Resonance Neutron Capture Research Articles

Measurement of thermal neutron capture cross-section and resonance integral for the 165Ho(n,γ)166gHo reaction by the activation method

The thermal neutron capture cross-section and resonance integral for the 165Ho(n,γ)166Ho reaction were measured experimentally by the activation method. Holmium oxide, manganese oxide and cobalt oxide powders, all dissolved in a mixture of hydrochloric acid and nitric acid, were irradiated within and without cadmium covers in the Tehran Research Reactor. The measured value of the thermal neutron cross-section relative to the 55Mn(n,γ)56Mn and 59Co(n,γ)60Co monitor reactions (with thermal neutron cross-section of 13.3±0.1b and 37.18±0.06b) was 58.6±1.8b. The result was in a good agreement with the most previously reported values. Also the resonance integral was determined relative to the 55Mn(n,γ)56Mn and 59Co(n,γ)60Co monitor reactions with the reference value of 14.0±0.3 and 75.9±2.0, respectively. The measured resonance integral of the 165Ho(n,γ)166Ho reaction at the cadmium cut-off energy of 0.55eV was 650±31. The result was measured with high precision and compared with other measurements in the literature.

중성자 비행시간법을 이용한 인듐의 공명에너지 동정에 관한 연구

Prompt gamma ray from the natural Indium sample was measured by using an assembly of BGO() scintillation detectors in the neutron energy region from 1 to 300 eV. The assembly was composed of pieces of BGO. The spectrometer was composed geometrically as total energy absorption detector. 46-MeV electron linear accelerator which is located at Research Reactor Institute, Kyoto University used for neutron sources from photonuclear reaction. The measurement of the neutron capture resonances was performed to below neutron energy 1 keV, because of strong X-ray effect from photonuclear reaction in Ta target and short distance from the target to an assembly of detector. The distance of neutron flight path is . The large neutron capture resonances were measured from 1 to 400 eV. The energy in the capture resonance was compared with the evaluated values. The large resonances were seen in the present measurement. General agreement can be seen between the present measurement and the previous evaluated data in relevant energy region. In the present study, we measured the continues resonance structure above 1 keV neutron energy region. 91.49 eV new neutron capture resonance was found in present measurement.

The decays of 70,72Ga to levels of 70,72Ge and the neutron capture cross sections of 69,71Ga

The decays of 21-min 70Ga and 14-h 72Ga have been studied from neutron-irradiated Ga. Several discrepancies in previous studies are resolved and inconsistencies in the previous 72Ge data set are addressed. New values are proposed for the energies and β-decay branchings of the 72Ge levels. Energies and intensities of the 70Ga γ rays are also discussed. A new measurement and critical discussion of the 72Ga half-life is offered. Measurements of the 69Ga and 71Ga thermal neutron capture cross sections and resonance integrals are also reported.

Neutron resonance spectroscopy for the characterization of materials and objects

The resonance structure in neutron induced reaction cross sections can be used to determine the elemental compositions of materials or objects. The occurrence of resonances is the basis of neutron resonance capture analysis (NRCA) and neutron resonance transmission analysis (NRTA). NRCA and NRTA are fully non-destructive methods to determine the bulk elemental composition without the need of any sample preparation and resulting in a negligible residual activity. They have been applied to determine the elemental composition of archaeological objects and to characterize reference materials used for cross section measurements. For imaging applications a position sensitive neutron detector has been developed within the ANCIENT CHARM project. The detector is based on a 10 × 10 array of 6Li-glass scintillators mounted on a pitch of 2.5 mm, resulting in a 25 × 25 mm2 active area. The detector has been tested at the time-of-flight facility GELINA and used at the ISIS spallation source to study cultural heritage objects.

Measurement of thermal neutron capture cross section and resonance integral of the 138Ba( n, γ) 139Ba reaction using 55Mn( n, γ) 56Mn as a monitor

The thermal neutron capture cross section ( σ o ) and the resonance integral cross section ( I o ) of the 138Ba( n, γ) 139Ba reaction have been measured by the activation method using the Ghana Research Reactor-1 (GHARR-1). The barium and manganese targets were irradiated within and without a cadmium capsule. The result of the thermal neutron capture cross section for the 138Ba( n, γ) 139Ba reaction is 0.53 ± 0.01barns. The result was obtained relative to the reference value 13.2 barns of the 55Mn( n, γ) 56Mn reaction. The resonance integral cross section for the 138Ba( n, γ) 139Ba reaction was also measured relative to the reference value of 13.9 barns for the 55Mn( n, γ) 56Mn reaction. The present resonance integral cross section for the 138Ba( n, γ) 139Ba reaction is 0.380 ± 0.005 barns. The previous measurements of the σ o and I o of the reaction 138Ba( n, γ) 139Ba were reviewed and the difference between the present values and the previous results were discussed. The present work was undertaken with the aim to contribute to the experimental basis of σ o and I o evaluations.

A Neutron Resonance Capture Analysis Experimental Station at the ISIS Spallation Source

Neutron resonance capture analysis (NRCA) is a nuclear technique that is used to determine the elemental composition of materials and artifacts (e.g., bronze objects) of archaeological interest. NRCA experiments are mostly performed at the GELINA facility in Belgium, a pulsed neutron source operating with an electron linear accelerator. Very intense fluxes of epithermal neutrons are also provided by spallation neutron sources, such as the ISIS spallation neutron source in the United Kingdom. In the present study, the suitability of the Italian Neutron Experimental Station (INES) beam line for NRCA measurements is assessed using a compact (n, γ) resonance detector made of a Yttrium-Aluminum-Perovskite (YAP) scintillation crystal coupled with a silicon photomultiplier (SiPM) readout. The measurements provided a qualitative recognition of the composition of the standard sample, a lower limit for the sensitivity for NRCA for almost-in-traces elements, and an estimation of the relative isotopic concentration in the sample.

Impact of the phonon coupling on the radiative neutron capture

Inclusion of the coupling of quasiparticle degrees of freedom with phonon degrees is a natural extention of the standard QRPA approach. The paper presents the quantitative impact of this phonon coupling on the dipole strength and radiative neutron capture for the stable 124Sn and very exotic 150Sn isotopes, as an illustration, using the self-consistent version of the Extended Theory of Finite Fermi Systems. It was found that the phonon contribution to the pygmy-dipole resonance and radiative neutron capture cross section is increased with the (N − Z) difference growth. The results show that the self-consistent nuclear structure calculations are important for unstable nuclei, where phenomenological approaches do not work.

A detector system for neutron resonance capture imaging

Neutron resonance capture analysis (NRCA) is used in the Ancient Charm project to determine element concentrations in cultural heritage objects. NRCA employs gamma-ray detectors to determine time-of-flight spectra that reveal the resonance structure in neutron induced reaction cross sections. One of the objectives is to produce a high-detection efficient NRCA system capable of mapping element distributions. The detection system is described together with the results of neutron beam tests at the time-of-flight facility GELINA and at the pulsed neutron spallation source ISIS (UK).

Non-destructive bulk analysis of the Buggenum sword by neutron resonance capture analysis and neutron diffraction

Two neutron based techniques, neutron resonance capture analysis (NRCA) and time-of-flight neutron-diffraction (TOF-ND) have been used to determine the elemental composition and structure of a precious and very well preserved all-metal sword from the Bronze Age. This Buggenum sword was on loan from the National Museum of Antiquities (NMA) in Leiden (NL). NRCA and TOF-ND experiments have been carried out at a number of more or less identical positions of the sword. The tin-bronze ratio and the relative amounts of some minor elements (Sb, As, Ag, In) have been determined. The results of neutron diffraction measurements showed considerable tin-segregation, and clear indications of hardening on the edges of the blade. In addition, radiographs using Bremsstrahlung revealed the construction of the hilt–blade connection. The work was carried out at the EC Joint Research Centre IRMM in Geel (B) and at the ISIS facility of the Rutherford Appleton Laboratory (UK).

A simple method for the analysis of neutron resonance capture spectra

Neutron resonance capture analysis (NRCA) is a method used to determine the bulk composition of various kinds of objects and materials. It is based on analyzing direct capture resonance peaks. However, the analysis is complicated by scattering followed by capture effects in the object itself. These effects depend on the object’s shape and size. In this paper the new Delft elemental analysis program (DEAP) is presented which can automatically and quickly analyze multiple NRCA spectra in a practical and simple way, yielding the elemental bulk composition of an object, largely independent of its shape and size. The DEAP method is demonstrated with data obtained with a Roman bronze water tap excavated in Nijmegen (The Netherlands). DEAP will also be used in the framework of the Ancient Charm project as data analysis program for neutron resonance capture imaging (NRCI) experiments. NRCI provides three-dimensional visualization and quantification of the internal structure of archaeological objects by performing scanning measurements with narrowly collimated neutron beams on archaeological objects in computed tomography based experimental setups. The large amounts (hundreds to thousands) of spectra produced during a NRCI experiment can automatically and quickly be analyzed by DEAP.

Photon data shed new light upon the GDR spreading width in heavy nuclei

A global study of the electric dipole strength in and below the isovector giant dipole resonance (GDR) is presented for mass numbers A>80. It relies on the recently established remarkably good match between data for the nuclear photo effect to novel photon scattering data covering the region below the neutron emission threshold as well as by average resonance neutron capture (ARC). From the wide energy coverage of these data the correlation of the GDR spreading width with energy can be studied with remarkable accuracy. A clear sensitivity to details of the nuclear shape, i.e. the β- and γ-deformations, is demonstrated. Based hereon a new parameterization of the energy dependence of the nuclear electric-dipole strength is proposed which — with only two new parameters — allows to describe the dipole strength in all heavy nuclei with A>80. Although it differs significantly from previous parameterizations it holds for spherical, transitional, triaxial and well deformed nuclei. The GDR spreading width depends in a regular way on the respective resonance energy, but it is independent of the photon energy.

Neutron resonance capture and neutron diffraction analysis of Roman bronze water taps

Parts of four Roman bronze water taps, excavated in The Netherlands consisting of two cylinders and two cylinder housings, were non-destructively investigated by neutron resonance capture analysis and by time-of-flight neutron diffraction. The two complementary neutron methods have been, for the first time, combined for providing a comprehensive alloy characterization of intact, undisturbed archaeological bronze objects. Bulk chemical analyses and phase analyses of the copper alloys were carried out in order to establish relations and differences among the taps, and to address questions of standardization and fabrication.

Measurement of Neutron Capture Resonance Integrals on Bromine Isotopes

Neutron capture resonance integrals of the reactions 79Br(n, γ)80Brm, 79Br(n, γ)80Brg, 81Br(n, γ)82Brm, 81Br(n, γ)82Brg, and 81Br(n, γ)82Brm+g have been measured under 1-mm-thick cadmium covers inside the core of the RA-6 research reactor. The measured values are, respectively, (29.2 ± 3.1) b, (86.1 ± 8.9) b, (40.9 ± 2.3) b, (5.1 ± 1.1) b, and (46.8 ± 2.3) b. Resonance integrals of the reactions 79Br(n, γ)80Brm and 81Br(n, γ)82Brm were also measured by a direct method using the gamma ray from the isomeric transition. The results are (30.3 ± 2.6) b and (42.7 ± 4.0) b, respectively. All measured resonance integrals are referred to the standard value (1562 ± 48) b, corresponding to the reaction 197Au(n, γ)198Au. Spectrum unfolding with the STAY’SL code showed the 1/E behavior of the neutron energy spectrum in the epithermal range. Good agreement was found between the results of this work and others published in the literature. Perturbations of epithermal activation due to the presence of cadmium covers are discussed and corrected in the cases where differential cross-section data are available.

Neutron resonance capture analysis and applications

In this paper we discuss the use of neutron resonances to determine the elemental composition of objects non-destructively. Resonances are observed from about 1 to 3000 eV by the time-of-flight technique using the pulsed neutron source of the GELINA facility in Geel (Belgium). Prompt capture γ-radiation is used to signal capture events. Some aspects of the neutron resonance capture analysis (NRCA) are compared with prompt gamma neutron activation analysis (PGNAA).

Neutron resonance capture analysis: Improvements for resonances above 3 keV and new applications

In neutron resonance capture analysis (NRCA), the detection of resonances in the neutron cross section as a function of neutron energy with the time of flight (TOF) technique is used to identify and quantify isotopes. In this paper the improvements of the measuring conditions are discussed in order to reduce the high background, especially in the keV range. The detection efficiency was generally improved, especially for resonances above 3 keV, which allowed the detection of lighter elements, usually having resonances only in the keV region. This broadened the number of applications that could be targeted with NRCA.

Neutron Capture and Total Cross-Section Measurements and Resonance Parameters of Gadolinium

Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic Institute linac facility using metallic and liquid Gd samples. The liquid samples were isotopically enriched in either 155Gd or 157Gd. The capture measurements were made at the 25-m flight station with a multiplicity-type capture detector, and the transmission measurements were performed at 15- and 25-m flight stations with 6Li glass scintillation detectors. The multilevel R-matrix Bayesian code SAMMY was used to extract resonance parameters.Among the significant findings are the following. The neutron width of the largest resonance in Gd, at 0.032 eV in 157Gd, has been measured to be (9 ± 1)% smaller than that given in ENDF/B-VI updated through release 8. The thermal (2200 m/s) capture cross section of 157Gd has been measured to be 11% smaller than that calculated from ENDF. The other major thermal resonance, at 0.025 eV in 155Gd, did not display a significant deviation from the thermal capture cross section given by ENDF.In the epithermal region, the analysis provided here represents the most extensive to date. Twenty-eight new resonances are proposed, and other resonances previously identified in the literature have been revisited. The assignment of resonances within regions of complicated structure incorporated the observations of other researchers, particularly on the six occasions where ENDF resonances are recommended to be removed. The poor match of the ENDF parameters to the current data is significant, and substantial improvement to the understanding of gadolinium cross sections is presented, particularly above 180 eV where the ENDF resolved region for 155Gd ends.

Neutron Capture and Transmission Measurements and Resonance Parameter Analysis of Niobium

Epithermal neutron capture and transmission measurements were performed using the time-of-flight method at the Rensselaer Polytechnic Institute linac using metallic Nb samples. The capture measurements were made at the 25-m flight station with a 16-section sodium iodide multiplicity detector and the transmission measurements at the 25-m flight station with a 6Li glass scintillation detector. Resonance parameters were determined for all resonances up to 500 eV with a combined analysis of capture and transmission data using the multilevel R-matrix Bayesian code SAMMY. The results are compared to those presented in ENDF/B-VI, updated through Release 3.

Neutron Transmission and Capture Measurements and Resonance Parameter Analysis of Neodymium from 1 to 500 eV

Neodymium is a 235U fission product and is important for reactor neutronic calculations. The aim of the present work is to improve upon the existing neutron cross-section data of neodymium.Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic Institute (RPI) linear accelerator (LINAC) laboratory using metallic neodymium samples. The capture measurements were made at the 25-m flight station with a 16-segment NaI multiplicity detector, and the transmission measurements were performed at 15- and 25-m flight stations, respectively, with 6Li glass scintillation detectors. After the data were collected and reduced, resonance parameters were determined by combined fitting of the transmission and capture data with the SAMMY multilevel R-matrix Bayesian code.The resonance parameters for all naturally occurring neodymium isotopes were deduced within the energy range of 1 to 500 eV. The resulting resonance parameters were used to calculate the capture resonance integrals from this energy. The RPI parameters gave a resonance integral value of 32 ± 1 b that is ˜7% lower than that obtained with the ENDF/B-VI parameters. The current measurements significantly reduce the uncertainties of the resonance parameters when compared with previously published parameters.

241Am(n,γ)242gAm反応の熱中性子捕獲断面積及び共鳴積分

241Am(n,γ)242gAm反応の熱中性子捕獲断面積及び共鳴積分

Non-destructive analysis of objects using neutron resonance capture

In this paper we discuss an analytical method, neutron-resonance-capture-analysis (NRCA), which uses the energies of resonances to recognize elements. These resonances are observed by the time-of-flight technique using a pulsed neutron beam at the GELINA facility in Geel (Belgium). The prompt γ-radiation, emitted after a neutron is captured, is used to signal that capture occurred. Areas of resonance peaks are used to evaluate the elemental composition of objects and materials quantitatively. A comparison of NRCA and PGAA is made and elucidated with experimental data resulting from measurements of bronze artefacts at GELINA and at the Budapest Neutron Centre.