Micromeritics 061-00023-00, Руководство оператора

Страница: 20 / 62

Creating a Sorption Pump VacPrep 061
1-14 Feb 2013
Creating a Sorption Pump
You can improve the vacuum in the VacPrep 061 by creating a sorption pump using a sample
tube and a microporous material with a high surface area. The following steps describe how to
create a sorption pump.
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 VACUUM/GAS control knob to VAC and allow the sample tube to
be evacuated for approximately one hour or until the vacuum gauge reading falls below 50
millitorr (50

mHg).
5. Leave the VACUUM/GAS control knob in the VAC position and move the sample tube to
a cooling 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

mHg).
8. The vacuum gauge may be recalibrated with the sorption pump attached.
9. Turn the VACUUM/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.
Backfilling the sample tube increases its pressure to a level greater than atmospheric
pressure. 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.