Abstract
Background benchmarking measurements have been made to check the low-energy processes which will contribute via nuclear reactions to the radiation background in the Large Hadron Collider (LHC) experiments at CERN. Previously these processes were only evaluated with Monte Carlo simulations, estimated to be reliable within an uncertainty factor of 2.5. Measurements were carried out in an experimental set-up comparable to the shielding of ATLAS, one of the general purpose experiments at LHC. The absolute yield and spectral measurements of photons and neutrons emanating from the final stages of the hadronic showers were made with a Bi 4Ge 3O 12 (BGO) detector. The particle transport code FLUKA was used for detailed simulations. Comparison between measurements and simulations show that they agree within 20% and hence the uncertainty factor resulting from the shower processes can be reduced to a factor of 1.2.
Highlights
1 IntroductionThe Large Hadron Collider (LHC) under construction at CERN is scheduled to be operational in 2006
ATLAS, A T(oroidal) L(HC) A(pparatu)S [1], is characterized by two distinct magnetic-field systems: A superconducting solenoid will be installed around the inner-detector cavity and large superconducting air-core toroids consisting of independent coils will be arranged outside the calorimetry for the muon spectrometer
A mixed, positively charged hadron beam (π+, protons, K+) with a momentum of pbeam = 40 GeV/c or pbeam = 120 GeV/c was directed onto a 200 cm × 200 cm cast-iron wall with a thickness of 200 cm (≈ 11λ) and 240 cm (≈ 14λ). This setup resembles closely the forward part of the ATLAS experiment, where the beam approximates the momenta of particles typically produced in ‘minimum-bias collisions’ and where the iron absorber corresponds to the shielding in front of the muon spectrometer
Summary
The Large Hadron Collider (LHC) under construction at CERN is scheduled to be operational in 2006. At a luminosity of L = 1034 cm−2 s−1 the experiments will operate with collision rates at the 109 Hz level, producing > 1011 particles per second This very high rate of p–p collisions creates a level of background so high that it becomes a major design criterion for the LHC experiments. ATLAS, A T(oroidal) L(HC) A(pparatu)S [1], is characterized by two distinct magnetic-field systems: A superconducting solenoid will be installed around the inner-detector cavity and large superconducting air-core toroids consisting of independent coils will be arranged outside the calorimetry for the muon spectrometer. This concept offers almost no constraints on calorimetry and the inner detector while at the same time providing magnetic fields for a high-resolution, large-acceptance and robust muon spectrometer
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