Online program Overview Session: NSS-07

Abstract

High-melting-point oxide scintillators are key materials for radiation imaging and harsh-environment radiation detection, but their scaling is limited by iridium crucibles, melt contamination, and composition fluctuation. We report crucible-free growth and scaling of Ce:LYSO and Y₂O₃ scintillators using the oxide crystal growth from cold crucible (OCCC) method. In OCCC growth, the oxide melt is directly heated by high-frequency induction and retained by a self-formed solidified raw-material layer in a water-cooled copper basket. Ce:LYSO was grown in air, and EPMA showed host-cation segregation coefficients close to unity for Lu, Y, and Si. The straight-body region exhibited light-output variation within ±20%, with a maximum light output of approximately 16,000 photons/MeV under ¹³⁷Cs 662-keV excitation. Most importantly, an ultrahigh-melting-point Y₂O₃ scintillator was successfully grown to a 3-inch diameter by OCCC, and polished Y₂O₃ samples exhibited transparent appearance and a clear scintillation response under ¹³⁷Cs excitation. The OCCC method is a promising platform for scaling high-melting-point oxide scintillators without precious-metal crucibles.

Abstract

Cs₃Cu₂I₅ single crystals were grown at room temperature via a solvent evaporation method using two organic acid additives: oleic acid (OA) and formic acid (FA), and their effects on crystal quality and scintillation performance were systematically investigated. X-ray photoelectron spectroscopy confirmed the absence of Cu²⁺ features in both samples, demonstrating that organic acid additives effectively suppress Cu⁺ oxidation during growth. Single-crystal X-ray diffraction and rocking curve analysis revealed that formic-acid-assisted crystals exhibit superior crystalline quality, with a narrower rocking-curve FWHM of 0.009° compared to 0.016° for OA-assisted crystals. Scintillation measurements using a ¹³⁷Cs γ-ray source (662 keV) coupled to a SiPM photosensor showed an improved energy resolution of 5.4% for formic-acid-grown crystals versus 5.8% for OA-grown crystals. The enhanced performance of FA-assisted crystals is attributed to formic acid's ability to regulate iodide ion availability through slow reaction with I^3- species, reducing the crystallization rate and extending the metastable growth regime, thereby suppressing defect formation. In contrast, the long-chain nature of oleic acid promotes residual ligand incorporation and non-uniform solvent evaporation, slightly degrading optical transparency and crystallinity

Abstract

Tl-doped cesium copper iodide (Cs₃Cu₂I₅:Tl, CCI:Tl) has emerged as a promising scintillator for medical imaging, offering higher light yield than the long-established CsI:Tl while remaining non-hygroscopic and lead free.  Its emission (445–500 nm) matches the quantum efficiency of CCD, CMOS, and flat panel readouts, making it an excellent choice as a converter for advanced X-ray detectors. Detectors based on CCI:Tl have potential for providing dose efficiency in medical applications including digital mammography, radiography, and cone-beam CT. The high brightness of CCI:Tl will enable their use in high framerate or otherwise light starved applications in both medical and industrial fields.

We report on the development of polycrystalline CCI:Tl scintillating films grown by hot wall evaporation (HWE), a technique previously used to produce columnar, low stress CsI:Tl films and extended here to the ternary CCI system.  CCI crystals were first grown and then used as the source for evaporation.  Material quality was characterized by SEM and EDX.  EDX confirms stoichiometric Cs:Cu:I ratio of 3:2:5. Scintillation properties were measured under gamma and X-ray excitation, including pulse-height spectra, emission, light yield relative to CsI:Tl, scintillation decay time, and afterglow.  X-ray imaging performance was evaluated through quantification of contrast transfer function (CTF(f)) and measurements of modulation transfer function (MTF(f)) using a slit method. with films demonstrating resolution 5 lp/mm at 70 kVp for thickness in excess of 150µm.  The results indicate structured growth and demonstrate that HWE grown CCI:Tl films offer a viable, potentially higher luminosity alternative to CsI:Tl for indirect medical‑imaging detection while also revealing the deposition parameters that govern film morphology and scintillation response.  Results from both crystals and films and applications of CCI:Tl films will be presented.

Abstract

Two-dimensional (2D) metal halide perovskites have emerged as promising scintillator materials for radiation detection due to their high x-ray and gamma-ray absorption coefficients, high light yields, and fast scintillation decay times. Their structural flexibility enables precise tuning of optical and scintillation properties through variation of the organic spacer, halide composition, and dopant incorporation [1]. This work presents the synthesis, optical characterisation, and pellet fabrication of several 2D perovskite scintillators, including the Ruddlesden-Popper (RP) phase materials (BA)₂PbBr₄ and (PEA)₂PbBr₄, and the Dion-Jacobson (DJ) phase material (TMPDA)PbBr₄. Crystals were synthesised using a slow-cooling solution growth method and subsequently processed into pellets using a cold-pressing technique to increase thickness while improving uniformity and reproducibility. The effects of manganese and rubidium doping in (BA)₂PbBr₄ were also investigated, demonstrating enhanced light yield and tuneable emission behaviour. Under x-ray excitation, (PEA)₂PbBr₄ exhibited a light yield exceeding that of LYSO, while all investigated materials demonstrated promising gamma-ray scintillation responses with resolvable peaks. These results highlight the strong potential of 2D perovskite scintillators for next-generation radiation detection technologies.

Abstract

Cs₂ZnCl₄ single crystals exhibit ultrafast cross-luminescence and show great potential for high-repetition-rate and fast timing radiation detection areas. However, their light output is severely limited by synthesis-induced impurities and intrinsic defects. To address this bottleneck, this work systematically investigates two parallel strategies: hydrothermal purification and Cd doping.  High optical-quality single crystals were grown via the vertical Bridgman method using hydrothermally purified method, followed by systematic optical transmittance, luminescence, and absolute light output characterizations. The results demonstrate that hydrothermal purification effectively eliminates heavy metal impurities in the precursors, significantly enhancing the light output (LO) from 680 ph/MeV to 1078 ph/MeV (a 58.5% increase) while fully preserving the crystal's ultrafast decay constant of 1.76 ns. Furthermore, Cd doping increases the light output to 3689 ph/MeV, representing an enhancement of 126.6%. This study provides two effective strategies for enhancing the light output of ultrafast halide light-emitting materials.

Abstract

Lithium-rich scintillators are widely used to detect thermal neutrons, with Eu-doped lithium iodide (LiI:Eu) serving as the long-standing benchmark. LiI:Eu, however, has high gamma sensitivity, slow scintillation decay, and limited ability to distinguish neutrons from gamma rays. As a result, we have shifted our focus towards the lighter binary lithium halides, such as lithium chloride (LiCl) and lithium bromide (LiBr), which offer intrinsically lower gamma sensitivity.  We also investigated Ce³⁺ and Pr³⁺ with the goal of evaluating their ability for fast d-f type emission and neutron-gamma discrimination.

Single crystals were grown by the vertical Bridgman method and characterized by X-ray luminescence, light yield, decay time, and neutron response using a moderated Am/Be source. Initial results show that LiBr:Ce delivers a clear thermal-neutron peak at 3.1 MeVee with a light yield of 7,300 ph/n (comparable to GS20) and pulse-shape discrimination capability. Full data and comparison across all dopant-host combinations will be presented.

Abstract

ZnSe(Al,O) is a promising scintillator for compact beta spectroscopy, but its detector-relevant properties are poorly documented and strongly dependent on dopant composition, growth quality, and optical transport. This work experimentally characterises a commercially supplied ZnSe(Al,O) crystal intended for use in a silicon photomultiplier-coupled beta detector for strontium-90 monitoring. The crystal measured 42 mm in diameter and 2.1 mm in thickness. Scanning electron microscopy with energy-dispersive X-ray spectroscopy confirmed a zinc selenide composition with aluminium and oxygen impurities, giving measured atomic abundances of 49.2% zinc, 46.1% selenium, 3.50% oxygen, and 1.2% aluminium. The measured density was 5.31 g cm^−3, and the refractive index determined using a Brewster-angle method was 2.475. Scintillation waveforms were recorded under strontium-90/yttrium-90 beta irradiation using silicon photomultiplier readout and analysed to extract charge spectra and decay behaviour. The light yield was estimated to be approximately 7.8 × 10$^4$ photons MeV^−1, while the decay constant was measured as 9.41 us, with a waveform-to-waveform standard deviation of 1.1 us. These values are broadly consistent with the range reported for zinc-selenide-based scintillators, while providing a single experimentally derived parameter set for this specific ZnSe(Al,O) sample. The results support the suitability of ZnSe(Al,O) for silicon photomultiplier-based beta spectroscopy and provide material inputs required for improved detector modelling, optical design, and future development of compact detectors for environmental strontium-90 monitoring.

Abstract

Efficient detection of fast ultraviolet scintillation is essential for the next generation of high-speed radiation detectors. We investigate CsPbX₃ nanocrystals as a versatile wavelength-shifting platform, leveraging their sub-nanosecond response times and tunable bandgaps to match the peak sensitivity of standard photodetectors. As a proof-of-concept, using radioluminescence measurements, we characterize the conversion of scintillation light from a LYSO:Ce reference crystal by CsPbBr₃ nanocrystal layers and polymer-based nanocomposites. It has been observed that concentrated drop-cast layers perform better than nanocomposites and achieve total extinction of the broad scintillation peak of LYSO:Ce at 430 nm, shifting it to 535 nm, corresponding to the nanocrystal emission. Rigorous validation tests confirm that the observed green emission is a product of wavelength-shifting rather than a result of direct nanocrystal excitation or spectral attenuation of the primary light. This performance establishes a foundation for modular wavelength-shifting interfaces that can be tailored to various scintillators and radiators, including BaF₂ (cross-luminescence), CeF₃, and PbF₂ (Cherenkov light).