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The reflectometer allows measuring the neutron optical reflectivity on flat surfaces at grazing angles. The reflectivity is related to the variation of the refractive index within a depth of about 100 nm, thus structural depth profiles can be studied. The reflectometer is with vertical scattering geometry and it is installed at BERII reactor at HMI, Berlin. The beam is collimated by two sets of computer controlled cadmium slits. For solid samples the angle of incidence is usually varied by a precise tilting of the sample surface relative to the (fixed) collimated neutron beam. Thus an angular range of 0° - 3.5° is accessible. Liquid samples can be measured using the vertically focussing monochromator. In this mode the sample surface is kept horizontal and the angle of incidence is varied by a precise movement of the slit system. Thus an angular range of 0°-2° is accessible. In both modes of operation an angular resolution is 0.001° - 0.01° depending on the collimation. The detector is an array of 3He gas-detectors with high efficiency, moving in a vertical plane. The typical neutron flux at the sample is 3x104 n.cm2/s, a reflectivity down to 2x10-5 is accessible for large enough samples. All instrument components and the sample environments are computer controlled. For the analyses of the reflectivity data the necessary fitting programs are provided. The instrument is equipped with heatable cell for studies of solid/liquid interfaces, tightly closed cell for solid/gas interfaces and Langmuir Blodgett trough for liquid/air interfaces. It is suitable for studies of multilayered organic or inorganic structures and liquid and solid surfaces.
The use of polarized neutrons allows in a unique way also the reconstruction of magnetic properties and depth profiles near surfaces. In this mode of operation magnetic penetration depth in superconductors and magnetic properties of thin layers or multilayers can be obtained.
- Place: Hahn-Meitner Institute, Berlin, Glienicker Strasse 100, 14109 Berlin
- Country: Germany
- Partner: Dr. Rumen Krastev, Hahn-Meitner Institute, Fon: ++ 49 (0) 30 / 8062 3077, E-mail: krastev@hmi.de, krustev@mpikg.mpg.de
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