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Field quality versus beam dynamics targets in MQ and corrective actions

CERN, 8 th January 2004 Field Quality Working Group. Field quality versus beam dynamics targets in MQ and corrective actions. P. Hagen, E. Todesco AT-MAS-MA With the help of F. Simon, C. Vollinger. Contents. Correction for b6 Update of field quality in collared coils Randoms

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Field quality versus beam dynamics targets in MQ and corrective actions

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  1. CERN, 8th January 2004 Field Quality Working Group Field quality versus beam dynamics targets in MQ and corrective actions P. Hagen, E. Todesco AT-MAS-MA With the help of F. Simon, C. Vollinger

  2. Contents • Correction for b6 • Update of field quality in collared coils • Randoms • Systematics • Spread in field gradient P. Hagen, E. Todesco, AT-MAS-MA

  3. Correction of b6 - collared coils data • b6 in collared coils is among 3.5 and 7 units • Average:5.5 units Spread: 0.7 units (one sigma) P. Hagen, E. Todesco, AT-MAS-MA

  4. b6 - target in the collared coils • Offset between collared coil and injection • Around -4 units in series [memo by L. Bottura et al.] • Data of prototypes: -3.7 units with sigma of 0.3 units (5 apertures) • This corrects previous estimate of -2.5 units • Target range at injection [-2,0] units [A. Lombardi talk] • Beam screen: small contribution (-0.2 units) [simulations by S. Russenchuck] • Target range in collared coil: [2.2,4.2] units P. Hagen, E. Todesco, AT-MAS-MA

  5. b6 - dependence on coil protection sheet • Part of the spread is due to different coil protection sheet thickness used in the production • Between 0.87 and 0.96 mm • Model in agreement with data • Large spread • Hard to obtain 3 units • CPS too small, prestress problems • Already with 0.87 mm, prestress could be too low P. Hagen, E. Todesco, AT-MAS-MA

  6. b6 - solution proposed • Keep the coil protection sheet at 0.87 mm and add 0.125 mm in the coil midplane • Collared coils with 0.87 mm have average b6 of 5 units • According to simulations the expected shift of additional midplane is -2 units • What we should obtain • Bring b6 in the centre of the range • Give some more pre-stress to be safer for quench P. Hagen, E. Todesco, AT-MAS-MA

  7. b6 - solution proposed - side effects • Field gradient lower of 6 units • b10 lower of 0.2 units • Now at -0.1 units, will go to -0.3 units P. Hagen, E. Todesco, AT-MAS-MA

  8. b6 - solution proposed - first results • First results are in agreement with simulations P. Hagen, E. Todesco, AT-MAS-MA

  9. Update of target on systematics • New targets for systematics have been agreed with AB-ABP (see talk by A. Lombardi) • everything looks fine P. Hagen, E. Todesco, AT-MAS-MA

  10. Situation on randoms • These targets were already reviewed in June 2003 • everything looks fine, but • Problem on spread of field gradient P. Hagen, E. Todesco, AT-MAS-MA

  11. Spread of field gradient • A decrease of field gradient of around 30 units is observed after aperture 115. This is a feature due to the use of a new measuring mole (calibration problem) • Data have to be corrected soon P. Hagen, E. Todesco, AT-MAS-MA

  12. Conclusions • Systematic b6 • Correction proposed: +0.125 mm in coil midplane • First results in agreement with simulations • We should be safely inside the target range • This should also increase pre-stress • Review of targets for systematics • Some ranges have been widened • Everything is within specifications • Spread in field gradient • We see a decrease of field gradient due to the use of a new mole • Calibration should be checked P. Hagen, E. Todesco, AT-MAS-MA

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