Ametek ORTEC MOBIUS-B, User Manual, Page: 17 / 28

805709F / 1115 ORTEC
® MÖBIUS™ HPGe Detector Cooling System
11
3) If using the split center plug, put the two halves carefully in place before fully lowering the cooling rod
through the bottom of the shield. To avoid ground loops, position the detector high enough inside the shield
that its base plate does not touch the top of the center plug.
4) Finally, the damping materials and spacers can be inserted under the MÖBIUS. It is easiest to have two
helpers lift the MÖBIUS while you slide the spacer stack underneath.
5) Now is a good time to choose a location for the status display and mount it with the hook-and-loop strips
provided with the system. Make sure to position it where the readout is clearly visible (for example, on the
shield table as in Figure 11).
3.2. FILLING WITH LN2
This procedure requires cryoprotective gloves and eye protection.
Note: pressure from the refill dewar should not exceed 22 psi (152 kPa).
1) Before filling the MÖBIUS with LN2, be sure to read all cautions in Section 3.3.
2) For MÖBIUS-B Models, ensure the supplied top plug is secure (see Figure 5) and the detector is properly
installed on the cryostat before filling.
3) The MÖBIUS is now ready for power-up. Connect the mains power cord to a properly grounded electrical
supply and set the power switch to the “On” position. The remote status display will light up and show
LN2:
0%, Pwr: 0%
indicating that the dewar is completely empty and cooler power is off. If dewar is partially filled
then display will show X% depending on the level of LN2 currently in the dewar.
4) With the remote status display clearly visible, open the two fill/vent valves on the front of the dewar
(Figure 2). This will depressurize the system. The status display will now show pressure PSIG: 0.0 and fill level
LN2: 0% (or X% is dewar is partially filled). Display should look as follows:
5) Connect the transfer hose from the supply dewar to the MÖBIUS. Its two fill/vent valves are identical to one
another, hence, interchangeable (i.e., if the supply dewar is connected to the left connection, the right
connection becomes the vent, and vice versa). Although not specifically required for protection of the
MÖBIUS, an exit line can be connected to the vent valve to route gas and liquid that escapes during filling to a
safe location. Suitable transfer and vent hoses are available separately from ORTEC. Pressure from the refill
dewar should be between 5 and 22 psi.
Pressure from the refill dewar should not exceed 22 psi (152 kPa).
6) Open the valve on the supply dewar to start the flow of LN2 into the MÖBIUS. Cold nitrogen gas will
immediately begin blowing out of the vent side and will condense moisture in the air, creating a clearly visible
fog.
If this fog is not observed, turn the supply dewar valve off immediately and ensure that both valves on the
front of the Mobius are open.
7) As the liquid level in the MÖBIUS rises, the liquid nitrogen fill readout on the status display will increase until
the dewar is full and the readout indicates 100%. Fill time depends very much on supply dewar pressure, but
is typically between 10 and 30 minutes for a completely empty MÖBIUS. Once filled, display would look as