FLUKA simulations of machine-induced background from local beam-gas for HL-LHC

• machine configuration:
  
• 7 TeV,
  
• beta*=15cm, optics version HL-LHC 1.0,
  
• nominal collimator settings - TCTs at 8.3 sigma
• Layout in the FLUKA model  (L. Esposito, A. Lechner, N.V. Shetty et al).:
• 2013 layout version - still preliminary IR layout (FLUKA geometry IR1,FLUKA geometry IR5)
  
• TCTs assumed to be located 131.8/133.5 m from the IP
• the assumed TAN aperture used in the FLUKA model (elliptical, with H and V semi-axes of 4.1 cm and 3.7cm) is not the final one, and the TAN vacuum chambers for both beams were assumed to be parallel (which will not be the case)
• The concrete shielding blocks (JSCA), which are currently installed between D1 and TAN, were not included in the simulations since they are not yet defined
• Interface plane at 22.6m from IP, where all particles are scored
  
• Beam-gas interactions and pressure profile (pressure profile by G. Bregliozzi and R. Kersevan):
• only beam-gas interactions up to the TAN were considered since the matching section layout was not yet defined
• two different states of machine conditioning were assumed: 1) start-up, 2) conditioned machine. Separate data files are available for 1) and 2).
  
• the conditioning assumes a decrease of the electron and photon desorption yield by a factor 100, as well as a decrease of the electron flux by a factor 10
• the profile for each machine state is affected by about one order of magnitude uncertainty due to uncertainties in layout, effective dimensions and available pumping speeds; the pressure profiles used in the simulations reflect the most pessimistic assumptions
• the gas pressure profiles do not take into account dynamic effects encountered during operation (e.g. HOM, thermal heating of equipment)
• Normalization:
• for each case, the gas pressure profiles were decomposed according to their elemental composition (hydrogen, carbon and oxygen nuclei) and FLUKA simulations of proton-nucleus interactions were run individually for each nuclei species assuming a flat spatial distribution along s
  
• the background for a given machine conditioning state hence comprises interactions on all three elemental constituents (i.e. all three constituents need to be taken into account in follow-up simulations)
• the actual gas density variation along the s-coordinate was incorporated afterwards by adjusting accordingly the weight of a particle crossing the scoring plane (column number 4)
• apart from reflecting the density variation, the weighting factors are normalized wrt the interaction probability for the respective nuclei species in the entire s-range considered and they are expressed to be per proton bunch per second (assuming a bunch intensity of 2.2E11 protons) 
• all secondary particles contained in a file, which have the same event number (column 1), originate from the *same* beam-gas interaction and hence they have to be loaded together
• results of beam-gas simulations are contained in separate files each corresponding to 2000 beam-gas interactions
  
• Cutoff at 20 MeV

Data files with particles entering the interface plane:

• IR1 B2, startup machine. Simulation done by N. Shetty and A. Lechner
• Data file of particles at the interface plane for machine startup (454000 inelastic beam-gas interactions), carbon
• Data file of particles at the interface plane for machine startup (412000 inelastic beam-gas interactions), oxygen
  
• Data file of particles at the interface plane for machine startup (476000 inelastic beam-gas interactions), hydrogen
  
  
• IR1 B2, conditioned machine. Simulation done by N. Shetty and A. Lechner
• Data file of particles at the interface plane for conditioned machine (454000 inelastic beam-gas interactions), carbon
• Data file of particles at the interface plane for conditioned machine (412000 inelastic beam-gas interactions), oxygen
  
• Data file of particles at the interface plane for conditioned machine (476000 inelastic beam-gas interactions), hydrogen
  
  
• IR5 B2, startup machine. Simulation done by N. Shetty and A. Lechner (*)
• Data file of particles at the interface plane for machine startup (224000 inelastic beam-gas interactions), carbon
• Data file of particles at the interface plane for machine startup (224000 inelastic beam-gas interactions), oxygen
  
• Data file of particles at the interface plane for machine startup (202000 inelastic beam-gas interactions), hydrogen
  
  
• IR5 B2, conditioned machine. Simulation done by N. Shetty and A. Lechner (*)
• Data file of particles at the interface plane for conditioned machine (224000 inelastic beam-gas interactions), carbon
• Data file of particles at the interface plane for conditioned machine (224000 inelastic beam-gas interactions), oxygen
  
• Data file of particles at the interface plane for conditioned machine (202000 inelastic beam-gas interactions), hydrogen
  
  
(*) IR5 files updated in July 2014 to correct geometry error (in addition, beam screen was changed to early 2014 version)

Data columns in the files:

1. primary event number
2. FLUKA particle type ID
3. particle generation number
4. Stastical weight
5. x (cm)
6. y (cm)
7. directional cosine w.r.t X-axis
8. directional cosine w.r.t Y-axis
9. Total energy (GeV)
10. Kinetic energy (GeV)
11. particle age since primary event (sec)
12. x coordinate of initial inelastic proton interaction in TCT or on beam-gas (cm)
13. y coordinate of initial inelastic proton interaction in TCT or on beam-gas (cm)
14. z coordinate of initial inelastic proton interaction in TCT or on beam-gas (cm)