Positron annihilation lifetime spectroscopy (PALS) is an established method for characterization and quantification of point defects in bulk solids. The method demonstrates a sub-nano scale resolution, that spans from a single atom vacancy to voids (vacancy clusters), and bubbles (defects filled with gas), with high sensitivity.

The basic concept behind PALS is that vacant point defects in the lattice act essentially as potential wells that trap positrons. The electron density inside them is lower than in the undamaged bulk region. Thus, positron lifetimes inside the defects are longer and depend upon their size.

The measured lifetime spectrum consists of contributions from annihilation events in the sample under study and its point defects, as well as undesired contributions from the sample housing and source support foils. Since the time resolution of PALS systems is usually of the same order as the mean positron lifetime in bulk of materials, it is crucial to have time resolution as high as possible.

In this talk we will present a novel experimental system that enables a time resolution of 140ps, in comparison to a typical resolution of about 240ps. We will present a unique offline analysis method that chooses annihilation events by applying optimized criteria to the data and creates positron lifetime spectra. We will describe the trapping model that allows extraction of mean positron lifetime values and their relative intensities in the lifetime spectrum. Finally, we will discuss the significance contribution of Geant4 Monte-Carlo simulations to the determination of spatial annihilation intensities in the source and sample housing.