WATERS CORPORATION 2424, Operator'S Manual, Page: 24 / 196

1-10 2424 ELS Detector Optics Principles
Illumination system
The illumination system uses these components to direct broadband light
from the lamp into the light scattering chamber:
• Tungsten halogen lamp
• Entrance mask
• Two convex lenses, L1 and L2, acting as a condenser
• Slit
• Baffle
• Convex relay lens L3
Light scattering chamber
The light scattering chamber is the equivalent of a flow cell in other detectors.
It provides an environment where the sample in the gas stream and the
incident light beam can interact. The chamber contains these components:
• Two light traps
• Reference photodiode
To prevent the solvent and analyte from condensing on the chamber walls or
optical surfaces, the chamber is heated to 50 °C (122 °F) and cannot be varied.
A thermistor for temperature regulation and an over-temperature switch are
included in its heating circuit.
Collections system
The collections system collects scattered light from the scattering chamber
and directs it to the PMT for conversion to an electrical signal. It consists of
these components:
• Snout
• Biconvex collector lens, L4
• Mirror M1
• PMT
Temperature control
To vaporize and evaporate the solvent, the nebulizer and drift tube have
temperature control.