1 / 21

UPDATE ON DYNAMIC APERTURE SIMULATIONS

UPDATE ON DYNAMIC APERTURE SIMULATIONS. M. Giovannozzi For the AB/ABP-LHC Optics and Commissioning Section Protocol of DA computation and target Main studies: MQM and MQY MQX MQTL Analysis of the performance of the DA protocol Outlook Acknowledgements: S. Fartoukh.

liana
Download Presentation

UPDATE ON DYNAMIC APERTURE SIMULATIONS

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. UPDATE ON DYNAMIC APERTURE SIMULATIONS M. Giovannozzi For the AB/ABP-LHC Optics and Commissioning Section Protocol of DA computation and target Main studies: MQM and MQY MQX MQTL Analysis of the performance of the DA protocol Outlook Acknowledgements: S. Fartoukh M. Giovannozzi - XIX LHC MAC Meeting

  2. Protocol of DA computation and target - I • Massive tracking of initial conditions for sufficient number of turns to determine stability of initial condition. • Conditions: • 105 turns • Initial conditions distributed along 5 directions in the (x, y) phase space • 15 initial conditions (couples for Lyapounov exponent evaluation)/beam sigma • Scan from 8-20 sigma • Momentum offset set to 0.75×10-3 -> ¾ of bucket height • 60 realisations of the LHC lattice for random magnetic errors M. Giovannozzi - XIX LHC MAC Meeting

  3. Protocol of DA computation and target - II • Machine model: • Optics version: V6.4 with nonlinear package correctors in Q3 moved -> effectively V6.5 optics • Magnetic errors: • Only nonlinear imperfections • Magnetic errors are derived from: magnetic models and/or measurement • Machine status: mainly injection M. Giovannozzi - XIX LHC MAC Meeting

  4. Protocol of DA computation and target - III • Recap of targets for DA value: • Injection: 12 sigma • Margin from simulations at injection to reality: factor of 2 • Break down of contributions to DA uncertainty • Extrapolation to 107 turns 7 % • Finite mesh size in tracking 5 % • Amplitude ratio 5 % • Linear imperfections 5 % • Time-dependent effects 10 % • Ripple 10 % • Safety margin 20 % CPU-time M. Giovannozzi - XIX LHC MAC Meeting

  5. Aim of the studies • Define target values of the field quality of the magnets. • Magnet production/installation is in full swing, hence: • DA is used to provide feedback on the field quality of the magnets with impact on the hardware, e.g. change of cross section -> main dipoles and quadrupoles • DA is used to assess impact of field quality of magnet classes whenever this deviates from beam dynamic targets M. Giovannozzi - XIX LHC MAC Meeting

  6. Main studies: MQM and MQY - I • MQM: • Three types (MQM, MQMC, MQML) depending on length. • Used in the dispersion suppressor and matching sections • MQY • Large aperture quadrupoles used in the matching sections • Issues: • Wide range of powering values at injection -> hysteresis effects cannot be neglected • Sometimes located in regions with high beta-values, e.g. IR4/6. • Approach: • Scan each multipole around the measured value of a given mutipole to determine acceptable ranges. M. Giovannozzi - XIX LHC MAC Meeting

  7. Main studies: MQM and MQY - II Typical values for the optical functions for MQY quadrupoles Values comparable with max beta-functions for MQM-like quadrupoles M. Giovannozzi - XIX LHC MAC Meeting

  8. Main studies: MQM and MQY - III DA reduction at large angle Systematic value of b10 for MQY Scan over MQY multipoles M. Giovannozzi - XIX LHC MAC Meeting

  9. Main studies: MQM and MQY - IV DA reduction at small angle Scan over MQY multipoles M. Giovannozzi - XIX LHC MAC Meeting

  10. Main studies: MQX Impact of measured field quality of triplet quadrupoles at injection. Impact on DA at small angles M. Giovannozzi - XIX LHC MAC Meeting

  11. Main studies: MQTL - I • Long trim quadrupoles used: • As correctors (i.e. combined with an MQ) in all Q11 and Q10, Q9, Q8, Q7 in IR3/7 • Main quadrupoles in Q6 assembly in IR3/7 • Field quality feature a large systematic b10 of about 15 units. • Feed down effects due to vertical closed orbit, generating a9 (see impact on DA for MQY) were checked. M. Giovannozzi - XIX LHC MAC Meeting

  12. Main studies: MQTL - II Magnetic errors computed as feed-down from the measured field quality of random orbit (4 mm) are used. No dramatic impact on DA M. Giovannozzi - XIX LHC MAC Meeting

  13. Summary of results - I Minimum DA (over angles) decreased from 11.2 -> 10.4 All magnets, but MBs and MQs, reduce DA by 1 sigma M. Giovannozzi - XIX LHC MAC Meeting

  14. Summary of results - II Loss of DA visible also on average DA. M. Giovannozzi - XIX LHC MAC Meeting

  15. Analysis of the performance of the DA protocol - I • Detailed analysis of dependence of the DA estimate on: • Number of angles -> pushed up to 103 (for 60 realisations) • Number of realisations -> pushed up to 600 (for 5 angles) • The model used is LHC, optics V6.4 (injection) with errors in • Main dipoles • Main quadrupoles • Cold separation dipoles M. Giovannozzi - XIX LHC MAC Meeting

  16. Analysis of the performance of the DA protocol: angle dependence Minimum DA (over realisations and angles) vs. # angles qNangles, i = 90° i /(Nangles +1), 1 < i < Nangles This indicates that about 20-50 angles should be used ~ 5% -> corresponding to the allocated budget M. Giovannozzi - XIX LHC MAC Meeting

  17. Analysis of the performance of the DA protocol: realisation dependence - I M. Giovannozzi - XIX LHC MAC Meeting

  18. Analysis of the performance of the DA protocol: realisation dependence - II This indicates that about 300 realisations should be used -> not feasible This spread is much reduced for the most realistic LHC model -> this might mitigate the need for more realisations M. Giovannozzi - XIX LHC MAC Meeting

  19. Outlook - I • Present status of DA studies: • Minimum (over realisations and angles) DA is 10.4 sigma • The model used is the most complete possible -> magnetic errors from simulations gradually replaced by those results from magnetic measurements and all classes of magnets are included • Improvement of the model: • Move to the latest optics version V6.500 • Improvement of the protocol for DA computation • Increase number of angles and realisations M. Giovannozzi - XIX LHC MAC Meeting

  20. Outlook - II • Next step • Take into account slot assignment activity from Magnet Evaluation Board • Take into account pre-assignment of magnets, e.g. all SSS are already pre-assigned • Assign actual measured errors • General comment: • The field quality of each individual is taken into account in the slot allocation process, e.g.: • b2 for quadrupoles (beta-beating) • b1, a2, b3 for dipoles (corrector strength, coupling, 3rd order driving term) • The impact on DA is yet to be evaluated. M. Giovannozzi - XIX LHC MAC Meeting

  21. Outlook - III • Tools • Software tool developed by Colleagues in AT/MAS-MA to gather information from databases (magnetic and slot allocation) • New routines to assign measured errors in MAD-X developed inside AB/ABP-LOC • First result: beta-beating correction based on the best estimate of the distribution of b2 errors in the machine as-installed M. Giovannozzi - XIX LHC MAC Meeting

More Related