Atomic Number Ratio Research Articles

Improving the accuracy of density logging results considering mineral composition for evaluation of high-level radioactive waste disposal sites

ABSTRACT Site selection and characterisation are key factors influencing the safe, stable disposal of spent nuclear fuel. Site selection can be based on geophysical surveys, and geophysical well logging is performed at the detailed survey stage. Typically, gamma – gamma density logging is conducted to continuously obtain in situ density information regarding the well depth. However, gamma – gamma density logging is often influenced by the geological characteristics of the site. The ratio of atomic number to atomic weight is required to convert the electron density obtained through density logging counts into bulk density. Because it is difficult to calculate these ratios for the entire depth, an equation based on water-filled limestone is typically used for conversion. Therefore, as the difference in the ratio of the atomic number and atomic weight increases relative to that of limestone, the difference between the converted bulk density and the actual bulk density increases. In this study, equations were derived for various mineral compositions and applied to the density logging results. Matrix density was analyzed using a pycnometer, and the ratio between the atomic number and weight was calculated according to X-ray fluorescence analysis results. This approach improved the accuracy of the density logging data and reduced density errors. The proposed method is expected to be particularly useful for estimating in situ density at high-level radioactive waste disposal sites without complex geological formations.

Surface Stability and Exfoliability of Non-van der Waals Magnetic Chromium Tellurides.

Exfoliation of two-dimensional (2D) magnetic materials from non-van der Waals (non-vdW) materials has attracted increasing attention because it provides a great platform for the construction of 2D magnetic materials. For non-vdW magnetic chromium tellurides with high Curie temperatures, their few-layer samples show promising applications in the field of spintronics. However, there is still no consensus on whether the surface structures of few-layer chromium tellurides should be terminated by Cr or Te atoms. By calculating the surface and exfoliation energy, we find that which structure is more stable depends greatly on the value of the chemical potential of Te atoms, and the few-layer sample with a Cr-terminated surface is easier to exfoliate than that with both Te-terminated surfaces. Finally, we propose that different exfoliated structures can be identified by using the atomic number ratio of Cr to Te and the average magnetic moment of Cr atoms in few-layer samples.

In vivo assessment of tissue-specific radiological parameters with intra- and inter-patient variation using dual-energy computed tomography.

Experimental in vivo determination of radiological tissue parameters of organs in the head and pelvis within a large patient cohort, expanding on the current standard human tissue database summarized in ICRU46. Relative electron density (RED), effective atomic number (EAN) and stopping-power ratio (SPR) were obtained from clinical dual-energy CT scans using a clinically validated DirectSPR implementation and organ segmentations of 107 brain-tumor (brain, brainstem, spinal cord, chiasm, optical nerve, lens) and 120 pelvic cancer patients (prostate, kidney, liver, bladder). The impact of contamination by surrounding tissues on the tissue parameters was reduced with a dedicated contour adaption routine. Tissue parameters were characterized regarding the cohort mean value as well as the variation within each patient (2σintra) and between patients (2σinter). For the brain, age-dependent differences were determined. For 10 organs, including 4 structures not listed in ICRU46, the mean RED, EAN and SPR as well as their respective intra- and inter-patient variation were determined. SPR intra-patient variation was higher than 1.3% (1.3-4.6%) in all organs and always exceeded the inter-patient variation of the organ mean SPR (0.6-2.1%). For the brain, a significant SPR variation between pediatric and non-pediatric patients was determined. Radiological tissue parameters in the head and pelvis were characterized in vivo for a large patient cohort using dual-energy CT. This reassesses parts of the current standard database defined in ICRU46, furthermore complementing the data described in literature by smaller substructures in the brain as well as by the quantification of organ-specific inter- and intra-patient variation.

Correlation between the breaking behavior and the initial microstructural defects of the metallic nanowires: An approach from statistical analysis

It is speculated that the initial slip in the single-crystal nanowire (NW) is dominant to the final breaking position. To reveal the correlation between the initial slip and breaking position, in this paper, up to 300 independent [111] oriented single-crystal copper NWs under uniaxial tension at a temperature of 10 K have been performed using molecular dynamics (MD) simulations. Combining with Machine Learning, the position of the initial slip is determined by the density-based spatial clustering of applications with noise (DBSCAN) algorithm. The breaking position is calculated using the atom number ratio (ANR). The calculations illustrate that the final breaking positions follow two Gaussian distributions at two ends of the NW. Similarly, the distribution of the initial slip positions also has statistical peaks at the two ends and an additional distribution at the center of the NW within a large span. The results demonstrated that there is a clear correlation between the initial slips and the breaking positions on the basis of the distribution features. Further, four representative samples were studied systematically from the aspects of the microstructure and the stress–strain properties, showing that the final breaking position is determined at the middle and late stages of the plastic deformation. It infers that the apparent correlation between the initial slip positions and the final breaking positions of NWs exhibits statistically rather than causally. The conclusion derived from this study may contribute to promoting the fundamental research of metal nanomaterials and the optimization of the nanodevices.

Comparison of Four Dual-Energy CT Scanner Technologies for Determining Renal Stone Composition: A Phantom Approach.

Background Studies have investigated the value of various dual-energy CT (DECT) technologies for determining renal stone composition. However, sparse multivendor comparison data exist. Purpose To compare the performance of four DECT technologies in determining renal stone composition at standard- and low-dose acquisitions. Materials and Methods This was an in vitro phantom study. Seventy-one urinary stones (size: 2.7-14.1 mm) of known chemical composition (51 calcium, four struvite, four cystine, and 12 urate) were placed in a custom-made cylindrical phantom. Consecutive scans with manufacturer-recommended protocols and dose-optimized institutional protocols (up to 80% reduction in volumetric CT dose index) were obtained with rapid kilovolt peak switching DECT (rsDECT) (n = 2), dual-source DECT (n = 2), twin-beam DECT (tbDECT) (n = 1), and dual-layer detector-based CT (dlDECT) (n = 1) scanners. The image data sets were analyzed using effective atomic number and dual-energy ratio indexes of maximally available and comparable spectra. The performance of each combination of scanner technology, method, and acquisition was assessed. Logistic regression models were used to calculate the area under the receiver operating characteristic curve (AUC). Results After image analysis, all scanners except tbDECT had an AUC greater than 0.95 in at least one acquisition in distinguishing urate from other stones. All DECT techniques were able to help differentiate calcium oxalate monohydrate stones with moderate accuracy (AUC: 0.70-0.83), and brushite was differentiated from urate with AUC greater than 0.99. There was no correlation between performance and acquisition with dose-optimized and/or vendor-recommended settings. Conclusion All four dual-energy CT (DECT) technologies enabled accurate determination of stone composition at standard- and low-dose acquisitions; however, performance varied based on the scanner parameters, DECT technique, and stone type. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Ringl and Apfaltrer in this issue.

Measurement of material isotopics and atom number ratio with [formula omitted]-particle spectroscopy for a NIFFTE fission Time Projection Chamber actinide target

We present the results of a measurement of isotopic concentrations and atomic number ratio of a double-sided actinide target using α-spectroscopy and mass spectrometry. The double-sided actinide target, with predominantly 239Pu on one side and 235U on the other, was used in the fission Time Projection Chamber (fissionTPC) for a measurement of the neutron-induced fission cross-section ratio between the two isotopes. The measured atomic number ratio is needed to extract an absolute measurement fission cross-section ratio. The 239Pu/235U atom number ratio was measured with a combination of mass spectrometry and α-spectroscopy with a planar silicon detector achieving uncertainties of less than 1%. Different strategies for estimating isotopic concentration from the α-spectrum are presented to demonstrate the potential of these methods for non-destructive target assay. We found that a combination of fitting spectra with constraints from mass spectrometry, and summing counts in a region of the spectrum provided the most consistent results with the lowest uncertainty.

Miscibility Regimes in a 23Na–39K Quantum Mixture

The effects of miscibility in interacting two-component classical fluids are relevant in a broad range of daily applications. When considering quantum systems, two-component Bose–Einstein condensates provide a well-controlled platform where the miscible–immiscible phase transition can be completely characterized. In homogeneous systems, this phase transition is governed only by the competition between intra- and inter-species interactions. However, in more conventional experiments dealing with trapped gases, the pressure of the confinement increases the role of the kinetic energy and makes the system more miscible. In the most general case, the miscibility phase diagram of unbalanced mixtures of different atomic species is strongly modified by the atom number ratio and the different gravitational sags. Here, we numerically investigate the ground-state of a 23Na–39K quantum mixture for different interaction strengths and atom number ratios considering realistic experimental parameters. Defining the spatial overlap between the resulting atomic clouds, we construct the phase diagram of the miscibility transition which could be directly measured in real experiments.

KV-kV and kV-MV DECT based estimation of proton stopping power ratio - a simulation study.

This study aims to estimate the proton stopping power ratio (SPR) by using 80-120kV and 120kV-6MV dual-energy CT (DECT) in a fully simulation-based approach for proton therapy dose calculations. Based on a virtual CT system, a two-step approach is applied to obtain the reference attenuation coefficient for image reconstruction. The effective atomic number (EAN) and electron density ratio (EDR) are estimated from two CT scans. The SPR is estimated using a calibration based on known materials to obtain a piecewise linear relationship between the EAN and the logarithm of the mean excitation energy, lnIm. The calibration phantoms are constructed from reference tissue materials taken from ICRU Report 44. Our approach is evaluated through using the ICRP110 human phantom. The respective influences of noise and beam hardening effects are studied. With the beam hardening correction applied, the results of 120 kV-6 MV DECT are comparable to those of 80-120 kV DECT in predicting the EAN, but the former demonstrated a clear improvement in predicting the EDR and SPR. The 120 kV-6 MV DECT is able to predict the SPR within an accuracy of 10% for lung tissue and 5% for pelvis tissue, thereby outperforming the 80-120 kV DECT. The 120 kV-6 MV DECT is less sensitive to noise but more susceptible to beam hardening effects. By applying beam hardening correction, the 120 kV-6 MV DECT can predict the SPR more accurately than the 80-120 kV DECT. To utilize our DECT approach most effectively, high-quality reconstructed images are required.

Development the Miniaturized AMS System and Its Analysis Technique

Accelerator mass spectrometry(AMS) is the most sensitive analytical technique for measuring long-lived radionuclides, which is widely used in the fields of environment, geology, archaeology and physics. In recent years, the miniaturization of AMS device has been greatly developed in the world. In order to develop miniaturized AMS devices and their analysis technology, China institute of atomic energy has independently developed a single-stage AMS device with an acceleration voltage of 0.2 MV and a tandem AMS device with an terminal voltage of 0.3 MV, respectively. Based on the single-stage AMS device, the high efficiency transport technique and background eliminating method have been developed for 14C measurement, and realized the high sensitivity measurement of 14C. The measurement sensitivity reaches 14C/12C (atomic number ratio)=2×10–15. Using the 0.3 MV tandem AMS device, the gas stripping conditions, background eliminating and detection methods of 129I at low ion energy were systematically studied, and the high efficient transmission and high sensitive measurement methods of 129I were established, the sensitivity is 129I/127I=1×10–14. This is the first time to develop miniaturized AMS devices in China, which lays the foundation for the localization of AMS.

Synthetic polymer hydrogels as potential tissue phantoms in radiation therapy and dosimetry

The efficacy of synthetic polymers as hydrogel phantoms for radiation therapy and dosimetry has been investigated for photon and charged particle (electron, proton and alpha particle) interactions. Tissue equivalence has been studied in terms of photon mass energy-absorption coefficients, KERMA (kinetic energy released per unit mass), equivalent atomic number and energy absorption build-up factors, relative to human tissues (skin, soft tissue, cortical bone and skeletal muscle), in the energy range 0.015–15 MeV. For charged particle interactions, ratio of effective atomic number is examined for tissue-equivalence in the energy region of 10 keV–1 GeV. Well established theoretical formulations are used for computation of photon mass-energy absorption effective atomic number, electron density and KERMA. Five-parameter geometric progression (G-P) fitting approximation is used to compute the values of energy absorption build-up factors. Effective atomic number for charged particle interaction is determined using logarithmic interpolation method. Using the analytical methodology, it has been revealed that all the selected synthetic polymers have good tissue-equivalence relative to all tissue except cortical bone. In particular, polyglycolic acid (PGA) and poly-lactic-co-glycolic acid (PLGA) prove to be best substitute material for photon interactions. On the other hand, % difference between effective atomic number for charged particle relative to human tissues is found least for polyethylene glycol (PEG) demonstrating adequate tissue-equivalence. Therefore, the present study is expected to be useful to choose most appropriate phantom material for radiation therapy.

Formation of ultracold weakly bound dimers of bosonic 23Na39K

We create weakly bound bosonic $^{23}\textrm{Na}^{39}\textrm{K}$ molecules in a mixture of ultracold $^{23}\textrm{Na}$ and $^{39}\textrm{K}$. The creation is done in the vicinity of a so far undetected Feshbach resonance at about $196\,\text{G}$ which we identify in this work by atom-loss spectroscopy. We investigate the involved molecular state by performing destructive radio frequency binding energy measurements. For the constructive molecule creation we use radio frequency pulses with which we assemble up to $6000$ molecules. We analyze the molecule creation efficiency as a function of the radio frequency pulse duration and the atom number ratio between $^{23}\textrm{Na}$ and $^{39}\textrm{K}$. We find an overall optimal efficiency of $6\,\%$ referring to the $^{39}\textrm{K}$ atom number. The measured lifetime of the molecules in the bath of trapped atoms is about $0.3\,\textrm{ms}$.

Ion charge state and energy distributions of laser produced plasma from pure metals and their alloy.

A high intensity highly charged laser ion source has been studied at the Institute of Modern Physics for the last few years. In order to investigate the processes of plasma heating and expansion of laser produced plasma, the charge state and energy distributions of the ions from pure copper, silver, and copper-silver alloy, in which the atom number ratio between copper and silver is 2:3, were measured with a 90° cylindrical electrostatic ion analyzer. It was shown that the yields of highly charged copper ions from the pure copper target are higher compared with those of the alloy target. In contrast, higher yields of highly charged silver ions were obtained from the copper-silver alloy target. Moreover, the ion energy distributions were derived from the time-of-flight spectra for the ions with different ion charge states and compared between the pure metal and alloy targets.

Effect of Fe doping concentration on photocatalytic performance of CeO2 from DFT insight into analysis

A series of CeO2 based materials are analyzed using first-principles calculation. After geometry optimization, the calculated parameter of Ce32O64 is in good agreement with the experimental and theoretical results. The lattice constant of doped materials becomes increasingly smaller with the introduction of more Fe doping into the lattice owing to the small radii of impurity atoms. Other data relate to increase or decrease to some extent. As for electronic property, the energy band structure and partial density of states are explored and discussed. Due to the enhancement of the degree of hybridization between O atoms and metal atoms, there is a narrower band gap in Fe doped materials, indicating that lower energy can promote and achieve electronic transition from the valence band to the conduction band. Through the complex dielectric function composed of the real part and the imaginary part, the extinction coefficient, it is observed that they are responsive to light and electronic transition under visible light irradiation. On the other hand, we predict the photocatalytic behavior by discussing the extinction coefficient. Besides, the optical absorption spectrum and optical band gap are analyzed to further observe performance in photocatalysis. It is found that doping causes first the red shift of the absorption edge and then results in the red shift and enhancement of photocatalytic performance, which is consistent with our prediction. In addition, Eopt indicates that Fe is beneficial for the activity of CeO2. The atomic number ratio of 3:1 (Fe:Ce) shows superior behavior compared to other materials.

Experimental measurement of atomic composition in sooting luminous flame by Laser-Induced Breakdown Spectroscopy

In the present study, Laser-Induced Breakdown Spectroscopy (LIBS) was applied to the measurement of fuel-rich propane-air luminous flame in a counter-flow configuration to investigate the applicability of LIBS to measure local chemical composition in sooting field. H656nm/O777nm intensity ratio was chosen as the indicator of atomic number ratio H/O which gives direct information on equivalence ratio and is important for analyzing not only blue flame but also sooting flame. Measurement was conducted in the first place on propane-air/air counter-flow flame with the range of local equivalence ratio 0–4, in which the intensity ratio showed a good linear correlation with calculated H/O atomic number ratio as it had been observed in non-sooting conditions. LIBS technique was also applied to uniformly sooting flame supplying the same mixture at equivalence ratio of 2.2 from both nozzles to produce predefined homogeneous atomic composition. The measured intensity ratio was a good agreement with the linear relationship obtained in the propane-air/air diffusion flame experiment. Therefore, robustness of LIBS measurement of atomic/molecular composition in sooting flame was reasonably elucidated.

Breathing mode of a Bose-Einstein condensate repulsively interacting with a fermionic reservoir

We investigate the fundamental breathing mode of a small-sized elongated Bose-Einstein condensate coupled to a large Fermi sea of atoms. Our observations show a dramatic shift of the breathing frequency when the mixture undergoes phase separation at strong interspecies repulsion. We find that the maximum frequency shift in the full phase-separation limit depends essentially on the atom number ratio of the components. We interpret the experimental observations within a model that assumes an adiabatic response of the Fermi sea, or within another model that considers single fermion trajectories for a fully phase-separated mixture. These two complementary models capture the observed features over the full range of interest.

Estimation of electron density, effective atomic number and stopping power ratio using dual-layer computed tomography for radiotherapy treatment planning

PurposeAssess the accuracy for quantitative measurements of electron density relative to water (ρe/ρe,w), effective atomic number (Zeff) and stopping power ratio relative to water (SPRw) using a dual-layer computed tomography (DLCT) system. Methods and MaterialsA tissue characterization phantom was scanned using DLCT with varying scanning parameters (i.e., tube voltage, rotation time, CTDIvol, and scanning mode) and different reference materials. Then, electron density ρe/ρe,w and atomic number Zeff images were reconstructed, and their values were determined for each reference materials. Based on these two values, SPRw was calculated. Finally, the percent error (PE) against the theoretical values was calculated for reference materials. ResultsSignificant linear relationships (p < 0.001) were observed between the measured and theoretical ρe/ρe,w (r = 1.000), Zeff (r = 0.989) and SPRw (r = 1.000) values. The PE for each reference material varied from –2.0 to 1.2% (mean, <0.1%) for electron density ρe/ρe,w, from –6.4 to 8.0% (mean, –2.0%) for atomic number Zeff, and from –2.0 to 1.9% (mean, 0.3%) for stopping power ratio SPRw. The mean PE of ρe/ρe,w (<0.1%), Zeff (<–2.5%) and SPRw (<0.4%) was verified across the variation of scanning parameters (p > 0.85). ConclusionsDLCT provides a reasonable accuracy in the measurements of ρe/ρe,w, Zeff and SPRw, and could enhance radiotherapy treatment planning and the subsequent outcomes.

Radiological properties of plastics and TLD materials its application in radiation dosimetry

In the current study, we evaluated the tissue equivalency of nine different commonly used thermoluminescence compounds and six plastic materials over the photon energy range of 15 KeV to 20 MeV. Our result confirmed that the ratio of number of electrons per gram, electron density of the entire TLD compounds and plastic materials to ICRU-44 soft tissue was lesser than unity, except in the case of polypropylene plastics. The effective atomic number ratio of all the plastic materials was also <1 excluding Poly-vinyl-chloride, and for TLD lithium borate material, it was <1 others which showed the deviation with respect to photon energy. Mass attenuation coefficient (µ/ϼ), mass absorption coefficient (µen/ρ) was calculated and the results are discussed in this paper.

The Property of Phonon Gap in Iron-Based Superconductors FeSe, LiFeAs and SrFeAsF

First-principles calculations are performed for iron-based superconductors FeSe, LiFeAs and SrFeAsF, and the reasons of generation and loss of the phonon gaps in them are analyzed by analogy with electronic energy band theory. In iron-based superconductors FeSe and LiFeAs, lattice vibrations are affected by so strong changes in the periodic potential that the phonon spectra open a full gap. After considering electron–spin interactions, the enhancement of the periodic potential results in a broadening of the gap. From binary FeSe to ternary LiFeAs to quaternary SrFeAsF, the full phonon gap undergoes the process from decrease to disappearance, which is closely related to the frequencies overlapping of different atoms by vibrations. The fewer the material components and the larger the atomic number ratio, the more possible the production of the full phonon gap or the appearance of wider gap. In addition, the phonon gaps of FeSe and LiFeAs locate around the frequency of \(10^{12}\) Hz, whose filtering properties for elastic waves are hopefully to be applied in quantum acoustics.

A phantom-based forward projection approach in support of model-based iterative reconstructions for HAADF-STEM tomography

We introduce a forward model for the computation of high angle annular dark field (HAADF) images of nano-crystalline spherical particles and apply it to image simulations for assemblies of nano-spheres of Al, Cu, and Au with a range of sizes, as well as an artificial bi-sphere, consisting of solid hemispheres of Al and Cu or Al and Au. Comparison of computed intensity profiles with experimental observations on Al spheres at different microscope accelerating voltages provides confidence in the forward model. Simulated tomographic tilt series for both HAADF and bright field (BF) images are then used to illustrate that the model-based iterative reconstruction (MBIR) approach is capable of reconstructing sphere configurations of mixed atomic number, with the correct relative reconstructed intensity ratio proportional to the square of the atomic number ratio.

Evaluation of neutron economical effect of new cladding materials in light water reactors

The present paper aims to contribute from a neutronic aspect to activities for new cladding material development for light water reactors (LWRs) that can reduce the risk of hydrogen gas explosion. Iron (Fe), nickel (Ni), titanium (Ti), niobium (Nb) and vanadium (V) are selected as possible component elements to cover a variety of new cladding materials for LWRs. The effect of larger thermal absorption cross sections of these elements than those of zirconium (Zr), together with those of silicon carbide (SiC), on the neutron economy in LWRs is evaluated by performing pin cell burnup calculations for a conventional pressurized water reactor (PWR), a low-moderation high-burnup LWR (LM-LWR) and a high-moderation high-burnup LWR (HM-LWR). As can be anticipated from the thermal cross sections, SiC has excellent neutron economy. The materials other than SiC largely decrease discharge burnup for all three types of LWRs in comparison with Zircaloy-4. Among such elements of larger thermal absorption cross section, Nb has neutron economical advantage over the other materials except SiC in softer neutron spectrum reactors such as HM-LWR in which the atomic number ratio of hydrogen to heavy metal is 6. In conventional LWRs, stainless steel of low Ni contents has the neutron economic advantage as well as Nb for cladding material. The results of the calculations are summarized for the purpose to provide reference data for new cladding material development studies, in terms of the relation between fuel enrichment and cladding thickness from the viewpoint to achieve the same discharge burnup as the Zircaloy cladding.