Back scatter optics and particle size measurement. (Workshop).
The unique back scatter optics in the recently introduced Malvern HPPS (High Performance Particle Sizer) are making possible the accurate measurement of a range of high concentration samples, such as suspensions and particularly emulsions, without the need for dilution. This is a significant advance since many high concentration systems are sensitive to the disruptive effects of dilution, which rod uce erroneous particle sizing results. Equally, it may be difficult or inconvenient to build in a dilution step.
An example of a highly concentrated system is that of silica particles used in polishing slurries for the semi-conductor industry. Here particle size distribution affects both the substrate removal rate and the surface finish. Typically slurries can contain silica at 20 per cent volume concentration and are opaque. Classical light scattering systems fail to give accurate particle sizing data due mainly to the presence of multiple scattering, whereby light scattered by one particle is rescattered by others before reaching the detector. HPPS back scatter optics minimise multiple scattering by automatically optimising the scattering path length.
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