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 3 rd Joint HiLumi LHC-LARP Annual Meeting, November 2013, Daresbury Laboratory

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 2

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 3  these interactions generate showers entering the detector region

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

TCTHTCTV x[cm] z [cm] example of vertical halo distribution Simulation Setup for Beam-Halo 5 Halo simulation in 2 steps: 1.beam tracking through machine using SixTrack ATS optics new aperture model use 2 types of halo input distribution to SixTrack – vertical + horizontal distribution 2.shower generation at detector interface with Fluka force inel. interaction at position given by SixTrack

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! 6

Normalisation local beam-gas (BG): use high pressure levels only (due to high uncertainties) 1.start-up 2.after conditioning 7 Both data, BH and BG, especially the pressure profiles, are given for the nominal HL-LHC scenario, i.e. 2.2 x p/bunch, 2808 bunches, 25 ns, E beam = 7 TeV Normalisation considers 2 scenarios for BH and BG beam-halo (BH): 1.beam lifetime of 12 min – corresponds to design parameter of collimation system 2.beam lifetime of 100 h – according to operation experience in 2012

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: σ x = σ y nominal collimator settings as in the design report (WP5, Task 3), possibly optimistic for background ✗ more relaxed collimator settings ✗ flat beam: σ x ≠ σ y – different collimator settings (as above) 8

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

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

Energy Spectra of Proton Rates at 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 11

Energy Spectra of Muon Rates at 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 TeV analysis published in NIMA, 729:21, 825–

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

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

Energy Spectra of Electron/Positron Rates at interface plane 15 high energy electrons expected mostly from beam-gas

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

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

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. 18

Additional slides 19

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

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

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

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) 23

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) 24