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-->The intense beams and large cross sections at the LHC give rise to high flux of background throughout the ATLAS detector cavern. This background, composed mainly of low energy neutrons and photons, can cause radiation damage to detector elements and front-end electronics. The induced hits increase detector occupancy. It is important to properly simulate this background so we can understand the sources and attempt to shield them. Cavern background is also crucial for sLHC upgrade.
ATLAS carried out such a calculation several years ago. It used the detector and shielding geometries knwon at that time. This calculation needs to be updated now to reflect the current geometries. SLAC is spearheading this effort.
Tool
It is generally accepted that the physics modeling in the FLUKA package gives the best agreement with data for the low-energy neutrons and photons that are important here. On the other hand, ATLAS has little expertise with FLUKA but has much experience with Geant4, which is regarded as having a more flexible geometry definition. We therefore decided to use FLUGG, which couples Geant4 geometry with FLUKA physics.
Validation
The earlier studies made by the ATLAS Radiation Task Force is available as Doc XYZ. We will use the same geometry as in this report, and compare the FLUGG results with the FLUKA results from the Task Force.