Upgrade of the KWS-2 high-intensity/extended-Q-range SANS diffractometer of JCNS for soft matter and biophysics: in situ SEC, controlled in situ RH/T variation and WANS detection.

Abstract

The KWS-2 small-angle neutron scattering (SANS) diffractometer operated by Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum, Garching, Germany, is dedicated to the investigation of mesoscopic multi-scale structures and structural changes due to rapid kinetic processes in soft condensed matter and biophysical systems. Following requests from the user community, it has been repeatedly upgraded with respect to the most important methodological parameters of an instrument of this type, namely the intensity on the sample, the instrumental resolution and the minimum scattering variable Q _min. Here we report on further specific improvements to the sample environment and detection capabilities which have just been completed or are being implemented. Complementary size-exclusion chromatography (SEC) for in situ protein purification was developed and optimized at KWS-2 to provide the instrument with biological samples of controlled quality. The instrument is also currently being equipped with a wide-angle neutron scattering (WANS) detector which will allow it to bridge the atomic and mesoscale, benefiting from the instrument's adjustable resolution down to Δλ/λ = 2%. For controlled relative humidity and temperature (RH/T) on ionic conductive samples for energy applications or biomembranes for biophysical and health applications, a precise dew point generator has recently been characterized and commissioned; this offers great versatility with regard to varying the contrast in situ in the beam on hydrated samples.