Neutron reflectivity

The specular neutron reflectivity is a technique enabling the measurement of neutron scattering length density profile perpendicular to the plane of a surface or an interface, and thereby the profile of chemical composition. The characteristic sizes that are probed range from around 5 Å up 5000 Å. It is a scattering technique that averages information on the entire surface and it is therefore not possible to obtain information within the plane of the interface. The specific properties of neutrons (possibility of tuning the contrast by isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) makes it particularly interesting in the fields of soft matter, biophysics and magnetic thin films. This course is a basic introduction to the technique and does not address the magnetic reflectivity. It is composed of three parts describing respectively its principle and its formalism, the experimental aspects of the method (spectrometers, samples) and two examples related to the materials for energy

UCANS-8 in Paris Eighth International Meeting of the Union for Compact Accelerator-Driven Neutron Sources

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The SONATE project, a french CANS for materials sciences research

International audienceWe describe the Compact Accelerator-based Neutron Source SONATE which we are aiming for to replace the close Orphée reactor at Saclay, France. The SONATE source would serve an instrumental suite of about 10 instruments. The instruments would be split into low resolution instruments and higher resolution instruments. Our reference design is based on a proton accelerator operating at an energy in the range 20-30 MeV. The accelerator would serve 2 target stations. The first one operating at 20Hz with 2ms long pulses serving low resolution instruments (SANS, reflectivity, imaging, spin-echo) and the second one operating at 100Hz, 200µs long pulses serving higher resolution instruments (powder diffraction, Direct Time-of-flight spectroscopy, Indirect geometry spectroscopy). The 2 operation modes would be interlaced. The peak current on the target is aimed at 100 mA with an average power on the target on the order of 50-80 kW. Numerical Monte-Carlo simulations show that we may expect instrument performances equivalent to the current instruments around Orphée or ISIS

UCANS – 8, Paris, July 8-11 th 2019 Eighth International Meeting of the Union of Compact Accelerator-based Neutron Sources

International audienc

SONATE, a French CANS for materials science research

International audienc

Orthorhombicity and oxygen uptake by YBa2Cu3O6 + x

We have measured, at different oxygen contents, the cell parameters of YBa2Cu3O6+x between 24 and 260 K using cold neutrons. The results of profile refinement of our high resolution data is shown in figure 1 ; it does not confirm the X-ray finding, recently reported [1], showing a cusp in the orthorhombic splitting b — a, around the superconducting transition temperature. It has also been evidenced that the volume of the crystallographic cell is contracted by oxygen uptake.Nous avons mesuré, à différents taux d'oxygène, les paramètres de maille de YBa2Cu3O6+x entre 24 et 260 K à l'aide de neutrons froids. L'affinement de nos résultats, présenté sur la figure 1, ne nous permet pas de confirmer les mesures de rayons-X, récemment publiées [1], montrant une anomalie de l'orthorhombicite b - a, au voisinage de la température de transition supraconductrice. Il a aussi, été mis en évidence que le volume de la maille cristallographique se contractait par absorption d'oxygène