Cross-sectional Resonance Research Articles

Simulation Chemical Reactions in Faddeev Approach

The main features of resonance in scattering are described and resonances are determined on the basis of the theory of collisions in a two-body system, as well as resonances emerging as a result of collisions in a few-body system. Regularities in the emergence of such resonances and their characteristics are analyzed. The results of calculations of these resonant processes occurring during collisions of electrons with diatomic molecules, made on the basis of the quantum theory of scattering in a few body system, based on Faddeev-Yakubovsky equations are discussed. The results of calculations of the resonant cross sections of electron and atom collisions with molecules are presented. Obtained results are compared with the available experimental data and with the results of calculations based on other approximations. In addition some biological applications (e.g. properties biopolymer molecules) are presented.

Analysis of the Influence of Energy Group Structure on Iron Shielding Calculation

The energy group structure of a multi-group cross section library matched with a deterministic method has a significant influence on shielding calculation. The complex resonance cross section of Fe-56 has a significant influence on accuracy with different energy group structures when processing multi-group cross section data. In this study, in order to more accurately test the influence of the iron resonance phenomenon on shielding calculations, this group structure is modified by the 199-group with 69 points interpolated into its group boundaries at an energy range from 1.1 keV to 3.1164 MeV. The new 269-group library is then tested with selected SINBAD iron sphere benchmarks and compared with the results of 199-group, 299-group, and 172-group libraries and measurements. Upon analysis, it is shown that the resonance of Fe-56 has a great influence on the accuracy of the calculated leakage. Further, it is noted that the finer the energy group division, the greater the calculated leakage fluctuation, and the deeper the neutron passes through the iron sphere, the larger the calculated leakage fluctuation. This study and its leakage results may provide a good reference for the development of new multi-group structures for present and future shielding design.

Neutron skin thickness of 116,118,120,122,124Sn determined from reaction cross sections of proton scattering

Background:The cross sections of the isovector spin-dipole resonances (SDR) in the Sb isotopes have been measured. Within the model used, the neutron-skin thicknesses rskin(exp) deduced 0.12±0.06 fm for 116Sn, 0.13±0.06 fm for 118Sn, 0.18±0.07 fm for 120Sn, 0.22±0.07 fm for 122Sn, 0.19±0.07 fm for 124Sn. We tested the chiral (Kyushu) g-matrix folding model for 12C+12C scattering, and found that the Kyushu g-matrix folding model is reliable for reaction cross sections σR in 30˜<Ein˜<100MeV and 250˜<Ein˜<400MeV. We determine neutron skin thickness rskin(exp), using measured σR of 4He+116,120,224Sn scattering. The results are rskin(exp)=0.242±0.140 fm for 116Sn, rskin(exp)=0.377±0.140 fm for 120Sn, rskin(exp)=0.180±0.142 fm for 124Sn. The σR are available for proton scattering on 116,118,120,122,124Sn with high accuracy of 2∼3% as a function of incident energy Ein. Purpose:Our aim is to determine rskin(exp) for 116,118,120,122,124Sn with small errors by using the Kyushu g-matrix folding model. Methods:Our model is the Kyushu g-matrix folding model with the densities scaled from the D1S-GHFB+AMP neutron density, where D1S-GHFB+AMP stands for Gogny-D1S HFB (D1S-GHFB) with the angular momentum projection (AMP). Results:The proton radii of D1S-GHFB+AMP agree with those calculated with the isotope shift method based on the electron scattering. We then scale the D1S-GHFB+AMP neutron densities so as to reproduce the σR(exp). In 30˜<Ein˜<65MeV, we determine rskin(exp) from measured σR. The values are rskin(exp)=0.118±0.021 fm for 116Sn, 0.112±0.021 fm for 118Sn, 0.124±0.021 fm for 120Sn, 0.156±0.022 fm for 124Sn. As for 122Sn, the skin value in 30˜<Ein˜<50MeV is 0.122±0.024 fm. Conclusions:Our results are consistent with the previous values.

Monte Carlo model for ion mobility and diffusion for characteristic electric fields in nanodosimetry

The quantification of the effects of space radiation for manned spaceflight can be approximated by nanodosimetric measurements. For the development of nanodosimetric detectors, a Monte Carlo model for ion mobility and diffusion for characteristic electric fields is presented.This model can be used to describe the interactions of ions in their parent gas based solely on commonly known input parameters, such as the ionization potential, kinetic diameter, molar mass, and polarizability of the gas. A model for approximating the resonant charge exchange cross section has been proposed, requiring only the ionization energy and mass of the parent gas as input parameters. The method proposed in this work was tested against experimental drift velocity data for a wide range of gases (helium, neon, nitrogen, argon, krypton, carbon monoxide, carbon dioxide, oxygen, propane). The transverse diffusion coefficients were compared to experimental values for helium, nitrogen, neon, argon, and propane gas.With the Monte Carlo code and resonant charge exchange cross section approximation model presented in this work, it is now possible to calculate an estimate of the drift velocities, transverse diffusion, and thus the ion mobility of ions in their parent gas. This is essential for further nanodosimetric detector development, as those parameters are often not well known for the gas mixtures used in nanodosimetry.

Statistical Uncertainty Quantification of Probability Tables for Unresolved Resonance Cross Sections

The probability table method is an important method to treat the self-shielding effect in the unresolved resonance region. A probability table is generated by using many “ladders” that represent pseudo resonance structures. This study developed a quantification method of the statistical uncertainty of a probability table. The product of the probability table and average cross section in each probability bin was considered as the target of the statistical uncertainty of the probability table. The central limit theorem (CLT), bootstrap method, and jackknife method were adopted to calculate the statistical uncertainty. The statistical uncertainties calculated using these methods were compared with the reference results. The calculation results showed that the statistical uncertainties obtained by CLT were similar to those of the other methods. Because the CLT calculation time was faster than that of the other methods, CLT was deemed as the best method for calculating the statistical uncertainty of the probability table. The statistical uncertainty quantification of the probability table developed in this study was implemented in nuclear data processing code FRENDY version 2. FRENDY version 2 can generate a probability table using the tolerance of the statistical uncertainty of the probability table.

Analyses of on-the-fly generation of spectral superhomogenization factors for multigroup whole core calculation employing pin-wise slowing-down solutions

On-the-fly(OTF) generation of Spectral Superhomogenization(SSPH) factors is analyzed in the multigroup(MG) whole core calculation employing pin-wise continuous energy(CE) slowing-down solutions. The motivation for the work is to avoid the huge computing time required for the generation of a parametrized SSPH factor library(PSSL) which is used to resolve the angular dependency of MG resonance cross sections, and also to exploit the advantage of flexible choice of a MG structure by using CE slowing-down solutions. Two pin-wise CE slowing-down methods, the equivalent Dancoff cell method and the shadowing effect correction method, are evaluated with the OTF SSPH method. The effectiveness of the OTF SSPH method is examined for various simplified and realistic core problems with various MG structures. It is demonstrated that the computing time overhead of this method is negligible whereas the solution accuracy is considerably enhanced.

Rayleigh scattering from hydrogen atoms including resonances and high photon energies

The nonrelativistic cross section from Rayleigh scattering by hydrogen atoms in the ground state was calculated over a wide range of photon energies (&lt;0.8 keV). Evaluations were performed in terms of the real and imaginary components of the atomic polarizability. The sum over intermediate states that characterizes this second-order radiative process was performed using exact analytic expressions for oscillator strengths of bound and continuum states. Damping terms associated with the finite lifetimes of excited states and their splitting into two fine-structure levels (p1/2 and p3/2) are taken into account in resonance cross sections. Fitting formulas required for cross-section evaluation are presented for incident photon energy (i) redward of the first resonance (Lyman-α1/2), (ii) in the spectral region corresponding to resonances (for an arbitrary number of them), and (iii) above the ionization threshold.

Feasibility of deterministic self-shielding models for Molten Salt Fast Reactor analysis using DRAGON5 code with ENDF/B-VIII.0 data library

Due to its complex geometry and neutron spectrum, the GenIV Molten Salt Fast Reactor was largely studied using the “one-step” calculation scheme, based on the Monte Carlo method. However, for whole-core simulations, this method requires a long computing time to get accurate results. A deterministic “two-step” calculation scheme must be considered and applied to minimize the computational resources. In general, the first step is to obtain multi-group homogenized and condensed cross-sections, while the second step is using those multi-group cross-sections to perform the whole-core simulations. The treatment of the resonance cross-section behavior is one of the biggest problems that affect the accuracy of the multi-group cross-section and handling such a problem is required before proceeding to the second step calculation. So, it is essential to choose a proper and accurate self-shielding model. In this paper, the different self-shielding models are performed with the deterministic code DRAGON5, using ENDF/B-VIII.0 with various energy group libraries on which the self-shielding model is implemented. The infinite multiplication factor Kinf and the radial distribution of absorption, nu-fission, and capture rates were calculated at the low temperature to demonstrate the rim effect. To guarantee accurate predictions of the results revealed by the self-shielding models, the temperature was increased in the range [893 K–1123 K], and a series of different parameters, such as Kinf, average percent error (AVG), root mean square (RMS), and mean relative error (MRE), were calculated as functions of temperature. The calculation’s accuracy is determined by comparing the results with the stochastic transport code OpenMC. It was found that the deterministic transport code DRAGON5 can accurately treat the effect of self-shielding behavior in the MSFR; hence, DRAGON5 code can be utilized as a tool to generate the multi-group homogenized cross-sections of MSFR for whole-core calculations.

The effect of generation of narrow ultrarelativistic beams of positrons (electrons) in the process of resonant photoproduction of pairs on nuclei in a strong electromagnetic field

The generation of narrow beams of high-energy positrons (electrons) in the process of resonant photogeneration of ultrarelativistic electron–positron pairs by high-energy gamma quanta in the field of the nucleus and a strong electromagnetic wave is theoretically predicted. It is shown that if the energy of the initial gamma quanta significantly exceeds the characteristic energy of the process, then ultrarelativistic positrons (electrons) are emitted with energies very close to the energy of gamma quanta. Moreover, the resonant differential cross-section of such processes can exceed the corresponding differential cross-section without an external field by thirteen orders of magnitude. This effect makes it possible to obtain narrow beams of ultrarelativistic positrons (electrons) in strong electromagnetic fields with high probability.

Development and verification of a new nuclear data processing code AXSP

The advanced reactor design needs an accurate cross-section generation code. In this study, a new nuclear data processing code AXSP is developed, and the method and performance of which are described. Compared with the NJOY program, the precision of the unresolved resonance processing module UnresXS has been significantly improved due to the adoption of a more accurate solution method and the consideration of in-sequence overlap integrals. The time consumption of PUnresXS has been decreased significantly due to an optimized sorting algorithm. At the same time, other modules of AXSP are relatively comprehensive. The function of resolved resonance cross-section reconstruction and linearization is the ReconXS module. The Doppler broadening module is BroadXS by using Gauss–Hermite quadrature and Gauss–Legendre quadrature from 0 K temperature pointwise cross section to any temperature which is defined by the user. The shielding factor in the unresolved resonance energy region is calculated by the UnresXS or the PUnresXS module, which are developed based on the Bondarenko method and the probability table method, respectively. The ACE formatted cross sections for the Monte Carlo code is processed by the ACEXS module, and the multigroup cross sections are generated by the GroupXS module. The cross sections processed by different modules were verified by the NJOY2016 code, and the multigroup cross sections were also verified by using the critical benchmarks. The multiplication factor difference between AXSP and NJOY2016 is less than 20 pcm. In addition to this, the ZPR6/7 fast reactor is used for ACE format library verification. The results show that the criticality calculated by AXSP has a good agreement with that of NJOY2016.

The possibility of creating narrow beams of high-energy gamma quanta in the process of resonant spontaneous bremsstrahlung radiation of ultrarelativistic electrons on nuclei in strong electromagnetic fields

The production of narrow beams of high-energy gamma quanta in the process of resonant spontaneous bremsstrahlung radiation of ultrarelativistic electrons on nuclei in strong electromagnetic fields is predicted. This effect is realized under special experimental conditions for the frequencies and intensities of the laser installation. Resonant differential cross sections with simultaneous registration of the outgoing angle and the energy of the spontaneous gamma quantum, as well as a small number of absorbed photons of the wave, can exceed the corresponding differential cross section without an external field by 18–19 orders of magnitude. The obtained results can be used to obtain narrow beams of high-energy gamma quanta, as well as to explain high-energy gamma quanta near pulsars and magnetars.

Performing Bayesian Analyses With AZURE2 Using BRICK: An Application to the 7Be System

Phenomenological R-matrix has been a standard framework for the evaluation of resolved resonance cross section data in nuclear physics for many years. It is a powerful method for comparing different types of experimental nuclear data and combining the results of many different experimental measurements in order to gain a better estimation of the true underlying cross sections. Yet a practical challenge has always been the estimation of the uncertainty on both the cross sections at the energies of interest and the fit parameters, which can take the form of standard level parameters. Frequentist (χ2-based) estimation has been the norm. In this work, a Markov Chain Monte Carlo sampler, emcee, has been implemented for the R-matrix code AZURE2, creating the Bayesian R-matrix Inference Code Kit (BRICK). Bayesian uncertainty estimation has then been carried out for a simultaneous R-matrix fit of the 3He (α,γ)7Be and 3He (α,α)3He reactions in order to gain further insight into the fitting of capture and scattering data. Both data sets constrain the values of the bound state α-particle asymptotic normalization coefficients in 7Be. The analysis highlights the need for low-energy scattering data with well-documented uncertainty information and shows how misleading results can be obtained in its absence.

Tunable infrared high absorbing polarization independent niobium nitride plasmonic perfect absorber nanowire photodetectors

The recent development of photon-based technologies such as quantum cryptography and quantum computing requires high fidelity and fast photodetectors, as well as the ability to detect single photons. One possibility to achieve these goals are superconducting nanowire single photon detectors, utilizing the superconducting-to-normal conducting phase transition. To achieve the required high efficiency, we use resonant plasmonic perfect absorber effects, reaching over 90% polarization-independent absorbance at our target wavelength of 1140 nm. Moreover, the target wavelength can be easily tuned by adjusting the geometry of our detectors. Furthermore, the high absorbance is maintained at oblique incidence, due to the plasmonic perfect absorber principle, and small active areas can be achieved by the high resonant absorption cross-section of plasmonic resonances. We fabricated different tunable, polarization independent plasmonic perfect absorber superconducting nanowire photodetectors and proved their high absorbance and polarization independent response in the wavelength regime around 1140 nm.

Electron-positron pairs and radioactive nuclei production by irradiation of high-Z target with γ -photon flash generated by an ultra-intense laser in the λ3 regime

This paper studies the interaction of laser-driven $\ensuremath{\gamma}$ photons and high-energy charged particles with high-Z targets through Monte Carlo simulations. The interacting particles are taken from particle-in-cell simulations of the interaction of a tightly focused ultra-intense laser pulse with a titanium target. Lead is chosen as the secondary high-Z target because of its high cross-section of the giant dipole resonance and electron-positron pair production. The results reveal an ultra-short, ultra-relativistic collimated positron population and their energy spectra, angular distribution, and temporal profile are found. We investigate the target thickness dependence of the resulting total numbers and total kinetic energies of various particle species emitted from the lead target irradiated with laser-generated $\ensuremath{\gamma}$ photons and charged particles separately. We plot the charts of residual high-Z nuclides generated by irradiation of the lead target. Because of the short pulse duration, the $\ensuremath{\gamma}$ photon, electron-positron, and neutron sources could find applications in material science, nuclear physics, laboratory astrophysics, and as injectors in laser-based accelerators of charged particles.

Doppler broadening using discrete cosine transform and kernel reconstruction for spatially variable media

Doppler broadening plays key roles in understanding the temperature dependence of materials’ particle reaction rates, which are vital for high fidelity nuclear reactor physics simulations. However, the treatment of spatially continuously variable temperature distribution is far from its maturity to reach the goal of routine high fidelity reactor whole core transport. This article made an attempt to move one step closer to the goal by proposing and verifying a solution package innovative in three aspects. First, we present the DCT-DB Doppler broadening method, efficient in computation and compact for storage, being based on discrete cosine transform by reformulating the Doppler broadening problem as solving a heat equation. The total, elastic, absorption, capture and fission resonance plus background cross sections (if needed) of 512 nuclides from the most recent ENDF/B-VIII.0 data library are studied in the temperature ranging from 200 K to 3,000 K. The maximum relative errors achieve the 0.001 target (in the meaningful range) after validated against NJOY 2016. The new method is computationally efficient, where for the nuclides with maximum intermediate energy grid size of 226 (more than 67 millions), GPU delivers a computing power equivalent to 1 to 2 orders of magnitudes of CPU cores running with the NJOY Doppler broadening method, while generating cross sections at 1 to 2 orders of magnitudes lower errors. The storage of coefficients for all 512 nuclides compresses in an almost numerically lossless way to be 715 MB. Second, we combine the kernel reconstruction method with improved Monte Carlo delta tracking and track length (as track integral) estimators to perform on-the-fly Doppler broadening in media with spatially continuously variable properties, where the algorithm takes into consideration all of the temperature variance, the coolant density variance and the atomic density variance from such as depletion together. The on-the-fly Doppler broadening runtime data is 3.69 GB, attainable by taking as lower as minutes with the DCT-DB processing code on GPU. Numerical simulations of homogeneous pincell problems, homogeneous 3x3 assemblies mini reactor problems, and pincell problems with variable temperature distributions are validated against the ENDF point-wise cross sections, where the new method costs only 3 to 5 times more computational time than reference problems with uniform temperature valued at the single ENDF point-wise cross section table used, which is competitive with existing methods. The new method's competitiveness over windowed multipole for spatially variable media is justified for on-the-fly Doppler broadening for problems with depleted fuel on GPU devices as well. The widely adopted approach of using average temperatures in fuel, gap, clad and moderator of a pincell could underestimate fission power by 0.04% and k-effective by 45 pcm. In fair comparisons, Apple M1 Pro CPU is 3–6 times more energy efficient than mainstream AMD64 CPUs. The new method is also in favor of current and coming exascale HPC systems with large memory bandwidth. Third, we found a closed form of relationship between multipole parameters and DCT coefficients, which brings a broader picture to existing Doppler broadening methods.

Resonant spontaneous bremsstrahlung in the scattering of ultrarelativistic electrons on nuclei in a strong light field

Abstract An analytical study of the process of resonant spontaneous bremsstrahlung radiation during the scattering of ultrarelativistic electrons with energies by the nuclei in strong laser fields with intensities up to I ∼ 1025 Wcm-2 was carried out. Under resonant conditions, an intermediate electron in the wave field enters the mass shell. As a result, the initial second-order process by the fine structure constant is effectively reduced to two first-order processes: laser-stimulated Compton effect and laser-assisted Mott process. The resonant kinematics for two reaction channels (A and B) is studied in detail. An analytical resonant differential cross-section with simultaneous registration of the frequency and the outgoing angle of a spontaneous gamma-quantum is obtained. It is shown that the resonant differential cross-section has the largest value in the region of average laser fields and can be of the order of ∼ 1018 in units Z 2 α r e 2 . The obtained results reveal new features of spontaneous emission of ultrarelativistic electrons on nuclei in strong laser fields and can be tested at international laser installations.

Radiation of High-Energy Gamma Quanta by Ultrarelativistic Electrons on Nuclei in Strong X-ray Fields

The possibility of radiation of high-energy gamma quanta with energies of the order of 100 GeV by ultrarelativistic electrons on nuclei in strong X-ray fields with intensities up to ∼1027Wcm−2 was theoretically studied. It is shown that this effect can be realized under special experimental conditions in the process of resonant spontaneous bremsstrahlung radiation of ultrarelativistic electrons on nuclei in an external electromagnetic field. These special experimental conditions determine the characteristic energy of the electrons. This characteristic energy should be significantly less than the energy of the initial electrons. Under these conditions, spontaneous gamma quanta are emitted in a narrow cone with energies close to the energy of the initial electrons. Moreover, the resonant differential cross-sections of such processes can exceed the corresponding differential cross-section without an external field by twenty orders of magnitude. The results obtained can explain the occurrence of high-energy gamma quanta near pulsars and magnetars.

Spinopelvic measurements of sagittal balance with deep learning: systematic review and critical evaluation.

To summarize and critically evaluate the existing studies for spinopelvic measurements of sagittal balance that are based on deep learning (DL). Three databases (PubMed, WoS and Scopus) were queried for records using keywords related to DL and measurement of sagittal balance. After screening the resulting 529 records that were augmented with specific web search, 34 studies published between 2017 and 2022 were included in the final review, and evaluated from the perspective of the observed sagittal spinopelvic parameters, properties of spine image datasets, applied DL methodology and resulting measurement performance. Studies reported DL measurement of up to 18 different spinopelvic parameters, but the actual number depended on the image field of view. Image datasets were composed of lateral lumbar spine and whole spine X-rays, biplanar whole spine X-rays and lumbar spine magnetic resonance cross sections, and were increasing in size or enriched by augmentation techniques. Spinopelvic parameter measurement was approached either by landmark detection or structure segmentation, and U-Net was the most frequently applied DL architecture. The latest DL methods achieved excellent performance in terms of mean absolute error against reference manual measurements (~ 2° or ~ 1mm). Although the application of relatively complex DL architectures resulted in an improved measurement accuracy of sagittal spinopelvic parameters, future methods should focus on multi-institution and multi-observer analyses as well as uncertainty estimation and error handling implementations for integration into the clinical workflow. Further advances will enhance the predictive analytics of DL methods for spinopelvic parameter measurement. Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

Post Collision Interraction Effect on the magnitude(e, 2e) Autoionization Amplitude

Post collision interaction effect on the magnitude of the He(e,2e)He* direct and resonant amplitudes as a function of electron ejection angle has been considered. Calculated values are found in good agreement with the extracted experimental data. It is shown that the 3-body Coulomb interaction in final state may give a considerable contribution to the direct cross section, but a small account to the resonant cross section.

Search for heavy resonances decaying to WW , WZ , or WH boson pairs in a final state consisting of a lepton and a large-radius jet in proton-proton collisions at s=13 TeV

A search for new heavy resonances decaying to pairs of bosons (WW, WZ, or WH) is presented. The analysis uses data from proton-proton collisions collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb$^{-1}$. One of the bosons is required to be a W boson decaying to an electron or muon and a neutrino, while the other boson is required to be reconstructed as a single jet with mass and substructure compatible with a quark pair from a W, Z, or Higgs boson decay. The search is performed in the resonance mass range between 1.0 and 4.5 TeV and includes a specific search for resonances produced via vector boson fusion. The signal is extracted using a two-dimensional maximum likelihood fit to the jet mass and the diboson invariant mass distributions. No significant excess is observed above the estimated background. Model-independent upper limits on the production cross sections of spin-0, spin-1, and spin-2 heavy resonances are derived as functions of the resonance mass and are interpreted in the context of bulk radion, heavy vector triplet, and bulk graviton models. The reported bounds are the most stringent to date.