A study on the output charge from a TGC for 2.5 MeV and 14 MeV neutrons

Thin gap chambers (TGCs) will be used for triggering muons in the end-cap region of the ATLAS detector. A large amount of neutron background radiation is foreseen in the experimental area. This paper describes experimental results of the TGC response to neutrons as fundamental data. Neutrons with monochromatic energies of 2.5 MeV and 14 MeV were generated by d-D and d-T reactions, respectively. Output charge spectra of a TGC originated by these neutrons were measured. They show difference characteristics due to the original neutron energies. A qualitative explanation of the difference will be presented, where the ionization energy deposit in the gas volume is estimated with the GEANT4 simulation. The high voltage dependencies of the TGC outputs were also measured.