Journal of the Korean Physical Society最新文献

Utilizing an anti-reflection coating on the lens surface to enhance the coupling efficiency, we employ the ABCD matrix formalism to derive analytical expressions for the coupling efficiency (CE) between a laser diode (LD) and both single-mode circular core dispersion managed fiber, i.e., dispersion-shifted fiber (DSF) and single-mode dispersion-flattened fiber (DFF), facilitated by an anti-reflection coated hyperbolic microlens (ARCHL) at the fiber tip. This coating is pivotal for maximizing efficiency. Although no prior theoretical work has utilized an anti-reflection coating on the lens surface to enhance coupling efficiency, it is essential to acknowledge its potential importance. By reducing reflections at the lens surface, such a coating can minimize loss and increase the overall efficiency of the coupling process. We assume that the distribution for both the source and the fiber follows a Gaussian field characterized by a single parameter, and ensuring maximum CE necessitates matching the transmitted spot size of the lens with that of the fiber. To address the non-Gaussian nature of the fiber’s field, we utilize the Petermann II spot size, enhancing the realism of our estimations. Investigations span two wavelengths, 1.3 μm and 1.5 μm. Here, we show the effects of anti-reflection coating on coupling optics by comparing the coupling efficiencies for the two cases with and without using the anti-reflection coating on the lens surface. Our straightforward method accurately predicts coupling optics performance with minimal computational effort. This simple, yet precise technique stands to greatly benefit system designers in the optical technology field.

Beamline 6C Bio Medical Imaging at the Pohang Light Source-II is a station for synchrotron X-ray radiograph and micro-computed tomography. The beam emitted from a multipole wiggler is trimmed, attenuated, and made monochromatic before illuminating an object. The projection image is recorded using a detection scheme that converts the X-ray image into a visible light image, which is then magnified and captured by an optical microscope. For image conversion, a single-crystal (garnet) scintillation screen is used. Here, we assess the image quality in terms of noise characteristics and spatial resolutions. Two types of scintillation screens (LuAG:Ce and GAGG:Ce) with two different thicknesses (50 μm and 100 μm) are compared. Although GAGG:Ce featured a better signal-to-noise ratio thanks to its two times higher light yield, contrast-transfer function (CTF) analysis in the spatial frequency domain suggests that the spatial resolutions of each scintillator were more or less identical. A scientific CMOS (complementary metal-oxide semiconductor) camera at the beamline was seen to accumulate electronic noise for longer exposures. In addition, because each scintillator has similar resolution characteristics according to CTF results, the resolution according to the various sample-to-detector distances (i.e., SDD or magnification or ({R}_{2})) in a particular LuAG:Ce scintillator was measured, and the optimal ({R}_{2}) was observed to be 50 mm.

Optical spectroscopy is a non-destructive and non-contact method used to explore the physical properties of solids over a wide range of energy, and it is particularly suitable for studying two-dimensional van der Waals magnetic materials due to its ability to probe magnetic order and electronic transitions simultaneously. We have investigated the optical properties of the layered antiferromagnet NiGa₂S₄ over a wide range of frequencies from the near-infrared region to the visible region, obtaining valuable insights into the electronic structure of NiGa₂S₄. NiGa₂S₄ is an insulator with a triangular antiferromagnetic spin configuration (S = 1) and is known as a spin-nematic material. We identified a (d-d) transition and an absorption edge in the near-infrared and visible regions and studied their temperature dependence. In particular, we observed that the temperature dependence of the (d-d) transition exhibits a distinct change in its trend at the spin-nematic phase transition temperature. These findings suggest key insights into the electronic transitions and magnetic properties of NiGa₂S₄. Our optical spectroscopic investigation of NiGa₂S₄ enhances our understanding of its complex electronic structure, contributing to the broader field of condensed matter physics and materials science.

Microwave cavities used in axion haloscope experiments typically employ a tuning rod as a means to widen the range of resonance frequencies at which it is sensitive to axion-to-photon conversion. A realistic tuning mechanism requires a gap between the cavity end caps and the tuning rod to ensure movement, and causes some modes to hybridize with the resonant mode that is being tracked for the experiment. These so-called mode mixings lead to gaps in the frequency range that practically lose sensitivity to axions. To solve this problem, we present a cavity design which, for two tuning rod configurations corresponding to a lower and higher frequency range, have a dielectric rod inserted at a specific location that makes the cavity asymmetrical. Moving the tuning rod closer to the dielectric insert changes the location and frequency of the mode mixing compared to when it is farther away from it. This design is easily realizable in practical experiments and makes possible an axion dark matter search with minimal loss in sensitivity due to mode mixings. We also show that the same design has the same desired effect when cavity dimensions are scaled down to be smaller and are at higher resonance frequencies.

Liquid scintillators are widely used in nuclear, particle, and medical physics, as well as in other radiation-related applications. Traditional liquid scintillators typically consist of organic solvents and fluors. In this study, a new acetone-based liquid scintillator was synthesized by dissolving 2,5-diphenyloxazole (fluor) in acetone, replacing conventional oil-based solvents. A new acetone-based scintillation solution mixed with a contrast agent was prepared to enhance X-ray attenuation properties. The performance of this new formulation was evaluated by measuring Hounsfield unit values using computed tomography. Specifically, Hounsfield unit values for several scintillator samples were obtained from computed tomography images and compared with those of traditional scintillator solutions. Our new liquid scintillation formulation with a contrast agent concentration of 50% or higher achieves Hounsfield unit values exceeding 2500. This formulation enables the detection of radiation exposure via its fluorescent properties, enhancing radiation safety monitoring, while also providing a liquid shielding effect. To date, no prior research or results have reported on this specific combination of acetone, fluor, and contrast agent. These findings suggest that new acetone-based scintillation solution mixed with a contrast agent has potential applications in dosimetry, radiation shielding, and imaging analysis.

The relativistic effect on the fundamental properties of the dust-acoustic waves (DAWs) is investigated in a collisionless, unmagnetized, anisotropic, self-gravitating, dusty plasma containing electron-depleted nonextensive ions and inertially warmed, positively and negatively charged dust grains. For this purpose, a Korteweg–de Vries (KdV) as well as a forced KdV (FKdV) equation are derived employing the well-known reductive perturbation method. The structures of single-, double-, and triple-solitons are studied due to the impact of concerned parameters. The effects of external periodic force and angular frequency on the structure of KdV-soliton are also examined. The phase velocity of the DAWs decreases with the rising values of the entropy index and the relativistic streaming factor, whereas it increases with the growing values of the mass ratio of the negative to positive dust grains and the gravitational parameter. The amplitude of the DAWs decreases with the increasing effects of the entropic index and the dust pressure. When the entropic index and gravitational parameter values are small, the amplitude decreases by a significant amount. The impacts of the relevant factors on the structure of the hump-shaped compressive and dip-shaped rarefactive single-, double-, and triple-KdV-solitons, as well as FKdV-solitons, are significant. The entropic index is crucial to the structure of the KdV- and FKdV-solitons.

The  4th generation storage ring (4GSR) facility is under construction in Korea. The facility includes a 200-MeV Linac, a booster ring operating from 200 MeV to 4 GeV, and a storage ring. Storage ring circumference is 799.297 m, stored electron energy and current are 4 GeV and 400 mA, respectively. Both storage ring and booster ring are located in the same tunnel. Shielding assessment was performed using the FLUKA 4(-)4.0 Monte Carlo code to determine the required thickness and shielding structure of the Linac and storage ring tunnels. Various beam loss scenarios under normal and abnormal operations were considered for the shielding analysis. The injection efficiency from booster ring into storage ring was assumed as 90%. For the shielding calculations, it was assumed that 4 mA beam current is injected into the storage ring every 2 min. The electron beam injection from Linac to booster ring, beam extraction from booster ring, and injection from booster ring to storage ring are all located near each other. Thus, the shielding calculations were categorized for the injection area and non-injection area so that for each area different tunnel wall thicknesses were considered. The shielding criteria were based on the Nuclear Safety Act in Korea and the As Low As Reasonably Achievable (ALARA) principle. These simulations will provide an overall radiological framework for shielding the 4GSR in Korea based on the present design conditions.

The impact of position resolution on the sensitivity of short-baseline reactor neutrino experiments searching for light sterile neutrinos is investigated. Detailed simulations are conducted to evaluate two detector configurations: a segmented detector and an opaque liquid scintillator (OLS) detector, each positioned at two candidate research reactor sites, HANARO and Kijang. For both detector types, pseudo-data are generated under realistic assumptions regarding neutrino flux, detector response, and background levels. Oscillation analyses are performed to estimate detector sensitivity, incorporating both statistical and systematic uncertainties. The results indicate that the OLS detector, owing to its superior position resolution, achieves leading sensitivity across a wide range of oscillation parameters, even under conservative experimental conditions. These findings underscore the potential of OLS technology as a highly effective approach for future sterile neutrino searches.

Intracranial aneurysms (IAs) pose a significant risk of rupture, necessitating accurate hemodynamic assessment for effective clinical decision-making. This study explores the feasibility of using physics-informed neural networks (PINNs) to predict blood flow velocity, pressure distribution, and wall shear stress (WSS) in a simplified 3D sidewall saccular aneurysm model, without relying on conventional computational fluid dynamics (CFD) simulations. A PINN was developed to approximate velocity and pressure fields by enforcing the Navier–Stokes equations for steady-state conditions and boundary conditions within a computational domain. The model was trained using a collocation-based approach with 20,000 domain points and 2000 boundary points. A fully connected neural network with nine hidden layers was implemented, and training was conducted using the Adam optimizer with a learning rate of 0.001. Velocity, flow vectors, pressure, and WSS were predicted from both 3D geometry and 2D profile. Results demonstrated that the PINN model effectively captured physiologically relevant hemodynamic patterns, including velocity reduction within the aneurysm sac and elevated WSS at the aneurysm neck. Performance metrics showed an MSE of 5.57 for velocity and 3.32 for pressure, with an R-squared value of 0.66 and 0.60, respectively. This study presents an initial demonstration of PINNs as a CFD-free modeling framework for hemodynamic analysis in idealized aneurysm geometries. While not benchmarked against CFD, the results underscore the potential of PINNs for future patient-specific, image-based modeling pipelines, offering a physics-informed approach for cerebrovascular risk assessment and treatment planning.