Abstract
The small angle neutron scattering (SANS) of nearly Q-independent nuclear spin-incoherent scattering from hydrogen present in most soft matter and biology samples may raise an issue in structure determination in certain soft matter applications. This is true at high wave vector transfer Q where coherent scattering is much weaker than the nearly Q-independent spin-incoherent scattering background. Polarization analysis is capable of separating coherent scattering from spin-incoherent scattering, hence potentially removing the nearly Q-independent background. Here we demonstrate SANS polarization analysis in conjunction with the time-of-flight technique for separation of coherent and nuclear spin-incoherent scattering for a sample of silver behenate back-filled with light water. We describe a complete procedure for SANS polarization analysis for separating coherent from incoherent scattering for soft matter samples that show inelastic scattering. Polarization efficiency correction and subsequent separation of the coherent and incoherent scattering have been done with and without a time-of-flight technique for direct comparisons. In addition, we have accounted for the effect of multiple scattering from light water to determine the contribution of nuclear spin-incoherent scattering in both the spin flip channel and non-spin flip channel when performing SANS polarization analysis. We discuss the possible gain in the signal-to-noise ratio for the measured coherent scattering signal using polarization analysis with the time-of-flight technique compared with routine unpolarized SANS measurements.
Highlights
Over the last three decades, small-angle neutron scattering (SANS) has been a powerful probe for determining the size, shape, distribution, inter- and intra-structures of particles or aggregates, such as colloidal particles, surfactant aggregates, and polymers, often existing in soft condensed matter and biology
In order to determine the weak coherent scattering that carries the structural information of the sample, it is necessary to subtract out the nuclear spin-incoherent (NSI) background accurately, which is typically independent of the wave vector transfer Q
Proper data reduction and the Monte Carlo simulation for multiple scattering estimation, we have unambiguously separated the first diffraction peak of silver behenate from the strong spin-incoherent background for a sample of silver behenate back filled with 1 mm-thick light water that is known to exhibit strong nuclear spin-incoherent scattering, inelastic scattering and multiple scattering
Summary
Over the last three decades, small-angle neutron scattering (SANS) has been a powerful probe for determining the size, shape, distribution, inter- and intra-structures of particles or aggregates, such as colloidal particles, surfactant aggregates, and polymers, often existing in soft condensed matter and biology. In order to determine the weak coherent scattering that carries the structural information of the sample, it is necessary to subtract out the nuclear spin-incoherent (NSI) background accurately, which is typically independent of the wave vector transfer Q. SANS polarization analysis has been demonstrated for separation of coherent and incoherent scattering in special soft matter samples [3, 11, 12, 13]. The inelastic scattering mixes with the nuclear spin-incoherent scattering, making it impossible to be separated in the current SANS polarization analysis method [3, 4]. We report the development of SANS polarization analysis in conjunction with the time-of-flight technique using a chopper to effectively remove the inelastic scattering background. Where T0 is the transmission for an unpolarized neutron beam passing through a unpolarized 3He cell
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