TECHNIQUES FOR PRODUCTION OF ORTHOSILICATE SCINTILLATORS

这项提议的目标是开发高产量、低成本生产高性能掺Ce氧硅酸吕(LSO)闪烁晶体的新方法。其动机是LSO是近50年来发现的最有希望的新闪烁体之一，具有X和伽马射线光谱的重要特性的独特组合，即：高密度、快速衰减和相对于BGO的大光产额。在聚酯体系中，LSO似乎是取代BGO的主要候选者。然而，LSO的实际应用受到与晶体生长(提拉法)有关的困难的阻碍，因为使用的温度很高。在第一阶段的工作中，我们成功地完成了一项可行性研究，该研究验证了使用一种新的低温晶体生长技术来生产闪烁LSO晶体的创新方法。生长了体积为几mm~3的轻质透明多晶LSO样品，并研究了它们的材料特性、闪烁特性和对伽马射线的响应。新晶体的性能可与提拉法生长的高质量晶体相媲美。在第二阶段，我们将优化生长技术和简化工艺，以获得专门适用于PET探测器环的大体积、高性能和低成本的LSO闪烁晶体。为了实现这一目标，我们还将开发和实施新的铸造技术，以直接生产具有当前PET仪器正确尺寸的矩形晶体和晶体块。最后，我们将建立一条预产线，并使用在第一阶段建立的评估技术来评估生长的晶体的产量和质量。建议的商业应用：到目前为止，LSO仍未商业化。一旦可用，它将在许多应用程序中广泛使用，从而立即提高性能，或者在需要快速计时或高计数率的情况下实现全新的使用。这些领域包括：正电子对撞机；高能物理；工业过程控制；环境监测；地球物理；空间仪器等；以及固体光电探测器的全新用途，如雪崩光电探测器和新型漂移光电探测器。

The goal of this proposal is to develop novel methods for high-yield, low- cost production of high performance cerium-doped lutetium oxyorthosilicate (LSO) scintillating crystals. The motivation is that LSO is amongst the most promising new scintillators discovered in almost five decades, with a unique combination of important properties for x and gamma-ray spectroscopy, namely: high density, fast decay, and large light yield relative to BGO. LSO seems to be a prime candidate to replace BGO in PET systems. However, the practical utilization of LSO is hindered by difficulties related to crystal growth (Czochralski method) due to the high temperatures employed. During the Phase I effort we successfully concluded a feasibility study which validated the innovative approach using a new low-temperature crystal growth technology to produce scintillating LSO crystals. Light transparent polycrystalline LSO samples of a few mm3 in volume were grown and investigated for their material properties, scintillation properties and response to gamma-rays. The properties of the new crystals compared well with high-quality crystals grown by the Czochralski method. In Phase II we will optimize the growth technique and streamline the process to obtain large volume, high performance and low cost LSO scintillating crystals specifically suited for PET detector rings. Towards this goal we will also develop and implement novel casting techniques to directly produce rectangular crystals and blocks of crystals with the correct dimensions for current PET instruments. Finally we will set-up a preproduction line and evaluate yields and quality of the grown crystals using evaluation techniques established in Phase I. PROPOSED COMMERCIAL APPLICATIONS: To date LSO is still not commercially available. When available its use will be widespread in hosts of applications leading to immediate performance gains, or enabling completely new uses where fast-timing or high counting-rate is needed. These include: PET; high-energy physics; industrial process control; environmental monitoring; geophysics; and space instrumentation etc., as well as brand new uses with solid-state photodetectors such as APD's and new drift photodetectors.