Nuclear Instruments and Methods in Physics Research A 506 (2003) 101–109 Resistive plate chamber neutron and gamma sensitivity measurement with a 252 Cf source M. Abbrescia a , S. Altieri b , V. Baratti b , O. Barnab " a b , G. Belli b , G. Bruno b , A. Colaleo a , C. DeVecchi b , R. Guida b, *, G. Iaselli a , E. Imbres b , F. Loddo a , M. Maggi a , B. Marangelli a , G. Musitelli b , R. Nard " o b , S. Natali a , S. Nuzzo a , G. Pugliese a , A. Ranieri a , S. Ratti b , C. Riccardi b , F. Romano a , P. Torre b , A. Vicini b , P. Vitulo b , F. Volpe a a Dipartimento Interateneo di Fisica, Universit " a di Bari and INFN sezione di Bari, via Amendola 173, I-70126 Bari, Italy b Dipartimento di Fisica Nucleare e Teorica, Universit " a di Pavia and INFN sezione di Pavia, via Bassi 6, I-27100 Pavia, Italy Received 6 June 2002; received in revised form 4 March 2003; accepted 4 March 2003 Abstract A bakelite double gap Resistive Plate Chamber (RPC), operating in avalanche mode, has been exposed to the radiation emitted from a 252 Cf source to measure its neutron and gamma sensitivity. One of the two gaps underwent the traditional electrodes surface coating with linseed oil. RPC signals were triggered by fission events detected using BaF 2 scintillators. A Monte Carlo code, inside the GEANT 3.21 framework with MICAP interface, has been used to identify the gamma and neutron contributions to the total number of collected RPC signals. A neutron sensitivity of (0.6370.02)  10 3 (average energy 2 MeV) and a gamma sensitivity of (14.070.5)  10 3 (average energy 1.5 MeV) have been measured in double gap mode. Measurements done in single gap mode have shown that both neutron and gamma sensitivity are independent of the oiling treatment. r 2003 Elsevier Science B.V. All rights reserved. Keywords: Resistive Plate Chamber; Gamma sensitivity; Neutron sensitivity; Compact Muon Solenoid 1. Introduction Bakelite Resistive Plate Chambers (RPCs) have been chosen as part of the muon subdetector for the Compact Muon Soleniod (CMS) experiment at the Large Hadron Collider (LHC). RPCs, as well as each detector in the CMS experiment, will work in a hostile environment rich of neutron and gamma rays. In order to evaluate the effect of this back- ground radiation on the detector functionality, it is necessary to know the RPC efficiency, called sensitivity, to this kind of radiations. Neutron background, in an energy range between 20 meV (thermal neutrons) and 1 GeV, is produced from the hadronic interactions in the calorimeter and from the interactions of the primary proton beam with the beam pipe and/or the beam collimators. ARTICLE IN PRESS *Corresponding author. Tel: +39-0382-507268; fax: +39- 0382-526938. E-mail address: roberto.guida@pv.infn.it (R. Guida). 0168-9002/03/$-see front matter r 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-9002(03)01378-0