Development of an ultra-small-angle X-ray scattering instrument for probing the microstructure and the dynamics of soft matter

Abstract

A Bonse-Hart camera suitable for studying dilute and weakly scattering systems has been developed. The required level of reduction of the parasitic background scattering was realised by replacing channel-cut crystals by a pair of polished and deeply etched parallel crystals. The performance of this ultra-small-angle X-ray scattering instrument is illustrated by means of two examples: the microstructure of a short-range attractive colloidal system; and the growth dynamics of soot particles in a diffusion flame. In addition, the feasibility of performing dynamic X-ray scattering experiments is demonstrated.

Everything SAXS: small-angle scattering pattern collection and correction

“…The wavelength spread in these systems typically assumes values smaller than 10 −3 and is therefore often not considered [140]. For Bonse-Hart instruments, however, the monochromaticity is tied to the instrument resolution and its consideration is therefore a necessity [26,178,203]. The smearing effect due to the sample thickness is similarly very small.…”

“…Given the particulars of the data, Bonse-Hart data correction may require additional consideration (e.g. for the determination of the sample transmission factor and the effects of the rocking curve on the data) [26,178,203].…”

“…While a large variety of crystalline materials can be used in the instrument, the channel-cut crystals are usually made from either silicon or germanium due to their high degree of crystalline perfection over large sizes [5]. These crystals have Darwin widths (FWHM) for the common (111) and (220) x-ray reflections of about 0.0002 • , thus defining the q-resolution for most such instruments to be about 0.001 nm −1 (where the multiple reflections do not change the Darwin width, but improve the off-reflection rejection) [26,178,40,65,106]. When a higher resolution is required, for example to measure larger structures, the combination of high-energy and higher-order crystalline reflections can lead to a ten-fold increase in resolution [82].…”

Glassy Carbon as an Absolute Intensity Calibration Standard for Small-Angle Scattering

“…A USAXS instrument, designed after the BonseHart double-crystal configuration, [15][16][17] offers a primary method of providing an absolute intensity calibration without the need for beam attenuation or an intensity calibration standard sample of any kind. [15] The instrument at the Advanced Photon Source (APS), Argonne National Laboratory, [16] takes advantage of a silicon photodiode detector that gives a linear signal response over 11 decades of scattering intensity, [18] enabling it to measure the full incident beam intensity without loss of linearity.…”

Analysis of structures of rubber-filler systems with combined scattering methods

“…Recently, Bonse-Hart cameras have also been installed at synchrotron facilities. 18,19 In particular, Ilavsky et al 20 succeeded in measuring two-dimensional (2D) USAXS images by using two sets of monochromators and analyzers, which were positioned both vertically and horizontally.…”