Neutron total,scattering and inelastic Gamma-ray cross sections of yttrium at few MeV energies

Neutron total, scattering and (n; n′,γ) cross sections of elemental yttrium (⁸⁹Y) were measured in the few-MeV region. The neutron total-cross-section measurements were made with broad resolutions from ≈0.5 to 4.2MeV in steps of ?0.1 MeV. Neutron elastic- and inelastic-scattering cross sections were measured from ≈1.5 to 4.0 MeV, at incident-neutron energy intervals of ≈50keV and at ten or more scattering angles distributed between 20 and 160 degrees using neutron detection. Inelastic-scattering cross sections were also determined using the (n; n′,γ) reaction at incident energies from 1.6 to 3.8 MeV at intervals of 0.1 MeV. Gamma-rays and/or inelastically-scattered neutrons were observed corresponding to the excitation of levels at: 909.0±0.5, 1,507.4 ±0.3, 1,744.5±0.3, 2,222.6±0.5, 2,530±0.8, 2,566.4±1.0, 2,622.5±1.0, 2,871.9 ±1.5, 2,880.6±2.0, 3,067.0±2.0, 3,107.0±2.0, 3,140.0±2.0, 3,410.0±2.0, 3,450.0±2.0, 3,504.0 ±1.5, 3,514.0±2.0, 3,556.0±2.0, 3,619.0±3.0, 3,629.0±3.0 and 3,715.0±3.0 keV. The experimental results are discussed in terms of the spherical-optical-statistical, coupledchannels, and core-coupling models, and in the context of previously reported excitedlevel structure.     

Measurement of neutron elastic scattering cross sections for carbon at 134 MeV

Angular differential neutron elastic scattering cross sections have been measured by using a ⁷Li(p,n) quasi-monoenergetic neutron beam. The neutron beam whose peak energy is 134 MeV was incident upon a natural carbon sample, and the scattering neutrons were measured by liquid organic scintillators with the time-of-flight (TOF) technique. The results were compared with the existing experimental data measured by a recoil-proton telescope, and the evaluated nuclear data of JENDL/HE-2007 and ENDF/B-VII.0.     

Neutron activation cross sections at 14.7 MeV for isotopes of tungsten

Cross sections for (n, 2n), (n, p), (n, α) and [(n, n′p) + (n, pn)] reactions at 14.7 ± 0.3MeV on enriched ^{180, 182, 183, 184, 186}W isotopes have been measured by the activation technique using Ge(Li) detector γ-ray spectroscopy. Some systematic trends in the cross-section data have been analysed. The (n, 2n) reaction at this energy in this mass region is by far the most favoured reaction and accounts for > 80 % of the total inelastic cross section.     

Neutron emission spectra and angular distributions at 25.7 MeV neutron bombarding energies

Inelastic scattering of 25.7 MeV neutrons to unresolved final states with excitation energies up to ~13 MeV were measured for monoisotopic samples of ⁵¹V,⁵⁶Fe, ⁶⁵Cu, ⁹³Nb and ²⁰⁹Bi. Time-of-flight spectra were taken at several angles between 25° and 145° using the beam swinger spectrometer. Double differential cross sections, angle-integrated spectra and energy-binned angular distributions are compared with the predictions of pre-equilibrium theory.     

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.O and JEFF-3.1.1 near the angle of 90°at incident energies of 8.17 and 11.5 MeV,respectively.     

Hydrogen and deuterium total neutron cross sections in the MeV region

Total neutron cross sections, using a continuous-energy source of neutrons, were measured for hydrogen and deuterium. The neutron energy range covered was from less than 1 MeV, to about 30 MeV. No structure is observed for either isotope. The precision of the cross-section magnitudes appears to be within 1 % over much of the measured energy interval.     

Neutron scattering lengths and cross sections of the barium isotopes

Coherent neutron scattering lengths and total cross sections have been measured for barium compounds and on isotopically enriched samples for neutron energies from 0.5 meV up to 132 eV using different techniques. From the experimental data the following quantities were obtained:

the coherent scattering lengths (in fm) of Ba (5.07±0.03) and of the isotopes with mass numbers 130 (?3.6±0.6); 132 (7.8±0.3); 134 (5.7±0.1); 135 (4.66±0.10); 136 (4.90 ±0.08); 137 (6.82±0.10); and 138 (4.83±0.08).

the absorption cross sections σ_γ (at 0.025 eV in barn): of Ba (1.1±0.1) and of the isotopes: 130 (30±5); 136 (0.68±0.17); 137 (3.6±0.2); and 138 (0.27±0.14).

zero-energy scattering cross sections for Ba and the isotopes 136, 137 and 138. On the basis of these data, the isotopic- and spin-incoherent cross sections and the (s)-resonance contributions to the coherent scattering lengths have been determined and discussed.

     

Theoretical analysis of double-differential neutron emission cross sections for n+~(56)Fe 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 ENDFB Ⅶ.0 and JEFF-3.1.1 near the angle of 90° at incident energies of 8.17 and 11.5 MeV, respectively.     

Measurements of the total neutron cross sections of hydrogen and carbon at 0.5, 1.0 and 2.0 MeV

The total neutron cross sections of carbon and hydrogen were measured at 0.5, 1.0 and 2.0 MeV. The determination of the H(n, n) cross section often used as a standard was the major objective of the present measurements and values were obtained with accuracies of ～0.2 %, 0.2 % and 0.4 % respectively. A parameter set for the shape-independent effective-range approximation of the H(n, n) cross section was obtained with the present and other recent data indicating lower crosssection values than given in the Hopkins-Breit analysis.     

Neutron total cross sections on nuclei at Fermilab energies

We have measured total cross sections for neutrons on protons, deuteriom, beryllium, carbon, aluminium, iron, copper, cadmium, tungsten, lead, and uranium for momenta between 30 and 300 GeV/c. The measurements were carried out in a small-angle neutral beam at Fermilab. Typical accuracy of the data is 0.5 to 1%. The cross sections are consistent with an A^0.77±0.01 dependence over the entire momentum range. The cross sections are compared with theoretical predictions. Agreement is found only if inelastic screening is included. Nuclear radii obtained from our data are in good agreement with previous determinations.     

Neutron scattering from Bismuth,Strontium and Sodium at 14.8 MeV

Differential cross sections for the elastic and inelastic scattering of 14.8 MeV neutrons from Bi, Sr and Na have been measured with four neutron detectors participating in a time-of-flight system which had an energy resolution of 900 keV for the incident neutrons. The whole procedure was checked by scattering from carbon. For the elastic scattering of Bi, Sr and Na satisfactory optical-model fits were obtained. The absolute cross sections for excitation of collective states are compared to the distorted-wave theory for direct reactions, and a reasonable agreement has been found. The nuclear deformation parameters are extracted and compared to the values from other experiments.     

π− Production in16O +27Al at 38, 65 and 93 MeV/u

Negative pion production cross-sections are measured at 38, 65 and 93 MeV per nucleon in O + Al reaction. Rough estimations of the total cross sections are given and compared to previous neutral pion data. Double differential cross sections at 93 and 65 MeV/u show enhancement for pions with velocity close to the beam. At variance no effect is observed at 38 MeV, where π^? and π⁰ distributions are identical. Fewπ ⁺ detected at 38 MeV support this result. This indicates that at the lowest incident energy nearly the whole projectile participates in the production reaction.     

Differential cross sections of proton compton scattering at photon laboratory energies between 700 and 1000 MeV

Differential cross sections of proton Compton scattering have been measured at the Bonn 2.5 GeV synchrotron. 78 data points are presented as angular distributions at photon lab energies of 700, 750, 800, 850, 900, and 950MeV. The c.m. scattering angle ranges from 40°–130°, corresponding to a variation of the four momentum transfer squared betweent=?0.10 tot=?0.96 GeV² at 700 and 950 MeV, respectively. Two additional differential cross sections have been measured at 1000MeV, 35.6° and 47.4°. The angular distributions show forward peaks whose extrapolations to 0° are consistent with calculated forward cross sections taken from literature. The small angle data (|t| ?0.2 GeV²) together with the calculated cross sections at 0° are also consistent with the assumption of a slope parameterB of 5 GeV^?2. For the first time a rerise of the angular distributions towards backward angles has been observed. It becomes less steep with increasing energy. The most interesting feature of the angular distributions is a sharp structure which appears betweent=?0.55 GeV² at 700MeV andt=?0.72 GeV² at 950 MeV. Such a rapid varation of the differential cross section witht has never been ovserved in elastic hadron-hadron scattering or photoproduction processes. It indicates the existence of a dynamical mechanism which could be a peculiarity of Compton scattering.     

Differential cross sections for np and nd elastic scattering near 130 MeV

We have measured the np (nd) elastic scattering cross sections at 25(17) angles in the interval 30°–168° (c.m.), using a neutron beam with a broad spectrum peaked near 130 MeV. At backward angles the outgoing charged particles from a liquid hydrogen (deuterium) target were detected; at forward angles we detected neutrons scattered from a hydrogenated (deuterated) scintillating target. Cross sections have been normalized to the energy dependent solution of the Livermore nucleon-nucleon partial wave analysis, evaluated at 130 MeV. The np measurements represent a marginal improvement on previous work; the nd cross sections show some differences from pd measurements, in agreement with earlier indications at an energy of 152 MeV.     

Activation cross section for 27Al(π+,π0)27Si at 100 MeV

The activation cross section for ${}^{27}\text{Al}\text{(π}{}^{\mathrm{+}}\text{,π}{}^0\text{)}{}^{27}\text{Si at}\text{E}{}_{\mathrm{\pi }}\text{= 99 ± 9}\text{MeV}$ was determined to be 5.1 ± 2.2 mb by counting the residual β⁺ activity of ²⁷Si. This result is compared with other pion-nucleus cross sections. A value for the elementary pion-nucleon cross section inside the nucleus is derived from this result and compared with an estimate from a phenomenological expression.     

Optical model analysis of 14 to 40 MeV neutron elastic scattering from 27Al, 28Si and 32S

An optical model analysis of 14 to 40 MeV neutrons elastic scattering from 2s-1d shell nuclei ²⁷Al, ²⁸Si and ³²S is described. A set of spherical optical model parameters is presented for each nucleus. A regional neutron optical model, valid for nuclei near the center of the 2s-1d shell, is proposed. A comparison between neutron and relevant proton data, which entailed the analysis of the latter, confirms earlier determinations of the Coulomb correction term to the real potential and of the strength of the real isospin potential.