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Chromaticity during ramp

CERN, 8 th March 2011. Chromaticity during ramp. E. Todesco CERN, Geneva Switzerland Ackowledgements : M. Streczlycz , N. Aquilina , W. Venturini Delsolaro , M. Lamont. RECONSTRUCTION OF CHROMATICITY DURING RAMP. Four cases – injection times from 30 min to 20 hours

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Chromaticity during ramp

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  1. CERN, 8th March 2011 Chromaticityduringramp E. Todesco CERN, Geneva Switzerland Ackowledgements: M. Streczlycz, N. Aquilina, W. VenturiniDelsolaro, M. Lamont

  2. RECONSTRUCTION OF CHROMATICITY DURING RAMP • Four cases – injection times from 30 min to 20 hours • In all cases chromaticity is measured continuously • From chroma measured we subtract the trim put in the MS, and the bare chroma • If the model (static and snapback) were perfect we would have zero Chromaticityw.r.t. nominal duringramp on 28 February

  3. RECONSTRUCTION OF CHROMATICITY DURING RAMP • At the end of the ramp the model is perfect (within a few units of chroma) • At injection chroma is undercorrected of about 10-20 units Chromaticityw.r.t. nominal duringramp on 28 February

  4. UNDERCORRECTION AT INJECTION • At injection chroma is under corrected of about 10-20 units • The hysteresis of MS can be the cause: • Their setting at injection are about 5 A and 8 A • At 5 A the hysteresis is about 10% • Natural chroma is 82-86 • Nearly 10 units not corrected • Including MS hysteresis we should bring down injection values of about 8 units Chromaticityw.r.t. nominal duringramp on 28 February

  5. SNAPBACK AMPLITUDE Chromaticityw.r.t. nominal duringramp on 28 February (18.5 hoursat injection) Chromaticityw.r.t. nominal duringramp on 26 February (20 hoursat injection) Chromaticityw.r.t. nominal duringramp on 24 February (12 hoursat injection) Chromaticityw.r.t. nominal duringramp on 22 February (30 minutes at injection)

  6. SNAPBACK AMPLITUDE • If we have a perfect correction of the decay amplitude, H and V chroma have the same value • H chroma increases during decay • If H is lower than V, over correction of decay amplitude – in this case 2 units of chroma, i.e., 0.05 of b3 Chromaticityw.r.t. nominal duringramp on 26 February (20 hoursat injection)

  7. SNAPBACK AMPLITUDE • If we have a perfect correction of the decay amplitude, H and V chroma have the same value • H chroma increases during decay • If H is lower than V, over correction of decay amplitude – in this case 5 units of chroma, i.e., 0.1 of b3 Chromaticityw.r.t. nominal duringramp on 26 February (12 hoursat injection)

  8. SNAPBACK AMPLITUDE • If we have a perfect correction of the decay amplitude, H and V chroma have the same value • H chroma increases during decay • If H is lower than V, over correction of decay amplitude – in this case 10 units of chroma, i.e., 0.2 of b3 Chromaticityw.r.t. nominal duringramp on 26 February (30 minutes at injection)

  9. SNAPBACK AMPLITUDE: summary • Today we have a 0.4 units correction of snapback • Independently of the injection time • For short injection times we are overcorrecting • Anyway not far from the data of decay

  10. THE PYRAMID • Including the hysteresis in MS and evaluating the snapback based on the decay with time we should • Bring the injection values from 10-20 to around zero • Bring the H and V on the same values • Still a mystery is the pyramid (side effect of hysteresis ? Too fast constant time?)

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