2 Installation
C
REATE A
S
ORPTION
P
UMP
The VacPrep vacuum can be improved by creating a sorption pump using a sample tube and a
microporous material with a high surface area.
1. Partially fill a sample tube with material of a high surface area, such as aquarium charcoal,
other forms of activated carbon, or zeolite. Avoid using fine powders.
2. Attach the sample tube to one of the degas stations.
3. Set the temperature controller to approximately 150 ºC.
4. Turn the appropriate VAC/GAS control knob to VAC and allow the sample tube to be evac-
uated for approximately one hour or until the vacuum gauge reading falls below 50 millitorr
(50 μmHg).
5. Leave the VAC/GAS control knob in the VAC position and move the sample tube to a cool-
ing station.
6. After the sample tube has cooled sufficiently, immerse the lower two thirds of the tube into a
liquid nitrogen bath.
7. The resulting sorption pump will reduce the pressure in the VacPrep to less than 1 millitorr
(1 μmHg).
8. The vacuum gauge may be recalibrated with the sorption pump attached.
9. Turn the VAC/GAS control knob to GAS for about 30 seconds, then to OFF before removing
the sorption pump from the fitting.
For sample tubes having a capacity greater than 6 cm
3
and for tubes containing high
surface area materials, a longer backfill time will be required.
Do not exceed 5 psi regulator pressure when backfilling sample tubes. If the gas
pressure is greater than the recommended maximum of 5 psig (35 kPag), the sample
tube could be ejected from the fitting or broken.
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VacPrep Operator Manual
061-42802-01 (Rev B) — Apr 2021
