Effect of La doping on calcium tungstate (CaWO4) crystals radiation hardness

The induced absorption spectra were measured for equally grown CaWO4 and Ca WO4:La single crystals after Co-60 radioisotope irradiation by doses within 1 to 230 Gy. La doping increases considerably the radiation hardness of Ca WO4 material similarly as was observed for isostructural PbWO4 single cryst als recently. Transmission of as grown undoped CaWO4 shows a noticeable dec rease below 450 nm, which gives the evidence of deep trapping states. These trapping centres are effectively diminished by La doping as well. Induced absorption bands are discussed in the light of known and hypothesized color centers in CaWO4 and PbWO4 single crystals, which were reported earlier in the literature.