Double-differential Cross-section Data Research Articles

Ionization of CH[formula omitted] under fast He-like Si-ion impact

We have studied the absolute double differential cross section (DDCS) of electrons ejected from the methane molecule (CH4) under the impact of highly charged fast projectile ions. The energy and angular distributions of electrons have been measured in interactions with 70 MeV Si12+ ions. These DDCS data together with the derived single differential cross sections and the total cross section (TCS) have been compared with predictions of the continuum distorted wave-eikonal initial state model using different approaches for the molecular orbitals. It has been found that the theories overestimate the measured DDCS values at low ejection energies, which may indicate shortcomings of the model in the case of strong perturbation. At the same time, applying the model to a previous measurement using fast C ions having a lower perturbation strength, excellent agreements have been obtained with the experimental data. Considering the scaling properties, the available TCS data have been plotted with a scaled parameter, namely the perturbation strength, q/v (where q= charge state, v=velocity of the projectile). The KLL Auger e-emission as well as the KLL hyper-satellite peaks are analyzed for different emission angles. The double K-vacancy production shows a considerable enhancement i.e. 37% of the single production cross section which is consistent with some of the recent experiments on K-ionization using x-ray techniques.

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.

Production of high-energy neutrons by interaction of a deuteron beam with matter

Experimental double differential cross section data for neutrons in the high-energy region are still scarce because of the difficulty of producing high-energy neutrons. The present work studies the possibility of producing high-energy neutrons by interaction of a deuteron beam with matter. The Geant4 toolkit is used to simulate the interaction between a deuteron beam and matter. An analytical method is also developed to calculate the neutron yields produced in the interaction of the deuteron beam with matter. The input cross section data are not only taken from the TEDNL-2017 library but are also calculated by the isospin-dependent quantum molecular dynamics model. It is shown that it is possible to produce high-energy neutrons by interaction of a deuteron beam with matter. If one wishes to produce high-energy neutrons, a low-Z target and a small emission angle may be considered. A thin target is a good choice if one wishes to produce neutrons with a smaller energy peak width.

Double-differential cross section for ionization of H2O molecules by 4-MeV/u C6+ and Si13+ ions

Double-differential cross section (DDCS) for electrons ejected in collisions of fast ${\mathrm{C}}^{6+}$ and ${\mathrm{Si}}^{13+}$ projectiles, with a ${\mathrm{H}}_{2}\mathrm{O}$ vapor target, were measured. The electrons were detected over an energy range of 1--600 eV and an angular range of ${20}^{\ensuremath{\circ}}$--${160}^{\ensuremath{\circ}}$. The obtained DDCS spectra, for both the ions, were compared with the CDW-EIS model. Occasional reference has been made to the DDCS data for the case of 3.75-MeV/u ${\mathrm{O}}^{8+}$ colliding on the same molecule for an overall comparison. A reasonable agreement with theoretical results was seen for the case of ${\mathrm{C}}^{6+}$ and ${\mathrm{O}}^{8+}$ projectiles. However, between ${\mathrm{C}}^{6+}$ and ${\mathrm{O}}^{8+}$ projectiles, the deviation from theory is larger for the case of the carbon projectile. Substantial deviation starts to show up for the case of the ${\mathrm{Si}}^{13+}$ projectile. By numerical integration of the DDCS data, the single-differential cross section (SDCS) and total cross section (TCS) were obtained and compared with theoretical models. The present TCS data along with the other available data for $p$, $\mathrm{He}$, and $\mathrm{C}$ ions were plotted together. A clear and gradual deviation from the Bethe-Born predicted ${q}^{2}$ scaling was observed, where $q$ is the projectile charge state. From all the data we find TCS varies as ${q}^{n}$ where $n$ = 1.7 $\ifmmode\pm\else\textpm\fi{}$ 0.1. The provided data set will be valuable in order to help model the radiation damage in hadron therapy, particularly in the Bragg peak region.

Calculated differential and double differential cross section of DT neutron induced reactions on natural chromium (Cr)

Chromium is an important alloying element of stainless steel (SS) and SS is the main constituent of structural material proposed for fusion reactors. Energy and double differential cross section data will be required to estimate nuclear responses in the materials used in fusion reactors. There are no experimental data of energy and double differential cross section, available for neutron induced reactions on natural chromium at 14 MeV neutron energy. In this study, energy and double differential cross section data of (n,p) and (n,α) reactions for all the stable isotopes of chromium have been estimated, using appropriate nuclear models in TALYS code. The cross section data of stable isotopes are later converted into the energy and double differential cross section data of natural Cr using the isotopic abundance. The contribution from compound, pre-equilibrium and direct nuclear reaction to total reaction have also been calculated for 52,50Cr(n,p) and 52Cr(n,α). The calculation of energy differential cross section shows that most of emitted protons and alpha particles are of 3 and 8 MeV respectively. The calculated data is compared with the data from EXFOR data library and is found to be in good agreement.

Extraction of the axial mass parameter from MiniBooNE neutrino quasielastic double differential cross-section data

MiniBooNE charge current quasi-elastic double differential cross section data are analyzed and confronted with predictions of two theoretical nucleus models: Fermi gas and spectral function. The fitting procedure includes the overall flux uncertainty multiplicative factor. In order to obtain a reliable value of the axial mass, bins with large contribution from small momentum transfer are eliminated from the analysis. It is shown that the best fit axial mass value becomes smaller as the momentum transfer cut is more restrictive. For $q_{cut}=500$~MeV/c the obtained values of axial mass are $M_A=1350\pm 66$~MeV for the Fermi gas and $M_A=1343\pm 60$~MeV for the spectral function. The value $M_A=1030$~MeV is excluded on the level which goes far beyond $5\sigma$.

Heavy fragment emission in alpha-induced reactions on aluminum at 60 MeV

The production of intermediate-mass fragments ranging from Z=3 to 8 emitted in the reaction of 60 MeV alpha on an aluminum target has been experimentally studied. The energy spectra of the emitted fragments in the angular range of 20\ifmmode^\circ\else\textdegree\fi{}--130\ifmmode^\circ\else\textdegree\fi{} have been measured and the total production cross sections of each fragment have been estimated from the data. The double-differential cross-section data have been compared with the predictions made using (a) a phenomenological moving source model and (b) a binary fragmentation model. The absolute total emission cross sections for various fragments have been calculated assuming the statistical decay of a fully equilibrated compound nucleus and have been compared with the corresponding experimental estimates. It is found that the exit-channel deformation plays a significant role in the estimation of the Coulomb barrier of the separating nuclei. A theoretical procedure for the estimation of the exit-channel Coulomb barrier for the deformed system has been incorporated in the present calculation.

Development of radiation transport code in three-dimensional (X, Y, Z) geometry for shielding analyses by direct integration method.

A three-dimensional radiation transport code TRISTAN has been developed by applying the method of direct integration to the group-flux calculation in order to enhance the accuracy of shielding analysis. It uses group-angle transfer matrices derived from the double-differential cross section data instead of the Legendre polynomial expansion. In order to improve the numerical accuracy, a technique to separate radiation into two components (the scattered and the unscattered) is adopted and the balance equation of radiation flux is applied to the solution method. Two new techniques, a stratification of the angular mesh and a kind of the forward-adjoint coupling, are introduced to enhance its applicability to the practical shielding analysis. The validity of the TRISTAN is verified by making comparison with the results of the Monte Carlo code MCNP, and with the experimental values in the JRR-4 streaming experiments.

Measurements of Angular Flux on Surface of Li2O Slab Assemblies and their Analysis by a Direct Integration Transport Code “Bermuda”

Angle-dependent neutron leakage spectra above 0.5 MeV from Li/sub 2/O slab assemblies were measured accurately by the time-of-flight method. The measured angles were 0/sup 0/, 12.2/sup 0/, 24.9/sup 0/, 41.8/sup 0/ and 66.8/sup 0/. The sizes of Li/sub 2/O assemblies were 31.4 cm in equivalent radius and 5.06, 20.24 and 40.48 cm in thickness. The data were analyzed by a new transport code ''BERMUDA-2DN''. Time-independent transport equation is solved for two-dimensional, cylindrical, multi-regional geometry using the direct integration method in a multi-group model. The group transfer kernels are accurately obtained from the double-differential cross section data without using Legendre expansion. The results were compared absolutely. While there exist discrepancies partially, the calculational spectra agree well with the experimental ones as a whole. The BERMUDA code was demonstrated to be useful for the analyses of the fusion neutronics and shielding.

Compound Nucleus Contributions in the Differential and Double Differential Cross-Sections for24Mg(d, p γ)25Mg

The examination of published differential and double differential cross section data for the reaction 24 Mg(d, p γ) 25 Mg at 10 MeV shows that the angular distributions can not be reproduced completely by DWBA calculations, particularly at backward angles. This discrepancy may be due to the presence of compound nucleus (CN) contributions. The CN contributions calculated from Hauser-Feshbach theory have been added to the double differential cross sections calculated from DWBA. It has been shown that the fits to the double differential cross sections are markedly improved, like the differential cross sections, by the addition of CN contributions. Moreover the differential cross section of the levels with spin 7/2 + and 9/2 + and double differential cross sections for 3 →0 and 8 →3 correlations, which do not show the stripping pattern are close to those predicted by HF calculations. Thus it is possible to account for the strength of the levels, which do not have the obvious direct stripping pattern, simply b...

Slow neutron scattering by solid CH 4 and NH 4I.

In order to get information on the rotational freedom of the molecule, cross section formulae are evaluated, using the phonon expansion for the translational modes combined with the assumption of free rotation. The results are applied to analyze neutron scattering data in the case of highest temperature modification of the solid methane and ammonium iodide. Comparison of theoretical calculations and experiments has shown, that 1. 1. data of neutron elastic form factor measurements are not in conflict with a calculation based on the hypothesis of free rotation in room temperature ammonium iodide; 2. 2. double differential cross section data cannot be fitted assuming free rotation in solid methane at 86°K, thus such an experiment clearly exhibits rotational hindrance of the CH 4 molecule.