed between the horizontal and vertical plane

  9. Examples (5) • Difference of 2 unit is observed between the horizontal and vertical plane

  10. Examples (6) • Difference of 2 unit is observed between the horizontal and vertical plane 8 units 6 units

  11. Conclusions • Chromaticity decays by 22 units during injection, if left uncorrected • Maximum asymmetry of 2 units of chromaticity • This was observed in 18% of the cases analysed

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