Excitation Functions Of Reactions Research Articles

Fast neutron spectrum unfolding of a TRIGA Mark II reactor and measurement of spectrum-averaged cross sections: integral tests of differential cross sections of neutron threshold reactions

Summary The spectrum of fast neutrons having energies from 0.5 to 20 MeV in the core of the 3MW TRIGA Mark II reactor at Savar, Dhaka, Bangladesh, was unfolded by activating several metal foils to induce threshold nuclear reactions covering the whole spectrum, and then doing necessary iterative calculations utilizing the activation results and the code SULSA. The analysed shape of the spectrum in the TRIGA core was found to be similar to that of the pure 235U-fission spectrum, except for the energies between 0.5 and 1.5 MeV, where it was slightly higher than the fission spectrum. Spectrum-averaged cross sections were determined by integral measurements. The integral values measured in this work were compared with the recommended values for a pure fission spectrum as well as with the integrated data deduced from measured and evaluated excitation functions of a few reactions given in some data files. The good agreement between integral measurements and integrated data in case of well-investigated reactions shows that the fast neutron field at the TRIGA Mark II reactor can be used for validation of evaluated data of neutron threshold reactions.

Experimental investigation of the 19F(n, α)16N reaction excitation function in the neutron energy range of 4 to 7.35 MeV

The interaction of neutrons with light nuclei study is of interest for understanding nuclear-reaction mechanisms. Fluorine nuclei are worth particular attention because they are abundant in the core of the promising molten-salt reactors and can noticeably affect the chain reaction kinetics. In this work we have experimentally investigated the 19F(n, α)16N reaction cross-section at neutron energies ranging from 4 to 7.35 MeV.

Excitation functions for the formation of longer lived isotopes by deuteron irradiation of Europium

Excitation functions for nuclear reactions induced on natural europium targets by energetic deuterons were studied up to 50MeV. A standard stacked foil technique was used for irradiation and high resolution gamma spectrometry was applied for activity assessment. Direct or cumulative cross sections for reaction products with half-life longer than 2h were determined. Reactions leading to the formation of the radionuclides 147,149,151,153Gd, 147,148,149,150m,150g,152m,152g,154gEu, 153Sm and 150Pm were studied. In most cases no earlier data were available in the literature. The new experimental results were compared with values tabulated in the on-line TENDL2011 library.

Study of fusion and nucleon transfer channels in the 197Au + 6He reaction in an energy range of 6He to 20 Mev/A

New data on the cross sections of reactions occurring during the interaction of 6He nuclei with 197Au at energies of 6He from 40 to 120 MeV are presented. The experiments were performed in the ACCULINNA secondary beam separator of the Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research. To identify the reaction products, the activation method for measuring the gamma activity of the target assembly of thin foils was used. The excitation functions for fusion reactions involving the evaporation of up to ten neutrons from the compound nucleus as well as reactions with the emission of charged particles and nucleon transfer in the investigated energy region are obtained. Data analysis was carried out using two codes: ALICE-MP and NRV. The cross sections for the (6He, xn) reactions occurring through the compound nucleus are mostly in agreement with the results of model calculations based on the statistical approach. It is shown that, up to the energies of 114 MeV, the cross-section drop in the complete fusion reactions is negligible. The experimental excitation functions of reactions leading to the formation of isotopes of mercury and gold (transfer reaction) indicate that the main contribution to their formation is made by direct processes and that evaporation reactions (6He, pxn) and (6He, αxn) play a minor role, as is evidenced by a comparison of the measured cross sections with the calculation results.

Investigating the nuclear fusion and nucleon transfer channels in the 197Au + 6He reaction at 6He energies up to 20 MeV/A

New data on the cross sections of reactions that proceed during the interaction of 6He and 197Au nuclei in the 6He energy range of 40 to 120 MeV are reported. The experiments were performed using the secondary beam of the ACCULINNA separator at the Flerov Laboratory of Nuclear Reactions (FLNR), JINR. Reaction products are identified by means of activation method to measure the gamma activity of a thin-foil target assembly. Excitation functions for 6He fusion reactions with subsequent emission of up to 10 neutrons from the compound nucleus are measured. Cross sections for reactions with emission of charged particles and nucleon transfer were also measured. The experimental cross sections for the (6He, xn) reactions that proceed via the formation of a compound nucleus agree in general with calculations using models that involve the statistical approach. It is shown that the complete fusion reaction cross section drops slightly up to an energy of 114 MeV. The experimental excitation functions for the reactions resulting in the formation of mercury and gold isotopes indicate that the main contribution to their formation comes from direct processes, while the evaporation reactions (6He, pxn) and (6He, αxn) are of minor importance.

Investigation of the 19F(n, α)16N reaction excitation function in neutron energy range of 4–7.35 MeV

New method based on ionization chamber with Frisch grid and digital signal processing was developed for experimental investigation of 19F(n, α)16N reaction. The chamber filling gas with CF4 additive was used as the fluorine-containing target. The experimental investigation of 19F(n, α)16N reaction cross-section in 4–7.35 MeV energy range is represented in this work. The total cross section of 19F(n, α)16N reaction was measured as well as partial cross-section for sum of α0-α3 and sum of α4 and α5 reaction channels.

Cross section measurements of a few threshold reactions induced by fast neutrons from an Am/Be source: integral tests of differential neutron reaction cross section data

Abstract Integral cross sections of the reactions 24Mg(n,p)24Na, 27Al(n,p)27Mg, 27Al(n,α)24Na and 95Mo(n,p)95Nb were measured for the first time with fast neutrons (E n > 1.5 MeV) from an Am/Be source. Furthermore, upper cross section limits for the reactions 98Mo(n,α)95Zr and 103Rh(n,p)103Ru were deduced. The results were compared with data calculated using the neutron spectral distribution and the excitation function of each reaction given in the data files and libraries ENDF/B-VII, JEFF-3.1.2, JENDL-4.0, IRDF-2004, TENDL-2010, ROSFOND-2010 and CENDL-3.1. In general, the integral measurement and the integrated value agreed within ± 10%. The fast neutron field (with E n > 1.5 MeV) of the Am/Be source is thus well suited for integral tests of excitation functions of neutron threshold reactions.

Investigation of activation cross-section data of proton induced nuclear reactions on rhenium

In the frame of systematic investigations of activation cross-section data for different applications the excitation functions of natRe(p,x)185Os, 183mOs, 183gOs, 182Os, 181mOs, 186gRe, 184mRe, 184gRe, 183Re, 182mRe, 182gRe and 181gRe reactions were measured up to 70MeV. The data for the natRe(p,x) 183mOs, 183gOs, 182Os, 181gOs,186gRe, 184mRe,182mRe, 182gRe, and 181Re reactions are reported for the first time. The activation method, the stacked foil irradiation technique and γ-spectroscopy for activity detection were used. The experimental data were compared with predictions of three theoretical codes. From the measured cross-section thick target integral yields were also calculated and presented.

STEREODYNAMICS STUDY OF THE ABSTRACTION REACTION H + CD4 → HD + CD3

A new London–Eyring–Polanyi–Sato (LEPS) potential energy surface (PES) is employed in this work to study the stereo properties for the abstraction reaction of hydrogen with methane at its rovibrationally ground state using the quasiclassical trajectory method (QCT). A "quasi-triatomic" approximation is used to treat the CD3 group of CD4 as a pseudoatom. The calculated excitation function of the title reaction can give a good agreement to most experimental and theoretical data at collision energies (Ec =1.5 ~ 2.5 eV ). Further investigation of the product HD in reaction H + CD4 (v = 0, j = 0) → HD + CD3 and D + CH4 (v = 0, j = 0) → HD + CH3 shows the dependence of the product rotational polarization on collision energies and mass factor, but P(θr) is not sensitive to both the collision energies and the mass factor.

Excitation functions of (n,2n) reactions for stable lead isotopes from reaction threshold to 20 MeV

The excitation functions for (n,2n) reactions from reaction threshold to 20MeV on four stable lead isotopes 204Pb, 206Pb, 207Pb and 208Pb were calculated using Talys-1.2 nuclear model code, this essentially involves fitting a set of global parameters. An excellent agreement between the calculated and experimental data is obtained. The level densities and effective imaginary potential were studied to obtain the best fit of the excitation functions. The cross sections were calculated by invoking suitable options for global optical model potential, microscopic level densities from Goriely’s Table, Hauser–Feshbach model for equilibrium calculations, the two-component exciton model by Kalbach for pre-equilibrium calculations in the Talys input file. The results of the present study reveal that the theoretical estimation of the cross sections match fairly well with the experimental data (EXFOR database) as well as with the evaluated data files (ENDF/VII.0, JENDL-4.0, CENDL-3.1). This is of importance to the validation of nuclear model approaches with increased predictive power.

New measurements and evaluation of database for deuteron induced reaction on Ni up to 50 MeV

Excitation functions for nuclear reactions induced by deuterons up to 50MeV on natural nickel targets were studied in five experiments using a standard stacked foil technique and non destructive high resolution gamma spectrometry. Reaction products with half life of more than 2h were assessed. The elemental activation cross sections were determined for reactions resulting in the radionuclides 61Cu, 56,57Ni, 55,56,57,58,60Co, 52,54,56Mn and 51Cr. The new experimental results were compared with earlier evaluated data and with values tabulated in the online TENDL2011 library.

Excitation functions of (d,x) nuclear reactions on natural titanium up to 24 MeV

Excitation functions of the natTi(d,x)48V and natTi(d,x)43,44m,44g,46,47,48Sc nuclear reactions were measured up to a 24-MeV deuteron energy by using a stacked-foil activation technique combined with γ-ray spectrometry with a high-purity germanium detector at the AVF cyclotron of the RIKEN RI Beam Factory, Wako, Japan. An overall good agreement is found between the measured cross-sections and the literature ones, whereas partial agreements are obtained for the theoretical calculations based on the TALYS code. Physical thick target yields, i.e., induced radioactivities per unit fluence of the 24-MeV deuteron were also deduced, and they were compared with the directly measured ones in the literature. The present results will have an important role in enrichment of the literature database of the deuteron-induced reactions on natural titanium leading to various applications.

Pre-equilibrium and equilibrium calculations of (n, p) reactions on 32S, 64Zn, 67Zn, 89Y, 90Zr and 153Eu targets used for production of 32P, 64Cu, 67Cu, 89Sr, 90Y and 153Sm therapeutic radionuclides

In this study, by using the pre-equilibrium and equilibrium reaction mechanisms, the cross-sections of (n, p) reactions on 32S, 64Zn, 67Zn, 89Y, 90Zr and 153Eu targets have been calculated. The excitation functions of (n, p) reactions on 32S, 64Zn, 67Zn, 89Y, 90Zr and 153Eu targets by using the hybrid model, the geometry dependent hybrid model and the exciton model of pre-equilibrium reaction mechanism at the energies in the range 1–20MeV have been investigated. To investigate the equilibrium effects, the Weisskopf–Ewing model is used. The proton emission spectra of (n, xp) reactions by 14.6, 14.8 and 14.8MeV neutron incident energies, respectively, on 32S, 89Y and 90Zr targets are also investigated using the same models. The obtained results have been discussed and compared with the experimental results.

Outstanding features of reactions with halo nuclei

Recent results for total reaction and fusion excitation functions for halo systems are compiled. The striking similarity in the behavior of total cross sections for proton-halo (8B) and neutron-halo (6He) systems is pointed out. Static and dynamic halo effects are elucidated by comparing data for a neutron-halo nucleus and its core. Fusion cross sections are discussed in terms of a maximum angular momentum for fusion, Lf. A linear energy dependence for Lf is consistent with the data for all the existing measurements so this might actually be a characteristic feature of true halo systems. A qualitative difference between the fusion of neutro-halo and proton-halo systems also is pointed out.

Excitation functions for deuterium-induced reactions on 194Pt near the coulomb barrier

Experiments were carried out at the U-120M cyclotron of the Nuclear Physics Institute of the Czech Republic in Řež using extracted beams of deuterons with energies of 11.7 and 16.4 MeV. The irradiated targets were made of natural Pt and enriched 194Pt. For the two natPt + d and 194Pt + d reactions, cross sections for the production of the isotopes 194Au, 195Au, and 195 mPt near the Coulomb barrier were measured. Calculations of these cross sections at different energies of the deuteron beam were performed with the programs EMPIRE 2.18 and TALYS 1.2. The values calculated for cross sections with a standard set of parameters cannot reliably describe the measured excitation functions for the reactions in the studied range of deuteron energy.

Alpha Induced Reaction Cross Section Calculations of Tantalum Nucleus

The fusion energy is attractive as an energy source because the fusion will not produce CO2 or SO2 and so fusion will not contribute to environmental problems, such as particulate pollution and excessive CO2 in the atmosphere. The fusion reaction does not produce radioactive nuclides and it is not self-sustaining, as is a fission reaction when a critical mass of fissionable material is assembled. Since the fusion reaction is easily and quickly quenched the primary sources of heat to drive such an accident are heat from radioactive decay and heat from chemical reactions. Both the magnitude and time dependence of the generation of heat from radioactive decay can be controlled by proper selection and design of materials. Tantalum is one of the candidate materials for the first wall of fusion reactors and for component parts of irradiation chambers. Accurate experimental cross-section data of alpha induced reactions on Tantalum are also of great importance for thermonuclear reaction rate determinations since the models used in the study of stellar nucleosynthesis are strongly dependent on these rates (Santos et al. in J Phys G 26:301, 2000). In this study, neutron-production cross sections for target nuclei 181Ta have been investigated up to 100 MeV alpha energy. The excitation functions for (α, xn) reactions (x = 1, 2, 3) have been calculated by pre-equilibrium reaction mechanism. And also neutron emission spectra for 181Ta (α, xn) reactions at 26.8 and 45.2 MeV have been calculated. The mean free path multiplier parameters has been investigated. The pre-equilibrium results have been calculated by using the hybrid model, the geometry dependent hybrid (GDH) model. Calculation results have been also compared with the available measurements in literature.

Cross Sections Calculations of (d, t) Nuclear Reactions up to 50 MeV

In nuclear fusion reactions two light atomic nuclei fuse together to form a heavier nucleus. Fusion power is the power generated by nuclear fusion processes. In contrast with fission power, the fusion reaction processes does not produce radioactive nuclides. The fusion will not produce CO2 or SO2. So the fusion energy will not contribute to environmental problems such as particulate pollution and excessive CO2 in the atmosphere. Fusion powered electricity generation was initially believed to be readily achievable, as fission power had been. However, the extreme requirements for continuous reactions and plasma containment led to projections being extended by several decades. In 2010, more than 60 years after the first attempts, commercial power production is still believed to be unlikely before 2050. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. In the fusion reactor, tritium self-sufficiency must be maintained for a commercial power plant. Therefore, for self-sustaining (D–T) fusion driver tritium breeding ratio should be greater than 1.05. Working out the systematics of (d, t) nuclear reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. Since the experimental data of charged particle induced reactions are scarce, self-consistent calculation and analyses using nuclear theoretical models are very important. In this study, (d, t) cross sections for target nuclei 19F, 50Cr, 54Fe, 58Ni, 75As, 89Y, 90Zr, 107Ag, 127I, 197Au and 238U have been investigated up to 50 MeV deuteron energy. The excitation functions for (d, t) reactions have been calculated by pre-equilibrium reaction mechanism. Calculation results have been also compared with the available measurements in literature.

Measurement of the natHf(d,x)177Ta cross section and impact of erroneous gamma-ray intensities

In this work, excitation functions for deuteron-induced reactions on natural hafnium have been measured in the energy range 7–17MeV, using the stacked-foil technique. Particular attention has been paid to the reaction natHf(d,x)177Ta, because reported γ-ray intensities have been found to be in disagreement with previously published data. This discrepancy is due to an error in the 2003 ENSDF absolute γ-ray intensities of 177Hf following the decay of 177Ta, which are about a factor of three higher compared to other available data. As a consquence, some peer reviewed papers reporting on natHf(d,x)177Ta, and also on natHf(p,x) 177Ta and natW(p,x) 177Ta, need to be reviewed. An upcoming re-evaluation of the 177Ta decay data shows new significant changes in the absolute γ-ray intensities, which in turn will affect again the 177Ta producing cross sections.

Investigation of deuteron breakup and deuteron-induced fission on actinide nuclei at low incident energies

An analysis of the $^{231}$Pa$(d,3n)$$^{230}$U reaction excitation function at energies around the Coulomb barrier has taken into account the pre-equilibrium and compound-nucleus cross sections corrected for the deuteron-breakup decrease of the total reaction cross section, as well as the inelastic breakup enhancement. The analysis reveals the dominance of the deuteron breakup mechanism unlike a former assessment in this respect of the deuteron-induced fission process.

Excitation functions and isotopic effects in (n,p) reactions for stable iron isotopes from reaction threshold to 20 MeV

The excitation functions for (n,p) reactions from reaction threshold to 20MeV on four stable Iron isotopes viz; 54Fe, 56Fe, 57Fe and 58Fe were calculated using Talys-1.2 nuclear model code. This essentially involves fitting a set of global parameters. An excellent agreement between the calculated and experimental data is obtained with minimal effort on parameter fitting and only one free parameter called ‘shell damping factor’ has been adjusted. This is very important for the validation of nuclear model approaches. The systematic decrease in (n,p) cross-sections with increasing neutron number in reactions induced by neutrons on isotopes of iron is explained in terms of the pre-equilibrium model. The compound nucleus and pre-equilibrium reaction mechanism as well as the isotopic effects were also studied extensively.