Innovative approaches to advanced X-ray detection with layered garnet optical ceramics

The efficient detection of ionizing radiation is crucial in various tools developed for X-ray-based security, particle identification, and medical diagnostics. Intensive research is underway to enhance the performance of current detectors, focusing on improving sensitivity, and timing response. In the well-known garnet single crystal family, new complex compositions are emerging, with Gd3(Ga,Al)5O12 (GGAG) recently gaining attention due to its high light yield of over 104 photons/MeV and short scintillation lifetime of a few tens of ns when doped with Cerium. Nevertheless, the challenges associated with producing bulk crystals have prompted a search for alternative and more manageable materials. In this context, advancements in sintering techniques for transforming crystalline micro-grains into bulk ceramics with high optical quality have enabled optical ceramics to become highly competitive compared to single crystals. This is due to the relative ease of production, the ability to uniformly incorporate high concentrations of activators, and the versatility of shaping that allows for complex geometries in a single piece without requiring mechanical post-processing or bonding. Our recent research efforts have resulted in the development of fully densified Ce:GGAG optical ceramics through reaction sintering using commercial oxide powders [1]. We optimized the synthesis process to eliminate porosity and achieve good optical quality by employing a combined approach involving pressureless sintering in air followed by hot isostatic pressing, along with the use of sintering aids. Furthermore, directional sensitivity is a crucial requirement for detectors used in locating orphan nuclear sources. To address this, we also explore unconventional geometries by combining two layers of different garnets (Ce:GGAG and Pr:YAG), revealing a scintillation response strongly influenced by the material architecture, extending the potential of layered optical ceramics for energy- and direction-sensitive X-ray detectors [2].