Progress Towards Bonner Sphere Spectrometry of the INFN-LNL SPES-BNCT

The Legnaro National Laboratories (LNL) of the Italian National Institute of Nuclear Physics (INFN) are developing a neutron source within the SPES-BNCT project. An accelerator-based, high-flux thermal neutron beam facility is planned for the experimental treatment of skin melanoma. Neutrons are produced via the Be(p,n) reaction by bombarding a 1 mm thick beryllium target with 5 MeV protons generated by the CN Van de Graaff accelerator of the INFN-LNL. One of the major challenges of Boron Neutron Capture Therapy (BNCT) is to obtain the required characterization of the neutron beam in terms of intensity and energy spectrum. Data from the literature are limited when it comes to the angular neutron yield of the Be(p,n) reactions and the corresponding energy spectra [1]. While various types of spectrometers are currently being used at INFN-LNL for measurements in the 100 keV 5 MeV neutron energy regions [3,4], spectra should also be characterized below 100 keV. For this purpose a Bonner Sphere Spectrometer (BSS) was developed at the Department of Mechanical, Nuclear and Production Engineering (DIMNP) of the University of Pisa. The present report concentrates on the setup of the BSS. An evaluation of the response matrix of the BSS was carried out by using the MCNPX code [4]. An appropriate unfolding code is necessary to achieve the final spectrum, various deconvolution options are being examined.