Linac-based thermal neutron source construction and characterization

Within the INFN ELIBANS project, an intense thermal neutron source has been designed and set up at the University of Torino. It is based on an electron medical linac coupled to a photoconverter structure based on (gamma, n) reaction in a lead target. The photoconverter materials and geometry have been optimized in order to have a pure and intense thermal neutron field in an irradiation cavity. This paper describes the results of the first benchmark experiments concerning the linearity of the thermal fluence rate with the linac current, the spatial uniformity of thermal neutron field and its highly thermal energetic spectrum. The achievements concerning different active neutrons diagnostics able to measure intense thermal neutron fluence rates are also reported.