KWS-2, the high intensity / wideQ-range small-angle neutron diffractometer for soft-matter and biology at FRM II

Abstract

The KWS-2 small-angle neutron diffractometer operated by JCNS at FRM II is upgraded and optimized towards high intensity and wide Q-range studies of mesoscopic structures and structural changes due to rapid kinetics and becomes a dedicated SANS instrument to soft-matter and biology. The high intensity permits fast measurement of small or weak scattering samples and time resolved structural studies with a time resolution up to 100ms. The possibility to cover up to four decades in Q will soon enable structural investigation over a wide length scale, between several Å and 1μm. The characteristics and performance of the instrument in the conventional pinhole mode is detailed presented and the new upgrades currently in progress and aiming for boosting the instrument performance towards higher intensity and wider Q-range are reported.

Studying Soft-matter and Biological Systems over a Wide Length-scale from Nanometer and Micrometer Sizes at the Small-angle Neutron Diffractometer KWS-2

“…The transmitted beam in this case was monitored with Monitor 3 at a short detection distance L D = 2 m. In this case, the gravity effects are weak and the direct beam falls on the beam-stop (like in the Figure 8A). The data collected two-dimensionally on the detector for a pixel size of 5.25 mm x 5.25 mm were further corrected for the detector sensitivity, and the contributions from the empty cell, instrument background, and solvent were absolutely calibrated using the scattering from the Plexiglas secondary standard 4 . Finally, the scattering patterns that were isotropically distributed around the position Q→0 were averaged radially, which delivered the dΣ/dΩ for each polystyrene particle system.…”

“…Based on the relaxed wavelength resolution, the KWS-2 has a nearly doubled flux 2,4 . Recently, very specialized SANS diffractometers became operational to serve with optimized characteristics for a specific range of applications, such as for investigations at very small scattering vectors 22,23 .…”

“…The SANS diffractometer KWS-2 (Figure 1), operated by the Jülich Centre of Neutron Science (JCNS) at the Heinz Maier-Leibnitz Center (MLZ) in Garching, was originally a classical pinhole SANS instrument benefiting from a high neutron flux (Supplementary Figure 1) delivered by the FRM II neutron source 1 and the dedicated guide system [2][3][4] . After repeated upgrades, the instrument was optimized for the exploration of a wide Q range, between 1x10 -4 and 0.5 Å -1…”

“…The detector is typically placed in the tower on the top of the vacuum tank at a fixed distance L D = 17 m and can be vertically moved in or out of the beam (Figure 1). The main detector is parked in the end position of the tank at 20 m, while the secondary detector is moved in the beam when high-resolution investigations (low Q) using lenses are being performed 4,7 . The secondary detector is placed in one focal point of the lens system, while a small entrance aperture at L C = 20 m would be, in this case, in the other focal point.…”

Systematic Limitations in Concentration Analysis via Anomalous Small-Angle X-ray Scattering in the Small Structure Limit

“…The capillaries were closed with a pipette plug fixed by two-component quick setting adhesive. The SANS measurements have been performed at the Jülich Center for Neutron Science (JCNS) with the beam line KWS-2 at the FRM II (Forschungsreaktor München of the Technische Universität München, Garching, Germany) [37]. The samples were filled in standard Helma cells with a thickness of 2 mm and have been exposed to a neutron beam of wavelength 0.7 nm at sample detector distances of 2, 8, and 20 m. Along with the sample solvent measurements have been performed using 0.1 M NaNO 3 in D 2 O.…”