Energy Cross Sections Research Articles

Polarimetry for a storage-ring electric-dipole-moment measurement

These proceedings summarize the progress which has been made within the Jülich Electric Dipole Moment Investigations (JEDI) Collaboration on deuteron beam polarimetry for a storage-ring electric-dipole-moment (EDM) measurement. The design of a dedicated EDM polarimeter requires a precise database for optimization purposes. To address this need, a measurement of a deuteron-carbon scattering database has been performed with the forward part of the WASA-at-COSY detector. Preliminary results for vector analyzing powers and unpolarized differential cross sections for different deuteron beam energies are presented.

Impact of average neutron energy on the fast neutron fluency measurement by Np237 fission to capture ratio and reverse dark current of planar silicon detector methods

This work is a subsequent step to study the feasibility of fast neutron fluency measurements using two different complementary methods. Np-237 samples and planar silicon detectors were mounted very close to each other on different sections of a subcritical assembly irradiated with the proton beam of 0,66 GeV (the Quinta assembly at the Joint Institute for Nuclear Research, Dubna, Russia) to provide both samples with the same neutron fluency. We have processed the experimental data of irradiated Np-237 actinide samples and silicon detectors directly placed on two sections of the QUINTA setup without a lead shield-reflector. Applying the try and error method we have found found that the neutron energy for which the ratio of the fission cross section to the capture cross section of the actinide Np-237 from the nuclear data base is equal to the measured ratio of the fissioned and captured actinide isotopes. The retrieved distinct fission and capture cross sections for the distinct neutron energy from the nuclear data base describe the average values. The considered above experimental and earlier obtained data have been shown that the higher is the average neutron energy the smaller is the difference of the neutron fluency measurement between the two methods. This effect has been expected since the silicon detector method efficiently measures the fast neutrons of the energy higher than about 170 keV while the actinide method covers a wider energy range.

Deep levels, charge transport and mixed conductivity in organometallic halide perovskites

Understanding the type, formation energy and capture cross section of defects is one of the challenges in the field of organometallic halide perovskite (OMHP) devices.

Application and evaluation of Chinese spallation neutron source in single-event effects testing

Due to the lack of available spallation neutron source, the atmospheric neutron single event effect (SEE) in China were studied mainly by means of simulation and single energy neutron test. Since the Chinese spallation neutron source (CSNS) passed the national acceptance, it has become possible to carry out the research on atmospheric neutron SEE by using the CSNS. In this paper, the neutron SEE experiments of 3 kinds of SRAMs with different feature sizes are carried out for the first time by using the CSNS back-n. The application of CSNS back-n in the study of atmospheric neutron SEE is evaluated by comparing with the results of the earlier plateau experiment. The results show that the cross section of the single event upset is smaller than that of the plateau test, and the cross sections of different devices have no obvious monotonic relationship with feature size. The reason for the former result is that the energy spectrum of CSNS back-n is slightly softer than that of the atmospheric neutron. The reason for the second result is that small feature size means small critical charge and small sensitive volume, and these two factors compete with each other when they make the contribution to the cross section. According to the difference in energy spectrum and cross section among the SRAM devices, a correction factor is proposed to correct the test results based on CSNS back-n. For the difference in energy spectrum, different energy thresholds will produce different ratios between the cross sections by using CSNS back-n and atmospheric neutron. The neutrons of CSNS back-n are mainly concentrated around 1 MeV, which is close to the energy threshold of general SRAM devices. Thus, inaccurate energy threshold estimation will introduce a large error into the cross section of SEU. Thus, the relation between the correction factor and the energy threshold is analyzed. If 12 MeV is selected as the energy threshold to calculate the cross section, more consistent results could be obtained for our DUT in CSNS back-n and atmospheric neutron environment. In a word, the results show that the CSNS back-n can be used to speed up the atmospheric neutron SEE test, but the result should be corrected to evaluate the threat from atmospheric neutron. Fortunately, with the continuous increase of CSNS operating power, the neutron flux and the accelerated factor of CSNS will increase synchronously. Besides, other 3 white light neutron beams are planned in the CSNS project, the planned energy spectra are closer to those of atmospheric neutron. It is expected that the CSNS will be better applied to the study of atmospheric neutron SEE.

Studies of the UHECR Mass Composition and Hadronic Interactions with the FD and SD of the Pierre Auger Observatory

With data on the depth of maximum Xmax collected during more than a decade of operation of the Pierre Auger Observatory, we report on the inferences on the mass composition of UHECRs in the energy range E = 1017.2 – 1019.6 eV and on the measurements of the proton-air cross section for energies up to 1018.5 eV. We also present the results on Xmax obtained using the information on the particle arrival times recorded by the SD stations allowing us to extend the Xmax measurements up to 1020 eV. The inferences on mass composition, in particular using the data of the SD, are subject to systematic uncertainties due to uncertainties in the description of hadronic interactions at ultra-high energies. We discuss this problem with respect to the properties of the muonic component of extensive air-showers as derived from the SD data.

Experimental study on fission reaction rate induced by D-T neutron in depleted uranium shell

Fission reaction rate is an important index for validating and checking the neutron transportation and fission power in nuclear engineering. The experimental data can be used in benchmark validation of cross sections, and in studying the correlation of fission power with the thickness of uranium sphere shell. There are five assemblies of depleted uranium shells used in this work, the inner radii of which are all fixed at 13.1 cm, while their outer radii are 18.1, 19.4, 23.35, 25.4 and 28.5 cm, respectively. The D-T neutron source is generated in the center of the assemblies, the yield of which is about 3 × 10<sup>10</sup>−4 × 10<sup>10</sup> s<sup>–1</sup>. In horizontal plane across the center of the assemblies, the fission rates at positions along the radial direction are measured in the direction with 45° inclining with respect to the incident D<sup>+</sup> beam. Due to the disturbance to assemblies and neutron field, the activation foil of uranium is a suitable choice rather than fission chamber or capture detector. The material of activation foil is the same as that in the experimental assemblies. Considering the accurate fission yield of <sup>143</sup>Ce, the objective nuclides are selected. The total fission yield of <sup>143</sup>Ce is contributed by <sup>238</sup>U and a little <sup>235</sup>U. For calculating the total fission yiled of <sup>143</sup>Ce, the neutron energy range of 0−15 MeV is divided into eight subranges. By measuring the 293 keV gamma rays from the fission product <sup>143</sup>Ce in activation foils with a TRANS-SPEC-DX100 HPGe detector, with a relative efficiency 40%, the fission rates and the trends at positions along the radial direction in the five assemblies are obtained based on the <sup>143</sup>Ce fission product yield. The fission rate ranges from 5.28 × 10<sup>–29</sup> to 7.58 × 10<sup>–28</sup> sn<sup>-1</sup>·nuclide<sup>–1</sup>, with the relative uncertainty in a range from 6% to 11%. The Monte Carlo transport code MCNP5 and continuous energy cross section library ENDF/BV.8 are used for analyzing the fission rate distribution in the assemblies, and the experiemtal configuration, including the wall of the experimental hall is described in detail in the model. The calculated results are compared with the experimental ones and their agreement is found to be in an uncertainty range.

Electron–atom bremsstrahlung cross sections in the 20–100 keV energy region: absolute measurements for and comparison with theoretical databases

We report absolute measurements of doubly differential electron–atom bremsstrahlung cross sections for energies in the keV region and elements with atomic numbers 6, 13, 52, 73 and 79. Thin targets were irradiated at the low-energy beam line of the São Paulo Microtron with 20, 50, 75 and 100 keV electrons. For each element and energy, the photon spectra were collected simultaneously with three HPGe detectors at the emission angles of 35°, 90° and 131°. The deconvolution of the bremsstrahlung spectra was done adopting an analytical model for the spectrometers’ response functions. The resulting doubly differential cross sections are compared with the available partial-wave calculations of ordinary bremsstrahlung. Based on this comparison, we discuss some features of the experimental spectra that might be related to the emission of polarization bremsstrahlung.

Neutron inelastic scattering on 54Fe

A neutron inelastic scattering experiment was performed at the Geel Electron Linear Accelerator neutron source using an enriched 54Fe sample. The $\gamma$ rays produced in the reaction were detected using the Gamma Array for Inelastic Neutron Scattering spectrometer. For each observed transition we determined the $\gamma$ -production cross section for incident energies ranging from the inelastic threshold ( $\approx 1.434$ MeV) up to 18 MeV. Using these primary data we also calculated the cross section of the first excited level and the total inelastic cross section. Our experimental results are compared with previous reported values, evaluated nuclear data libraries and theoretical calculations performed with the TALYS 1.9 code. A careful tuning of the optical model parameters allowed significant improvements in the description of the experimental results leading to interesting conclusions regarding the interaction of the 54Fe nucleus with neutrons.

Polarization Observables of the Reaction γp→η'p Near Threshold

In the isobaric model of photoproduction of η'-mesons on protons, reproducing well the experimental cross sections for photon energies from 1500 to 2500 MeV and the Σ-asymmetry of this reaction near its threshold, various polarization observables of this reaction have been calculated in the energy range near its threshold in order to stimulate future experiments.

VOLSCAT2.0: The new version of the package for electron and positron scattering off molecular targets

VOLSCAT2.0: The new version of the package for electron and positron scattering off molecular targets

Demonstration of Multigroup Multiband Cross Section Generation in Monte Carlo Simulations

This is the investigation into the generation of high-fidelity multigroup multiband cross sections from Monte Carlo neutron transport simulations. Previous methods for generating multigroup multiband (MGMB) cross sections, and multigroup cross sections, assume an approximate shape for the scalar flux. This approximate flux shape is the product of an energy-dependent spectrum and a cross-section-dependent self-shielding factor for the material of interest. Since, these methods assume a scalar flux a priori, the cross sections generated may not be sufficiently consistent with the actual scalar flux of any particular problem. Instead, in our approach we tally both the reaction rate and the flux for each energy group and cross section magnitude band using the Mercury Monte Carlo particle transport code and compute the group-band cross sections from these tallies. This approach eliminates the need for assuming a flux by using a Monte Carlo simulation to calculate these cross sections. The increased physical fidelity of MGMB also requires more data storage, since more than one cross section value needs to be stored per energy group. However, this storage tradeoff could be mitigated by using less energy groups.

Structure, spectroscopy and cold collisions of the (SrNa)+ ionic system

We perform a study on extended adiabatic potential energy curves of nearly 38 states of 1,3$\Sigma^+$, 1,3$\Pi$ and 1,3$\Delta$ symmetries for the (SrNa)$^+$ ion, though only the ground and first two excited states are used for the study of scattering processes. Full Interaction Configuration (CI) calculations are carried out for this molecule using the pseudopotential approach. In this context, it is considered that two active electrons interact with the ionic cores and all single and double excitations were included in the CI calculations. A correction including the core-core electron interactions is also considered. Using the accurate potential energy data, the ground state scattering wave functions and cross sections are obtained for a wide range of energies. We find that, in order to get convergent results for the total scattering cross sections for energies of the order 1 K, one need to take into account at least 87 partial waves. In the low energy limit ( < 1 mK), elastic scattering cross sections exhibit Wigner law threshold law behavior while in the high energy limit the cross sections go as $E^{-1/3}$. A qualitative discussion about the possibility of forming the cold molecular ion by photoassociative spectroscopy is presented.

Accurate integral cross sections for the H + CO2 → OH + CO reaction

A full-dimensional quantum dynamics calculation has been carried out to yield the coupled-channel reaction probabilities with total angular momentum J up to 60 for the H + CO2 → OH + CO reaction on the PIP-NN PES potential energy surface. Well converged integral cross section (ICSs) for collision energy up to 2.4 eV were obtained for the ground initial state. As compared with previous study, it is found that the CS approximation substantially underestimated ICSs, which is inadequate for the title reaction. In addition, the agreement between QM and QCT ICSs is quite satisfactory, indicating that the QCT method is rather accurate on describing dynamics of this complex-forming reaction.

Investigation of (n, α) Reaction Cross Sections for a Number of Structural Material Isotopes

A novel spectrometer was developed and used to measure the cross section for the (n, α) reaction at the Institute for Physics and Power Engineering. Direct measurements of the alpha particles yielded from isotopically enriched solid targets of 50Cr, 52Cr, and 53Cr; 54Fe and 57Fe; 60Ni; 64Zn; and 47Ti were carried out in the neutron energy range from 4.0 to 7.2 MeV. For some of the isotopes, the (n, α) reaction cross sections for neutron energies below 14 MeV were measured for the first time. The result of the comparison of new experimental data with the evaluated data from ENDF/B-VII, JENDL-4.0, JEFF-3.2, ROSFOND-2010, and BROND-3 libraries and with the experimental data of other authors is presented.

Electron impact total ionization cross section for C4 and C5 isomeric alcohols

Electron scattering total ionization cross sections are reported for butanol and pentanol isomers. These data have relevance in modelling spark ignition and combustion of species that constitute important third generation bio fuels. The total inelastic cross sections are calculated using spherical complex optical potential formalism, and complex scattering potential-ionization contribution method is employed to extract ionization cross section from inelastic cross section for incident energies ranging from ionization threshold to 5000 eV. Group additivity rule is modified using newly introduced electrostatic potential surface method to identify individual scattering centres that contribute to the cross section of the target molecule as a whole. Isomeric effect has been studied for the set of target species and has been found to have a small, but considerable impact on cross sections. Reasonable agreement with available experimental results has been obtained for butanol. The cross sections for pentanol isomers have been reported here for the first time.

Role of Mn2+ ions on optical and luminescent properties of CaF2–Y2O3–ZnO–B2O3–SiO2 glasses

MnO doped CaF2–Y2O3–ZnO–B2O3–SiO2 glasses were synthesized. Different physical parameters of these glass materials such as density, molar volume, electronegativity, optical basicity and refractive index were calculated. The glass transition and glass crystallization temperatures of these glasses were measured by DTA analysis. The mechanical properties such as Young’s modulus, Shear modulus, Bulk modulus, Poisson’s ratio and microhardness of these materials were also calculated. Different characterization such as FT-IR, ESR, DC conductivity, optical absorption and photoluminescence were carried out on the prepared glass samples. ESR studies of these glass materials exhibited sextet at lower concentrations of MnO. The optical bandgap, Urbach energy, transition probability and emission cross section of these glass materials were calculated. Semiconducting nature of these glass materials was also observed due to the significant increase in BO3 and MnO6 units with increasing concentration of MnO. Optical absorption studies revealed that the increase in intensity of different octahedral peaks were due to the increase in concentration of MnO. Photoemission occurs around 545 to 567.3 nm suggested that the emission was red-shifted for higher MnO concentration and green-shifted for lower MnO concentration.

Role of Mn2+ ions on optical and luminescent properties of LiF–Sb2O3–ZnO–B2O3–SiO2 glasses

MnO doped LiF–Sb2O3–ZnO–B2O3–SiO2 glasses were synthesized by melt quenching technique. Different physical parameters such as density, molar volume, electronegativity, optical basicity and refractive index were calculated. The non-crystalline nature of the samples was confirmed by XRD analysis. SEM images projected that the prepared glass materials were contain well defined and indiscriminately allocated grains. The chemical analysis of these materials was studied by energy dispersion spectrum. The glass transition and glass crystallization temperatures of the glasses were recorded by DTA. FT-IR, Raman and ESR studies were also carried out on the prepared glass samples. The optical absorption reports of these glass materials have suggested that the octahedral tendency of Mn2+ ions increases with increasing concentration of MnO. The optical bandgap, Urbach energy, transition probability and emission cross section of these glass materials were calculated. Photoluminescence studies were also performed on the glass samples. The outcomes on all the investigations of these glasses have suggested that the Mn2+ ions predominantly occupy octahedral sites at higher concentrations of MnO.

Derived properties from the dipole and generalized oscillator strength distributions of an endohedral confined hydrogen atom

We report the electronic properties of a hydrogen atom confined by a fullerene molecule by obtaining the eigenvalues and eigenfunctions of the time-independent Schrödinger equation by means of a finite-differences approach. The hydrogen atom confinement by a C60 fullerene cavity is accounted for by two model potentials: a square-well and a Woods–Saxon. The Woods–Saxon potential is implemented to study the role of a smooth cavity on the hydrogen atom generalized oscillator strength distribution. Both models characterize the cavity by an inner radius R0, thickness Δ, and well depth V0. We use two different values for R0 and Δ, found in the literature, that characterize H@C60 to analyze the role of the fullerene cage size and width. The electronic properties of the confined hydrogen atom are reported as a function of the well depth V0, emulating different electronic configurations of the endohedral cavity. We report results for the hyper-fine splitting, nuclear magnetic screening, dipole oscillator strength, the static and dynamic polarizability, mean excitation energy, photo-ionization, and stopping cross section for the confined hydrogen atom. We find that there is a critical potential well depth value around V0 = 0.7 a.u. for the first set of parameters and around V0 = 0.9 a.u. for the second set of parameters, which produce a drastic change in the electronic properties of the endohedral hydrogen system. These values correspond to the first avoided crossing on the energy levels. Furthermore, a clear discrepancy is found between the square-well and Woods–Saxon model potential results on the hydrogen atom generalized oscillator strength due to the square-well discontinuity. These differences are reflected in the stopping cross section for protons colliding with H@C60.

Asymptotic form of the high energy photoionization cross section of fullerenes

We show that the theoretical predictions on high energy behavior of the photoionization cross section of fullerenes depend crucially on the form of the function V(r) which approximates the fullerene field. The shape of the high energy cross section is obtained without solving the wave equation. The cross section energy dependence is determined by the analytical properties of the function V(r).

Measurement of the multi-TeV neutrino interaction cross-section with IceCube using Earth absorption.

Neutrinos interact only very weakly, so they are extremely penetrating. The theoretical neutrino-nucleon interaction cross-section, however, increases with increasing neutrino energy, and neutrinos with energies above 40 teraelectronvolts (TeV) are expected to be absorbed as they pass through the Earth. Experimentally, the cross-section has been determined only at the relatively low energies (below 0.4 TeV) that are available at neutrino beams from accelerators. Here we report a measurement of neutrino absorption by the Earth using a sample of 10,784 energetic upward-going neutrino-induced muons. The flux of high-energy neutrinos transiting long paths through the Earth is attenuated compared to a reference sample that follows shorter trajectories. Using a fit to the two-dimensional distribution of muon energy and zenith angle, we determine the neutrino-nucleon interaction cross-section for neutrino energies 6.3-980 TeV, more than an order of magnitude higher than previous measurements. The measured cross-section is about 1.3 times the prediction of the standard model, consistent with the expectations for charged- and neutral-current interactions. We do not observe a large increase in the cross-section with neutrino energy, in contrast with the predictions of some theoretical models, including those invoking more compact spatial dimensions or the production of leptoquarks. This cross-section measurement can be used to set limits on the existence of some hypothesized beyond-standard-model particles, including leptoquarks.