Ametek ORTEC MOBIUS-B User manual

ORTEC®
MÖBIUS Recycler
Condensing Liquid Nitrogen
HPGe Detector Cooling System
User Manual
Printed in U.S.A. ORTEC® Part No. 805709 0514
Manual Revision F
™

PROPERTY OF AMETEK, INC. –ORTEC®
ORTEC®MÖBIUS™ Recycler HPGe Detector Cooling System 805709F / 1115
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Advanced Measurement Technology, Inc.
a/k/a/ ORTEC®, a subsidiary of AMETEK®, Inc.
WARRANTY
ORTEC* warrants that the items will be delivered free from defects in material or workmanship. ORTEC makes no other
warranties, express or implied, and specifically NO WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE.
ORTEC’s exclusive liability is limited to repairing or replacing at ORTEC’s option, items found by ORTEC to be defective in
workmanship or materials within one year from the date of delivery. ORTEC’s liability on any claim of any kind, including
negligence, loss, or damages arising out of, connected with, or from the performance or breach thereof, or from the
manufacture, sale, delivery, resale, repair, or use of any item or services covered by this agreement or purchase order, shall
in no case exceed the price allocable to the item or service furnished or any part thereof that gives rise to the claim. In the
event ORTEC fails to manufacture or deliver items called for in this agreement or purchase order, ORTEC’s exclusive liability
and buyer’s exclusive remedy shall be release of the buyer from the obligation to pay the purchase price. In no event shall
ORTEC be liable for special or consequential damages.
Quality Control
Before being approved for shipment, each ORTEC instrument must pass a stringent set of quality control tests designed to
expose any flaws in materials or workmanship. Permanent records of these tests are maintained for use in warranty repair
and as a source of statistical information for design improvements.
Repair Service
If it becomes necessary to return this instrument for repair, it is essential that Customer Services be contacted in advance of
its return so that a Return Authorization Number can be assigned to the unit. Also, ORTEC must be informed, either in
writing, by telephone [[phone]] or by facsimile transmission [[phone]], of the nature of the fault of the
instrument being returned and of the model, serial, and revision (“Rev” on rear panel) numbers. Failure to do so may cause
unnecessary delays in getting the unit repaired. The ORTEC standard procedure requires that instruments returned for repair
pass the same quality control tests that are used for new-production instruments. Instruments that are returned should be
packed so that they will withstand normal transit handling and must be shipped PREPAID via Air Parcel Post or United Parcel
Service to the designated ORTEC repair center. The address label and the package should include the Return Authorization
Number assigned. Instruments being returned that are damaged in transit due to inadequate packing will be repaired at the
sender's expense, and it will be the sender's responsibility to make claim with the shipper. Instruments not in warranty
should follow the same procedure and ORTEC will provide a quotation.
Damage in Transit
Shipments should be examined immediately upon receipt for evidence of external or concealed damage. The carrier making
delivery should be notified immediately of any such damage, since the carrier is normally liable for damage in shipment.
Packing materials, waybills, and other such documentation should be preserved in order to establish claims. After such
notification to the carrier, please notify ORTEC of the circumstances so that assistance can be provided in making damage
claims and in providing replacement equipment, if necessary.
Copyright ©2014, Advanced Measurement Technology, Inc. All rights reserved.
*ORTEC®is a registered trademark of Advanced Measurement Technology, Inc. All other trademarks used herein are the property of their
respective owners.
NOTICE OF PROPRIETARY PROPERTY —This document and the information contained in it are the proprietary property of AMETEK Inc.,
ORTEC Business Unit. It may not be copied or used in any manner nor may any of the information in or upon it be used for any purpose
without the express written consent of an authorized agent of AMETEK Inc., ORTEC Business Unit.

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TABLE OF CONTENTS
1. INTRODUCTION........................................................................................................................................................... 1
1.1. HOW MÖBIUS WORKS ..................................................................................................................................... 1
1.2. UPS INTEROPERABILITY.................................................................................................................................... 1
1.3. SPECIFICATIONS ............................................................................................................................................... 2
1.3.1. Performance ....................................................................................................................................... 2
1.3.2. Mechanical.......................................................................................................................................... 3
1.3.3. CE ........................................................................................................................................................ 3
1.4. INSPECTION FOR SHIPPING DAMAGE .............................................................................................................. 3
2. SYSTEM OVERVIEW..................................................................................................................................................... 4
2.1. CONTENTS OF THE SHIPPING CARTON............................................................................................................. 4
2.2. THE MÖBIUS..................................................................................................................................................... 4
2.3. PREPARING THE MÖBIUS FOR USE .................................................................................................................. 6
3. INSTALLATION............................................................................................................................................................. 9
3.1. ASSEMBLING THE SYSTEM ............................................................................................................................. 10
3.2. FILLING WITH LN2 .......................................................................................................................................... 11
3.3. SAFETY AND EQUIPMENT WARNINGS ........................................................................................................... 13
3.3.1. Liquid Nitrogen Safety ...................................................................................................................... 13
3.3.2. Other Precautions............................................................................................................................. 14
3.3.2.1. HANDLING POPTOP DETECTOR/CRYOSTAT ASSEMBLIES................................................................ 14
3.3.2.2. ELECTRICAL CAUTIONS............................................................................................................ 14
3.3.2.3. UNINTENDED DETECTOR WARM-UP......................................................................................... 15
4. MAINTENANCE ......................................................................................................................................................... 16
4.1. CLEANING OR REPLACING THE MÖBIUS FILTER ............................................................................................. 16
4.2. EMPTYING AND WARMING THE MÖBIUS ...................................................................................................... 17
4.3. TRANSPORTING OR SHIPPING THE MÖBIUS .................................................................................................. 18
4.4. DETECTOR WARM-UP .................................................................................................................................... 18
4.5. REMOVING THE DETECTOR/CRYOSTAT ASSEMBLY........................................................................................ 18
4.6. DECOUPLING A POPTOP CAPSULE FROM THE CRYOSTAT ............................................................................. 19

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ADDITIONAL WARRANTY AND SAFETY NOTICES
There are no serviceable parts in or on the MÖBIUS except those specified in this manual, e.g., the mains power cord,
fuses, and filter. Opening the rear panel or otherwise accessing the interior components, attempting to detach the
level monitor or remote status display leads, or performing operations other than those described in this manual (e.g.,
inserting/removing the mechanical cooler’s protective foam block, adding/removing liquid nitrogen, and
inserting/withdrawing detector crystostats into/from the dewar) may void your warranty.
Using this equipment in a manner not specified in this manual may impair the protection the equipment provides.
Changes to valving, tubing, or other components of the MÖBIUS system can result in damage to equipment, injury,
or death. Modifications to any system components must be made in consultation with ORTEC technical support
personnel and authorized in writing in advance of such modifications.
SAFETY INSTRUCTIONS AND SYMBOLS
This manual contains up to three levels of safety instructions that must be observed in order to avoid personal injury
and/or damage to equipment or other property. These are:
DANGER Indicates a hazard that could result in death or serious bodily harm if the safety instruction is not
observed.
WARNING Indicates a hazard that could result in bodily harm if the safety instruction is not observed.
CAUTION Indicates a hazard that could result in property damage if the safety instruction is not observed.
Please read all safety instructions carefully and make sure you understand them fully before attempting to use this
product.
In addition, the following symbol might appear on the product:
ATTENTION –Consult the manual in all cases where this symbol is marked in order to
determine the nature of the potential hazards and any actions that must be taken to avoid
them
DANGER –Hazardous voltage
Protective earth (ground) terminal
Please read all safety instructions carefully and make sure you understand them fully before attempting to use this
product.

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MÖBIUS-B w/ HJ-style cryostat
MÖBIUS-B w/ PopTop® cryostat
MÖBIUS w/ PopTop® cryostat

1
ORTEC MÖBIUS™RECYCLER
CONDENSING LIQUID NITROGEN HPGE DETECTOR COOLING SYSTEM
1. INTRODUCTION
The ORTEC MÖBIUS Recycler integrates a Sunpower® CryoTel® Stirling-cycle cryocooler with a specially designed
28 liter liquid nitrogen (LN2) dewar to yield a high-reliability HPGe detector cooling system. This is especially useful for
counting laboratories that have periodic power failures. The MÖBIUS fits easily under standard lead shields with the
same footprint as a regular dewar. The remote status display can be mounted outside the lead shield for easy
visibility.
A continuously operating MÖBIUS requires refilling only once every two (2) years —a major savings in worry, time,
money, and exposure to LN2 handling risks. During a power failure, the MÖBIUS performs as a standard dewar. After
power is restored, check the LN2 level and top it off if necessary —that’s all it takes to return the system to maximum
performance.
The MÖBIUS supports our Streamline and PopTop® detector lines, and horizontal as well as vertical dipstick-type
cryostats. In addition, a number of non-ORTEC cryostats and detectors are supported; contact your ORTEC
representative for more information. If you have purchased a detector in addition to a MÖBIUS, all detector-specific
information is included in the detector’s data sheet and user manual.
1.1. HOW MÖBIUS WORKS
The MÖBIUS has a computer-controlled pressure system that maintains a
constant and stable 0.5 psi (3.5 kPa) in the vapor space of the dewar. A
pressure transducer feeds the pressure in the dewar to the onboard
computer, which controls the rate at which the Sunpower cryocooler re-
condenses the nitrogen vapor to liquid. The cryocooler operates only when a
cryostat is installed and the two fill/vent valves are closed (i.e., when the
system is pressurized). This evaporation/re-condensation process is
illustrated in Figure 1.
The fill collar has redundant pressure relief valves designed to open if the
pressure exceeds 1 psi (6.9 kPa). In the event of power loss the cryocooler
stops, the pressure inside the vapor space starts increasing, and nitrogen
vapor slowly begins escaping into the atmosphere via the pressure relief
valves. However, if power remains on and the system is operating in an
uninterrupted steady state, there is no LN2 loss and the system can operate
indefinitely without an LN2 refill.
The LN2 level monitor calculates the level of liquid nitrogen in the dewar,
giving you ample opportunity to schedule maintenance.
1.2. UPS INTEROPERABILITY
The MÖBIUS is designed to run on ac mains power. However, during a power
failure it acts as a conventional dewar and can keep a detector cold for
200 hours or more, depending on the level of LN2 in the dewar. When power is restored, the unit’s cryocooler restarts
and it resumes recycling nitrogen gas boil-off as before.
Figure 1.

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The unit can be connected to an uninterruptable power supply (UPS) to sustain operation during short-duration power
failures. Fully cooled, it draws about 150 watts of power from a UPS without a “smart” capability. Alternatively, the
MÖBIUS can run off of a “smart” UPS with a dry contact relay interface, such as the APC SMT750 UPS equipped with
their optional AP9613 dry contact management card. In this configuration, if power fails the UPS signals the MÖBIUS
to enter its power-saving mode to conserve UPS battery life. The cryocooler turns off, reducing power consumption to
less than 10 watts, while the remote status display continues to provide all status readouts including the liquid
nitrogen level in the dewar.
1.3. SPECIFICATIONS
1.3.1. Performance
●Refill Period After the detector is cool and the LN2 is topped off, the MÖBIUS system can run for 2 years or
longer without filling. This is based on the sealing technology and assumes system operation in
uninterrupted, steady-state conditions.
●Maintenance Wash or replace inlet air filter every 3 months (replacements available from ORTEC). No other
maintenance is required.
●Remote Status Display Readout unit with hardwired umbilical cord can be remotely mounted to improve
visibility when the detector is placed in a lead shield. The display registers the liquid nitrogen level in the
dewar, power level being supplied to the cooler, pressure level within dewar and general status of the
system.
●Internal Controller Control electronics, power supply, and cooler electrically isolated from the dewar and
protected from LN2 spillage.
●LN2 Level Sensing Capacitance level sensor provides continuous measurement of the LN2 level from
0–100% full.
●Use with UPS The MÖBIUS has a small onboard computer that can receive an input, via the rear-panel I/O
connector, in the event of power loss. The input causes the system to enter power saving mode and turn off
the cryocooler. With the cryocooler turned off, the onboard computer can be powered by a small UPS.
●LN2 Loss Rate Approximately 3 L/day with non-PopTop cryostats when cooler is off (same as for
conventional dewar); loss rate will vary depending on ambient conditions and detector size. With PopTop
cryostat typical consumption can be as high as 4L/day when cooler is off.
●Spectroscopic Performance
For new ORTEC detectors purchased with the MÖBIUS: at energies above 15 keV we certify no
degradation of the detector resolution warranted on the detector data sheet, and below 15 keV, less
than 10% of the warranted resolution.
For existing ORTEC detectors in dipstick cryostats, where the MÖBIUS replaces an existing dewar or X-
Cooler®, resolution degradation is based on the existing detector performance. It is expected that the
detector will have similar performance compared to using a standard LN2 dewar. Some degradation
may occur depending on the detector's age and configuration. Note: Detector in a PopTop cryostat
requires a 1.50 inch in diameter dipstick when converting from X-Cooler® to MÖBIUS.
MÖBIUS can be used with existing non-ORTEC detectors in dipstick cryostats having 1.25 or 1.50 inch
diameter. It is expected that the detector will have similar performance compared to using a standard
LN2 dewar. Some degradation may occur depending on the detector's age and configuration.

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1.3.2. Mechanical
●Dewar Capacity 28 L, excluding detector dipstick volume.
●Cooler AMETEK SUNPOWER with passive vibration dampening.
●Auxiliary Cooling Internal fan.
●Audible Noise Less than 60 dB (A) at 1 m fully operational, below 30°C ambient.
●Electrical Supply 100–240 V ac, 50 Hz or 60 Hz.
●Normal Power Consumption 125 W typical, 350 W maximum.
●Dimensions (excluding HPGe detector) 25.8 in. H x 17.2 in. Diam (65.4 cm x 43.7 cm).
●Operating Temperature 0–40°C, 20–90% relative humidity, non-condensing.
1.3.3. CE
●Intended for indoor use.
●Intended for altitude up to 2000 m (6562 ft).
●Mains supply voltage fluctuations up to +/-10% of the nominal voltage.
●Transient overvoltages up to the levels of overvoltage category II.
●Pollution degree 2.
1.4. INSPECTION FOR SHIPPING DAMAGE
If the shipping carton(s) arrives with externally visible damage, do not unpack it. Notify the carrier and make
arrangements to file a damage claim. In all cases of shipping damage, it is the customer's responsibility to file a
damage claim.
If, during unpacking, you find concealed damage, notify the carrier and file a claim. Be sure to save all packing
materials, waybills, and other such documentation to establish claims.
Contact our Global Service Center or your ORTEC representative for further instructions.

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2. SYSTEM OVERVIEW
2.1. CONTENTS OF THE SHIPPING CARTON
1
When you receive the MÖBIUS, its shipping carton(s) will contain the following components at minimum:
●MÖBIUS cryocooler/dewar main assembly with integrated LN2 fill collar, hardwired remote status display,
and adhesive-backed hook-and-loop strip for attachment of remote display.
●Universal power cord kit (contains a universal ac mains power cord and a set of region-specific outlet).
●Fuse kit (contains fuse block and fuses; use the 250 V/10 A time-delay [slo-blo] fuses for 120 V ac mains
power, and the 250 V/5 A time-delay [slo-blo] fuses for 220 V ac mains power).
●Acoustic damping foam shim pack with plywood platform and anti-vibration pad.
●User manual and documentation package.
Options will typically be packaged separately and will include their own instructions.
2.2. THE MÖBIUS
Figure 2 through Figure 5 illustrate the main features of the MÖBIUS.
Figure 2. MÖBIUS Top Panel Features (1).
1
All system components and specifications subject to change without notice.

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Figure 3. MÖBIUS Top Panel Features (2).
Figure 4. Rear Panel Features.

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Figure 5. Top Plug for MÖBIUS-B Models Only.
2.3. PREPARING THE MÖBIUS FOR USE
1) Unpack the dewar and make sure the dewar and vent/fill valve tube stems are empty of any packing material.
2) As shipped from the factory, the cryogenic cooler is protected from damage by a foam block inserted under
the black cooler cover beside the fill collar (Figure 6). This foam must be removed before using the MÖBIUS.
Using a #1 Phillips screwdriver, remove the screws from the cooler cover and set them aside.
Lift off the cooler cover, then remove the caution tag.
Remove the foam block and keep it with along with all other shipping materials for transporting the
MÖBIUS, returning it to the factory for service, etc.
Replace the cover and tighten the screws just enough that they will not vibrate loose. Do not over-
tighten. This seal is intended as an air dam, not a pressure seal, so tighten the screws just enough to
establish uniform, snug contact with the gasket.
3) Next, the fuses must be installed. As shipped, the fuse block and fuses are packaged in zippered plastic bags
so you can select the proper fuse for the ac mains power at your site. Use the 250 V/10 A time-delay fuses for
120 V ac/60 Hz operation and the 250 V/5 A time-delay fuses for 220 V ac/50 Hz operation. Install the fuses in
the block, turn the block until the key tab faces down (Figure 7), and push it into the power entry module
until both sides snap positively into place (Figure 8).
CAUTION When the foam block is not in place under the cooler cover, keep the MÖBIUS upright
or the cooler may be damaged. See also Section 4.3.
Do not operate the MÖBIUS without the cover installed; it is required for proper air flow
to the cooler.

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Figure 6. Remove Protective Foam Block and Caution Tag Under Cooler Cover and Keep for Future Use.
Figure 7. Underside of Fuse Block is Keyed.
Figure 8. Insert Keyed Side Down, Snap
Both Sides Into Place.

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4) The universal power cord adapts for almost any mains power configuration. Simply choose the plug that
matches your outlet (Figure 9) and press it onto the power cord. The other end is a standard female IEC
connector that plugs into the MÖBIUS power entry module.
Figure 9. Select the Plug That Matches Your Outlet.

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3. INSTALLATION
Installation requires at least two people (better
still, three) and a step-stool. Specific shield config-
urations call for specific installation methods.
However, installing the MÖBIUS is essentially no
different than installing a standard 30 L dewar
because the two are very similar in size. The
detector/cryostat assembly should be dry and
warm and the MÖBIUS empty.
The mounting surface must be flat and horizontal.
The shield and/or MÖBIUS must not be positioned
so that it is difficult to disconnect the MÖBIUS
from the electrical supply. Orient the dewar so its
ventilation openings and filter are not blocked.
Figure 10 is an exploded diagram of a typical
spectroscopy system with a PopTop detector, PV4
vertical dipstick cryostat, Model HPLBS shield with
split center plug, and MÖBIUS.
Figure 11 shows a typical MÖBIUS installation
under an HPLBS shield. Setting the detector height
involves the interplay of shield height (adjustment
typically requires a hydraulic jack and wrench), the
thickness of acoustic damping material and/or
other spacers under the dewar, and the insertion
depth of the cryostat cooling rod in the dewar.
Note the arrangement of damping and spacer
materials under the dewar necessary to bring it to
the correct height. Various thicknesses of foam
are used on the bottom (i.e., contacting the floor).
The foam is followed by the plywood spacer, and
the anti-vibration pad is on top. Order is important
for the various spacers: Foam on the bottom,
followed by the plywood, followed by the anti-
vibration mat.
For installations where there is not enough room
for all three layers, omit the foam first, then the
plywood, then the anti-vibration mat as a last
resort.
The detector can also be raised by adjusting the
collar position on the cryostat. This is useful when
using a center plug to reduce floor shine. Note
however that this adjustment lifts the cryostat
cooling rod out of the LN2 column, reducing the
effective capacity of the dewar. In such cases, the
detector begins to warm as soon as the LN2 level
Figure 10.

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falls below the cold tip rather than when the dewar is empty. One solution for this problem is to use a cooling rod
extender such as the ORTEC Model CRE-1, which adds up 4 inches of cold tip to the cryostat.
Figure 11. The MÖBIUS Installed on Foam, Plywood, and Anti-Vibration Pad.
3.1. ASSEMBLING THE SYSTEM
1) Before installation, you may wish to assemble the the spacers, damping materials, MÖBIUS, and
detector/cryostat assembly beside the shield to make preliminary height estimates, cryostat and shield
height adjustments, etc. Otherwise, place the MÖBIUS under the shield first with no spacers under it
2) Holding the detector/cryostat assembly by the preamplifier shroud or under the detector capsule base, lower
the cooling rod through the bottom of the shield —feeding the detector cabling through first —and through
the fill collar into the dewar.
CAUTION Keep the cabling and connectors from being pinched, kinked, deformed, or otherwise
damaged as they and the cooling rod pass through the bottom of the shield.

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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

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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:

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13) At this point, the MÖBIUS is a closed system that is designed to contain all nitrogen vapor. You are now ready
to connect the detector cable to the detector and multichannel buffer.
NOTE: Mobius is designed to operate without liquid nitrogen refilling for up to two years under normal,
continuous operating conditions (e.g. no power loss). The display will blink when the LN2 levels drops below
85%. This value was established to alert the user that the LN2 level in the Mobius is not sufficient to provide
cooling for a full seven days upon an extended power outage.
3.3. SAFETY AND EQUIPMENT WARNINGS
3.3.1. Liquid Nitrogen Safety
Before filling the MÖBIUS, be sure to read the following LN2 advisories as well as the information in Section 3.3.2.
DANGER
●The large expansion ratio of LN2 from liquid to gas (1 to 692) can generate high pressures if the dewar does
not have adequate venting or pressure relief provisions.
●When filling the MÖBIUS, you may be tempted to use dry nitrogen gas to pressurize the supply dewar. ORTEC
STRONGLY RECOMMENDS AGAINST THIS PRACTICE.Instead, only the self-generated pressure of the supply
dewar should be used. Compressed gases (even purportedly dry “house” nitrogen) may contain moisture, oil,
and oxygen. Any oxygen will liquefy at LN2 temperatures (77 K), creating an explosion hazard. In addition,
the moisture and oil can freeze, making the safety valves inoperable. Use a pressure relief of 22 psi
(152 kPa) on the supply dewar to avoid over-pressurization in the event of ice blockage. A blockage can
rupture the dewar and/or expel the detector/cryostat with explosive force.
If the MÖBIUS dewar becomes contaminated with oil, the unit must be returned to ORTEC for service.
Do not use a degreaser or attempt any other remediation unless authorized to do so by our ORTEC
Global Service Center.
If water accumulates in the dewar, remove the LN2; obtain a cylinder of high-purity, oil-free, dry
nitrogen gas (not “house” nitrogen); and stream the gas at very low pressure through the dewar until all
water has evaporated.
●Piping or transfer lines should always be constructed so as to avoid trapping LN2 in the line. Evaporation can
result in pressure buildup and eventual explosion of the line. If all lines cannot be emptied, install safety relief
valves and rupture discs. Also keep in mind that some materials become brittle and fracture when exposed to
LN2 temperatures. For advice on selecting materials for use in storing and transferring LN2, contact ORTEC or
your LN2 supplier. Other sources of information include the CRC Handbook of Laboratory Safety and the
American Society of Mechanical Engineers’ Boiler and Pressure Vessel Code, Section VIII.
●Nitrogen gas can pose an asphyxiation hazard by displacing air. Transfer LN2 only in a well-ventilated area.
Vent storage containers to a well-ventilated area or to the outside to avoid buildup of nitrogen gas in the
work area.
WARNING
●On contact with skin, LN2 causes burns similar to thermal burns or frostbite. Eyes are especially vulnerable to
this type of exposure. Avoid wearing anything capable of trapping or holding spilled liquid nitrogen close to
your skin (for instance, mesh-top running shoes). An impervious apron or coat, cuffless trousers, and high-
topped shoes are recommended. Wear safety glasses or, better yet, full-face protection. Remove all watches,
rings, bracelets, or other jewelry. When gloves are used to handle containers or cold metal parts, they should
be impervious and sufficiently large to be easily tossed off the hand in case of a spill.
●Before removing a detector/cryostat assembly from a MÖBIUS, always vent the system by opening both the
fill and vent valves (Figure 2). Failure to do so may result in the entire contents of the dewar spewing

PROPERTY OF AMETEK, INC. –ORTEC®
ORTEC®MÖBIUS™ Recycler HPGe Detector Cooling System 805709F / 1115
14
dangerously out of the fill collar as the cryostat is removed. Redundant relief valves on the MÖBIUS fill collar
reduce this risk, but it is always best to eliminate the risk by first opening the fill and vent lines.
CAUTION
●The detector electronics must be protected from excessive cold.Avoid spilling LN2 on the cryostat or
electronics, and vent cold gas away from the system being filled. A cold detector must not be enclosed in any
thermally insulating materials at any time.Following these precautions will prevent damage to the vacuum
seals or system electronics from excessive chilling.
●Never attempt to fill the MÖBIUS by manually pouring LN2 through the fill collar. Always install the detector
before filling, and use a fill dewar.The recommended filling procedure described in Section 3.2 presents
minimal risk to the unit and users.
3.3.2. Other Precautions
3.3.2.1. HANDLING POPTOP DETECTOR/CRYOSTAT ASSEMBLIES
●Grasp the assembly just beneath the base of the detector capsule, where the cable exits the base plate; or by
the preamplifier shroud (see Figure 12). Do not touch any cryogenically cooled surfaces (if moving a cryostat
that is already cold), and do not hold the detector by the endcap!
Figure 12. Where To Hold a PopTop.
●If the detector is cold, at the same time you lift or lower the assembly, turn it slightly clockwise (as viewed
from above the endcap; i.e., turn it in the direction that tightens the PopTop capsule to the cryostat).
Applying counterclockwise force to a cold detector will rupture the capsule’s vacuum seal, and the unit
must be returned to ORTEC for repair.
3.3.2.2. ELECTRICAL CAUTIONS
●Ensure the unit is fused for the proper voltage —250 V/10 A time-delay fuses for 120 V ac systems and
250 V/5 A time-delay fuses for 220 V ac systems —before connecting the power cord to ac mains power.
Replace blown fuses with the same model and performance specifications. Never short circuit a blown fuse.
●Always disconnect the power cord from the MÖBIUS before performing any maintenance.