Calculated Energy Spectra Research Articles

Primary knock on atom spectra, gas production and displacement cross section for tungsten and chromium irradiated with neutrons at energies up to 14.1 MeV

In the ITER and other proposed fusion reactors, chromium and tungsten are proposed as first wall materials. Fusion of DT plasma will produce neutrons of 14.1 MeV energy. Nuclear reactions of fusion reactor material with such high energy neutrons lead to the displacement cascades and gas production in the reactor materials. All probable reaction channels such as (n,n’), (n,2n), (n,p), (n,α) and (n,d) are open for the interactions of these neutrons with tungsten and chromium. In the present study, energy spectra of recoils or PKA, gas production and displacement cross section for tungsten and chromium at neutrons of up to 14.1 MeV energy have been predicted using the appropriate nuclear models in the TALYS-1.8 code. In the cross section and PKA calculations, the contributions from possible reaction mechanisms such as direct, pre-equilibrium, and compound nuclear mechanisms have been considered. Calculated energy spectra of protons, alpha particles, and outgoing neutrons have been compared with recent ENDF-VIII, JEFF-3.3 and TENDL-2017 data libraries and discrepancies among them have been discussed. PKA data from each reaction channels have been calculated. PKA data have been used to predict the displacement cross-section with the Norgett, Robinson, and Torrens (NRT) approach. Calculated displacement cross section data of chromium and tungsten have been compared with existing data.

Contribution of Supernova Remnants to CRs Secondary to Primary ratios

We study production of secondary cosmic rays (CR) in supernova remnants (SNR). The model includes reacceleration of already existing in interstellar medium secondary CR particles as well as creation of secondary CRs in nuclear collisions of accelerated protons with gas nuclei and their subsequent acceleration by SNR shock. It is shown that generation of secondary CRs in SNRs produces considerable effect in their resultant energy spectrum making it essentially flatter above 10 GeV. It is shown that calculated energy spectra of antiprotons, positrons and secondary nuclei Li, Be, B are well consistent with experimental data obtained in recent experiments PAMELA, Fermi and AMS-02.

Electronic Structure of GdCuGe Intermetallic Compound

The electronic structure of GdCuGe intermetallic compound has been studied. Spin-polarized energy spectrum calculations have been performed by the band method with allowance for strong electron correlations in the 4f-shell of gadolinium ions. Antiferromagnetic ordering of GdCuGe at low temperatures has been obtained in a theoretical calculation, with the value of the effective magnetic moment of gadolinium ions reproduced in fair agreement with experimental data. The electronic density of states has been analyzed. An optical conductivity spectrum has been calculated for GdCuGe; it reveals specific features that are analogous to the ones discovered previously in the GdCuSi compound with a similar hexagonal structure.

A function to provide neutron spectrum produced from the 9Be + p reaction with protons of energy below 12 MeV

ABSTRACTA function to give the total neutron production cross section, angular distribution, and energy spectrum via the 9Be + p reaction has been created by fitting experimental data to characterize compact neutron sources with thick Be targets bombarded by protons with energy below 12 MeV. To examine the suitability of the function, calculations of the angle-dependent neutron energy spectra produced in thick Be targets with 4- and 12-MeV protons using the function were compared with corresponding experiments and calculations using the nuclear data libraries of ENDF/B-VII.0 and JENDL4.0/HE. The function was in better agreement with the experiments than the calculations using the libraries except for at backward angles. The 115In(n,n’)115mIn reaction rates calculated using GEANT4 with source neutrons given by both the function and ENDF/B-VII.0 were compared with that measured at the RIKEN Accelerator-Driven Compact Neutron Source to evaluate the neutron spectrum above 1 MeV. The function slightly overestimated the measurement by 14% and the calculation with ENDF/B-VII.0 underestimated by 35%. It was concluded that the function can be applied in compact neutron source designs.

Single inclusive jet production and the nuclear modification ratio at very forward rapidity in proton-lead collisions with [formula omitted] TeV

We present calculations of single inclusive jet transverse momentum and energy spectra at forward rapidity (5.2<y<6.6) in proton-lead collisions with sNN=5.02 TeV. The predictions are obtained with the KaTie Monte Carlo event generator, which allows to calculate interactions within the High Energy Factorisation framework. The tree-level matrix element results are subsequently interfaced with the CASCADE Monte Carlo event generator to account for hadronisation. The effects of the saturation of the gluon density, leading to suppression of the cross section, are investigated.

Structure of BeΛ9 and BeΛΛ10 using the beyond-mean-field Skyrme-Hartree-Fock approach

Based on the beyond-mean-field Skyrme-Hartree-Fock model, the up-to-date Skyrme-type $N\mathrm{\ensuremath{\Lambda}}$ interaction, SLL4, is used to investigate the properties of $_{\mathrm{\ensuremath{\Lambda}}}^{9}\mathrm{Be}$ comprehensively. Energies of different configurations, such as $^{8}\mathrm{Be}\ensuremath{\bigotimes}\mathrm{\ensuremath{\Lambda}}[000]1/{2}^{+}, ^{8}\mathrm{Be}\ensuremath{\bigotimes}\mathrm{\ensuremath{\Lambda}}[110]1/{2}^{\ensuremath{-}}, ^{8}\mathrm{Be}\ensuremath{\bigotimes}\mathrm{\ensuremath{\Lambda}}[101]3/{2}^{\ensuremath{-}}$, and $^{8}\mathrm{Be}\ensuremath{\bigotimes}\mathrm{\ensuremath{\Lambda}}[101]1/{2}^{\ensuremath{-}}$ are given and used to study the effects of $\mathrm{\ensuremath{\Lambda}}$ occupying different orbitals. The calculated energy spectra, including both positive- and negative-parity levels, are given and compared to the experimental data. The observed positive-parity spin doublets ($3/{2}^{+},5/{2}^{+}$) are successfully reproduced, but the energy difference needs further investigation. The two well-known band structures corresponding to the genuine hypernuclear states and the $^{9}\mathrm{Be}$-analog states are also obtained and compared with the observed ones. The shrinkage effect of $\mathrm{\ensuremath{\Lambda}}$ occupying $\mathrm{\ensuremath{\Lambda}}[000]1/{2}^{+}$ is investigated through the density distributions of nuclear core. And finally, the $E2$ transition rates are given and compared with the observed data and with the results of the hypernuclear particle-rotor model. Properties of $_{\mathrm{\ensuremath{\Lambda}}\mathrm{\ensuremath{\Lambda}}}^{10}\mathrm{Be}$ are also studied to show the completeness of this current model.

Energy spectra of vibron and cluster models in molecular and nuclear systems

The relation of the algebraic cluster model, i.e., of the vibron model and its extension, to the collective structure, is discussed. In the first section of the paper, we study the energy spectra of vibron model, for diatomic molecule then we derive the rotation-vibration spectrum of \( 2\alpha\), \( 3\alpha\) and \(4\alpha\) configuration in the low-lying spectrum of 8Be, 12C and 16O nuclei. All vibrational and rotational states with ground and excited A, E and F states appear to have been observed, moreover the transitional descriptions of the vibron model and \( \alpha\)-cluster model were considered by using an infinite-dimensional algebraic method based on the affine \(\widehat{SU(1,1)}\) Lie algebra. The calculated energy spectra are compared with experimental data. Applications to the rotation-vibration spectrum for the diatomic molecule and many-body nuclear clusters indicate that there are solvable models and they can be approximated very well using the transitional theory.

Cluster shell model: I. Structure of 9Be, 9B

We calculate energy spectra, electromagnetic transition rates, longitudinal and transverse electron scattering form factors and log ft values for beta decay in 9Be, 9B, within the framework of a cluster shell model. By comparing with experimental data, we find strong evidence for the structure of these nuclei to be two α-particles in a dumbbell configuration with Z2 symmetry, plus an additional nucleon.

Energy Levels Calculations in &amp;lt;sup&amp;gt;23&amp;lt;/sup&amp;gt;Mg/&amp;lt;sup&amp;gt;23&amp;lt;/sup&amp;gt;Na and &amp;lt;sup&amp;gt;47&amp;lt;/sup&amp;gt;Cr/&amp;lt;sup&amp;gt;47&amp;lt;/sup&amp;gt;V Mirror Nuclei

Coulomb Displacement Energies in mirror nuclei ²³Mg, ²³Na and ⁴⁷Cr, ⁴⁷V have been calculated using shell model code OXBASH [1] and compared with experimental results. The calculations were carried out in the USD model space with the W Hamiltonian [2]. This code which is based on one of the most applicable nuclear models, the shell model, deals with evaluating energy levels in nuclei. A comparison had been made between computational results in this paper and the available experimental data to test theoretical shell model description of nuclear structure in mirror nuclei. The energy states of mirror nuclei are almost identical, except for the small effects due to Coulomb interaction where the symmetry in being broken. The calculated energy spectrum is in good agreement with the available experimental data.

Realistic shell model description of beta decay

In this paper, we extend our previous realistic shell-model study of Gamow-Teller strengths and double-β decay properties for nuclei around 132Sn to lighter mass nuclei. The effective shell-model Hamiltonian and transition operators are microscopically derived by way of many-body perturbation theory, without resorting to empirical parameters. Our main aim is to further check the reliability of our approach and verify its stability in other mass regions. Calculated energy spectra as well as electric-quadrupole and β-decay properties are presented for 76Ge and 82Se and compared with the experimental data, together with some results for 130Te and 136Xe already reported in our previous paper. Finally, some preliminary results of nuclear matrix elements responsible for the neutrinoless double beta decay, calculated by using the bare operator, are shown.

Nuclear Neutrino Spectra in Late Stellar Evolution

Neutrinos are the principle carriers of energy in massive stars, beginning from core carbon burning and continuing through core collapse and after the core bounce. In fact, it may be possible to detect neutrinos from nearby pre-supernova stars. Therefore, it is of great interest to understand the neutrino energy spectra from these stars. Leading up to core collapse, beginning around core silicon burning, nuclei become dominant producers of neutrinos, particularly at high neutrino energy, so a systematic study of nuclear neutrino spectra is desirable. We have done such a study, and we present our sd-shell model calculations of nuclear neutrino energy spectra for nuclei in the mass number range A = 21 – 35. Our study includes neutrinos produced by charged lepton capture, charged lepton emission, and neutral current nuclear deexcitation. Previous authors have tabulated the rates of charged current nuclear weak interactions in astrophysical conditions, but the present work expands on this not only by providing neutrino energy spectra, but also by including the heretofore untabulated neutral current de-excitation neutrino pairs.

Neutrino Spectra from Nuclear Weak Interactions in sd-Shell Nuclei under Astrophysical Conditions

Abstract We present shell model calculations of nuclear neutrino energy spectra for 70 sd-shell nuclei over the mass number range A = 21–35. Our calculations include nuclear excited states as appropriate for the hot and dense conditions characteristic of pre-collapse massive stars. We consider neutrinos produced by charged lepton captures and decays, and for the first time in tabular form, neutral current nuclear deexcitation, providing neutrino energy spectra on the Fuller–Fowler–Newman temperature–density grid for these interaction channels for each nucleus. We use the full sd-shell model space to compute initial nuclear states up to 20 MeV excitation with transitions to final states up to 35–40 MeV, employing a modification of the Brink-Axel hypothesis to handle high-temperature population factors and the nuclear partition functions.

Электронная структура интерметаллического соединения GdCuGe

AbstractThe electronic structure of GdCuGe intermetallic compound has been studied. Spin-polarized energy spectrum calculations have been performed by the band method with allowance for strong electron correlations in the 4 f -shell of gadolinium ions. Antiferromagnetic ordering of GdCuGe at low temperatures has been obtained in a theoretical calculation, with the value of the effective magnetic moment of gadolinium ions reproduced in fair agreement with experimental data. The electronic density of states has been analyzed. An optical conductivity spectrum has been calculated for GdCuGe; it reveals specific features that are analogous to the ones discovered previously in the GdCuSi compound with a similar hexagonal structure.

Fragments in heavy ion collisions in a hydrodynamic approach with a nonequilibrium equation of state

A hydrodynamic approach with a nonequilibrium equation of state is used to describe heavy ion collisions at medium energies. This approach includes describing the compression, dilution, and freeze-out stages of a hot spot formed during a heavy ion collision. The calculated energy spectra of protons and light 4He, 7Li, 9Be fragments produced in the 14N + 124Sn reaction at a 14N ion energy of 32 MeV/nucleon are compared to experimental data.

Topological magnon bound states in periodically modulated Heisenberg XXZ chains

Strongly interacting topological states in multi-particle quantum systems pose great challenges to both theory and experiment. Recently, bound states of elementary spin waves (magnons) in quantum magnets have been experimentally observed in quantum Heisenberg chains comprising ultracold Bose atoms in optical lattices. Here, we explore a strongly interacting topological state called topological magnon bound-state in the quantum Heisenberg chain under cotranslational symmetry. We find that the cotranslational symmetry is the key to the definition of a topological invariant for multi-particle quantum states, which enables us to characterize the topological features of multi-magnon excitations. We calculate energy spectra, density distributions, correlations and Chern numbers of the two-magnon bound-states and show the existence of topological protected edge bound-states. Our study not only opens a new prospect to pursue topological magnon bound-states, but also gives insights into the characterization and understanding of strongly interacting topological states.

Combined BC/MD approach to the evaluation of damage from fast neutrons and its implementation for beryllium irradiation in a fusion reactor

The determination of primary damage production efficiency in metals irradiated with fast neutrons is a complex problem. Typically, the majority of atoms are displaced from their lattice positions not by neutrons themselves, but by energetic primary recoils, that can produce both single Frenkel pairs and dense localized cascades. Though a number of codes are available for the calculation of displacement damage from fast ions, they commonly use binary collision (BC) approximation, which is unreliable for dense cascades and thus tend to overestimate the number of created displacements. In order to amend the radiation damage predictions, this work suggests a combined approach, where the BC approximation is used for counting single Frenkel pairs only, whereas the secondary recoils able to produce localized dense cascades are stored for later processing, but not followed explicitly. The displacement production in dense cascades is then determined independently from molecular dynamics (MD) simulations. Combining contributions from different calculations, one gets the total number of displacements created by particular neutron spectrum. The approach is applied here to the case of beryllium irradiation in a fusion reactor. Using a relevant calculated energy spectrum of primary knocked-on atoms (PKAs), it is demonstrated that more than a half of the primary point defects (∼150/PKA) is produced by low-energy recoils in the form of single Frenkel pairs. The contribution to the damage from the dense cascades as predicted using the mixed BC/MD scheme, i.e. ∼110/PKA, is remarkably lower than the value deduced from uncorrected SRIM calculations (∼145/PKA), so that in the studied case SRIM tends to overpredict the total primary damage level.

First-principles energy and vibration spectrum simulations of Cr/V interacting with H in W-based alloy in a fusion reactor

ABSTRACT We perform first-principles total energy and vibration spectrum calculations to study the effect of Cr/V on the H formation and diffusion at temperature range 300–2100 K in dilute W–Cr/W–V alloy. Temperature and H chemical potential are two important factors to affect the H formation energy and migrating energy. The H formation energy referring to the static/temperature-dependent H chemical potential decreases/increases with the temperature. At each given temperature, the presence of Cr in W reduces the H formation energy, while the existence of V in W has little effect on the H formation energy. The diffusion energy barrier and pre-exponential factor strongly depend on the temperature and increase with the temperature from 300 to 2100 K. Both Cr and V additions in W has a large consequences on H migrating energy. The energy barriers at any given temperature can be reduced by ∼0.05 and 0.10 eV in W–Cr and W–V alloys, respectively. The current study reveals that vibration free energy plays a decisive role in the formation energy and migrating energy of H with the temperature, while the thermal expansion energy has little influence on the H formation energy and migrating energy with the temperature.

Finite-temperature H behaviors in tungsten and molybdenum: first-principles total energy and vibration spectrum calculations

We have carried out systematic first-principles total energy and vibration spectrum calculations to investigate the finite-temperature H dissolution behaviors in tungsten and molybdenum, which are considered promising candidates for the first wall in nuclear fusion reactors. The temperature effect is considered by the lattice expansion and phonon vibration. We demonstrate that the H Gibbs energy of formation in both tetrahedral and octahedral interstitial positions depends strongly on the temperature. The H Gibbs energy of formation under one atmosphere of pressure increases significantly with increasing temperature. The phonon vibration contribution plays a decisive role in the H Gibbs energy of formation with the increasing temperature. Using the predicted H Gibbs energy of formation, our calculated H concentrations in both metals are about one or two orders of magnitude lower than the experimental data at temperature range from 900 to 2400 K. Such a discrepancy can be reasonably explained by the defect-capturing effect.

Photoluminescence from Ordered Ge/Si Quantum Dot Groups Grown on the Strain‐Patterned Substrates

The photoluminescence (PL) properties of combined Ge/Si structures representing a combination of large (200–250 nm) SiGe disk‐like quantum dots (QDs) and the groups of smaller (40–50 nm) laterally ordered QDs grown on the nanodisk surface are studied. The experimental results are analyzed basing on the calculations of energy spectra, electron and hole wave functions. It is found that the strain accumulation in multi‐layered structure is the main factor providing the room temperature PL. The new type of QD structures that should provide the observation of enhanced PL from SiGe QDs at room temperature is proposed. The structures represent the stacked compact groups of laterally aligned QDs incorporated in Si at the distance 30–40 nm above the large nanodisks.

Presupernova Neutrinos: Realistic Emissivities from Stellar Evolution

Abstract We present a new calculation of neutrino emissivities and energy spectra from a massive star going through the advanced stages of nuclear burning (presupernova) in the months before becoming a supernova. The contributions from β decay and electron capture, pair annihilation, plasmon decay, and the photoneutrino process are modeled in detail, using updated tabulated nuclear rates. We also use realistic conditions of temperature, density, electron fraction, and nuclear isotopic composition of the star from the state-of-the-art stellar evolution code MESA. Results are presented for a set of progenitor stars with mass between and . It is found that β processes contribute substantially to the neutrino emissivity above realistic detection thresholds of few MeV, at selected positions and times in the evolution of the star.