The improved scintillation crystal lead tungstate scintillation for PET

As a valuable material for the detecting of γ-ray, PbWO 4 and BaF 2 :PbWO 4 crystals were grown by a novel multi-crucible temperature gradient system developed by ourselves. Utilizing a topical partial heating method, this system can form a topical partial high temperature in its hearth. Thus this system could melt raw materials in step by step as requirement. The advantage of this method is that there would be solid obstruct left on the melt in the procedure of the crystal growing up. The left obstruct could prevent the volatilization of the component in the melt. Hence it is helpful for the composition homogenization in the crystal. The system also offers a sustaining device for multi-crucibles and thus it can grow many crystals simultaneity. The optical properties and scintillation properties of the crystals were studied. The results reveal that the ions doping improves the scintillation properties of the crystal. The transmittance spectra show that the transmittance of BaF 2 :PbWO 4 crystals are better than that of PbWO 4 crystals. For the PbWO 4 crystals, their absorption edge is at 325nm, and their maximum transmittance is 68%. For the BaF 2 :PbWO 4 crystals, their absorption edge is at 325nm and their maximum transmittance is upto76%. The X-ray excited luminescence spectra shows that the luminescence peak is at 420nm for the samples of PbWO 4 crystal while the peak is at 430nm for the samples of BaF 2 :PbWO 4 crystal respectively. The luminescence intensity of the samples of BaF 2 :PbWO 4 crystal is about two times than that of PbWO4 crystal. And their peak shape is different for the two kind of crystal. The light yield of BaF 2 :PbWO 4 crystals is about 2.9 times than that of PbWO 4 crystal Analyzing these scintillation properties, we find that the V Pb 3+ and V O- defects do harm for the optical properties of the crystal. Ions doping method could reduce the defect concentration and improving its illumination performance of the crystal. Specially, the doped F - ions in O 2- site can induce the aberrance of the [WO4] 2- tetrahedron and form [WO 3 F] - tetrahedron which has more active blue light yield, thus improve the light yield of the crystal. The improved light yield of BaF 2 :PbWO 4 crystals is valuable for the medical diagnosing instrument PET and CT with high resolving power