Level Density Models Research Articles

Production cross-section calculations of some strontium isotopes via (p,x) reactions on natural abundance rubidium using different level density models

Abstract The cross-section, a measure of the probability that a nuclear reaction will occur, needs to be calculated properly. The level density model used in the computations is one of several factors which may affect the theoretical value of the cross-section in a nuclear reaction. In this study, it is aimed to investigate the influence of level density models on the cross-section calculations in the production of some strontium isotopes from the natural abundance of rubidium by proton induced reactions. To this end, calculations have been made by triggering the six level density models that can be used in the TALYS code, one after the other. To allow a visual comparison of the effects of the level density models, the obtained calculation outputs and the experimental results from the literature have been plotted together. Furthermore, numerical comparisons have been made with the calculated values of a deviation factor.

Activation cross section for the [formula omitted] and [formula omitted] reactions on 103Rh, 48Ti and 52Cr from reaction threshold up to 25 MeV energy region

Activation and off-line γ-ray spectrometric methods were used to measure the ground and isomeric state (n,2n) reaction cross section for 103Rh at two different neutron energies. The standard 27Al (n,α)24Na reference reaction was used to normalise neutron flux. The proton beam from the 14UD BARC-TIFR Pelletron facility in Mumbai, India, was utilised to create high-energy quasi-monoenergetic neutrons via the 7Li (p,n) reaction. Statistical model calculations including the level density, pre-equilibrium and optical potential model were performed using the TALYS (ver. 1.95) and EMPIRE (ver. 3.2.3) reaction codes. In addition, because of considerable discrepancies in measured data, the literature (n,p) reaction cross section of 52Cr and 48Ti targets were examined theoretically in the present work. The measured cross sections are discussed and compared with the latest evaluated data of the FENDL-3.2b, CENDL-3.2, TENDL-2019, JENDL-5.0, and ENDF/B-VIII.0 libraries, and experimental data based on the EXFOR compilation. The theoretical investigation of the (n,2n) reaction cross section was performed for the ground and isomeric state for the first time from reaction threshold to 25 MeV energies. The experimental data corresponding to the ground, isomeric state and isomeric ratio were reproduced consistently by the theoretical calculations. The present experimental results are good with certain literature data and theoretical values.

Spectroscopic analysis of photoneutrons in intense [formula omitted]-ray background

CR-39 SSNTD is used to measure the photoneutron spectrum produced by a medical linear accelerator in an intense γ-ray background. The spectroscopic resolution and the neutron detection threshold have been improved by introducing the event selection criteria, based on the track diameter-brightness correlation. The CR-39 detector’s efficiency is determined by adapting the 1H(n,el) cross section from the ENDF/B-VIII.0 evaluations. The measured spectrum was reproduced through Talys-1.96 calculations by implementing the Gogny-HFB microscopic level density model.

Calculation of double differential neutron cross-sections of 56Fe and 90Zr isotopes

This study is concerned with the calculations of double differential neutron cross-sections of the structural fusion materials of 56Fe and 90Zr isotopes that are bombarded with protons. Calculations were performed using the level density models of the TALYS 1.95 code and PHITS 3.22 Monte Carlo code. Constant Temperature Fermi Gas, Back Shifted Fermi Gas, and Generalized Super Fluid Models were employed for level density models. Calculations were performed at 22.2 MeV proton energies. Calculations were compared with the experimental data taken from Experimental Nuclear Reaction Data (EXFOR). In conclusion, the results showed that the level density model results of TALYS 1.95 codes for the double differential neutron cross-sections of 56Fe and 90Zr isotopes are consistent with experimental data. On the other hand, PHITS 3.22 results gave lower cross-section values than experimental data at 120 and 150°.

Systematic study of (p, n) and (p, 2n) reactions on 110Cd

Standard activation analysis technique with γ ray spectroscopy via off-line mode was utilized for reaction cross section estimation. The proton beam was transported from the BARC-TIFR accelerator and targeted on the natCd target. The 16 MeV proton beam irradiated the sample, and Copper foil was utilized as an energy degrader. The activation cross sections were estimated for 110Cd(p, n) reaction for the ground state (Jπ = 7+) population of 110In nucleus and 110Cd(p, 2n)109In reaction at 14.14 MeV of proton energy. Along with experimental measurements, the theoretical study has been carried out for ground and metastable states population by utilizing the nuclear model code TALYS-1.95, EMPIRE-3.2.3, and ALICE-2014 for both reaction channels. The estimated cross sections are valuable for the improvement of theoretical nuclear model codes for a comprehensive knowledge of nuclear reaction mechanisms. The produced isotopes 109,110In have significant importance in Positron Emission Tomography (PET) studies. The present study is a dive into the phenomenological and microscopic level density models of different nuclear model codes in predicting excitation functions.

Investigation of charged-particle induced reactions on 27Al up to 100 MeV leading to the formation of 22Na and 24Na

Abstract Studies using theoretical models are of great importance for understanding of reaction process and its nature. In this study, nuclear level density model calculations of the cross sections of 27Al are investigated by using TALYS 1.96 computer code. The cross section calculations of 27Al(α,x)22Na, 27Al(α,x)24Na, 27Al(3He,x)22Na, 27Al(3He,x)24Na, 27Al(p,x)22Na and 27Al(p,x)24Na reactions were carried out for incident particle energy up to 100 MeV. In these calculations, four nuclear level density models, namely constant temperature model (CTM), back-shifted Fermi gas model (BSFGM), generalized superfluid model (GSM) and recently proposed semi-classical Fermi gas model (CSCFGM) are used. This model is developed using the simplest model BSFGM. The most obvious difference between CSCFGM and other models is the inclusion of the collective effects in the base of the formulation. The predicted results are discussed and compared with each other and the available experimental data taken from EXFOR library. In order to better evaluate the model results, chi-squared values are calculated and compared with each other for all analyzed reactions. According to the chi-squared results, CSCFGM gives closer predictions to the experimental data compared with the other models in 4 of the 6 analyzed reactions. Therefore, in this study, it is presented that this model can be reliably used in the reaction cross section calculations.

Decay Times of Compound Nuclei in Heavy Ion Fusion Reactions

The decay time of the compound nuclei has been studied using different statistical models. In the present work, we have improved the back-shifted microscopic level density model by including the pairing effect, an angular momentum-dependent moment of inertia, fission barriers, and a dynamical effect. The decay time of the compound nuclei is evaluated with and without dynamical effect and also compared with various statistical models and available experiments. It is also observed that the decay times of the compound nuclei formed during inverse kinematics is found to be larger when compared to direct kinematics at same excitation energy. Furthermore, the possible fission fragments have been identified using modified generalised liquid drop model. The identified fission fragments are compared with available experiments. The failure of the experiments to synthesize the superheavy element Z = 119 and 120 may be confirmed by the identification of fission fragments in these reactions. The predicted decay times of the compound nuclei and possible fission fragments gives a complete over view of failure of reactions to synthesize the superheavy element Z = 119 and 120.

An investigation of the effects of optical model potentials and level density models on the calculation of excitation function for the production of medical isotopes $$^{68}Ge$$ and $$^{82}Sr$$ through alpha and proton induced nuclear reactions

An investigation of the effects of optical model potentials and level density models on the calculation of excitation function for the production of medical isotopes $$^{68}Ge$$ and $$^{82}Sr$$ through alpha and proton induced nuclear reactions

Cross-Section Calculations for the Production of 123I and 124I Radioisotopes via (p,n) and (p,2n) Reactions Using Collective Nuclear Level Density Model

Some isotopes such as 123I and 124I are useful in medical science, and thus, the production of these isotopes has great importance. Iodine-123 is the gamma-emitting radioisotope of radioiodine, and 124I is the long-lived positron-emitting radioisotope of radioiodine, and they have applications in diagnosis via both Single Photon Emission Computed Tomography (SPECT)/Positron Emission Tomography (PET) and radiotherapy. Therefore, many theoretical and experimental studies are performed for these isotopes. In this study, the cross sections of the 123Te(p,n), 124Te(p,n), and 124Te(p,2n) reactions up to 31 MeV, where 123I and 124I can be produced, are calculated by importing the Collective Semi-Classical Fermi Gas Model (CSCFGM) to the Talys 1.96 computer code. The predictions are compared with the default theoretical calculations of Talys 1.96 and existing experimental data taken from the EXFOR library. The results are in good agreement with the experimental data, and therefore, CSCFGM looks to be a useful tool for predicting the production reactions of some therapeutic isotopes.

Theoretical consideration of isomeric ratios in some photonuclear reactions induced by bremsstrahlung with endpoint energy in giant dipole resonance region using Talys 1.95 code

Isomeric ratios of isomeric pairs produced by photonuclear reactions (γ, n) on Se, Ce, Eu and Hg targets induced by bremsstrahlung with endpoint energies in the giant dipole resonance region have been theoretically calculated using TALYS 1.95 code in combination with Geant4 simulation. The computed isomeric ratios as a function of the bremsstrahlung endpoint energies in the range of 10 to 25 MeV resulted from convolution between calculated differential cross-sections using six level density models available in TALYS 1.95 and the bremsstrahlung spectra simulated by the GEANT4 toolkit. Moreover, for each level density model, eight gamma strength functions have been employed. The calculated results are compared to the experimental data in the existing literature for Talys 1.95 model evaluation.

Extracting model-independent nuclear level densities away from stability

The nuclear level density (NLD) is a fundamental measure of the complex structure of atomic nuclei at relatively high energies. Here we present the first model-independent measurement of the absolute partial NLD for a short-lived nucleus. For this purpose we adapt the recently introduced ``shape method'' for $\ensuremath{\beta}$-decay experiments, providing the shape of the $\ensuremath{\gamma}$-ray strength function for exotic nuclei. In this work, we show that combining the shape method with the $\ensuremath{\beta}$-Oslo technique allows for the extraction of the NLD of the populated states without the need for theoretical input. This development opens the way for the extraction of experimental NLDs far from stability with major implications in astrophysical and other applications. We benchmark our approach using data for the stable $^{76}\mathrm{Ge}$ nucleus, finding excellent agreement with previous experimental results. In addition, we present new experimental data and determine the absolute partial level density for the short-lived $^{88}\mathrm{Kr}$ nucleus. Our results suggest a fivefold increase in the NLD for the case of $^{88}\mathrm{Kr}$, compared to the recommended values from semimicroscopic Hartree-Fock Bogoliubov calculations recommended by the RIPL3 nuclear data library. However, our results are in good agreement with other semimicroscopic level density models. We demonstrate the impact of our method on the $^{87}\mathrm{Kr}(n,\ensuremath{\gamma}$) neutron capture rate and show that our experimental uncertainties for NLDs fulfill the requirements needed for astrophysical calculations predicting $r$-process abundances.

Measurement and calculation of isomeric cross section ratios for the natW(3He, x)184m,gRe reactions

Excitation functions for the natW(3He, x)184m,gRe nuclear reactions were measured from respective thresholds up to 55 MeV by using a conventional stacked-foil activation technique combined with HPGe γ-ray spectroscopy. Individual cross-section values for the production of 184mRe and 184gRe were separated using a proper mathematical method based on their interference-free characteristic gamma lines and the data are reported here for the first time. The default parameters of recently developed nuclear model code TALYS-1.96 were found to be unable to reproduce the excitation functions, hence cannot provide 184mRe/184gRe isomeric cross-section ratios consistent with the experimental results. However, the adjustment of the level density model and optical model potentials together with some other parameters, such as the spin cut-off parameter, were found to be effective to reproduce the measured excitation functions. A similar parameter adjustment may be useful to reproduce the excitation functions of like unusual isomeric pairs, especially when the metastable state is longer-lived than the ground state.The reported cross-sections and the model calculation show interesting in the understanding of the nuclear reaction mechanisms as well as for the improvement of nuclear model codes for accurate prediction of nuclear reaction cross-sections where the experimental data are scarce, or an expensive experiment is required to obtain experimental data.

Investigation of the Cross Sections and Effect of Level Density Models for Platinum Element

In cases where experimental studies cannot be carried out and there is no experimental data with it, studies carried out with theoretical models shed light on the researchers' knowledge of different data. The most important of this data is the measurable or calculatable influence cross-section value, which is defined as the probability of a reaction occurrence. Examining the possible effects of different models in the calculation of the effect section is important for the correct calculation of this value. The most important data, the cross section of influence, has taken its place in the radioisotope world as well as in many areas of nuclear physics. With developing technology and advancing science, radioisotopes have widespread and diversified uses. Most commonly, radioisotopes are used in medical diagnosis and treatment applications. Among the many radioisotopes used for this purpose, 191-199Au radioisotopes are also important in terms of both their benefits and characteristics in medical applications. In this respect, the study aimed to investigate the effects of different nuclear level density models in production impact cross-section calculations of 191-199Au radioisotopes with deuteron reference. Theoretical cross sections using the TALYS code have been simulated for all isotopes. The results of the calculations obtained were compared with each other and with the experimental data in the literature and it was aimed to determine the most compatible level density models according to the reaction situations examined.

Farklı seviye yoğunluk modelleri kullanılarak reaksiyon eşik değerinden 20 MeV’e kadar Paladyum izotoplarının (n,2n), (n,p) ve (n,) tesir kesitlerinin hesaplanması

Bu çalışmada, Paladyum izotoplarının (102,104,106,108,110Pd) (n,2n), (n,p) ve (n,) reaksiyon tesir kesitleri Empire-3.2.3 (Malta) istatistiksel model kodu kullanılarak reaksiyon eşik değerinden 20 MeV’e kadar nötron enerjilerinde hesaplanmıştır. Hesaplamalar, dört farklı nükleer seviye yoğunluğu modeli (Genelleştirilmiş Süper Akışkan modeli, Gelişmiş Genelleştirilmiş Süper Akışkan modeli, Gilbert-Cameron modeli ve Hartree-Fock-Bogoliubov mikroskobik modeli) kullanılarak yapılmıştır. Hesaplardan elde edilen sonuçlar, EXFOR kütüphanesinde bulunan deneysel verilerle ve ENDF kütüphanesinden alınan ENDF/B-VIII.0 (USA,2018), TENDL-2019 (TALYS, 2019) ve JENDL-5 (Japan,2021) değerlendirilmiş verilerle karşılaştırılmıştır. 14.5 MeV civarında deneysel ve değerlendirilmiş verilerle karşılaştırıldığında, sonuçlar genel olarak tutarlı bir uyum göstermektedir.

An Investigation on Production Routes of $${}^{\mathbf{230}}$$U Radioisotope Used in Targeted Alpha Therapy by Different Level Density Models

An Investigation on Production Routes of $${}^{\mathbf{230}}$$U Radioisotope Used in Targeted Alpha Therapy by Different Level Density Models

Investigation of the production routes of Palladium-103 and Iodine-125 radioisotopes

The most commonly used radioisotopes are Palladium-103 (103Pd) and Iodine-125 (125I) for interstitial application in brachytherapy. In the present study, different production routes of 103Pd and 125I have been investigated. The different level density and optical models of the TALYS 1.95 have been used to determine 103Rh(p,n)103Pd, 103Rh(d,2n)103Pd, and 126Te(p,2n)125I production cross-sections. Besides, activity calculations and production yields have been obtained. The data from the present work have been compared with the values based on the TALYS 1.95 code and with the experimental data from the EXFOR compilation.

Measurement of the integrated cross section of 110Pd(γ,n)109mPd, 110Pd(γ,n)109gPd, and 110Pd(γ,x)108mRh reactions with 70 MeV bremsstrahlung

We measured the integrated cross sections of 110Pd(γ,n)109mPd, 110Pd(γ,n)109gPd and 110Pd(γ,x)108mRh reactions in the energy range from the reaction threshold to 70 MeV bremsstrahlung end-point energy. Measurements were performed by means of the activation method in combination with off-line γ-ray spectrometry. The induced activity of radionuclides was measured with a high-purity germanium (HPGe) detector and necessary corrections for γ-ray interferences were made. The integrated cross section of the studied reactions was measured relative to that of the monitor reaction 27Al(γ,2pn)24Na. Current results are compared with theoretical predictions using the TALYS-1.9 statistical nuclear model code. Calculations were performed using six different level density models in combination with eight γ-strength functions to determine which combinations best fit the experimental results. The present results are measured for the first time.

Comprehensive test of nuclear level density models

For the last two decades, experimental information on nuclear level densities for about 60 different nuclei has been obtained on the basis of the Oslo method. While each of these measurements has been typically compared to one or a few level density models, a global study including all the measurements has been missing. The present study provides a systematic comparison between Oslo data and six global level density models for 42 nuclei for which $s$-wave resonance spacings are also available. We apply a coherent normalization procedure to the Oslo data for each of the six different models, all being treated on the same footing. Our quantitative analysis shows that the constant-temperature model presents the best global description of the Oslo data, closely followed by the mean-field plus combinatorial model and Hartree-Fock plus statistical model. Their accuracies are quite similar, so that it remains difficult to clearly favour one of these models. When considering energies above the threshold where the experimental level scheme is complete, all the six models are shown to lead to rather similar accuracies with respect to Oslo data. The recently proposed shape method can, in principle, improve the situation since it provides an absolute estimate of the excitation-energy dependence of the measured level densities. We show for the specific case of $^{112}\mathrm{Cd}$ that the shape method could exclude the Hartree-Fock plus statistical model. Such an analysis remains to be performed for the bulk of data for which the shape method can be applied to the Oslo measurements before drawing conclusions on the general quality of a given nuclear level density model.

Photonuclear reactions natNi(γ,xn)57Ni and natNi(γ,xn)56Ni in the energy range Eγmax = 35–94 MeV

The total bremsstrahlung flux-averaged cross-sections 〈σ(Eγmax)〉 for the photonuclear reactions natNi(γ,xn)57Ni and natNi(γ,xn)56Ni have been measured in the range of end-point energies Eγmax = 35–94 MeV. The experiments were performed with the beam from the NSC KIPT electron linear accelerator LUE-40 with the use of the activation and off-line γ-ray spectrometric technique. The calculation of the flux-average cross-sections 〈σ(Eγmax)〉th was carried out using the partial cross-section values σ(E) computed with the TALYS1.95 code for the level density models LD1-6 and bremsstrahlung γ-flux calculated by GEANT4.9.2. The obtained experimental results are compared both with the theoretical calculation 〈σ(Eγmax)〉th and with the data available in the literature. The obtained 〈σ(Eγmax)〉 values expand the energy range of previously known experimental data.

Kollektif Etkilerin Nötron Yakalama Reaksiyon Tesir Kesiti Üzerindeki Rolü

The neutron capture reaction is one of the important reactions that provides the determination of the structural properties of the nucleus and detailed information about the capture reaction mechanisms. In this study, cross section values of 89Y(n,g)90Y reaction, which is a neutron capture reaction, were calculated with TALYS computer code up to 10 MeV incident particle energy using different level density models. In the calculations, back-shifted Fermi gas model (BSFGM), constant temperature model (CTM), generalized superfluid model (GSM), and collective semi-classical Fermi gas model (CSCFGM) were preferred. The obtained results were compared with the data taken from the experimental database. In addition, the quality factors of the models were presented in the table. As a result of the calculations, it has been presented that the CSCFGM, which takes the collective effects into account basically, is more successful model to reproduce the experimental data and that the collective effects play a dominant role on the neutron capture reaction cross sections. Therefore, it has been demonstrated that CSCFGM is a model, which can be used for neutron capture reaction analyses in the future.