Mitigating background caused by extraneous scattering in small-angle neutron scattering instrument design

Measurements, calculations and design ideas to mitigate background caused by extraneous scattering in small-angle neutron scattering (SANS) instruments are presented. Scattering includes processes such as incoherent scattering, inelastic scattering and Bragg diffraction. Three primary sources of this type of background are investigated: the beam stop located in front of the detector, the inside lining of the detector vessel and the environment surrounding the sample. SANS measurements were made where materials with different albedos were placed in all three locations. Additional measurements of the angle-dependent scattering over the angular range of 0.7π–0.95π rad were completed on 16 different shielding materials at five wavelengths. The data were extrapolated to cover scattering angles from π/2 to π rad in order to estimate the materials' albedos. Modifications to existing SANS instruments and sample environments to mitigate extraneous scattering from surfaces are discussed.

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Silver behenate powder as a possible low-angle calibration standard for small-angle neutron scattering

Journal of Applied Crystallography ◽

10.1107/s0021889898004440 ◽

1998 ◽

Vol 31 (6) ◽

pp. 957-959 ◽

Cited By ~ 28

Author(s):

R. Gilles ◽

U. Keiderling ◽

A. Wiedenmann

Keyword(s):

Neutron Scattering ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Angular Range ◽

Calibration Standard ◽

X Ray Diffraction ◽

Transmission Method ◽

Wavelength Calibration ◽

X Ray ◽

Flight Measurements

Small-angle neutron scattering (SANS) is a transmission method working in the angular range 0.4–6° (2θ). In this paper, silver behenate powder [CH3(CH2)20COOAg] (referred to as `AgBE'), one of the very few materials featuring Bragg reflections in the angular range accessible to SANS instruments, is suggested as a possible new SANS wavelength calibration standard. In the past, this powder has been successfully tested as a calibration standard in low-angle X-ray diffraction. Results of new SANS wavelength calibration measurements performed with AgBE and with the traditional method of time-of-flight measurements are presented and compared with low-angle X-ray diffraction measurements.

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Polarization analysis for small-angle neutron scattering with a 3He spin filter at a pulsed neutron source

Journal of Applied Crystallography ◽

10.1107/s1600576721001643 ◽

2021 ◽

Vol 54 (2) ◽

pp. 548-556

Author(s):

Takuya Okudaira ◽

Yuki Ueda ◽

Kosuke Hiroi ◽

Ryuhei Motokawa ◽

Yasuhiro Inamura ◽

...

Keyword(s):

Neutron Scattering ◽

Neutron Source ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Incoherent Scattering ◽

Polarization Analysis ◽

Spin Filter ◽

Scattering Intensity ◽

Pulsed Neutron ◽

Pulsed Neutron Source

Neutron polarization analysis (NPA) for small-angle neutron scattering (SANS) experiments using a pulsed neutron source was successfully achieved by applying a 3He spin filter as a spin analyzer for the neutrons scattered from the sample. The cell of the 3He spin filter gives a weak small-angle scattering intensity (background) and covers a sufficient solid angle for performing SANS experiments. The relaxation time of the 3He polarization is sufficient for continuous use for approximately 2 days, thus reaching the typical duration required for a complete set of SANS experiments. Although accurate evaluation of the incoherent neutron scattering, which is predominantly attributable to the extremely large incoherent scattering cross section of hydrogen atoms in samples, is difficult using calculations based on the sample elemental composition, the developed NPA approach with consideration of the influence of multiple neutron scattering enabled reliable decomposition of the SANS intensity distribution into the coherent and incoherent scattering components. To date, NPA has not been well established as a standard technique for SANS experiments at pulsed neutron sources such as the Japan Proton Accelerator Research Complex (J-PARC) and the US Spallation Neutron Source. It is anticipated that this work will contribute significantly to the accurate determination of the coherent neutron scattering component for scatterers in various types of organic sample systems in SANS experiments at J-PARC, particularly for systems involving competition between the coherent and incoherent scattering intensity.

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Silica Fouling in Reverse Osmosis Systems–Operando Small-Angle Neutron Scattering Studies

Membranes ◽

10.3390/membranes11060413 ◽

2021 ◽

Vol 11 (6) ◽

pp. 413

Author(s):

Vitaliy Pipich ◽

Thomas Starc ◽

Johan Buitenhuis ◽

Roni Kasher ◽

Winfried Petry ◽

...

Keyword(s):

Ionic Strength ◽

Neutron Scattering ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Volume Fraction ◽

Cross Flow ◽

Bragg Diffraction ◽

Layer Formation ◽

Permeate Flux ◽

Cake Layer

We present operando small-angle neutron scattering (SANS) experiments on silica fouling at two reverse osmose (RO) membranes under almost realistic conditions of practiced RO desalination technique. To its realization, two cells were designed for pressure fields and tangential feed cross-flows up to 50 bar and 36 L/h, one cell equipped with the membrane and the other one as an empty cell to measure the feed solution in parallel far from the membrane. We studied several aqueous silica dispersions combining the parameters of colloidal radius, volume fraction, and ionic strength. A relevant result is the observation of Bragg diffraction as part of the SANS scattering pattern, representing a crystalline cake layer of simple cubic lattice structure. Other relevant parameters are silica colloidal size and volume fraction far from and above the membrane, as well as the lattice parameter of the silica cake layer, its volume fraction, thickness, and porosity in comparison with the corresponding permeate flux. The experiments show that the formation of cake layer depends to a large extent on colloidal size, ionic strength and cross-flow. Cake layer formation proved to be a reversible process, which could be dissolved at larger cross-flow. Only in one case we observed an irreversible cake layer formation showing the characteristics of an unstable phase transition. We likewise observed enhanced silica concentration and/or cake formation above the membrane, giving indication of a first order liquid–solid phase transformation.

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