EROS II: A boosted time-of-flight reflectometer for multi-purposes applications at the Laboratoire Léon Brillouin
Laboratoire Léon Brillouin, CEA-CNRS, IRAMIS, F-91191, Gif sur Yvette, France
* e-mail: Fabrice.Cousin@cea.fr
Revised: 27 May 2011
Accepted: 11 November 2011
Published online: 11 November 2011
We present the characteristics and performances of the time-of-flight EROS reflectometer, located at Laboratoire Léon Brillouin (Saclay, France), which operates on the high-flux Orphée reactor. It is a versatile spectrometer with a horizontal geometry enabling air/liquid, air/solid and solid/liquid measurements. It is mostly dedicated to soft matter projects but welcomes also studies on thin solid films. It is equipped with a multi-disc chopper providing a tunable δλ/λ resolution, a collimation system with two deviating supermirrors and slits with flexible apertures allowing any given δθ/θ higher than 0.007, a large sample area, and a detector (either single tube or positioning sensitive detector). The accessible Q min is 0.0026 Å−1 and the accessible Q max is 0.36 Å−1 in air/solid or solid/liquid geometries and 0.21 Å−1 in air/liquid geometry. The spectrometer has been upgraded during the last decade in order to reach a gain in flux of ∼ 50 from its original version. In air/solid geometry, we reach R min = 2×10−5 in 1 hour, R min = 8×10−7 in 4 hours and R min = 4×10−7 in 12 hours on a sample of ∼ 20 cm2 with EROS II, while it was difficult to go below 10−5 with the initial version dating from 1992. In air/liquid or solid/liquid geometries, we show that the main limitation to reach very low reflectivities is the incoherent scattering of the liquid solvent (D2O) . For such geometries, we obtain R min of 5×10−6 in 4 hours after incoherent background subtraction. The rejuvenated EROS allows thus measurements of 15-20 samples of a few tens cm2 in a span of 4 days, which corresponds to the minimum time allocated to external users for a given experiment.
© Società Italiana di Fisica and Springer, 2011