Partial Reaction Cross Sections Research Articles

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

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 in Experiments on Beams of Bremsstrahlung

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

К программе фотоядерных исследований на пучке обратных комптоновских квазимонохроматических 𝛾–квантов с перестраиваемой энергией E𝛾 ≲ 40 МэВ

Based on the analysis of development of photonuclear reaction studding at 𝐸𝛾 ≲ 40 MeV and the unique parameters of the Compton source of 𝛾–quanta under projecting, a program of priority photonuclear research using this source is proposed. The program includes research on: structures of giant E1 resonances and pygmy resonances; cross sections for partial photonucleon reactions; nuclear resonant fluorescence; photofission; problems of astrophysics and nucleosynthesis.

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

Measurement of partial (n, n’γ) reaction cross-sections on highly radioactive nuclei of interest for energy production

In the context of the development of Gen. IV nuclear reactors, the GIF (Generation IV. International Forum) has selected six innovative technologies. Among them, one can highlight the concept of breeding for 232Th/233U and 238U/239Pu fuel cycles. But those nuclei, crucial for such cycles, suffer from a lack of precise knowledge (nuclear structure, reaction cross sections). In particular, it has been demonstrated that neutron inelastic scattering reaction cross sections are not known with sufficient precision for the isotopes 238U and 239Pu, and not known at all experimentally for 233U. In order to perform simulations of innovative reactor cores for the development of those technologies, the knowledge of the reaction cross section has to be improved which implies that new measurements have to be done. The GRAPhEME (GeRmanium array for Actinides PrEcise MEasurements) experimental setup, developed by the IPHC laboratory from CNRS and installed at the EC-JRC-Geel GELINA facility is a powerful tool to answer this need [1, 2]. Combining the prompt γ-ray spectroscopy and the time-of-flight methods, it measures partial (n, xnγ) reaction cross sections. This paper reports on the improvements made on the GRAPhEME setup and data analysis methodology to tackle the challenge of (n, xnγ) cross section measurements on high activity actinides. Results obtained so far on 233U are presented compared to TALYS calculations.

Fragmentation of carbon on elemental targets at 290AMeV

The total charge-changing cross-sections and the partial cross-sections for projectile fragments (PFs) production for the fragmentation of 12C on C, Al, Cu, Pb and CH2 targets at the highest energy of 290[Formula: see text]A[Formula: see text]MeV were studied. It was found that the total charge-changing reaction cross-sections and the partial reaction cross-sections of PFs production were independent of the beam energy, and increased with increase of mass of target for the same beam energy. The total charge-changing reaction cross-section was the same as the prediction of Bradt–Peters semi-empirical formula, PHITS and NUCFRG2 simulation models. The partial cross-section of PFs production increased with the increase of the mass of target, and it was the same as the prediction of NUCFRG2 models. The mean scattering angle of projectile particle was smaller than the average emission angle of PF, and the width of scattering angle distribution of projectile particle was smaller than that of emission angle distribution of PFs. The mean emission angle of PFs does not obviously depend on the target mass and beam energy in our studied beam energy regions.

Reliability of Neutron Yield Cross Sections on 12C–127I Isotopes in Proton-Induced Reactions Evaluated Using GEANT4 Package for Proton Therapy Applications

The work is aimed at studying the reliability of proton-induced neutron yield cross sections on 12C–127I biological tissue isotopes using the GEANT4 Monte Carlo simulation package, which is commonly applied for dosimetry calculations in proton therapy. Because of the lack of experimental results on the neutron yield for most of the isotopes considered, the simulated cross sections are first compared with theoretical data acquired using the TALYS nuclear reaction package, and the partial reaction cross sections calculated in TALYS are in turn analyzed in comparison with available experimental results. The mismatch between theory and experiment allows one to suggest a significant uncertainty in the calculation of the neutron doses associated with the isotopes under consideration.

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.

Nuclear spallation in active galaxies

A number of works point to the presence of narrow emission features at unusual energies in the X-ray spectra of active galactic nuclei (AGN) or to potentially low iron abundances as possible evidence for the spallation of iron. With the imminence of high-resolution calorimeter spectroscopy, the potential to test spallation models in astrophysical sources will soon be possible. Previously determined nuclear spallation reactions of Fe are recalculated making use of improved total inelastic and partial reaction cross sections that result in different absolute and relative abundances of the main spallation elements Mn, Cr, V, and Ti. The effects of ionisation and dynamics near the black hole are examined in simulated spectra with CCD and calorimeter (i.e. Hitomi) resolution. With high-resolution, differences in relative abundances and ionisation should be detectable if spallation is originating at large distances from the black hole (e.g. torus or disc wind) where blurring is not significant. If spallation were occurring in the inner accretion disc, it would likely be undetected as blurring effects would cause significant blending of spectral features.

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.

The Reliability of Cross Sections of Partial Photoneutron Reactions for 98Mo

The cross sections of partial photoneutron reactions for 98Mo were evaluated. These cross sections are free from the shortcomings of various methods for neutron multiplicity determination used at the beams of quasimonoenergetic annihilation photons and bremsstrahlung radiation. New data on the cross sections of reactions (γ, 1n), (γ, 2n), and (γ, 3n) were obtained using the experimental–theoretical method for evaluation of cross sections of partial reactions satisfying the introduced physical reliability criteria. It is demonstrated that considerable deviations of the experimental cross sections from the evaluated ones result from an inaccurate sorting of neutrons between channels with a multiplicity of 1, 2, and 3.

Evaluated Cross Sections of Photoneutron Reactions on the Isotope 116Sn and Spectra of Neutrons Originating from These Reactions

With the aid of the results obtained by evaluating cross sections of partial photoneutron reactions on the isotope 116Sn and the energy spectra of neutrons originating from these reactions, the possible reasons for the well-known discrepancies between the results of different photonuclear experiments were studied on the basis of a combinedmodel of photonuclear reactions. On the basis of physical criteria of data reliability and an experimental–theoretical method for evaluating cross sections of partial reactions, it was found that these discrepancies were due to unreliably redistributing neutrons between (γ, 1n), (γ, 2n), and (γ, 3n) reactions because of nontrivial correlations between the experimentally measured energy of neutrons and their multiplicity.

Modern status of photonuclear data

The reliability of experimental cross sections obtained for (γ, 1n), (γ, 2n), and (γ, 3n) partial photoneutron reactions using beams of quasimonoenergetic annihilation photons and bremsstrahlung is analyzed by employing data for a large number of medium-heavy and heavy nuclei, including those of 63,65Cu, 80Se, 90,91,94Zr, 115In, 112−124Sn, 133Cs, 138Ba, 159Tb, 181Ta, 186−192Os, 197Au, 208Pb, and 209Bi. The ratios of the cross sections of definite partial reactions to the cross section of the neutron-yield reaction, F i = σ(γ, in)/σ(γ, xn), are used as criteria of experimental-data reliability. By definition, positive values of these ratios should not exceed the upper limits of 1.00, 0.50, 0.33,... for i = 1, 2, 3,..., respectively. For many nuclei, unreliable values of the above ratios were found to correlate clearly in various photon-energy regions F i with physically forbidden negative values of cross sections of partial reactions. On this basis, one can conclude that correspondent experimental data are unreliable. Significant systematic uncertainties of the methods used to determine photoneutron multiplicity are shown to be the main reason for this. New partial-reaction cross sections that satisfy the above data-reliability criteria were evaluated within an experimental–theoretical method [σ eval(γ, in) = F i theor (γ, in) × σ expt(γ, xn)] by employing the ratios F i theor (γ, in) calculated on the basis of a combined photonuclear-reaction model. It was obtained that cross sections evaluated in this way deviate substantially from the results of many experiments performed via neutron-multiplicity sorting, but, at the same time, agree with the results of alternative activation experiments. Prospects of employing methods that would provide, without recourse to photoneutron-multiplicity sorting, reliable data on cross sections of partial photoneutron reactions are discussed.

Photoneutron cross sections for 59Co : Systematic uncertainties of data from various experiments

Data on partial photoneutron reaction cross sections $(\gamma ,1n)$ , $(\gamma ,2n)$ , and $(\gamma ,3n)$ for 59Co obtained in two experiments carried out at Livermore (USA) were analyzed. The sources of radiation in both experiments were the monoenergetic photon beams from the annihilation in flight of relativistic positrons. The total yield was sorted by the neutron multiplicity, taking into account the difference in the neutron energy spectra for different multiplicity. The two quoted studies differ in the method of determining the neutron. Significant systematic disagreements between the results of the two experiments exist. They are considered to be caused by large systematic uncertainties in partial cross sections, since they do not satisfy physical criteria for reliability of the data. To obtain reliable cross sections of partial and total photoneutron reactions a new method combining experimental data and theoretical evaluation was used. It is based on the experimental neutron yield cross section which is rather independent of neutron multiplicity and the transitional neutron multiplicity functions of the combined photonucleon reaction model (CPNRM). The model transitional multiplicity functions were used for the decomposition of the neutron yield cross section into the contributions of partial reactions. The results of the new evaluation noticeably differ from the partial cross sections obtained in the two experimental studies are under discussion.

Physical criteria for the reliability of data on the photodisintegration of the 89Y nucleus

Experimental photonuclear reaction cross sections obtained in experiments using quasimonoenergetic annihilation, monoenergetic tagged photons, and bremsstrahlung γ-radiation are analyzed using physical criteria for the reliability of data on the 89Y nucleus. It is found that the reliability of data on the cross sections of partial reactions (γ, 1n) and (γ, 2n), obtained by means of photoneutron multiplicity sorting, is highly doubtful. Reliable cross sections of reactions (γ, 1n) and (γ, 2n) are obtained using the experimental–theoretical method (ETM) for evaluating using both experimental cross sections of neutron yield reaction σexp(γ, xn) that are free of neutron multiplicity problems, and theoretically calculated F i theor ratios of the cross sections of definite (i) partial reactions to cross section σtheor(γ, xn). It is shown that the evaluated cross sections differ noticeably from the experimental data.

Cross sections of the photoneutron reaction for 141Pr and 186W nuclei, estimated from physical criteria of data reliability

Using objective physical criteria for data reliability, cross sections of partial photoneutron reactions (γ, 1n), (γ, 2n) and (γ, 3n) that are free of the shortcomings of neutron multiplicity sorting methods used on beams of quasimonoenergetic annihilation photons are obtained for 141Pr and 186W nuclei. Evaluation is performed using the experimental–theoretical method (ETM), based on the experimental cross section of neutron yield reaction σexp(γ, xn) = σexp(γ, 1n) + 2 σexp(γ, 2n) + 3 σexp(γ, 3n) + … and ratios F i theor= σtheor(γ, in)/σtheor(γ, xn) calculated within the combined model (CM) of photonuclear reactions, which stipulates that σeval(γ, in) = F i theor σexp(γ, xn). It is found that for 141Pr and 186W, ratios F exp i do not contradict the data reliability criteria only at energies up to ~21 and ~22 MeV, respectively. At the same time, there are notable discrepancies between F i theor and F exp i, and thus between the evaluated and experimental cross sections of reactions. It is shown that the discrepancies between the evaluated and experimental cross sections are due to the assumed unreliable experimental distribution of neutrons in the channels with multiplicities 1, 2, and 3.

Photoneutron reactions in the range of giant dipole resonance

The well-known significant systematic disagreements between data on partial photoneutron reaction cross sections obtained in experiments using quasimonoenergetic annihilation photons and bremsstrahlung were investigated using objective physical criteria of data reliability. It was shown that many data are not reliable because of significant systematic uncertainties of the photoneutron multiplicity sorting methods used. The experimental–theoretical method for evaluation of reliable partial reaction cross sections was proposed and many new data were obtained.