Speaker
Mr
Steven Peetermans
(Paul Scherrer Institut)
Description
Neutron radiography and its extension to tomography is based on transmission contrast by varying macroscopic cross sections in the sample of interest. Traditionally, a polychromatic beam is used, which enables to discriminate between different sample materials and thicknesses.
By using a tunable monochromatic, cold neutron beam one can scan in transmission polycrystalline samples over the cold energy range, where so-called Bragg edges dominate the cross section. Those edges can be understood in the context of the Bragg law 2dhklsin(θhkl)=λ, where coherent elastic scattering at the hkl lattice plain is possible until 2dhkl=λ, after which a sharp increase in transmission intensity is observed because of decreased sample scattering out of the beam. In energy selective neutron imaging around these Bragg edges lays a new source of image contrast that contains microstructural information on the sample. It has the potential of becoming a new tool for material research complementary to existing diffraction techniques. The approach can also be extended to 3D tomography studies on request.
A first part of this poster is dedicated to a study on the use of two monochromator types for energy selective imaging: the neutron velocity selector and a newly developed monochromator called TESI. The first features a large field-of-view and a monochromaticity Δλ/λ=15% realized through mechanical selection of the desired neutron energies. TESI uses a set of single crystals to scatter neutrons of unwanted energies out of the direct beam, to obtain a final monochromaticity of Δλ/λ=2%-5%.
The second part of the poster deals with applications of energy-selective neutron imaging, with special focus on the combination with neutron diffraction imaging.
Primary author
Mr
Steven Peetermans
(Paul Scherrer Institut)
Co-authors
Dr
Eberhard Lehmann
(Paul Scherrer Institut)
Ms
Lidija Josic
(Paul Scherrer Institut)
