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S A Werner

Publications and source records attributed to S A Werner.

5 recordsLinked to original sources
PubMed2004

Thermal and cold neutron phase-contrast radiography.

In this paper, we will discuss a phase-contrast imaging method that avoids the complications of interferometry to provide phase contrast in weakly absorbing samples. A transversely coherent neutron beam is used with the traditional radiography scheme. Images taken with this scheme show dramatic intensity variations due to sharp changes in the neutron wave refractive index. With some numerical processing these images may be used to reconstruct a quantitative phase radiograph of specimens imaged with this technique.

Journal Article↗
PubMed2003

Quantitative phase radiography with polychromatic neutrons.

We develop and experimentally demonstrate a formalism that allows accurate phase imaging using neutron sources producing highly polychromatic beams. The results of measurements from a rectangular block of silicon compare favorably with theoretical simulations based upon the known composition and geometry of the block. The increased flux and reduced exposure times will permit a simple extension of the technique to tomographic phase imaging.

Journal Article↗
PubMed2003

Precision neutron interferometric measurement of the nd coherent neutron scattering length and consequences for models of three-nucleon forces.

We have performed the first high precision measurement of the coherent neutron scattering length of deuterium in a pure sample using neutron interferometry. We find b(nd)=(6.665+/-0.004) fm in agreement with the world average of previous measurements using different techniques, b(nd)=(6.6730+/-0.0045) fm. We compare the new world average for the nd coherent scattering length b(nd)=(6.669+/-0.003) fm to calculations of the doublet and quartet scattering lengths from several modern nucleon-nucleon potential models with three-nucleon force (3NF) additions and show that almost all theories are in serious disagreement with experiment. This comparison is a more stringent test of the models than past comparisons with the less precisely determined doublet scattering length of (2)a(nd)=(0.65+/-0.04) fm.

Journal Article↗