1 / 17

Beam optics requirements for quadrupoles and correctors

Beam optics requirements for quadrupoles and correctors. Alignment tolerances Transfer function issues Other issues Correctors Summary Acknowledgements: O. Brüning, S. Fartoukh, J.-B. Jeanneret, J.-P. Koutchouk, A.-M. Lombardi. Alignment tolerances: MQs - I. Transverse displacement:

jules
Download Presentation

Beam optics requirements for quadrupoles and correctors

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Beam optics requirements for quadrupoles and correctors Alignment tolerances Transfer function issues Other issues Correctors Summary Acknowledgements: O. Brüning, S. Fartoukh, J.-B. Jeanneret, J.-P. Koutchouk, A.-M. Lombardi M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  2. Alignment tolerances: MQs - I • Transverse displacement: • Impact on available aperture • Impact on rms closed orbit • Impact on closed orbit corrector strength • Tolerances take into account • random b1 in main dipoles • MQ misalignment • Beam Position Monitor (BPM) misalignment M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  3. Alignment tolerances: MQs - II S. Fartoukh LHC Project Note 260 • Roll angle: • Impact on coupling • Values of tolerances Alignment Mini-Workshop (Dec. 2000), LHC Project Note 297, LHC Project Report 397 M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  4. Alignment tolerances: DS and MS quads - I • Similar arguments hold as for MQs, but • Aperture is tighter (higher values of beta-function) The situation can be improved by reducing b*, but there are still limits in Q10/Q11 S. Fartoukh 23 LTC Meeting “New optics solutions in IR1 and IR5” (31 March 2004) M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  5. Alignment tolerances: DS and MS quads - II IR2 – Beam2 IR8 – Beam1 O. Brüning 23 LTC Meeting “New optics solutions in IR2 and IR8” (31 March 2004) M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  6. Alignment tolerances: DS and MS quads- III Values of tolerances (assuming realignment after one year) A. Verdier, presentation at the MEB meeting Measurements of geometric/magnetic axes are required M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  7. Transfer function issues - I • Gradient errors generate: • Tune variation • Beta-beating • Spurious dispersion • Tune correction is performed by means of: • Independent small tune correction (trim quadrupoles between Q14 and Q21). • Independent large tune correction. These can be performed by using • MQTL quads: located in Dispersion Suppressors (DS). However, they induce strong beta-beating if used for generating DQ>0.1 • Retuning insertions • All this requires, either • Good knowledge of the transfer function, or • Beam based approach M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  8. Transfer function issues - II • Beta-beating (random b2): • Peak value is limited to 21% (injection) • Off-momentum beta-beating is estimated to 7% (injection) • Budget for peak beta-beating is: 14%. • Such a budget is already taken by: MBs, MQs, feed-down from nonlinear correctors. • It is found that Db/b = Cost * (random b2) • With MQs: 392 magnets MQM(C,L)s: 86 magnets MQY: 24 magnets These large values can be attained assuming quads are stronger than nominal optics (flexibility is mandatory) M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  9. Transfer function issues - III • Adding (quadratically) the contribution of DS and MS quadrupoles (assuming 10 units rms of b2) gives Db/b 14.9 % or 15.9% • The allocated budget is exceeded (small amount)! • Spurious normalised dispersion: Dx/ √b = Cost * (random b2) Tolerance at injection is set to Dx/ √b< 1.3 10-2 m1/2 b2 random of 10 units (rms) is well within budget M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  10. Other issues: squeeze - I During the squeeze, gradients of DS and MS quadrupoles will change. This requires a very good knowledge of time-dependent effects, hysteresis etc. S. Fartoukh 23 LTC Meeting “New optics solutions in IR1 and IR5” (31 March 2004) M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  11. Other issues: squeeze - II O. Brüning 23 LTC Meeting “New optics solutions in IR2 and IR8” (31 March 2004) • In general: • Q4, Q5, Q6 decrease during beta-squeeze (IR1, IR5, IR8) • QTL11, QT12, QT13 deserve special care (IR1, IR5) Measurements of time-dependent effects, hysteresis are required M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  12. Other issues: DA - I • Impact on DA of field quality of DS and MS is by far non-negligible. • Presented at FQWG (09/12/03, 21/09/04). • Initial assumption of MQ-like field quality for DS and MS quads produced a dramatic loss of DA. M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  13. Other issues: DA - II • Measured field errors for DS and MS quads improved DA. • Impact of MQMs on DA is marginal (unless at 45º). • Impact of MQYs is clearly visible, but less pronounced than before. Measurements of field quality are required M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  14. Correctors - I • Can be powered to any value => control of hysteresis • Are adjusted during setting up and commissioning => knowledge of the transfer function • Compensate for errors => field quality such that there is no effect on the DA • Nested correctors => knowledge of cross-talk • The measurement accuracy of the observable to be corrected sets the targets. M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  15. Correctors - II • Requirements were discussed at • FQWG meetings • S. Fartoukh (March 2004) • M. Giovannozzi (November 2004) • A. Lombardi (March and November 2004) • MAC meeting • A. Lombardi (July 2004) • Status of measurements in Block 4 were also reviewed at FQWG (V. Venturini Delsolaro, November 2004): • For some magnet classes the warm/cold correlations are not considered good enough, essentially because of poor statistics. • Conclusions on the strategy of magnetic measurements for corrector will be drawn in few months by FQWG. M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  16. MQs • Strategy discussed at Arc SSS Review (19 May 2004) should be pursued. • DS and MS quads • Aperture is rather critical at injection (DS quadrupoles): accurate axis (magnetic/geometric) measurements important. • Transfer function is crucial (beta-beating, IR tuning). The required accuracy is about 10 units. • Detailedmagnetic measurements (time-dependent effects, hysteresis) should be foreseen for quadrupoles with critical behaviour during squeeze. • Field quality is also crucial and should be measured. Conclusions - I M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

  17. Conclusions - II • Correctors • Targets values for the field quality (in a broad sense, including also alignment and transfer function) of correctors were presented and discussed at many FQWG meetings. This activity should be completed. • The poor statistics of magnetic measurements for some magnet classes makes the warm/cold correlations not good enough. • It is recommended to continue the spot checks of the series correctors in Block 4 (baseline). M. Giovannozzi – Review of the Tests of Superconducting Magnets in SM18

More Related