Neutron interference scattering in crystalline solids Progress report
Neutron elastic and inelastic interference scattering cross section in crystalline lattices of solids
ELASTIC SCATTERING↗
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Selection of a system of functions for the excitation of levels during elastic scattering of neutrons by iron, nickel and niobium nuclei
Cross sections of inelastic scattering of neutrons by levels of iron, nickel, and niobium determined by spectra of gamma rays from decay of excited states
SCATTERING CROSS SECTION↗
Analytic expression for epithermal neutron spectra amplitudes as a function of water content
The epithermal portion of an equilibrium neutron spectrum in a planetary body is a function of the water content of its material. The neutrons are produced at high energies but are moderated by elastic and inelastic scattering until they either are captured by surrounding nuclei or escape. We have derived an expression that explicitly shows the dependance of epithermal neutron spectra on water content. Additionally, we compared its predictions to calculations done by Boltzman transport code for infinite media for silicon, oxygen, and a possible lunar composition, and we have obtained very good agreement.
Drake, Darrell↗
GAMBIT program
GAMBIT computer program provides multigroup flux and current averaged neutron cross sections for input to transport programs. The fast neutron compilation includes P/0/ and P/1/ elastic scattering transfer matrices, inelastic scattering matrices, n,2n cross section matrices, absorption and fission cross sections for all isotopes.
Collier, G.↗
Production cross sections for Lee-Wick massive electromagnetic bosons and for spin-zero and spin-one W bosons at high energies.
Production cross sections for three types of hypothetical particles are calculated in the presented paper. Several (Z, Z') cases were studied corresponding to elastic scattering off protons and neutrons (either free or embedded within a Fermi sea), coherent scattering off a nucleus, and inelastic scattering off a proton (in which case Z' denotes a nucleon resonance or hadronic system in the continuum). Detailed structure-function data are used to improve the accuracy of the inelastic scattering calculation. Results of calculations are given for beam energies between 50 and 10,000 GeV, and masses between 5 and 40 GeV for the massive Lee-Wick spin-1 boson. Cross sections were computed for resonant and semiweak processes. The production cross section of spin-zero weak intermediate bosons was found to be at least one order of magnitude smaller than for spin-1 weak bosons in nearly all regions of interest. The production cross section of spin-zero weak intermediate bosons for inelastic scattering off protons compares with that for elastic scattering in the regions of interest. In the case of massive spin-1 bosons and spin-1 weak intermediates, the main contribution to total production cross section off protons is elastic.
Linsker, R.↗
The response of a 300 micron silicon detector to monoenergetic neutrons determined by the use of the Monte Carlo technique
The response of a 300 micron thick silicon detector to an incident monoenergetic neutron beam is evaluated by the Monte Carlo method for the cases of both a shielded and a bare detector. The result of Monte Carlo calculation, using elastic, inelastic, and absorption reactions indicates that the response of the silicon detector to neutrons is basically due to the elastic scattering. In addition, the gamma rays generated in the shield of the detector will result in a response which is 3 or 4 orders of magnitude smaller than response to incident photons. The response of a bare silicon detector is calculated for neutron energies up to 6 MeV and bias energies from 50 to 250 KeV. It is found that the maximum response for a 300 micron thick silicon detector is less than .004 c/n within this selected neutron and bias energy range. When the pulse height defect is introduced in the calculation the results at low energy neutrons were reduced.
Tahezadeh, M.↗
Consistent Pl Analysis of Aqueous Uranium-235 Critical Assemblies
The lethargy-dependent equations of the consistent Pl approximation to the Boltzmann transport equation for slowing down neutrons have been used as the basis of an IBM 704 computer program. Some of the effects included are (1) linearly anisotropic center of mass elastic scattering, (2) heavy element inelastic scattering based on the evaporation model of the nucleus, and (3) optional variation of the buckling with lethargy. The microscopic cross-section data developed for this program covered 473 lethargy points from lethargy u = 0 (10 Mev) to u = 19.8 (0.025 ev). The value of the fission neutron age in water calculated here is 26.5 square centimeters; this value is to be compared with the recent experimental value given as 27.86 square centimeters. The Fourier transform of the slowing-down kernel for water to indium resonance energy calculated here compared well with the Fourier transform of the kernel for water as measured by Hill, Roberts, and Fitch. This method of calculation has been applied to uranyl fluoride - water solution critical assemblies. Theoretical results established for both unreflected and fully reflected critical assemblies have been compared with available experimental data. The theoretical buckling curve derived as a function of the hydrogen to uranium-235 atom concentration for an energy-independent extrapolation distance was successful in predicting the critical heights of various unreflected cylindrical assemblies. The critical dimensions of fully water-reflected cylindrical assemblies were reasonably well predicted using the theoretical buckling curve and reflector savings for equivalent spherical assemblies.
Fieno, Daniel↗
Dynamics of the iron spins in superconducting YBa2(Cu(1-x)Fe(x))O7
The dynamics of the iron spins in YBa2(Cu(1-x)Fe(x))3O7 alloys (0 = to or less than 0.12) was studied by the means of inelastic neutron scattering. Measurements were performed using the time of flight technique with an excellent resolution of 50 micro eV, in a temperature range of 1.8 to 300 K. The doped samples show an elastic and a quasielastic intensity strongly varying with temperature. A spin glass like freezing is revealed at low temperature by a sudden decrease of the quasielastic intensity, an increase of the elastic or resolution limited intensity and a minimum in the quasielastic width. The freezing temperature corresponds to the one already determinated by a magnetic splitting in Mossbauer experiments. Above freezing, the occurrence of superconductivity slightly modifies the characteristics of the spin relaxation in the paramagnetic state, as shown by measurements in two x = 0.06 samples. In the whole temperature range of measurement, the dependence of the quasielastic intensity with the scattering vector q, mainly reflects the variation of the Iron form factor, which shows that the spins are almost uncorrelated.
Mirebeau, I.↗