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2010 MQW measurement campaign and updated FIDEL LHC models

2010 MQW measurement campaign and updated FIDEL LHC models. P. Hagen and E. Todesco measurements by M. Buzio, R. Chritin, J. G. Perez beta-beating analysis by R. Tomas Garcia (BE/ABP) May 2010. Lessons learnt from LHC beam commissioning.

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2010 MQW measurement campaign and updated FIDEL LHC models

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  1. 2010 MQW measurement campaign and updatedFIDEL LHC models P. Hagen and E. Todescomeasurements by M. Buzio, R. Chritin, J. G. Perezbeta-beating analysis by R. Tomas Garcia (BE/ABP) May 2010

  2. Lessons learnt from LHC beam commissioning • The measured β-beating after the FIDEL update of the MQW models in January 2010 demonstrated that there are STILL errors in the transfer function in the order of 1 or 2% in MQWA, much more in MQWB • We decided to initiate a new measurement campaign measuring 2 of the 4 spare magnets in MQWA and MQWB mode • The working assumption being that the difference in pre-cycle of series measurements vs. “as used” in LHC would be the main source of error • The I_MIN of the MQWA power supply could change in the future due to stability issues, so we added a few extra pre-cycles in the measurements, in case we would need them • The new measurements will be used to re-adjust, recalibrate the transfer of all 48 MQW A+B magnets in LHC| • Use SSW measurements for fast and precise Bdl integrals

  3. MQWA pre-cycles MQWB pre-cycle

  4. MQWA results… SSW comparison with old series meas Shape of TF wrt pre-cycle

  5. Zoom on hysteresis Shape in table format

  6. MQWA 51 shape

  7. MQWA measurement conclusions • Combine series measurements with new measurements of 4 apertures with pre-cycle “B” (I_MIN=20 A) • MQWA 51 has good match between old and new measurements for I >= 100 A • MQWA 10 was not measured during series measurements! • Assume MQWA 10 + MQWA 51 represent the population • Replace hysteresis part of old transfer function with new shape (points where I < 200 A) • No strong justification for doubting the absolute calibration of series measurements so keep the old TF geometric @ 200 A “as is” ! ?

  8. MQWA FiDeL 2010 fit of 2 magnets fit of 2 magnets fit of 2 magnets

  9. MQWA current predictions @ 450 GeV Note: I (units) is wrt new 2010 operational currents over-corrected? • In 2008 we had the original FIDEL parameters and they changed slightly in 2009 at injection • First beta-beating study in 2009 showed a 3% error at injection • Wrong pre-cycle found in Dec. 2009 and corrected. The required corrections were reduced to 1.5% (average) • The new FIDEL 2010 (not yet used) predict a stronger residual magnetisation in agreement with actual currents recorded in TIMBER, i.e. nominal 2009 settings plus trims to decrease the beta-beating • The new FIDEL 2010 gives no changes at 3.5 TeV (same geometric), i.e. FIDEL 2010 are identical to FIDEL 2009 for this range of E.

  10. MQWB results (magnet 10 and 51 = 4 apertures) BL negative for I < 2.x A! Geo @ 200 A not valid! Zoom on hysteresis

  11. MQWB comparison issueswrt series measurements MQWB measurement conclusions • The entire TF is different due to pre-cycle (not only low currents) • At best the only point from series measurement which could be re-used is at 600 A, but is not justified given the small spread at 600 A in new measurements ! • So assume MQWB 10 + MQWB 51 represent the population and use the same TF for all MQWB ! • Change TF geometric current to 437 A

  12. MQWB FiDeL 2010 Fit branch where BL>0and dI/dT > 0

  13. MQWB current predictions 450 GeV over-corrected? 3.5 TeV Old FIDEL parameters actually used Note: I (units) is wrt new 2010 operational currents • The new FIDEL 2010 prediction for 450 GeV is better in agreement with actual currents (recorded in TIMBER) to decrease the beta-beating • We have considerable differences from TIMBER at 3.5 TeV as well (slides 11 gives us 100 units systematic diff at 200 A) • The worst-cases as usual RQT5.L7 and RQT5.R7 (hardest to predict)

  14. Check of beta-beating for MQWB @ 3.5 TeV • Thanks to Rogelio Tomas Garcia for checking the estimated change of beta- beating using the new MQWB currents • The change in currents with new FIDEL 2010 versus operation should reduce the beta-beating (slightly) • The MQWB @ 3.5 TeV is not a strong source for beta-beating; around 3-5% • The greatest advantage of applying the new FIDEL parameters instead of the trim is that FIDEL is based upon a physical model whilst the trim is a linear function • Therefore the FIDEL TF should work better during the ramp where no beta-beat measurements exist to improve the trim function, and we know the FIDEL TF is non-linear due to magnetic hysteresis

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