A new hybrid gadolinium nanoparticles-loaded polymeric material for neutron detection in rare event searches

Experiments aimed at direct searches for WIMP dark matterrequire highly effective reduction of backgrounds and control of anyresidual radioactive contamination. In particular, neutronsinteracting with atomic nuclei represent an important class ofbackgrounds due to the expected similarity of a WIMP-nucleoninteraction, so that such experiments often feature a dedicatedneutron detector surrounding the active target volume. In thecontext of the development of DarkSide-20k detector at INFN GranSasso National Laboratory (LNGS), several R&D projects wereconceived and developed for the creation of a new hybrid materialrich in both hydrogen and gadolinium nuclei to be employed as anessential element of the neutron detector. Thanks to its very highcross-section for neutron capture, gadolinium is one of the mostwidely used elements in neutron detectors, while the hydrogen-richmaterial is instrumental in efficiently moderating the neutrons. Inthis paper results from one of the R&Ds are presented. In thiseffort the new hybrid material was obtained as a poly(methylmethacrylate) (PMMA) matrix, loaded with gadolinium oxide in theform of nanoparticles. We describe its realization, including allphases of design, purification, construction, characterization, anddetermination of mechanical properties of the new material.

Journal of Instrumentation, 19, P09021 (2024)