Measurements of the ^(107)Ag neutron capture cross sections with pulse height weighting technique at the CSNS Back-n facility

Silver indium cadmium(Ag–In–Cd) control rod is widely used in pressurized water reactor nuclear power plants,and it is continuously consumed in a high neutron flux environment. The mass ratio of ^(107)Ag in the Ag–In–Cd control rod is 41.44%. To accurately calculate the consumption value of the control rod, a reliable neutron reaction cross section of the ^(107)Ag is required. Meanwhile,^(107)Ag is also an important weak r nucleus. Thus, the cross sections for neutron induced interactions with ^(107)Ag are very important both in nuclear energy and nuclear astrophysics. The(n, γ) cross section of ^(107)Ag has been measured in the energy range of 1–60 eV using a back streaming white neutron beam line at China spallation neutron source. The resonance parameters are extracted by an R-matrix code. All the cross section of ^(107)Ag and resonance parameters are given in this paper as datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00010.

Measurement of neutron capture cross section on^(71)Ga at 2.15 and 3.19 MeV and uncertainty propagation and covariance analysis

The cross section values of the^(71)Ga(n,γ)^(72)Ga reaction are measured,which are 9.14±0.81 mb and 5.74±0.50 mb at 2.15 and 3.19 MeV,respectively.The detailed uncertainty propagation and covariance analysis are also given.The^(7)Li(p,n)^(7)Be reaction was used to generate the neutrons,and the neutron flux was normalized using the^(115)In(n,n′)^(115)In^(m)monitor reaction.The measured cross section data are compared with the data available in the EXFOR database,the data obtained using nuclear reaction model codes EMPIRE-3.2 and TALYS-1.95,and also the evaluated nuclear data from ENDF/B-VIII.0 and JEFF-3.1/A.The comparison shows that our result at 3.19 MeV is in good agreement with those of EMPIRE-3.2 and JEFF-3.1/A.Since there are no other measurements available at3.19 MeV,our data could not be compared with literature data at 3.19 MeV,but they are consistent with the cross section values available at 2.98±0.26 and 3.0±0.1 MeV.Our result at 2.15 MeV is slightly higher than the literature value available in EXFOR,evaluated value,and theoretically predicted result.

Measurement of Br(n,γ)cross sections up to stellar s-process temperatures at the CSNS Back‑n

The neutron capture cross sections(n,γ)of bromine were obtained using the time-of-flight technique at the Back-n facility of the China Spallation Neutron Source.Promptγ-rays originating from neutron-induced capture events were detected using four C_(6)D_(6) detectors.The pulse-height weighting technique and double-bunch unfolding method based on Bayesian theory were used in the data analysis.Background deductions,normalization,and corrections were carefully considered to obtain reliable measurement results.The multilevel R-matrix Bayesian code SAMMY was used to extract the resonance parameters in the resolved resonance region(RRR).The average cross sections in the unresolved resonance region(URR)were obtained from 10 to 400 keV.The experimental results were compared with data from several evaluated libraries and previous experi-ments in the RRR and URR.The TALYS code was used to describe the average cross sections in the URR.The astrophysical Maxwell average cross sections(MACSs)of ^(79,81)Br from kT=5 to 100 keV were calculated over a sufficiently wide range of neutron energies.At a thermal energy of kT=30 keV,the MACS value for ^(79)Br 682±68 mb was in good agreement with the KADoNiS v1.0 recommended value.By contrast,the value of 293±29 mb for ^(81)Br was substantially higher than that of the evaluated database and the KADoNiS v1.0 recommended value.

Neutron capture cross section of ^(169)Tm measured at the CSNS Back-n facility in the energy region from 30 to 300 keV

The capture cross sections of the ^(169)Tm(n,γ)reaction were measured at the back streaming white neutron beam line(Back-n)of the China Spallation Neutron Source(CSNS)using four C_(6)D_(6) liquid scintillation detectors.The background subtraction,normalization,and correction were carefully considered in the data analysis to obtain accurate cross sections.For the resonance at 3.9 eV,the R-matrix code SAMMY was used to determine the resonance parameters with the internal normalization method.The average capture cross sections of ^(169)Tm for energy between 30 and 300 keV were extracted relative to the ^(197)Au(n,γ)reaction.The measured cross sections of the ^(169)Tm(n,γ)reaction were reported in logarithmically equidistant energy bins with 20 bins per energy decade with a total uncertainty of 5.4%-7.0% in this study and described in terms of average resonance parameters using a Hauser-Feshbach calculation with fluctuations.The point-wise cross sections and the average resonance parameters showed fair agreement with the evaluated values of the ENDF/B-Ⅷ.0 library in the energy region studied.

Capture cross sections of ^(15)N(n,γ)^(16)N at astrophysical energies

We have reanalyzed reaction cross sections of 16N on a 12C target. The nucleon density distribution of 16N, especially surface density distribution, was extracted using the modified Glauber model. On the basis of dilute surface densities, the 15N（n, γ）16N reaction is discussed within the framework of the direct capture reaction mechanism. The calculations agree quite well with the experimental data.

Influence of electron correlations on double-capture process in proton helium collisions

The first-order correct-boundary Coulomb–Born distorted-wave approximation is used to study the double-electron capture by protons from the ground-state helium atoms at intermediate and high impact energies. The differential double capture cross sections are obtained as a function of the projectile scattering angle and the total cross sections as a function of the impact energy. In the considered range of impact energy, our calculation shows that although the results are not so sensitive to the static inter-electronic correlations in the initial channel, the strong final-state correlations have a large effect on the magnitudes of the double capture cross sections. The calculated differential and integral cross sections are compared with their available experimental values. The comparison shows a good agreement between the present calculations and the measurements. The comparison of the integral cross sections shows that the present approach is compatible with other theories.

Analysis of influencing factors on the method for determining boron concentration and dose through dual prompt gamma detection

A method based on the cross-sectional relationship between^(10)B(n,α)^(7)Li and^(1)H(n,γ)^(2)H was proposed to detect and reconstruct the three-dimensional boron concentration/dose distribution in vivo during boron neutron capture therapy(BNCT).Factors such as the neutron energy,fluence rate,and degree of non-uniform distribution of the boron concentration in a voxel may affect the results of this method.A theoretical analysis of the accuracy of the method using a Monte Carlo simulation shows that the determining error is generally less than 1%under different tumor locations and neutron source configurations.When the voxel size is larger than 0.4 cm,the determining error might be higher for a non-uniformly distributed boron concentration in the voxel because of the changes in the neutron energy and fluence rate.In conclusion,the proposed method enables an accurate threedimensional boron determination in vivo during BNCT.

The Radioactivity of Nuclei &Solar Oscillations: New Experiments

The experimental detection of the hidden periodicities in the activity of various radioactive sources which were observed by different instruments and which coincided with the period of the free oscillations of the Sun gave an impetus to the further research. The simultaneous recording of gamma rays from two radioactive sources revealed the elements of synchronism and the periods of solar oscillations as well as the phase delay for the different sources in the obtained time series. A neutrino detector has been designed and tested, the advanced schemes for neutrino detection are developed, and the impact of the neutrino source on the radioactive matter is explored. The search for the new principles for creating the emitters of neutrino beams is conducted.

Single‑Photon Sources Based on Novel Color Centers in Silicon Carbide P–I–N Diodes: Combining Theory and Experiment

Point defects in the crystal lattice of SiC,known as color centers,have recently emerged as one of the most promising single-photon emitters for non-classical light sources.However,the search for the best color center that satisfies all the requirements of practical applications has only just begun.Many color centers in SiC have been recently discovered but not yet identified.Therefore,it is extremely challenging to understand their optoelectronic properties and evaluate their potential for use in practical single-photon sources.Here,we present a theoretical approach that explains the experiments on single-photon electroluminescence(SPEL)of novel color centers in SiC p-i-n diodes and gives the possibility to engineer highly efficient single-photon emitting diodes based on them.Moreover,we develop a novel method of determining the electron and hole capture cross sections by the color center from experimental measurements of the SPEL rate and second-order coherence.Unlike other methods,the developed approach uses the experimental results at the single defect level that can be easily obtained as soon as a single-color center is identified in the i-type region of the SiC p-i-n diode.

Systematical law of (n, γ) reaction cross sections of even-even nuclei

We have derived a formula for the neutron radiative capture cross section in the framework of a statistical model approach to nuclear reactions. Based on this formula, new systematics are established between the （n, y） reaction cross section and the energy level density of a compound nucleus or a relative neutron excess of an even-even target nucleus for neutron incident energy above the resonance region to MeV. Good agreement with experimental data suggests that this new systematical law is helpful to nalyze the experimental data.

Monte Carlo simulation for pulsed neutron-neutron logging in fractured and cavernous carbonate formation

The influence of carbonate formation on Pulsed Neutron logging(such as Pulsed Neutron-Neutron logging)is quite different from that of sandstone due to the complexity of reservoir architecture and the development of fracture in carbonate reservoir.To study the factors affecting Pulsed Neutron-Neutron(PNN)logging in carbonate formation,the responses on fracture or cave are simulated by Monte Carlo method,getting the relationships among the macroscopic capture cross section(Σ),the count ratio of the thermal neutron at far spacing and near spacing detectors(RATIO),the fracture porosity,oil-bearing and shale content of fracture.The results show that PNN logging can be used to detect caves,and there exist linear relationships among the macroscopic capture cross section(Σ),the count ratio(RATIO)and the above factors.The research findings in this paper provides theoretical basis for the interpretation and data correction of the PNN logging in carbonate reservoirs.

The C_(6)D_(6)detector system on the Back-n beam line of CSNS

Introduction The neutron capture cross sections are very important in the field of nuclear device design and basic physics research.Hydrogen-free liquid scintillator such as C_(6)D_(6)detectors are widely used in the neutron capture cross-sectional measurements for the low neutron sensitivity and fast time response.The Back-n white neutron source at China Spallation Neutron Source is the first spallation white neutron source in China,and it is suitable for neutron capture cross-sectional measurement.Materials and methods A C_(6)D_(6)detector system was built in the Back-n experimental station.The pulse height weighting technique was used to determine the system’s detection efficiency.The response to gamma rays of the C_(6)D_(6)detector was measured,and the energy resolution function was determined.Monte Carlo simulation with Geant4 code was carried out to get the weighting function of this C_(6)D_(6)detector system.Additionally,the systematic uncertainty of the weighting function was also determined.Conclusion According to the experimental and simulation results,this C_(6)D_(6)detector system can be used to measure neutron capture cross section.