The Calliope plant, a pool-type irradiation facility located at the Research Centre ENEA-Casaccia (Rome), is
equipped with the 60Co γ source in a high-volume shielded cell. Calliope facility is involved in radiation processing
research on materials (polymers and optical components) and on devices to be used in hostile radiation environment
such as nuclear plants, aerospace experiments and High Energy Physics experiments. The aim of this work is to give
an overall picture of the activity we are carrying on at our laboratories with a mention to the possible applications in
the field of scintillators and glasses, like doping effect to induce radiation resistance in scintillators, glasses for safe
nuclear fuel disposal, suitable substitute oxides which can replace PbO in the preparation of lead-free glasses
complying environmental regulations.
Gamma radiation induced absorption processes of various scintillating materials were studied at room temperature.
Single crystal of PbWO4, Ce-doped YAlO3 and Ce(Pr)-doped Y(Lu)3Al5O12 were irradiated by 60Co and doses ranging
between 1-500 Gy. Broad induced absorption spectra obtained were decomposed into separate Gaussian components and
tentatively ascribed to specific color centres. Supporting thermoluminescence and electron paramagnetic resonance
experiments were performed to reveal the nature of charge carrier traps. The influence of codoping by aliovalent ions is
also shown and discussed.
Optical coatings are widely used in optical instrumentation for astronomical and space applications. The required optical components are similar to the ones necessary for ground-based instrumentation: antireflection coatings, mirrors, transmission filters. In addition, depending on the specific application, resistance to the radiation induced damage is needed. The analysis here is limited to optical components for instruments to be used for Earth observation from the polar sun-synchronous orbit, where they will withstand a total radiation dose of 50 Gy accumulated during a typical lifetime of 5 years. In this work a set of optical coating materials were submitted to γ irradiation at the 60Co radioisotope source (ENEA Research Center) in order to simulate the hostile radiation environment in which they will be employed. The selected coatings are made with a multilayer structure that contains oxide layers and/or metal layers. Before the coating irradiation, the behavior of single-layer materials was investigated by comparing their reflectance and transmittance before and after the γ-ray exposure. Results are reported for a number of oxide single layers (SiO2, HfO2, Y2O3), metal layers (Ag, Al) and multilayer coatings made with these materials, by the physical vapor deposition (PVD) technique. The behavior of different substrates (glass, quartz) is also compared.
A group of of heavy germanate glasses containing BaO and/or Gd2O3, La2O3, SnO and doped with the scintillating rare earth Tb3+ are presented. Photoluminescence measurements are made on these glasses. The intensity of emission peaks is found proportional to the contents of Tb3+ dopants as well as of Gd3+: the former indicates that no obvious concentration quenching effect is visualized within the limits of present Tb3+ dopant while the latter is related to the enhanced energy transfer process from Gd3+ to Tb3+ centers.