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As an alternative to rigid anodes, a novel concept of X-ray targets consisting of a stream or a multitude of streams of fast tungsten microparticles has recently been proposed. Low-density microparticle streams resemble thin targets with nearly constant intensity distribution over a wide range of photon energies, abruptly terminating at the Duane–Hunt limit of maximum photon energy instead of falling off smoothly. According to our simulations, fast microparticles outperform classical rigid targets and enable extremely high electronic input power density and X-ray output. This opens new possibilities for generating high-intensity, nearly monochromatic X-rays. Such keV-type X-ray sources could replace expensive electron synchrotrons in appropriate applications. Furthermore, for sufficiently thin microparticle streams, the output X-ray spectra are functions of particle size, allowing modulation of the mean photon energy. We simulated the spectral response of tungsten microparticles using Monte Carlo methods and confirmed the validity of our new concept to generate near-monochrome spectra and high intensity with microparticle-based X-ray sources, outperforming classical X-ray tubes. Furthermore, we confirm a weak size dependence of the mean energies of filtered X-rays. We complement previous results highlighting the advantages of microparticle-based X-ray targets and aim at the implementation of the new concept in the future. [ABSTRACT FROM AUTHOR]

The spatiotemporal resolution of diagnostic X-ray images obtained with rotating-anode X-ray tubes has remained limited as the development of rigid, high-performance target materials has slowed down. However, novel imaging techniques using finer detector pixels and orthovolt cancer therapy employing narrow X-ray focal spots demand improved output from brilliant keV X-ray sources. Since its advent in 1929, rotating-anode technology has become the greatest bottleneck to improvement. To overcome this limitation, the current authors have devised a novel X-ray generation technology based on tungsten microparticle targets. The current study investigated a hybrid solution of a stream of fast tungsten microparticles and a rotating anode to both harvest the benefits of the improved performance of the new solution and to reuse known technology. The rotating anode captures energy that may pass a partially opaque microparticle stream and thereby contributes to X-ray generation. With reference to fast-rotating anodes and a highly appreciated small focal spot of a standardized size of 0.3 for an 8° target angle (physical: 0.45 mm × 4.67 mm), we calculated a potential output gain of at least 85% for non-melting microparticles and of 124% if melting is envisioned. Microparticle charging can be remediated by electron backscattering and electron field emission. The adoption of such a solution enables substantially improved image resolution. [ABSTRACT FROM AUTHOR]

This study investigates the critical significance of anode material selection in defining the energy spectrum and properties of X-ray photons in medical physics applications. Using the GATE platform and Monte Carlo simulations, a direct relationship between anode material atomic number and photon fluence is demonstrated. As the atomic number increases from Z = 29 (Copper) to Z = 74 (Tungsten), photon fluence rises by 62 %, indicating a substantial impact on X-ray production. Furthermore, the X-ray spectrum is affected by this material-driven changes, revealing a noticeable shift towards higher energy values: the mean energy of the continuous spectrum rises from 46.97 keV for Copper to 49.0 keV for Tungsten. The thermal properties of the material affect the temperature increase at the focal point. Rhodium and Molybdenum have a higher temperature rise than Copper (Cu) and Tungsten (W), because Cu and W have a greater thermal diffusion compared to other materials. These findings underscore the significance of anode material choice in optimizing X-ray systems which may enhance diagnostic accuracy and efficiency in diverse applications. [ABSTRACT FROM AUTHOR]

The focal spot size of X-ray tube is one of the key factors affecting the imaging resolution, and it is also an important index to characterize the working performance of the X-ray source. Typically, after the X-ray tube is manufactured, the focal spot size must be measured and marked. Nowadays, the most widely used measurement standards for X-ray tube focal spot size in the world are IEC 60336, EN 12543, and ASTM E1165. Between various standards, there are differences in the focal spot size measurement methods, scope of application, loading factors and imaging equipment. Among these, the slit method of EN 12543 standard is mostly utilized in industrial X-ray tubes. However, due to its complex and precise design requirements, the test equipment, i.e., the slit camera, is difficult to produce and process, and the cost is high, which is not conducive to promotion and application. This paper studied the influence and variation of the measurement of the focal spot size at different slit sizes by using double tungsten alloy cylinders instead of slit camera. Based on the calibration of distance and position parameters in the cylinder method, the measurement equipment was conveniently positioned, and the distance between the focal spot and the translation mechanism was measured simultaneously, which improves the position accuracy of the focal spot size measurement. Additionally, the formula for determining the focal spot size in the slit method was improved, so that the slit method can be applied to a wide range of slit widths. In particular, the geometric magnification of the system can be measured directly when the slit width is large, skipping the step of measuring the distance between the focal spot and the translation mechanism. The experiment scheme has low requirements on the centering conditions of the equipment and the distribution of the X-ray source. In the data processing process, dark field correction and bright field correction were used to eliminate the problem of inconsistency in the response characteristics of each detector pixel, and the Wiener Filtering was performed on the signal output by the detector to deal with Gaussian noise and uniformly distributed noise. The experiment results show that relatively accurate measurement values can be obtained by measuring MXR-225HP/11 with double tungsten alloy cylinders with the same spacing as the focal spot size. The measurement relative error is less than 10%. According to international standards, when the measurement results are within plus or minus 10% of the theoretical value, it can be used as a method to determine the focal spot size. Therefore, the improved method in this paper is reliable and does not require high testing equipment, allowing it to be widely used. In addition, the geometric magnification of the focus measurement device can be directly calculated when the slit width is larger than the focal spot size, and the calculation results are consistent with the results measured in the cylinder method.

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As an alternative to rigid anodes, a novel concept of X-ray targets consisting of a stream or a multitude of streams of fast tungsten microparticles has recently been proposed. Low-density microparticle streams resemble thin targets with nearly constant intensity distribution over a wide range of photon energies, abruptly terminating at the Duane–Hunt limit of maximum photon energy instead of falling off smoothly. According to our simulations, fast microparticles outperform classical rigid targets and enable extremely high electronic input power density and X-ray output. This opens new possibilities for generating high-intensity, nearly monochromatic X-rays. Such keV-type X-ray sources could replace expensive electron synchrotrons in appropriate applications. Furthermore, for sufficiently thin microparticle streams, the output X-ray spectra are functions of particle size, allowing modulation of the mean photon energy. We simulated the spectral response of tungsten microparticles using Monte Carlo methods and confirmed the validity of our new concept to generate near-monochrome spectra and high intensity with microparticle-based X-ray sources, outperforming classical X-ray tubes. Furthermore, we confirm a weak size dependence of the mean energies of filtered X-rays. We complement previous results highlighting the advantages of microparticle-based X-ray targets and aim at the implementation of the new concept in the future.

X-ray tube can easily produce X-ray, which is widely used in industry, archaeology and medicine. X-ray tubes use the interaction between high-speed electrons and anodic target atoms to generate X-rays, including discrete characteristic X-rays and continuous bremsstrahlung spectrum. Their spectral distribution is an important parameter index, which is the basis of subsequent applications. The spectral distribution can be obtained by actual measurement, Monte Carlo simulation and analytical calculation. Here, the analytical calculation of bremsstrahlung spectrum was mainly studied. Analytical calculation is to quickly calculate the bremsstrahlung spectrum produced by X-ray tube using known parameters. The key to its accuracy is the depth distribution of electrons in the anode target. By analyzing the depth distribution of electrons in the anode target, an analytical calculation model for the bremsstrahlung spectrum of electrons with incident energy from 10 to 50 keV in the copper target was established. Due to the elastic and inelastic interactions, the electron transport process in the target is very complex, and it is difficult to obtain the electron depth distribution by experimental or theoretical analysis. Monte Carlo simulation software Geant4 was used to simulate the interaction between the electron and copper target with incident energy of 10, 20, 30, 40 and 50 keV. The count, energy distribution and angle distribution of the electron at different penetration depths were obtained. The empirical formulas of electron depth distribution and path length correction coefficient of 10.50 keV electrons in copper target were obtained by fitting the simulated data. Since the penetration depth was scaled by using the continuous slowing down approximation range RCSDA, the parameters of the fitted empirical formula were approximately independent of the incident energy of electrons in this energy segment. The calculated results of the empirical formula for the electron depth distribution are in good agreement with the data of the electron depth distribution simulated by Geant4, which can accurately represent the electron depth distribution and the correction coefficient of path length. Combining the empirical formulas of electron depth distribution and path length correction coefficient with the corresponding bremsstrahlung cross-section data, an analytical calculation model of the bremsstrahlung spectrum of the thick target reflection type X-ray tube was established. Compared with Monte Carlo simulation results, the analytical calculation model has high accuracy and is in good agreement with the simulation results. When the electron incident energy is 15, 25, 35 and 45 keV, the spectral errors are 0.036 6, 0.041 7, 0.040 8 and 0.038 9, respectively. Compared with Monte Carlo simulation of X-ray tube bremsstrahlung spectrum, the analytical calculation speed is faster and can achieve high accuracy, which can be used in the need of fast calculation of X-ray tube bremsstrahlung spectrum.

The spatiotemporal resolution of diagnostic X-ray images obtained with rotating-anode X-ray tubes has remained limited as the development of rigid, high-performance target materials has slowed down. However, novel imaging techniques using finer detector pixels and orthovolt cancer therapy employing narrow X-ray focal spots demand improved output from brilliant keV X-ray sources. Since its advent in 1929, rotating-anode technology has become the greatest bottleneck to improvement. To overcome this limitation, the current authors have devised a novel X-ray generation technology based on tungsten microparticle targets. The current study investigated a hybrid solution of a stream of fast tungsten microparticles and a rotating anode to both harvest the benefits of the improved performance of the new solution and to reuse known technology. The rotating anode captures energy that may pass a partially opaque microparticle stream and thereby contributes to X-ray generation. With reference to fast-rotating anodes and a highly appreciated small focal spot of a standardized size of 0.3 for an 8° target angle (physical: 0.45 mm × 4.67 mm), we calculated a potential output gain of at least 85% for non-melting microparticles and of 124% if melting is envisioned. Microparticle charging can be remediated by electron backscattering and electron field emission. The adoption of such a solution enables substantially improved image resolution.

The focal spot size of X-ray tube has great impact on the image quality in radiographic testing. Typical EN 12543 standard gives five measuring methods (scanning method, pinhole camera radiographic method, slit camera radiographic method, edge method and measurement of the effective focal spot size of mini and micro focus Xray tubes) for focal spot size of industrial Xray systems. The testing conditions and equipment of these methods are complicated except the edge method. However, the edge method cannot be used for an absolute measurement of the focal spot. It is only useful for the checking of focal spot under field condition in order to find change of the focal spot. Based on the edge method of EN 12543, an innovative method called cylinder method for the absolute measurement was proposed in this paper. This method was different from traditional measurement of the focal spot perpendicular to X-ray emission direction called nominal focus. It could measure the focal spot size at arbitrary angle within the field angle of radiation beam by using shift-rotation mechanism. In this experiment, the focal spot size of MXR-225HP/11 was measured by double tungsten alloy cylinder and 100 μm pixel areaarray detector. Double tungsten alloy cylinder could reduce the influence of scattering and the spacing between two cylinders was designed to be variable in preparation for future research on the silt camera radiographic method. Pixel areaarray detector overcame the shortcomings of film photography and was convenient for computer image processing. In order to improve the accuracy of measurement, a calibration method for measuring the distance parameter from the focal spot to the shiftrotation mechanism and location parameter at arbitrary angle was proposed. By measuring the large and small focal spot size of MXR225HP/11 at different angles in the width and length directions, it is found that the focal spot size varies with angle and nominal focus sizes agree well with those measured by pinhole camera radiographic method provided in the manual. However, the variation law of effective focal spot size with angle in the width direction is quite different from the theoretical analysis results, and the reasons need to be further explored. The results show this method can accurately measure the nominal focus size but also the focal spot size variation within the field angle of radiation beam which will provide reference for the design of focal spot and performance evaluation of Xray tube. Besides, the layout of imaging system can be optimized by the variation of focal spot size to ensure high imaging quality.

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The air kerma, which is the amount of energy given off by a radioactive substance, is essential for medical specialists who use radiation to diagnose cancer problems. The amount of energy that a photon has when it hits something can be described as the air kerma (the amount of energy that was deposited in the air when the photon passed through it). Radiation beam intensity is represented by this value. Hospital X-ray equipment has to account for the heel effect, which means that the borders of the picture obtain a lesser radiation dosage than the center, and that air kerma is not symmetrical. The voltage of the X-ray machine can also affect the uniformity of the radiation. This work presents a model-based approach to predict air kerma at various locations inside the radiation field of medical imaging instruments, making use of just a small number of measurements. Group Method of Data Handling (GMDH) neural networks are suggested for this purpose. Firstly, a medical X-ray tube was modeled using Monte Carlo N Particle (MCNP) code simulation algorithm. X-ray tubes and detectors make up medical X-ray CT imaging systems. An X-ray tube's electron filament, thin wire, and metal target produce a picture of the electrons' target. A small rectangular electron source modeled electron filaments. An electron source target was a thin, 19,290 kg/m3 tungsten cube in a tubular hoover chamber. The electron source–object axis of the simulation object is 20° from the vertical. For most medical X-ray imaging applications, the kerma of the air was calculated at a variety of discrete locations within the conical X-ray beam, providing an accurate data set for network training. Various locations were taken into account in the aforementioned voltages inside the radiation field as the input of the GMDH network. For diagnostic radiology applications, the trained GMDH model could determine the air kerma at any location in the X-ray field of view and for a wide range of X-ray tube voltages with a Mean Relative Error (MRE) of less than 0.25%. This study yielded the following results: (1) The heel effect is included when calculating air kerma. (2) Computing the air kerma using an artificial neural network trained with minimal data. (3) An artificial neural network quickly and reliably calculated air kerma. (4) Figuring out the air kerma for the operating voltage of medical tubes. The high accuracy of the trained neural network in determining air kerma guarantees the usability of the presented method in operational conditions. [ABSTRACT FROM AUTHOR]

Multi-target X-ray tube is a new type X-ray source, and can be applied in many fields such as sensitive X-ray fluorescence analysis and medical imaging. In this work, we report an electric field modulation multi-target X-ray tube, which contains four targets (Cr, Ni, Au, Mo) coated on a Beryllium (Be) window. A four-valve electric field deflector was developed to deflect the electron beam to bombard the corresponding targets. Particle dynamics analysis software was employed to simulate the particle tracking of electron beam. The results show that the 30 keV electron beam could get a 6.7 mm displacement on the target plane by 105 V/m electric field. The focus areas are about 2 mm × 5 mm and 4 mm × 2.5 mm after deflection in two directions. Thermal behavior calculated by ANSYS shows that the designed target assembly could withstand a 10 W continuous power. The optimum target thicknesses and emission spectra were obtained by Geant4 when the thickness of Be window was 300 μm and the electron beam incident angle was 0.141 rad. The results indicate that this multi-target X-ray tube could provide different X-ray sources effectively.

The air kerma, which is the amount of energy given off by a radioactive substance, is essential for medical specialists who use radiation to diagnose cancer problems. The amount of energy that a photon has when it hits something can be described as the air kerma (the amount of energy that was deposited in the air when the photon passed through it). Radiation beam intensity is represented by this value. Hospital X-ray equipment has to account for the heel effect, which means that the borders of the picture obtain a lesser radiation dosage than the center, and that air kerma is not symmetrical. The voltage of the X-ray machine can also affect the uniformity of the radiation. This work presents a model-based approach to predict air kerma at various locations inside the radiation field of medical imaging instruments, making use of just a small number of measurements. Group Method of Data Handling (GMDH) neural networks are suggested for this purpose. Firstly, a medical X-ray tube was modeled using Monte Carlo N Particle (MCNP) code simulation algorithm. X-ray tubes and detectors make up medical X-ray CT imaging systems. An X-ray tube’s electron filament, thin wire, and metal target produce a picture of the electrons’ target. A small rectangular electron source modeled electron filaments. An electron source target was a thin, 19,290 kg/m3 tungsten cube in a tubular hoover chamber. The electron source–object axis of the simulation object is 20° from the vertical. For most medical X-ray imaging applications, the kerma of the air was calculated at a variety of discrete locations within the conical X-ray beam, providing an accurate data set for network training. Various locations were taken into account in the aforementioned voltages inside the radiation field as the input of the GMDH network. For diagnostic radiology applications, the trained GMDH model could determine the air kerma at any location in the X-ray field of view and for a wide range of X-ray tube voltages with a Mean Relative Error (MRE) of less than 0.25%. This study yielded the following results: (1) The heel effect is included when calculating air kerma. (2) Computing the air kerma using an artificial neural network trained with minimal data. (3) An artificial neural network quickly and reliably calculated air kerma. (4) Figuring out the air kerma for the operating voltage of medical tubes. The high accuracy of the trained neural network in determining air kerma guarantees the usability of the presented method in operational conditions.

Purpose: To develop a method to perform quality control (QC) of X‐ray tubes and automatic exposure control (AEC) as a part of the QC of the radiographic and fluoroscopic X‐ray system. Our aim is to verify the output from the X‐ray tube by comparing the measured radiation output, or air kerma, to the theoretical output given the applied exposure settings and geometry, in addition to comparing the measured kV to the nominal kV. The AEC system for fluoroscopic and conventional X‐ray systems is assessed by determining the absorbed dose to a homogenous phantom with different thicknesses. Method: This study presents a model to verify the X‐ray tube measurement results and a method to determine the dose to a homogenous phantom (Dphantom). The following input is needed: a parameterized model of the X‐ray spectrum, the X‐ray tube measurements using a multifunctional X‐ray meter, the exposure parameters recorded via imaging of polymethyl methacrylate (PMMA) slabs of different thickness that simulate the patient using AEC, and a parameterized model for calculating the dose to water from Monte Carlo simulations. The output is the entrance surface dose (ESD) and absorbed dose in the phantom, Dphantom (µGy). In addition, the parameterized X‐ray spectrum is used to compare theoretical and measured air kerma as a part of the QC of the X‐ray tube. To verify the proposed method, the X‐ray spectrum provided in this study, SPECTRUM, was compared to two commercially available spectra, SpekCalc and Institute of Physics and Engineering in Medicine (IPEM) 78. The fraction of energy imparted to the homogenous phantom was compared to the imparted fraction calculated by PCXMC. Results: The spectrum provided in this study was in good agreement with two previously published X‐ray spectra. The absolute percentage differences of the spectra varied from 0.05% to 3.9%, with an average of 1.4%, compared to SpekCalc. Similarly, the deviation from IPEM report 78 varied from 0.02% to 2.3%, with an average of 0.74%. The SPECTRUM was parameterized for calculation of the imparted fraction for target angles of 10°, 12°, and 15°, kV (50–150 kV) with the materials Al (2.2–8 mm), Cu (0–1 mm), and any combination of the filters, PMMA and water. The deviation of energy imparted from the results by PCXMC was less than 8% for all measurements across different kV, filtration, and vendors, obtained by using PMMA to record the exposure parameters, while the dose was calculated based on water with same thicknesses as the PMMA. Conclusion: This study presents an accurate and suitable method to perform a part of the QC of fluoroscopic and conventional X‐ray systems with respect to the X‐ray tube and the associated AEC system. The method is suitable for comparing protocols within and between systems via the absorbed dose. [ABSTRACT FROM AUTHOR]

Near background low dose rate measurements are important part of the environmental radiation monitoring. It is possible to fulfill energy response verification for the high sensitive dosimeters based on inorganic scintillation detectors in low energy region when creating reference X-ray fields with dose rates up to 5 µSv/h. The aim of this work was to create and study reference X-ray fields with low dose rate and narrow spectrum in the energy range from 15 to 250 keV using high-purity metal filters as a part of X-ray irradiator of AT300 X-ray calibration facility.To determine the main characteristics of created X-ray fields highly sensitive comparators of photon radiation based on NaI(Tl) scintillation detectors was used. The comparators were developed in “ATOMTEX”. To verify comparators energy response the reference AT5350/1 dosimeter and ionization chamber TM32003 with sensitive volume 10000 cm3 were used.Characteristics of X-ray fields that were created on the AT300 X-ray calibration facility to verify the energy response of high sensitive dosimeters based on scintillation detectors were investigated. The possibility to calibrate high sensitive dosimetric measuring instruments based on scintillation detectors in the energy range up to 250 keV in X-ray beams was shown.

Two phase flows are of particular importance in various research fields. In the current article, a novel system consists of an X-ray tube and one sodium iodide crystal detector with ability of determining type of flow regime as well as void fraction percentage of a two phase flow, is proposed. MCNP-X code was used for physical modelling of the proposed system and its performance. Radial basis function (RBF) was also implemented for analyzing and classifying the obtained data from the proposed system. Counts in each 1 keV energy bin of photon energy spectra in the detector were inserted in RBF as inputs data set and flow regime and void fraction percentage were obtained as the two outputs. After training the RBF network, the system could simultaneously recognize all the flow regimes and predict the void fraction percentage of a modelled liquid–gas two-phase flow with an acceptable error. The proposed methodology in the present paper has three main novelties and advantages over former studies. Firstly, in this system an X-ray tube is used compared to previous studies where one or more radioisotope sources served as radiation source in a radiation based multi-phase flow meter. Secondly, in former works at least two detectors were used to recognize type of flow pattern and meter volume fractions simultaneously, while in this study only one detector is utilized. Thirdly, in this study just one neural network is used, while in other studies more than one network was used. [ABSTRACT FROM AUTHOR]

We have stabilized and equalized field-emission (FE) currents from carbon nanotube (CNT) emitters by a cascade active-current-control (ACC) using two transistors. Theoretical and experimental analyses on the cascade ACC operation, including single ACC with a single transistor, were done for both diode- and triode-configured CNT emitters. A fully vacuum-sealed CNT FE X-ray tube (FEXT) was used as a triode-configured test device. FE currents, in both configurations, by the cascade ACC were found to be stabilized to a standard deviation of 0.05% even in high-voltage and high-power circumstances while the single ACC could hardly regulate fluctuations in FE currents from CNT emitters. Furthermore, an array of CNT FEXTs successfully demonstrated a completely equalized emission current when the cascade ACC was employed. This result has important implications for FEXT current uniformity and other FEXTs applications, because the cascade ACC can equalize FE currents even through large variation of CNT emitters, thereby greatly enhancing the usability of FE devices. [ABSTRACT FROM AUTHOR]

BackgroundAs a hot material, diamond has been widely used in various civil and military equipment with high hardness (Mohs hardness is 10), compressive strength (greater than 1.2 GPa), excellent thermal (thermal conductivity at room temperature is 20~22 W·cm-1·K-1, thermal expansion coefficient at room temperature is only (1.1~1.3)×10-6 K-1), optical (higher transparency to X-rays) and electrical properties. Traditional optical window material beryllium is harmful to the human body and industrial hazards, its hardness, thermal conductivity and the thermal expansion coefficient are much lower than that of diamond.PurposeThis study aims to explore the performance of micro X-ray tube with diamond optical window by simulation, obtain the best thickness of diamond for X-ray tube optical window and its shielding effect against low, medium and high energy X-ray.MethodsThe Monte Carlo method was used to calculate the effective transmission ratio, peak back ratio and transmission ratio of characteristic X rays with diamond optical window in high energy region. The X-ray tube with 50 kV tube voltage and 1.0 mA tube current was taken as an example to determine the optimal thickness of diamond.ResultsSimulation results show that the Kα characteristic X-ray effective transmittance and peak to total X-ray ratio of the silver target increase continuously with the increase of the diamond window thickness, and the optimum diamond thickness is 2.0 mm. Under the optimal thickness of 2.0 mm, the effective transmittance is 154.5%, high-energy X-ray transmittance is 74.5%, and the characteristic X-ray peak back ratio is 27.9%.ConclusionsDiamond can be used as a substitute for beryllium optical windows and has good application prospect.

In this paper, the feasibility of using an X-ray tube instead of radioisotope sources for measuring volume fractions of gas, oil, and water in two typical flow regimes of three-phase flows, namely, annular and stratified, is evaluated. This study’s proposed detection system is composed of an X-ray tube, a 1 inch × 1 inch NaI detector, and one Pyrex-glass pipe to model different volume fractions for two flow regimes, annular and stratified. Group method of data handling (GMDH), a powerful regression tool, was also implemented to analyze the obtained data. The obtained results in this work indicate that a simple system based on an X-ray tube and just one NaI detector could be a potential alternative to radioisotope-based systems for separate measurements of gas, oil, and water volume fractions in annular and stratified flow regimes of a three-phase flow.

For real-time computed tomography (CT), a temporal resolution lower than 30 ms is required, which cannot be delivered by conventional CT architectures with a rotation gantry. Stationary CT architecture can achieve a temporal resolution lower than 30 ms by eliminating the physical rotation of the gantry and by electronically sweeping X-ray beams across the gantry. Stationary CT architecture utilizes two separate arrays, one for distributed X-ray sources and another for detectors. These individual X-ray sources are required to be compact, fast, and individually addressable in order to acquire 200+ projections for successful CT reconstruction and to achieve a temporal resolution lower than 30 ms. A compact X-ray tube that fits these requirements is being developed. The aim of this paper was to design an electrostatic electron focusing lens for the first-generation prototype compact X-ray tube primarily consisting of a carbon nanotube-based electron source and a transmission-type anode by studying the multiple variables that affect the focal spot size (FSS) and by comparing different types of electrostatic lenses with the help of simulations. This multivariable simulation study was conducted using an object-oriented particle-in-cell code, OOPIC PRO. The results of these simulations showed the following: Einzel lens can achieve the required FSS (lower than 1 mm); lens aperture, thickness, and location of the lens can be used as a coarse control over the FSS, whereas the lens potential can be used as a fine control; and the chromatic and spherical aberrations can be reduced if Einzel lens is used. [ABSTRACT FROM AUTHOR]

Actuality of this work is related to human radiation safety during tuning and regulation of X-ray devices in the process of their development and production. The more precise the calculations for the device are, the less time is required for its tuning and regulation, and thus people are less exposed to radiation. When developing an X-ray device, it is necessary to choose an X-ray tube and filters taking into account the application domain of the device. In order to do this, one should know anode voltage, X-ray tube anode current, material and thickness of filters, i.e. to calculate these characteristics at the set quality of X-ray radiation. The known published studies do not give any solution to this problem. The scientific novelty of this work is that it establishes the interdependence between main characteristics of the X-ray device: the function of the device defines the quality of X-ray radiation (mean photon energy and air kerma power); mean photon energy depends on the X-ray anode tube voltage and spectral resolution; air kerma power depends on anode tube voltage, current of X-ray tube anode, spectral resolution, thicknesses of the filters and their materials; spectral resolution depends on thicknesses of filters and their materials; thickness of filters depends on the material of the filter (the linear coefficient of weakening of X-ray radiation). Knowledge of interdependence of basic characteristics of the X-ray devices allowes developing simple algorithm for their calculation at the values of homogeneity coefficient from 0,8 to 1, which makes it possible to choose an X-ray tube and filters with the purpose of obtaining X-ray radiation of the set quality.

Compound refractive lens was used for measuring size of 2-3 beamline Standford synchrotron radiation source and a size of microfocus X-ray tube. X-ray beam from the source was focused by the lens and parameters of the beam at image plane were measured. Scanning diaphragm and X-ray CCD-camera were used for measuring X-ray beam. It was found that the vertical size of synchrotron source is equal to 0,6 mm and the size of the X-ray tube focal spot is equal to 60 micrometers.

Tube arcing artifact is known to be caused by a temporary short circuit in the X-ray tube causing momentary loss of X-ray output. It is seen as near-parallel and an equidistant streak pattern on transaxial computed tomography (CT) images and as a "horizontal" hypodense band on the coronal and sagittal CT images. This artifact can be a random occurrence and was caused in this particular case due to voltage fluctuations in the high-voltage supply transformer supplying the rotor of the anode in the X-ray tube. This problem was initially corrected by reducing the tube voltage to 120 kV from the original 140 kV and, subsequently, replacing the faulty transformer. This kind of artifact, which is a very rare situation, can affect the image quality, and could also be an early sign of equipment failure. To the authors′ knowledge, such an artifact has not been reported till date in a clinical scenario. Hence, we would like to report a rare situation of tube arcing artifact along with a unique remedy.

The results of experimental investigations of the characteristics of the X-ray emitter cooling system, based on dielectric heat pipes are shown. The cooling system combines the high efficiency of heat transfer and electrical insulating properties at voltages of 100 kV.

In this paper, a high rigidity and high speed rotating mechanism using a new concept hydrodynamic bearing in X-ray tube for high speed computed tomography is proposed. In order to obtain both the stability and the high load carrying capacity, the hydrodynamic bearing lubricated by liquid metal (Gallium alloy), named as the hybrid hydrodynamic bearing generates the lubricating film by wedge effect on the plane region between the spiral grooves under high loading condition. The parallelism between the bearing and the rotating body can be secured by optimizing the rigidity distribution of stationary shaft in the proposed rotating mechanism. By carrying out the fundamental design by numerical analyses, it has been made clear that the hybrid hydrodynamic bearing and the rotating mechanism are suitable for the X-ray tube used in the CT with ever-increasingly scanning speed.

Objective: Over 1/3 to half of accurate medical diagnosis are based on x-ray examinations. The x-ray tube is the main part of a radiology set. X-ray production is a phenomenon with low efficiency and over 99.6% of the fast electrons energy changes to heat. This heat is also a limiting factor for the system function. The aim of this study was to design and manufacture an automatic heat control system in radiology tubes for multiple exposures. These exposures are allowed with regard to overload system but inappropriate intervaling in exposures causes heat damages in anode. Methods: The hardware of system was designed and manufactured by using of micro-controller system. Its software was written by 8051 Franklin preview software package and on the basis of anode cooling chart data and installed on micro-controller by A1-11 system. Findings: The designed system can calculate and display anode heat at every moment. Functioning test in 100 experimental exposures showed a reliability of 99.92±0.07%. Conclusion: This system can be used as a suitable equipment in protecting and preventing radiology tubes against heat damages after frequent exposures.

A new hemispherical-geometry cathode for field emission (FE) X-ray tubes was designed and simulated in this study. The electric field strength distribution on the hemispherical-geometry cathode was calculated and used to predict the emission current. Because of their unique FE properties, carbon nanocoils were used as the electron emitters for simulation and modeling. The results show that a large tolerance is permitted, and the performance attained with ±20° cathode misalignment was nearly identical to that without misalignment. The maximum emission current can be achieved using a hemispherical-geometry cathode with a radius of 1 mm. Additional advantages of FE X-ray tubes with hemispherical-geometry cathodes are higher FE currents, shorter response times, and smaller X-ray spot sizes. In addition, lower power consumption, longer lifetimes, and higher resolutions are expected with this simple and low-cost design. [ABSTRACT FROM AUTHOR]