The Reference Detector; The Pmt; Figure 10-3. Source Uv Lamp Construction - Teledyne T101 Operation Manual

Principles Of Operation

10.2.2. THE REFERENCE DETECTOR

10.2.3. THE PMT

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The lamp used in the Model T101 is constructed with a vacuum jacket surrounding a
double-bore lamp element (Figure 10-3). The vacuum jacket isolates the plasma arc
from most external temperature fluctuations. The jacket contains the thermal energy
created by the lamp's operation, thereby helping the lamp heat up and maintains proper
vaporization temperature. Light is emitted through a 20 mm x 5 mm portal.
Vacuum
Jacket
Dual Bore

Figure 10-3. Source UV Lamp Construction

A vacuum diode UV detector that converts UV light to a DC current is used to measure
the intensity of the excitation UV source lamp. Its location, directly across from the
source lamp at the back of a narrow tube-shaped light trap, places it directly in the path
of the excitation UV light. A window transparent to UV light provides an air-proof seal
that prevents ambient gas from contaminating the sample chamber. The shape of the
light trap and the fact that the detector is blind to wavelengths other than UV means no
extra optical filtering is needed.
The amount of fluoresced UV produced in the sample chamber is much less than the
intensity of excitation UV source lamp (see Figure 10-4). Therefore a much more
sensitive device is needed to detect this light with enough resolution to be meaningful.
The Model T101 uses a Photo Multiplier Tube or PMT for this purpose (see 10.4.4 for
more details regarding the electronic operation of the PMT).
Teledyne ML - T101 Operation Manual
Light Output
Portal
Zinc-Vapor
Plasma Arc