TECHNIQUES FOR PRODUCTION OF ORTHOSILICATE SCINTILLATORS

本发明的目的是开发用于高产量、低成本生产高性能掺铈氧正硅酸镥（LSO）结晶的新方法。其动机是LSO是近五十年来发现的最有前途的新闪烁体之一，具有x和伽马射线光谱学的重要特性的独特组合，即：相对于BGO的高密度，快速衰减和大的光产额。LSO似乎是PET系统中取代BGO的主要候选者。然而，LSO的实际应用受到与晶体生长（Czochralski方法）相关的困难的阻碍，这是由于所采用的高温。在第一阶段的工作中，我们成功地完成了一项可行性研究，该研究验证了使用新的低温晶体生长技术生产结晶LSO晶体的创新方法。光透明的多晶LSO样品的体积为几毫米3的生长和研究其材料特性，闪烁特性和响应γ射线。新晶体的性能与直拉法生长的高质量晶体进行了比较。在第二阶段，我们将优化生长技术并简化工艺，以获得特别适用于PET探测器环的大体积、高性能和低成本LSO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，以直接生产矩形晶体和具有当前PET仪器正确尺寸的晶体块。最后，我们将建立一条预生产线，并使用第一阶段建立的评估技术评估生长晶体的产量和质量。拟议的商业应用：迄今为止，LSO仍然没有商业可用。当可用时，它的使用将广泛应用于各种应用程序中，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用途。其中包括：PET;高能物理学;工业过程控制;环境监测;微物理学;空间仪器等，以及全新的固态光电探测器，如APD和新的漂移光电探测器的用途。

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.