Isotopic Cross Sections Research Articles

14.8 MeV Neutron Activation Cross Section Measurements for Ge Isotopes

The cross sections of Ge isotopes were measured with the activation method at 14.8 MeV neutron energy. The quasi-monoenergetic neutron beams were produced via the 3H(d,n)4He reaction at the 150 kV J-25 neutron generator of INST, AERE. The characteristics γ-lines of the product nuclei were measured with a closed end coaxial 17.5 cm2 high purity germanium (HPGe) detector gamma ray spectroscopy. The cross sections were determined with reference to the known 27Al(n,α)24Na reaction. Cross section data are presented for 72Ge(n,p)72Ga, 74Ge(n,α)71mZn and 76Ge(n,2n)75m+gGe reactions. The cross section values obtained for the above reactions were 24.78±1.75 mb, 1.69±0.11 mb and 860±50 mb, respectively. The results obtained were compared with the values reported in literature as well as theoretical calculation performed by the statistical code SINCROS-II. The experimental data were found fairly in good agreement with the calculated and literature data. Keywords: Activation cross section; Neutron induced reaction; Gamma-ray spectroscopy; 14.8 MeV. © 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v1i2.1532

Isospin dependence of projectile-like fragment production at intermediate energies

The cross sections of fragments produced in 140 $A$ MeV $^{40,48}\mathrm{Ca}+^{9}\mathrm{Be}$ and $^{58,64}\mathrm{Ni}+^{9}\mathrm{Be}$ reactions are calculated by the statistical abration-ablation (SAA) model and compared to the experimental results measured at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The fragment isotopic and isotonic cross section distributions of $^{40}\mathrm{Ca}$ and $^{48}\mathrm{Ca}$, $^{58}\mathrm{Ni}$ and $^{64}\mathrm{Ni}$, $^{40}\mathrm{Ca}$ and $^{58}\mathrm{Ni}$, and $^{48}\mathrm{Ca}$ and $^{64}\mathrm{Ni}$ are compared and the isospin dependence of the projectile fragmentation is studied. It is found that the isospin dependence decreases and disappears in the central collisions. The shapes of the fragment isotopic and isotonic cross section distributions are found to be very similar for symmetric projectile nuclei. The shapes of the fragment isotopic and isotonic distributions of different asymmetric projectiles produced in peripheral reactions are found to be very similar. The similarity of the distributions are related to the similar proton and neutron density distributions inside the nucleus in framework of the SAA model.

Elastic and related transport cross sections for singly charged ion–atom scattering of light metals (Li, Be, B) and hydrogen

Elastic differential and integral cross sections are calculated using a fully quantum-mechanical treatment and new, highly accurate potential curves, for collisions of light metal atoms (Li, Be, B) or their singly charged ions with hydrogen ions or atoms and their isotopes, over the six-decade range of centre-of-mass collision energy 0.0001–100 eV. In addition, the momentum transfer and viscosity cross sections, relevant to transport modelling, have been computed along with results of the classical trajectory Monte Carlo (CTMC) method in an extended energy range (0.01–10000 eV). The CTMC results, though less accurate, also include the inelastic processes of charge transfer, excitation and ionization, enabling improved assessment of the accuracy achieved through comparison of the results of the cross sections obtained with two methods in the overlapping energy range. We also study a fully neutral system, Li + H, using both methods. All of the data calculated here are explicitly tabulated on the World Wide Web for convenient use in plasma modelling and we find a mass-dependent scaling of the cross sections for the hydrogen isotopes.

Dependence of the cross sections for Ir isotopes on the values of Qgg in the heavy ion collision

197Au were irradiated with 47 MeV/u 12C ions. Iridium was produced via the multinucleon transfer reactions in bombardments of 197Au with 12C. and was separated radiochemically from Au and the mixture of the reaction products. The γ radioactivities of Ir isotopes were measured by using a HPGe detector. The production cross sections of Ir isotopes were determined from activities of Ir isotopes at the end of bombardment and the other relative data. It has been found that the cross sections for neutron-rich isotopes of iridium show an exponential dependence on the values of Qgg. Our experimental results also demonstrate lack of correlation between the cross sections and Qgg in the case of neutron-deficient isotopes of iridium. The fact can be explained from that neutron-rich isotopes of iridium were produced in the deep inelastic transfer reactions.

Experimental study of theZr91(n,γ) reaction up to 26 keV

The neutron capture cross sections of the Zr isotopes are relevant to studies in nuclear structure, nuclear astrophysics, and nuclear technology. The valence neutron of Zr91 with respect to the neutron magic nucleus Zr90 has interesting implications for the statistical analysis in the proximity of shell closures. In stellar nucleosynthesis, the Zr isotopes are important for the s-process reaction flow between the Fe seeds and the heavier isotopes. Because of its relatively small (n,γ) cross sections, Zr represents also an interesting structural material for nuclear reactors. For the same reason, these cross sections are difficult to measure and reliable data are sparse. Therefore, the (n,γ) cross sections of the Zr isotopes have been remeasured at the CERN n_TOF facility. Thanks to its high instantaneous flux, good energy resolution, and low background, this facility is particularly suited for the determination of small, resonance-dominated cross sections. In this work, results for the Zr91(n,γ)Zr92 reaction are reported in the neutron energy range from thermal to 26 keV. In this region, accurate data of 157 resonances could be obtained, 33 of these resonances are not present in the main databases and/or were observed for the first time.Received 29 July 2008DOI:https://doi.org/10.1103/PhysRevC.78.045804©2008 American Physical Society

Possibility of production of neutron-rich isotopes in transfer-type reactions at intermediate energies

The production cross sections of neutron-rich isotopes of Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, and Ti in the multinucleon transfer reactions 48 Ca(64 MeV/nucleon, 140 MeV/nucleon) + 181 Ta and 48 Ca(142 MeV/nucleon)+ nat W are estimated. A good agreement of the calculated results with the available experimental data confirms the mechanism of multinucleon transfer at almost peripheral collisions at intermediate energies. The global trend of production cross section with the charge (mass) number of target in reactions with 48 Ca beam is discussed for the future experiments.

Thermal neutron capture cross sections of the palladium isotopes

Precise thermal neutron capture \ensuremath{\gamma}-ray cross sections ${\ensuremath{\sigma}}_{\ensuremath{\gamma}}$ were measured for all elements with $Z=1\text{\ensuremath{-}}83,90$, and 92, except for He and Pm, at the Budapest Reactor. These data were evaluated with additional information from the literature to generate the Evaluated Gamma-ray Activation File (EGAF). Isotopic radiative neutron cross sections can be deduced from the total transition cross section feeding the ground state, ${\ensuremath{\sigma}}_{0}=\ensuremath{\Sigma}{\ensuremath{\sigma}}_{\ensuremath{\gamma}}(\mathrm{GS})$ if the decay scheme is complete. The EGAF file contains partial \ensuremath{\gamma}-ray cross sections for all stable palladium isotopes. None of these decay schemes are complete, although in each case transitions de-exciting low-lying levels are known. We have performed Monte Carlo simulations of the palladium thermal neutron capture decay schemes using the computer code DICEBOX. The simulated populations of low low-lying levels are normalized to the measured ${\ensuremath{\sigma}}_{\ensuremath{\gamma}}$ values from EGAF and the total radiative neutron cross section ${\ensuremath{\sigma}}_{0}$ is obtained. The ${\ensuremath{\sigma}}_{0}$ values derived for the palladium isotopes agree well with previous measurements and were in several cases more precise. Complementary use of \ensuremath{\gamma}-ray cross-section data and Monte Carlo calculations has proven effective in determining both the palladium total radiative cross sections and new nuclear structure information.

Efficient Generation of One-Group Cross Sections for Coupled Monte Carlo Depletion Calculations

Coupled Monte Carlo depletion systems provide a versatile and an accurate tool for analyzing advanced thermal and fast reactor designs for a variety of fuel compositions and geometries. The main drawback of Monte Carlo-based systems is a long calculation time imposing significant restrictions on the complexity and amount of design-oriented calculations. This paper presents an alternative approach to interfacing the Monte Carlo and depletion modules aimed at addressing this problem. The main idea is to calculate the one-group cross sections for all relevant isotopes required by the depletion module in a separate module external to Monte Carlo calculations. Thus, the Monte Carlo module will produce the criticality and neutron spectrum only, without tallying of the individual isotope reaction rates. The one-group cross section for all isotopes will be generated in a separate module by collapsing a universal multigroup (MG) cross-section library using the Monte Carlo calculated flux. Here, the term “universal” means that a single MG cross-section set will be applicable for all reactor systems and is independent of reactor characteristics such as a neutron spectrum; fuel composition; and fuel cell, assembly, and core geometries. This approach was originally proposed by Haeck et al. and implemented in the ALEPH code.Implementation of the proposed approach to Monte Carlo burnup interfacing was carried out through the BGCORE system. One-group cross sections generated by the BGCORE system were compared with those tallied directly by the MCNP code. Analysis of this comparison was carried out and led to the conclusion that in order to achieve the accuracy required for a reliable core and fuel cycle analysis, accounting for the background cross section (σ0) in the unresolved resonance energy region is essential.An extension of the one-group cross-section generation model was implemented and tested by tabulating and interpolating by a simplified σ0 model. A significant improvement of the one-group cross-section accuracy was demonstrated.

Reaction cross sections of carbon isotopes incident on a proton

We systematically study total reaction cross sections of carbon isotopes with $N=6\text{\ensuremath{-}}16$ on a proton target for wide range of incident energies. An emphasis is put on the difference from the case of a carbon target. The calculations include the reaction cross sections of $^{19,20,22}\mathrm{C}$ at $40A$ MeV, the data of which have recently been measured at RIKEN. The Glauber theory is used to calculate the reaction cross sections. To describe the intrinsic structure of the carbon isotopes, we use a Slater determinant generated from a phenomenological mean-field potential, and construct the density distributions. To go beyond the simple mean-field model, we adopt two types of dynamical models: One is a core$+n$ model for odd-neutron nuclei, and the other is a core$+n+n$ model for $^{16}\mathrm{C}$ and $^{22}\mathrm{C}$. We propose empirical formulas which are useful in predicting unknown cross sections.

Neutron capture cross section ofZr90: Bottleneck in thes-process reaction flow

The neutron capture cross sections of the Zr isotopes have important implications in nuclear astrophysics and for reactor design. The small cross section of the neutron magic nucleus Zr-90, which accounts for more than 50 for the stellar s-process, because it acts as a bottleneck in the neutron capture chain between the Fe seed and the heavier isotopes. The same element, Zr, also is an important component of the structural materials used in traditional and advanced nuclear reactors. The (n, gamma) cross section has been measured at CERN, using the n_TOF spallation neutron source. In total, 45 resonances could be resolved in the neutron energy range below 70 keV, 10 being observed for the first time thanks to the high resolution and low backgrounds at n_TOF. On average, the Gamma(gamma) widths obtained in resonance analyses with the R-matrix code SAMMY were 15 these results, the accuracy of the Maxwellian averaged cross section for s-process calculations has been improved by more than a factor of 2.

Neutron capture cross sections of even-mass tellurium isotopes

Neutron capture by the stable even-mass Te isotopes (A=120 to 130) produces in the neighboring odd-neutron isotopes a low-spin ground state (1/2{sup +} or 3/2{sup +}) and a high-spin (11/2{sup -}) isomeric state. Following neutron irradiation of samples of Te of natural isotopic abundance, thermal cross sections and resonance integrals have been determined for all of the odd-mass radioactive ground states and isomers produced in the capture process. By comparing Cd-shielded and unshielded irradiations, it was possible to correct for the effect of capture by epithermal neutrons and so obtain consistent values for the thermal cross sections. Half-lives have been remeasured for {sup 121g,m}Te, {sup 127m}Te, and {sup 131m}Te. The previously observed systematic behavior of the thermal cross sections leading to the low-spin and high-spin states in Sn does not appear for the similar states in the Te isotopes.

Nuclear Physics of thesProcess

AbstractStarting from a sketch of thes-process concept formulated 50 years ago, the nuclear physics data fors-process calculations are briefly reviewed with emphasis on the status of neutron capture cross sections and beta decay rates. Accurate and comprehensive experimental data are mandatory as direct input fors-process calculations as well as for improving the complementary information from nuclear theory. The current challenges of the field are discussed in the light of new or optimized methods and state-of-the-art facilities, indicating the potential for accurate measurements and the possibility to study cross sections of radioactive isotopes. These opportunities will be considerably enriched by the enormous improvements provided by new facilities.

Discrete Gamma Radiation in Interaction of 14.9-MeV Neutrons with Natural Copper

The discrete gamma radiation in the interaction of 14.9-MeV neutrons and a natural copper sample is investigated with the total gamma radiation measurement technique. One hundred seven prompt gamma rays, which come mainly from the reactions (n,n’γ), (n,2nγ), (n,npγ), (n,dγ), (n,pγ) and (n,αγ) of 63Cu and 65Cu, are identified by a high-resolution gamma-ray analysis code. According to the systematic knowledge of 14.9-MeV neutron-induced 63,65Cu(n,xγ) reactions, nine final nuclei are identified, and 139 possible transitions are designated. The differential elemental production cross sections of 107 gamma lines at 90 deg and 79 gamma lines at 55 deg are determined. The nine integral isotopic cross sections of 11 reaction channels including 63Cu(n,n’)63Cu, 63Cu(n,2n)62Cu, 63Cu[(n,np) + (n,d)]62Ni, 63Cu(n,p)63Ni, 63Cu(n,α)60Co, 65Cu(n,n’)65Cu, 65Cu(n,2n)64Cu, 65Cu[(n,np) + (n,d)]64Ni, and 65Cu(n,p)65Ni are also obtained. The present results are in good agreement with some recent experimental and evaluated results.

Fragmentation cross sections and binding energies of neutron-rich nuclei

An exponential dependence of the fragmentation cross section on the average binding energy is observed and reproduced with a statistical model. The observed functional dependence is robust and allows the extraction of binding energies from measured cross sections. From the systematics of Cu isotope cross sections, the binding energies of $^{76,77,78,79}\mathrm{Cu}$ have been extracted. They are $636.94\ifmmode\pm\else\textpm\fi{}0.4,647.1\ifmmode\pm\else\textpm\fi{}0.4,651.6\ifmmode\pm\else\textpm\fi{}0.4$, and $657.8\ifmmode\pm\else\textpm\fi{}0.5$ MeV, respectively. Specifically, the uncertainty of the binding energy of $^{75}\mathrm{Cu}$ is reduced from 980 keV, as listed in the 2003 mass table of Audi, Wapstra, and Thibault to 400 keV. The predicted cross sections of two near drip-line nuclei, $^{39}\mathrm{Na}$ and $^{40}\mathrm{Mg}$ from the fragmentation of $^{48}\mathrm{Ca}$ are discussed.

Cross-section measurements for (n, 2n) and (n, p) reactions on tellurium isotopes in the neutron energy range of 13.5−14.6 MeV

Cross sections for (n,2n) and (n,p) reactions have been measured on tellurium isotopes at the neutron energies of 13.5−14.6 MeV using the activation technique. Data are reported for the following reactions: 120Te(n,2n)119mTe, 120Te(n,2n)119gTe, 122Te(n,2n)121mTe, 122Te(n,2n)121gTe, 124Te(n,2n)123mTe, 128Te(n,2n)127gTe, 130Te(n,2n)129mTe, 120Te(n,p)120mSb, 122Te(n,p)122m+gSb, 124Te(n,p)124m+gSb, 126Te(n,p)126m+gSb and 128Te(n,p)128m+gSb. These new data for the cross sections of tellurium isotopes have smaller uncertainties than those reported in the previous literature. The first data for the 120Te(n,p)120mSb reaction cross sections are presented. In our experiment, natural high-purity tellurium powder was used as target material and the samples were wrapped in cadmium foil during the irradiation so the influence of the (n,γ) reactions of thermal neutrons was reduced to a low level and the interfering reactions were avoided or subtracted. The HPGe detector employed in this work has better resolution than NaI(Tl). Furthermore, while gamma-ray yields were measured and then turned into cross sections using the formula in Sect. 2.2, the most recent and accurate nuclear data available were adopted. These cumulative improvements should make our results more accurate and reliable than those reported in the previous literature. Our results are useful for verifying the accuracy of nuclear models used in the calculation of cross sections and are expected to help new evaluations of the 14 MeV neutron cross sections on isotopes of tellurium.

Influence of the uncertainty of the microscopic cross sections of 238U and plutonium isotopes on the neutron multiplication coefficient in VVÉR

The influence of the uncertainties in the microscopic cross sections of 238U and 239–241Pu on the neutron multiplication coefficient in VVER-1000 is studied. Data on the uncertainty of the cross sections were obtained by analyzing the ENDF/B files of the JENDL 3.3 system using the ERRORJ program. The characteristics of the reactor are calculated using the TRIFON 2.1 and SHERHAN programs. An approach associated with the calculation of the coefficients of sensitivity of the fuel assemblies and the reactor to standard samples in a small-group approximation is used.

Erratum: Systematic analysis of reaction cross sections of carbon isotopes [Phys. Rev. C75, 044607 (2007)

We systematically analyze total reaction cross sections of carbon isotopes with N=6--16 on a $^{12}$C target for wide range of incident energy. The intrinsic structure of the carbon isotope is described by a Slater determinant generated from a phenomenological mean-field potential, which reasonably well reproduces the ground state properties for most of the even $N$ isotopes. We need separate studies not only for odd nuclei but also for $^{16}$C and $^{22}$C. The density of the carbon isotope is constructed by eliminating the effect of the center of mass motion. For the calculations of the cross sections, we take two schemes: one is the Glauber approximation, and the other is the eikonal model using a global optical potential. We find that both of the schemes successfully reproduce low and high incident energy data on the cross sections of $^{12}$C, $^{13}$C and $^{16}$C on $^{12}$C. The calculated reaction cross sections of $^{15}$C are found to be considerably smaller than the empirical values observed at low energy. We find a consistent parameterization of the nucleon-nucleon scattering amplitude, differently from previous ones. Finally, we predict the total reaction cross section of $^{22}$C on $^{12}$C.

Development of a Comprehensive Code for Nuclear Data Evaluation, CCONE, and Validation Using Neutron-Induced Cross Sections for Uranium Isotopes

A new comprehensive code for nuclear data evaluation, CCONE, has been developed for the evaluation of nuclear data for actinides. Neutron-induced reaction cross sections for uranium isotopes (A = 232, 233, 234, 235, 236, 237, 238) were analyzed for incident energies from 10keV to 20MeV using CCONE in order to validate its capability. Reproducibility of the cross section calculations for various reactions such as total, fission, capture, and (n, 2n) was tested using simple parameterization. The calculated cross sections and neutron emission spectra show good agreement with the experimental data.

Progress on the europium neutron capture study using DANCE

The accurate measurement of neutron capture cross sections of the Eu isotopes is important for many reasons including nuclear astrophysics and nuclear diagnostics. Neutron capture excitation functions of 151,153Eu targets were measured recently using a 4π γ-ray calorimeter array DANCE located at the Los Alamos Neutron Science Center for En=0.1–100keV. The progress on the data analysis efforts is given in the present paper. The γ-ray multiplicity distributions for the Eu targets and Be backing are significantly different. The γ-ray multiplicity distribution is found to be the same for different neutron energies for both 151Eu and 153Eu. The statistical simulation to model the γ-ray decay cascade is summarized.

Systematic analysis of reaction cross sections of carbon isotopes

We systematically analyze total reaction cross sections of carbon isotopes with $N=$ 6--16 on a $^{12}\mathrm{C}$ target for wide range of incident energy. The intrinsic structure of the carbon isotope is described by a Slater determinant generated from a phenomenological mean-field potential, which reasonably well reproduces the ground-state properties for most of the even $N$ isotopes. We need separate studies not only for odd nuclei but also for $^{16}\mathrm{C}$ and $^{22}\mathrm{C}$ to improve their wave functions. The density of the carbon isotope is constructed by eliminating the effect of the center-of-mass motion. For the calculations of the cross sections, we take two schemes, the Glauber approximation and the eikonal model using a global optical potential. Both the reaction models successfully reproduce low and high incident energy data on the cross sections of $^{12}\mathrm{C}$, $^{13}\mathrm{C}$, and $^{16}\mathrm{C}$ on $^{12}\mathrm{C}$. The calculated reaction cross sections of $^{15}\mathrm{C}$ are found to be considerably smaller than the empirical values observed at low energy. We find a consistent parametrization of the nucleon-nucleon scattering amplitude, differently from previous ones. Finally, we predict the total reaction cross section of $^{22}\mathrm{C}$ on $^{12}\mathrm{C}$.