Investigation of gamma strength functions and level density models effects on photon induced reaction cross-section calculations for the fusion structural materials 46,50Ti, 51V, 58Ni and 63Cu

Predicting (n,3n) nuclear reaction cross-sections using XGBoost and Leave-One-Out Cross-Validation

Accurately predicting nuclear reaction cross-sections is crucial for advancing various fields, including nuclear medicine, energy production, and materials science. This study aims to address the challenges associated with predicting (n ,3n) nuclear reaction cross-sections by developing a robust machine learning (ML) model based on the XGBoost (eXtreme Gradient Boosting) algorithm. By leveraging a comprehensive dataset of experimental cross-sectional values, the study demonstrates the potential of ML to overcome limitations in existing theoretical and empirical approaches. LOOCV (Leave-One-Out Cross-Validation) was employed for feature selection and hyperparameter optimization to ensure the reliability of the model. The dataset was meticulously prepared by normalizing values and addressing missing data, which contributed to robust model training. XGBoost's ability to handle complex, non-linear relationships enabled it to provide accurate predictions that closely align with experimental data, as evaluated through key metrics such as Mean Squared Error (MSE) and Mean Absolute Error (MAE), and reduced Chi-Square. To validate the model's accuracy, its predictions were compared with calculations from the TALYS 1.95 nuclear reaction code, TENDL and phenological model. The results highlight the efficacy of XGBoost in improving prediction accuracy, offering a novel approach to solving complex challenges in nuclear data analysis.

A new empirical formula for calculation of (n,3n) cross sections of heavy mass nuclei in the energy region 22-27.5 MeV

In this paper we want to study (n,3n) reactions using an empirical formula derived on the basis of the statistical model considering reaction Q-value dependence. This formula was obtained by taking into account the exponential dependence on asymmetry parameter (N-Z)/A for neutron-induced reactions in Levkovskii's empirical formula. In addition, the present formula depends also on incident energy En, reaction Q-value and symmetry term (N-Z)2/A. Herein, a new analysis of experimental data of (n,3n) reactions in the energy region 22-27.5 MeV was carried out for quick estimation of cross sections of the heavy mass isotopes of odd Z-even N nuclides in the region of A = 151 to 209. We observed a good agreement of the experimental cross section data with the calculations performed using the present empirical formula.

(n,2n) cross section calculations for tungsten, tantalum and osmium nuclei

Tungsten, tantalum and osmium are important alloying elements in the nuclear technology research and development, particularly in nuclear fission/fusion power plant material applications. So, data results of the cross sections and emission spectra of neutron-induced reactions are required to predict nuclear responses in these elements. However, the cross sections measurements of (n,2n) reactions on tungsten, tantalum and osmium isotopes are rather limited in the literature. In this case, theoretical approaches are often used for obtaining the cross section data. In this article, theoretical (n,2n) cross sections on 180,182-184,186W, 181Ta and 186,192Os target nuclei are calculated up to 20 MeV energy, using the simulation codes TALYS 1.95, ALICE/ASH and CEM03.01. Further, the empirical (n,2n) systematics based on the statistical model have been used for predicting the cross section data at ∼14 MeV incident neutrons. The present results from the empirical systematics and model-based calculations are also compared with the literature experimental data, and JENDL-5.0, ENDF/B-VIII, JEFF3.3 and TENDL-2021 libraries. This paper can provide a contribution to complete description of the (n,2n) reactions considering the lack of experimental cross section data.

Lithium–lithium fusion evaporation research

In this study we have explored 6Li + 7Li fusion evaporation reactions cross sections dependencies on both nuclear level density and various spin combination effects. The reaction cross section was calculated in the energy range of 0.1–16 MeV projectile of 6Li on the fixed target of 7Li. The excited compound nucleus (13C) can decay into various channels, and its decay rate in any given channel is proportional to the available phase space, i.e., the corresponding level density of it which is explained in the present study. In the present study, LISE++, PACE4, NRV and GEMINI codes were used to determine cross section of evaporation residues cross sections of 13C.

Effects of deuteron optical models on the cross-section calculations of deuteron induced reactions on natural germanium

A common feature of scientific studies is that when experimental observation data are not available, theoretical calculations are used to obtain information about the subject under investigation. In this context, many parameters and theoretical models have been developed that can be used in nuclear physics studies just as it is in other branches of sciences. It is intended that by doing so, theoretical models can be improved using recent experimental data while also learning about outcomes where experimental data is unavailable or difficult to access. Among the many theoretical models available, there are also deuteron optical models whose effects are examined in this study. The objective of this study is to examine the effects of different deuteron optical models on the cross-section calculations of deuteron induced reactions on natural germanium. The cross-section values of ^natGe(d,x)⁷⁰As, ^natGe(d,x)⁷¹As, ^natGe(d,x)⁷²As, ^natGe(d,x)⁷³As, ^natGe(d,x)⁷⁴As and ^natGe(d,x)⁷⁶As reactions were calculated using five deuteron optical models in the TALYS code's v1.95 for this aim, and the results were compared to the experimental data available in the database known as Experimental Nuclear Reaction Data (EXFOR) library. Graphics and quantitative analyses were also used to present the findings and interpretations of the outcomes.

Cross sections of 56Fe(n, p)56Mn, 55Mn(n, p)55Cr, 52Cr(n, p)52V, 56Fe(n, α)53Cr, 55Mn(n, α)52V and 52Cr(n, α)49Ti reactions using phenomenological level density models from threshold to 20 MeV

⁵⁶Fe(n,p)⁵⁶Mn, ⁵⁵Mn(n,p)⁵⁵Cr, ⁵²Cr(n,p)⁵²V, ⁵⁶Fe(n, α)⁵³Cr, ⁵⁵Mn(n, α)⁵²V and ⁵²Cr(n, α)⁴⁹Ti reactions are evaluated using four phenomenological nuclear level density models from reaction threshold to 20 MeV. The calculated data is compared with the experimental nuclear reaction data from EXFOR database. Statistical factors H, D and R are computed to identify the best fit. Level density parameters are adjusted for further improvement of the fitting. Back shifted Farmi-gas model gives a resemblance of neutron-induced ⁵⁶Fe, ⁵⁵Mn and constant temperature Fermi-gas model gives a closeness for ⁵²Cr reaction with our new parameter values.

An investigation of the effects of level density models and alpha optical model potentials on the cross-section calculations for the production of the radionuclides 62Cu, 67Ga, 86Y and 89Zr via some alpha induced reactions

Theoretical studies via nuclear reaction models have an undeniable importance and impact in terms of better understanding of reaction processes and their nature. In this study, by considering the importance of these models and the medical radionuclides, the effects of six level density models and eight alpha optical model potentials on the cross-section calculations for the production of the radionuclides 62Cu, 67Ga, 86Y and 89Zr via 59Co(α,n)62Cu, 60Ni(α,np)62Cu, 65Cu(α,2n)67Ga, 64Zn(α,p)67Ga, 85Rb(α,3n)86Y, 86Sr(α,n)89Zr, 87Sr(α,2n)89Zr and 88Sr(α,3n)89Zr reactions were investigated. Calculations for each reaction route were performed by using the TALYS v1.9 code. The most consistent model with the literature data taken from the Experimental Nuclear Reaction Database (EXFOR), was identified by using the reduced chi-squared statistics in addition to an eyeball estimation. Also, the effects of combinational use of selected models and potentials were investigated by comparing the calculational results with the experimental data.

Analysis of neutron induced (n,γ) and (n,2n) reactions on 232Th from reaction threshold to 20 MeV

Excitation functions for ²³²Th(n,γ) and ²³²Th(n,2n) reactions from reaction threshold to 20 MeV were calculated using TALYS-1.9 nuclear code by invoking suitable options for the level densities, optical model potentials, pre-equilibrium effects and γ-ray strength functions. In earlier studies, theoretical plots for ²³²Th(n,γ) and ²³²Th(n,2n) reaction cross-sections were obtained by using EMPIRE 3.2 and TALYS 1.9 codes with default parameters, however none of the reported plots could match with the corresponding experimental cross-sections reported in EXFOR data particularly between 14-20 MeV. The results of the present study reveal that by using a combination of specific input parameters in TALYS 1.9 code, the theoretical evaluation of the cross sections favour a higher pre-equilibrium rate for the harder spectrum. Moreover the estimated cross-sections match fairly well with the corresponding experimental data (EXFOR database) as well as with the evaluated data files (ENDF/VII.0, JENDL-4.0). The results of the present study are important for the validation of nuclear model approaches with increased predictive power for (n,xn) cross-sections and particularly for the application of thorium based fuel in Accelerator-Driven Sub-critical System.