Photoneutron Reaction Cross Sections Research Articles

Reliability of 51V partial photoneutron reaction cross sections obtained using bremsstrahlung

Reliability of 51V partial photoneutron reaction cross sections obtained using bremsstrahlung

Cross Sections of Partial Photoneutron Reactions on $${}^{59}$$Co in Experiments with Bremsstrahlung

Cross Sections of Partial Photoneutron Reactions on $${}^{59}$$Co in Experiments with Bremsstrahlung

Cross Sections of Partial Photoneutron Reactions in Experiments on Beams of Bremsstrahlung

Cross Sections of Partial Photoneutron Reactions in Experiments on Beams of Bremsstrahlung

Similarity and distinctions of <sup>58, 60</sup>Ni photodisintegration processes

Reliability of (γ, 1n) and (γ, 2n) reactions cross sections for 58, 60Ni obtained in experiments carried out on the beams of bremsstrahlung and quasimonoenergetic annihilation photons was investigated using objective physical criteria. It was found that data of the first type experiment do not satisfy those criteria and definitely are not reliable. At the same time there are serious doubts in reliability of the data obtained in the second type experiment. New partial photoneutron reaction cross sections on 58, 60Ni satisfying physical criteria of data reliability were used for analysis of characteristics of both isotope photodisintegration processes. It was obtained that for neighboring (differ in two neutrons) isotopes because of various type systematic uncertainties there are significant disagreements between evaluated and experimental cross sections of various reactions which for isotopes 58Ni and 60Ni are of significant different character. It was shown that the reasons are not only the differences in energy thresholds and absolute values of cross sections of the (γ, 1n), (γ, 1n1p) and (γ, 2n) reactions on 58Ni and 60Ni but significant differences in specific features of neighboring isotopes shell structure also.

Partial photoneutron reaction cross sections in experiments with bremsstrahlung

The analysis of reliability of experimental partial photoneutron reaction cross sections of the reactions (γ, 1n) and (γ, 2n) obtained in experiments on the beams of bremsstrahlung was carried our using the objective physical criteria. In this type of experiments partial reaction cross sections were obtained using the procedure of neutron yield cross section σ(γ, xn) corrections calculated on the base of statistical theory. It was found out that in the cases of 59Co, 58,60Ni, 112, 114, 119Sn reaction cross sections obtained using that procedure do not satisfy the physical criteria of data reliability and therefore are not reliable. At the same time in the cases of 127I, 165Ho и 181Ta one has not any doubts in the data obtained reliability.

Cross sections of partial photoneutron reactions: the problems with reliability and new data

The (𝛾, 1𝑛), (𝛾, 2𝑛) and (𝛾, 3𝑛) reactions cross sections the majority of which were obtained using beams of quasimonoenergetic annihilation photons were discussed. The significant systematic uncertainties of the experimental results far exceeding the achieved statistical accuracy were considered. The results of experiments for about 50 nuclei from 51V to 209Bi were analyzed using objective physical criteria of data reliability. It was shown that in many cases the systematic uncertainties of experimental cross sections were significant and data do not satisfy physical criteria. The experimental theoretical method for evaluation of cross sections satisfying those criteria was described. The systematic uncertainties of several types due to shortcomings of the method of photoneutron multiplicity sorting used in experiments and specific features of neutron detectors used. The new evaluated reliable cross sections of the partial reactions and total photoneutron reaction (𝛾, 1𝑛)+(𝛾, 2𝑛)+(𝛾, 3𝑛) were presented.

Cross Sections of Partial Photoneutron Reactions: Problems of Reliability and New Data

Cross Sections of Partial Photoneutron Reactions: Problems of Reliability and New Data

Reliability of $${}^{{159}}$$Tb Partial Photoneutron Reaction Cross Sections Obtained in Various Experiments

Reliability of $${}^{{159}}$$Tb Partial Photoneutron Reaction Cross Sections Obtained in Various Experiments

New Evaluated Data on Photoneutron Reaction Cross Sections for $${}^{60}$$Ni Nuclei

New Evaluated Data on Photoneutron Reaction Cross Sections for $${}^{60}$$Ni Nuclei

Investigation of level density and Gama strength function for photoneutron reaction in medical linacs in Beamline

Photoneutron reaction cross-sections of 197Au, 187Re, 186W, 181Ta, 94,95,96,97,98,100Mo isotopes were calculated through the TALYS 1.95 nuclear reaction code. The energy range of the incident photon chosen as 7 MeV–30 MeV corresponded to the range of the giant dipole resonance region, which is also an applicable energy range in radiotherapy for many commercial medical linear accelerators. Calculations were performed using three phenomenological level density models available in code, namely the Constant Temperature Fermi Gas Model, the Back-shifted Fermi Gas Model, and the Generalized Superfluid Model. The most convenient level density model for each reaction was chosen using relative variance calculations. The cross-section calculations were repeated using gamma strength function models, Kopecky-Uhl generalized Lorentzian model, Brink-Axel Lorentzian model, and Goriely's hybrid model and the best level density model was kept constant. The calculated data and the experimental data from the international Experimental Nuclear Reaction Data Library were analysed and compared graphically.

Photoneutron production in heavy water reactor fuel lattice from accelerator-driven bremsstrahlung

The coupling of low-energy electron linear accelerators (eLINACs) to a large heavy water reactor is proposed to create an accelerator-driven photoneutron source (ADS). Photoneutron yields of 1012 pn/s per kW of beam power can be achieved in the ADS-CANDU concept where the wide fuel channel spacing of heavy water reactors represents a near-optimal geometry for conversion of accelerator-driven bremsstrahlung into photoneutrons in the heavy water moderator with minimal parasitic attenuation of photons in the fuel channels. Twenty MeV electron beam energy is most efficient at producing photoneutrons despite having the largest fuel channel shielding effect (28% attenuation compared to an infinite heavy water medium). The majority of photoneutrons are produced during source-photon first flights, so the spatial distribution and emission spectra of the ADS in the secondary (γ,n) converter are correlated to the doubly differential angle and energy distribution of the bremsstrahlung emitted from the (e-,γ) converter. Compton-scattered photons and tertiary bremsstrahlung originating from the electron–positron pair and recoil electron secondary particles are important contributors to the photoneutron yield of higher energy eLINACs systems. Photonuclear data for the deuterium photoneutron reaction cross section and secondary electron transport and tertiary bremsstrahlung production physics implemented in Monte-Carlo radiation transport codes can dominate ADS simulation results and are the same magnitude as the physical phenomena such as the fuel channel shielding effect.

Photodisintegration of <sup>127</sup>I: Systematic Uncertainties of Experiments and Data Evaluated Using Physical Criteria

The experimental data for photoneutron reaction cross sections for 127I obtained using beams of quasimonoenergetic annihilation photons and the method of neutron multiplicity-sorting at Livermore (USA) and Saclay (France) were analyzed using objective physical data reliability criteria. It was found that data of both laboratories contain significant systematic uncertainties and therefore are not reliable. New data for partial and total photoneutron reactions cross sections for 127I satisfied physical criteria of data reliability were evaluated using experimental-theoretical method based on both experimental neutron yield reaction cross-section and results of calculation in the combined photonucleon reaction model (CPNRM). The neutron yield reaction cross-section obtained at Saclay (France) was used in evaluation procedure. The newly evaluated cross sections for partial (γ, 1n), (γ, 2n) and (γ, 3n) reactions for 127I were used for discussion in detail the problems of significant disagreements between experimental data for many nuclei obtained at Saclay and Livermore. It was found that systematic uncertainties of experimental data for the (γ, 1n), (γ, 2n), and (γ, 3n) reactions cross sections for 127I obtained at both laboratories are of different nature. One of the reasons of noticeable systematic uncertainties of cross sections obtained are the shortcomings of the procedures used to separate counts into 1n, 2n, and 3n events. At the same time it was shown that the main reason of significant disagreements between new evaluated data and data obtained at Livermore experiment for 127I is the loss of many neutrons from the (γ, 1n) reaction. This situation is analogous to those in Livermore experiments for 75As and 181Ta.

Photo-neutron reaction cross-sections of 59Co in the bremsstrahlung end-point energies of 65 and 75 MeV

The flux-weighted average cross-sections for the 59Co($ \gamma$, xn)58-55Co reactions have been measured with the bremsstrahlung end-point energies of 65 and 75 MeV by using the activation method in combination with the off-line $ \gamma$-ray spectrometry. The measured cross-sections for the $ (\gamma,\mathrm{n})$, $ (\gamma,2\mathrm{n})$, $ (\gamma,3\mathrm{n})$ and $ (\gamma,4\mathrm{n})$ reactions of 59Co at 65 MeV are $ 15.828\pm 0.491$, $ 5.003\pm 0.206$ , $ 0.408\pm 0.047$ and $ 0.039\pm 0.008$ mb, whereas at 75 MeV are $ 15.653\pm 0.361$, 4.965±0.289, $ 0.389\pm 0.062$ and $ 0.036\pm 0.007$ mb, respectively. The 59Co($ \gamma$, xn) reaction cross-sections as a function of photon energy were also theoretically simulated by using TALYS 1.9 code. Then the flux-weighted average cross-sections at different bremsstrahlung energies were obtained from the theoretical values and the literature data at lower energy based on mono-energetic photons. The present data are measured for the first time and are found to be in good agreement with the theoretical flux-weighted average values. It was found that the 59Co($ \gamma$, xn)58-55Co reaction cross-sections increase from their threshold values to a certain bremsstrahlung energy. After a certain energy, the individual 59Co($ \gamma$, xn) reaction cross-sections decrease with the increase of bremsstrahlung energy due to opening of other reaction channels. These two observations indicate the role of excitation energy and its partition in different reaction channels. All the four cobalt isotopes produced from the 59Co($ \gamma$, xn) reactions have medical and other applications.

Theoretical photoneutron cross-section calculations on Osmium isotopes by Talys and Empire codes

In this study, the level density parameter and the gamma ray strength function effects on photoneutron reaction cross-section calculations for Osmium isotopes were investigated by employing available level density models and gamma ray strength functions within Talys v1.8 and Empire v3.1 nuclear codes. A relative variance analysis was done to determine the best gamma ray strength function. Then, the effect of level density models for the photoneutron reactions was investigated by using the best gamma ray strength function. The results were compared with each other and also with the experimental data taken from the literature.

Evaluation of Reliable Cross Sections of Photoneutron Reactions on 103Rh and 165Ho Nuclei

With the aim of studying the reasons for the discrepancies between the cross sections determined for total and partial photoneutron reactions from various experiments in beams of quasimonoenergetic annihilation photons, data on such cross sections are analyzed for 103Rh and 165Ho target nuclei. Objective physical criteria of data reliability are used in this analysis. It is shown that significant systematic uncertainties the methods of photoneutron multiplicity sorting that were used in those experiments result in the unreliability of experimental data on the cross sections of (γ, 1n), (γ, 2n), and (γ, 3n) partial reactions over wide regions of photon energies. New cross sections of photoneutron reactions on 103Rh and 165Ho nuclei and data reliability criteria are obtained by employing the experimental—theoretical method developed earlier for evaluating partial reaction cross sections. The evaluated photoneutron reaction cross sections are compared with experimental data.

New Data on the Photodisintegration of 140, 142Ce and 153Eu Nuclei

Experimental data for 140, 142Се and 153Eu nuclei are analyzed jointly using the cross sections for total and partial photoneutron reactions obtained with quasimonoenergy photon beams formed during the annihilation of relativistic positrons. The results from an experiment performed on a bremsstrahlung beam are also used for such an analysis for the 153Eu nucleus. Well-known systemic discrepancies between the results of different experiments are analyzed using the objective physical criteria of data reliability, and ways of allowing for them are considered. New data on the cross sections of (γ, 1n) and (γ, 2n) reactions for 140, 142Се nuclei, on the cross section of (γ, 3n) reaction for 153Eu nucleus, and on the cross section of total photoneutron reaction for all three nuclei were obtained additionally the cross sections of partial reactions that satisfy the established criteria of reliability. It was shown that substantial deviations of the experimental reaction cross sections from those evaluated are due to an unreliable sorting of neutrons between the channels with a multiplicity of 1, 2 due to the abovementioned systematic uncertainties.

Photoneutron reaction cross-section data for As75 : Experiments and evaluation

The problems of reliability of partial photoneutron cross-section data for $^{75}\mathrm{As}$ obtained using beams of quasimonoenergetic photons produced by annihilation in flight of relativistic positrons and the method of neutron multiplicity sorting at Lawrence Livermore National Laboratory (USA) and Centre d'Etudes Nucleaires of Saclay (France) were discussed using the objective physical data reliability criteria. New data for photoneutron reaction cross sections for $^{75}\mathrm{As}$, satisfying those criteria, were obtained using the experimental-theoretical method for partial reaction cross-section evaluating. Evaluated data for $^{75}\mathrm{As}$ were compared with experimental data and the problems of significant disagreements between Livermore and Saclay data were discussed in detail. It was shown that experimental data for the $(\ensuremath{\gamma},1n)$ and $(\ensuremath{\gamma},2n)$ reactions' cross sections obtained at Livermore are not reliable because of significant systematic uncertainties of different nature.

Photoneutron reaction cross section measurements on Mo94 and Zr90 relevant to the p -process nucleosynthesis

The photodisintegration cross sections for the 94Mo({\gamma},n) and 90Zr({\gamma},n) reactions have been experimentally investigated with quasi-monochromatic photon beams at the High Intensity {\gamma}-ray Source (HI{\gamma}S) facility of the Triangle Universities Nuclear Laboratory (TUNL). The energy dependence of the photoneutron reaction cross sections was measured with high precision from the respective neutron emission thresholds up to 13.5 MeV. These measurements contribute to a broader investigation of nuclear reactions relevant to the understanding of the p-process nucleosynthesis. The results are compared with the predictions of Hauser-Feshbach statistical model calculations using two different models for the dipole {\gamma}-ray strength function. The resulting 94Mo({\gamma},n) and 90Zr({\gamma},n) photoneutron stellar reaction rates as a function of temperature in the typical range of interest for the p-process nucleosynthesis show how sensitive the photoneutron stellar reaction rate can be to the experimental data in the vicinity of the neutron threshold.

New Data on Photoneutron Reaction Cross Sections for 76,78,80,82Se Nuclei

The problem of reliability of the cross section data obtained for partial photoneutron reactions on 76,78,80,82Se nuclei in beams of quasimonoenergetic annihilation photons by means of neutron multiplicity sorting is discussed by employing objective physical criteria. It is shown that, because of substantial systematic uncertainties, experimental data on the (γ, 1n) and (γ, 2n) cross sections are unreliable. New data satisfying the reliability criteria are obtained for the partial photoneutron reaction cross sections for 76,78,82Se nuclei by an experimental—theoretical method for evaluating such cross sections and are compared with experimental data and with data evaluated earlier for the isotope 80Se. The evaluated integrated cross sections for the total photoneutron reactions on 76,78,80,82Se nuclei are compared with the predictions of the Thomas-Reiche-Kuhn classical dipole sum rule.

Evaluation of Reliable Cross Sections of Partial and Total Photoneutron Reactions for the 139La Nucleus

Cross sections of partial photoneutron reactions free of the shortcomings of different ways of determining the multiplicity of neutrons used on beams of quasi-monoenergetic annihilation photons are evaluated for 139La. The experimental-theoretical method of evaluation of partial reaction cross sections satisfying proposed data reliability criteria is used to obtain new data on the cross sections of reactions (γ, 1n), (γ, 2n), and (γ, 3n). It is shown that noticeable deviations of experimental cross sections from evaluated values are due to the unreliable sorting of neutrons between channels with multiplicities of 1, 2, and 3.