Nagarkar V V, Miller S R, Gelfandbein V, Shirwadkar U, Gaysinskiy V
Radiation Monitoring Devices (RMD) Inc., 44 Hunt Street, Watertown, MA 02472, USA.
Nucl Instrum Methods Phys Res A. 2011 Oct 1;652(1):271-274. doi: 10.1016/j.nima.2010.08.039. Epub 2010 Aug 31.
We are exploring a novel time- and cost-efficient approach to produce robust, large-volume polycrystalline lanthanide halide scintillators using a hot wall evaporation (HWE) technique. To date, we have fabricated LaBr:Ce and LaCl:Ce films (slabs) measuring up to 7 cm in diameter and 7+ mm in thickness (20 to 25 cm in volume) on quartz substrates. These polycrystalline scintillators exhibit very bright emissions approaching those exhibited by their melt-grown crystal counterparts. Scanning electron micrographs (SEMs) and X-ray diffraction analyses confirm polycrystalline growth with columnar structures, both of which help in light piping, thereby contributing to the observed high light yields. The new scintillators also exhibit good energy resolution for γ-rays over the tested range of 60 keV (Am) to 662 keV (Cs), although they have not yet reached that of the corresponding crystals. The measured response linearity over the same energy range is comparable for both our HWE synthesized films and melt-grown commercially-available reference crystals. Similar consistency in response is also observed in terms of their decay time and afterglow behaviors. The data collected so far demonstrate that our HWE technique permits the rapid creation of scintillators with desired structural and compositional characteristics, without the introduction of appreciable defects, and yields material performance equivalent to or approaching that of crystals. Consequently, the deposition parameters may be manipulated to tailor the physical and scintillation performance of the resulting structures, while achieving a cost per unit volume that is substantially lower than that of crystals. In turn, this promises to allow the use of these novel scintillation materials in such applications as SPECT, PET, room-temperature radioisotope identification and homeland security, where large volumes of materials in a wide variety of shapes and sizes are needed. This paper describes our growth and testing of polycrystalline LaBr:Ce scintillators and provides comparative characterizations of their performance with crystals.
我们正在探索一种新颖的、省时且经济高效的方法，利用热壁蒸发（HWE）技术来制备坚固的、大批量的多晶镧系卤化物闪烁体。到目前为止，我们已经在石英衬底上制备出了直径达7厘米、厚度达7毫米以上（体积为20至25立方厘米）的溴化镧铈（LaBr:Ce）和氯化镧铈（LaCl:Ce）薄膜（板）。这些多晶闪烁体发出的光非常明亮，接近其熔融生长的晶体对应物发出的光。扫描电子显微镜（SEM）图像和X射线衍射分析证实了具有柱状结构的多晶生长，这两者都有助于光导，从而导致观察到的高光产额。尽管新的闪烁体尚未达到相应晶体的能量分辨率，但在60 keV（镅）至662 keV（铯）的测试能量范围内，它们对γ射线也表现出良好的能量分辨率。在相同能量范围内，我们通过HWE合成的薄膜和熔融生长的市售参考晶体的测量响应线性相当。在它们的衰减时间和余辉行为方面也观察到了类似的响应一致性。到目前为止收集的数据表明，我们的HWE技术能够快速制造出具有所需结构和成分特征的闪烁体，而不会引入明显的缺陷，并且所产生材料的性能等同于或接近晶体的性能。因此，可以操纵沉积参数来调整所得结构的物理和闪烁性能，同时实现每单位体积成本远低于晶体。反过来，这有望使这些新型闪烁材料能够用于单光子发射计算机断层扫描（SPECT）、正电子发射断层扫描（PET）、室温放射性同位素识别和国土安全等应用，在这些应用中需要大量各种形状和尺寸的材料。本文描述了我们对多晶溴化镧铈闪烁体的生长和测试，并提供了它们与晶体性能的比较表征。
