Static Multiple Light Scattering (SMLS) – How does it work?

With Static Multiple Light Scattering (SMLS), photons (NIR light source, 880 nm) are sent into the sample. After these photons have been scattered several times by the particles (or droplets) in the dispersion, they emerge from the sample and are detected by two synchronous detectors. For opaque samples the backscattering is measured at 135°, for transparent samples the transmission is measured at 0° from the light source.

Backscattering is directly related to the photon transport mean free path (I*). I* (µm) is the distance above which the photon loses the initial direction of the incident beam. The transmission is directly related to the photon mean free path (I), which is the average distance between scatterers. Thus, the transmission and backscattering light intensities both depend on particle size and concentration.

The TURBISCAN technology, employing Static Multiple Light Scattering (SMLS), measures transmission or backscattering intensities versus the sample’s height and aging time. Particle diameter evolution (aggregation, flocculation, coalescence) and concentration change (sedimentation, creaming) can easily be detected and monitored. The particles’ mean diameter can be calculated from backscattering or transmission intensities thanks to the Mie theory using the following equations.