Capture Reaction Research Articles

Effects of three-body forces on the [formula omitted]He–[formula omitted] radiative capture process

The 3He(α,γ)7Be radiative capture reaction has studied using the pionless Effective Field Theory (EFT) approach to determine the cross-section, astrophysical S-factor, and reaction rate in astrophysical energies. We have applied the Faddeev equation method, while taking three-body forces into account. The scattering amplitude in the E1 and E2 transitions to the 7Be ground state (lf=1,Jf=3/2), has computed at Leading Order (LO) considering the Coulomb effects. The thermonuclear reaction results have normalized using NACRE 1999 experimental data. All results are compared with certain theoretical and experimental data and there is good agreement with this data.

Stellar neutron capture reactions at low and high temperature

The determination of astrophysical reaction rates requires different approaches depending on the conditions in hydrostatic and explosive burning. The focus here is on astrophysical reaction rates for radiative neutron capture reactions. Relevant nucleosynthesis processes not only involve the s-process but also the i-, r- and gamma -processes, which from the nuclear perspective mainly differ in the relative interaction energies of neutrons and nuclei, and in the nuclear level densities of the involved nuclei. Emphasis is put on the difference between reactions at low and high temperature. Possible complications in the prediction and measurement of these reaction rates are illustrated and the connection between theory and experiment is addressed.

Neptunium mononitride as a target material for Pu-238 production

Deep space exploration requires specialized sources for both thermal and power applications. Radioactive decay heat of plutonium-238 (238Pu) provides these sources in the form of radioisotope thermoelectric generators (RTGs). The238Pu is producedvianeutron capture reaction involving neptunium-237 (237Np) target material. Continual optimization of237Np target materials and evaluation of potential alternative targets for production of238Pu RTGs are advantageous for meeting ongoing space power system resource requirements. Current production of238Pu for RTGs for the United States space program utilizes neptunium dioxide (237NpO2) targets; however, the use of neptunium mononitride (237NpN) presents an opportunity to increase the mass of237Np per target compared to the dioxide form, as well as increase the thermal conductivity of the target. To assess the viability of a237NpN target material, the material chemistry must be thoroughly evaluated, including synthesis methods and dissolution and reprocessing schemes. This review presents a summary of synthesis pathways for237NpN based on published literature on actinide mononitrides. Specific literature on237NpN is limited, necessitating evaluation of other actinide systems to gather parallels. This suggests a need for additional experimental studies on237NpN. A particular limitation in the existing literature is a lack of information on the differences in material characteristics, such as morphology, particle size, and trace chemical impurities, as a function of synthesis method. These parameters may affect subsequent reactor performance or dissolution of irradiated targets. The evaluation of existing literature is presented with a focus on the efficacy of237NpN targets for238Pu production.

Dynamics analysis of knee joint during sit-stand movement

Sit-stand movement is one of the most common movement behaviors of the human body. The knee joint is the main bearing joint of this movement. Thus, the dynamic analysis of knee joint during this movement has deeply positive influences. According to the principle of moment balance, the dynamics of the knee joint during the movement were analyzed. Furthermore, combined with the data obtained from optical motion capture and six-dimensional ground reaction force test, the curve of knee joint torque was calculated. To verify the accuracy of the analysis of dynamic, the human body model was established, the polynomial equations of angle and angular velocity were fitted according to the experimental data, and the knee joint simulation of the movement was carried out. The result revealed that in terms of range and trend, the theoretical data and simulation data were consistent. The relationship between knee joint torque and ground reaction force was revealed based on the variation law of knee joint torque. During the sit-stand movement, the knee joint torque and the ground reaction force were directly proportional to each other, and the ratio was 5 to 6. In the standing process, the acceleration first increased and then decreased and finally increased in reverse, and the maximum knee torque occurred at an angle of about 140°. In the sitting process, the torque was maximized in the initial stage. The results of the dynamics analysis of knee joint during sit-stand movement are beneficial to the optimal design and force feedback control of seated rehabilitation aids, and can provide theoretical guidance for knee rehabilitation training.

R -matrix analysis of elastic scattering, phase shifts, and radiative capture reaction cross sections in the α+α system

The unstable nucleus $^8$Be, with its two $\alpha$-cluster configuration, is the doorway to the formation of heavier $\alpha$-cluster nuclei. Most importantly, its the precursor of the production of $^{12}$C through the Hoyle state, a resonance state of three $\alpha$ clusters, in the helium burning phase of a massive star. The nucleus exhibits a ground state band of rotational states established through $\alpha-\alpha$ scattering experiments. A subsequent precision particle-$\gamma$ coincidence measurement of the electromagnetic transition between the 4$^+\rightarrow$ 2$^+$ excited states also corroborated the evidence for a highly deformed dumb-bell shaped structure of $^8$Be. A simultaneous phenomenological R-matrix analysis of the measured capture reaction cross sections along with the elastic excitation function and phase shift data has been performed. The resulting reduced transition strength of 21.96$\pm$3.86 $e^2 fm^4$ compares well with the estimated experimental value of 21.0$\pm$2.3 e$^2$ fm$^4$. The R-matrix yield of the B($E2$) value is closer to the prediction of cluster model but about 19$\%$ less than the {\it ab initio} result.

Reaction rate of radiative p12N capture

The S-factor of radiative p12N capture at energies from 20 keV to 5 MeV was considered within the modified potential cluster model with forbidden states, considering the first resonance at Ex = 2.69(5) MeV. It was shown that one can obtain the astrophysical S-factor based on potentials consistent with the bound state energies and asymptotic constant values. According to the theoretical total cross sections, the calculation of the p12N capture reaction rate is made at temperatures from 0.001 to 10 T9. The calculated results for the reaction rate are approximated by analytical expression, which simplifies their use in applied research.

Original e− Capture Cross Sections for Hot Stellar Interior Energies

The nuclear electron capture reaction possesses a prominent position among other weak interaction processes occurring in explosive nucleosynthesis, especially at the late stages of evolution of massive stars. In this work, we perform exclusive calculations of absolute e−-capture cross sections using the proton–neutron (pn) quasi-particle random phase approximation. Thus, the results of this study can be used as predictions for experiments operating under the same conditions and in exploring the role of the e−-capture process in the stellar environment at the pre-supernova and supernova phase of a massive star. The main goal of our study is to provide detailed state-by-state calculations of original cross sections for the e−-capture on a set of isotopes around the iron group nuclei (28Si, 32S, 48Ti, 56Fe, 66Zn and 90Zr) that play a significant role in pre-supernova as well as in the core–collapse supernova phase in the energy range 0≤E≤50 MeV.

Stability analysis of supermassive primordial stars: a new mass range for general relativistic instability supernovae

ABSTRACT Observed supermassive black holes in the early Universe have several proposed formation channels in part because most of these channels are difficult to probe. One of the more promising channels, the direct collapse of a supermassive star has several possible probes including the explosion of a helium-core supermassive star triggered by a general relativistic instability. We develop a straightforward method for evaluating the general relativistic radial instability without simplifying assumptions and apply it to population III supermassive stars taken from a post Newtonian stellar evolution code. This method is more accurate than previous determinations and it finds that the instability occurs earlier in the evolutionary life of the star. Using the results of the stability analysis, we perform 1D general relativistic hydrodynamical simulations, and we find two general relativistic instability supernovae fuelled by alpha capture reactions as well as several lower mass pulsations, analogous to the puslational pair instability process. The mass range for the events ($2.6-3.0\times 10^4{\rm M}_\odot$) is lower than that had been suggested by previous works ($5.5\times 10^4{\rm M}_\odot$), because the instability occurs earlier in the star’s evolution. The explosion may be visible to among others JWST, while the discovery of the pulsations opens up additional possibilities for observation.

Magnetic dipole transitions in 9Be(p,γ)10B

The proton radiative capture reactions are crucial in nuclear astrophysics. 9Be(p,γ)10B is important in stellar and primordial nucleosynthesis. In the present work, we compute the astrophysical S-factor for 9Be(p,γ)10B by employing the potential model (PM) for the magnetic transitions. Moreover, we revised the nuclear structure features and spectroscopic properties of the 10B nucleus under the PM approach.

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.

A comparison of cross sections for Selenium -73 radioisotopes produced by accelerators and reactors

Background: Selenium-73 with half- life of 7.15 hour emits β+ in nature and has six stable isotopes which are ( 74Se,76Se,77Se,78Se,80Se and 82Se ). Selenium-73 has many applications in technology and radioselenium compounds of metallic have found various applications in medicine. Objective: To make a comparison between different reactions that produced cross sections of Se-73 radioisotopes. Subjects and methods: The feasibility of the production of Selenium -73 via various nuclear reactions was investigated. Excitation functions of 73Se production by the reactions of 75As (p,3n), 169Tm( d,x), 74Se, natSe, natBr (p,x) , 75As (d,4n), natGe (3He,x), 70Ge (α, n), and 72Ge (α, 3n) and neutron capture were calculated using the available data in the international libraries in accordance with SRIM code . Theoretical calculations of the thick target integral yields were deduced using the calculated cross sections by using Matlab program Results: When proton induced reaction on 75As, 74Se, natSe and natBr to obtain 73Se, the reaction 75As(p,3n) with range of energy (22.5 to 45.5 MeV) and the maximum cross section is 315 mb at 36.5 MeV gives maximum yield (2*106 GBq/C).while for the reaction 75As (d,4n) 73Se with range of energy (25 to 56 MeV) , and maximum cross sections is 30 mb at 43MeV gives (0.085*106 GBq/C). The three reactions natGe (3He,x) , 70Ge (α,n) and 72Ge (α,3n) show that the best reaction to obtain 73Se is 72Ge (α,3n) within the range of energy (27 to 46 MeV) and maximum cross sections 494 mb at 42MeV give the maximum yield (0.03*106 GBq/C). Conclusion: the use of proton as projectile is best compared with other particles in order to get maximum isotopes production yield of 73Se.

Reaction rate of radiative n6Li capture in the temperature range from 0.01 to 10 T9

We consider the rate of radiative n6Li capture reaction in the temperature range from 0.01 to 10 T9 within the framework of the modified potential cluster model with forbidden states. The total cross sections are calculated for capture to the ground, and the first excited states of the 7Li nucleus in the n6Li channel in the energy range from 10 meV to 5 MeV. Analytical expressions approximate the total cross-section at low energies and the reaction rate over the entire considered temperature range.

In vivo evaluation of the effects of combined boron and gadolinium neutron capture therapy in mouse models

While boron neutron capture therapy (BNCT) depends primarily on the short flight range of the alpha particles emitted by the boron neutron capture reaction, gadolinium neutron capture therapy (GdNCT) mainly relies on gamma rays and Auger electrons released by the gadolinium neutron capture reaction. BNCT and GdNCT can be complementary in tumor therapy. Here, we studied the combined effects of BNCT and GdNCT when boron and gadolinium compounds were co-injected, followed by thermal neutron irradiation, and compared these effects with those of the single therapies. In cytotoxicity studies, some additive effects (32‒43%) were observed when CT26 cells were treated with both boron- and gadolinium-encapsulated PEGylated liposomes (B- and Gd-liposomes) compared to the single treatments. The tumor-suppressive effect was greater when BNCT was followed by GdNCT at an interval of 10 days rather than vice versa. However, tumor suppression with co-injection of B- and Gd-liposomes into tumor-bearing mice followed by neutron beam irradiation was comparable to that observed with Gd-liposome-only treatment but lower than B-liposome-only injection. No additive effect was observed with the combination of BNCT and GdNCT, which could be due to the shielding effect of gadolinium against thermal neutrons because of its overwhelmingly large thermal neutron cross section.

Efficacy of the symmetry-adapted basis for ab initio nucleon-nucleus interactions for light- and intermediate-mass nuclei

We study the efficacy of a new ab initio framework that combines the symmetry-adapted (SA) no-core shell-model approach with the resonating group method (RGM) for unified descriptions of nuclear structure and reactions. We obtain ab initio neutron-nucleus interactions for 4He, 16O, and 20Ne targets, starting with realistic nucleon-nucleon potentials. We discuss the effect of increasing model space sizes and symmetry-based selections on the SA-RGM norm and direct potential kernels, as well as on phase shifts, which are the input to calculations of cross sections. We demonstrate the efficacy of the SA basis and its scalability with particle numbers and model space dimensions, with a view toward ab initio descriptions of nucleon scattering and capture reactions up through the medium-mass region.

Deuteron-induced nonelastic cross sections based on the intranuclear cascade model with independent incident particles under interaction potentials

Deuteron-induced nonelastic cross sections are studied in an extended intranuclear cascade (INC) model. A three-body framework of proton, neutron, and target is introduced into the INC model to incorporate naturally the decomposition and capture reactions from weakly bound deuterons. This framework includes three types of interaction potential, namely proton-target, neutron-target, and proton-neutron, the last of which causes the two nucleons in the deuteron to oscillate and play an important role in its breakup. The calculated results reproduce well the experimental data for $^{12}\mathrm{C}, ^{40}\mathrm{Ca}, ^{58}\mathrm{Ni}$, and $^{208}\mathrm{Pb}$ targets with almost the same parameters as those determined previously for nucleon-induced nonelastic reactions. It is found that the contribution of the two-nucleon collision process increases with target size, that the contribution of the capture processes is limited to a narrow region at low energy for lighter targets, and that the contribution of the breakup process is relatively small compared to other processes. It is also concluded that discrete-level-constraint effects dominate in the low-energy region for light nuclei such as $^{12}\mathrm{C}$, while Coulomb effects dominate in the low-energy region for heavy nuclei. This result is consistent with the INC model of nucleon incidence, which explains well the nucleon-induced nonelastic cross sections at low energies.

Analysis of boron neutron capture reaction sensitivity using Monte Carlo simulation and proposal of a new dosimetry index in boron neutron capture therapy.

Boron neutron capture therapy is a cellular-scale heavy-particle therapy. The factor determining the biological effects in the boron neutron capture reaction (BNCR) is the value of n}{}{alpha}_{boron}, which is the alpha component in the Linear Quadratic (LQ) model. Recently, the factor determining the value of n}{}{alpha}_{boron} has been revealed to correspond to the structural features of the tumor tissue. However, the relationship and mechanism have yet to be thoroughly studied. In this study, we simulated BNCR in tissues using the Monte Carlo simulation technique and examined the factors that determine the value of n}{}{alpha}_{boron}. According to this simulation, the nuclear-cytoplasmic (N/C) ratio, nuclear diameter and heterogeneity of the distribution of boron in the tissue have been suggested to determine the value of n}{}{alpha}_{boron}. Moreover, we proposed Biological Effectivity (BE) as a new dosimetry index based on the surviving fraction (SF), extending the concept of absolute biological effectiveness (ABE) in a previous report.

Ni/support-CaO bifunctional combined materials for integrated CO2 capture and reverse water-gas shift reaction: Influence of different supports

Integrated CO2 capture and utilisation (ICCU) is a promising strategy for restricting carbon emissions and achieving carbon neutrality. Bifunctional combined materials (BCMs), containing adsorbents and active catalysts, are widely applied in this process. Producing syngas via reverse water–gas shift reaction (RWGS) and integrating with Fischer-Tropsch (F-T) synthesis is an attractive and valuable CO2 utilisation route. This work investigated a series of Ni/support-CaO BCMs (supports = ZrO2, TiO2, CeO2 and Al2O3) for the integrated CO2 capture and RWGS (ICCU-RWGS) process. The Ni/support-CaO BCMs were prepared by physically mixing various metal oxide supports loaded Ni with sol–gel derived CaO. The ICCU-RWGS performance (CO2 conversion, CO yield and CO generation rate) of these BCMs followed the order during tested conditions (550–750 °C): Ni/CeO2-CaO > Ni/TiO2-CaO > Ni/ZrO2-CaO > Ni/Al2O3-CaO. A comprehensive characterisation of Ni/support materials showed that Ni/CeO2 had the characteristics of stronger basicity, optimal Ni dispersion and improved NiO reducibility, which led to the outperforming ICCU-RWGS activity over Ni/CeO2-CaO (e.g. 56.1% CO2 conversion, 2.68 mmol g−1 CO yield and ∼100% CO selectivity at 650 °C). Furthermore, the Ni/CeO2-CaO BCM showed a stable, yet, self-optimising catalytic performance during the cyclic ICCU-RWGS reaction over 20 cycles. The TEM characterisation suggested that was ascribed to the volume expansion and shrinkage of CaO in the cyclic adsorption–desorption altering the distance between the adsorbent and Ni/CeO2, resulting in an enhanced CO2 conversion during the cycle.

Li6(p,γ)Be7reaction rate in the light of the new data of the Laboratory for Underground Nuclear Astrophysics

We present new calculations of the astrophysical $S-$factor and reaction rate for the $^{6}$Li$(p,\gamma )^{7}$Be reaction at energies of 10 keV to 5 MeV in the framework of a modified potential cluster model with forbidden states, including low lying resonances. The astrophysical $S(E)-$factor is compared with the available experimental data and calculations done within different models. The results for the $S-$factor are in good agreement with the data set (for $E<0.3$ MeV) and calculations (for $E<0.6$ MeV) of LUNA collaboration (Phys. Rev. C 102$,$ 052802, 2020). The recommended extrapolated zero value $S(0)$ turned out to be 101 eV $\cdot $ b. Using the theoretical total cross-sections$,$ the $^{6}$Li$(p,\gamma)^{7} $Be capture reaction rate is calculated at temperatures ranging from 0.01 to 10 $T_{9}$ and compared with NACRE and NACRE II. Analytical expressions for the $S-$factor and reaction rate are given, and the effect of low-lying resonances on the reaction rate is estimated. We suggest to update the NACRE and NACRE II databases in light of the new LUNA data and present calculations.

Gamow shell model description of the radiative capture reaction Li8(n,γ)Li9

Background: The $^{8}\mathrm{Li}(n,\ensuremath{\gamma})^{9}\mathrm{Li}$ reaction plays a critical role in several reaction chains leading to the nucleosynthesis of $A&gt;12$ nuclei. Due to unstable nature of $^{8}\mathrm{Li}$ and the unavailability of neutron targets, direct measurements of this reaction are exceedingly difficult. Only upper limits of this cross section, provided by the indirect experiments, have been obtained so far.Purpose: In this work, we use the Gamow shell model (GSM) in the coupled-channel representation (GSM-CC) to study the properties of $^{9}\mathrm{Li}$ and the radiative capture reaction $^{8}\mathrm{Li}(n,\ensuremath{\gamma})^{9}\mathrm{Li}$.Method: GSM-CC is a theoretical framework allowing for the description of both nuclear structure and reaction cross sections. In GSM-CC calculations, a translationally invariant Hamiltonian is used with a finite-range two-body interaction tuned to reproduce the low-energy spectra of ${}^{8,9}\mathrm{Li}$. The reaction channels are built by coupling wave functions of the ground state ${2}_{1}^{+}$, the first-excited state ${1}_{1}^{+}$, and the first resonance state ${3}_{1}^{+}$ in $^{8}\mathrm{Li}$ with the neutron wave function of the projectile in different partial waves. In the calculation of $^{8}\mathrm{Li}(n,\ensuremath{\gamma})^{9}\mathrm{Li}$ cross section, all relevant $E1$, $M1$, and $E2$ transitions from the initial continuum states to the final bound states ${3/2}_{1}^{\ensuremath{-}}$, ${1/2}_{1}^{\ensuremath{-}}$ and the resonance ${5/2}_{1}^{\ensuremath{-}}$ of $^{9}\mathrm{Li}$ are included.Results: The GSM-CC approach reproduces the experimental low-energy spectrum, neutron emission threshold, and spectroscopic factors in $^{9}\mathrm{Li}$. The calculated reaction rate is consistent with the experimental upper limit of the reaction rate obtained in the indirect measurements at stellar energies.Conclusion: The GSM-CC calculations suggest that the $^{8}\mathrm{Li}(n,\ensuremath{\gamma})^{9}\mathrm{Li}$ reaction does not reduce significantly heavy-element production via the main chain $^{7}\mathrm{Li}(n,\ensuremath{\gamma})^{8}\mathrm{Li}(\ensuremath{\alpha},n)^{11}\mathrm{B}(n,\ensuremath{\gamma})^{12}\mathrm{B}({\ensuremath{\beta}}^{+})^{12}\mathrm{C}$. Major contribution to the calculated cross section is given by the direct $E1$ transition to the ground state of $^{8}\mathrm{Li}$. The contribution of excited states to the reaction rate does not exceed $\ensuremath{\approx}20$% of the total reaction rate.

Nuclear Data–Induced Uncertainty of Criticality in Solid-Moderated and Solid-Reflected Cores with Highly Enriched Uranium Fuel at Kyoto University Critical Assembly

Nuclear data–induced uncertainty of criticality is successfully analyzed by combining the eigenvalue calculations, the uncertainty, and the reduction of uncertainty with the use of the KENO-VI code, the TSUNAMI-3D and the TSURFER modules of the SCAL6.2.4 code system, respectively. The comparative study of conventional and revised S(α, β) applications is also conducted by KENO-VI. Notably, the KENO-VI analyses reveal the difference between the experimental and numerical results of criticality and the neutron spectrum dependence of criticality on the H/U ratio in the solid-moderated and solid-reflected cores at the Kyoto University Critical Assembly (KUCA). The difference is identified as the leading cause of uncertainty in the 235U fission spectrum (χ value) through the combined use of the uncertainty and the cross-section adjustment by TSUNAMI-3D and TSURFER, respectively, especially that the highly enriched uranium (HEU) fuel is loaded into the KUCA cores. Also, the neutron spectrum dependence of criticality is attributable to the uncertainty induced by the cross-section data of 235U capture, 27Al elastic scattering, and inelastic scattering reactions in the HEU fuel plate and to the 1H capture reactions in the polyethylene moderator through the TSUNAMI-3D analyses.