2n Reaction Research Articles

Stellar Thermonuclear Reaction Rates of Proton Radiative Capture by Closed Light Shell Isotopes

Light isotopes, especially closed shell nuclei, have significance in thermonuclear reactions of the Carbon-Nitrogen-Oxygen (CNO) cycle in stars. In this research, 12C(p, γ) 13N and 14N(p, γ) 15O reactions have been calculated by means of Matlab codes to find the reaction rate across a temperature range of 0.006 to 10 GK using non-resonant parts, as well as the astrophysical S- factor S(E) at low energies. It was concluded that the high binding energy of 12C and 14N nuclei make the reaction less probable thus enabling other competitive processes to develop, which enhances the probability of other competitive proton reactions in the CNO cycle.

17O Destruction Rate in Stars

In recent years, several laboratory studies of CNO cycle-related nuclear reactions have been carried out. Nevertheless, extant models of stellar nucleosynthesis still adopt CNO reaction rates reported in old compilations, such as NACRE or CF88. In order to update these rates, we performed new calculations based on a Monte Carlo R-Matrix analysis. In more detail, a method was developed that is based on the collection of all the available data, including recent low-energy measurements obtained by the LUNA collaboration in the reduced background environment of the INFN-LNGS underground laboratory, on R-Matrix cross-section calculations with the AZURE2 code and on uncertainty evaluations with a Monte Carlo analysis. As a first scientific benchmark case, the reactions 17O(p,γ)18F and 17O(p,α)14N were investigated. Among the different stellar scenarios they can influence, the 16O/17O abundance ratio in RGB and AGB stars is the one that can be directly confirmed from spectroscopic measurements. The aim is to reduce the nuclear physics uncertainties, thus providing a useful tool to constrain deep mixing processes eventually taking place in these stars. In this work, we present the procedure we followed to calculate the 17O(p,γ)18F and the 17O(p,α)14N reaction stellar rates and preliminary comparisons with similar rates reported in widely used nuclear physics libraries are discussed.

Prediction of (n, 2n) reaction cross-sections of long-lived fission products based on tensor model

Prediction of (n, 2n) reaction cross-sections of long-lived fission products based on tensor model

Revised Reaction Rate for the Astrophysical Reaction 18O(p, α)15N via a Global R-matrix Analysis

The 18O(p, α)15N reaction is of particular importance for influencing the abundances of key isotopes such as 19F, 18O, and 15N. Peculiar abundances for these nuclei are observed from spectra or meteorite grains originating in asymptotic giant branch stars. The 18O(p, α)15N could provide a way to explain the discrepancy between the observations and model predictions. A comprehensive R-matrix analysis has been performed for the 18O(p, α)15N reaction by including additional constraints from other reaction channels; in particular, the 15N+α scattering data were involved in the analysis for the first time. All available data were compiled and used in the R-matrix analysis. The fitted resonance parameters are compared with previous works. A revised determination of reaction rate has been extracted, relying on the present fitting parameters. The uncertainties on the corresponding reaction rates were then obtained by a Monte Carlo analysis.

Correction: Study of (n, 2n) reaction cross sections for 107Ag within the energy range of 9–22 MeV

Correction: Study of (n, 2n) reaction cross sections for 107Ag within the energy range of 9–22 MeV

Quantum dynamical study on 15N ＋ 14N14N isotope exchange reactions at high energies

In this study, we conduct quantum dynamical calculations at relatively high energies on the exchange reaction 15N ＋ 14N14N →15N14N ＋ 14N on its ground electronic N3 (4A′′) potential energy surface (PES) utilizing the time-dependent wave packet (TDWP) propagation method. Our primary focus is on analyzing the reaction mechanism for 15N ＋ ortho-14N14N (j = 0) and para-14N14N (j = 1) cases. We also explore the influence of varying J (up to 120) of the three-body system and the initial vibrational level (ν = 1, 5, 10) of the diatom on the reaction probability (RP) for ortho and para configurations.

INVESTIGATION OF THE PARTIAL CHANNEL OF 8Be NUCLEUS GROUND STATE FORMATION IN THE 14N(γ,2α6Li) REACTION

Using the track 4𝜋-detector method (a diffusion chamber arranged in a magnetic field on the way of a beam of bremsstrahlung photons with the final energy 𝐸𝛾max = 150 MeV), the reaction 14N(γ,2α6Li) has been studied. The distributions of events over the excitation energy of 2𝛼-particles were analyzed and a channel of the formation of the 8Be nucleus in the ground state was revealed and has been separated. Events in which the 𝛼-particle pairs correspond to the formation of the 8Be nucleus in the ground state can be reliably identified. The energy and angular distributions of 𝛼 particles at each stage of decay are analyzed.

Calculation of [formula omitted] and [formula omitted] thick targets neutron yields from particle accelerator-induced nuclear reactions using PHITS code

The double-differential cross-sections, and neutron yields of the 9Be(4He,n)12C and 12C(d,n)13N reactions at various energies, have been calculated. The cross-sections for the consider nuclear reactions were obtained using PHITS code based on Monte Carlo method. The calculated data were validated against the available experimental data with varying agreement up to 30MeV. We have suggested the most suitable reaction, at certain energies, for better neutron yield and hence radiotherapy applications.

Neutronic performance of 208Pb-Bi eutectic-cooled fast reactor with uranium nitride fuel (enriched 15N)

Fast reactors (FRs) require more uranium enrichment than LWRs and fuel reprocessing. The solution proposed to address these issues is to use the modified CANDLE burnup scheme on the reactor core. The use of uranium nitride (UN) as fuel was proposed because the UN fuel has several advantages, such as high melting point, high heavy metal density, and large thermal conductivity. However, using UN as a fuel can produce the radioactive isotope 14C via the reaction 14N (n, p)14C. Therefore, in this study, a neutronic analysis was performed in a modified CANDLE fast reactor employing UN and UN (enriched 15N) as fuel using SRAC. The modified CANDLE fast reactor fuelled with UN (99% 15N) has a higher keff than the UN-fuelled reactor with similar parameters. Similarly, the atomic density of fissile nuclides and power density are higher because the 15N isotope has a smaller neutron capture cross-section than the 14N isotope.

Astrophysical S-factor and reaction rate for 15N(p,γ)16O within the modified potential cluster model* *Supported by the Ministry of Science and Higher Education of the Republic of Kazakhstan (AP09259174)

We study radiative capture on the ground state of 16O at stellar energies within the framework of a modified potential cluster model (MPCM) with forbidden states, including low-lying resonances. The investigation of the 15N( )16O reaction includes the consideration of resonances due to transitions and the contribution of the scattering wave in the p + 15N channel due to the transition. We calculated the astrophysical low-energy S-factor, and the extrapolated turned out to be within 34.7−40.4 keV·b. The important role of the asymptotic constant (AC) for the 15N( )16O process with interfering (312) and (962) resonances is elucidated. A comparison of our calculation for the S-factor with existing experimental and theoretical data is addressed, and a reasonable agreement is found. The reaction rate is calculated and compared with the existing rates. It has negligible dependence on the variation of AC but shows a strong impact of the interference of (312) and (962) resonances in reference to the CNO Gamow windows, especially at low temperatures. We estimate the contribution of cascade transitions to the reaction rate based on the exclusive experimental data from Phys. Rev. C. 85, 065810 (2012). The reaction rate enhancement due to the cascade transitions is observed from and reaches the maximum factor ~ 1.3 at . We present the Gamow energy window and a comparison of rates for radiative proton capture reactions 12N( )13O, 13N( ) 14O, 14N( )15O, and 15N( )16O obtained in the framework of the MPCM and provide the temperature windows, prevalence, and significance of each process.

Study of (n,α) reactions of interest for nuclear reactors: the case of19F(n,α)16N with SCALP detector

The19F(n,α)16N cross section is of great interest for the development of the next generation IV reactors that could potentially use molten fluoride salts. Significant differences (up to a factor of 3) have been observed for this nucleus regarding the (n,α) channel. In view of improving our knowledge on this (n,α) reactions, the GrACE group (Groupe Aval du Cycle Electronucl´eaire) of the LPC Caen has developed a new detector named SCALP (Scintillating ionization Chamber for ALPha particle detection in neutron induced reactions). This paper deals with the first experiment carried out with this brand new detector at the new NFS facility (GANIL, Caen, France). After discussing the needs for new measurments of the19F(n,α)16N reaction, the operating procedure of the SCALP detector will be presented, as well as the experiments that have been conducted using it. Furthermore, insights into the data acquired during our experiment, as well as the ongoing data processing and associated multi-channel analysis, will be provided.

Cross-section data for the reactions 12C(3He,p0)14N to 12C(3He,p6)14N at energies up to 6 MeV

The cross-sections of the 12C(3He,px)14N reactions were studied for x = 0...6 at energies from 1.5 to 6 MeV and reaction angles of 135∘ and 175∘ using thin amorphous hydrocarbon (a–C:H) film targets on silicon and chromium substrates. The cross-sections were determined relative to the Rutherford scattering cross-section of 3He from gold, the accuracy of the measured cross-sections ranges from 2 to 4% at 135∘ and 3 to 10% at 175∘. The determined cross-sections were validated using benchmark measurements from bulk carbon targets. The results are presented in graphical and tabular form.

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.

Studying the Yields of Reactions 13C(γ, p), 14N(γ, 2p), and 14N(γ, 2n) on a Pulsed Electron Accelerator with of (12B, 12N) Activity Measured by ΔE Detector Telescopes

Studying the Yields of Reactions 13C(γ, p), 14N(γ, 2p), and 14N(γ, 2n) on a Pulsed Electron Accelerator with of (12B, 12N) Activity Measured by ΔE Detector Telescopes

On the studies of the reactions <sup>13</sup>C(γ, <i>p</i>), <sup>14</sup>N(γ, 2<i>p</i>), and <sup>14</sup>N(γ, 2) at the pulsed electron accelerator with measurements of (<sup>12</sup>B, <sup>12</sup>N)-activity by Δ<i>E-</i>detector telescopes

The issues are considered for studying the yields of the reactions 13C(γ, p)12B, 14N(γ, 2p)12B, and 14N(γ, 2n)12N with measuring (12B, 12N)-activity by telescopes of ΔE-detectors in time between electron accelerator pulses. For the chosen radiators and targets, the fluxes, and spectra of irradiating bremsstrahlung γ-quanta are found. The influence of the parameters of targets and telescopes of ΔE-detectors on production of (12B, 12N)-nuclei and registration of their decay is estimated.

Measurement of the [formula omitted] and [formula omitted] reaction cross-sections and isomeric ratios induced by the 14.8 MeV neutrons

The precise measurement of the (n, 2n) reaction cross-sections of xenon isotopes is of great significance for the diagnosis of the Inertial Confinement Fusion fuel area density ρR. The preparation of xenon samples and how they can be efficiently adsorbed to obtain an optimal reaction cross section are extremely difficult in existing experiments. This work aims to use the 93Nb(n,2n)92mNb reaction cross section as the standard to calculate the cross-sections and isomeric ratio for 134Xe(n,2n)133m,gXe and 136Xe(n,2n)135m,gXe reactions. This work also aims to explore the feasibility of adsorbent selection, the method of adsorption sample and the feasibility of the method used in the laboratory. In this paper, the Geant4 program was used to simulate and calculate the adsorption factors of activated carbon and polymer for standard 152Eu multi-line sources, so as to determine the most suitable adsorption material. Next, the GammaVision analysis software was used to observe whether the characteristic γ-rays released by other isotope reaction products of xenon in the sample and packaging material had an effect on the characteristic γ-rays of the target product. Then, the basic principle of activation method and the relative measurement principle are used to calculate the cross-sections and isomeric ratio for 134Xe(n,2n)133Xe and 136Xe(n,2n)135Xe reactions. Finally, the experimental results are compared and analyzed with the existing data in EXFOR database to verify whether the experimental method is correct.

Measurement of the (n, 2n) reaction cross-sections of iodine and cesium induced by D-T neutrons with covariance analysis* *Supported by the Key Laboratory of Nuclear Data Foundation (JCKY2022201C151), and the National Natural Science Foundation of China (11975113).

The cross-sections of the 127I (n, 2n) 126I and 133Cs (n, 2n) 132Cs reactions at neutron energies of 13.83 ± 0.05, 14.33 ± 0.10, and 14.79 ± 0.10 MeV were measured relative to the 93Nb (n, 2n) 92mNb reaction using the activation technique in combination with off-line γ-ray spectrometry. A neutron beam was generated from the T (d, n) 4He reaction using the K-400 neutron generator at the China Academy of Engineering Physics. Considering the correlations between different attributes, detailed uncertainty propagation was performed using covariance analysis, and the cross-sections were reported with their uncertainties and correlation matrix. The uncertainty of the measurement cross-sections ranged from 4.84 to 5.90%, which is lower than previous experimental data. Furthermore, the theoretical excitation functions of the 127I (n, 2n) 126I and 133Cs (n, 2n) 132Cs reactions were calculated using the TALYS-1.95 and EMPIRE-3.2.3 codes. Then, the experimentally determined cross-sections were analyzed by comparing them with literature data available in the EXFOR database and evaluated nuclear data in the ENDF/B-VIII.0, JEFF-3.3, JENDL-5, BROND-3.1, CENDL-3.2, and TENDL-2021 databases. Compared with the values previously reported in the 13.8-14.8 MeV energy region, the precision of the results obtained in this study was greatly improved. The current experimental results with thorough uncertainties and covariance information are critical for verifying the reliability of the theoretical model and improving the quality of the nuclear database.

Improved S factor of the C12(p,γ)N13 reaction at E=320–620 keV and the 422 keV resonance

The 12C(p,{\gamma})13N reaction is the onset process of both the CNO and Hot CNO cycles that drive massive star, Red and Asymptotic Giant Branch star and novae nucleosynthesis. The 12C(p,{\gamma})13N rate affects the final abundances of the stable 12,13C nuclides, with ramifications for meteoritic carbon isotopic abundances and the s-process neutron source strength. Here, a new underground measurement of the 12C(p,{\gamma})13N cross-section is reported. The present data, obtained at the Felsenkeller shallow-underground laboratory in Dresden (Germany), encompass the 320-620 keV center of mass energy range to include the wide and poorly constrained E = 422 keV resonance that dominates the rate at high temperatures. This work S-factor results, lower than literature by 25%, are included in a new comprehensive R-matrix fit, and the energy of the 1+ first excited state of 13N is found to be 2369.6(4) keV, with radiative and proton width of 0.49(3) eV and 34.9(2) keV respectively. A new reaction rate, based on present R-matrix fit and extrapolation, is suggested.

Precise resonance parameter measurement in the 12C(p,γ)13N astrophysically important reaction

Precise knowledge of the 12C(p,γ)13N reaction cross section is crucial to understand the evolution of various types of red giant stars and to explain their astronomically observed surface 12C/13C abundance ratio. Experimental data show discordance near resonances below Ep=2000 keV. Dedicated measurements using in-beam γ-spectroscopy have been carried out in the vicinity of Ep=460 and 1700 keV to obtain resonance parameters, such as the resonance energy and width. Using a simplified R-matrix model, the following values of resonance energy and width were obtained: Er=459.8±0.8; Γtotal= 38.2±0.5 keV and Er=1685.1±0.7; Γtotal=57.6±0.8 keV given in laboratory system. These values with reduced uncertainties provide new input parameters for future compilations of 12C(p,γ)13N reaction and thus for astrophysics cross-section extrapolations.

Tritium and deuterium release behavior of Li2TiO3-0.5Li4SiO4–Pb ceramic

The neutron multiplier lead (Pb) containing Li2TiO3-0.5Li4SiO4–Pb was prepared, which aimed at the improvement of the tritium release performance of the lithium ceramic without an increase in lithium density. Li2TiO3-0.5Li4SiO4–Pb and that without Pb were irradiated at Kyoto University Research Reactor (KUR) with the thermal neutron flux of 5.5 × 1012 n s−1 cm−2 and the fast neutron flux of 1.2 × 1012 n s−1 cm−2. Fast neutrons can trigger the Pb (n, 2n) reaction. The tritium release experiments were conducted using the tritium thermal desorption spectroscopy (tritium-TDS) system. Compared with Li2TiO3-0.5Li4SiO4, the tritium release rate at the lower temperature range was higher than that for Li2TiO3-0.5Li4SiO4–Pb. The tritium-TDS spectrum was also shifted to the lower temperature side. The isothermal heating experimental results confirmed that tritium in the form of gas species (HT) was controlled by the diffusion process, while the trapping and de-trapping process contributed to the total tritium release. Further, 3 keV D2+ implantation with the fluence of 2.0 × 1022 D m−2 and subsequent TDS measurements were performed. It was shown that the D2 release at the lower temperature side was increased for Li2TiO3-0.5Li4SiO4–Pb. Meanwhile, HD and HDO release at higher temperature side was significantly decreased.