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Photo-ionization
lamps are compact, rugged, low-pressure gas discharge lamps used in
photo-ionization detectors (PIDs) to measure various volatile organic
compounds (VOCs).
Resonance mass
produces an extensive range of RF excited lamps filled with a variety
of gases. In these lamps, the natural "RESONANCE" frequency of the gas
is excited by plasma in the bulb. Combinations of the appropriate fill
gases and window materials are used to select near monochromatic
energies in the 11.7 to 4.9 eV range. Unique sealing and processing
technologies developed during work for the US and Japanese space
programs yield lamps of exceptionally high stability and output.
Burn-in and VUV testing of every lamp ensures the best quality to meet
customers' requirements throughout the world.
In
a
low-pressure
RF-excited
gas discharge lamp electrons collisionally
excite atoms in the lamp causing them to emit at highly specific
spectral emission wavelengths. These spectral "lines" will
typically appear in all spectral regions down to the short wavelength
cut-off of the window. In Resonance's lamps the presence of
unwanted "impurity lines" is minimized and is typically far less than
0.1 percent. This insures that the species-to-species
photoionization sensitivity of a PID equipped with a Resonance lamp
will not change from lamp to lamp or drift with time.
The
most
commonly
used
lamp for PID purposes is the 10.6, 10.0 eV magnesium
fluoride windowed lamp filled with Krypton. Resonance's lamp has
a hard glass seal allowing high temperature processing, a special low
fluorescence grade of magnesium fluoride with very high VUV
transmission and a high capacity chemical getter. The combined
effect of these advanced construction methods is the production of a
lamp with very high spectral purity and exceptional operational and
shelf life. These lamps are similar in construction to those in
use on the Hubble Space Telescope which meet the requirements of a 10
year mission life in the rigorous thermal environment of space.
During
use
the
lamp
may appear to drop in intensity due to an accumulation of
photo polymerized deposits on the window. These deposits result
from the cross linking of organic compounds to form a thin UV-absorbing
film on the window. These films may be removed by a
methanol wipe with a cotton swab or by a gentle polish with 0.3 micron
aluminum oxide powder. When the window cleanness is maintained
the operational life of the Resonance lamps will exceed 2,000 burning
hours.
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