氟离子掺杂钨酸铅闪烁晶体的发光特性

钨酸铅(PWO)晶体是一种综合性能非常优异的无机闪烁晶体,并且在高能物理研究领域已获得重要应用,但光输出偏低的缺点严重制约了它在非高能物理领域的应用.本文采用氟化铅作为掺杂剂,用Bridgman方法生长出了光输出比普通PWO晶体高出2—3倍的新型PWO晶体.紫外和X射线荧光光谱的测试结果表明,这种新型晶体的发光波长比纯PWO晶体红移了大约134 nm,即为553 nm,衰减时间也从几十纳秒延长到100 ns以上,且光输出随积分时间的增加而增强.此外,发射波长和光输出沿晶体生长方向存在明显的位置依赖性,初期

Luminescence characteristics of lead tungstate(PbWO4)scintillation crystal doped with fluorine anions

Lead tungstate (PbWO₄, shorten as PWO) crystal has attracted much interest as a very dense, fast and radiation hard scintillator. However, its application is strongly hampered by its poor light output. At present, great efforts have been devoted to improve the scintillating efficiency of PWO crystals. In this paper, fluorine anions were used as dopant to improve the light output of PWO crystals. The crystals were grown by modified Bridgman method. The charge was obtained from PbO and WO₃ powder with purity of 99.99% and 99.999% respectively. The transmittance spectra measured with a spectrophotometer Shimadzu UV-2501PC reveal that the transmission of PWO:F is much higher than that of undoped PWO, especially in the short wavelength region (330—500 nm). The most significant characteristic of the F-doped PWO is that two emission components can be identified in their photoluminescence spectra, a fast component related to the blue emission (419 nm) and a slow component related to the green emission (553 nm). The measured light yield of PWO:F, based on the pulse height spectra stimulated by ¹³⁷Cs, is as high as 2 to 3 times of the undoped PWO and meanwhile will be increased with the integration of time gate. This means that the significant contribution to the light yield of PWO may come from the green luminescence. The decay constants excited by ²²Na gamma ray can be fitted into three components, they are τ₁=2.68[57.5%] , τ₂=47.6[31.0%] and τ₃=183[11.5%]. 88.5% of total scintillating light decays within 50 ns. However, the distribution of light yield along the crystal axis is not uniform, i.e. higher at the tail end than that in the seed end. It is suggested that the blue emission is ascribed to the regular lattice centers, namely [WO₄]^2- and the green one to a defect [WO₃+F] cluster. The significant defects in PWO lattice induced by F-anion should be responsible for the increase of the light yield.