We investigate, by experiments and numerical simulations, thermal activation processes of Josephson tunnel junctions in the presence of microwave radiation. When the applied signal resonates with the Josephson plasma frequency oscillations, the switching current may become multivalued in a temperature range far exceeding the classical to quantum crossover temperature. Plots of the switching currents traced as a function of the applied signal frequency show very good agreement with the functional forms expected from Josephson plasma frequency dependencies on the bias current. Throughout, numerical simulations of the corresponding thermally driven classical Josephson junction model show very good agreement with the experimental data.

A high sensitive nano superconducting quantum interference device (nanoSQUID) operating as a magnetic flux to critical current transducer with a suitable feedback circuit is employed to measure the magnetization of ferrimagnetic iron oxide nanoparticles. An improved SQUID responsivity has been obtained by using a loop inductance asymmetry. Iron oxide nanoparticles having a mean diameter of 8 nm have been excited by applying a polarizing field in the plane of the nanoSQUID loop. The field dependence of the nanoparticle magnetization at T = 4.2 K shows magnetic hysteresis. Magnetic relaxation measurements are reported and compared with those obtained by using a commercial measurement system.

We present an ultra high sensitive three-dimensional nano Superconducting QUantum Interference Device (nanoSQUID) fabricated by using the Focused Ion Beam sculpting technique. Based on a fully niobium technology, the nanodevice consists in a niobium superconducting loop (0.2 μm²) interrupted by two nanometric Nb/Al-AlOx/Nb Josephson junctions. The nanoSQUID exhibited an intrinsic magnetic flux noise as low as 0.65 μΦ₀/Hz^1/2 corresponding to a spin noise less than 10 Bohr magnetons per unit of bandwidth. It has been successfully employed in nanoparticle magnetic relaxation measurements. Due to its excellent performance, reliability, and robustness, we believe that the proposed nanoSQUID offers a crucial step toward a wide employment of nanoSQUIDs in the nanoscience.

A new Selective Solar Absorber, designed to improve the Sun-to-thermal conversion efficiency at mid temperatures in high vacuum flat thermal collectors, is presented. Efficiency has been evaluated by using analytical formulas and a numerical thermal model. Both results have been experimentally validated using a commercial absorber in a custom experimental set-up. The optimization procedure aimed at obtaining Selective Solar Absorber is presented and discussed in the case of a metal dielectric multilayer based on Cr₂O₃ and Ti. The importance of adopting a real spectral emissivity curve to estimate high thermal efficiency at high temperatures in a selective solar absorber is outlined. Optimized absorber multilayers can be 10% more efficient than the commercial alternative at 250 $°$C operating temperatures, reaching 400 $°$C stagnation temperature without Sun concentration confirming that high vacuum flat thermal collectors can give important contribution to the energy transition from fossil fuels to renewable energy for efficient heat production.