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Collimation Backgrounds in HL-LHC

This presentation outlines the impact of collimator margins on machine-induced background in experiments and includes results from beam-halo simulation setups for the HL-LHC. Evaluation of cleaning efficiency and halo losses for round and flat beams, comparison to baseline settings, and conclusion with outlook are covered.

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Collimation Backgrounds in HL-LHC

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  1. Collimation Backgrounds in HL-LHC R.Kwee-Hinzmann (RHUL) R.Bruce (BE-ABP), F.Cerutti (EN-STI), L.S.Esposito (EN-STI), A.Lechner (EN-STI) HL-LHC Annual Meeting, 28/10/2015

  2. Outline • Introduction • Beam-halo simulation setup • Evaluation of new collimation layout in context of background • Cleaning efficiency and IR1 tertiary halo losses for round and flat beams • Experimental background with final collimation layout in IR1 • Comparison to baseline settings and Run 2 • Conclusion & Outlook R Kwee-Hinzmann

  3. Introduction Machine induced Background • Collimator margins have strong influence of “machine-induced background” to experiments • Major sources of MIB: • beam-gas: el. and inel. collisions of beam protons with residual gas-molecules such as CH4, O2, H2 • First estimate has been shown for baseline parameters in 1st annual meeting • beam-halo: halo-protons leaking from the cleaning system to the experimental areas • Today: use updated layout, 2σ-retraction collimator settings and different beam optics R Kwee-Hinzmann

  4. Collimator Settings • From TUPTY067 (IPAC15) R Kwee-Hinzmann

  5. Simulation Setup for Beam-Halo Simulation of beam-halo induced showers requires two steps: • Tracking of halo distributions through the HL-LHC, in particular considering the HL collimation system • Used SixTrack • Obtain a distribution of inelastic interactions inside the jaws of the tertiary collimators (TCTs) close to the experiments. • Shower simulations with FLUKA • Force inelastic interactions per TCT hit with beam proton. • Record each particle reaching the interface plane at 22.6 m R Kwee-Hinzmann

  6. Simulation setup for halo induced showers losses on TCTs in IR1 SixTrack lossmap in full ring TCT5H+TCT5V zoom TCT4H+TCT4V • Use right side of P1 in FLUKA to simulate showers (symmetric layout, different in IR5 –not done here) load TCT hits from h+v halo simulations into FLUKA HL-LHC layout left side of ATLAS (use symmetric right side in FLUKA) ATLAS (IP1) TCTH TCTV TCT4s TCT5s R Kwee-Hinzmann

  7. Beam halo simulationsHL-LHC • Use 15 cm optics, HL-LHC v1.0, 295 μrad half-crossing angle in SixTrack and FLUKA simulations for B1 and B2. • Note HL-LHC v1.1 fluka layout and HL-LHCv1.0 optics were used. • Study effect of additional TCT5s in the IRs (now part of the baseline) • use 2-σ-retraction collimation settings • compare to different beam optics (always HLv1.0) • Compare baseline (nominal) and 2σ-retraction settings with updated HL-LHC and final collimator layout. • frozen for HL1.1: short TAN (2.5m), D2 aperture R Kwee-Hinzmann

  8. simulation results on Effect of TCT5s R Kwee-Hinzmann

  9. SixTracklossmaps:Cleaning efficiency in HL-LHC R Kwee-Hinzmann

  10. SixTracklossmaps:Cleaning efficiency in HL-LHC R Kwee-Hinzmann

  11. IR7 Zooms round B1H TCT5s in round B2H TCT5s in 2σ-retrac. settings: • Less cold losses from B1 than from B2. • Very similar loss pattern for round and flat B1H. B1 B2 flat B1H TCT5s in R Kwee-Hinzmann

  12. Comparison of round/flat beam optics • Use the two cold cluster losses in IR7 as benchmark B1 B2 Generally similar cleaning performance for round and flat beam 1. TCT5 in/out scenarios not expected to show significant differences in IR7. R Kwee-Hinzmann

  13. IR1 Zooms round B1H TCT5s out round B2H TCT5s out round B1H TCT5s in round B2H TCT5s in R Kwee-Hinzmann

  14. IR1 Zooms round B1H TCT5s out flat B1H TCT5s out round B1H TCT5s in flat B1H TCT5s in R Kwee-Hinzmann

  15. TCT distributions in IR1positions of inelastic interactions round B2 TCT5s out round B1 TCT5s out Note the different x-range! round B1 TCT5s in round B2 TCT5s in R Kwee-Hinzmann

  16. Effect of TCT5s at interface plane • Fluka shower distributions at interface plane are normalised to stable beam operation considering • 100h of beam lifetime • @7 TeV, 2736 bunches/beam, 2.2e11 protons/bunch • @6.5 TeV, 2748 bunches/beam, 1.2e11 protons/bunch • respective leakage from TCPs to TCTs TCT4 only B1: 9.7e-5 TCT4 only B2: 2e-4 TCT5 in B1: 1e-4 TCT5 in B2: 1e-4 6.5 TeV 80 cm B1: 2.1e-5 B2: 2.8e-5 HL 1.0 15 cm R Kwee-Hinzmann

  17. Beam halo simulations Including TCT5 normalisation per TCT hit origin of muons vertical view energy distribution origin of muons above 100 GeV R Kwee-Hinzmann

  18. Beam halo simulations Energy distribution in φ for muons Energy distribution in φ R Kwee-Hinzmann

  19. Beam halo simulationscomparison B1/B2 Expect slightly more muons and more energy from muons from B1. Very similar distributions for B1 and B2. R Kwee-Hinzmann

  20. Comparison TCT5s in/outfor B1/B2 Expect improvement when TCT5s are included. R Kwee-Hinzmann

  21. Beam halo simulationscomparison TCT5 in/out Slightly more energy expected without TCT5s, more by B2. R Kwee-Hinzmann

  22. Beam halo simulationscomparison TCT5 in/out Very similar situation up to large radii. Slightly worse without TCT5s in B2. R Kwee-Hinzmann

  23. simulation results on Comparison to run2 halo

  24. Comparison of halo6.5TeV Run 2 and nominal HL Expect a factor 2-3 more particles and energy in HL. R Kwee-Hinzmann

  25. Comparison of halo6.5TeV Run 2 and nominal HL Factor 2 to 3 more muons and almost factor 4 more energy from muons. R Kwee-Hinzmann

  26. simulation results on Comparison of nominal and retracted collimator settings HL1.0

  27. Comparing the cleaning efficiency • Use IR7 cold clusters (for B1: Q8/Q10) as benchmark to compare cleaning efficiency R Kwee-Hinzmann

  28. Effect at the interface plane About x2.6 less particles and more than x3 less energy with retracted settings. R Kwee-Hinzmann

  29. Comparison of effect at the interface plane • Quite a difference at the very central region for charged particles. R Kwee-Hinzmann

  30. Conclusions and Outlook • Evaluated halo background in HL1.0 for different configurations: nominal coll, 2σ-retracted coll sett, • also looked at different beam optics • Evaluated effect of TCT5 at IR1 • Some gain is expected: about 30% to 40% particles and 20% less energy from B1, and about 50% particles and 40 % energy from B2. • Retracted settings produce less particles (x2.6) and less energy (x3.2) at the interface plane. • Observe distinct features at the very central region • Performed also failure studies (not shown here). • Future background shower studies for HL-LHC should include IR5 R Kwee-Hinzmann

  31. additional information R Kwee-Hinzmann

  32. positions of inelastic interactions nominal settings 3,320,000 primaries retracted settings 5,319,000 primaries round B1 TCT5s in R Kwee-Hinzmann

  33. phi definition transverse (x,y) plane y> 0, φ = π/2 outside LHC inside LHC φ = - π,π x > 0, φ = 0 φ = - π/2 R Kwee-Hinzmann

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