Micro-Inclusion Engineering via Sc Incompatibility for Luminescence and Photoconversion Control in Ce3+-Doped Tb3Al5-xScxO12 Garnet.

Aluminum garnets display exceptional adaptability in incorporating mismatching elements, thereby facilitating the synthesis of novel materials with tailored properties. This study explored Ce3+-doped Tb3Al5-xScxO12 crystals (where x ranges from 0.5 to 3.0), revealing a novel approach to control luminescence and photoconversion through atomic size mismatch engineering. Raman spectroscopy confirmed the coexistence of garnet and perovskite phases, with Sc substitution significantly influencing the garnet lattice and induced A1g mode softening up to Sc concentration x = 2.0. The Sc atoms controlled sub-eutectic inclusion formation, creating efficient light scattering centers and unveiling a compositional threshold for octahedral site saturation. This modulation enabled the control of energy transfer dynamics between Ce3+ and Tb3+ ions, enhancing luminescence and mitigating quenching. The Sc admixing process regulated luminous efficacy (LE), color rendering index (CRI), and correlated color temperature (CCT), with adjustments in CRI from 68 to 84 and CCT from 3545 K to 12,958 K. The Ce3+-doped Tb3Al5-xScxO12 crystal (where x = 2.0) achieved the highest LE of 114.6 lm/W and emitted light at a CCT of 4942 K, similar to daylight white. This approach enables the design and development of functional materials with tailored optical properties applicable to lighting technology, persistent phosphors, scintillators, and storage phosphors.

Scintillation of polyester fabric and clothing via proton irradiation and its utilization in surface imaging of proton pencil beams.

In the realm of radiation therapy, a conspicuous obstacle lies in the dearth of external observation concerning radiation beams aimed at the patient. While real-time monitoring of such beams on the patient's surface during therapy holds promise, the imaging of particle beams has thus far proven to be a formidable task. Here, we show our discovery of polyester fabrics and cloths as auspicious scintillating materials, ideally suited for the visualization of radiation beams upon the patient's surface. The light output of polyester fabrics ranged from 10 to 20% of that observed in plastic scintillators. When exposed to spot scanning proton beams, clear beam spots emerged on the surface of the polyester cloths. The movement of these scanning beams was effectively captured using a CMOS camera in a light-shield-free with lights-off environment. The resulting images provided a means for evaluating spills of the proton beams. The inherent flexibility of polyester fabrics and clothing enhances their appeal for applications in the intricate landscape of radiation therapy, promising a bright future for surface beam imaging endeavors.

Development of an event-by-event based Li-ZnS(Ag) neutron imaging detector with selective neutron detection capability.

High sensitivity and high resolution is desired in such technologies as neutron radiography. However, the contamination of gamma photons in neutron images decreases the accuracy of neutron radiography. To solve this problem, we developed an event-by-event based neutron imaging system that can selectively detect neutrons. The developed neutron imaging system consists of an Li-ZnS(Ag) scintillator plate optically coupled to a flat panel photomultiplier tube (FP-PMT) with a light guide. Scintillation light emitted from the Li-ZnS(Ag) by the interaction with neutron-induced particles is used to calculate the position based on the center of mass calculations. The spatial resolution of the neutron imaging detector is ∼2.3 mm FWHM, and the sensitivity for 252Cf at 2 cm from the source with 2-cm-thick polystyrene is 20 cps/MBq. Background count fraction from 60Co gamma photons was 0.2 %. For various types of neutron absorption phantoms, high-contrast and high-resolution neutron images are obtained with the developed neutron imaging detector using a252Cf neutron source.

A comparative study of EM-CCD and CMOS cameras for particle ion trajectory imaging.

High-resolution and real-time imaging of particle ion trajectories is essential in nuclear medicine and nuclear engineering. One potential method to achieve high-resolution real-time trajectory imaging of particle ions involves utilizing an imaging system that integrates a scintillator plate with a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera. However, acquiring an EM-CCD camera might prove challenging due to the discontinuation of CCD sensor manufacturing by vendors. As an alternative imaging approach, a low-noise, high-sensitivity camera utilizing a cooled complementary metal-oxide-semiconductor (CMOS) sensor offers a promising solution for imaging particle ion trajectories. Yet, it remains uncertain whether CMOS-based cameras can perform as effectively as CCD-based cameras in capturing particle ion trajectories. To address these concerns, we conducted a comparative analysis of the imaging performance between a CMOS-based system and an EM-CCD-based system for capturing alpha particle trajectories. The results revealed that both systems could image the trajectories of alpha particle, but the spatial resolution with the CMOS-based camera exceeded that of the EM-CCD-based camera, primarily due to the smaller pixel size of the sensor. While the signal-to-noise ratio (SNR) of the trajectory image from the CMOS-based camera initially lagged behind that from the EM-CCD-based camera, this disparity was mitigated by implementing binning techniques on the CMOS-based camera images. In conclusion, our findings suggest that a cooled CMOS camera could serve as a viable alternative for imaging particle ion trajectories.

Development of an ultrahigh resolution real time alpha particle imaging system for observing the trajectories of alpha particles in a scintillator.

High-resolution imaging of alpha particles is required in the detection of alpha radionuclides in cells or small organs for the development of radio-compounds for targeted alpha-particle therapy or other purposes. We developed an ultrahigh resolution, real time alpha-particle imaging system for observing the trajectories of alpha particles in a scintillator. The developed system is based on a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera, combined with a 100-µm-thick Ce-doped Gd3Al2Ga3O12 (GAGG) scintillator plate. Alpha particles from an Am-241 source were irradiated to the GAGG scintillator and imaged with the system. Using our system, we measured the trajectories of the alpha particles having different shapes in real time. In some of these measured trajectories, the line shapes of the alpha particles that flew in the GAGG scintillator were clearly observed. The lateral profiles of the alpha-particle trajectories were imaged with widths of ~ 2 µm. We conclude that the developed imaging system is promising for research on targeted alpha-particle therapy or other alpha particle detections that require high spatial resolution.

Temperature Characteristics of Resonance Frequency for Double-Layered Thickness-Shear Resonator.

The effect of the difference in the thickness ratio of the double-layered thickness-shear resonator on the temperature characteristics of the resonance frequency was investigated using a Ca3TaGa3Si2O14 (CTGS) single crystal. Three specimens with thickness ratios of x = 0.25 , 0.33, and 0.50 were prepared using 122° Y - and 171° Y -cut CTGS substrates. For the specimens with x = 0.25 and 0.33, the temperature characteristics varied depending on the order of the resonance mode. For the specimen with x = 0.50 , on the other hand, almost the same temperature characteristics were observed regardless of the order of the resonance mode. To interpret this phenomenon, a new equation for predicting the temperature characteristics of the fundamental mode (first mode) for the double-layered resonator was created using the electric flux density ratio generated in the two substrates. The expected values using this equation were in good agreement with the result of the first mode temperature characteristics.

Mid-infrared imaging through up-conversion luminescence in trivalent lanthanide ion-doped self-organizing optical fiber array crystal.

We propose a scheme for imaging mid-infrared (MIR) wavelengths via pre-excitation-assisted up-conversion luminescence in lanthanide ion (Ln3+)-doped Self-organizing Optical FIber Array (SOFIA) crystal. First, near-infrared pre-excitation wavelength excites an electron from the ground state to an excited state of Ln3+. Next, the MIR wavelength to be imaged promotes this excited electron to a higher-lying energy state. Finally, relaxation of the electron from the higher-lying energy state to the ground state emits the up-conversion luminescence in the visible region, completing the MIR-to-visible wavelength conversion. An analysis of the 4f to 4f intra-configurational energy level transitions in Ln3+, together with an appropriate selection of the pre-excitation wavelength and the visible luminescence constrained within the 500-700 nm wavelength range, reveals that trivalent erbium (Er3+), thulium (Tm3+), holmium (Ho3+), and neodymium (Nd3+) can be used to image MIR wavelengths. Our proposed scheme, called MIR imAging through up-Conversion LuminEscence in a SOFIA crystal, will enable the imaging of MIR wavelengths using low-cost optics and readily available silicon-based detectors in the visible spectral region and will open up new possibilities for MIR wavelength detection and imaging.