Chansun Park

With the growing complexity of modern radiotherapy, the demand for dosimeters capable of delivering real-time, high-resolution, and reliable measurements has grown significantly. Although cadmium–zinc–tellurite (CZT) detectors have emerged as potential solutions to this growing demand, the lack of comprehensive characterization data for these detectors deters their application in clinical electron-beam dosimetry, especially for high-precision tasks such as small-field and point-dose dosimetry. In this study, we systematically characterized CZT detectors, emphasizing the performance trade-offs associated with detector thickness for therapeutic electron-beam dosimetry. The performance of two CZT detectors (6 × 6 mm²), with thicknesses of 5 and 8 mm, was evaluated using a clinical linear accelerator (LINAC) over an electron energy range of 6–18 MeV. Both detectors demonstrated stable baseline performance, including proportional dose linearity (R² > 0.997), dose-rate independence, and excellent long-term stability (<1.3% variation over two months). Furthermore, a distinct thickness-dependent trade-off was identified: while both configurations exhibited highly comparable dose responses at the 6-MeV baseline, the 8-mm detector exhibited better energy capture efficiency for higher-energy electrons. By contrast, the 5‑mm detector offered enhanced angular isotropy with respect to the gantry angle as well as reduced signal variation (±3.5% vs. ± 6.4%), emerging as more suitable for rotational therapies and geometrically demanding scenarios. Additionally, a nonmonotonic energy dependence was observed, characterized by a pronounced response peak at 15 MeV, which was likely attributable to bremsstrahlung photon contamination from the LINAC head. These findings demonstrate that detector thickness serves as an application-specific optimization factor for sensitivity and angular fidelity, offering a practical framework for deploying CZT detectors in both initial clinical evaluations and challenging extra-clinical radiation environments.

This study aims to establish evaluation criteria for selecting suitable scintillators by investigating how inorganic scintillators respond to particle radiation, particularly electron beams. We conducted a radiation tolerance study of inorganic scintillators irradiated with a 6 MeV electron beam, examining factors such as beam energy, radiation dose, crystallinity, and operating environment. The energy spectral performance revealed a dose‐dependent decrease in the relative light outputs and energy resolutions of Lu₃Al₅O₁₂:Pr (LuAG:Pr) and Gd₂Si₂O₇:Ce (GPS:Ce) when irradiated with a ¹³⁷Cs radioactive source, indicating a reduced radiation detection efficiency. After exposure to a 3 kGy dose of electron beam, the relative light outputs of these scintillators reduced to 66.2% and 56.9%, respectively. In contrast, Lu_2−xY_xSiO₅:Pr and Gd₃Al₂Ga₃O₁₂:Ce maintained their spectral performances after electron beam irradiation. Changes in the surface microstructure due to surface defects and the formation of color centers in bulk sites, induced by electron beam irradiation, hinder scintillation light detection and transmission, highlighting the importance of defect mitigation strategies and selection of suitable scintillators for radiation detection systems. Transmittance measurements of LuAG:Pr and GPS:Ce demonstrated that with increasing radiation dose, their optical performances and photoluminescence intensities decreased, indicating the impact of defects on light collection efficiency. In addition, their reduced thermoluminescence intensity confirmed that the irradiated electron beam‐induced changes in the defect density within the scintillators. These results suggest that scintillators for medical and aerospace applications should be selected based on their operating environmental conditions. Further studies on defect behavior and its effect on scintillation properties will guide the advancement of radiation detection technology.

This paper introduces the characteristics and efficiency of post-treatment methods for enhancing the timing resolution of ceramic Ce:GAGG scintillators. The thermal annealing and surface treatments were included to analyze their impact on time-resolved photoluminescence (TRPL) and thermoluminescence (TL) characteristics. Optical properties were improved by suppressing nonradiative recombination due to the reduced surface defects, while heat-treatment removes traps as confirmed by TL measurements. TRPL decay characteristics revealed that samples treated with mechanical polishing followed by heat treatment exhibited the best scintillation performance, with a slow component of 272.3 ns. These findings will aid in developing techniques for improving the luminescence of other inorganic scintillators.

We compared thermal stability, open-circuit voltage, short-circuit current, and fill factor values of single-crystal Cadmium telluride (CdTe) grown using the vertical Bridgman (VB) technique and doped with group V elements (phosphorus and arsenic), and group Ⅰ element (sodium), followed by an annealing process. The sodium-doped CdTe maintained a hole density of 10¹⁶ cm⁻³ or higher; after annealing for a long time, this decreased to 10¹⁵ cm⁻³ or less. The arsenic-doped CdTe maintained a hole density of approximately 10¹⁶ cm⁻³ even after the annealing process; however its bulk minority carrier lifetime decreased by approximately 10%. The phosphorus-doped CdTe maintained its properties after the annealing process, ultimately achieving a hole density of ~10¹⁶ cm⁻³ and a minority carrier lifetime of ~40 ns. The characteristics of a single-crystal solar cell were evaluated using a solar cell device that contained single-crystal CdTe with various dopants. The sodium-doped sample exhibited poor interfacial properties, and its performance decreased rapidly during annealing. The samples doped with group V elements exhibited stable characteristics even during long-term annealing. We concluded, therefore, that group V elements dopants are more suitable for CdTe single-crystal-based solar cell applications involving thermal stress conditions, such as space missions or extreme fabrication temperature environments.

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In the past, the main research and use of scintillators in extreme environments were mainly limited to high energy physics and the well-logging industry, but their applications are now expanding to reactor monitoring systems, marine and space exploration, nuclear fusion, radiation therapy, etc. In this article, we review and summarize single-crystal inorganic scintillator candidates that can be applied to radiation detection in extreme environments. Crucial scintillation properties to consider for use in extreme environments are temperature dependence and radiation resistance, along with scintillators’ susceptibility to moisture and mechanical shock. Therefore, we report on performance change, with a focus on radiation resistance and temperature dependence, and the availability of inorganic scintillator for extreme environments—high radiation, temperature, humidity and vibration—according to their applications. In addition, theoretical explanations for temperature dependence and radiation resistance are also provided.

We propose an integrated front-end data acquisition circuit for a hybrid ultrasound (US)-gamma probe. The proposed circuit consists of three main parts: (1) a preamplifier for the gamma probe, (2) a preprocessing analog circuit for the US, and (3) a digitally controlled analog switch. By exploiting the long idle time of the US system, an analog switch can be used to acquire data of both systems using a single output channel simultaneously. On the nuclear medicine (NM) gamma probe side, energy resolutions of 18.4% and 17.5% were acquired with the standalone system and with the proposed switching circuit, respectively, when irradiated with a Co-57 radiation source. Similarly, signal-to-noise ratios of 14.89 and 13.12 dB were achieved when US echo signals were acquired with the standalone system and with the proposed switching circuit, respectively. Lastly, a combined US-gamma probe was used to scan a glass target and a sealed radiation source placed in a water tank. The results confirmed that, by using a hybrid US-gamma probe system, it is possible to distinguish between the two objects and acquire structural information (ultrasound) alongside molecular information (gamma radiation source).

Surface modification of ceramic Ce-doped Gd₃Al₂Ga₃O₁₂ (Ce:GAGG) was performed by exposing small samples to anhydrous phosphoric acid (H₃PO₄) under different conditions (temperature and duration) to investigate the effects of chemical polishing treatment. When coupled to a photomultiplier tube (PMT) and used as a radiation detector, chemical treatment for 3 min at 190 °C improved the light (signal) output by 24.8% and energy resolution by 2.5% (percentage point), respectively. This can be attributed to a reduction in surface roughness that enhanced optical properties. Thus, chemical polishing could be a low-cost alternative to mechanical polishing especially for small or complex shaped ceramic scintillators.