Interaction Of 14-MeV Neutrons Research Articles

Charge Losses through Recombination while Detecting Fast Neutrons with Gas Proportional Counters

A procedure of calculating the ionization defect in a methane proportional counter is described for the case of heavy charged particles (p, α, 9Ве, and 12C), which are products of the interaction of 14-MeV neutrons with hydrogen and carbon nuclei. A radial structure of a charged-particle track and its decay through diffusion and recombination processes in an electric field are modeled. Certain effects neglected earlier are taken into consideration. Comparing the calculated and counter-measured experimental amplitude distributions has shown that the theory developed for calculating the ionization defect yields qualitatively correct results. Analyzing the compared results has also shown that some important notions concerning the initial data on the differential cross sections of gas ionization by particles with charges Z > 1, electron temperature in the track plasma, and model concepts on the electron escape from the track need refinement.

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.

Study of Gamma Radiation from Interaction of 14.7-MeV Neutrons with208Pb

The gamma radiation from the interaction of 14.7-MeV neutrons with {sup 208}Pb is investigated by high-resolution germanium-detector gamma-ray spectroscopy by using an enriched {sup 208}Pb sample. Cross sections for 14 gamma-ray lines from the {sup 208}Pb(n,n{prime}{gamma}) and {sup 208}Pb(n,2n{gamma}) reactions are measured at an emission angle of 124 deg. The results are compared with measurements from previous studies and with predictions based on the statistical theory of nuclear reactions (including direct and precompound contributions). The current results, especially for the {sup 208}Pb(n,n{prime}{gamma}) reaction, are considerably smaller than the results of most of the measurements of the previous studies probably because of the neglect of important sources of background, e.g., gamma-ray production in lead shielding, in the previous studies. Agreement with theory is adequate for the strong transitions between the lowest levels in {sup 207}Pb and {sup 208}Pb, but large discrepancies exist for the weaker transitions, especially for gamma-ray transitions from levels where experimental knowledge of branching ratios is missing. The study of the gamma radiation from the interaction of 14-MeV neutrons with lead is essential for accurate prediction of the gamma-ray heating in such devices. In addition, the nucleus {sup 208}Pb is especially studied as a test case for detailedmore » comparison of the predictions of nuclear reaction theory with experiments.« less

Group and total cross sections of formation of ?-ray quanta upon the interaction of 14-MeV neutrons with various nuclei

Group and total cross sections of formation of ?-ray quanta upon the interaction of 14-MeV neutrons with various nuclei

Measurements and Calculations of the Electron Recoil Spectra from Gamma Rays Emitted by Nitrogen for a 14-MeV Neutron Source

The electron recoil spectra from gamma rays produced by the interaction of 14-MeV neutrons with 0.5, 1.0, 3.0, and 7.0 mean-free-paths (mfps) of nitrogen have been measured with NE-213 scintillator...

Measurements of the Neutron Spectra from Materials Used in Fusion Reactors and Calculations Using the ENDF/B-III and -IV Neutron Libraries

Proposed fusion reactor blanket designs bring into focus a large number of problems dealing with the interaction of 14-MeV neutrons with different materials. Carbon, oxygen, aluminum, titanium, and iron are among the materials used in the blanket. To have confidence in fusion reactor blanket calculations, a necessary prerequisite is that the transport code correctly describes the interaction of 14-MeV neutrons with the materials of the blanket. Spherical assemblies of the above materials ranging from 1 to 5 mean-free-paths in thickness have been bombarded with a centered nominal 14-MeV neutron source. The emitted neutron energy spectra were measured using time-of-flight techniques (3-nsec full-width-at-half-maximum system resolution) in a geometry where the flight path (7 to 10 m) is long compared to the dimensions of the spherical targets. The spectra have been calculated with the Monte Carlo neutron transport code TART using the ENDF/B-III and -IV neutron libraries and compared with measurements.

Gamma-Ray Spectra from the Interaction of 14-MeV Neutrons with Copper, Zirconium, and Antimony

High energy gamma-ray spectra from the radiative capture of 14-MeV neutrons in copper, zirconium, and antimony have been measured with a coincidence-anticoincidence telescope pair spectrometer. These spectra are compared with predictions from calculations using the semidirect (collective) capture model. The parameter values used were derived from other types of experiments and from nuclear models. Agreement is found both in shape and in magnitude without further adjustment of parameters. Partial radiative capture cross sections, obtained by integrating the gamma-ray spectra for gamma energies in excess of 14 MeV, are compared with values from other measurements.

Gamma rays from the interaction of 14-MeV neutrons with lithium

The cross section for the LP(n, n′)Li7∗ → Li7 + γ(0.477 MeV) reaction has been measured near 14 MeV by detecting the gamma rays. A time-of-flight technique was used to distinguish the gamma rays from the high neutron background. The cross section is about 80 mb (± 12%) in the neutron energy range 13.6–14.3 MeV. Beyond this the data suggest a rise in the cross section is 110 mb at 14.7 MeV.

Gamma rays from the interaction of 14-MeV neutrons with carbon

The cross section for the C 12(n, n′)C 12 λ →C 12+ γ (4.43 MeV) reaction has been measured near 14 MeV by detecting the gamma rays at scattering angles of 30° to 150°. A time-of-flight technique was used to distinguish the gamma rays from the high neutron background. A least-squares fit to the data gives σ( θ) = (13.3 ± 0.6) + (40.0 ± 4.7) cos 2 θ−(34.1 ± 5.1) cos 4 θ for the angular distribution. The integrated cross section is σ n, n′ γ = 249 ± 28 mb.

Gamma rays from the interaction of 14-MeV neutrons with beryllium

The cross section for the Be 9( n, t′) Li 7∗ → Li 7 + γ (0.477 MeV) reaction has been measured in the vicinity of 14 MeV by detecting the gamma-rays at scattering angles from 30° to 150°. A time-of-flight technique was used to distinguish the gamma-rays from the high neutron background. The cross section drops from 20 mb at 13.6 MeV to 10 mb at 14.1 MeV and then rises to 30 mb at 14.7 MeV.

Neutron Emission Probabilities from the Interaction of 14-Mev Neutrons with Be, Ta, and Bi

The spatial and spectral distributions of the neutrons from 14-Mev neutron interactions with Ta and Bi have been obtained by using nuclear emulsion detectors in conjunction with a neutron collimator. These results indicate that roughly 85 to 90% of the interactions proceed via compound-nucleus formation while approximately 10 to 15% proceed by direct interactions. The space-integrated neutron spectrum has been obtained for Be by means of a sphere experiment. Cross sections for neutron emission, nonelastic scattering, ($n, {n}^{\ensuremath{'}}$), and ($n, 2n$) are derived for all three elements.

Inelastic interaction of 14-Mev neutrons with nuclei

Inelastic interaction of 14-Mev neutrons with nuclei

Charged Particles from the Interaction of 14-Mev Neutrons withLi6andLi7

The angular distribution of the charged particles produced in the bombardment of ${\mathrm{Li}}^{6}$ and ${\mathrm{Li}}^{7}$ by 14-Mev neutrons was observed with nuclear emulsions in a multiplate camera. Metallic targets of enriched ${\mathrm{Li}}^{6}$ and ${\mathrm{Li}}^{7}$ were used. The following cross sections were measured: ${\mathrm{Li}}^{6}(n, p){\mathrm{He}}^{6}$, 6\ifmmode\pm\else\textpm\fi{}2 mb; ${\mathrm{Li}}^{6}(n, d){\mathrm{He}}^{5}$, 89\ifmmode\pm\else\textpm\fi{}10 mb; ${\mathrm{Li}}^{6}(n, d){\mathrm{He}}^{5*}$, 77\ifmmode\pm\else\textpm\fi{}9 mb; ${\mathrm{Li}}^{6}(n, t){\mathrm{He}}^{4}$, 26\ifmmode\pm\else\textpm\fi{}4 mb; ${\mathrm{Li}}^{7}(n, t){\mathrm{He}}^{5}$, 55\ifmmode\pm\else\textpm\fi{}8 mb. The reaction ${\mathrm{Li}}^{7}(n, d){\mathrm{He}}^{6}$ was also observed but was not well enough resolved to give an angular distribution and total cross section. No evidence was found for the formation of ${\mathrm{He}}^{7}$ by ${\mathrm{Li}}^{7}(n, p){\mathrm{He}}^{7}$ with a cross section greater than 5 mb in the range $\ensuremath{-}1.0>Q>\ensuremath{-}7.0$ Mev. The angular distributions obtained for ${\mathrm{Li}}^{6}(n, d){\mathrm{He}}^{5}$ and ${\mathrm{Li}}^{6}(n, d){\mathrm{He}}^{5*}$ indicate these reactions proceed mainly by an inverse stripping or pick-up process. The energy spectrum of the neutrons from ${\mathrm{Li}}^{6}(n, d){\mathrm{He}}^{5}(n){\mathrm{He}}^{4}$ and ${\mathrm{Li}}^{6}(n, d){\mathrm{He}}^{5*}(n){\mathrm{He}}^{4}$ is calculated using several assumptions for the angular distribution of the ${\mathrm{He}}^{5}$ disintegration.

Gamma Rays from Interaction of 14-Mev Neutrons with Various Materials

Experiments have been performed to observe the pulse-height distribution produced in a single crystal spectrometer by gamma radiation arising from bombardment of various materials with 14-Mev neutrons. Various gamma-ray lines have been identified and estimates made of the total cross section for gamma-ray production.

The Interaction of 14-Mev Neutrons with Protons and Deuterons

Nuclear emulsions in conjunction with a neutron collimator have been used to measure the differential cross section as a function of angle for the elastic scattering of monoenergetic 14-Mev neutrons by protons and by deuterons. Measurements were carried out in the angular regions corresponding to neutrons being scattered at angles between 48\ifmmode^\circ\else\textdegree\fi{} and 154.5\ifmmode^\circ\else\textdegree\fi{} in the center-of-mass system by protons and between 46\ifmmode^\circ\else\textdegree\fi{} and 176\ifmmode^\circ\else\textdegree\fi{} in the same coordinate system by deuterons. The $n\ensuremath{-}p$ scattering data are consistent with isotropic scattering in the center-of-mass system, and are in excellent agreement with the data of Barschall and Taschek. The $n\ensuremath{-}d$ elastic scattering data are strongly anisotropic. The shape of the angular distribution of the neutrons elastically scattered by deuterons may be inferred from the differential cross sections in millibarns for the following laboratory angles: 2\ifmmode^\circ\else\textdegree\fi{}, 435\ifmmode\pm\else\textpm\fi{}28; 10\ifmmode^\circ\else\textdegree\fi{}, 342\ifmmode\pm\else\textpm\fi{}27; 20\ifmmode^\circ\else\textdegree\fi{}, 78\ifmmode\pm\else\textpm\fi{}9.3; 30\ifmmode^\circ\else\textdegree\fi{}, 38\ifmmode\pm\else\textpm\fi{}4.2; 40\ifmmode^\circ\else\textdegree\fi{}, 59\ifmmode\pm\else\textpm\fi{}5.2; 50\ifmmode^\circ\else\textdegree\fi{}, 104\ifmmode\pm\else\textpm\fi{}9.0; 60\ifmmode^\circ\else\textdegree\fi{}, 136\ifmmode\pm\else\textpm\fi{}12; 65\ifmmode^\circ\else\textdegree\fi{}, 142\ifmmode\pm\else\textpm\fi{}14. Strong evidence for the reaction $D(n, 2n){H}^{1}$ has been found and an attempt to determine the energy and angular distribution of the disintegration protons was moderately successful.

Gamma-Radiation from Interaction of 14-Mev Neutrons with Iron

Experiments have been performed to observe gamma-rays produced by the interaction of 14-Mev neutrons with iron. Although the gamma-spectrum appears to be continuous below 3.0 Mev, there may be discrete gamma-rays at 3.3, 4.4, 5.8, 7.1, and 8.75 Mev. The total cross section for gamma-ray production is 4.6\ifmmode\pm\else\textpm\fi{}0.5 barns.

Distribution in Energy of the Neutrons from the Interaction of 14-Mev Neutrons with Some Elements

The neutron spectra from the interaction of 14-Mev neutrons with a number of elements have been determined by nuclear plate techniques. The plates were exposed to neutrons from the bombardment of a Zr-T target by 200-kev deuterons when the target was as nearly as possible isolated from all scattering material and when the target was surrounded by a spherical shell of the element to be investigated. The variation of $F({E}_{n})$, the number of emitted neutrons per unit energy interval with energy (${E}_{n}$), appears to be Maxwellian in the region 0.5 to 4.0 Mev and may be represented by $F({E}_{n})d{E}_{n}=C{E}_{n}{e}^{\ensuremath{-}\frac{{E}_{n}}{T}}d{E}_{n}.$

Interaction of 14-Mev Neutrons with Deuterons

By coincidence counting of recoil deuterons in a proportional counter telescope the angular distribution for $n\ensuremath{-}d$ scattering has been measured using monoergic neutrons of 14-Mev energy. The measurements covered the angular range corresponding to neutrons being scattered at angles between 180\ifmmode^\circ\else\textdegree\fi{} and 70\ifmmode^\circ\else\textdegree\fi{} in the center of mass system, and by extrapolation an approximate curve was obtained over all angles. Upper limits can be placed on the probability of the $n\ensuremath{-}2n$ disintegration process for ejection of protons in the angular range from 0\ifmmode^\circ\else\textdegree\fi{} to 120\ifmmode^\circ\else\textdegree\fi{} in the center of mass system.