Terahertz tomography for testing wrapped scintillating crystals

Terahertz time-domain spectroscopy (THz-TDS) is demonstrated to be effective in novel application, for 3D characterization of wrapped scintillator crystals in search for defects affecting the light-yield of these crystals. This is of special importance for fast scintillators currently in demand to be exploited in high-energy physics experiments and medical imaging devices. Typical inorganic (GAGG:Ce) and organic (BC-408) scintillators wrapped in polytetrafluoroethylene (PTFE) and enhanced specular reflector (ESR) tapes have been studied. Time-of-flight information extracted from THz-TDS data reveals positions of the interfaces between the materials, wrapping thickness variations, and allows for the wrapping inspection with resolution better than a single layer, typically ∼200 μm-thick, of PTFE, the currently most common wrapping material. The results are supported by the study of the properties of the wrapping materials in the THz range and evidence of the prospectiveness of THz-TDS technique as a novel tool for nondestructive inspection of wrapped scintillators. •New application of terahertz imaging for inspecting wrapped scintillator crystals•Thickness variations are revealed with resolution better than one wrapping layer•Diffusive and enhanced specular reflector tapes are transparent in terahertz range