Limitations Of Lithium Fluoride Lamp Window; Using The 11.7 Ev Uv Lamp - PerkinElmer Photovac 2020 Manual

2020 is equipped with a standard 10.6 eV UV lamp. An 11.7 eV
UV lamp (Part No. MX390024) available for special applications.
Install this lamp as outlined in Removing and Replacing the UV
Lamp on page 116. When you install a UV lamp other than the
standard 10.6 eV lamp, all the response factors become invalid. You
must set the response factor for the current cal memory to 1.
Contact the Applications Department for further information.
NOTE: Do not use the 11.7 eV lamp in conjunction with the dilution
probe.
Limitations of Lithium Fluoride Lamp
Window
This lamp is intended for special applications only. It is not suitable
for normal operation, due to limitations of the lamp window material.
The 11.7 eV lamp window material is lithium fluoride (LiF). LiF is
composed of two light elements which are easily disrupted within the
crystal lattice by the UV light generated by the lamp. Disruption of
the lattice causes the crystal to turn a yellowish color, and again
performance declines.
Unlike other lamp windows, LiF readily absorbs water from
atmospheric humidity. When contaminated by moisture, the window
loses its ability to transmit UV light. Clean the lamp window as
outlined in Cleaning the Lithium Fluoride Window on page 120.
NOTE: Do not touch the lamp window or handle it near liquid water.

Using the 11.7 eV UV Lamp

With an 11.7 eV lamp installed, your instrument functions as a leak
detector responding to gases and vapors which ionize at 11.7 eV or
less. The 11.7 eV lamp may be useful for detecting leaks of
chemicals not ionized by the standard 10.6 eV lamp.
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Connecting Accessories