Ametek ORTEC MOBIUS-B, User Manual, Page: 18 / 28

PROPERTY OF AMETEK, INC. – ORTEC ®
ORTEC
® MÖBIUS™ Recycler HPGe Detector Cooling System
805709F / 1115
12
follows:
8) Frost will form on the fill and vent tubing, fittings, and other cold surfaces as the LN2 flows. The frost serves
as a warning that these surfaces that are very cold and should not be touched without suitable gloves. It is
not unusual for the valve on the supply dewar to frost over during the fill process, so be sure to have gloves
handy so you can quickly close the supply valve as soon as the MÖBIUS is full. The frost also provides
additional thermal insulation to the lines so do not wipe it off during LN2 transfer.
Note: the fill and vent valves on the MÖBIUS should not be operated (opened or closed) until they are at
room temperature.
9) When the MÖBIUS status display indicates LN2:
100%
, watch the fog exiting the vent tube very closely for
signs of small LN2 droplets first, then large droplets . Immediately close the supply valve as soon as you
observe these droplets, otherwise the MÖBIUS system electronics and seals could incur damage.
10) Leave the fill and vent lines connected until all frost on the lines and fittings has thawed (this typically takes
just a few minutes). Only when all signs of frost are gone can the lines can be removed safely. Cold gaseous
nitrogen will continue to exit the vent as the detector continues to cool. The system should be left
undisturbed overnight to allow the detector and MÖBIUS to completely cool down. During cooldown
leave
the MÖBIUS fill/vent valves open.
11) A warm detector causes a significant amount of LN2 to boil off at first. Once the detector is cold, it is a good
idea to top off the LN2 level in the MÖBIUS. After top-off, remove any attached hoses and close the fill/vent
valves. The system will begin to pressurize as LN2 in the dewar vaporizes. The MÖBIUS will sense this
pressure increase and turn on its cryogenic cooler to begin re-condensing the evaporating LN2. Between PSIG
values of 0 and 0.2 system will indicated
Vented status. Between PSIG values of 0.45 and 0.55 status will
indicate OK status. Between PSIG values of 0.65 and 1.4 status will indicate Cooling status. At first, the cooler
and its cooling fan will run at high power. While cooling, MÖBIUS display should look as follows:
where X should have a value between 0.0 and 1.0 psi. Note: LN2 may indicate value slightly below 100% at
this point. Note: Two safety valves will vent excessive pressure, if pressure exceeds approximately 1 psi.
12) After about 2 hours the system will stabilize so the cooler and its cooling fan are running just at the power
level necessary to maintain a constant pressure of 0.5 psi (3.5 kPa; 104.4 kPa absolute pressure) inside the
MÖBIUS dewar. Once the system is stabilized, power consumption level will vary while pressure is maintained
around 0.5 psi. It is normal for cooler to turn off occasionally when pressure drops below 0.50 psi. A display
example of a pressurized, cooled down MÖBIUS would look as follows: