The spin Hamiltonian parameters of Gd 3+ in a single crystal of Thorium disulfide (TI1S2) are analysed by means of the superposition model, in its most general form of a two exponents power law. In fact, the approximated one exponent power law is not suitable for this compound, where the ion-ligand distances show a quite large spread. The results of the analysis are then applied to the case of Gd 3+ doped Thorium oxysulfide (ThOS), where the fitting of the experimental data is possible only assuming some distortion of the ligand cage.

A new kind of UHV compatible microdisplacement actuator has been developed. It is based on a piezoelectric translator bakable up to 150 °C, encapsulated in a stainless-steel housing. A metal bellows allows the movement of the actuator and it gives a suitable preload to compensate the vacuum load. This new actuator has a very low outgassing rate due to the external stainless-steel surface of the casing and to the UHV electrical feedthrough. The mechanical characteristics (resolution, load capability, stiffness) are similar to those available with standard non-UHV compatible piezos. This new kind of microdisplacement actuator can be used in an UHV environment without any significant effect on the ultrahigh vacuum. The vacuum test and the accuracy test in UHV have been performed and will be thoroughly described.