The department has a laserdiffraction system by Sympatec HELOS which measures particle size distribution (PSD) in the range 0.0018mm-3.5mm.
The laser source is of the He-Ne type and emits red light at 632.8nm.
The instrument is equipped with 3 different lenses (R1, R4, R7) which each has an optimum measuring range. Each lens covers 31 measured particle classes, the number of optional interpolated particle classes is unlimited.
2 modules are available for wet (Quixel) and dry (Vibri/Gradis) material. 2 flow-cells for either 2mm or 6 mm exist for the Quixel module, the flow-cells are steel material with quartz windows.
Data can be evaluated with either Fraunhofer or Mie theory.
Depending on the sample composition, it may be necessary to split the sample into maximum 3 fractions and measure each fraction individually. In the end data can be combined for a PSD covering the entire size range of the sample.
It may be necessary to further prepare the sample before splitting and/or measuring: For marine samples salt may need to be removed. For samples high in organic matter, carbon may need to be removed by an oxidation process using hydrogenperoxide or ignition at 550 degrees of Celcius.
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