We report on the development of a high-sensitivity Gallium Nitride (GaN)-based X-ray detector, specifically engineered for low-energy X-ray applications targeting energies below 25 keV. This study introduces two types of diode-based detector structures, pn-type and pin-type, fabricated on high-mobility n-type GaN substrates. Our experimental results demonstrate that both detector types exhibit favorable characteristics, with enhanced output counts proportional to the X-ray dose, thereby confirming their efficacy for medical imaging purposes. A comparative analysis of the pn-type and pin-type detectors revealed a preference for the pintype configuration due to its superior performance metrics, establishing it as the basic design for further development. This preference is largely attributed to the structure of the pin-type detector which features a thick depletion layer, essential for the effective operation of X-ray detectors. The required thickness for this layer ranges from 100 to $1000 \mu \mathrm{m}$, significantly greater than the several micrometers necessary for visible light photodiodes. This thickness is crucial to ensure stable, recombination-free carrier transport across the detector, which is vital for maintaining high charge collection efficiency. Notably, the intrinsic layer (i-layer) of the pin-type detector contains fewer defects compared to the p-layer, further contributing to its higher charge collection efficiency. The advancements highlighted in this research are promising for the enhancement of low-energy X-ray applications, potentially leading to significant improvements in medical imaging technology. This work lays the foundation for future studies and development of GaN-based detectors, steering the field towards more sophisticated and efficient X-ray imaging solutions.

In the high-temperature gas-cooled reactors (HTGR), new neutron detectors are expected to be developed because the in-core temperature is over $600{ }^{\circ} \mathrm{C} . \mathrm{BGaN}$, a wide bandgap semiconductor operating in harsh environments, is expected to be a new neutron detection semiconductor. In previous studies, a high-temperature tolerance of BGaN detectors is $300^{\circ} \mathrm{C}$. In this study, we fabricated detectors with different BGaN film thicknesses and investigated their effect on high-temperature tolerance through neutron irradiation and high-temperature tolerance experiments. BGaN films are grown by MOCVD with BGaN thicknesses of 1 and $5 \mu \mathrm{m}$. Neutron detectors were fabricated using BGaN films, and $\alpha$-particles detection measurements were performed at high-temperatures. Neutron irradiation measurements were carried out at UTR-KINKI and at KUR. The crystallinity of BGaN was degraded with increasing film thickness by XRC measurements. The detection characteristics of $\alpha$-particles at high-temperature were evaluated using each BGaN detector. In case of the $5-\mu \mathrm{m}-\mathrm{GaN}$ detector, its high-temperature tolerance was $600{ }^{\circ} \mathrm{C}$. In case of the $5-\mu \mathrm{m}-\mathrm{BGaN}$ detector, the noise signals were increased at $300^{\circ} \mathrm{C}$, and it was difficult to discriminate between the detection and noise signals. On the other hand, in the $1-\mu \mathrm{m}-\mathrm{BGaN}$ detector, increasing in the noise signals is suppressed at $400^{\circ} \mathrm{C}$. These results indicate that the improvement of crystallinity has reduced defects and improved tolerance to thermal noise.

A technique has been developed for determining the linear tension of steps with one-ion and two-ion heights that form growth/evaporation spirals on NaCl(100). This technique is based on the interpretation of experimentally obtained nonlinear dependences of the steady-state distance between spiral’s turns in relation to the inverse undersaturation by numerical simulation performed using the analytical solution of the Barton, Cabrera, and Frank diffusion problem, taking into account the step kinetic coefficient and the back stress effect. The linear tension value of steps with one-ion height is found to be less than half the linear tension value of steps with two-ion height. This suggests that the studied vicinal surfaces are thermodynamically stable. The proposed technique can also be applied to other alkali halide crystals.

In neutron imaging, the development of neutron detectors with high spatial resolution is expected. BGaN neutron semiconductor detectors have been proposed as new neutron imaging sensors. BGaN includes ${ }^{10} \mathrm{~B}$ elements with large neutron capture cross-section as constituent atoms and has low $\gamma$-ray sensitivity because of a constituent atom with a relatively small atomic number. In previous research, a neutron detection pulse signal was observed, but an energy spectrum could not be obtained. In this study, the influence of film thickness on neutron detection in BGaN devices was evaluated by simulation and experiment. The neutron detection energy spectrum for each film thickness was calculated by PHITS. In BGaN film thickness of over $1 \mu \mathrm{m}$, the dominant peak energy was 2.3 MeV. This result indicates that $1 \mu \mathrm{m}-\mathrm{BGaN}$ may have sufficient energy discrimination properties in neutron detection. Then, we fabricated BGaN detectors with film thicknesses of $1,3,5$, and $10 \mu \mathrm{m}$. The $1 \mu \mathrm{m}-\mathrm{BGaN}$ has the best crystallinity, and decrease in crystallinity was observed with increasing BGaN film thickness. On the other hand, the sensitive layer region becomes thicker as the BGaN layer becomes thicker, which is expected to improve the neutron capture sensitivity. In the neutron irradiation experiment results at UTR-KINKI, the neutron detection sensitivity was contributed by crystallinity rather than B content. Furthermore, neutron capture energy spectra of 5 and $10 \mu \mathrm{m}-\mathrm{BGaN}$ devices were obtained by irradiation experiments using long wavelength neutrons at MINE-1 in JRR-3. FWHM of energy peak by neutron capture was decreased with increasing BGaN thickness. The result suggests that some of the generated charged particles escaped outside the BGaN -sensitive layer.

In inspections using 3D X-ray CT for industrial applications, along with improvements in CT technology and software performance, evaluation methods have improved, such as characterization using energy information and segmentation according to composition information and analysis using conventional transmission images and CT reconstructed images. On the other hand, in the conventional method of checking segmented three-dimensional voxel data with multi-section reconstruction (MPR) images, it is difficult to grasp the location of defects and cracks, and it is difficult to check the overlapped areas of segmented models in the 3D rendering method. In our previous research, a system that represents the internal structure of an object imaged by 3D X-ray CT using Mixed Reality (MR) and combines a spatial reality display and motion capture was proposed so that the internal structure can be grasped spatially with intuitive operation while viewing the object in 3D. This study attempts to represent the information easily spatially from these segmented 3D X-ray CTs. In the experiment, an aluminum die-cast sample was prepared, two surface-rendered models with threshold values suitable for displaying surface and internal defects, performed surface rendering, overlaid with translucent coloring, and pasted MPR images generated from DICOM onto the cross-section according to the position and angle of the surface with MPR images generated from DICOM.

This paper describes the capability of surface flattening of thallium bromide crystals by hot pressing. TlBr detectors are suitable for X-ray imaging applications because of the associated large attenuation coefficients and direct conversion behavior. In the process of developing X-ray imagers such as flat panel detectors, it is essential to form small pixel electrodes on the detector, which requires flatness on the detector surface. However, the TlBr crystal is relatively soft as a semiconductor detector material, and there is a problem in ensuring flatness over a large area using mechanical or chemical polishing. The softness is that the shape of the crystal can be changed by hot pressing, so by pressing the TlBr crystal with a sufficiently flat surface, the flatness of the surface can be improved by an area corresponding to the pressing area. In addition, the TlBr crystal maintains the property of detecting gamma rays in pulse mode even after pressing.

This study introduces a novel denoising method for spectral X-ray computed tomography (CT) images using weighted local regression (WLR). The proposed method exploits the common structural information present across different energy bins. Denoised pixel intensities of a certain energy bin are estimated using the intensities of the other energy bins via WLR. Denoising is achieved by applying a WLR model to the noisy pixel intensities of all energy bins, excluding the target bin, which obtains approximate noise-free intensities for the target energy bin. The performance of our approach was assessed using synthetic spectral X-ray CT images produced using a Monte Carlo photon simulator called the Electron Gamma Shower 5 (EGS5). Both qualitative and quantitative evaluations demonstrated that our approach effectively reduced noise across all energy bins while maintaining image sharpness. Comparisons with common denoising methods demonstrate the effectiveness of the proposed method.

X-ray spectral information is important for X-ray imaging. However, under high dose such as medical CT, pile-up is a problem and correct measurement is difficult. One effective measure is to reduce the detector area, but as the electrodes become smaller, charge-sharing becomes a problem. Different charge-sharing measures are taken by different methods depending on the electrode structure. If only the measurement of the X-ray spectrum at a single point, for example, a detector with a structure of a single pixel and an auxiliary electrode for charge-sharing correction around it can be considered. Such a simple structure allows independent measurement and analysis of output waveforms at all electrodes. When there is a large difference in the mobility of electron and hole such as in Cadmium Telluride (CdTe), pulses that are positively or negatively different from the normal waveform (negative pulses) may be generated depending on the position where the electron-hole pairs occur in the detector. This event includes a charge-sharing event. Therefore, detecting and removing this event can reduce the effects of charge-sharing. Two electrodes of the same size (3mm*1.45mm) were mounted on CdTe for confirmation, and spectrum and signals were measured with a digital MCA and an oscilloscope. As a result, it was confirmed that negative pulses sometimes occur at the same time as normal signals and that the energy resolution of the spectrum can be improved by removing events that occur at the same time as the negative pulses.

In this study, we present an X-ray imaging detector made of single-crystal diamond. Diamond detectors are used in radiotherapy measurements because of their high radiation tolerance and effective atomic number close to that of human tissue. The proposed imager is constructed utilizing a combination of existing technologies; the detector created consists of an indium plate electrode, an 80μm pitch pixelated silver electrode, and a photon-counting readout integrated circuit (ROIC) that operates in hole or electron collection mode. The shape of a 1 mm-thick lead plate was successfully imaged with X-rays emitted from an X-ray tube with a tube voltage of 100 kV. The results of this study motivate the development of an image detector process optimized for single crystal diamond.

In the medical field, X-ray computed tomography (CT) is used to determine the size of defects and damage in an examined object, and to diagnose infectious diseases. Generally, data captured by 3D X-ray CT are viewed as images in three directions (sagittal, axial, and coronal) on a computer. However, augmented reality, virtual reality, and mixed reality are emerging as alternatives for imaging captured data for 3D X-ray CT and are used for medical simulations and educational purposes. Although these techniques are capable of 3D expression, they are limited to the representation of the surface structure of the object. The original function required of these technologies is to check the tomographic image of a specific part of the object by specifying any direction and position in three dimensions. This study proposes a method of representation in which a 2D digital imaging communication image is superimposed on a surface-rendered cross-section of an object. In addition, it proposes a pointing system using motion capture and a spatial reality display. The observer can confirm the object from any direction and understand the structure spatially. It can be moved and rotated with movements similar to actually holding, grabbing, moving, and rotating with hands. Moreover, the cross-section can be observed in any direction. In addition, by matching the respective scales of the device and application, the object can be represented with an error of less than 1 mm in the horizontal, vertical, and depth directions with respect to the actual object. Therefore, the proposed method is an effective 3D representation method in 3D X-rays, which are voxel data containing internal information. Furthermore, this method can easily indicate the desired location where the cross-section image can be viewed in a CT image. This study will help improve the efficiency of 3D X-ray inspection and surgery in the medical field.

Our research has been focusing on X-ray imagers that directly convert highly crystalline semiconductors such as CdTe, CdZnTe, and TlBr to obtain higher energy resolution than indirect conversion detectors that use scintillators. X-ray spectroscopic imaging has the advantages over X-ray imaging without spectroscopic imaging that beam hardening effect tends to be smaller. In this research, contrast adjustment using energy bands in transmission images has attempted. The shot noise generated in each energy band was focused, its coefficient was automatically determined, and corrected to equalize the signal-to-noise ratio. These methods were used to improve the image quality of reconstructed images in X-ray CT and corrected the images focusing on the shot noise in the same way. The effect of the correction on the reconstructed images was verified. The results showed that the image quality was also improved in the reconstructed X-ray CT images.

The morphology of the growth surface near NaCl(100), formed during the pore motion in a crystal due to the temperature gradient, has been studied by the electron microscopic method of vacuum decoration. It is shown that at T = 950 K and ∆μ/kT = 4·10-3, the profile of the vicinal surface in the <11> direction is represented by monoatomic steps, while in the <10> direction, as the surface curvature increases, there is a grouping of steps with the formation of macrosteps – bunches of elementary steps separated by areas of atomically smooth terraces. The sawtooth dependence of the step density on the longitudinal coordinate is described by a particular solution of the Burgers equation for a shock wave. Data on the parameters of three shock waves and the time of their formation are obtained.

Carbon nanotubes (CNTs) are one alternative building block for the new generation of electronics. One of the critical challenges is placing semiconducting CNTs as the active channel in a device configuration, while maintaining compatibility with Si-technology processes. In this work, a CMOS-compatible platform was fabricated in a first stage (as nanoscale gaps in Al electrodes on Si/SiO 2 surfaces) and, in a second stage, CNTs were deposited using an inkjet printing system. By process optimization, devices containing local networks (arrays) of just a few CNTs contributing to transport can be formed. As a proof-of-concept, we also demonstrate the capability of applying an AFM-manipulation technique to modify the CNT network. This study can open a door to advanced fabrication capabilities for CNT-based transistors on a CMOS-compatible platform.

Розглянуто механізми імпульсного лазерного твердофазного легування CdTe індієм при створенні діодних структур для детекторів рентгенівського і гамма-випромінювання. Показано, що масоперенос індію в CdTe при наносекундному лазерному опроміненні структури Іn–CdTе до порога плавлення CdTe відбувається за механізмом бародифузії – внаслідок значного градієнта напружень. Розраховано коефіцієнти масопереносу індію та оцінено середню дрейфову швидкістьпереміщення атомів Іn в CdTe під час опромінення наносекундним імпульсом ексимерного лазера структури Іn–CdTe з товщиною плівки Іn 30 нм при оптимальному для легування значенні густини енергії E = 100 мДж/см2.

Spectral computed tomography (CT) with photon-counting detectors (PCDs) can provide a variety of cross-sectional images, showing improved diagnostic capability at low radiation doses. PCDs acquire and divide signals of each energy intensity into separate energy bins and improve the count rate by pixel size miniaturization, which can simultaneously increase spatial resolution. Nevertheless, PCDs do show some limitations in data processing. Acquisition of large-spectrum data requires large spaces of an analog-to-digital converter (ADC) and a memory in each pixel, and this process generates massive amounts of data traffic. The conventional compression techniques used in CT imaging are not suitable for such traffic because they are applied to the CT image data, not the projection data stored by PCDs. This study aimed to secure ADC and memory space and compress the data traffic while maintaining high image resolution by using a number of energy bin's information for computing. This approach was based on a composite method using CT images from high spatial resolution non-spectral CT and low spatial resolution spectral CT. The resolution in non-spectral CT was recognized by assigning grayscale values, while the resolution for spectral CT was maintained with a pseudocolor scale based on visual characteristics. In this paper, we evaluated the image quality against the compression rate to verify our concept.

The defect structure of CdTe single crystals and spectrometric properties of the CdTe-based Schottky diode-type X/γ-ray detectors with MoO x electrical contacts were studied in order to investigate and understand the roles of structure defects and their effect on the final detector performance. A complex of the crystal surface processing techniques, including preliminary chemical and ion surface etching, laser surface irradiation, metallization and chemical passivation, were employed during contact preparation and electrode formation. The X-ray diffraction investigations of the defect structure of the CdTe crystals and CdTe-based heterostructures were carried out on every stage of the detector fabrication. The correlation between the defect structure of CdTe substrates or MoO x /p-CdTe/MoO x Schottky-diodes and the detector characteristics was established.

The defects structure, charge collection, and detection efficiency of the Ni(NiO)/p-CdTe/Au/Cu Schottky-diode detector have been investigated. The spectroscopic properties of the obtained heterostructures have been studied experimentally and analyzed theoretically. The optimal reverse bias voltage for higher performance of the detectors under study was determined. The reasons of poor charge collection in the detectors and low detection efficiency of photons emitted by an 241Am (59.5 keV) radioisotope have been established and discussed. The techniques of increasing the functional parameters of Ni(NiO)/p-CdTe/Au/Cu Schottky diodes have the investigated and the optimal ways for improvement of the detector performance have been formulated.

The paper is devoted to the study of the features of CdTe surface treatment under laser irradiation with both different wavelengths (lambda = 300-800 nm) and pulse durations (tau(p) = 7 ns-1 ms). The thermal conductivity of the semi-insulating p-like CdTe semiconductor crystals was evaluated using the photoacoustic gas-microphone method. Simulations of the melting threshold were performed based on the three stage model of the laser induced excitation and relaxation. In particular, the following processes were considered in frames of the model: (i) rapid interband thermalization, (ii) nonradiative interband and (iii) nonradiative surface recombination. It was revealed that in the range of pulse durations from 7 ns to 1 mu s, the melting threshold of the CdTe mainly depended on the absorption coefficient alpha(lambda). For pulse durations longer than 1 mu s the threshold started to depend also on the spectra of the reflectivity coefficient R(lambda). The obtained results have been used for optimization of the laser-assisted techniques of surface processing and stimulated doping of CdTe crystals.

Objectives: Sick sinus syndrome (SSS) is a type of bradyarrhythmia that can lead to syncope. It is one of the most common causes of cardiac impairment necessitating pacemaker implantation. However, studies of SSS pathogenesis are neither comprehensive nor conclusive due to limited success in achieving a stable animal SSS model. Here, we report a reproducible canine SSS model by minimally invasive procedure.

We present that fabricating ferroelectric thin film capacitor on electrodes of the X-ray detector to make AC-coupled CdTe X-ray imager. In order to determine the capacitance required for the coupling capacitor, radiation spectrum is measured by using some coupling capacitor have different capacitance. As a result, it was found that the more the capacitance is large, we can get correct radiation spectrum. Because small capacitor with large capacitance is required, BaTiO3 is selected as a high dielectric constant material. We fabricated a ferroelectric thin film capacitor with an area of about 48 mu m(2) and a thickness of about 100 nm by sputtering. As a result of measurement, the capacitance is about 880 pF, and the tendency of variation of dielectric constant with frequency corresponded with past paper. Although the dielectric constant was significantly smaller than the BaTiO3 film in the papers. We considered that the main issue is quality of BaTiO3 film. Quality of film is increased by depositing under high substrate temperature. Performance of CdTe as a radiation detector is deteriorated by high temperature. Therefore, we need to consider the way to deposit BaTiO3 on CdTe at low substrate temperature.