Double Differential Neutron Emission Cross Research Articles

Calculations of Double-Differential Neutron and Proton Emission Cross Sections on 19F at 14.2-MeV Incident Neutron Energy

In the present paper, the double-differential cross sections (d2σ/dΩde) of emission spectra for the 19F(n, xn) and 19F(n, xp) structural fusion materials (contained in FLiBe) were calculated by using the Hybrid Monte-Carlo Simulation at 14.2-MeV incident neutron energy in emission angles ranging from 30◦ to 150◦. Theoretical model calculations were carried out by using ALICE-2011, EMPIRE, and TALYS computer codes. Theoretically calculated results of the double-differential cross section for neutron and proton emission are presented and compared with the existing experimental data taken from the international nuclear reaction EXFOR database.

Angle-Dependent Double-Differential Neutron Emission Cross Sections of 3H(t,n) between 5.98 and 19.14 MeV and Evidence of 4H as Intermediate Reaction Product

Neutrons for fusion applications stem not only from monoenergetic sources but also from “white” neutron sources. In this regard, the reaction 3H(t,n) is of particular interest. Continuous neutron spectra of the 3H(t,n) reactions were measured at 5.98-, 7.47-, 10.45-, 16.41-, and 19.14-MeV triton energy at typically seven angles between 0 and 145 deg. The spectra at the three lowest energies contain only neutrons from 3H(t,n)5He and 3H(t,2n)4He reactions and therefore can more easily be interpreted than the spectra at 16.41 and 19.14 MeV, which are too complex to allow a straightforward decomposition except for estimation of the neutron emission cross section following the reaction 3H(t,d)4H. Angle-dependent double-differential and neutron energy—integrated cross sections are given at the five energies. In most cases the peak of the two-body ground state transition could be deconvolved reliably resulting in cross sections of the reaction 3H(t,n)5He. Although the basic scale uncertainty is >5%, severe background, in particular, at the higher triton energies, increases the total uncertainty of integrated cross sections up to 9%. Naturally, the uncertainty of each energy bin of the double-differential cross sections, which depend on bin width, is considerably higher. As no previous data are reported at or near these energies, no direct comparison with other data was feasible. Evidence is provided of the formation of the short-lived neutron-rich nuclei 5He and at higher energies of 4H.

Neutron Emission Spectra of Triton Beams of 20.22-MeV Fully Stopped in Targets of H2O, D2O, LiF, Si, Ni, Mo, Ta, W, Pt, and Au

The Ion Beam Facility of Los Alamos National Laboratory could routinely provide accelerated bunched triton beams to be used in neutron time-of-flight experiments. Exploratory measurements at 0 deg were done to determine the neutron yield with target materials throughout the periodic system yielding absolute specific double-differential neutron yields. Only a few of these measurements were made public previously. The results of these measurements having a mainly demonstrative purpose are presented here because of their uniqueness. For lithium and beryllium, double-differential neutron emission cross sections are given at 17.2 and 15.2 MeV, respectively.

Calculations of Double-Differential Neutron Emission Cross Sections for 9Be Target Nucleus at 14.2 MeV Neutron Energy

In this study, we investigated neutron-emission spectra induced by (n,xn) nuclear reactions for the 9Be structural fusion material at 14.2 MeV neutron energy. We calculated double-differential cross sections (\({\raise0.7ex\hbox{${d^{2} \sigma }$} \!\mathord{\left/ {\vphantom {{d^{2} \sigma } {d\varOmega d\varepsilon }}}\right.\kern-0pt} \!\lower0.7ex\hbox{${d\varOmega d\varepsilon }$}}\)) with ALICE-2011 codeor the angles of 30°, 60°, 90°, 120°, and 150°. Hybrid Monte Carlo simulation model have been used to calculate the double differential emission spectra for these different angles. The obtained results were compared with the measured data taken from EXFOR library. The results show an acceptable agreement.

Theoretical analysis of double-differential neutron emission cross sections for n+56Fe reactions at incident energies of 7–13 MeV

The double-differential neutron emission cross sections for n+56Fe reactions at incident energies of 7–13 MeV at different angles are calculated by the UNF (abbreviation for unified, 2009 Version) code, which is based on the unified Hauser-Feshbach and exciton model. The results indicate that the higher the incident energies, the better the results, although there are some discrepancies between the calculated results and the measured data for natural iron. These discrepancies are analyzed in detail in this paper. In addition, the calculated results are also compared with the evaluated results of ENDF/B VII.0 and JEFF-3.1.1 near the angle of 90° at incident energies of 8.17 and 11.5 MeV, respectively.

Double differential neutron emission cross sections for n + 230,231,232,233,234Th reactions

Consistent calculation and analysis of neutron-induced reaction cross sections of 232Th with optical model, the unified Hauser–Feshbach and exciton model, the linear angular momentum dependent exciton density model, the coupled channel theory and the distorted wave Born approximation is carried out in the E n ⩽ 20 MeV energy range based on the experimental data of total, nonelastic, fission, and other reaction cross section and elastic scattering angular distributions. Especially, the analysis includes the elastic and inelastic scattering angular distribution, the inelastic scattering cross sections of discrete levels, the prompt fission neutron spectra, the double differential cross section and the angle-integrated spectra for neutron emission. Theoretical calculations are compared with recent experimental data, other theoretical calculations and evaluated data from ENDF/B6 and JENDL-3. Theoretical models predict the results for n + 230,231,233,234Th reactions.

Experimental Study on Cross Section Data of Mercury with D-T and 252Cf Neutron Sources

Mercury is a promising candidate material for spallation neutron targets driven by high intensity proton accelerators. Validity of cross section data of mercury up to 20 MeV evaluated for JENDL-3.3 was investigated experimentally by means of both differential and integral approaches. Double differential neutron emission cross section (DDX) for incident neutron energy at 15 MeV was measured. Integral experiment for testing neutron transport and secondary gamma-ray production was conducted by using D-T and 252Cf neutron sources. As a result, general agreement between quantities derived from JENDL and the experimental results was confirmed. Some problems were still pointed out in the DDX data, cross section data in an incident neutron energy range approximately from 0.3 to 3 MeV and secondary gamma-ray production cross section.

Measurement of the 28Si(n,p), 29Si(n,p) and 30Si(n,α) Cross Sections between 6.9 and 14.0 MeV

Neutron activation cross sections of 28Si(n, p)28Al, 29Si(n, p)29Al and 30Si(n, α)27Mg were measured in the energy region from 7 to 14 MeV. The measurements were performed with a D(d, n)3He neutron source and were carefully corected for disturbing neutrons from the D(d, np) breakup reaction. The corrections are based on a detailed measurement of the double-differential neutron emission cross sections of the neutron source reaction. The present work is the only experiment which covers the neutron energy range from 7 to 13 MeV of the 29Si(n, p)29Al and 30Si(n, α)27Mg reaction, and that from 9 to 12.5 MeV of the 28Si(n, p)28Al reaction.

Measurements of Double-Differential Neutron Emission Cross Sections of 6Li, 7Li and 9Be for 11.5 MeV and 18.0 MeV Neutrons

Double-differential neutron emission cross sections (DDXs) of 6Li, 7Li and 9Be were measured for 18.0 MeV and 11.5 MeV incident neutrons produced by the T(d, n) and 15N(d, n) reactions respectively, using the Tohoku University Dynamitron time-of-flight (TOF) spectrometer. The data were obtained at 13 laboratory angles, and angular-differential cross sections (ADXs) of elastic and inelastic scattering neutrons were derived from the DDXs. For 11.5 MeV neutrons, we obtained the neutron emission spectra over the secondary neutron energies by newly employing the double TOF method as well as the conventional one. In the measurements at 18.0 MeV, we achieved better energy resolution than in our previous studies by using a neutron detector that has a larger solid angle and a thinner tritium target. The experimental results of DDXs and ADXs were compared with our previous results and the evaluated data given in JENDL-3.2, JENDL Fusion File and ENDF/B-VI. It is found that the JENDL data reproduce the experimental ones very well.

Measurements of Double-Differential Neutron Emission Cross Sections of 6Li, 7Li and 9Be for 11.5 MeV and 18.0 MeV Neutrons.

Measurements of Double-Differential Neutron Emission Cross Sections of 6Li, 7Li and 9Be for 11.5 MeV and 18.0 MeV Neutrons.

Double-differential neutron emission cross sections of 14-MeV neutron induced reactions on Na and Pb

The energy and angular distribution of secondary neutrons from the interaction of 14-MeV neutrons with sodium and natural lead were investigated. Absolute double-differential neutron emission cross sections were measured for reaction angles from 30\ifmmode^\circ\else\textdegree\fi{} to 150\ifmmode^\circ\else\textdegree\fi{} in steps of 15\ifmmode^\circ\else\textdegree\fi{} in the secondary neutron energy range 2--14 MeV using the time-of-flight facility at the Institut f\"ur Radiumforschung und Kernphysik, Vienna. Systematic uncertainties in these measurements could be reduced to less than 3--5% (depending on secondary neutron energy) resulting in total uncertainties of less than 5% for a large part of the studied range in angle and energy for Pb and of less than 8% for Na. These results agree with previous measurements within the relatively large uncertainties of the latter. The measured cross sections were compared to the results of statistical model calculations using the quantum mechanical theory of Feshbach, Kerman, and Koonin for preequilibrium emission and also with calculations based on the exciton model and the Kalbach-Mann systematics for the shape of the angular distributions. For compound nucleus decay, the Hauser-Feshbach model was used in both cases. Very good agreement was found with both predictions in the case of lead; in the case of sodium, noticeable discrepancies do show the limits of applicability of any statistical model for light nuclei.

Gradual absorption of fast neutrons in niobium

Single- and double-differential neutron-emission cross sections for niobium, at bombarding neutron energies of 7, 14, 20 and 26 MeV, have been adequately explained in terms of direct reactions accompanied by gradual absorption into successive compound states of increasing complexity which develop towards the compound nucleus.

Measurements of Double-Differential Neutron Emission Cross Sections of Nb, Mo, Ta, W and Bi for 14 and 18 MeV Neutrons

Measurements of Double-Differential Neutron Emission Cross Sections of Nb, Mo, Ta, W and Bi for 14 and 18 MeV Neutrons

A compact post-acceleration beam chopper for a 4.5 MV Dynamitron pulsed neutron generator

A post-acceleration beam chopper (PACS) has been installed for a 4.5 MV Dynamitron accelerator to improve the energy resolution of neutron time-of-flight (TOF) experiments by shortening the duration of the ion beam pulses. The PACS sweeps the accelerated ion pulses across a chopping slit and eliminates the tails of the beam pulses. It operates sinusoidally at a frequency of 8 MHz with a maximum voltage of 10 kV peak to peak in synchronization with the accelerated ion pulses. The high voltage generator of the PACS was constructed of commercially available amplifiers and components, which realized easy maintenance and low cost. The PACS proved to be very effective to improve the pulse shape and has been applied for double-differential neutron emission cross section measurements.

Measurements of Double-Differential Neutron Emission Cross Sections of Nb, Mo, Ta, W and Bi for 14 and 18 MeV Neutrons.

Double-differential neutron emission cross sections have been measured for Nb, Mo, Ta, W and Bi at 14 MeV incident energy, and for Nb and Bi at 18 MeV using Tohoku University Dynamitron TOF spectrometer. The experimental results indicated problems in current evaluations both for energy spectra and angular distributions. Angle-integrated neutron emission spectra and angular distributions of secondary neutrons were analyzed, respectively, by the statistical multi-step model code EXIFON and the systematics by Kalbach-Mann and by Kalbach. The energy spectra were reproduced successfully by EXIFON except for Bi, and the angular distributions were followed by the systematics over wide range of outgoing energy and target mass if the emission spectra calculated by EXIFON were employed for generation of angular distributions.

Measurement of double differential neutron emission cross sections of Fe induced by 14.1 MeV neutrons

We measured the energy spectra and yields of neutrons above 2 MeV emitted from collisions of 14.1 MeV neutrons with an iron target. The measurements we

Neutron emission cross sections on 93Nb and 209Bi at 20 MeV incident energy

Double-differential neutron emission cross sections at 20 MeV incident energy have been studied for monoisotopic samples of 93Nb and 209Bi. Time-of-flight spectra were taken at several angles between 15° and 153° using a beam-swinger spectrometer. The data are averaged over 0.5 MeV energy bins and compared with quantum-mechanical, statistical multistep calculations.

Requirements and status of fast neutron cross sections for nuclear fusion

This paper discusses some of the requirements of fast neutron cross sections for the development of tokamak fusion reactor technology and their current status. While considerable progress has been achieved in knowledge of fast neutron scattering and reaction cross sections of fusion reactor materials, much work needs still to be done particularly on double-differential neutron emission and neutron activation cross sections, in particular (n,α) cross sections. Particular consideration has been given to the work of Professor Csikai and co-workers who have rendered essential contributions to the measurement and analysis of 14 MeV neutron cross sections of importance to fusion.

Modelling double differential neutron emission cross sections for 7LI

Sequential modelling, phase space and two-body scattering models are used to produce a unified model for the double differential neutron cross sections for neutron emission in 7Li for the range of incident neutron energies 5–18 MeV. While satisfactory agreement is obtained with a range of measurements of both double differential and angular distributions, some anomalies are revealed in the competing roles of three-body breakup and sequential reactions in the (n,2n) channel, particularly at the higher incident energies.

Measurement of double-differential neutron emission spectra from uranium-238.

We have performed the measurement of neutron emission spectra from 238U using a time-of-flight technique, and deduced the following data; (1) the prompt fission neutron spectra for 2 MeV incident neutrons at two emission angles of 90° and 135°, (2) the double-differential neutron emission cross sections at the incident energies of 1.2, 2.0, 4.2, 6.1 and 14.1 MeV. The emission spectra and the cross sections for scattering process were also deduced by subtracting the fission neutrons from the experimental spectra. The experimental results were compared with other experiments and the evaluations of JENDL-3 and ENDF/B-IV. From the fission spectrum data ranging from 2 to 12 MeV, we have derived the best fit parameters for the Maxwellian and Watt type distribution functions. The experimental spectra are described with the Maxwellian spectrum with temperature of 1.24–1.26 MeV and are softer than both evaluations. The spectra and cross sections for inelastic-scattering showed substantial disagreement with the eva...