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Update on snapback analysis in the main LHC dipoles

CERN, FiDeL meeting, 27 th April 2010 . Update on snapback analysis in the main LHC dipoles. Nicholas Aquilina TE-MSC-MDA Acknowledgements : L. Fiscarelli , G. Montenero , L. Walckiers for measurements L. Bottura , N. Sammut , E. Todesco for fits and model. Contents.

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Update on snapback analysis in the main LHC dipoles

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  1. CERN, FiDeL meeting, 27th April 2010 Update on snapback analysis in the main LHC dipoles Nicholas Aquilina TE-MSC-MDA Acknowledgements: L. Fiscarelli, G. Montenero, L. Walckiers for measurements L. Bottura, N. Sammut, E. Todesco for fits and model

  2. Contents • Method • Verification of ∆bnvs IFT, tpreperation and dI/dt • Estimate of gnSB

  3. Method used • In order to model the static part (baseline), the region of decay and snapback was removed (red and green)

  4. Method used • Corresponding b3 component • Snapback fit carried out on a 10 A region 10 A

  5. Fit error • 10/10: Region of snapbackremoved = 10A, region of snapback for fit = 10A • 30/30: Region of snapbackremoved = 30A, region of snapback for fit = 30A • 10/30: Region of snapbackremoved = 30A, region of snapback for fit = 10A • Maximum error in the first 70A afterbeginning of snapback

  6. Fit error • 10/10: Region of snapbackremoved = 10A, region of snapback for fit = 10A • 30/30: Region of snapbackremoved = 30A, region of snapback for fit = 30A • 10/30: Region of snapbackremoved = 30A, region of snapback for fit = 10A • Maximum error in the first 70A afterbeginning of snapback

  7. Measurements available

  8. Equations • Powering history dependence of ∆bn • Snapback analysis • Linear correlation

  9. Results: LHC cycle-Flattop current dI/dt = 10A/s IFT = varying tFT = 1000s tPRE = 1000s

  10. Results: LHC cycle-Flattop current dI/dt = 10A/s IFT = varying tFT = 1000s tPRE = 1000s

  11. Results: Standard-Ramp rate dI/dt = varying IFT = 11.85kA tFT = 1000s tPRE = 0s

  12. Results: Standard-Ramp rate dI/dt = varying IFT = 11.85kA tFT = 1000s tPRE = 0s

  13. Results: LHC cycle-Preparation time dI/dt = 10A/s IFT =11.85kA tFT = 1000s tPRE = varying

  14. Results: LHC cycle-Flattop current • 2kA move back to a reasonable place

  15. Results: LHC cycle-Flattop current

  16. Results: Standard-Ramp rate

  17. Results: Standard-Ramp rate

  18. Results: Standard-Preparation time

  19. Results: Standard-Preparation time

  20. Conclusions • Fitting the snapback over the first period of 10 A givesbetterresults • This part is not affected by the error in the baseline • b3 andb5 versus IFT, tPRE and dI/dtfollow the model • Correlationb3 - I3agreeswith model (0.176) • Correlationb5 - I5 to becorrected (0.028)

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