Microscopy for Biomedicine

The research of the group is focused on electron microscopy of biomedical samples imaged at high vacuum, thus required a specific sample preparation. A technique for quantitative imaging of thin samples using detection of transmitted scatterd electrons is introducing, that allows imaging of the structure of investigated objects at high resolution and simultaneous measurement of their local mass-thickness and mass, respectively. The team is concerned with the investigation of new scintillation materials based on single crystals of dioxides and with their use in detection systems of signal electrons, particularly in scanning electron microscopes. Special attention is paid to the computer simulation of interaction mechanisms between electrons and a solid, to light propagation in light guides, and electron propagation in electrostatic and magnetic fields. Simulation results are compared with the experiment directed at the design of systems for the detection of backscattered and secondary electrons. The team is concentrated on the development of methods of detection of electrons that are difficult to be detected, such as low energy backscattered electrons. Different modes of information obtained by means of electrons with different take-off angles and energies propagated in different media are studied. The basic methodological conception is connected with the detection systems that ensure attainment of a high resolution image of the studied specimen, enable separation of different types of detected electrons and cathodoluminescent light, record different contrast mechanisms, and make use of the variety of the physical properties of signal electrons in scanning or transmission electron microscopy. The team is concentrated on the study of electron interaction in solids, cathodoluminescence, and on the research of noise effects. The team activity includes the Monte Carlo simulation of interaction processes and related optical effects. The results are used for the construction of detection systems and/or screens for electron microscopes. The essence of the current project is the investigation of properties of single crystal imaging screens (cerium activated single crystals of yttrium aluminium garnet YAG:Ce), and their exploitation in transmission electron microscopy. The project is motivated by the effort to put into practice new imaging components with relatively small dimensions and a high spatial resolution that will enable gaining of high quality digital images of objects investigated in the transmission electron microscope. The goal of the project is to experimentally determine the spatial resolution and the detection efficiency of a single crystal cathodoluminescence screen in the dependence on its thickness. The results of the measurement are compared with the values predicted by the theory and obtained by a computer simulation. The results are used for the design and construction of an imaging unit of the transmission electron microscope.