Intensity and resolution effects in converging multichannel collimators for SANS by Monte Carlo simulation

A study of the contribution of the individual channels of a converging multichannel collimator to the operation of the device is carried out by means of a Monte Carlo computer simulation. The simulation shows that the coupling between the divergence of the incident neutron beam and the inclination of the individual CMC channel axis relative to the beam direction modulates the channel performance as far as intensity and resolution of the transmitted neutrons are concerned. While this does not impair in any significant way the usefulness of the device, the results are helpful to the designer.

Monte Carlo simulation of a reactor-based neutron strain scanning diffractometer

A Monte Carlo code for the simulation of neutron strain scanning experiments on a reactor-based two-axis diffractometer is described. In order to validate this code, several experiments have been performed. A comparison is made between experimental and simulated results for instrumental resolution, primary beam divergence and wavelength distribution in the incident neutron beam. Finally, the application of the simulation results to the analysis of a real neutron strain scanning experiment is outlined.

Internal Strains Of A Creep Deformed Single Crystal Nickel-Based Superalloy

ABSTRACTNeutron scattering experiments have been carried out with undeformed and creep deformed samples of the superalloy CMSX-4. From the measured constrained misfit data, obtained from different reflecting planes with respect to the external load axis, two strain tensors for horizontal and vertical matrix plates can be extracted.A careful data analysis is necessary since the technical manufactured single crystals show a mosaic spreading of 0.5° and the wavelength spreading of the incident neutron beam, Δλ/λ is about 410-3 This is in the same range as the unknown constrained misfit quantities δc. A method has been developed which allows a calculated intensity distribution to be fitted to the measured one.

THE SPECTRUM OF NEUTRONS FROM THE IRRADIATION OF URANIUM BY 14-MEV NEUTRONS

The spectrum and absolute yield of neutrons resulting from 14-Mev neutrons incident on natural uranium was observed at 90°± 16 to the incident neutron beam by a time-of-flight method. Further observations of the spectrum from 9 to 13.5 Mev were made for scattering angles at 30° and 60°. In addition to the expected neutrons resulting from evaporation and fission, strong evidence is seen for direct interaction inelastic scattering. The (n,n′) cross section is estimated to be 150 ± 70 millibarns.