The extendedQ-range small-angle neutron scattering diffractometer at the SNS

Abstract

The extended Q-range small-angle neutron scattering diffractometer (EQ-SANS) at the Spallation Neutron Source (SNS), Oak Ridge, is designed for wide neutron momentum transfer (Q) coverage, high neutron beam intensity and good wavelength resolution. In addition, the design and construction of the instrument aim to achieve a maximum signal-to-noise ratio by minimizing the background. The instrument is located on the high-power target station at the SNS. One of the key components in the primary flight path is the neutron optics, consisting of a curved multichannel beam bender and sections of straight neutron guides. They are optimized to minimize neutron transport loss, thereby maximizing the available flux on the sample. They also enable the avoidance of a direct line of sight to the neutron moderator at downstream locations. The instrument has three bandwidth-limiting choppers. They allow a novel frameskipping operation, which enables the EQ-SANS diffractometer to achieve a dynamic Q range equivalent to that of a similar machine on a 20 Hz source. The two-dimensional low-angle detector, based on 3 He tube technologies, offers very high counting rates and counting efficiency. Initial operations have shown that the instrument has achieved its design goals.

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

“…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 . With the very recent commission of the specialized TOF-SANS diffractometers at steady-state reactors 24 or spallation sources 25,26 , a massively-increased dynamic Q range in a given experimental setup and increased flexibility and optimization regarding the choice of the experimental resolution are offered. For the KWS-2 SANS diffractometer, a high level of versatility and performance required for very specific structural studies in the field of soft matter and biophysics is enabled on an otherwise classical SANS instrument.…”

Axisymmetric grazing-incidence focusing optics for small-angle neutron scattering

“…To reach the smallest required Q min , long 's are used, thus requiring long evacuated detector tanks. For instance, EQ-SANS has a 10 m detector tank [21], GP-SANS at HFIR (High Flux Isotope Reactor, ORNL) has a 20 m detector tank [24], and NG3 SANS in NIST has a 13 m detector tank [25]. These huge vacuum tanks are expensive, cumbersome, and require a lot of maintenance.…”

“…Focusing mirrors must be optimized for a particular SANS instrument, since the performance of the optics depends on the mirror sizes, focal distances, and neutron energies, which determine critical angles. Therefore, the ray-tracing analysis was performed for an existing SANS diffractometer, EQ-SANS at the Spallation Neutron Source (SNS) [21,22].…”

Probing Peptide-Membrane Interaction by Neutron Scattering

“…With H2O/D2O contrast variation and selective deuterium labeling techniques, different compositions in a membrane complex can be distinguishable, and different parts of structure can be accessed either separately or wholly. A few neutron scattering methods for studying peptide-membrane interaction introduced here are implemented at the SANS instruments located in Oak Ridge National Laboratory [1,2].…”