Development of the ACSpect neutron spectrometer: Technological advance and response against an accelerator-based neutron beam

Advances in neutron-based radiation therapies such as Boron Neutron Capture Therapy (BNCT) pushes towards the development of new neutron spectrometers, whose key features are to be their practicability, reliability, energy resolution and detection range. The ACSpect is a novel neutron spectrometer based on a two-stages monolithic silicon telescope detector coupled to an organic scintillator working as an active neutron converter.This paper reports the latest developments of the ACSpect and the results of the measurements of an accelerator-based neutron beam moderated by AlF3. The AlF3 is a moderator material optimised to obtain an epithermal neutron beam for accelerator-based BNCT of deep seated tumours. The experiments carried out are the first neutron spectrometry of a neutron beam moderated by AlF3.The performances of the ACSpect have been compared against Monte Carlo simulations, literature data and the gold-standard neutron spectrometer DIAMON. While the agreement between experiments and simulations allowed to validate the Monte Carlo model used to simulate the new moderator material, the agreement between literature data, ACSpect and DIAMON results confirmed the ACSpect as a compact and relatively easy-to-use high-resolution neutron spectrometer, capable of reliably operating in the energy range 250 keV - 4 MeV.