7Be Reaction Research Articles

Differential cross section measurements of the 7Li(3He, p0)9Be, 7Li(3He, p2)9Be, and 7Li(3He, d0)8Be reactions from 2 to 4 MeV

The use of lithium in plasma facing components (PFCs) for fusion reactors is increasingly more prominent due to its ability to enhance plasma performance and potential to protect the underlying high-Z PFCs. In order to use nuclear reaction analysis (NRA) to investigate lithium depth profiles in fusion relevant experiments such as hydrogen retention in lithiated PFCs, there is a need for experimental measurements of the cross section of the reactions of interest over a wide range of energies and in a scattering angle in which the differential cross sections of other relevant species, such as deuterium and oxygen, have been measured. In this paper we report the differential cross sections of the 7Li(3He, p0)9Be, 7Li(3He, p2)9Be, and 7Li(3He, d0)8Be reactions from 2 to 3.919 MeV at a measurement angle of 135°. The measurements were performed on a lithium fluoride film target with the 7Li areal density determined using the 7Li(p, α)4He reaction at 2 MeV and 150°.

Production and measurement of a stellar neutron spectrum at 30 keV

A few years ago, we theoretically studied the production of a stellar neutron spectrum at kT = 30 keV using a shaped proton beam impinging on a thick lithium target. Here, we first measure the proton distribution to better control the produced neutron spectrum. Then, we measure the forward-emitted angle-integrated neutron spectrum of the 7Li(p,n)7Be reaction via time-of-flight neutron spectrometry with such proton distribution. The result resembles a stellar neutron spectrum at kT = 30 keV. This method avoids in activation experiments the need for spectrum correction. In the case of spherical samples, no knowledge of the cross-section of the isotope being measured by activation would be necessary. Therefore, the present method is of interest for isotopes with unknown or poorly known cross-sections, such as branching points in astrophysics. The key point of our method is the experimental control of the proton distribution that impinges on the lithium target.

Measurement of fast neutron induced (n,γ) reaction cross-section of 68Zn, 96Zr, 121Sb and 123Sb in the energy range of 1 to 2 MeV

The (n,γ) reaction cross-section for the elements 68Zn, 96Zr, 121Sb and 123Sb, present in the reactor structural/shielding materials, was measured by neutron activation technique in the neutron energy region of 1–2 MeV as very limited data is available in this energy range. Further, the neutron spectrum peaks in this energy region for the fast breeder reactors and proposed accelerator driven sub-critical systems. The natural strontium (natSr) element was used as a neutron flux monitor by considering effective combined reaction cross-section for 86Sr(n,γ)87Srm and 87Sr(n,n′)87Srm reactions. The pellets of mixture of sample and monitor were irradiated by a quasi-mono energetic fast neutron beam, generated by 7Li(p,n)7Be reaction at FOTIA, Bhabha Atomic Research Centre, Mumbai, India. The activity of activation products was measured by off-line gamma-ray spectrometry using High Purity Germanium Detector (HPGe). The present data with improved uncertainty and covariance analysis enhance the cross-section data base for better constraining the evaluated data and theoretical models. The theoretical (n,γ) reaction cross-sections were calculated using TALYS 1.96, which could reasonably explain the present data with the Fermi gas level density prescription.

Activation cross section for 85Rb(n,2n)84mRb and 85Rb(n,p)85mKr reactions with uncertainty propagation and covariance analysis

The cross section of 85Rb(n,2n)84mRb and 85Rb(n,p)85mKr reactions were measured at neutron energy range 12–20 MeV using activation analysis followed by off-line γ-ray spectroscopic technique. The quasi mono-energetic neutrons were produced through 7Li(p,n)7Be reaction. The measurements were done relative to 27Al(n,α)24Na reference monitor reaction cross section. The detailed uncertainty propagation from the attributes present in measurements was performed using covariance analysis. The γ-ray self-attenuation and background low neutron energy corrections were performed in the measurement studies. Theoretical calculations were performed by TALYS-1.96 nuclear code. The comparison of measured values with the available data in EXFOR database and evaluated data from JENDL-5 and EAF-2010 shows the measured cross section values of 85Rb(n,p)85mKr reaction were slightly higher than the published values, evaluated data and theoretical data while for 85Rb(n,2n)84mRb, the measured values were consistent with the published data.

Differential cross-section measurement for 10B(p, αγ1)7Be, 10B(p, p’γ1)10B and 11B(p, p’γ1) 11B reactions

Differential cross-sections of the 10B(p, αγ1)7Be (Eγ = 429 keV), 10B(p, p’γ1)10B (Eγ = 718 keV) and 11B(p, p’γ1) 11B (Eγ = 2124 keV) reactions have been measured at proton laboratory energies of 912–2776 keV at 90°. The proton beam impinged on a thin natB2O3 film evaporated onto a self-supporting thin carbon layer. The incident energies were increased by 10 (20) keV steps in the resonance (off-resonance) regions. Our data are compared with the existing ones from literature. A benchmark procedure was performed by comparing the calculated thick-target yields from the current differential cross-sections with the existing measured thick target gamma-ray yields. The overall systematic uncertainty of the cross-sections was estimated to be about 10 %, mainly related to the target thickness determination.

Study of one-step and two-step neutron transfer in the reaction 6Li + 9Be* *Supported by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (AP19677087) and by the Russian Science Foundation (24-22-00117)

This paper presents the results of experiments conducted to measure the cross-sections for elastic scattering and nucleon transfer channels in the 6Li+9Be reaction at an incident energy of 68 MeV: 9Be(6Li,6Li)9Be, 9Be(6Li,7Li)8Be, 9Be(6Li,7Li)8Be2+, 9Be(6Li,8Li)7Be, and 9Be(6Li,7Be)8Li. The objective of the study is to elucidate the manifestation of the cluster structure of 9Be. Theoretical analysis of the contributions of the one-step and two-step neutron transfer mechanisms is performed using the distorted wave Born approximation method with the Fresco code. Good agreement between the calculations and the experimental data is obtained for the channels of elastic scattering 9Be(6Li,6Li)9Be, neutron 9Be(6Li,7Li)8Be, and proton transfer 9Be(6Li,7Be)8Li, as well as for the transfer of two neutrons 9Be(6Li,8Li)7Be. The dineutron cluster transfer mechanism makes a dominant contribution to the 9Be(6Li,8Li)7Be reaction channel at forward angles.

Bricks non-destructive simulation testing method utilizing neutron radiography facility based on a 7Li(p,n)7Be reaction

The evaluation of non-destructive neutron radiography (NR) for examining the internal composition of various structural materials, has been the focus of extensive research. This manuscript uses non-destructive testing to generate three-dimensional radiographs of three different brick structural materials: glass block, magnesia-chrome, and lead to evaluate their capability to withstand fast neutrons and gammas emitted from a source. When neutrons with thermal or epithermal spectrum are required, the optimum combination for an accelerator was simulated using a 2.8 MeV proton beam on a lithium target. The presented facility tested both thermal and fast neutron radiography. This study examined various aperture diameters and collimator lengths. It found that implementing a special fast neutron filter significantly increased the thermal neutron content (TNC) with minimal impact on the thermal neutron flux. For fast neutron radiography, the study evaluated parameters such as geometric unsharpness, fast neutron flux, and the percentage of the uncollided fast neutron reaching the object. Both neutrons and photons from the source were used to inspect faults in a glass brick.

Measurement of the 9Be(d, xt) Reaction Total Cross Sections by Secondary Activation and Spectroscopy Methods

Measurement of the 9Be(d, xt) Reaction Total Cross Sections by Secondary Activation and Spectroscopy Methods

Slow 7Be and the primordial 7Li abundance

The cross sections of neutron-induced nuclear reactions are commonly large at low energies. Given this feature, the 7Be(n, p)7Li process with slow 7Be is studied in connection with the cosmological lithium problem. An idea is tested whether slow (non-Maxwellian) 7Be born in the radiative capture 3He(α, γ)7Be reaction can boost the 7Be(n, p)7Li(p, α)α mechanism of 7Li burn-up in the early universe, reducing the amount of primordial 7Li. The rate of this sequential process is examined and its effect on the 7Li abundance is clarified. In the absence of 7Be thermalization in the primordial plasma, the above mechanism can decrease 7Li/H by several percent, leaving unchanged the abundances of D and 4He which are consistent with observations. However, taking into account the 7Be thermalization due to scattering off electrons, positrons, nuclei, and photons radically suppresses the effect. It is found that the typical thermalization time of 7Be is less than 10−5 s, while the fraction of non-Maxwellian particles in the 7Be component is at most 2 × 10−7. Under this condition, the corresponding impact on 7Li/H is estimated to be no more than 10−5%.

Evaluation of cross sections for fast ion reactions with beryllium in helium and hydrogen fusion plasmas

To computationally support hydrogen and helium plasma discharges in the early stages of tokamak operation and to support the commissioning of the neutron detectors during these operational phases, creation of a realistic neutron and gamma ray particle source for Monte Carlo simulations will be needed. One of the most important parts of creating the particle source is calculating the reaction rates of the particle-emitting reactions to determine the emission profile in the plasma and the energy spectra of the emitted particles. In this paper the analysis and evaluation of cross sections for important neutron-emitting reactions, namely, 9Be(p,nγ)9B, 9Be(3He,nγ)11C, and charged-particle emission reactions 9Be(p,d)2α and 9Be(p,α)6Li that cause neutron emission in the next step of interactions are presented. The reaction cross sections were evaluated based on experimental measurements and empirical models describing the interaction of two charged particles. Evaluation of the associated uncertainties was also performed. The main goal of the work is to propose the newly evaluated cross sections for inclusion in the FENDL nuclear data library, thus making the cross section available to other researchers studying the above listed reactions.

Angular differential cross section measurement for 11B(p, α0)8Be reaction with proton energy of 2.5 MeV

This report presents experimental differential cross section measurements at α0-particles’ eight outgoing angles of 50°, 70°, 90°, 106°, 120°, 130°, 150°, and 160° from 11B(p, α0)8Be reaction induced by 2.5 MeV proton beam bombarding on a natural boron target. The proton beams were accelerated by the 5SDH-2 pelletron at the University of Science - Hanoi National University (HUS). A good agreement has been observed between the obtained results and those from the literature. The importance of the data in a widely angular range is evidenced for the precise determination of the total integrated cross section.

A Micromegas-based gaseous detector for neutron-induced charged-particle reaction studies in nuclear astrophysics

The quasistellar neutron spectrum produced via 7Li (p, n)7Be reaction at a proton energy of 1.912 MeV has been extensively studied and employed reaction for neutron-induced reaction studies. We are working towards using this reaction at various proton energies from 1.9 MeV to 3.6 MeV to produce a neutron field at a temperature range of ∼ 1.5–3.5 GK to conduct measurements of neutron-induced charge particle reaction cross sections on various unstable nuclei at explosive stellar temperatures. In this paper, we are reporting our design and simulation study with regards to experimental set-up and a gaseous detector with a segmented Micromegas detector for conducting neutron-induced charge particle reactions studies for nuclei of astrophysics importance, for example, 26Al(p, n)26Mg, 26Al(n, α)23Na and 40K(p, n)40Ar, 40K(n, α)37Cl reactions. We plan to perform our experiments with a 10-μA proton beam at the Physikalisch Technische Bundesanstalt facility (PTB, Germany), with a Micromegas-based gaseous detector under construction as discussed in the paper.

Maxwell–Boltzmann-like neutron spectrum production for Maxwellian averaged cross sections measurements

Over the years, Maxwellian Averaged Cross Sections (MACS) have been measured by neutron activation, providing a neutron energy spectrum resembling the one found inside the stars. Recently, a new method has been proposed to produce stellar spectra at different stellar temperatures (a Maxwell–Boltzmann neutron energy distribution), employing the 7Li(p,n)7Be reaction. The method is based on the idea of shaping the proton beam energy to shape the neutron beam spectrum. This method was applied to obtain a well-reproduced Maxwell–Boltzmann neutron spectrum (MBNS) at kT=28 keV. An initial proton energy of 3170 keV and an aluminum foil as a proton energy shaper were employed. Differential angular neutron energy distributions from 0 to 90 degrees in 10∘ steps were measured to obtain the 0∘–90∘ integrated neutron spectrum over a neutron flight path of 50 cm. This manuscript reports on the measurement results, confirming the method’s capability, and suggests the approach for producing a high-quality MBNS at kT=28 keV.

Mechanical and Architectural Changes in Animal Bone Following Fast Neutron Irradiation.

Damage to healthy bone following exposure to ionizing radiation has been well documented for at least seven decades. Among the reported effects are a transient increase in stiffness and a reduction in breaking strength. These changes have been linked to a decrease in osteoblast proliferation and differentiation, inducing cell cycle arrest, reducing collagen production, and increasing sensitivity to apoptotic agents. In this work, we analyzed some mechanical and structural changes in compact costal bovine bone (Hereford breed, n = 9) subjected to escalating doses of fast neutrons from a 7 Li(p,n) 7 Be reaction. The mean neutron energy was 233 keV with calculated absorbed doses ranging from 0 to 4.05 ± 10% Gy. Samples were subjected to Young's Modulus (YM) and breaking strength testing with a Universal Testing Machine (UTM). We found an increase in Young's Modulus and a decrease in breaking strength as functions of increasing dose equivalent. Optical coherence tomography (OCT) revealed trabecular displacement into compact bone in an irradiated sample (D = 4.05 ± 10% Gy), with breaching of the endosteal wall. OCT further revealed a "crack-like" structure across the irradiated sample, potentially consistent with damage from a proton track resulting from an elastic (n,p) reaction. No previous report has been found on mechanical changes in large mammalian bones following fast neutron doses, nor of the OCT imaging of such samples.

A Neutron Beam Shaping Assembly for Boron Neutron Capture Therapy of Superficial Tumors

The Vacuum Insulated Tandem accelerator have been developed in Budker Institute of Nuclear Physics. Neutrons are generated in 7Li(p,n)7Be reaction. Neutron beam shaping assembly is used for therapeutic beam forming. It consists of the moderator, reflector and filter. Magnesium fluoride is considered optimal material for neutron slowing down because of noticeable cross section of inelastic neutron scattering. Previously, we showed that it is optimal to use proton beam at energy 2.3 MeV for neutron generation.As a result of a critical analysis of our earlier decisions on the methods used to form a therapeutic neutron beam and decisions of other research groups, as well as successful experiments on the irradiation of laboratory pets and cell cultures carried out at our experimental facility, we noticed that with the recent trend towards a decrease in proton energy the process of inelastic scattering in MgF2 is no longer decisive in neutron moderation, and it was decided to consider materials based on plexiglass as a moderator material.In this work we considered Poly-Biz as moderator material and get the neutron beam the same quality as with MgF2 moderator and proton energy 2.3 MeV but at lower proton energy and current that can cause treatment time reducing and allows more reliable neutron generation.For a long time, the development of BNСT was hindered by the lack of charged particle accelerators that provide stable production of a stationary 2.5 MeV 10 mA proton beam. The use of BSA with Poly-Biz allows the use of these accelerators at lower energy, which improves the reliability of their operation, and reduces the therapy time by more than 2 times, which is also important for therapy. Also, the use of such an BSA simplifies the requirements for a charged particle accelerator and this opens up both the possibility of optimizing the developed accelerators and the use of other accelerators that have not yet reached the required parameters.

Measurements of keV-Neutron capture cross sections and capture gamma-ray spectra of 74,76,78,80,82Se

ABSTRACT The neutron capture cross sections and capture γ -ray spectra of 74,76,78,80,82Se were measured in a region from 15 to 100 keV and around 550 keV. A neutron time-of-flight method was used with a ns-pulsed neutron source based on the 7Li(p,n)7Be reaction and a large anti-Compton NaI(Tl) γ -ray spectrometer. A pulse-height weighting technique was applied to the observed γ -ray pulse-height spectra to obtain capture yields. The capture cross sections of 74,76,78,80Se were derived with uncertainties from 4.0 to 5.5% and those of 82Se were derived with uncertainties of 6.5–27% by using the standard capture cross sections of 197Au. The present results of 78,82Se were the first experimental ones above the resolved resonance region. The present results were compared with previous measurements and the evaluated values in JENDL-5.0 and ENDF/B-VIII.0. The evaluations of JENDL-5.0 differ from the present results of 74,76,78,80Se and 82Se by 0.9–51% and 6.9–120%, respectively. The capture γ -ray spectra of 74,76,78,80,82Se were derived by unfolding the observed capture γ -ray pulse-height spectra. The present results were the first experimental ones in the keV region.

Differential cross–section measurements for the proton-induced alpha and deuteron reactions and elastic scattering on 9Be, suitable for Ion beam analysis applications

In the current work the differential cross sections for the proton-induced 9Be(p,d0)8Be and 9Be(p,α0)6Li nuclear reactions (Q-values = 559 and 2125 keV respectively), as well as, the 9Be(p,p0)9Be elastic scattering were measured for 6 backscattering detection angles (θ = 120°, 130°, 140°, 150°, 160° and 170°) covering the Ep,lab = 300–3000 keV energy range with an energy step between 10 and 50 keV. The total estimated uncertainties of the determined cross-section values did not exceed 6.4 % for the elastic scattering, 7.0 % for the 9Be(p,α0)6Li and 9.9 % for the 9Be(p,d0)8Be reaction. Benchmarking measurements were also performed with a suitable thick target in order to validate the obtained cross-section values. The present experimental results constitute three coherent differential cross-section datasets suitable for IBA applications. The measurements were performed at the 4 MV Tandem Dynamitron Laboratory of the Ruhr University Bochum in Germany. The experimental, data analysis and benchmarking procedures are presented in detail.

The Radiation Impact of Delayed Photoneutron Production in ITER Components

Photoneutrons may be generated in beryllium by energetic gamma rays via the reaction 9Be(γ,n)8Be. In ITER, the beryllium layer of the first wall may be the source of such photoneutrons. During plasma operation, these are of insignificant intensity compared with D-T neutrons from the plasma, but after shutdown, photoneutrons produced by decay gammas from neutron-activated material may be significant enough to impact sensitive electronic components in diagnostic or remote handling equipment that would not otherwise be exposed to neutrons. Studies have been performed to characterize the expected photoneutron source and to evaluate the fluxes arising in detailed three-dimensional models of the ITER tokamak. The results show photoneutron fluxes approaching 105 n/cm2·s within the vessel and up to 103 n/cm2·s elsewhere within the bioshield 14 days after shutdown. When first-wall panels are being transported to the Hot Cell Facility after irradiation, a photoneutron flux exceeding 104 n/cm2·s within the transfer cask is predicted 21 days after shutdown. The peak values in the surrounding building are between 102 and 103 n/cm2·s at the same time.

Measurement of energy and directional distribution of neutron ambient dose equivalent for the [formula omitted]Li(p,n)[formula omitted]Be reaction

Double differential neutron fluence distributions were measured in the 7Li(p,n)7Be reaction for proton beam energies 7, 9 and 12 MeV. Seven liquid scintillator based detectors were employed to measure neutron fluence distributions using the Time of Flight technique. Neutron ambient dose equivalents were determined from the measured fluence distribution using ICRP (International Commission on Radiological Protection) recommended fluence to dose equivalent conversion coefficients. Neutron dose equivalents were also measured using a conventional BF3 detector based REM counter. Ambient dose equivalent measured by the REM counter is found to be in agreement with that determined from the neutron fluence spectra within their uncertainties. Angular distributions of the ambient dose equivalents were also determined from the measured fluence distributions at different angles.

Measurement of fast neutron induced (n,γ) reaction cross-section of 152Sm, 154Sm and 150Nd in the energy range of 0.8 to 2 MeV

The (n,γ) reaction cross-section of rare earth stable fission products, such as 152Sm, 154Sm and 150Nd, in the neutron energy range of 0.8 to 2 MeV, obtained from 7Li(p,n)7Be reaction, was measured by neutron activation followed by off-line gamma-ray spectrometry. Natural strontium (natSr) has been established as a fast neutron flux monitor in this work, by measuring the natSr(n,γ+n,n′)87Srm reaction cross-section using 127I(n,γ)128I as monitor reaction. The cross-section for 86Sr(n,γ)87Srm has been determined for the first time to the best of our knowledge. The excellent decay properties of 87Srm and opposite energy dependence of 86Sr(n,γ)87Srm and 87Sr(n,n′)87Srm reactions makes natSr an excellent candidate for neutron flux monitor for wide neutron energy range. The measured (n,γ) cross-section data from the present study has been compared with the literature data, which is very limited along with large scatter in the energy range of 1–2 MeV for these nuclei. The results from the present study, clearly show a need for fresh cross-section evaluations for 152Sm(n,γ)153Sm. For, 154Sm(n,γ)155Sm and 150Nd(n,γ)151Nd reactions, the present data align with one of the data groups among the two which can be broadly identified having difference of about more than ∼50%. The present experimental data has been compared with TALYS 1.96 theoretical model calculations based on Fermi gas level density prescriptions which shows that the cross section values are close to the experimental data at some of the neutron energies. A comparison of the data on fast neutron capture cross-section for N = 90 isotones from the present study and from the literature showed a systematic decrease in the cross-section value with increasing neutron richness of the target nucleus. The cross-section data could be scaled with neutron-proton asymmetry parameter to show a nearly linear behaviour on a logarithmic scale. The data for 154Sm (N = 92) was also observed to follow the same trend.