Ph.d. degree
Institut Laue Langevin (France) and University of Perugia (Italy), 2014

Francesco Piscitelli

Supervisor: Francesco Sacchetti

Boron-10 layers, Neutron Reflectometry and Thermal Neutron Gaseous Detectors

Keywords:

• Gaseous detectors
• Wire chambers (MWPC, Thin-gap chambers, drift chambers, drift tubes, proportional chambers etc)
• Neutron detectors (cold, thermal, fast neutrons)
• Neutron diffraction detectors

Abstract:

Nowadays neutron facilities are going toward higher fluxes, e.g. the European Spallation Source (ESS) in Lund (Sweden), and this translates into a higher demand in the instrument performances. Because of its favorable properties,He-3 has been the main actor in thermal neutron detection for years. Starting in about 2001 the He-3 stockpile has been declining. The world is now experiencing the shortage of He-3. This makes the construction of large area detectors (several squared meters) not realistic anymore. A way to reduce the He-3 demand for those applications is to move users to alternative technologies, such as Boron-10. Although it is absolutely necessary to replace He-3 for large area applications, this is not the main issue for what concerns small area detectors for which the research is focused on improving their performances. Some technologies appear promising, though implementation would likely present technical challenges. There are several aspects that must be investigated in order to validate those new technologies; e.g. detection efficiency and gamma-ray sensitivity. Several detectors, based on Boron-10 layers, have been conceived, built and tested. We have laid a solid theoretical basis, confirmed by experiments, for the understanding of the main aspects of solid converter layers employed in neutron detectors. We also explored practically, by the construction and characterization of prototypes, a specific type of solid-converter-based neutron detector, the Multi-Blade, especially suited for application in neutron reflectometry.