1200 Series DAD and MWD User Manual 13
Introduction to the Detector 1
Optical System Overview
Optical System
The optical system of the detector is shown in Figure 1. Its illumination source
is a combination of a deuterium-arc-discharge lamp for the ultraviolet (UV)
wavelength range and a tungsten lamp for the visible (VIS) and short-wave
near-infrared (SWNIR) wavelength range. The image of the filament of the
tungsten lamp is focused on the discharge aperture of the deuterium lamp by
means of a special rear-access lamp design which allows both light sources to
be optically combined and share a common axis to the source lens. The
achromat (source lens) forms a single, focused beam of light through the flow
cell. Each cell room and lamp are separated by a quartz window which can be
cleaned or replaced. In the spectrograph, light is being dispersed onto the
diode array by a holographic grating. This allows simultaneous access to all
wavelength information
Lamps The light source for the UV-wavelength range is a deuterium lamp with a
shine-through aperture. As a result of plasma discharge in low-pressure
deuterium gas, the lamp emits light over the 190-nm to approximately 800-nm
Figure 1 Optical System of the Detector
Tungsten lamp
Deuterium lamp
Holmium oxide filter
Achromat (source lens)
Flow cell
Slit
Diode arra
Grating
Cell suppo
window
Spectro le
Coupling lens
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