High-Performance Transparent Optical Ceramic Scintillators through Nanotechnology

描述（申请人提供）：LSO是公认的PET理想闪烁体。它具有511 keV伽马射线的高阻挡能力，高产光率超过20000光子/MeV，快速衰减32ns。实现了高重合时间分辨率和能量分辨率。但是，LSO单晶的生长困难且昂贵，可重复性差，并且该材料根本无法用于一般商业用途。为了克服这些缺点，我们在之前的工作中开发了一种半透明的LSO光学陶瓷，它显示出与单晶相当的闪烁性能，但更容易制造并且可以以更低的成本填补可用性空白。但由于LSO具有光学各向异性，传统的陶瓷技术无法使其完全透明。然而，最近，一种通过纳米技术开发的新工艺能够在陶瓷甚至光学各向异性材料中实现几乎完全透明。这项技术涉及到纳米粉末在一定条件下的固化，将最终颗粒尺寸限制在可见光波长以下，从而防止几乎所有的散射，并使材料完全透明。该方法已在具有类似各向异性的多晶氧化铝实验中得到完全证实，并正在开发用于光学窗口的应用。本提案的目的是将两种已经开发的技术结合起来，以生产完全透明的光学陶瓷形式的LSO，其闪烁性能可与单晶相媲美。在第一阶段，我们将确认已经建立的氧化铝工艺也适用于LSO。我们将建立技术来制造必要的纳米颗粒粉末，并确定固化条件，在此条件下可以实现所需的材料特性。

DESCRIPTION (provided by applicant): LSO is generally recognized as the ideal scintillator for PET. It has high stopping power for 511 keV gamma rays, high light yield of over 20000 photons/MeV, and rapid decay of 32 ns. It achieves high coincidence timing resolution and energy resolution. But single crystals of LSO are difficult and expensive to grow, reproducibility is poor, and the material is simply not available for general commercial use. To overcome these drawbacks, we have in our previous work developed a translucent LSO optical ceramic, which displays scintillation performance comparable to that of the single crystal, yet is easier to fabricate and could fill the availability gap at lower cost. But because LSO is optically anisotropic, it cannot be made fully transparent by conventional ceramic technology. Recently, however, a new process has been developed through nanotechnology that is capable of achieving virtually full transparency in ceramics of even optically anisotropic materials. The technique involves the consolidation of nanopowders under conditions that limit the ultimate grain sizes to below the wavelengths of visible light, thereby preventing virtually all scattering and rendering the material fully transparent. The procedure has been completely confirmed in experiments on polycrystalline alumina, which is similarly anisotropic, and is being developed for optical window applications. It is the aim of this proposal to combine the two already developed technologies so as to produce LSO in the form of a fully transparent optical ceramic, which displays scintillation performance comparable to that of a single crystal. In Phase I we will confirm that the process that has already been established for alumina is adaptable to LSO as well. We will establish techniques to fabricate the necessary nanoparticulate powders and to define the consolidation conditions under which the desired material properties can be achieved.