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Simulation studies of proton and heavy-ion cleaning with 2018 optics

Simulation studies of proton and heavy-ion cleaning with 2018 optics. N. Fuster-Mart ínez, A. Abramov, R. Bruce, A. Mereghetti, D. Mirarchi, J. Molson, S. Redaelli On behalf of the LHC Collimation and OP team. LHC Collimation WG meeting 3/1/2018. Outline.

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Simulation studies of proton and heavy-ion cleaning with 2018 optics

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  1. Simulation studies of proton and heavy-ion cleaning with 2018 optics N. Fuster-Martínez, A. Abramov, R. Bruce, A. Mereghetti, D. Mirarchi, J. Molson, S. Redaelli On behalf of the LHC Collimation and OP team LHC Collimation WG meeting 3/1/2018

  2. Outline • 2018 proton run optics collimation cleaning studies • Introduction to the simulations • Simulation results and comparison with measurements • Summary and outlook • First 2018 ion run optics collimation cleaning simulation • Introduction to the simulations • First results • Summary and outlook

  3. Introduction to proton cleaning simulations 2018 • Motivation: • Reference loss maps of 2018 optics operation. • Contribute to the understanding of agreement of prediction tools with real data. Physics SixTrack simulation inputs LHC 2018 cycle: • Optics version: • …/opticsfile.24_ctpps2 (25 cm) • …/opticsfile.23_ctpps2 (27 cm) • …/opticsfile.22_ctpps2 (30 cm) • Beam: • 6.5 TeV • pencil beam at TCP (5-5.04 𝜎) Squeeze (b*= 0.3/10/0.4/1 m) Ramp&Squeeze (b*= 1/10/1/3 m) Xing Lev. XRP IN Coll. All IPs β* Lev. Inj.

  4. Collimator settings Collimator settings: Flat top and Physics optics 2018

  5. Simulation results B1H different β* β*= 25 cm 130 µrad sep=0 Small differences at the TCTs IP1/5/6 β*= 27 cm 130 µrad sep=0 β*= 30 cm 160 µrad sep=0 • Similar loss patter between differentβ*

  6. Simulation results B1H different β* IR7 β*= 25 cm 130 µrad sep=0 β*= 27 cm 130 µrad sep=0 β*=30 cm 160 µrad sep=0 • Same average inefficiency in all DS1/2/3.

  7. Losses at the TCTs summary B2 B1 β* change β* change • Qualitative good agreement of the trend as we decrease β*. • Measured levels of inefficiency on the TCTs higher by one order of magnitude or more than simulations. • Could be due to BLM response – CWG#206 2016 E. Skordis “TCT BLM response from tertiary halo at 6.5 TeV”.

  8. DS1 and DS2 cleaning inefficiency B2 B1 β* change β* change • No significant change of the inefficiency on the β* levelling as observed in measurements. • Level of inefficiency between measurements and simulation by a factor 4 to 10. • Higher measurements could be due to BLM response – CWG#206 2016 E. Skordis “TCT BLM response from tertiary halo at 6.5 TeV”.

  9. Simulation results and measurements B1H 25 cm β* Simulations Not observed in measurements Measurements TS1 2018 real! real! fake • Not observed cold spikes in measurements could be explain by orbit/misalignment of the TCP. • By comparison with previous simulation studies (R. Bruce, CWG 2017.10.09 B1H β*=55 cm) • Asymmetric TCP settings to complete the study for a better comparison with measurements.

  10. Simulation results and measurements B1H 25 cm β* Simulations Measurements TS1 2018

  11. Simulation results and measurements B1V 25 cm β* Simulations MeasurementsTS1 2018 real! real! real!

  12. Simulation results and measurements B2H 25 cm β* Simulations Measurements TS1 2018 real! real! real!

  13. Simulation results and measurements B2V 25 cm β* Simulations Measurements TS1 2018 real! real!

  14. Summary and outlook on proton simulations • Proton collimation cleaning simulations have been performed and compared with measurements for the 2018 β* levelling optics. • Differences between the three optics studied mainly at the TCTs in IP1/5 due to the tightening of the TCTs gaps in units of 𝜎 as β* is decreased. • The comparison of simulations with measurements shows a qualitative good overall agreement although some discrepancies are present. • OUTLOOK • Asymmetric TCP simulations could be performed for a better understanding of agreement between simulations and measurements.

  15. Introduction to ion cleaning simulations 2018 • Motivation: • The operation with heavy-ion beams at 6.37 Z TeV is more demanding for the collimation system. • In 2015 operation losses in the IR7 DS caused several dumps -> could limit the use of available intensity. • Crucial to perform cleaning simulations and validate the collimator settings for the 2018 ion run. hiSixtrack-FLUKA coupling (FLUKA PRO and SixTrack v5) (Thanks to FLUKA team and P. Hermes) • New 2018 ion optics (S. Fartoukh) -> essentially the nominal optics for the HL-LHC Pb-Pb • Optics simulated: Physics ->Optics file: /afs/cern.ch/eng/lhc/optics/runII/2018/ION/Opticsfile.21 • BFPP bumps in ATLAS and CMS off • Negative LHCb and ALICE polarity • Beam • 6.37xZ TeV, N=6x106208Pb+82 ions • Impact parameter at the TCP: 1 µm (max. ineff. in DS1/2 in the 2015 ion run simulations)

  16. Collimator settings Preliminary collimator settings • Smallest aperture expected in Q2R2 about 11𝜎 calculated with MADX (Tolerances: CERN-ACC-2014-0044) -> to be confirmed experimentally. • Changes whit respect to the proton collimator settings: • TCTs in IP1/2/5 • TCSP and TCDQ in IP6 (not ATS optics, no difference B1/B2)

  17. Simulation results: B1H Physics • Higher cold losses in DS1 and DS2. • Highest DS1 peak among beams and planes ~9.4x10-3. • Higher integrated losses inefficiency in DS2 and higher peak in DS1. • Higher losses at the TCTs among the IPs in IP1/2 ~ 10-3. • Similar loss pattern for B1V. DS1 DS2 DS3

  18. Simulation results: B2V Physics • Higher cold losses in DS1 and DS2 with maximum peak ~2.6 10-3 (a factor 4 lower than B1H). • Higher losses at the TCTs among the IPs in IP6 ~ 10-3. • Higher integrated losses inefficiency and higher peak in DS1. • Similar loss pattern for B2H. DS1 DS2 DS3

  19. Summary of inefficiencies in IR7 DS • Highest inefficiency peak in DS1 for B1H. • Highest integrated inefficiency in DS1 and DS2 for B1V.

  20. First comparison with 2015 ion run: B2H 2018 optics B2H • Some 2015 values for B2H: • Quench test: BLM MBB6L7 (2.2+/-0.4) x10-2 • EoS measured: BLM MQ9L7 (1.4+/-0.4) x10-2 • hiSixTrack-FLUKA: MBB9L7 (2.4+/-0.4) x10-3 • B2H cold cleaning inefficiency along the ring and in the DS1/2 (1.9x10-3) similar level as in the 2015 ion run, we are similar situation. P. Hermes P.h.D thesis

  21. B1H Physics: Asymmetric TCP • Study of possible strategies to reduce the cleaning inefficiency in the IR7 DS magnets. Dominated by first turn 206Pb +82 from TCP

  22. B1H Physics: Asymmetric TCP IR7 DS1 DS2 DS3

  23. Summary of inefficiencies in IR7 DS for asymmetric TCP • POSITIVE JAW ONLY: • Alleviates some high cold losses along the ring. • Highest impact in DS3 by about 70% -> however this is not the limiting location. • DS1 peak reduced by 5%. • DS1 integrated losses inefficiency by 40%. • In DS2 almost no impact. • Low impact observed in DS1 and DS2

  24. Summary and outlook • First collimation cleaning simulations has been performed for the new 2018 ion optics and a first proposal for the collimator settings have been made. • Higher cold losses along the ring observed in DS1 being B1H the worst case with an inefficiency in the order of ~1x10-2. Similar or lower levels as in the 2015 ion-run simulations. • Asymmetric simulations performed for B1H (one TCP jaw at a time) to investigate the possibility of improving the overall inefficiency. Some high spikes in the arcs in IR8/1/2 are alleviated if only one jaw is inserted but small impact is observed in the IR7 DS. • OUTLOOK • Detailed cold spikes and DS analysis for a better understanding of the origin of the losses and the asymmetric simulation observations. • ASD simulations to validate the TCTs settings.

  25. Back up …

  26. Simulation results: B1H separation bump ON/OFF Separation bumps ON 25 cm 130 urad Separation bumps OFF 25 cm 130 urad • No significant differences observed on the cold losses and at the collimators.

  27. Simulation results and measurements comparison R. Bruce, CWG 2017.10.09 “Previous studies on collimator settings for improved impedance” B1H β*=55 cm: simulations with only LEFT jaws showed a better cleaning and less cold losses Asymmetric TCP settings to complete the study for a better comparison with measurements -> orbit and/or TCP small misalignements could explain

  28. Simulation results B1V 25 cm β* Simulations Measurements TS1 2018

  29. Simulation results B2H 25 cm β* Simulations Measurements TS1 2018

  30. Simulation results B2V 25 cm β* Simulations Measurements TS1 2018

  31. B1V Physics • Higher cold losses in DS1 and DS2 with maximum peak ~7.3 10-3. • Integrated losses inefficiency and peak very similar in DS2 and DS1. • Higher losses at the TCTs among the IPs in IP1/2 ~ 10-3.

  32. B2H Physics • Higher cold losses in DS1 and DS2 with maximum peak ~1.8 10-3. • Higher losses at the TCTs among the IPs in IP6/2 ~ 10-3. • Higher integrated losses inefficiency in DS2 and higher peak in DS1.

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