Neutron Inelastic Cross Sections Research Articles

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.

Cross section for inelastic neutron scattering from 193Ir at 6 MeV

Two samples, one of natural iridium and the other of enriched 193Ir, were irradiated with a monoenergetic neutron beam of energy 6.0 MeV at the Triangle Universities Nuclear Laboratory. The product of the 193Ir(n,n′)193mIr reaction was determined by means of measuring X-rays following electron conversion of the isomeric state at 80.2 keV in 193Ir. The cross section for inelastic neutron scattering is reported disagreeing with the literature data.

Simulating Static and Dynamic Properties of Magnetic Molecules with Prototype Quantum Computers

Magnetic molecules are prototypical systems to investigate peculiar quantum mechanical phenomena. As such, simulating their static and dynamical behavior is intrinsically difficult for a classical computer, due to the exponential increase of required resources with the system size. Quantum computers solve this issue by providing an inherently quantum platform, suited to describe these magnetic systems. Here, we show that both the ground state properties and the spin dynamics of magnetic molecules can be simulated on prototype quantum computers, based on superconducting qubits. In particular, we study small-size anti-ferromagnetic spin chains and rings, which are ideal test-beds for these pioneering devices. We use the variational quantum eigensolver algorithm to determine the ground state wave-function with targeted ansatzes fulfilling the spin symmetries of the investigated models. The coherent spin dynamics are simulated by computing dynamical correlation functions, an essential ingredient to extract many experimentally accessible properties, such as the inelastic neutron cross-section.

Describing the Spin Dependence of p-Wave Neutron Scattering on Spherical Nuclei in a Two-Phonon Approximation of the Coupled Channel Technique

The spin dependence of p-wave neutron scattering by spherical nuclei in region A ≈ 60–130 is analyzed. The spin-orbit splitting of the 3p-maximum of the neutron force function is described using a two-phonon approximation of the coupled channel thechnique. The cross section of inelastic neutron scattering through a composite nucleus is comparable to that of the direct excitation of collective states at an energy of ∼1 MeV.

Nucleon inelastic scattering cross sections on O16 and Si28

This paper reports cross-section measurements of the ($n,{n}^{\ensuremath{'}}$) and ($p,{p}^{\ensuremath{'}}$) reactions on $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$ at Geel Electron Linear Accelerator and at the 9-MV Tandem Accelerator of Horia Hulubei National Institute for Physics and Nuclear Engineering, respectively. The main purpose was to measure the neutron- and proton-induced inelastic $\ensuremath{\gamma}$-production cross sections for all observed transitions in $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$, followed by the calculation of the corresponding total inelastic cross section. The results are compared with theoretical calculations performed using the talys 1.9 code, evaluated nuclear data, and previously reported experimental data. The broader goal of this work is to study whether and to what extent the neutron-induced inelastic cross sections of these nuclei can be inferred from those obtained using suitable charged particle reactions. We show that, by making use of the formal similarities between the neutron- and the proton-target optical model potentials and isospin symmetry in mirror nuclei, one can develop a procedure that combines experimental proton-induced inelastic cross sections with theoretical calculations to infer neutron inelastic cross sections. For $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$, the precision associated with this procedure is around 10--20% for most of the incident energy range.

GAINS: neutron inelastic cross section measurements of interest for applications and reaction studies

The paper represents an overview of the measurements performed using GAINS at GELINA (JRC-Geel, Belgium). While undergoing continuous upgrades, the setup produced highly precise cross sections. Our measurements are primarily driven by technological needs with an emphasis on structural materials used in the development of nuclear facilities. However, most cases offered the opportunity to investigate various reaction mechanism and/or nuclear structure issues. We concentrate on several specific experiments describing the particular difficulties we met and the solutions we adopted to infer reliable data and to draw significant conclusions.

Neutron inelastic cross section measurements on 58,60Ni

A natural nickel sample was used at the GELINA (Geel Electron LINear Accelerator) neutron source of the European Commission, Joint Research Centre, Geel to measure the neutron inelastic cross sections. The GAINS (Gamma Array for Inelastic Neutron Scattering) spectrometer was employed to detect the emitted γ rays while a 235U fission chamber monitored the neutron flux. We report the preliminary production cross sections corresponding to the first transitions in 58,60Ni in comparison with previously reported data and with TALYS 1.9 calculations performed using the default input parameters.

Inelastic scattering of fast neutrons on 6Li and 7Li nuclei in three-body cluster model

The systematic approach to calculating cross section of inelastic neutron scattering on 6Li and 7Li nuclei in the range of kinetic energies En=0.1−20 MeV is presented. The reaction mechanism is described using the Faddeev equations within the problem of neutron interaction with two clusters which form the target nucleus bound state. The length anLi of elastic n−Li scattering are calculated. The coherence effect on n5Li and αd contributions to 6Li nucleus ground state is demonstrated by the example of elastic neutron scattering reaction. Total and differential cross sections of inelastic neutron scattering on 6Li and 7Li nuclei with formation of three and four particles in the final state are calculated. Three-body interaction of clusters which form the target nucleus ground state in 6Li(n,n′)dα and 7Li(n,n′α)t reactions is shown to be of great importance.

Neutron inelastic scattering of 232Th: measurements and beyond

Gamma production cross sections have been obtained for 81 transitions in 232Th from (n,n’γ), 11 in 231Th from (n,2nγ) and 7 in 230Th from (n,3nγ) reactions using prompt gamma spectroscopy. Incident neutron energies were determined using the neutron time-of-flight technique. Sources of uncertainty have been examined and their correlations have been computed. Total uncertainty on cross sections ranges from 4 to 20%. Obtained cross sections are in agreement with prior experiments, but are not well reproduced by the TALYS 1.8 reaction code using default parameters. During analysis, discrepancies between our findings and the Evaluated Nuclear Structure Data File (ENSDF) were noted. Future work related to the present experiment includes: improving theoretical models, quantifying the influence of the 232Th inelastic neutron cross section on reactor core parameters, and conducting additional measurements.

Integral cross section measurement of theU235(n,n′)U235mreaction in a pulsed reactor

The integral measurement of the neutron inelastic cross section leading to the 26-minute half-life $^{235m}\mathrm{U}$ isomer in a fission-like neutron spectrum is presented. The experiment has been performed at a pulsed reactor, where the internal conversion decay of the isomer was measured using a dedicated electron detector after activation. The sample preparation, efficiency measurement, irradiation, radiochemistry purification, and isomer decay measurement will be presented. We determined the integral cross section for the $^{235}\mathrm{U}(n,{n}^{\ensuremath{'}})^{235m}\mathrm{U}$ reaction to be $1.00\ifmmode\pm\else\textpm\fi{}0.13\phantom{\rule{0.28em}{0ex}}\mathrm{b}$. This result supports an evaluation performed with talys-1.4 code with respect to the isomer excitation as well as the total neutron inelastic scattering cross section.

γ-ray production cross sections of inelastic neutron scattering on natural molybdenum

γ-ray production cross sections of inelastic neutron scattering have been measured for molybdenum using the (n,n’γ)-technique. The experiment was performed at the GELINA facility at the Institute for Reference Materials and Measurements (IRMM) with the Gamma Array for Inelastic Neutron Scattering (GAINS) setup. GAINS consisted of eight high purity germanium detectors at the time of this experiment. The sample was made of natural molybdenum, which includes seven isotopes (A = 92, 94, 95, 96, 97, 98, 100). The presence of so many isotopes in the sample leads to overlapping peaks in the spectra, which limits the amount of data that can be extracted from the analysis. Nevertheless, a total of 31 γ rays from the seven isotopes were analysed and γ-ray production cross sections were determined. Comparisons to other experimental results were made when such data was available. Also comparisons with model calculations were made with the Talys 1.6 code.

From resonances to fluctuations: A microscopic analysis of the cross-section for inelastic neutron scattering to a definite state

Thomas' approximation to the general R-matrix theory of Wigner and Eisenbud is used to study the development of fluctuations in the cross-section for inelastic neutron scattering, to a definite state, in the transition from the resonance region to the continuum. In standard analyses of Ericson fluctuations, averaging of all resonance parameters is carried out from the beginning. Here, no averaging is performed; it is therefore possible to study, in detail, the effects of variations in both the random distributions of the phases of interfering amplitudes associated with elastic and inelastic scattering and the statistical distributions of parameters of the underlying resonances. The present microscopic model is not limited to the study of nuclear reactions; studies of inelastic scattering associated with quantum dots in semiconductors at low temperature and electron–atom interactions that involve many overlapping resonances, require analyses of the kind reported.

Neutron Inelastic Cross Section Measurements for Sodium

Inelastic scattering cross sections for sodium are of interest to the development of sodium cooled fast reactors. A recent OECD-NEA subgroup analysed the sensitivity of reactor parameters to cross sections and accordingly determined target uncertainties for the nuclear data. Comparing these target uncertainties with the current status of nuclear data uncertainties and covariance data resulted in a list of target priorities. Among these features sodium inelastic scattering for which a target uncertainty of about 5% was established, approximately two to three times as good as the uncertainty for current evaluated data files for this isotope (see OECD-NEA High Priority Request List, http://www.nea.fr/html/dbdata/hprl/hprlview.pl?ID=448). At IRMM, the GAINS gammaarray for inelastic neutron scattering was developed with the purpose of measuring cross sections with uncertainties at or below the target uncertainties for nuclides like Na using the (n, n′γ)technique. Measurements were performed at the GELINA facility at a 200 m flight path with eight high purity germanium detectors. The sample was an 80 mm diameter metallic disk prepared at IRMM by cutting, pressing, rolling and punching. For the experimental work, a careful review was made of the gamma-efficiency calibrations and the flux normalization in order to investigate in detail the corrections and the final uncertainties that may realistically be achieved. An elaborate account will be presented of the data analysis and checks that have been made and implications for earlier work by our group will be discussed. First results will be shown for the gamma-production cross sections of the main transitions in the energy range from threshold to 10 MeV.

Nuclear data evaluation of 55Mn by the EMPIRE code with emphasis on the capture cross-section

Manganese is one of the constituents of alloys for structural components of fission and fusion devices and a well-known neutron dosimeter; however, existing ENDF-B/VII.0 55Mn evaluation was produced by Shibata (1989). This work is an attempt to re-evaluate neutron-induced cross-sections of 55Mn using the latest release of the EMPIRE code. Sensitivity studies on the physical and fitting parameters are presented, with special emphasis on the capture and neutron inelastic cross-sections. A calculated nuclear data file in ENDF-6 format of the neutron interaction cross-sections is produced. It extends up to 150 MeV, which is of interest for fusion and accelerator driven system applications. This evaluation is compared with the ENDF/B-VII.0 evaluation and with a selection of experimental microscopic cross-sections. The evaluation is tested using integral data: the OKTAVIAN integral experiment on a manganese shell and an FNG experiment with manganese activation foils. Benchmark results provide needed feedback for the refinement of the physics parameters.

Inelastic neutron scattering cross section in ferromagnetic nanowires

This article presents the first theoretical study of the inelastic neutron cross section in arrays of cylindrical ferromagnetic nanowires. The recently developed dipolar-exchange theory of spin-wave excitations in such wires is used. Results are represented for the few lowest bulk quantized spin-wave modes of different forms.

Dipolar-exchange theory of quantized spin-wave modes: Calculations of inelastic neutron scattering cross section in arrays of ferromagnetic nanowires

A recently developed dipolar-exchange theory of quantized spin-wave (SW) modes in cylindrical ferromagnetic nanowires is used here for the calculation of the inelastic neutron cross section in different ordered lattices of such wires. The Hamiltonian formalism for bulk spin-wave excitations in nanowires is developed under the following simplifications: (1) wires in the array do not interact with each other; (2) an applied magnetic field is equal to zero. The calculated cross section is analyzed as a function of different shapes of SW modes, SW frequencies, quantized radial wave vector components, and the momentum transfer along the wire.

Measurements and analysis of carbon and oxygen neutron inelastic cross sections below 10 MeV

Inconsistencies and errors have been found in standard neutron cross-section libraries. In particular, cross-sections for the production of gamma-rays induced by the interactions of fast neutrons with carbon and oxygen have been found to be in error. Accurate values for these particular cross-sections are important for the simulation and design of non-intrusive inspection systems based on nuclear techniques. To support the simulations, several experimental measurements have been performed and analyzed. These include both relative measurements of angular distributions and absolute measurements of differential cross sections. Simple analysis has been performed for all of the data collected, and detailed analysis has been performed for data collected at a neutron energy of 8.51 MeV. A description of the experimental setup, the analysis of the data, and the results are presented.

Vibrational properties of the modulated spring chain: neutron cross section and dual spectrum

The inelastic neutron cross section is calculated for a modulated spring chain, which models an incommensurate composite system. The authors obtain a difference equation for the neutron cross section which has an exact and analytic solution for a periodic modulation. The structure of the neutron spectrum is studied as functions of wavevector and energy transfers for a wide range of model parameters. In general the spectra consist of bands of intensity, except at special wavevectors where bands collapse to a singular structure characteristic of normal modes of vibration.

Inelastic neutron scattering by quasi-local vibrations interacting with sound waves in glasses

By taking into account both long-wave acoustic phonons and strongly anharmonic low-frequency quasi-local vibrations (QLV), the general double-differential cross section for inelastic neutron scattering in glasses is derived. In the framework of the appropriate pseudo-spin model of a glass, QLV scattering intensities of both the resonant and relaxation types are evaluated. It is shown that, in the range of low frequencies (2-3 meV), the resonant-like density of QLV states is comparable with the density of phonon states as well as corresponding rather closely to the neutron-measured dominant low-frequency ('additional') density of vibrational states in glasses.

Neutron scattering from tunneling protons in metals

We consider a two-level system in metals, in which a proton is tunneling between two neighboring sites. Cross section of inelastic neutron scattering from this system is calculated. The interaction with the metallic electrons reduces the level separation and causes a level broadening. The ratio of the former to the latter turns out to increase as a negative power of the temperature as the temperature decreases. Thus, the proton may make a coherent motion at very low temperatures. The cross-over temperature where this ratio goes through unity is shown to be of the order of the level separation at T = 0. This result explains a recent neutron experiment on the proton in niobium with a small amount of oxygen.