New evanescent neutron wave diffractometer at LLB

A new surface diffraction option has been mounted on the reflectometer EROS at the Laboratoire Leon Brillouin (LLB). The originality of the design lies in the fact that we are working in a Laue-type configuration. The sample is mounted horizontally on a goniometric table. A position-sensitive detector (PSD; 200 mm × 200 mm) can be swept around the sample in the horizontal plane. The sample is illuminated by a white beam, the Bragg diffraction angle is defined by the PSD position, the dhkl is fixed by the material then according to Bragg’s law the wavelength is selected. Time-of-flight measurements can be performed to measure the diffracted wavelength. Measurements on 1-cm2 samples show that the intensity in the surface diffraction peaks at about 0.5–1 counts s-1.Measurements have been performed on non-magnetic crystals and on a magnetic Co epitaxial thin film.