Study of cleaning performance with ATS optics for post LS1

1. Study of cleaning performance with ATS optics for post LS1 Daniele Mirarchi,Stefano Redaelli, R. Bruce On behalf of the LHC Collimation Team Special thanks to S. Fartoukh for the useful discussions and help on optics modifications Daniele Mirarchi, BE-ABP-HSS Meeting

2. Introduction Possibility to implement the ATS optics at the post LS1 LHC restart Study of its influence on cleaning performance of the collimation system are required Complete loss map simulations made for various machine and system configurations: • Collimators settings: • mm_kept • sigma_kept • Optics versions: • Nominal (NOM) • ATS Simulations made for each combination of them, for both planes and both beams at 6.5TeV Comparative studies between these 16 cases are shown in the next Daniele Mirarchi, BE-ABP-HSS Meeting

3. Configurations Collimation layout: mm_kept settings sigma_kept settings IR7-TCP same settings as in mm_kept, Nominal retraction in sigma for the rest same settings in mm as in the 2012 Key optics settings: Crossing scheme values in MADX (V.5.02.00) modified each time in order to get always the same crossing angles. Daniele Mirarchi, BE-ABP-HSS Meeting

4. “Observables” Main parameters for comparative studies of optics influence on collimation performance: • Average value of losses density in the limiting regions of the whole LHC • Integrated losses in the limiting regions of the whole LHC Average value of losses: calculated on a sub-set of bins, in which a reasonable number of primary protons are lost (to take low the statistical error, i.e. 1p in 1bin has 100% of error) • Various “threshold” were probed to identify how it effects the average value. Final threshold chosen in order to have a reasonable statistical error (<30%) and a number of bin on which make sense to perform an average and a standard deviation (min 20bins) Integrated losses:are given by the sum of all primary protons lost in “interesting” losses distributions Daniele Mirarchi, BE-ABP-HSS Meeting

5. Beam 1 Daniele Mirarchi, BE-ABP-HSS Meeting

6. ATS vs NOM, H plane NOMINAL OPTICS Whole LHC, horizontal plane, mm_kept collimator settings ATS OPTICS !!!

7. Comments on H plane New dangerous peak losses appeared just after IP8! Due to the dispersion mismatch induced by the crossing scheme! Same peaks are seen in HL-LHC simulations, but they are cured by IR7 CRYO-Collimators Many tricks tried with StephaneFartoukh to decrease those dangerous dispersive peaks after IP8: • Only difference between the two optics: IP8 β*=3m in ATS, while β*=10m in NOM Produced a NOM thin opt. with IP8 β*=3m: no significant changes seen in high of those peaks • Tried to rematch IR7-ATS with IR7-NOM values of Dx and DPx at first TCP (TCP.D6L7.B1) no significant changes seen in high of those peaks • Stephane gave me a very nice tool to insert “a fake phase kick” between cells 78 and 81 After many tests, the only phase shift would cure those peaks bringing them to NOM values would be π This would imply ~7degree per cell, which is unfeasible as Stephane told me.

8. Summary H plane IR7 ZOOM ATS OPTICS NOMINAL OPTICS Q8-9 Q8-9 Q10-11 Q10-11 Q10 BC16-QT16 QT18 ZOOM of dangerous peaks in IR8

9. “Visual” summary H plane Previous summary table in histograms mm_kept settings, average losses mm_kept settings, integrated losses ATS/NOM ATS/NOM sigma_kept settings, integrated losses sigma_kept settings, average losses ATS/NOM ATS/NOM

10. “Visual” summary H plane Bin by bin ratio: mm+ATS/mm+NOM (not significative for comparisons, just to give you the feeling) Ratio only for losses on collimators (important for possible damages) IR7

11. ATS vs NOM, V plane NOMINAL OPTICS Whole LHC, horizontal plane, mm_kept collimator settings ATS OPTICS !!!

12. Summary V plane IR7 ZOOM ATS OPTICS NOMINAL OPTICS Q8-9 Q8-9 Q10-11 Q10-11 Q10 BC16-QT16 QT18 ZOOM of dangerous peaks in IR8

13. “Visual” summary Vplane Previous summary table in histograms mm_kept settings, average losses mm_kept settings, integrated losses ATS/NOM ATS/NOM sigma_kept settings, integrated losses sigma_kept settings, average losses ATS/NOM ATS/NOM

14. “Visual” summary H plane Bin by bin ratio: mm+ATS/mm+NOM (not significative for comparisons, just to give you the feeling) Ratio only for losses on collimators (important for possible damages) IR7

15. Beam 2 Daniele Mirarchi, BE-ABP-HSS Meeting

16. ATS vs NOM, H plane NOMINAL OPTICS Whole LHC, horizontal plane, mm_kept collimator settings ATS OPTICS Daniele Mirarchi, BE-ABP-HSS Meeting

17. Summary H plane IR7-DS limiting location for the whole LHC, summary of expected losses on Q 8-9-10-11 (shown only plots for mm_kept settings, more conservative. Better performance are achieved with sigma_kept settings) NOMINAL OPTICS ATS OPTICS IR7 ZOOM Q8-9 Q8-9 Q10-11 Q10-11 Comparable performance are found, seems that with ATS slightly less and more concentrated losses

18. “Visual” summary H plane Previous summary table in histograms mm_kept settings, average losses mm_kept settings, integrated losses ATS/NOM ATS/NOM sigma_kept settings, integrated losses sigma_kept settings, average losses ATS/NOM ATS/NOM

19. “Visual” summary H plane Bin by bin ratio: mm+ATS/mm+NOM (not significative for comparisons, just to give you the feeling) Ratio only for losses on collimators (important for possible damages) IR7

20. ATS vs NOM, V plane NOMINAL OPTICS Whole LHC, vertical plane, mm_kept collimator settings ATS OPTICS

21. Summary V plane IR7-DS limiting location for the whole LHC, summary of expected losses on Q 8-9-10-11 (shown only plots for mm_kept settings, more conservative. Better performance are achieved with sigma_kept settings) NOMINAL OPTICS ATS OPTICS IR7 ZOOM Q8-9 Q8-9 Q10-11 Q10-11 Comparable performance are found

22. “Visual” summary Vplane Previous summary table in histograms mm_kept settings, average losses mm_kept settings, integrated losses ATS/NOM ATS/NOM sigma_kept settings, integrated losses sigma_kept settings, average losses ATS/NOM ATS/NOM

23. “Visual” summary H plane Bin by bin ratio: mm+ATS/mm+NOM (not significative for comparisons, just to give you the feeling) Ratio only for losses on collimators (important for possible damages) IR7

24. Conclusion Many configurations where probed to test the influence of ATS optics on the collimations system performance, with different settings, in both planes, for both beams, at 6.5 TeV. Beam 1: • Horizontal plane: • averaged and integrated losses in the DS systematically higher with ATS opt. than with NOM opt. Worst case: factor 1.4 in averaged losses, 1.7 in integrated losses • Presence of dangerous peaks in IP8, with a average losses comparable with the ones in the DS. • Vertical plane: • Comparable results are found, however ATS slightly worse than NOM • Presence of dangerous peaks in IP8, with a average losses comparable with the ones in the DS. Beam 2: • Horizontal plane: • ATS worse than NOM with a factor 1.4 in terms of average losses, but slightly better in terms of integrated losses (factor 0.9) • Vertical plane: • Comparable results are found Since the worse/comparable performance of the system with ATS w.r.t. NOM opt. further and more detailed studies are needed (i.e. coupled simulations with FLUKA to access the effects on collimators too) Work is still on-going to try to mitigate dangerous spikes at IP8 (tried also to close more the TCT, but it’s not enought)