Neutron spectrometry with He-3 proportional counters

Helium filled proportional counters are widely used in the field of neutron detection and spectrometry. A review of some parameters and physical effects that influence the He-3 proportional counters response is presented through the experimental study of a commercially available counter. The impact of these effects is taken into account in the description of detector performance when the response is calculated with the Monte Carlo method. A method to determine neutron energy distribution with a bare He-3 counter in an unknown neutron field is presented. The neutron energy range extends up to about 7 MeV. The method does not require a hypothesis about neutron spectrum shape. It is based in the calculated counter response with Geant4, the validity of which is experimentally verified. A detailed description of the steps needed is presented.