SCINTILLATION PROPERTIES OF BaF2:Cd, BaF2, BaF2:Ce, BaF2:Sc, BaF2:Tm CRYSTALS AND CERAMICS; NEW PHOTOSENSORS FOR THE VACUUM ULTRAVIOLET REGION

Research and development of new scintillation materials is mainly triggered by the growing needs of modern medical imaging, high energy and nuclear physics. Pure BaF2 crystals are widely applied as scintillation material because of its high density, high radiation resistance and good time resolution due to the fast component (< 1 ns) appearing in the emission bands around 220 and 195 nm. This fast component luminescence is called Auger-free luminescence or crossluminescence, and it is attributed to the radiative recombination of the F-2p valence band electrons with the outmost holes of the Ba-5p core band. However, in addition to the fast component, the BaF2 crystal has a slow component at 300 nm with a decay time of about 700 ns, which causes deterioration of the time resolution at high counting rates. Suppression of the slow component is a crucial key when applying this crystal to high counting rate experiments in such fields as high energy physics and nuclear medicine. This work is aimed to develop specimens of BaF2-based crystals and ceramics doped with different elements in order to improve the light yield of the fast component and to suppress the slow part of the luminescence.