Neutron/γ discrimination by an emission-based phoswich approach

Development and Evaluation of a Dual-Layer-Offset PET Detector Constructed with Different Reflectors

Dual-layer-offset or multi-layer-offset design of a PET detector can improve spatial resolution while maintaining high sensitivity. In this study, three dual-layer-offset LYSO detectors with three different reflectors (ESR, Toray, and BaSO4) were developed. The top layer consisted of a 17 × 17 array of crystals 1 × 1 × 6.5 mm3 in size and the bottom layer consisted of an 18 × 18 array of crystals 1 × 1 × 9.5 mm3 in size. Neither light guides nor optical glue were used between the two layers of crystals. A custom-designed electronics system, composed of a 6 × 6 SiPM array, two FPC cables, and a custom-designed data processing module, was used to read out signals. An optimized interaction-decoding algorithm using the center of gravity to determine the position and threshold of analog signals for timing methods was applied to generate decoding flood histograms. The detector performances, in terms of peak to valley ratio of the flood histograms and energy resolutions, were calculated and compared. The dual-layer-offset PET detector constructed with BaSO4 reflectors performed much better than the other two reflectors in both crystal identification and energy resolution. The average peak-to-valley ratio and the energy resolution were approximately 7 and 11%, respectively. In addition, the crystals in the bottom layer showed better performance at crystal identification than those in the top layer. This study can act as a reference providing guidance in choosing scintillator reflectors for multi-layer dedicated DOI detectors designed for small-animal PET imaging.

Phoswich Detectors in Sensing Applications

Herein, we review studies of the integration of Phoswich detectors with readout integrated circuits and the associated performance in a radiological sensing application. The basic concept and knowledge of interactions with scintillation materials and the mechanisms and characteristics of radiological detection are extensively discussed. Additionally, we summarize integrated multiple detection systems and Phoswich detectors in radiological measurements for their device performance. Moreover, we further exhibit recent progress and perspective in the future of Phoswich-based radiological detection and measurement. Finally, we provide perspectives to evaluate the detector performance for radiological detection and measurement. We expect this review can pave the way to understanding the recent status and future challenges for Phoswich detectors for radiological detection and measurement.

Time-resolved luminescence and excitation spectroscopy of Co-doped Gd3Ga3Al2O12 scintillating crystals

Cerium doped Gd₃Ga₃Al₂O₁₂ (GGAG) single crystals as well as GGAG:Ce single crystals co-doped by divalent (Mg²⁺, Ca²⁺) and tetravalent (Zr⁴⁺, Ti⁴⁺) ions have been studied by means of time-resolved luminescence as well as the excitation luminescence spectroscopy in vacuum ultraviolet (VUV) and soft X-ray (XUV) spectral range. Tunable laser excitation was applied for time-resolved experiments in order to obtain luminescence decay curves under excitations in Ce³⁺, Gd³⁺ and excitonic absorption bands. The influence of the co-dopant ions on the Ce³⁺ luminescence decay kinetics is elucidated. The fastest luminescence decay was observed for the Mg²⁺ co-doped crystals under any excitation below bandgap energy indicating the perturbation of the 5d states of Ce³⁺ by Mg²⁺ ions. Synchrotron radiation was utilized for the luminescence excitation in the energy range from 4.5 to 800 eV. Special attention was paid to the analysis of Ce³⁺ excitation spectra in VUV and XUV spectral range where multiplication of electronic excitation (MEE) processes occur. Our results demonstrated that GGAG:Ce single crystals co-doped by Mg²⁺ ions as well as the GGAG:Ce crystal annealed in vacuum reveal the most efficient excitation of Ce³⁺ emission in VUV-XUV excitation range. The role of intrinsic defects in MEE processes in the co-doped as well as in the annealed GGAG:Ce single crystals is discussed.