Beam Background Simulations for HL-LHC at IR1

1. Beam Background Simulations for HL-LHC at IR1 Regina Kwee-Hinzmann, R.Bruce, A.Lechner, N.V.Shetty, L.S.Esposito, F.Cerutti, G.Bregliozzi, R.Kersevan, L.Nevay, S.Gibson, S.Boogert 3rd Joint HiLumi LHC-LARP Annual Meeting, 11-15 November 2013, Daresbury Laboratory

2. Outline • Beam background sources in IR1 and IR5 • HL LHC cases for beam background simulations • Simulation setup • beam-halo • local beam-gas • Results: background spectra at the detector interface • Summary and outlook

3. Beam Background Sources to Experiments Main sources of BB in IR1 and IR5: • beam-halo leakage from tertiary collimators (TCTs) • beam-gas • local BG: sample beam-gas interactions close to IP (140 m upstream) • global BG: sample through entire LHC • other sources: cross-talk these interactions generate showers entering the detector region

4. Geometry Layout at IR1 as used in Fluka (same geometry as used for energy deposition studies –WP10) x [cm] inner triplet Q1 Q2 Q3 separation dipole (D1) interface plane at 22.6 m IP incoming/outgoing beam TCTs detector side machine side z [cm]

5. TCTV TCTH x[cm] Simulation Setup for Beam-Halo • Halo simulation in 2 steps: • beam tracking through machine using SixTrack • ATS optics • new aperture model • use 2 types of halo input distribution to SixTrack • vertical + horizontal distribution • shower generation at detector interface with Fluka • force inel. interaction at position given by SixTrack z [cm] example of vertical halo distribution

6. Simulation Setup for local Beam-Gas • Use Fluka only • Force interaction based on simulated pressure profile • Consider 2 cases for gas pressures: • start-up conditions • after conditioning • per case 2 levels: • high and low due to uncertainties in layout, effective dimensions, pumping speed all pressure profiles are highly preliminary!

7. Both data, BH and BG, especially the pressure profiles, are given for the nominal HL-LHC scenario, i.e. 2.2 x 1011 p/bunch, 2808 bunches, 25 ns, Ebeam = 7 TeV Normalisation considers 2 scenarios for BH and BG Normalisation local beam-gas (BG): use high pressure levels only (due to high uncertainties) • start-up • after conditioning beam-halo (BH): • beam lifetime of 12 min • corresponds to design parameter of collimation system • beam lifetime of 100 h • according to operation experience in 2012

8. HL LHC Beam Background Simulation Cases ATS optics with layout HLLHCv1.0 for β* = 15 cm • new larger triplet with larger apertures • larger half-crossing angle (295 μrad at IP) This talk: IR1 geometry only, present TCT layout as pessimistic assumption (not final for HL, additional TCT's further upstream are expected to help) • round beam: σx = σy • nominal collimator settings as in the design report (WP5, Task 3), possibly optimistic for background • more relaxed collimator settings • flat beam: σx≠ σy • different collimator settings (as above)

9. Neutron fluence per primary beam-halo interaction horizontal cut interface plane at z = 22.6 m TAN TCTs

10. Neutron fluence per primary beam-halo interaction vertical cut interface plane at z = 22.6 m TAN TCTs

11. Energy Spectra of Proton Ratesat interface plane distinctive differences: • clear single-diffractive peak in halo distribution • halo protons show double bump structure • lowest background possibly from halo protons during normal operation

12. Energy Spectra of MuonRatesat interface plane • many background muons to be expected for very short beam lifetimes and during start-up • BG contribution after cond. similar to level at 3.5 TeV • BH for normal beam lifetimes is about x10 higher than at 3.5 TeV • 3.5 TeV analysis published in NIMA, 729:21, 825–840 2013

13. Energy Spectra of Neutron Ratesat interface plane • triple bump structure in halo neutrons • most of the background neutrons may be expected during machine start-up

14. Energy Spectra of Photon Ratesat interface plane • expect highest rates from photons • at high energies, local BG contribution comparable to very short beam lifetimes

15. Energy Spectra of Electron/Positron Ratesat interface plane • high energy electrons expected mostly from beam-gas

16. Transverse Radial Distributions for μ± and e±at interface plane • differences at very short radii more pronounced • “shoulder” from BG is more “washed out”

17. Transv. Rad. Distrib. for Neutrons and Protons at interface plane • expect more neutrons than protons (about x10)

18. Summary & Outlook • Presented first beam background studies with updated HL geometry for design case. • Comparison of 2011 machine to HL: expect similar level of high energy muons from local BG after conditioning, but x10 increase from BH during normal operation. • Results are available to experiments for further analysis. • Preliminary results need to be updated, once • final decision on layout is made (e.g. no JSCAA shielding included in geometry), • pressure profile simulations are updated. • More HL cases in pipline • use flat optics, use more relaxed/HL collimator configurations, • extend studies to IR5, consider new HL TCT’s. • More studies for future • global beam-gas, cross-talk.

19. Additional slides

20. Proton fluence per primary beam-halo interaction horizontal cut interface plane at z = 22.6 m TAN TCTs x[cm] z [cm]

21. Proton fluence per primary beam-halo interaction vertical cut interface plane at z = 22.6 m TAN TCTs

22. Energy Distribution for Particles within or outside of beampipe many more pions arrive at the interface from halo interactions than from beam-gas.

23. Particle distribution in x-y plane at interface • geometric features visible at interface plane • see similar distribution for other particles (e.g. kaons, pions, neutrons)

24. JCSAA concrete shielding • Halo spectra at interface plane can show specific features of the HL geometry (missing JSCAA, JSCAB and JSCAC shielding in HL layout)