Research activity



The scientific activity of the PAS Group covers the implementation of the various PAS methods and the widespread application of them in the fields of physics, chemistry and materials science based on the group’s decade-long experiences. The application of the phenomenon of positron trapping for the examination of structural imperfections in metallic and non-metallic solid samples (materials with crystalline structure, amorphous metallic glasses and semiconductors) is an actual task. These studies are related to the research of structural imperfections-created by heavy ion irradiation, a topic studied in strong co-operation with the other groups of the Department employing nuclear analytical methods.
The study of the formation of electron-positron bound system, the positronium (Ps) and the detection of the annihilation of the long-living orthopositronium (o-Ps) opens our research toward to the interdisciplinary frontiers of chemistry and physics. This direction has lead us to study the process of the positronium trapping which allows us to understand the native and induced extended free volume sites of polymers, ion crystalline grains with large specific surface and zeolites with high porosity. The goal of our current research is to establish the correlation between the orthopositronium trapping and the features of internal surfaces, the near-surface imperfection structure examination in thin films and sandwich samples, the detection of interlinked open volumes in membranes and polyethylene samples, the exploitation of Ps-creation using thin porous films (which is going to be applied by the CERN in antigravitational experiments, too).
One of the boundary conditions for achieving success in research is the involvement in developing the methodical techniques: this activity existed in our PAS laboratories since the beginning of the positron studies. We could improve the experimental performance of the measurements significantly by the elaboration of statistical utility-governed performance optimization aspects of the event-counting-based nuclear techniques (e.g. symmetric double-gating employed in PAS lifetime spectroscopy, the registration of expanded/full energy range in Doppler-spectroscopy, the inclusion of 3γ-annihilation events into the data acquisition of PAS lifetime spectroscopy) which has improved the international reputation of the group as well. Besides the conventional facilities of the lifetime and Doppler-spectroscopy the home-based development of a slow positron generator designed for the depth-selective study of imperfection structures has been started successfully. The routine-like application of the slow positron beam needs stronger financial support which may be attained by project applications.
The experimental experience of the PAS groups is also promising with respect to applications of positron emission tomography, PET, establishing national and international relations is in progress.