a) INFN – LNF, via E. Fermi n. 40, 00044 Frascati (Roma), Italy
b) CIEMAT, Av. Complutense 40, 28040 Madrid, Spain
c) Politecnico di Milano, Dipartimento di Energia, via La Masa 34, 20156 Milano, Italy
d) INFN – Milano, Via Celoria 16, 20133 Milano, Italy
e) INAIL – DPIA, Via di Fontana Candida n.1, 00040 Monteporzio Catone, Italy
A new directional neutron spectrometer called CYSP (CYlindrical SPectrometer) was developed within the NESCOFI@BTF (2011–2013) collaboration. The device, composed by seven active thermal neutron detectors located along the axis of a cylindrical moderator, was designed to simultaneously respond from the thermal domain up to hundreds of MeV neutrons. The new spectrometer condenses the performance of the Bonner Sphere Spectrometer in a single moderator; thus requiring only one exposure to determine the whole spectrum. The CYSP response matrix, determined with MCNP, has been experimentally evaluated with monochromatic reference neutron fields from 144 keV to 16.5 MeV, plus a 252Cf source, available at NPL (Teddington, UK). The results of the experiment confirmed the correctness of the response matrix within an overall uncertainty of ±2.5%. The new active spectrometer CYSP offers an innovative option for real-time monitoring of directional neutron fields as those produced in neutron beam-lines.