Backfilling - Princeton Instruments PI-MAX System Manual

216 PI-MAX/PI-MAX2 System Manual Version 5.F
Be wary of unspecified "dry" gases intended for less demanding applications. Even a
WARNING
99.9% pure gas can deposit enough water to cause permanent damage to the detector.
As an example, consider an IVUV camera where the CCD temperature is -20°C and
where you are using nitrogen with 100 ppm of water vapor. This water vapor will be at
dew point and water will condense and freeze on the CCD. Ice will continue to form for
as long as this nitrogen flows over the surface of the CCD.
Princeton Instruments recommends that gases with less than 10 ppm water vapor be used.
An example is AIRCO compressed nitrogen grade 4.8 (3 ppm). Equivalent gases from
other quality vendors are also suitable.
Connect the nitrogen source to the nitrogen inlet on the upper surface of the camera nose.
Purge the detector for at least 10 minutes at a high rate (1-2 liters/minute). Then lower the
rate to 750-1000 ml/minute.
After you have finished an experiment and have turned off the controller, maintain a gas
Caution
flow of at least 2 liters/minute for at least 15 minutes. This keeps condensation from
forming on the detector until it reaches room temperature.

Backfilling

If a sealed version of the IVUV PI-MAX detector must be backfilled, contact the factory
and arrange to return the detector to the factory where it can be properly flushed,
backfilled and resealed again. See page 232 for contact information.
WARNING
Operating a sealed-nose IVUV PI-MAX that is no longer backfilled with dry nitrogen
may result in condensation on the array that could cause irreversible damage. Such
damage would not be covered by the Warranty.