Abstract
We describe an experiment container with light scattering and imaging diagnostics for experiments on soft matter aboard the International Space Station (ISS). The suite of measurement capabilities can be used to study different materials in exchangeable sample cell units. The currently available sample cell units and future possibilities for foams, granular media, and emulsions are presented in addition to an overview of the designand the diagnostics of the experiment container. First results from measurements performed on ground and during the commissioning aboard the ISS highlight the capabilities of the experiment container to study the different materials.
Highlights
Dispersions of grains, bubbles, or droplets in a continuous phase with a different density are unstable in the presence of gravity due to drainage, sedimentation, and creaming
The light scattering diagnostics were designed to probe the inner dynamics of opaque samples using Diffusing Wave Spectroscopy (DWS17,18,21,22) and Time-Resolved Correlation spectroscopy (TRC23) and to characterize the inner structure of the samples using Diffuse Transmission Spectroscopy (DTS,24)
This is of interest because many studies have shown that coarsening of foams of arbitrary initial structure leads to a statistical self-similarity, where the bubble size distributions at different times collapse on a master plot if the sizes are scaled by their average values
Summary
Dispersions of grains, bubbles, or droplets in a continuous phase with a different density are unstable in the presence of gravity due to drainage, sedimentation, and creaming. The experiment container presented here provides several features that, combined, distinguish it from previous setups designed to study soft matter samples in microgravity:. 2. Enables the study of dynamic processes inside of opaque materials, such as foams, emulsions, and granular materials, as well as inside of transparent materials by combining light scattering diagnostics with optical microscopy. Slow dynamics accompanied by rare dynamic events arise, for example, in glassy states of hard-sphere colloids, during foam coarsening or when gels and granular media age Details of such processes and the scientific motivation are given in the sections on the sample cell units for the soft matter dynamics experiment A two-stage system is applied to control the temperature of the experiment: the whole sample cell carrier is located inside an isothermal housing and is connected to a water cooling loop provided by the FSL. The details of the sample cell carrier and the diagnostics are described in Subsections II A and II B
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