  Experiments aimed at direct searches for WIMP dark matter require highly
effective reduction of backgrounds and control of any residual radioactive
contamination. In particular, neutrons interacting with atomic nuclei represent
an important class of backgrounds due to the expected similarity of a
WIMP-nucleon interaction, so that such experiments often feature a dedicated
neutron detector surrounding the active target volume. In the context of the
development of DarkSide-20k detector at INFN Gran Sasso National Laboratory
(LNGS), several R&D projects were conceived and developed for the creation of a
new hybrid material rich in both hydrogen and gadolinium nuclei to be employed
as an essential element of the neutron detector. Thanks to its very high
cross-section for neutron capture, gadolinium is one of the most widely used
elements in neutron detectors, while the hydrogen-rich material is instrumental
in efficiently moderating the neutrons. In this paper results from one of the
R&Ds are presented. In this effort the new hybrid material was obtained as a
poly(methyl methacrylate) (PMMA) matrix, loaded with gadolinium oxide in the
form of nanoparticles. We describe its realization, including all phases of
design, purification, construction, characterization, and determination of
mechanical properties of the new material.
