Cross Section Database Research Articles

Collision Cross Section Prediction Based on Machine Learning.

Ion mobility-mass spectrometry (IM-MS) is a powerful separation technique providing an additional dimension of separation to support the enhanced separation and characterization of complex components from the tissue metabolome and medicinal herbs. The integration of machine learning (ML) with IM-MS can overcome the barrier to the lack of reference standards, promoting the creation of a large number of proprietary collision cross section (CCS) databases, which help to achieve the rapid, comprehensive, and accurate characterization of the contained chemical components. In this review, advances in CCS prediction using ML in the past 2 decades are summarized. The advantages of ion mobility-mass spectrometers and the commercially available ion mobility technologies with different principles (e.g., time dispersive, confinement and selective release, and space dispersive) are introduced and compared. The general procedures involved in CCS prediction based on ML (acquisition and optimization of the independent and dependent variables, model construction and evaluation, etc.) are highlighted. In addition, quantum chemistry, molecular dynamics, and CCS theoretical calculations are also described. Finally, the applications of CCS prediction in metabolomics, natural products, foods, and the other research fields are reflected.

Benchmark of Neutron Thermalization in Graphite Using a Pulsed Slowing-Down-Time Experiment

A benchmark has been developed using a pulsed slowing-down-time experiment to isolate the thermalization process in graphite. The experiment was conducted at the Oak Ridge Electron Linear Accelerator facility at Oak Ridge National Laboratory, and it measured the time spectrum of neutrons leaking from a graphite pile during slowing down and thermalization within graphite. Simulations of the benchmark experiment were performed using the MCNP6.1 Monte Carlo code and the ENDF/B-VII.1 and ENDF/B-VIII.0 cross-section databases. The benchmark provides a time spectrum (i.e., time-dependent counts in a detector) that allows for validation of the graphite thermal scattering libraries (TSLs). The impact on the simulations using a suite of graphite TSLs was compared with the experimental results. Given the density of nuclear graphite, the TSL corresponding to graphite with 30% porosity, as implemented in ENDF/B-VIII.0, was found to most accurately represent the measured time spectrum corresponding to the thermal energy range with an average deviation of ±1.7%.

A Novel Hierarchical Extreme Machine-Learning-Based Approach for Linear Attenuation Coefficient Forecasting.

The development of reinforced polymer composite materials has had a significant influence on the challenging problem of shielding against high-energy photons, particularly X-rays and γ-rays in industrial and healthcare facilities. Heavy materials' shielding characteristics hold a lot of potential for bolstering concrete chunks. The mass attenuation coefficient is the main physical factor that is utilized to measure the narrow beam γ-ray attenuation of various combinations of magnetite and mineral powders with concrete. Data-driven machine learning approaches can be investigated to assess the gamma-ray shielding behavior of composites as an alternative to theoretical calculations, which are often time- and resource-intensive during workbench testing. We developed a dataset using magnetite and seventeen mineral powder combinations at different densities and water/cement ratios, exposed to photon energy ranging from 1 to 1006 kiloelectronvolt (KeV). The National Institute of Standards and Technology (NIST) photon cross-section database and software methodology (XCOM) was used to compute the concrete's γ-ray shielding characteristics (LAC). The XCOM-calculated LACs and seventeen mineral powders were exploited using a range of machine learning (ML) regressors. The goal was to investigate whether the available dataset and XCOM-simulated LAC can be replicated using ML techniques in a data-driven approach. The minimum absolute error (MAE), root mean square error (RMSE), and R2score were employed to assess the performance of our proposed ML models, specifically a support vector machine (SVM), 1d-convolutional neural network (CNN), multi-Layer perceptrons (MLP), linear regressor, decision tree, hierarchical extreme machine learning (HELM), extreme learning machine (ELM), and random forest networks. Comparative results showed that our proposed HELM architecture outperformed state-of-the-art SVM, decision tree, polynomial regressor, random forest, MLP, CNN, and conventional ELM models. Stepwise regression and correlation analysis were further used to evaluate the forecasting capability of ML techniques compared to the benchmark XCOM approach. According to the statistical analysis, the HELM model showed strong consistency between XCOM and predicted LAC values. Additionally, the HELM model performed better in terms of accuracy than the other models used in this study, yielding the highest R2score and the lowest MAE and RMSE.

ENDF/B-VIII.0-based fast neutron removal cross sections database in Z = 1 to 92 generated via multi-layered spherical geometry

A fast neutron mass removal cross sections (ΣR/ρ) database covering the elemental range of Z = 1 to 92 is generated for source neutron energy distributions based on 241Am–Be, 252Cf, and 235U. Monte Carlo simulations using ENDF/B-VIII.0 nuclear data were performed with the fast neutron removal theory's ideal spherical representation. The ENDF/B-VIII.0-based ΣR/ρ′s derived were compared with values from the Oak Ridge National Laboratory's Lid Tank Shielding Facility (LTSF) experiments, values from software Phy-X/PSD and MRCsC, values obtained by an empirical model in Zoller, and values derived using the older ENDF/B-VII.0 nuclear data library. Subsequently, the generated ΣR/ρ′s were evaluated for convergence under varying moderator thickness. Results indicate that the ΣR/ρ quantity for fission and (alpha, n) spectra is universal, with slight deviations for low Z elements. The ΣR/ρ values generated from ENDF/B-VIII.0 agreed with LTSF experiments with an average relative deviation of 8.58%. Moreover, using ENDF/B-VIII.0-based ΣR/ρ′s, the derived fast neutron effective removal cross sections (ΣR's) for several light compounds and dry concrete have better agreement on average with LTSF experiments compared with values derived from the available ΣR/ρ′s in the literature. Significant differences were found for ΣR/ρ′s that were generated with ENDF/B-VIII.0 as compared with the superseded ENDF/B-VII.0. Furthermore, ENDF/B-generated ΣR/ρ′s through spherical model showed the expected convergence towards singular values at moderator thicknesses practical for fast neutron removal theory applications. Owing to the relatively high unavoidable uncertainties of the LTSF experimental ΣR/ρ′s, the ENDF/B-VIII.0-based ΣR/ρ′s present a new and potentially favorable database in ΣR general calculations for homogeneous multi-element materials for point-kernel shielding applications.

Absorption coefficients, frequency shifts and absorption cross sections measurements versus pressure at room temperature, for hydro-chlorofluorocarbon HCFC-141b using a tunable CW CO2 laser

Infrared (IR) absorption in the spectral ranges of 10P (934.92-952.89 cm−1), 10R (969.15-982.13 cm−1), 9P (1037.43-055.62cm−1) and 9R (1071.88-084.62 cm−1) in Freon of HCFC-141b (CH3CCl2F) was studied by measuring the laser output power at each emitted spectral line versus pressure. A tunable continuous wave (CW) CO2 laser with an absorber cell located outside the laser cavity were used and the maximum output power of about 2.88 W on the line 10P(22) was achieved.The absorption coefficients of HCFC-141b for all emitted spectral lines were determined versus the gas pressure between 0.01-300 mbar, 0.01- 500 mbar, 0.01-450 mbar and 0.01-80 mbar for 10P, 10R, 9P and 9R branches respectively.The frequency shifts of the absorption lines of HCFC-141b in relative to the central frequencies of laser lines were calculated vs the pressure on the basis of the absorption coefficients.The chosen spectral ranges were selected according to IR spectrum of the studied gas given by HITRAN cross section database. So the absorption was achieved for HCFC-141b at the spectral lines of 10P, 10R, 9P and 9R branches emitted by a tunable CW CO2 laser.The absorption cross sections of HCFC-141b determined in this work were compared with the relevant data given by HITRAN cross section database and with the available measured results of reported work by others. The agreement was almost reasonable for all lines.

The Effect of the "Triple-Layer Medical Security" Policy on the Vulnerability as Expected Poverty of Rural Households: Evidence from Yunnan Province, China.

China launched the “critical battle against poverty” nationwide in 2012. As its main battlefield, Yunnan province promulgated the “triple medical security” (TMS) policy in 2017. This study, based on the pooled cross-section database of 2015–2020 of registered poor households in Yunnan province, employed the logit model to examine the effect of TMS on the vulnerability as expected poverty (VEP) of these households. It found that increasing the reimbursement rates for overall medical expenses and inpatient expenses and decreasing the proportion of out-of-pocket medical payment to income reduced the VEP; increases in the number of sick people in the family increased its VEP, and although the increase in the reimbursement rate for overall medical expenses or for inpatient expenses partially offset the VEP caused by the increase in the number of chronically ill people in the family, the VEP caused by the increase in the number of critically ill people would increase in the short term with the increase in the reimbursement rate for overall medical expenses or for inpatient expenses. The findings help improve policies concerning the medical security and health of the rural poor population, providing theoretical reference and practical guidance for future research.

Comparability of Steroid Collision Cross Sections Using Three Different IM-HRMS Technologies: An Interplatform Study

Steroids play key roles in various biological processes and are characterized by many isomeric variants, which makes their unambiguous identification challenging. Ion mobility-mass spectrometry (IM-MS) has been proposed as a suitable platform for this application, particularly using collision cross section (CCS) databases obtained from different commercial IM-MS instruments. CCS is seen as an ideal additional identification parameter for steroids as long-term repeatability and interlaboratory reproducibility of this measurand are excellent and matrix effects are negligible. While excellent results were demonstrated for individual IM-MS technologies, a systematic comparison of CCS derived from all major commercial IM-MS technologies has not been performed. To address this gap, a comprehensive interlaboratory comparison of 142 CCS values derived from drift tube (DTIM-MS), traveling wave (TWIM-MS), and trapped ion mobility (TIM-MS) platforms using a set of 87 steroids was undertaken. Besides delivering three instrument-specific CCS databases, systematic comparisons revealed excellent interlaboratory performance for 95% of the ions with CCS biases within ±1% for TIM-MS and within ±2% for TWIM-MS with respect to DTIM-MS values. However, a small fraction of ions (<1.5%) showed larger biases of up to 7% indicating that differences in the ion conformation sampled on different instrument types need to be further investigated. Systematic differences between CCS derived from different IM-MS analyzers and implications on the applicability for nontargeted analysis are critically discussed. To the best of our knowledge, this is the most comprehensive interlaboratory study comparing CCS from three different IM-MS technologies for analysis of steroids and small molecules in general.

Applications of ion mobility-mass spectrometry in the chemical analysis in traditional Chinese medicines

离子淌度质谱(IM-MS)是一种将离子淌度分离与质谱分析相结合的新型分析技术。IM-MS的主要优势不仅是在质谱检测前提供了基于气相离子形状、大小、电荷数等因素的多一维分离,而且能够提供碰撞截面积、漂移时间等质谱信息进而辅助化合物鉴定。近年来,随着IM-MS技术的不断发展,该技术在中药化学成分分析中受到越来越多的关注。首先,IM-MS已成功应用于改善中药复杂成分尤其是同分异构体或等量异位素等成分的分离;其次,IM-MS可通过多重碎裂模式辅助高质量中药小分子质谱信息的获取;此外,IM-MS提供的高维质谱数据信息还可促进中药复杂体系多成分的整合分析。该文在对IM-MS分类和基本原理进行概述的基础上,从分离能力及分离策略、多重碎裂模式、多维质谱数据处理策略3个方面,重点综述了IM-MS在中药化学成分分析中的应用,以期为IM-MS在中药化学成分研究提供参考。

ExoMol photodissociation cross-sections – I. HCl and HF

ABSTRACT Photon initiated chemistry, i.e. the interaction of light with chemical species, is a key factor in the evolution of the atmosphere of exoplanets. For planets orbiting stars in UV-rich environments, photodissociation induced by high-energy photons dominates the atmosphere composition and dynamics. The rate of photodissociation can be highly dependent on atmospheric temperature, as increased temperature leads to increased population of vibrational excited states and the consequent lowering of the photodissociation threshold. This paper inaugurates a new series of papers presenting computed temperature-dependent photodissociation cross-sections with rates generated for different stellar fields. Cross-sections calculations are performed by solving the time-independent Schrödinger equation for each electronic state involved in the process. Here, photodissociation cross-sections for hydrogen chloride and hydrogen fluoride are computed for a grid of 34 temperatures between 0 and 10 000 K. Use of different radiation fields shows that for the Sun and cooler stars the photodissociation rate can increase exponentially for molecular temperatures above 1000 K; conversely the photodissociation rates in UV rich fields instead are almost insensitive to the temperature of the molecule. Furthermore, these rates show extreme sensitivity to the radiation model used for cool stars, suggesting that further work on these may be required. The provision of an ExoMol data base of cross-sections is discussed.

Monte Carlo simulation of the mass attenuation coefficient and effective atomic number of the Eremurus-Rhizophora ssp. particleboard phantom at the mammography energy range

The earlier investigations proved the potential of the Rhizophora spp. as a phantom material. In this study, the mass attenuation coefficients and empirical and theoretical effective atomic numbers of Eremurus-Rhizophora spp. particleboards in three particle sizes and two adhesive treatment levels were evaluated in 16.63–60 keV photon energy range, using theoretical (XCOM: NIST Photon Cross Sections Database Code), simulation (MCNPX: Monte Carlo N-Particle eXtended Code), and experimental methods. The findings of this study were discussed in terms of the various calculating approaches, and also comparing them with raw wood, binderless particleboard, water, and different breast tissues. The mass attenuation coefficients of Eremurus-Rhizophora spp. samples were seriously agreed with young age breast tissue in three determination methods. Although the empirical effective atomic number (Zeff) is independent of photon energy and the theoretical Zeff is affected by it, the empirical and theoretical effective atomic numbers of the Eremurus-Rhizophora spp. particleboards are in good agreement in the mammography photon energy range. Moreover, the results of this study showed that the radiation features of Rhizophora spp. particleboard can be significantly improved by adding the Eremurus spp. root. The results prove the validity of the MCNP method as an alternative to the XCOM and experimental methods for evaluating the attenuation features and effective atomic numbers of the bio-composites.

Neutron Direction Distribution in D-T Plasma

With the development of magnetic confinement fusion (MCF), it has become feasible for fusion energy to solve the future energy crisis. High-energy neutrons are produced during the fusion reaction. Neutron shielding and the tritium breeding ratio in MCF require a neutron source of high precision. In traditional methods, the neutron source is supposed to be isotropic. However, the double-differential cross sections for nuclear fusion given in the ENDF/B-VI database make it possible to calculate the neutron direction distribution in deuterium-tritium (D-T) plasma. In this study, a Maxwellian reactivity rate database is obtained by extracting double-differential cross-section data from the ENDF/B-VI database and then revising it. Monte Carlo and discrete ordinate methods are used to simulate transportation and fusion in D-T plasma and obtain the angular distribution of the neutron generation rate. The results of a preliminary numerical simulation in a simple model tell us that the difference between anisotropy and isotropy can reach an average of 4.6%. A temperature-corrected double-differential cross-section database and a numerical simulation method are developed to calculate the angular distribution of the neutron generation rate.

Projectile electron loss, excitation and de-excitation cross section database in a collision between two hydrogen atoms in the impact energy range between 50 keV–5.0 MeV, Part I: Target is in ground state

We present projectile electron loss, excitation, and de-excitation cross-sections database for H(nl)+H(1s) collision system. A four-body classical trajectory Monte Carlo (CTMC) and a quasi-classical trajectory Monte Carlo (QCTMC) methods were employed in the projectile energy range between 50 keV to 5.0 MeV.

State-selective electron capture cross sections in collision between fully striped ions and ground state hydrogen atom—Classical treatment of the collision

We present a state-selective electron capture cross sections database from the ground state hydrogen atom. A standard three-body classical trajectory Monte Carlo (CTMC) and quasi-classical trajectory Monte Carlo (QCTMC) models were employed for impact energies between 10 and 200 keV/amu. The projectile ions are H+, He2+, Li3+, Be4+, B5+, C6+, N7+, and O8+. The cross sections are tabulated for each value of the final quantum numbers n, l, m, summed over m for the given n and l and over l and m for the given n. The maximum quantum number nmax is set to 4 for H+, He2+ and Li3+, as well as to 5 for Be4+, B5+, C6+, N7+ and O8+, respectively.

Cross sections for valence-shell excitations of H2O in the 9.85–12.15-eV energy-loss range studied by high-energy inelastic electron scattering

The recent measurement of the generalized oscillator strengths (GOSs) for $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{A}\phantom{\rule{0.28em}{0ex}}^{1}B_{1}$ and $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{B}\phantom{\rule{0.28em}{0ex}}^{1}A_{1}$ of ${\mathrm{H}}_{2}\mathrm{O}$ exhibits the apparent deviations from the first Born approximation calculations in the large squared momentum transfer region [W. Q. Xu et al., Phys. Rev. A 103, 032808 (2021)]. Here a simplified theoretical model was proposed to calculate the GOSs of the two excitations at large momentum transfer within the second Born approximation. The accord of the experimental GOSs and the theoretical ones is improved, but the differences still exist. In addition, the GOSs and the integral cross sections for the higher excitations of ${\mathrm{H}}_{2}\mathrm{O}$ in 9.85--12.15 eV are presented, which could be used to complete the database of electron-impact excitation cross sections of ${\mathrm{H}}_{2}\mathrm{O}$ and be beneficial for modeling interaction processes between electrons and ${\mathrm{H}}_{2}\mathrm{O}$ in the earth's atmosphere, plasmas, radiation physics, biology, etc.

Upgrade of recommended nuclear cross section data base for production of therapeutic radionuclides

The IAEA Nuclear Data Section has coordinated several actions to setup and improve a database for recommended cross sections and nuclear decay data for various charged-particle reactions that can be used for medical radionuclide production. Some of the earlier evaluations did not provide uncertainties for the recommended cross sections. Updated evaluations with uncertainty quantification for 25 reactions relevant for production of 67Cu, 103Pd, 102mgRh, 114mIn, 125I, 169Yb, 177gLu, 186Re, 192Ir and 210,211At therapeutic radioisotopes are presented. Recommended cross-section data and their uncertainties for production of therapeutic radionuclides are available on the Web page of the IAEA Nuclear Data Section at https://nds.iaea.org/radionuclides and also at the IAEA medical portal https://nds.iaea.org/medportal.

Endf/B-Viii-Based Fast Neutron Removal Cross Sections Database in Z = 1 to 92 Generated Via Multi-Layered Spherical Geometry

Endf/B-Viii-Based Fast Neutron Removal Cross Sections Database in Z = 1 to 92 Generated Via Multi-Layered Spherical Geometry

Collisions of Nucleons with Atoms: Calculated Cross Sections and Monte Carlo Simulation

After a summary description of the theory of elastic collisions of nucleons with atoms, we present the calculation of a generic database of differential and integrated cross sections for the simulation of multiple elastic collisions of protons and neutrons with kinetic energies larger than 100 keV. The relativistic plane-wave Born approximation, with binding and Coulomb-deflection corrections, has been used to calculate a database of proton-impact ionization of K-shell and L-, M-, and N-subshells of neutral atoms These databases cover the whole energy range of interest for all the elements in the periodic system, from hydrogen to einsteinium (Z = 1–99); they are provided as part of the penh distribution package. The Monte Carlo code system penh for the simulation of coupled electron-photon-proton transport is extended to account for the effect of the transport of neutrons (released in proton-induced nuclear reactions) in calculations of dose distributions from proton beams. A simplified description of neutron transport, in which neutron-induced nuclear reactions are described as a fractionally absorbing process, is shown to give simulated depth-dose distributions in good agreement with those generated by the Geant4 code. The proton-impact ionization database, combined with the description of atomic relaxation data and electron transport in penelope, allows the simulation of proton-induced x-ray emission spectra from targets with complex geometries.

Technical note: MC-GPU breast dosimetry validations with other Monte Carlo codes and phase space file implementation.

To validate the MC-GPU Monte Carlo (MC) code for dosimetric studies in X-ray breast imaging modalities:mammography, digital breast tomosynthesis, contrast enhanced digital mammography, and breast-CT. Moreover, to implement and validate a phase space file generation routine. The MC-GPU code (v.1.5 DBT) was modified in order to generate phase space files and to be compatible with PENELOPE v.2018 derived cross-section database. Simulations were performed with homogeneous and anthropomorphic breast phantoms for different breast imaging techniques. The glandular dose was computed for each case and compared with results from the PENELOPE (v.2014) + penEasy (v.2015) and egs brachy (EGSnrc) MC codes. Afterward, several phase space files were generated with MC-GPU and the scored photon spectra were compared between the codes. The phase space files generated in MC-GPU were used in PENELOPE and EGSnrc to calculate the glandular dose, and compared with the original dose scored in MC-GPU. MC-GPU showed good agreement with the other codes when calculating the glandular dose distribution for mammography, mean glandular dose for digital breast tomosynthesis, and normalized glandular dose for breast-CT. The latter case showed average/maximum relative differences of 2.3%/27%, respectively, compared to other literature works, with the larger differences observed at low energies (around 10 keV). The recorded photon spectra entering a voxel were similar (within statistical uncertainties) between the three MC codes. Finally, the reconstructed glandular dose in a voxel from a phase space file differs by less than 0.65%, with an average of 0.18%-0.22% between the different MC codes, agreement within approximately statistical uncertainties. In some scenarios, the simulations performed in MC-GPU were from 20 up to 40 times faster than those performed by PENELOPE. The results indicate that MC-GPU code is suitable for breast dosimetric studies for different X-ray breast imaging modalities, with the advantage of a high performance derived from GPUs. The phase space file implementation was validated and is compatible with the IAEA standard, allowing multiscale MC simulations with a combination of CPU and GPUcodes.

Experimental cross-sections for proton induced reactions on natural molybdenum

The experimental cross-sections of the natMo(p,xn)93m+g,94g,95m,95g,96m+gTc, 100Mo(p,x)99Mo and 100Mo(p,2n)99mTc nuclear reactions were measured up to 18.3MeV, by the stacked-foil activation technique at the superconducting linear accelerator of the Institute of Modern Physics, Chinese Academy of Sciences. And the proton beam current was monitored by the independent natCu(p,x)65Zn and natTi(p,x)48V reactions. The experimental results were compared with the literature data taken from EXFOR database, evaluation data of the charged-particle cross section database and theoretical values by using TALYS-1.95 code with six level density models. The obtained results for most of the radionuclides show good agreement with the available literature data. Besides, the theoretical calculations predicted by the TALYS-1.95 code demonstrate similar trends with experimental data. Although in some cases, cross-sections results are sensitive to the nuclear level densities. Evaluated nuclear values of the charged-particle cross section database correspond well with our measurements for 96m+g,99mTcand 99Mo.

γ -ray emission in α -particle interactions with C, Mg, Si, and Fe at Eα=50–90 MeV

Nuclear deexcitation lines are regularly observed in the $\ensuremath{\gamma}$-ray emission spectra of strong solar flares. The most prominent lines are produced by interactions of protons and $\ensuremath{\alpha}$ particles, accelerated up to hundreds of MeV, with abundant nuclei of the solar atmosphere. Analysis and interpretation of these lines, which carry valuable information on the solar flare properties, need cross-section data for the $\ensuremath{\gamma}$-ray line emission in these interactions for a wide particle energy range. To this purpose, we measured the $\ensuremath{\gamma}$-ray emission in interactions of $\ensuremath{\alpha}$-particle beams of ${E}_{\ensuremath{\alpha}}=50\text{--}90$ MeV with target foils of C, Mg, Si, and Fe at the center for proton therapy of the Helmholtz-Zentrum Berlin. Setups of three high-purity Ge detectors and one $\mathrm{La}{\mathrm{Br}}_{3}$:Ce detector have been employed to detect the $\ensuremath{\gamma}$ rays in two experiment campaigns. Relatively large distances of the detectors from the target and pulsed beams with sub-ns-wide pulses allowed the separation of beam-induced prompt $\ensuremath{\gamma}$-ray emission from the targets from other $\ensuremath{\gamma}$ rays and neutron-induced background. $\ensuremath{\gamma}$-ray production cross sections for about 60 deexcitation lines from excited target nuclei or reaction products have been determined. For the strongest deexcitation lines from the major target isotopes, $^{12}\mathrm{C}$, $^{24}\mathrm{Mg}$, $^{28}\mathrm{Si}$, $^{56}\mathrm{Fe}$, there are now measured cross-section data from reaction threshold to ${E}_{\ensuremath{\alpha}}=90$ MeV that can be directly used for astrophysical applications like solar flares. Comparison of the results with a cross-section compilation for strong $\ensuremath{\gamma}$-ray lines in solar flare emissions and the predictions of the talys nuclear reaction code were done. They underline the importance of cross-section determinations at accelerator laboratories for the establishment of an accurate cross-section data base in a wide projectile energy range.