Design and experimental validation of a compact spectrometer for epithermal neutrons

A novel neutron compact spectrometer with an isotropic response called Neutron Capture Therapy Activation Compact Spectrometer is presented (**). The device is sensitive from thermal up to 100 keV neutrons, and it is designed for working in a single irradiation exposure. The detector geometry is composed by a spherical moderator shell containing different material foils exhibiting neutron radiative capture resonances covering the epithermal energy domain. The simulation results on the geometry optimization and on the elements choice will be presented. Irradiation and activation measurements on a first prototype have been performed at a calibrated epithermal neutron source in Torino. The unfolded neutron spectrum was compared with those obtained using a Bonner Sphere Spectrometer, showing an agreement within few %. This serves as a proof of concept. ACS is a promising device for neutron applications, such as Boron Neutron Capture Therapy, where an epithermal neutron beam or field is involved. Due to the compact dimensions, it could also be utilized for in-phantom measurements.