DHR/AR Series SALS Accessory Getting Started Guide
Page 18
Aligning the System
The laser in the base and the surface of the Peltier Plate are factory aligned and should not require any
adjustment.
A small amount of adjustment will be necessary to align the upper fixture whenever it is fitted. This is most
easily achieved by using a sample with a known scatter pattern.
The scattering from a random arrangement of spherical particles, with diameters greater than the wave-
length of the incident light, results in series of concentric rings that diminish in intensity as the scattering
angle increases (Mie scattering). Polystyrene micro particles of nominal diameter (3 µm) are suitable for
this purpose, and these can be obtained from Sigma-Aldrich (Fluka), product no. 80304. They are supplied
at a solids content of 2% by weight and should be diluted by a factor of about 200 using purified water to
eliminate multiple scattering.
Follow these steps to adjust the alignment:
1
Turn on the rheometer and start TRIOS Software.
2
Set the temperature of the Peltier Plate to 25°C.
3
Ensure upper geometry and lower plate are clean and free from lint.
4
Zero the gap.
5
Raise the head.
6
Set the focal point to 500 µm by setting the adjustable front lens to 1.35. See the figure below.
Figure 8
SALS front lens.
