HK8 - SANS and Neutron Optics Diffractometers

Neutron beam at the channel HK8 hosts two experimental facilities: High-resoiution SANS Diffractometer (MAUD) and Neutron Optics Diffractmeter (NOD). The two instruments use monochromatic beams selected by bent Si 111 and Si 220 monochromators situated in common shielding block. Such a construction is possible thanks to the very low absorption of silicon for thermal neutrons so that the first monochromator leaves the wavlength band for the second one almost intact. The common primary beam is shaped by a newly installed (in 2009) collimator with dimensions optimized for the beam size and divergence employed by the SANS instrument. It contains 10 cm thick sapphire filter and a sequence of B4C and Pb inserts in order to minimize gamma and neutron background and to suppress contamination of the beam by high-order Bragg reflections. The monochromators shielding is composed from inner Pb container and outer 40 cm thick wall made of concrete filled with B4C powder. The secondary collimators are equipped with horizontally and vertically adjustable slits, which permit fine tuning of required beam size delivered to the sample area.

 

  • Double-Crystal SANS Diffractometer (MAUD)

    (former DN2)

    The double-crystal diffractometer MAUD is designed for the measurements of neutron small-angle scattering in the high Q-resolution range. In contrast to conventional double-crystal arrangements, the fully asymmetric diffraction geometry on the elastically bent Si analyzer is employed to transfer the angular distribution of the scattered neutrons to the spatial distribution and to analyze the whole scattering curve by a one-dimensional position sensitive detector. It reduces the exposition time per sample typically to 0.5-5 hours (depending on the Q-resolution and sample cross-section). The remote control of the curvatures of the monochromator and analyzer crystals makes possible to tune the instrument resolution easily in the dQ range from 10-4 to 10-3 Ă -1, according to the expected size of investigated inhomogeneities. An absolute calibra-tion of scattering cross-sections is possible by measuring the intensity of the direct beam (no calibration samples are required). The instrument operates in fully automatic mode, including sample exchange.

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  • Instrument Parameters

    Monochromator bent perfect crystal Si(111), symmetric reflection
    Sample maximum cross-section 5x25 mm2
    Analyzer bent perfect crystal Si 111, fully asymmetric geometry
    Detector 1-dimensional position sensitive detector, 3He filled, resolution ~ 1 mm
    Wavelength 2.1 Ă
    Neutron flux 5x103 ÷ 5x104 n s-1 cm-2
    Q-resolution 10-4 ÷ 10-3 Ă-1
    Q-range 2x10-4 ÷ 2x10-2Ă-1
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  • Neutron Optics Diffractometer (NOD)

    to be completed

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