Investigation of the ATLAS MDT chambers response to fast neutron background radiation

We have studied the response of an array of ATLAS muon spectrometer drift tubes exposed to a neutron radiation produced by the d(d,n)t reaction at the 5.5 MV TANDEM Van de Graaff accelerator of the National Centre of Scientific Research "Demokritos" in Greece. The setup consisted of 24 drift tubes operating with a gas mixture of Ar:CO₂ (93:7%) at 3 atm absolute pressure. The operating anode wire voltage was 3080 V. The neutron energy varied between 6 and 11 MeV and the neutron flux was adjusted in order to match the expected background neutron flux in the ATLAS hall. In this framework, we present the data analysis with emphasis to the possible mechanisms following the neutron exposure, such as the effect of prompt gamma rays due to the neutron elastic and inelastic scattering in the aluminum drift tube wall, the elastic and inelastic recoils of the gas nuclei, and the emission of gamma rays after activation of the aluminum drift tube wall.