W0114

A Quick and Exact Method for Wavelength Calibration of SANS Instruments Using Silver Behenate. U. Keiderling^(1,2), R. Gilles⁽¹⁾, A. Wiedenmann⁽¹⁾, ⁽¹⁾Hahn-Meitner-Institut Berlin, Glienicker Str. 100, 14109 Berlin, Germany, ⁽²⁾Technical University Darmstadt, Petersenstr. 23, 64287 Darmstadt, Germany

Silver Behenate powder (AgBE) was used for neutron wavelength calibration of the monochromator system of the SANS instrument ÒV4Ó at the steady-state reactor "BER II", Hahn-Meitner-Institut Berlin, Germany. The monochromator system consists of a rotating mechanical velocity selector which allows a continuous setting of the transmitted wavelength depending on the speed of the selector. In the past, the usual method to determine the wavelength as a function of the selector speed were time-of-flight measurements which required a chopper and a special time-resolving electronical equipment. In the present paper, an alternative method for wavelength calibration with AgBE in the standard SANS measurement set-up is described. AgBE is one of the few materials featuring Bragg peaks in the angular range accessible to SANS instruments. This allows the easy calculation of the wavelength from the angular peak positions in the neutron diffraction pattern. The long-period spacing of AgBE required as an input parameter for this calculation has been determined before with high accuracy from X-ray diffraction measurements. The optimum geometry for the SANS measurements and the influence of different raw data reduction methods are described in detail.