Magnetic Property
Measurement System

Hardware Reference Manual

Quantum Design
San Diego, CA

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CE

Safety Instructions
No Operator Serviceable parts
are inside, refer servicing to_g_ualified__r_ersonnel

For continued protection against fire
hazard, replace fuses only with same typeand rating of fuses for selected line volt~e

As you use your system, observe the following safety guidelines:•

To avoid damaging your system, be sure to verify that your system power requirements match thealternating current (AC) power available at your location. If your system has not been configured forthe correct power available at your location contact your local service representative prior toproceeding with the system installation.

•

To prevent electrical shock, assure the equipment is properly grounded using 3 wire grounded plugs.

•

To prevent electrical shock, unplug the system prior to performing installation, adjustment or servicing.

•

Do not spill food or liquids on the system or its cables.

•

Refer to the section titled "Safety" prior to installing or operating this system. Direct contact with thecryogen liquids, surfaces and materials recently removed from these liquids, or exposure to the boil-off
gas can freeze skin or eye almost instantly causing serious injuries similar to frostbite or burns.

•

When handling cryogenic liquids wear protective clothing including insulated gloves and safety eye
protection.

•

Transfer liquid helium only in areas that have adequate ventilation and a supply of fresh air. Heliumgas can displace the air in a confined space or room, resulting in asphyxiation, dizziness,
unconsciousness or death.

•

Keep this system away from radiators and heat sources. Provide for adequate ventilation to allow forcooling around the cabinet and computer equipment.

•

Refer to the computer and monitor operators manuals for additional safety warnings and notices prior
to operating the system.

Regulatory Information•

This apparatus has been tested to the requirements of the EMC Directive 89/336/EEC.

•This apparatus meets the requirement for: ISM Group 1, Class A equipment per EN 50011:1991(Industrial Environment)

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Table of Contents

List of Figures .. :.............................................................................................................. iv
List of Tables .................................................................................................................. iv
Chapter One:

Introduction

1.1

The Physical Components ................................................................................. 1-1

1.2

The Functional Components .............................................................................. 1-6

1.3

The Working Environment ................................................................................. 1-8

1.4

Unpacking And Initial Setup ............................................................................ 1-1 O
1.4.1 Uncrate the Dewar ................................................................................ 1-11
1.4.2 Uncrate the Control Console ................................................................. 1-11
1.4.3 Uncrate the Vacuum Pump ................................................................... 1-12
1.4.4 Uncrate the MPMS Probe ..................................................................... 1-13
1.4.5 Uncrate the Sample Transport .............................................................. 1-13

1.5

Safety .... :.......................................................................................................... 1-15
1.5.1 Cryogenic Safety ................................................................................... 1-15
1.5.2 Magnet Safety ....................................................................................... 1-15
1.5.3 Electric Safety ....................................................................................... 1-17

1.6

Contacting an Authorized Quantum Design Representative ........................... 1-18

Chapter Two:

The Liquid Helium System

2.1

The MPMS Dewar And Helium Level Monitor.................................................... 2-1

2.2

Safe Handling of Liquid Cryogens ..................................................................... 2-3

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Chapter Three: Cool Down Procedure
3.1

Initial Cooldown .................................................................................................3-1

3.2

The Initial Transfer.............................................................................................3-1

3.3

Subsequent Transfers ........................................................................................3-2

Chapter Four:MPMS Temperature Control System

4.1

Physical Configuration .......................................................................................4-1
4.1.1 Description ..............................................................................................4-1
4.1.2 Low-Power Control Mode ........................................................................4-3

4.2

States of The Temperature Control System ...................................................... 4-4

4.3

Stable Temperature Control Above The Crossover. .......................................... 4-6

4.4High Speed Cooling Mode .................................................................................4-7

4.5

High Speed Warming Mode ...............................................................................4-9

4.6

Stable Temperature Control Below The Crossover ......................................... 4-10

4.7

Refilling The Liquid Reservoir ......................................................................... 4-12

4.8

Configuration of the 1802 RIG Bridge ............................................................ .4-14

Chapter Five:

Sample Handling System

5.1

Sample Support Assembly ................................................................................. 5-1
5.1.1 Slide-seal Assembly ................................................................................ 5-1
5.1.2 Clamp Assembly .....................................................................................5-3
5.1.3 Sample Rod ............................................................................................5-3
5.1.4 Mounting Samples ..................................................................................5-4

5.2

Taking A Measurement ......................................................................................5-6
5.2.1 Installing the Sample Rod Assembly into the Sample Chamber ............. 5-6
5.2.2 Center the Sample .................................................................................. 5-8
5.2.3 Take Measurements ...............................................................................5-8

5.3

Retrieving Samples And Cleaning The Sample Chamber ................................. 5-9

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Table of Contents
Chapter Six:

iii

MPMS Magnetic Field Control

6.1

Changing the Field ............................................................................................ 6-1

6.2

Oscillate Mode ...................................................................................................6-4

6.3

No Overshoot Mode .............·..............................................................................6-5

6.4

High and Low Resolution Mode .........................................................................6-6

6.5

Updating the Last Magnetic Field Stored in the Magnet.. .................................. 6-7

6.6

Direct Control over the Magnet Sequence ......................................................... 6-8

6.7

Magnetic Field Limitations as a Function of the Helium Level ........................... 6-8

Chapter Seven: Gas Control System
7.1

Description .........................................................................................................7-1

7.2

Purging the Airlock ............................................................................................7-3

7.3

Attaching an External Helium Source ................................................................7-4

7.4

The Check Valve ...............................................................................................7-4

7.5

Attaching a Helium Recovery System ................................................................ 7-4

Chapter Eight:

SQUID Detection System

8. 1

Description .........................................................................................................8-1

8.2

Transverse Coil Set ...........................................................................................8-3

8.3

Extended Dynamic Range ................................................................................. 8-5

Chapter Nine:
9.1

Description .........................................................................................................9-1

Chapter Ten:
10.1

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Manual Insertion Utility Probe

Description ....................................................................................................... 10-1

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iv
List of Figures

Figure 1-1
Figure 1-2
Figure 1-3
Figure 1-4

MPMS System Components ................................................................... 1-2
MPMS Probe .......................................................................................... 1-3
MPMS Magnet ........................................................................................ 1-4
MPMS Functional Control Diagram ........................................................ 1-7

Figure 2-1

MPMS Helium Levels ............................................................................. 2-2

Figure 4-1

MPMS Temperature Control Module ...................................................... 4-2

Figure 5-1

The Sample Support Assembly .............................................................. 5-2

Figure 6-1

MPMS Magnet Controls .......................................................................... 6-2

Figure 7-1

MPMS Gas Control System .................................................................... 7-2

Figure 8-1
Figure 8-2

Longitudinal SQUID System ................................................................... 8-2
Transverse SQUID System .................................................................... 8-4

List of Tables

Table 8-1

SQUID Ranges ....................................................................................... 8-5

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1-1

Chapter One:

Introduction

The Quantum Design Magnetic Property Measurement System (MPMS) is a sophisticatedanalytical instrument configured specifically for the study of the magnetic properties of small
experimental samples over a broad range of temperatures and magnetic fields. The system
hardware has two major components: (1) the MPMS dewar and probe assembly, and (2) the
associated control system in the MPMS control console (Figures 1-1, 1-2, 1-3). Automatic
control and data collection are provided by an HP computer and two independent subsystem
controllers (Model 1802 and Model 1822). Most of the gas control and other ancillary functionsin the system are also automated.
The cryogenic probe integrates a 5.5 tesla (1 tesla for MPMS 2) superconducting magnet with a
SQUID detection system and a high-performance temperature control system to provide rapid
precision measurements over a temperature range of 1.9 to 400 Kelvin (4.5 to 350 Kelvin for
MPMS 2). The modular design of the system also allows the probe to be easily refit for additional
options, or disassembled for repair.

1.1 The Physical Components
When installed, two cabinets plus the HP computer comprise the complete MPMS system,
occupying an area approximately 1.5 meters by 3 meters. The system has five major physicalcomponents as follows:1.

The HP computer with the installed MPMS control system software. This unit
communicates with the two MPMS subsystem controllers via the IEEE-488 Bus
Interface protocol (typically referred to as the General Purpose Interface Bus (GPIB)).

2.

The electronic control console is comprised of the 1822 MPMS controller, the 1802
RIG bridge, the MPMS gas control system and vacuum pump, the superconducting
magnet power supply, and the microstepping sample transport controller.

3.

The liquid helium dewar mounted in its cabinet.

4.

The MPMS cryogenic probe which includes the Temperature Control Module (TCM)
integrated with the MPMS superconducting magnet and SQUID detection system.

5.

The sample transport mechanism which mounts on the top of the TCM, and threesample rod assemblies for mounting samples.

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MPMS SYSTEM COMPONENTSSYSTEM COMPONENTS
1. Sample Rod
2. Sample Rotator
3. Sample Transport
4. Probe
5. Helium Level Sensor

6.
7.
8.
9.
10.
11.
12.
13.

Superconducting Solenoid
Flow impedance
SQUID Capsule
Dewar Cabinet
Dewar
HP Thinkjet PrinterMagnet Power supply
Model 1802 Digital
R/G Bridge

14.
15.
1 6.
17.

Console Cabinet
Power Distribution Unit
Model 1822 MPMS Controller
Gas/Magnet Contra-I Unit
170. External Gos
Service Port
17b. Toggle Valve
18. Hp Vectra Computer
19. Monitor
20. Vacuum Pump

11

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Figure 1-1 MPMS System Components

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0Chapter One:

1-3

Introduction

A------

6. 4cf17

B---~""""

6.4C~

c

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E

A

Upper Limit of Vertical Translator Movement
Center of Translator Movement
C
Lower Limit of Translator Movement
D
Top of Sensing Coils
E
Center of Sensing Coils
F
Bottom of Sensing CoilsG
Bottom of Dewar Top Plate
H . Top of Dewar Belly
I . Top of Superconducting Solenoid
J
Bottom of superconducting SolenoidK
Top of SQUID Housing
L . Lowest Point of the Plate

B

K

L

FILE: D014002A

Figure 1-2 MPMS Probe

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Quantum Design
Sample Chamber Tube

MPMS Hardware Reference ManualSample Space
Isa-Thermal Sheet with Heater

Inner Vacuum Jacket Wall

Annular Cooling Region
Superinsulation

Outer Vacuum Jacket Wall

Som pie

Sensing Coils(on composite form)

Multifilament
Superconducting
Wire

Tube Guides

Composite Form
For Solenoid

FILE: D014003A

Figure 1-3 MPMS Magnet

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Chapter One:

Introduction

1-5

The cables connecting the MPMS probe and sample transport to the control cabinet are color
coded for convenience. Note that the two gas lines are different sizes and should be·connected with the ninety degree elbow at the control console.
The HP computer should be connected to the Thinkjet printer and to the MPMS consolewith the two GPIB cable provided. The GPIB cable connecting the 1802 and 1822
controllers is installed at the Quantum Design.
While the components are easily assembled during installation, the installation will normallybe performed by Quantum Design service representatives. This also provides the opportunity
for user training and an opportunity to discuss some of the measurement techniques we havedeveloped. The initial installation, setup, and testing procedures are discussed in more detailin section 1.4.

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1.2 The Functional Components
When configured for magnetic susceptibility measurements, the MPMS integrates sevenmajor functional systems under the MPMS control software. These are as follows:
1.

The Temperature Control Module (TCM) which provides an actively regulated,precision thermal environment over its entire range of operation, 1.9 to 400 K (4.5 to350 K for MPMS2)

2.

The superconducting magnet system which provides reversible field operation to plus
and minus 5 .5 tesla ( 1 tesla for MPMS 2) using an oscillatory technique to minimize
magnet drift immediately following field changes.

3.

The SQUID detector system which includes the Model 2000 SQUID Amplifier control
electronics, sensing pick-up loops, and specially designed filtering with full computer
control via the HP interface computer.

4.

The sample handling system (sample translator and sample transport) which allows
automatic sample measurements and position calibrations using a microstepping
controller having a positioning resolution of .0003 cm.

5.

The gas handling system which provides gas flow control for temperature regulation,
flushing, and cleaning procedures.

6.

Liquid helium system which provides refrigeration for the superconducting detection
system and magnet, as well as providing for operation down to 1.9 Kelvin.

7.

The computer control system which includes the HP computer with a hard disk, a 3.5
inch microfloppy drive, an HP Thinkjet printer, and the integrated MPMS control
system operating software.

These systems are discussed in detail in the following sections of this manual. Figure 1-4,
that shows the functional relationships for the MPMS control system, illustrates control paths
and interactions of various system components. Most of the details of the control system
shown in Figure 1-4 will be invisible to those who operate the system through the Quantum
Design supplied MPMS software operating system. Nonetheless, we recommend that you
become reasonably familiar with this functional structure to better understand the detailed
discussions in this manual that describe both the individual systems and the interactions
between the various systems.

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Chapter One:

Introduction

MPMS FUNCTIONAL CONTROL DIAGRAM
Hp Computer

IEEE488 Interface

1822-MPMS
Computerf-------------i

Airblock
Flushing

VacuumPump

SampleTranslation

Coupling
Transformer
HeaterSQUID
Control

SompleTransport
Assembly

SQUID
Coupling
Transformer

SQUID
Sensor

Gos Control
Panel

Proportionol
Gas Flow

Magnet Power
SupplySQUID
Detector
Array

Figure 1- 4 MPMS Functional Control Diagram

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Gos/Heater
Switch1802 R/G Bridge

Temperature
SensorMagnetPersistent
SwitchMagnetFlow
Impedance
HeaterGas Heater

Helium Level
Detector

Dewar
SystemFile: D014004A

1-7

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MPMS Hardware Reference Manual

1.3 The Working Environment
The MPMS system; comprising the control console, dewar cabinet, and HP computer;requires a lab space about 1.5 meters by 3 meters. It should be positioned two to three feetfrom any wall to allow reasonable access to the rear of the unit. In addition, the dewar
cabinet should be conveniently accessible from the front and one side to facilitate sample
insertion/removal and transferring of liquid helium. Ready access to the system for liquid
helium storage dewars is essential since the MPMS dewar must be refilled with helium on a
weekly basis, every 5 to 7 days. The MPMS dewar has a capacity of 56 liters, with helium
consumption ranging from about 4.5 liters/day when operating the system at low
temperatures and up to 6 to 7 liters/day when operating at room temperature. The dewar isshock mounted in its enclosure, so that no special vibration isolation is required in normal
laboratory environments.
The HP computer can either sit on top of the control console or on a nearby desk. The twometer GPIB cable supplied with the system can be replaced with a cable up to four meters
long if desired. The MPMS control console is connected to the probe in the dewar cabinetby two flexible metal vacuum lines bundled with several multi-conductor electrical cables.
After the cables and vacuum lines are installed, the two cabinets should be separated as far
apart as possible without straining either the electrical cables or vacuum lines. Since thecontrol console contains a mechanical pump and other ferrous materials, the separation
prevents magnetic signals (especially from the vacuum pump) from interfering with the
SQUID detection system.
A three meter (ten feet) ceiling height is also required to allow sample insertion and liquid
helium transfers. The sample carrier, which is a rigid tube slightly less than 1.2 meters inlength, must be inserted into the top of the MPMS probe. A 3 meter ceiling provides theclearance needed to avoid bending the sample rod. Since minimal lateral clearance isrequired, removing a ceiling tile in a dropped-ceiling often provides the requisite ceilingheight.
During operation the MPMS power requirement is 15 amps at 110 V AC, single-phase. (Theunit can also be configured for 220 volt service at 7.5 amps.) The control console is suppliedwith a single eight-foot power cord that plugs into a receptacle at the rear of the control
console; three additional AC receptacles are required for the HP computer, its monitor, andthe Thinkjet printer. Under normal operation, the unit requires no external gas lines, but abottle of helium gas with a low-pressure regulator (0 to 10 psi) and a modest length offlexible plastic hose is needed when cooling the unit down. The small Edwards E2M2 (orAlcatel) vacuum pump, located inside the control console, is fitted with a replaceable exhaust
filter and should not require venting to the outside atmosphere, but a fitting is provided for
attachment to a helium recovery system if desired. No water service is required.

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The MPMS has been designed to operate without a superconducting magnetic shield aroundthe SQUID detection coils, allowing magnetic field changes and sample measurements to be
executed in rapid succession. Rejection of interference from nearby magnetic sources isachieved by using a small spacing and high degree of balance in the second-derivative
detection coils. Nonetheless, large magnetic sources (such as elevators or automobiles) caninterfere with measurements if they are located very near the instrument. To avoid this typeof interference, the instrument should be located at least several meters from any such large
magnetic objects. Smaller items such as steel frame chairs or steel lab stools should be kept
several feet away, or, at least, kept stationary while sample measurements are being
performed.

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MPMS Hardware Reference Manual

1.4 Unpacking And Initial Setup
The MPMS is typically packaged for shipment in five crates, with the individual componentsof the system distributed among the crates as follows:1.

The dewar cabinet and dewar are packaged and shipped in the same container. Padding
is provided to keep the dewar from shifting during shipment.

2.

The control console with all control electronics and cabling installed. The only
component that must be installed during the setup is the vacuum pump.

3.

The vacuum pump is shipped in its own container to prevent possible damage to othercomponents of the system in the case of an oil leak. The vacuum pump is filled with oil
at Quantum Design and is ready for use.

4.

The MPMS probe is the most delicate component of the system and is shipped in a
specially designed shipping crate to ensure its safety. This crate, in particular, should
be saved for use in the event the system is moved to another location or the probe must
be returned to Quantum Design for upgrade or repair.

Note: For the safety of the unit do not remove the MPMS probe from its shipping crate until
the dewar cabinet and dewar are set up and ready for the probe to be installed.

5.

The HP computer, its peripherals, the sample transport mechanism, and a variety ofaccessories for the MPMS including the helium transfer tube (after being unpacked andtested at our facility) are crated in the same container. The MPMS operating manuals
for the system, as well as manuals for items manufactured by other vendors, are also
included in this container.

CAUTION

If the dewar crate is not upright when it arrives, the dewar may havebeen damaged in shipment. Contact your Quantum Design service
representative immediately.

After checking the exterior of the shipping crates for visible damage, unpack the dewar
cabinet, control console, and vacuum pump according to the following sections. The dewar

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1-11

cabinet, with the dewar already mounted inside, is packed in a large wooden crate. ~are has
been taken at Quantum Design to ensure that the dewar was properly crated and shipped inits upright position as indicated on the crate. It should arrive at its destination in the sameorientation.
1.4.1 Uncrate the Dewar
To uncrate the dewar, carefully remove the wood screws from the top and front side of
the crate (maintaining its upright position), and lift the dewar and cabinet out of theshipping crate. Remove and set aside the cabinet top, and remove the foam packing
material from around the top and bottom of the dewar. After the dewar and cabinet
assembly are uncrated, examine the exterior of the dewar for damage. (It should not benecessary to remove the dewar from the cabinet for this inspection.) Also look insidewith a flashlight to examine the neck for cracks or misalignment, and verify that the
belly is clean and dry. Place the cabinet and dewar in its final position, and adjust thefeet on the bottom of the support box to level the top edges of the cabinet and toprevent any wobble.
The dewar is suspended inside the cabinet with rubber shock mounts with four 1/4-20
threaded rods that should already be in place. After the cabinet is leveled, adjust thenuts at the top of the threaded rods to lift the dewar about 1 cm off the floor. Now
replace the cabinet top, and check the clearance between the cabinet top and the dewar.
Adjust the dewar height to leave only a small gap between the dewar and the cabinet
top to prevent small screws or tools from dropping down inside the cabinet. Once theheight is correct, adjust the individual supports inside the dewar cabinet to level the topof the dewar and center the bottom of the dewar in the cabinet.
1.4.2Uncrate the Control Console
Uncrate the control console by removing the wood screws from the top and front of theshipping crate and lifting out the console.

CAUTION

The control console cannot be lifted by its top. To remove theconsole from the crate, slide it forward until it can be lifted from thebottom lip which forms the toe space.

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The console is shipped with its internal cabling installed. The cables that connect to the
MPMS probe are connected inside the cabinet and looped through the holes in the backpanel for shipment. Once the layout for the instrument has been determined, the cables
can be routed through the slot on the correct side.
Remove the lower front panel from the console and open the rear door. Also, remove
the protective packing from the flange on the end of the pumping line inside the console
which hangs down from the gas control unit.

1.4.3Uncrate the Vacuum Pump
Uncrate the vacuum pump, and remove the blanking plate from the inlet of the 'foreline
trap. The foreline trap has already been filled with absorbent, and extra absorbent ispacked with the pump in a sealed container. Remove the plastic cap from the black
plastic fitting at the front end of the pump, just above the oil level sight glass.

CAUTION

Verify that there is sufficient pump oil in the Edwards vacuum
pump (or Alcatel) and that there are no plugs in the inlet or exhaust
ports. Also, do not turn the pump on until the cap on the exhaust
port has been removed.

Set the pump on the floor inside the console with its motor toward the back of.theconsole. Attach the hose from the oil mist filter to the black plastic fitting on the top of
the pump body and tighten the hose clamp. Carefully position the pump so that theflange fitting on the end of the flexible metal hose mates readily with the foreline trap
input flange without twisting or stressing the pumping line. If the flanges do not mateproperly, it may be necessary to loosen the fitting at the upper end of the pumping line
so the flange at the lower position can rotate slightly. If the upper fitting is loosened,take care not to over tighten it when finished. The fitting contains an o-ring seal andshould be tightened only enough to keep it from loosening under vibration.
After the metal vacuum line and the exhaust lines are connected, plug the AC line cordfrom the pump into Jack JB-7 on the rear of the Power Distribution Unit (PDU). The
vacuum pump line cord should have a label near the plug indicating the correct jack.
The electric motor on the vacuum pump can be configured for either 115 V AC or 230

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1-13

V AC. The motor has been configured and tested at Quantum Design at the same
voltage rating as the rest of the system, and no further modifications should be requiredat this time.

1.4.4Uncrate the MPMS Probe
The probe is packed in a long wooden crate with skids on one side. The side opposite
the skids (the top) is attached with wood screws. Lay the box down on the skids, andremove the top.

CAUTION

Do not attempt to remove the probe from its shipping crate throughthe end, or with the crate standing on end. Also, remember to savethe crate and packing material for future use.

The head of the probe and the superconducting magnet are packed in foam rubber toprevent lateral movement and are held in place in the long dimension of the box by awood support plate with a U-shaped notch. Remove this plate by pulling it straight up
past the foam rubber, and carefully remove the top foam rubber blocks at both ends.
The probe can now be lifted out by holding BOTH the head and magnet ends but
avoiding pressure on the small lines that run along the shaft. If the probe is to be laid
on a bench, use the foam rubber "V" from the crate to support the magnet. Wheninserting the probe into the dewar, let the probe hang vertically by holding it at the top
as you lower it into the dewar, taking care not to bump the magnet or capsules against
the edge of the dewar opening. Ensure that the o-ring between the probe and dewar isin place and properly greased.

1.4.SUncrate the Sample Transport
Now unpack the transfer tube and accessory kit. Bolt the probe into place using the
1/4-20 socket head screws provided, and attach the sample transport mechanism to the
top of the probe. Ensure that the correct o-rings (Quantum Design part numbers
VON2-017 and VON2-026) are installed beneath the transport mechanism. M,ount theModel 2000 SQUID amplifier on the back of the dewar cabinet. (There will be twoModel 2000 SQUID amplifiers if your system was ordered with the longitudinal andtransverse SQUIDs.) Mounting screws will already be inserted in the mounting holes.

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Quantum Design

MPMS Hardware Reference Manual

Remove the screws and attach the amplifier(s) to the dewar cabinet. If the MPMS has
the Transverse SQUID option installed, place the Transverse Model 2000 in the left
mounting location, looking from the back towards the front on the dewar cabinet.
Connect the cables from the control console, matching the color-coded strain relief
boots on the cables with the matching rings on the receptacles mounted on the MPMS
probe. Finally, connect the vacuum lines between the console and probe. The vacuum
lines are different sizes and cannot be interchanged. Install both lines with the 90degree elbow at the control console. The unit is now ready for transferring liquid
helium.

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1.5 Safety
The MPMS superconducting magnet produces extremely strong magnetic fields. Following
safety procedures regarding the magnet is critical to laboratory safety. Furthermore,. theMPMS utilizes cryogenic liquids for temperature control. There are several concerns
surrounding cryogens: they burn skin on contact and they expand rapidly when warmed.
Certain safety precautions are necessary when dealing with the liquid helium (and the liquid
nitrogen, if a nitrogen-jacket dewar is included in the system) that the MPMS requires. Also,
general electrical safety procedures should be followed, since the MPMS has several piecesof electronic equipment.
The most useful pieces of advice concerning safety are to use common sense and to be awareof the system's state and of your surroundings. If the system behavior appears abnormal,
something may be wrong with the MPMS. If so, consider whether or not the problem posesa threat to personnel in the laboratory and take appropriate action. For the most part, theMPMS is provided with safety features to keep accidents from causing injury or serious
equipment damage. Read the precautions below carefully and keep them in mind wheneverworking with the MPMS. Inexperienced users should be supervised.

1.5.1 Cryogenic Safety
Section 2.2 explains cryogenic safety. See section 2.2 for more details.

1.5.2Magnet Safety
Because the superconducting MPMS magnet can trap magnetic flux in it, it is possible
to leave a charged magnet completely unconnected to the rest of the system. Doing so
leaves users no way to discharge the magnet directly, so avoid this practice. Neverdisconnect a charged magnet from the magnet controller and do not disconnect
any of the other connections in the system while a magnet is charged. Several
different cables contain connections for magnet control. Be sure to drive the magnet tozero field before disconnecting any cables if the probe ever needs to be disconnectedfrom the controllers for any reason.

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Quantum Design

MPMS Hardware Reference Manual

WARNING!

Never disconnect a charged magnet from the controllers. If the probemust be disconnected from the controllers, be sure to drive the magnet
to zero field before disconnecting the controllers from the probe head.

Superconducting magnet supplied with the MPMS is capable of disturbing computer
monitors, affecting electron microscopes, erasing credit cards, attracting ferromagnetic
tools, etc. Transverse magnets produce substantially stronger fields surrounding
the dewar than longitudinal magnets do. Keep in mind that the magnet in yoursystem produces strong fields that are not completely confined to the system unless it
contains some type of magnetic shielding.
It is recommended that the magnetic field around the MPMS be measured and a line
drawn to denote the region outside which the magnetic field does not exceed fivegauss. The determination of where this line lies is the user's responsibility, since itvaries from system to system. It is typically found about 1-2 m (3.3-6.6 ft.) from theedge of the dewar. No heavy ferromagnetic objects (e.g. gas cylinders, large tools,etc.) should be brought within this region when the magnet is charged. Gas
cylinders in the laboratory should be secured to the walls and only informed personnel
should be allowed to use large tools in the presence of the MPMS. It is possible tocause injury to personnel and damage to MPMS equipment by allowing heavy objects
to be attracted to the MPMS.

WARNING!

To be safe, keep all objects made of iron, nickel and otherferromagnetic substances at least 3.0-4.5 meters (10-15 feet)away from the MPMS dewar.

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Introduction

1-17

Furthermore, the magnetic fields produced by the MPMS can be dangerous or fatal towearers of pacemakers and other electrical or mechanical medical devices. Anyone

wearing a pacemaker or similar device should stay at least 3.0-4.5 meters (10-15feet) away from the MPMS dewar. This information should be posted in thelaboratory where the MPMS is operated so that people wearing such devices are awareof the presence of large magnetic fields.

WARNING!

Anyone wearing a pacemaker or similar medical device should
stay at least 3.0-4.5 meters (10-15 feet) away from the MPMS
dewar.

1.5.3Electric Safety
The MPMS component are powered by standard 120 or 240 V AC power lines. These
voltages are potentially lethal and appropriate care should be exercised around theequipment. Electronic equipment should be powered down and unplugged before
opening or removing any covers. Liquids should be kept away from the computer andelectronics cabinet. Frayed or damaged cords should be replaced immediately.

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1.6 Contacting an Authorized Quantum Design Representative
If you have trouble with your PPMS, contact your local Quantum Design service

representative for assistance. Authorized Quantum Design service representatives are listed
below. Please be prepared to describe the problem, the circumstances surrounding thetrouble and the system's recent history.
EuropeL.O.T.-GmbH
Im Teifen See 58
D-64293 Darmstadt, Germany
E-Mail:101657.1571@COMPUSERVE.COM

India

V.S. Scientific Instrument Agency
RZ-38 Lane No. 6, Tughalakabad Extension
New Delhi, 110019 India

Tel:
Fax:

9111-644-7577
9111-642-5540

Japan

Indeco, Inc.
Independence and Collaboration
1-11-14, Kasuga, Bunkyo-ku
Tokyo, Japan 112

Tel:
Fax:

813-3818-4011
813-3818-4015

TaiwanAmega Scientific Taiwan Ltd.
3rd floor, 570
Kuang Fu South Road, Taipei, Taiwan R.O.C.

Tel: 886-2-758-0084
Fax: 886-2-723-0956

UnitedQuantum DesignStates11578 Sorrento Valley RoadandSan Diego, CA 92121
All Other
Countries
E-Mail:SERVICE@QUANDSN.COM

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Tel: 49-6151-8806-31
Fax: 49-6151-896667

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Fax:

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619-481-7410

2-1

Chapter Two:

The Liquid Helium System

The liquid helium system for the MPMS comprises the liquid helium dewar, the helium tr~nsfer
line, the transfer adapter fitting packed in the utility kit, and the excitation electronics for the level
meter which are integrated into the 1822 MPMS controller. In addition, the MPMS control
system software automatically monitors and updates the helium level reading in the system, andprovides the user with a data plotting routine with which to monitor the helium level continuously
during transfers.

2.1 The MPMS Dewar And Helium Level Monitor
The MPMS liquid helium dewar of approximately 56-liter capacity provides the cryogenic
environment required by the Temperature Control Module (TCM), SQUID detector system,and the MPMS superconducting magnet. It is constructed of aluminum except for the neckwhich is G-10 fiberglass with a thin sheet of embedded stainless steel to serve as a diffusion
barrier. The dewar itself is a stand alone component, but in the MPMS system it is enclosed
in a supporting framework that provides both support and vibration isolation. The dewar israised off the floor by tightening the four nuts located above the rubber shock mounts insidethe dewar cabinet. As the nuts are tightened, take care to level the top plate of the dewar,
and ensure that the dewar hangs so that it is centered at the bottom of the cabinet.
The helium level in the dewar is monitored with a superconducting helium level metyr probe
installed on the MPMS probe assembly. The MPMS control software automatically activatesthe current to the level meter once each hour, reads the voltage across it, and turns the meter
off again. The helium level reading in the graph area of the HP monitor screen is thenupdated to reflect the new reading. It is important that the level meter not be left on since itdissipates a significant amount of heat and will increase the helium consumption substantially.
Approximate helium level locations are shown in Figure 2-1. When transferring helium,
however, the user needs to monitor the helium level continuously. It is particularly useful tohave the data presented in graphical form to indicate any problems that may occur during thetransfer - if the storage dewar from which you are transferring is emptied, for example. The
MPMS system provides both the percent of helium in the dewar and this data in graphicalform in the graph area by accessing FS (Graph) IDisplay Graph IHelium Transfer. The
helium level will now continuously plot the helium level. The percentage of helium is shownin the status window. It is important to activate the Helium Transfer within the Display
Graph menu in order to provide up-to-data information, otherwise the percentage amountwould represent the last half-an-hour update. (See the MPMS Software User's Manual for
details.)

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50% _ _____.!~~--------t---T op of Magnet
40%

Center of Pick-up Coil &30%

Bottom of Magnet

Figure 2-1 MPMS Helium Levels

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Liquid Helium System

2-3

The final components of the liquid helium equipment are a standard commercial liquid heliumtransfer line and a transfer adapter fitting for sealing the transfer tube to the MPMS probe
assembly. When preparing to transfer, slip the adapter fitting onto the end of the transfer
tube to be inserted into the MPMS dewar, then cool the transfer tube by pushing liquidthrough it. When the plume appears at the output of the transfer tube, put the end into the
MPMS dewar through the port where the dewar relief valve normally resides, and seat thetransfer adapter into the port. During the transfer the helium level can be monitored throughthe HP computer.
The helium consumption in the system is approximately 4.5 to 5 liters/day when running thesystem below about 200 K, increasing to about 6 to 7 liters/day when running at room
temperature. While the MPMS dewar has a 56-liter capacity, the superconducting magnet in
the system requires the liquid helium level to be at least 35 to 40 percent to operate. Hence,
to operate at the highest fields, the liquid helium should be replenished every 5 to 6 days.

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2.2 Safe Handling of Liquid Cryogens

WARNING!

Protective clothing; including thermal gloves, eye protection, andcovered shoes; should always be worn when working with liquid
helium, liquid nitrogen or any other cryogen.
In the event of a dewar rupture or spill of cryogenic materials, vent
the room immediately and evacuate all personnel.

The precautions required by personnel handling liquid helium are related to the very low
temperatures of the liquid and, when stored, its treatment as a high-pressure gas. Directcontact with surfaces or materials just removed from the helium bath, or exposure to highboil-off gas flows will freeze the skin almost instantly. Protection in the form of insulated
gloves and safety eye glasses should always be employed.
Helium gas is an odorless, colorless, inert material that is non-flammable. While the gas itself
is not toxic it can displace air in confined areas, potentially causing asphyxiation.
Transferring liquid helium from one container to another or any operation that produces ahigh boil-off of gas from the liquid should be performed in open shop or laboratory areas.
Lack of oxygen causes dizziness, unconsciousness or death. More importantly, in anoxygen-depleted atmosphere, the body will not experience the buildup of carbon dioxide that
normally produces respiratory distress. In this case a person may simply lose consciousness
without first realizing that anything is wrong. When using liquid helium, always use proper
ventilation.
Because helium has a relatively low latent heat of vaporization, care must be exercised in thedesign and use of apparatus that contains it. Pressure-relief valves must be adequately sized
to allow for sudden vaporization of liquid. Both the TCM and helium dewar provided by
Quantum Design employ relief valves and burst disks to provide safe operation if there iseither a leak into any of the insulating vacuum spaces or the superconducting magnet
quenches. Any user-supplied equipment that utilizes an open volume exposed to liquid,
particularly sealed volumes that might contain a small leak, should be similarly protected.

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Liquid Helium System

2-5

Liquid helium is the coldest liquid that will exist at atmospheric pressure and is therefore avery effective cryopump. If a vessel containing liquid helium is left open to the atmosphere,
air and other gases will rapidly condense and solidify inside. This can easily plug pressure
relief passages and transfer ports. Since helium gas is constantly evaporating from the liquid,high pressures within the container develop quickly. It is therefore essential to maintain apositive pressure (above atmospheric pressure) within any storage container and to makecertain that all ports and orifices, except proper relief valves, remain closed when immediate
access to the helium is not required.
Helium-cooled surfaces exposed to the atmosphere can similarly attract and condense air.
Because nitrogen has a lower boiling point than oxygen, this gas will evaporate first leaving
an oxygen-enriched residue that can flow onto surrounding surfaces. Contact withspontaneously combustible materials such as oil or grease can produce ignition, therefore
possible exposed surfaces should be clean and free of such materials.

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3-1

Chapter Three:

Cool Down Procedure

This section outlines the initial cool down procedure. It requires only liquid helium.

3.1 Initial Cooldown
This is the procedure for cooling the system from room temperature. Ensure that the large
o-ring is in the groove in the top surface of the dewar, and install the probe in the dewar.
Orient the probe as you wish, and secure it with the 1/4-20 X 3/8" socket head screws. Do
not overtighten the screws - they only need to seal the top plate against the o-ring. Attach
the pumping lines and electrical cables according to their color coding, and connect theflexible gas lines to their respective connectors. Be sure to connect the end of the gas lines
with the 90 degree elbow to the console.
Turn on the main power circuit breaker located on the back of the Power Distribution Unit
(PDU) and the main power switch on the front panel of the PDU. (On earlier models of the
PDU, the main power switch also serves as the main power breaker, and there is not a
separate main power breaker on the rear panel.) Tum on the pump with the circuit breakeron the PDU rear panel. The HP computer system (including printer) can now be connectedto the control console with its GPIB cable and turned on. Also turn on the power to the1802 RIG bridge and the 1822 MPMS controller. Type MPMSR2 into the HP computer at
the DOS prompt to initiate the control program.

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3.2 The Initial Transfer
The initial transfer will require between 75 and 90 liters of liquid helium to cool down thesystem and fill the dewar.
For the first transfer, the output end of the transfer tube should be fitted with one of theextensions provided which will reach to within a few inches of the bottom of the MPMS
dewar (about 44 inches (111.76 cm) below the top surface of the dewar). Just before thetransfer tube is inserted into the dewar, the plug should be removed from the MPMS top
plate, and the transfer fitting installed. It should seat in the tube sticking up from the top
plate, and the horizontal tube should be directed away from the head. If a helium recovery
system is being used, you may wish to connect it to this exhaust fitting. Open the coolingvalve from the Diagnostic Gas Controls menu (F7-Diagnostic Menus, move cursor to Gas
Controls and press Enter). This will provide full helium gas flow and help prevent blockingof the small impedance tube.
Insert one end of the transfer tube into the storage dewar and the other end into the transfer
port. Insert the transfer tube into the MPMS dewar slowly, making sure that its extension
does not bump into the magnet or other parts attached to the lower part of the probe. The
transfer should be started slowly to take maximum advantage of the cold helium gas. Since
the initial transfer will take 2 to 3 hours, it is helpful to have a small fan or a hair dryer
directed across the head during the transfer to help keep excessive moisture from condensing
on the head of the probe.
The transfer rate can be set by adjusting the pressure in the storage dewar. While the dewar
and probe are cooling down, the pressure should be held at about 200 mm of mercury. Thisshould produce a steady gas flow out of the transfer fitting. When liquid begins to collect,
normally after about 1 hour, the flow will momentarily drop to zero, then resume. Also, if
the helium level is being plotted on the HP computer, it will begin to increase at this time. As
the liquid helium level increases, the gas flow out of the pump will increase to a maximum of
2.5 liters/min. Once this flow rate has been achieved and the helium level is greater than
25%, the cooling valve can be closed. The SQUID should also be tuned at this time as
described in the software manual. Continue the transfer until the helium level reading reaches
100% or until the level stops increasing which indicates an empty storage dewar.
It will take 24 to 48 hours for the dewar to completely cool down and equilibrate, and a highbut decreasing boiloff should be expected during this period. The quiescent boiloff of thesystem with the sample region cold (less than about 200 Kelvin), is about five liters of liquid
per day. This loss is higher when the sample tube is warm or when the system is being
cooled down in the high-power cooling mode.
·

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3.3 Subsequent Transfers
The helium level in the system should be kept at about 40% or higher to provide cooling forthe superconducting magnet. If the level drops below 40%, the magnet should not be used at
its full field. Subsequent helium transfers into a cold MPMS dewar are essentially the sameas the initial transfer with the following exceptions:

WARNING!

Set the magnetic field to zero before beginning a helium transfer,otherwise the magnet may quench.

1.

The magnetic field should be set to zero before beginning the transfer. If the magnet isleft at a high field when the transfer is started, the initial process of inserting the warmtransfer tube into the dewar may cause the magnet to quench.

2.

A small wire or toothpick should be slipped into the dewar relief valve to release thedewar pressure before removing the transfer port plug.

3.

The output end of the transfer tube only needs to get into the belly of the MPMS dewar(about 16 inches (40.64 cm) below the top plate), so no extension should be used insubsequent transfers.

4.

Before the transfer tube is inserted into the storage dewar, it should be cooled py
blowing cold gas through it until a plume appears at the outlet. If the warm tube isinserted first, the initial warm gas from the tube will boil off liquid already in the MPMS
dewar.

At the beginning of the transfer, before inserting the transfer tube into the storage dewar;
remove the screw cap, compression ring, and o-ring from the top of the transfer fitting, andslip them up over the output end of the transfer tube. Then with the transfer fitting in place,after the tube has been precooled, the tube can be slipped into the transfer fitting, and thescrew cap tightened to seal the o-ring around the transfer tube.
Note: If you try to insert the transfer tube through the o-ring while cold gas is coming out,
the o-ring will freeze to the transfer tube causing it to jam as it is going through the

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MPMS Hardware Reference Manual

fitting. Be sure the o-ring, the compression ring, and the screw cap are installed overa warm transfer tube.
After the transfer tube has been inserted into the MPMS dewar, the pressure in the storage
dewar can be set to about 1 psi. The progress of the transfer can be monitored on the HP
computer with the helium level plot. At the transfer rate produced by the 1 psi storage dewarpressure, it will talce 30 to 40 minutes to fill the dewar when starting at a level of 40 percent.

Note: If the exhaust of the transfer tube is connected to a helium recovery system, a pressure
greater than 1 psi may be required to transfer helium. The higher pressure may beneeded to overcome backpressure from the helium recovery system. Typically only 1
or 2 psi more pressure would be required.

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4-1

Chapter Four:MPMS Temperature Control
SystemThe 1802 RIG bridge provides active temperature control for the MPMS, but the 1822 MPMS
controller and the MPMS control system software in the HP computer also play important roles inthe variable temperature sweep capability of the system. In this section we give a brief descriptionof the MPMS temperature control system, and discuss some of its complexities.

4.1 Physical Configuration
4.1.1 Description
The physical configuration of the sample chamber and temperature control system isshown in Figure 4-1. Cooling is provided by cold gas drawn into the cooling annulus
from the helium bath, and the sample chamber is heated by applying power to either thechamber or gas heater. Longitudinal copper wires along the length of the sample
chamber maintain thermal uniformity, and a few millimeters pressure of helium gas in
the sample chamber provide thermal contact with the sample.
When the system is setting a new temperature, it normally uses a high-power heating or
cooling mode until the temperature nears the specified control point. In this mode,heating is provided by the chamber heater and cooling is achieved by drawing gas
through the cooling annulus at high flow rates. In the high-power mode, the heating
rate (when the system is initially at room temperature) is about 10 Kelvin/minute, andtypical cooling rates exceed 20 Kelvin/minute. When the system temperature nears thetarget temperature specified by the user, the MPMS control system switches to a lowpower control mode using the gas heater.
There are two fundamentally different control mechanisms used in the system. The
normal mechanism is used for all temperatures above about 4.4 Kelvin, while below thistemperature, control is achieved by controlling the pressure on a small reservoir ofliquid helium. The MPMS control system automatically selects the correct mechanism
for the specified temperature.

Note: The crossover temperature, which can be set from the MPMS control system,
depends on the boiling point of helium at ambient atmospheric pressure. Hence,its value will vary with the altitude of the user's site. The correct value for thesite is normally set by the Quantum Design service representative when thesystem is installed and may vary from the sea level value of 4.4 Kelvin.

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MPMS Hardware Reference Manual

MPMS TEMPERATURE CONTROL MODULE

-0

t

+O
+o
Outer
Vacuum
Tube

-0

0-

I

t

Sampleo+o+t0Cooling
Annulus

SampleChamber

Inner
VacuumTube

Pick-Up
Coiltt

VacuumSampleTube

Super
InsulationttSampleChamber
HeaterLiquidHeliumVacuumttttGermanium
Thermometer

Platinum
Thermometert

Gas
Heater~lF-

JJ Ltr--L~

Helium Reservoir

Figure 4-1 MPMS Temperature Control Module

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-------//

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Crossover Tube

iquid
HeliumFlowChapter Four:

Temperature Control System

4-3

4.1.2Low-Power Mode
When the system is controlling the temperature above the crossover temperature, and is
at or near its target temperature, thermal stability is maintained by using the gas heaterto warm the incoming helium to the same temperature as the sample chamber. In thismode, the sample chamber can be slowly warmed or cooled by increasing or decreasing
the heater power to raise or lower the temperature of the gas. Since the heat capacityof the gas is small and the flow rate is low, this mechanism provides low-power thermal
control near the target temperature.
The gas flow through the annulus in this mode, about 100 cc/min at standard
temperature and pressure, is controlled by a needle valve located inside the gas/magnet
tray in the MPMS control console. This valve is set at Quantum Design, and should
not require adjustment by the user. If this valve must be adjusted, attach a floating-ballflowmeter to the output of the vacuum pump (at the output of the mist filter just inside
the rear door of the console), and adjust the needle valve to give an indicated flow of
100 cc/min. This setting corrects the flowmeter calibration for helium rather than air.
Note: The needle valve in the MPMS control console is set at Quantum Design toprovide the correct flow rate. If this valve is set incorrectly, the time required
to achieve temperature stability in the system will be substantially increased.
However, a failure to reach or maintain the correct temperature usuallyindicates a more serious problem, and you should contact you Quantum Design
service representative.

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4.2 States of The Temperature Control System
While the control system above the crossover temperature is fundamentally different thanbelow it, both regimes provide active control, and the specified temperatures are reached andmaintained without manual intervention. Because of the dramatic difference in the rl?quired
control mechanisms in both temperature regimes, the control system is particularly complex.
Consequently, the system will sometimes appear to be malfunctioning when, in fact, it iscycling through an operation that is designed to both minimize the time required to achieve
stability and eliminate thermal gradients which may have been introduced into the system.
There are essentially five states of the temperature control system that will be apparent when
the system is operating. They are as follows:1.

Stable temperature control at temperatures above about 4.4 Kelvin in which the control
system can maintain the specified temperature as long as required.

2.

A high speed cooling mode that can provide cooling rates (when the system is initiallyat room temperature) of more than 20 Kelvin/minute.

3.

A high-power heating mode that typically warms the sample chamber at about 10
Kelvin/minute when the system is initially at room temperature.

4.

Stable control at temperatures below 4.4 Kelvin in which the control system canmaintain the required temperature for periods ranging from about 45 minutes to about 3
hours depending on the temperature and thermal load on the system. Active control inthis regime is achieved by controlling the pressure over a reservoir of liquid helium.

5.

Recycling of the thermal system when controlling the temperature below 4.4 Kelvin.
When the helium reservoir is exhausted, the system automatically refills the reservoir
and reestablishes control at the requested temperature.

During some of the above operations, the system will often appear to behave rather
strangely. When this occurs, allow the system to continue its operation for a few minutes
before intervening. If the system does not return to its control temperature in about 30
minutes, try resetting the temperature and observe the behavior. If the system does not
function correctly when controlling below the crossover temperature, the temperature
control software can be reinitialized by setting a temperature of 10 Kelvin, and letting thesystem stabilize there. If the system controls properly at 10 Kelvin, try resetting the desired
temperature. If the abnormal behavior continues, contact your Quantum Design service
representative for assistance.
The following sections describe the general behavior of the system in its different control
modes. You should be familiar with the various states of the system, and the characteristic

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Temperature Control System

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behavior when switching from one state to another. In the current MPMS control system,
there is no indication on the HP computer display indicating which control mode is currently
active, only whether the temperature is considered to be stable. At the end of this section we
provide some useful techniques for optimizing the performance of the system.

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4.3 Stable Temperature Control Above The Crossover
When a temperature change is initiated with the target temperature above the crossover
point, the MPMS control system invokes the high-power heating or cooling mode to quickly
get the temperature near the final target temperature. When close to the target value, thesystem is switched to the low-power mode described in section 4.1.2 to provide control at
the specified temperature.
When the temperature change is initiated, the first line in the status window will indicate thatthe temperature is no longer stable by displaying the word Settling to the right of thetemperature reading. When the system temperature has reached the target value and remains
within a specified range of the target value for 1 minute, the temperature is considered to bestable, and is so indicated by the word Settling being replaced by the word Stable.

Note: In the present software revision, the temperature is considered to be stable when it hasremained within 0.5% of the target temperature continuously for 60 seconds. If thetemperature exceeds that window at any time, the word Settling appears in the statuswindow until the temperature stability criteria are reestablished.

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4.4 High Speed Cooling Mode
The very high cooling rates achieved in the MPMS result from a high throughput of cold
helium gas drawn into the cooling annulus from the helium bath. At the highest flow rate,over 5 liters of helium gas per minute (at standard temperature and pressure) are drawn
through the cooling annulus producing (when the system is initially at room temperature) a
cooling rate of 20 to 30 Kelvin/minute. The problem encountered in cooling the system thisfast is that the bottom of the sample chamber, where the thermometers are located, coolsmuch faster than the upper part. Hence, during a high-power cooldown, large thermal
gradients are generated in the sample chamber that can take up to an hour to equilibrate if nocorrective measures are taken. Since the thermometers are not located directly in the sample
chamber, the thermometers will not accurately report the sample temperature.
The MPMS temperature control system has been carefully designed to minimize this problem
by actively controlling the Temperature Control Module (TCM) heaters and the gas flow to
reduce the thermal gradients following a rapid cooldown. When cooling down the sample
chamber, the temperature displayed will always undershoot the target temperature before
warming back up to it. The undershoot, which depends on both the target temperature andstarting temperature, may be as great as 40 degrees. In addition, when a large undershoot isused, the system will hold the temperature at the lower value for a period that may be as longas 5 to 6 minutes. This technique helps reduce the thermal gradients by cooling the upper
part of the sample chamber to nearly the correct temperature, then warm the lower part backup by using the gas heater at the bottom of the sample tube for the final approach toequilibrium.
The problem of thermal gradients is much more pronounced at the higher temperatures
where the heat capacities of the copper wires and the sample tubes are large. At low
temperatures, below about 301 Kelvin, the thermal time constants in the system are short,and thermal gradients relax quickly.
With undercool on and when the system is cooled from at or near room temperature (298 K)
to a temperature below about 101 Kelvin, the temperature will first drop to about 5 Kelvinand remain there for several minutes to allow the upper part of the sample chamber to cool
down. Immediately following this delay, the control system is switched over to its lowpower control mode and begins regulating the temperature. If the target temperature is
below about 10 Kelvin, it may be several minutes before the system achieves temperaturestability. After such a long cooldown, there will still be warm spots higher up that produce aheat flow down the sample chamber. Furthermore, the helium gas entering the coolingannulus is at about 4.2 Kelvin, so there is only a small temperature difference between theentering gas and the sample chamber, and hence, very little cooling power. When thisproblem arises, the temperature will typically drift slowly warmer, seemingly without
recovering. Given time, however, the system will recover and achieve the target
temperature.

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Quantum Design

MPMS Hardware Reference ManualThis problem also arises when attempting to proceed directly from room temperature to atemperature below the crossover temperature. Under these conditions, as soon as the delay
at about 5 Kelvin is over, the system will immediately attempt to fill the helium reservoir, but
the liquid will evaporate as quickly as it enters. The temperature control will then fail when
the RIG bridge tries to control the temperature below the crossover.
A cure for both of these control problems is to first cool the system to about 20 to 30 Kelvin,allow the temperature to stabilize at that point, then proceed on to the lower temperature.
The MPMS temperature control system has been designed to provide very accurate
temperature readout and precision temperature control, but the high speed temperature
slewing when cooling down carries the penalty of introducing substantial thermal gradients
into the sample chamber. The control system has been studied extensively to minimize theproblem, but there will still be some uncertainty in the final temperature after a high-speed
cooldown that we estimate could be as large as one percent. Since the temperature control
during a high-speed warmup should be somewhat better, we recommend that data becollected while warming up the system rather than cooling down. Also, since there is very
little overshoot when warming up, the elapsed time between data points will be shorter.
If undercooling during a high-speed cooldown presents a problem with experiments, you cantum it off. Choose Temperature Undercool in the Set Parameters menu (F4). In thismode the system will use a low-power cooling mode, and the temperature undershoot will beminimized, typically to 1 Kelvin.

In order for this mode to be operated, the following requirements must be met:
1.
2.

System temperature must initially be less than 200 K.
The temperature change must be 10 K or less.

If these conditions are not met, the system will function as it would with the "Undercool"
turned on.

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4.5 High-Speed Warming ModeAll wanning operations above the crossover temperature in the MPMS system use a twostage process. When the temperature change is initiated, the system is put into the highspeed wanning mode until the temperature approaches its target value. The control is thenswitched over to the low-power control mode. In the rapid warming process, up to 15 mw
can be delivered to the sample chamber heater producing a warming rate at room
temperature of about 10 Kelvin/minute. The heat is applied with a high spatial uniformity to
avoid generating thermal gradients in the system, and for this reason we generally
recommend that measurements be made as a series of increasing temperatures.

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4.6 Stable Temperature Control Below The Crossover
There is a fundamental change in the operation of the thermal control system at temperatures
below the boiling temperature of liquid helium. To operate the system below this crossover
point, we must allow liquid to fill the lower part of the flow annulus and set the temperatureof the system by controlling the pressure over the liquid. The annulus is "charged" withliquid by turning off the heaters and holding the temperature about 0.1 Kelvin below theboiling point of the liquid helium in the dewar. When the liquid level gets to the appropriate
level, the liquid input is cut off, and the system begins regulating at the desired temp~rature.
Temperature regulation is essentially performed by adjusting the flow rate at the pump which,in tum, determines the vapor pressure over the liquid and the temperature of the system.
Flow control in the system is provided by the proportional valve which in this mode is
assigned to one output of the 1802 RIG bridge via the 1822 MPMS controller.
While measurements are being made in this regime, the helium level will slowly fall due toevaporation of the liquid charge. When the liquid helium from the initial filling is exhausted,
the temperature of the sample space will rise rapidly. The control computer senses thiscondition and initiates a sequence to reopen the liquid input port, refill the annulus with afresh charge of liquid, and once again close the impedance and finally reestablish the desired
temperature by pumping on the liquid. This entire operation typically requires about 25
minutes to again reach the target temperature. The MPMS control system normally executes
this entire sequence without any operator intervention, making operation in this regime
completely automatic. One charge of liquid will last for a period ranging from 45 minutes toseveral hours, depending on the temperature being held and the heat load introduced to thesystem by the sample.
You should be aware of a few particular characteristics when operating the system i~ thismode. First, for the last 3 or 4 minutes before the helium reservoir is completely exhausted,
the temperature control will become somewhat unstable, characterized by rapid swings of atenth of a degree or more. When this condition occurs, the system will shortly begin therecycling process to refill the liquid reservoir.
Secondly, when performing measurements below the crossover temperature, setting thesequence of temperatures in decreasing order will dramatically increase the operating time of
the reservoir between refills. The reason for this is that it requires a substantial fraction of
the liquid in the reservoir to cool the remaining portion down from 4.2 to 1.9 Kelvin. Hence,
if you proceed immediately to 1.9 Kelvin after filling the reservoir, approximately half of thetotal liquid will be consumed just cooling down the remaining liquid. But if themeasurements are started near the crossover temperature, a significant fraction of the initialhelium charge will be consumed as the system successively lowers the temperature, and theamount of liquid that must eventually be cooled to 1.9 Kelvin will be much less. The
operating time of the reservoir when going immediately to the lowest temperature will be

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approximately 35 to 43 minutes, but the helium charge will typically last for 1 to 2 hours
when operating the system in the 3 to 4 Kelvin temperature regime.
One important final point must also be made here. When operating below the crossover
temperature, the HP computer monitors the temperature to determine when the liquid
reservoir is exhausted. The present software revision assumes that the temperature will comewithin 0.1 Kelvin of the target temperature within two minutes of the time that the newtemperature is requested. The thermal response of the system in this regime is very fast,
typically reaching the desired temperature in 20 to 30 seconds, which is consistent with thecriteria used in the HP computer. However, when the reservoir is full and the target
temperature is set to, say 1.75 Kelvin, it may take more than 2 minutes to reach 1.85 Kelvinbecause of the large volume of liquid that must be cooled down.
If this happens, the HP computer can mistakenly conclude that the reservoir is empty andbegin recycling the system to refill it. This problem can usually be avoided by setting anintermediate temperature of 2.4 Kelvin or so, which will cause the 2 minute 'timer to be reset
when the temperature reaches the 2.4 Kelvin intermediate value. When running the system
under automatic sequence control, we recognize that you will not have this flexibility. To
avoid difficulties when executing sequences, you should determine about how long thereservoir will typically last when performing a particular measurement sequence, anci
structure the sequence to avoid exhausting the liquid reservoir at precisely the time thelowest temperature measurements are being performed.

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4.7 Refilling The Liquid Reservoir
The most complex portion of the MPMS temperature control system is that which controls
the sequencing of events when operating the system below the crossover temperature. Thisis reflected in the fact that it requires about 25 minutes to completely cycle the systemthrough the refilling process.
When the MPMS control system determines that the reservoir is empty, it momentarily
increases the temperature to approximately 12 to 15 Kelvin, and begins the sequence to open
the fill port. When this fill port is open, the temperature will drop to below 5 Kelvin, and thesystem resets the 1802 RIG bridge to refill the system. The system is filled by maintfilning
certain flow conditions in the system for a specified period of time. Once the reservoir has
been refilled, the fill port is again closed, and the 1802 RIG bridge is again reset for
temperature regulation at the target temperature.
The control system for these processes is complicated. In the present software revision, it ispossible to confuse the system by manually setting temperatures while the computer isperforming some of these operations. If this occurs, the temperature control system can bereinitialized by setting a new target temperature of 10 Kelvin or higher, and letting the systemstabilize at that temperature. This will reestablish the proper control values in both the
MPMS software and the two subsystem controllers (1802 and 1822).
There are several behavior patterns of which you should be aware. These are itemized, as
follows, with a brief description of the expected behavior of the system in each case:1.

The system is operating below the crossover temperature and you set a target
temperature above the crossover. When this occurs, the system immediately begins
warming up to boil off the residual liquid in the reservoir, and initiates the sequence toopen the fill port. After the temperature reaches 8 Kelvin, the HP computer monitors
the system to determine when the fill port is open, and then proceeds to the new target
temperature. The delay to open the fill port is required to ensure that adequate gas
flow will be available to provide the proper temperature control when the systemreaches its new target temperature.

2.

The system is waiting for the fill port to open and you set a new target temperature.
This will produce no response from the system other than that the new target
temperature will appear in the status window. This is appropriate, however, since thefill port must be opened before any new temperature is set. At higher temperatures, thegas flow is required for temperature control, and at low temperatures the fill port must
be opened to refill the impedance. Once the port is open, the system will proceed to
the new temperature.

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The system has just completed filling the reservoir and you set a new temperature
above the crossover temperature. During a very brief few seconds at this time; thesystem may be vulnerable to a possible malfunction. If a new temperature is set when
the fill port closing sequence is in progress, the system will immediately initiate the fillport opening sequence and begin boiling off the helium in the reservoir. When thisoccurs, the system can enter a mode in which the vacuum pump is drawing a large
quantity of gas through the system, while the MPMS heaters are trying to warm thesystem above 10 Kelvin.
In this case, the gas flow will overwhelm the heaters, and the system will never reach
10 Kelvin, which represents a necessary condition for the system to proceed to its next
step. When this occurs, the condition can be cleared by setting another new
temperature, either below or above the crossover temperature. This condition neveroccurs when the system is running under automatic sequence control, and can occur
only when using the system interactively as the system passes through a brief transientstate. While we expect this problem to be resolved in future software revisions, it canbe easily avoided or corrected in the present system once you are aware of the problem,
and take care to avoid resetting the temperature at the end of the filling cycle.

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4.8 Configuration of the 1802 RIG Bridge
While the 1802 RIG bridge is the central component in the MPMS temperature control
system, the 1822 MPMS controller and MPMS control system software also play a vital partin the MPMS temperature control process. The system uses two thermometers to cover theentire temperature range of 1.9 to 400 Kelvin. A germanium resistance thermometer is usedfrom 1.9 to 40 Kelvin, and a platinum resistance thermometer is used above 40 Kelvin.
These two thermometers are assigned to two of the four thermometer inputs in the 1802 RIG
bridge. The other two thermometer inputs are available on a spare connector on the 1822
rear panel.
The heater control output on the 1802, designated as Driver #1, is assigned to the MPMS
gas heater at the bottom of the sample tube. The other heater output, referred to as Driver#2, can be switched between the chamber heater and the proportional flow regulator valve.
The switching capability for this heater is located in the 1822 MPMS controller. In thenormal configuration, Driver #1 is completely dedicated to the gas heater. When the system
has the optional oven installed, the gas heater is reassigned to drive the oven heater when
operating at temperatures above 400 Kelvin. Also when the oven is being used, Driver #2
controls the proportional valve to maintain the internal sample chamber temperature at about
room temperature, while the oven may reach temperatures as high as 800 Kelvin.
The following list summarizes the thermometer and heater control assignments for the 1802
RIG bridge:
1.

RIGB Chan# 1 - Germanium Resistance Thermometer - Used over the range l.9K < T
<40K.

2.

RIGB Chan# 2 - Platinum Resistance Thermometer - 100 ohms at 273 Kelvin, usedover the range 40K < T < 400K.

3.

RIGB Chan# 3 - Available through connector J-C2 on the 1822 rear panel. Used forthe oven thermometer when the oven is installed.

4.

RIGB Chan# 4 - Available through connector J-C2 on the 1822 rear panel. Not used.

5.

RIGB Drvr# 1 - Assigned to the gas heater at bottom of sample tube, or switched tothe oven heater when the oven is installed.

6.

RIGB Drvr# 2 - Assigned to the chamber heater or to the proportional flow control
valve to provide either high power heating or cooling. Assigned to the proportional
valve when the oven is installed.

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If the temperature control system seems to be malfunctioning, and continuously fails to reachor maintain the requested temperatures, it is sometimes useful to monitor the power being
delivered to the heaters and/or proportional valve. If required, the voltage being applied toeither the heaters or proportional valve can be monitored on the 1802 RIG bridge rear panel
from the colored binding posts. The binding posts are labeled Driver #1 and Driver #2.
Using the summary developed on the preceding page, you can monitor the control outputs as
the system cycles through its temperature control operations.
The complexity of the system, however, makes it difficult to analyze problems without acomplete knowledge of how the system functions, and you are encouraged to contact your
Quantum Design service representative for assistance if problems with the system recur
frequently.
Note: When contacting your Quantum Design service representative for assistance, it is vitalthat you be as detailed as possible regarding the exact state of the system when the
problem occurred and what action has been taken prior to calling them. Most
problems cannot be solved without specific information.

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5-1

Chapter Five:

Sample Handling System

The sample support mechanism comprises a support rod with a sliding clamp near the upper end,
and a double lip-seal assembly that provides the vacuum seal. The assembly is shown in Figure 51. The sample is suspended from the end of the sample tube by a nonmagnetic holder of the user's
choice. Typical sample holders may be quartz rods or tubes, or even clear soda straws.

5.1 Sample Support Assembly
5.1.1 Slide-seal Assembly
The vacuum seal assembly, referred to as the slide-seal assembly, contains a pair ofrubber lip-seal glands separated by a vented chamber. When the slide-seal assembly is
installed in the top of the sample transport unit this chamber is continuously flushed bya stream of helium from the dewar through a 1/3 psi check valve. This techniqueminimizes the amount of air which is literally "dragged" through the slide seals and into
the sarriple chamber as the sample rod moves up and down during a sample
measurement. Under normal conditions, all of the boiloff from the dewar is directed
through this chamber and from there to a hose nipple on the back of the sample
transport. It is important to connect a tube to this nipple if the unit is to be connected
to a helium recovery system.
The double lip seal design has been tested at Quantum Design and found to provide
excellent sealing against air leaking into the sample chamber. Unlike o-rings, however,the lip seals rely on a relatively sharp lip to provide the seal. This lip can be easily
damaged by failure to keep the sample rod properly lubricated or by removing a cold
sample rod too quickly. Because the area of contact at the seal is very small, a cold
sample rod can quickly freeze the lip seal at the point of contact as the rod is withdrawn
and tear the seal. If this occurs, the seals will leak air into the sample chamber during
the measurement. This can be particularly troublesome when making measurements at
low temperatures because oxygen is strongly paramagnetic, and if it condenses onto thesample, the measurements will be in error.
A small tube of Apiezon M-Grease is supplied in the utility kit with the system. This
grease has an extremely low vapor pressure, and works well as a lubricant for thesliding Seals. No harm will be done if too much lubricant is used, except that excess
grease will build up at the top of the slide seal assembly and become a bit messy. If thisoccurs, simply wipe of the excess grease with a Kimwipe or similar tissue. If too little
lubricant is used, however, the slide seals may be damaged and have to be replaced.

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Sliding .Clamp~

Slide-Seal Assembly

Gloss Sleeve

Sample Rod

Figure 5-1 The Sample Support Assembly

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Before using the system, become familiar with the "feel" of the sample sliding throughthe seals, and be aware of this whenever you are using the system. If the sample rod
begins to drag through the seals, or is cold as you remove it, slow down, and thenlubricate the seals as soon as you have the sample rod out of the unit.
Note: If the slide seals become damaged, do not throw away the assembly. The lip
seals, can be removed from their housing and replaced at little cost. By
contrast, purchasing an entire new slide-seal assembly is relatively expensive.

5.1.2Clamp Assembly
The clamp assembly which attaches the sample rod to the sample transport mechanism
is derived from a swagelock tube fitting with split nylon ferrules. The knurled nut on
the top of the clamp should be tightened firmly with the fingers, but only enough tokeep the support rod from sliding while measurements are being made. If the sample
rod should jam or freeze into place inside the sample chamber, this clamp should breakfree to avoid damage to either the sample rod or the sample transport mechanism.

5.1.3Sample Rod
The sample rod is made with an upper section of needle temper type 304 stainless steel
and a bottom section of quantalloy (silicon copper alloy). The stainless steel is used forstrength, good surface finish and low thermal conductivity. The lower section is madefrom quantalloy to minimize the magnetic signal in the SQUID detector caused by the
sample.rod.
The sample rod may be modified to carry wires down to the sample by cutting off theplug at its top end. We have found it convenient to use a microminiature connector at
the top end of the sample rod rather than working with long leads "pigtailed" out fromthe rod. The inside diameter of the sample rod is about 2.5mm.
If this is done, however, you must devise some means of sealing the top of the sample
rod against the continual vacuum that is held in the sample space. If carefully applied
and well cured, RTV type sealants should be suitable for this application. This type ofsealant also has the advantage of being removable if repairs or changes to the wiring aredesired. We recommend that the seal be made at the top of the sample rod that always
stays at room temperature, rather than at the bottom end that must survive extreme andrapid thermal cycling. In any event the sample rod should never be sealed at both ends,
since a small leak in either end can allow gas to condense inside the tube which could
produce a hazardous condition.

Note: Quantum Design has an optional Manual Insertion Utility Probe (MIUP) similar
to the description above. (See chapter ten for more information.)

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When the unit is first unpacked, the sample rods, slide-seal assemblies, and clip
assemblies are packaged separately. Handle the sample rods carefully as their entire
length must pass through the slide-seal assembly. If the sample rod is bent or dented, it
must be replaced. To assemble the mechanism, lightly lubricate several inches of thesample tube at its rounded end, insert this end of the sample tube into the glass sleeveand gently push it through the lip-seals. Slide the sample rod up until a few inches ofthe sample rod protrude from the glass sleeve. Slip the clip assembly several inches
past the rounded end of the sample rod and secure it by tightening the knurled stainlesssteel nut. Now lightly lubricate the sample rod between the slide-seal and the clip
assembly.

CAUTION

The sample rods are made of a very thin-walled tube to limit thermal
conduction down the rod. Consequently these rods are easily bent,
particularly the quantalloy extension at the lower end of the rod. If therod is damaged, it must be replaced. It will not seal properly when thedamaged portion passes through the lip seal. Please handle rods withgreat care.

5.1.4Mounting Samples
Samples may be mounted on the end of the sample rod using a variety of techniques.
Because of the wide variations in the types, sizes, and geometries of samples from
customer to customer; we do not supply a standard sample holder. There are several
techniques that previous customers have found useful.
One particularly useful sample holder is a thin-walled quartz tube. This can be attachedby mounting a nonmagnetic coupling on the end of the sample rod to mate thequantalloy portion of the rod and quartz tube together. The sample can then be held inplace by inserting it into the quartz tube, and stuffing quartz wool in beneath it.
(Quartz wool is comprised of tiny quartz fibers.) A similar sample mounting can beaccomplished with something as simple as a soda straw.
·
Another technique that can be used with tiny samples is to attach them to the side of asmall quartz rod with a dot of vacuum grease. If this is done, centering rings should be

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Chapter Five:

Sample Handling System5-5attached to the top and bottom of the rod to ensure that the sample does not get
scrapped off the rod as it is inserted into the sample chamber.
If either of these techniques is used, the sample should be mounted about 7 to 10 cm
from the end of the sample holder so that the end of the sample holder does not movethrough the detection coils during the measurement. The end of the sample holder will
also produce a signal in the SQUID detector; and if it approaches the coils closely
enough.to be detected, the signal will be distorted, and the magnetic moment
calculation for the sample will be in error.

Larger samples can be suspended from the end of the sample tube with white cotton
thread. However, this allows the sample to swing back and forth in the sample
chamber, causing corresponding oscillations in the SQUID detection system. This cancause measurement errors much larger than when using rigidly mounted samples.
Generally, we have found it much more desirable to use a rigid mounting rather thansuspending samples from a thread.

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5.2 Taking A Measurement
Once the sample is mounted on the sample rod, the following procedure describes the
progression necessary to take a measurement:·
5.2.1 Installing the Sample Rod Assembly into the Sample Chamber

WARNING!

Care must be taken about the length of the sample rod and sample
holder so that when the transport is initialized, the sample holder
will not hit the bottom of the sample chamber. This may destroy the
sample tube and possibly damage the sample transport unit. If thesample holder is longer than 23.6 cm, do not continue.

1.

Tighted the knurled nut on the slide seal assembly so that it is positioned
approximately 122 cm away from the center of your sample.

2.

Pull the sample rod up through the slide-seal so that the sample holder is drawn
into the protective glass sleeve (the shroud). Make sure the sample holder is flush
against the blue plug.

3.

Vent the sample chamber.
a.

b.

c.
4.

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If there is no sample present in the sample chamber and the READY LED ison, vent the system by closing the airlock valve. This automatically vents the
sample chamber. Close the airlock by rotating the handle counter clockwise
so that it points horizontally to the indicated CLOSED position. Wait for the
VENTING LED to turn off.
If there is no sample present in the sample chamber, the airlock is already in
the CLOSED position, and the green READY LED is on; toggle the handle
to OPEN then back to CLOSED. Wait for the VENTING LED to turn off.
If there is a sample present in the sample chamber, proceed to the next step.

Open the slide seal clamps on the sample transport socket block so the blue plug
may be released or in the case of a sample rod present, the slide-seal.

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5.

Remove the blue plug or the sample rod.

6.

Before proceeding, verify that the three o-rings in the blue plug socket block are inplace, free of debris, and not dry. Do not put too much grease on the o-rings, but
if necessary, apply Apiezon M-Grease so the surface of the o-rings are wet.

7.

Insert the sample rod into the sample chamber until the point where the slide-seal
housing can be secured into the socket in the sample transport.

Note: Ensure that the white "dot" is facing forward. This ensures proper gas flow
through the slide-seal. It may be secured by rotating the two rectangular
handles on the socket block so that the slide-seal is forced down agains~ thethree o-rings in the block by cam action.
8.

The blue plug of the slide seal assembly should be flush to the top of the socket
block.

9.

Close the slide seal clamps on the sample transport so the slide-seal assembly may
be fastened.

10. Press the button on the front of the MPMS probe labeled PURGE AIRLOCK toinitiate automatic purging of the airlock. When the green LED labeled READY
comes on, open the airlock valve by rotating the handle clockwise so that it points
vertically to the indicated OPEN position.
Note: If the READY LED does not light within a few seconds after the purging
sequence ends, there may be a leak in the sample handling system or check theannulus pressure gauge for a negative pressure. (Negative pressure ischaracteristic of acquiring low temperatures. The temperature must first
become stable before the READY LED will light.)
11. Lower the sample slowly and slowly turn the rod during the insertion process.
Note: If the rod appears to be dry or not moving smoothly through the lip seals, add
some Apiezon M-Grease.
12.

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Lock the clip assembly into the actuator shoe by tightening the thumb nuts.

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5-8MPMS Hardware Reference Manual

5.2.2Center the Sample
1.

Access the Register Sample menu (F2) and perform the following action~:
a.
b.

2.

Tum Autosample Tracking on. If it is already on, toggle it on.
Initialize Sample Transport in order to calibrate the transport to 0.27 cm
from the bottom of the transport.

Perform the center sample process, in which it may be necessary to apply amagnetic field. Briefly, the sample centering process includes performing a fulllength DC scan, adjusting the sample position, and then performing DC centeringscan. (See the MPMS software manual for more information.)

5.2.3Take MeasurementsCollect data by opening the Measure menu (F3), then moving the cursor to
Immediate and press ENTER. Data may also be collected through a sequence.

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5.3 Retrieving Samples And Cleaning The Sample Chamber
If a sample falls off the sample holder or the sample chamber becomes contaminated, theMPMS is designed to allow the sample chamber to be opened to room temperature without
danger of plugging small gas tubes or otherwise degrading the operation of the system.
Simply set the system temperature to room temperature or slightly higher (about 310 Kelvin),
and when the system becomes stable at that temperature, the airlock can be opened to theroom.

Note that wh~n the airlock is vented after closing the airlock valve, the airlock flushing valve
is left closed, which is its energized state. For this reason, when there is no sample in the unit
we recommend that the airlock plug provided with the system be installed in place of theslide-seal assembly, and then purge the airlock. When the system is left in this condition,
simply open the airlock valve slightly, then close it again to vent the airlock. The airlock can
now be opened to the room. The airlock flushing and venting valves can also be controlledfrom the Diagnostic Gas Controls menu under Flush Valve and Vent Valve, respectively(access the Diagnostic Menus (F7), move cursor to Gas Controls, and then press Enter).
Once the airlock is open and the temperature is set to 310 Kelvin, a rod with an appropriate
hook or spiral wire can be inserted to the bottom of the sample chamber to retrieve lost
samples, or a Kimwipe with a mild solvent can be used to swab out the sample chamber. If asolvent is needed, use it sparingly since the o-ring seals at the top of the sample chamber
around the airlock valve may be damaged by strong solvents.
After the lost sample has been retrieved or the sample chamber cleaned out, replace theairlock plug in the top of the sample transport mechanism, and with the airlock open press
the PURGE AIRLOCK button. This will purge the entire sample chamber of air and any
vapors remaining from the solvent, and it will restore the static helium pressure of a few
millimeters. You may wish to repeat this process again after a few minutes, allowing time forany residual liquid or water moisture to vaporize. When this process is finished, close theairlock valve, and the system is ready to accept another sample.

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6-1

Chapter Six:

MPMS Magnetic Field Control

Since the MPMS uses no superconducting shield to trap a magnetic field over the sample volume,the magnetic field on the sample is sustained by trapping a persistent current in the five teslasuperconducting magnet. The control system for the magnet is shown in Figure 6-1. The field ischanged automatically by the MPMS control system when you specify a new magnetic field.

6.1 Changing t.he Field
The automatic sequence engaged when changing the field is as follows:1.

Turn on the power supply and heater for the SQUID flux transformer heater. Turningon the flux transformer will prevent large standing currents from being trapped in the
SQUID sensing circuit as a result of the field change.

2.

Set the current switching relays for the correct polarity. Set the power supply output
to the current presently stored in the magnet.

3.

Turn on the persistent switch heater, and wait a few seconds to ensure that the switch
has been driven nmmal.

4.

Change the current to give the next desired field. When this current is reached, the1822 MPMS controller will overshoot the desired value, then approach it through aseries of decreasing amplitude oscillations. This procedure dramatically reduces
relaxation in the magnet following a field change.

5.

When t~e correct value of current is reached, the 1822 MPMS controller reads thevoltage across a reference resistor in series with the magnet power supply to ensurethat the desired current has been set. If the proper current is not flowing, it is adjusted
to be within acceptable limits. In the low resolution mode, the acceptable limit
corresponds to 1 gauss; in the high resolution mode the limit is 0.1 gauss.

6.

After the final value of current has been reached, turn off the persistent switch heater.
Wait a few seconds to ensure that the switch has returned to its persistent mode.

7.

Set the power supply current to zero, turn the power supply off, and reset the polarity
relays to shunt the persistent switch. This is denoted as "Off" in the MPMS control
software.

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KEPCO P/S

Control ·::;: 1 Volt

Digitizer

1/0 Control
1822 Controller

MagnetProtection Diodes

SwitchHTR
Figure 6-1 MPMS Magnet Controls

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Chapter Six:

Magnetic Field Control

6-3

After this automatic sequence is initiated by the MPMS control software with a single
command to the 1822 MPMS controller, the entire sequence of events is processed entirelyby the 1822 controller without further attention from the HP computer. When the sequenceis finished, the word Stable will appear next to the field value on the HP computer screen.
There are two modes available for making field changes which may be selected from the
MPMS Executive menu. These are Oscillate and No Overshoot.

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6.2 Oscillate Mode
Since the MPMS uses no superconducting shield around the SQUID pickup coils, themagnetic field applied to the sample is just that trapped in the magnet in its persistent mode.
However, when a superconducting magnet is put back into the persistent mode immediately
after changing the field, the magnetic field will gradually relax due to the magnetic field lines
slowly creeping through the superconducting windings. Although the SQUID sensi~g coils
are balanced to reject signals from the magnet to a level of about 0.1 percent (due to theextreme sensitivity of the SQUID detector) any relaxation in the magnet will still produce a
substantial drift in the SQUID detector output for several minutes after changing the field in
the magnet.
This type of relaxation can be minimized by first going past the intended magnetic field, thenoscillating the current in the magnet back and forth about the target field with a decreasing
amplitude of oscillation. The MPMS control system uses this technique when changing thefield to minimize drift in the SQUID detector immediately following a magnetic field change.
The initial overshoot in the MPMS is approximately 30 percent of the total field change, andthe amplitude of each oscillation is 70 percent of the preceding one. The oscillations
continue until the field is within approximately 100 gauss of the desired value, at which timethe magnet is set to the precise field value requested.

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6.3 No Overshoot ModeIf hysteresis measurements are being made, it will be important that the sample not be
exposed to these field oscillations. The oscillations can be suppressed by selecting the No
Overshoot mode for the magnet under Magnet Charging Mode in the Set Parameters
menu (F4) in the MPMS software control system. When the No Overshoot mode is used,
the magnet will require a longer settling time.

Even when the No Overshoot mode is used, measurements can normally still be madeimmediately following a field change because the MPMS control system can compensate forrather large background drifts in the SQUID detector. Magnetic field drift will normallyappear in the data as a linear background which can be subtracted when the magnetic
moment of the sample is calculated. Hence, when the SQUID "Autoranging" is enabled in
the MPMS software control system, the SQUID detector will automatically switch to a lesssensitive range to accommodate the background drift.

Note: If the autoranging function is turned off, be sure that the SQUID detector range issufficiently insensitive to accommodate the background drift. If it is not, the ·data will
be invalid because the SQUID detector will saturate during the measurement in whichclipping the data occurs.

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Quantum Design

MPMS Hardware Reference Manual

6.4 High and Low Resolution Mode
When setting fields below 5000 gauss, the control system will automatically switch thecurrent sense resistor to a larger value (if the high resolution is enabled), providing field
resolution of .approximately 0.1 gauss, compared to the system's normal field resolution of
1.0 gauss. When enabled, the system will automatically select the high resolution mode
whenever possible. Note, however, that the relay that selects the high or low resolution
mode cannot be switched unless the current from the power supply is set to zero. When thehigh resolution mode is enabled, it will be selected as follows:1.

When the magnitudes of both the original field and the newly specified field are lessthan 5000 gauss.

2.

When the magnitude of the new field to be set is less than 5000 gauss and the Oscillate
mode is selected. In this case, when the oscillations become small enough to beaccommodated with the high resolution mode selected, the current will be momentarily
set to zero, the magnet control system will be switched to the high resolution mode,and the oscillations continued.

3.

When the "No Overshoot" mode is selected and the original field in the magnet isgreater than 5000 gauss, the high resolution mode will not be selected, since this would
require that the field be set to zero at some point during the field change - possibly inviolation of the "No Overshoot" requirement.

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Chapter Six:

Magnetic Field Control

6-7

6.5 Updating the Last Magnetic Field Stored in the Magnet
Another feature available in the MPMS magnet control system allows you to update theinformation in the 1822 MPMS controller and the MPMS HP operating system regarding thelast field stored in the magnet. From the magnet charging sequence described in section 6.1,
it is clear that the MPMS control system must "remember" the current that was last stored in
the magnet so the correct current from the power supply can be preset before energizing thepersistent switch heater. If the power supply is set to the wrong current when the persistentswitch is driven normal, the voltage across the switch will exceed the trigger voltage of theprotective diodes, and current will begin to flow through the diodes. When this occurs, thecmTent which was stored in the magnet will be dissipated in the diodes as the magnet is
rapidly discharged.
Under normal operating conditions, the 1822 MPMS controller stores the value of current
presently stored in the magnet and uses this value when the next field request is received.
However, if power outage occurs while the magnet is charged, the system will experience aPower-On reset, and the information in the 1822 MPMS controller will be lost. When the
HP control system is restarted, the data read from the system status file will be inconsistent
with the information received from the 1822 MPMS controller, and you will be informed ofthe problem during the reinitialization of the HP control system.

a

WARNING!
Be sure that the value of field you specify has the same polarity as
the last-field stored in the magnet. If you specify the field with theincorrect sign, you may physically damage the magnet control system.
Also, the field update operation should be performed immediately on
restarting the system after the power outage has been corrected.

The field information can also be restored using the Update Field in the Utilities (F6) menu.
(See the MPMS Software User's Manual for details of the use of this function.) Note thatneither field update operation at initialization nor in the Utilities menu initiates a change inthe field stored in the magnet- it only informs the 1822 MPMS controller and the MPMS
software control system that the field currently stored is as specified.

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6.6 Direct Control over the Magnet Sequence

CAUTIONAs a final reminder, we want to again caution you against carelessmanipulation of the magnet control system via the Magnet Controls
menu under the Diagnostic Menus (F7). These operations should
only be exercised by someone thoroughly familiar with the MPMS
system and its operation.

In addition to the normal automatic MPMS magnet controls, we have also included thenecessary command structure to allow direct control over the magnet sequence from the
MPMS system control computer. While the individual MPMS controller commands aredelineated in the Model 1822 MPMS Controller User's Manual, most of the specificfunctions are available from the Magnet Controls menu in the MPMS control system as
described in the MPMS Software User's Manual.

6. 7 Magnetic Field Limitations as a Function of the Helium Level
If the liquid helium level becomes too low, it is possible that the superconducting magnet
may quench. To prevent this from happening the liquid helium should be maintained above
the top of the magnet. This corresponds to a liquid helium level of approximately 50% (seeFigure 2-1).
·
If the helium level drops below the top of the magnet the magnet field used should be limited.
Between 40-50%, the maximum field should be limited to 10,000 gauss. Between 30-40%,
the maximum field should be limited to 1,000 gauss. Below 30%, the magnet should not becharged with a magnetic field.

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7-1

Chapter Seven:

Gas Control System

The MPMS gas system controls the gas flow through the cooling annulus to provide cooling for
the MPMS, plays a key role in the active temperature control below the crossover point of about
4.4 Kelvin, and provides the valving and controls for purging the airlock when loading samples.
Figure 7-1 shows a schematic view of the gas control system.

7.1 Description
Cold helium gas or liquid is drawn into the cooling annulus via the variable impedance.
When the system is maintaining a stable temperature, the incoming gas is heated to thetemperature of the sample chamber as it enters the cooling annulus. It then passes up thecooling annulus, through the larger vacuum line connecting the cooling annulus to the
MPMS control console, and through the metering valve (shown as the bias needle valve in
Figure 7-1) to the vacuum pump.
During a high speed cooldown, the proportional flow control valve will be opened, providing
a large gas flow through the cooling annulus. This valve is in parallel with the metering
needle valve which is simply bypassed during this operation.
The proportional valve also is used to fill the helium reservoir (the lower portion of thecooling annulus) with liquid for thermal control below the crossover temperature. The
reservoir is filled by adjusting the pumping speed to the proper rate using the proportional
valve and by holding that rate constant for an appropriate length of time. When properly
adjusted, this will draw liquid through the variable impedance and into the cooling annulus.
After the reservoir has been filled, the variable impedance is closed. The pumping rate canthen be adjusted to control the temperature of the reservoir. Again, the proportional valve
fulfills this function.

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0

~

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...
§
b
0

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r-

en
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.....
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MPMS GAS CONTROL SYSTEM

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MPMS and MPMS, with Low
Temperature Option Only

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SampleAccess

I

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AnnulusI
PressureIr ____ J

External
Gos Service

L-+------I
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Bias Needle
Valve

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Gas Control Unit

Proportional
Flow Control

Cooling
Valve

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Chapter Seven:

Gas Control System

7-3

7.2 Purging the Airlock
The other primary function of the gas system is to purge the airlock prior to opening the
airlock valve and inserting a sample into the sample chamber. The airlock flush valve, theairlock vent valve, and the thermocouple gauge provide this capability. Pressing the PURGEAIRLOCK switch on the front of the MPMS probe, initiates an automatic process in which
the two valves are sequentially opened and closed to purge air from the airlock. The flush
valve is opened first to evacuate the air from the airlock chamber, then the vent valve is
opened allowing helium gas from the dewar to enter the airlock. After a few seconds, thevent valve is again closed, and the flush valve is reopened to purge the airlock. The process
is repeated three times providing a thorough cleansing of the airlock.
At the compl~tion of the purge sequence, the vent valve is left closed and the flush valve
open, while the 1822 MPMS controller monitors the thermocouple gauge to ensure that the
sample chamber pressure is pumped down to the correct pressure. When a pressure of a few
millimeters is reached, the green LED on the front of the MPMS probe labeled READY willlight up indicating that the airlock can now be opened.
·
If the READY LED does not come on after 5 or 10 seconds, there is probably a leak in thesample chamber. There are three o-ring seals beneath the slide-seal assembly that seal thesample chamber when a sample is in the unit. (The slide-seal assembly is the unit that
contains the sliding seals around the sample rod, and is clamped into the top of the sample
transport mechanism when a sample is inserted into the airlock.) If the READY LED does
not light after the valve sequence is completed, open the airlock slightly, then close it again to
initiate the venting operation. After the VENTING LED on the MPMS probe goes out,
remove the slide-seal assembly and check to see if the three o-rings are in place. This is themost likely problem, as the o-rings will occasionally stick to the underside of the slide-seal
assembly when it is removed.

After the airlock purging operation has been completed and the READY LED is on, theairlock flush valve will be left open so that the vacuum pump will be pumping continuouslyon the sample chamber. This will maintain a few millimeters pressure of static helium gas in
the chamber to provide thermal contact between the sample and the walls of the sample
chamber.
When the sample is to be removed from the sample chamber, it is lifted into the airlock andthe airlock valve is closed. The valve closure is automatically detected by the 1822 MPMS
controller. The airlock flush valve is closed, and the vent valve is opened for several
seconds, allowing helium from the dewar to vent the airlock up to atmospheric pressure.
After the VENTING LED on the front of the MPMS probe goes off, the sample can beremoved from the airlock.

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7-4

MPMS Hardware Reference Manual

When there is no sample in the airlock, the airlock plug should be placed in the slide-seal
seat, and the airlock purged. This will keep dust and dirt from contaminating the o-ringseals, and keep any small objects from dropping into the airlock. It will also leave the flush
valve open, which is its deenergized state.

7.3 Attaching an External Helium Source
The toggle valve and access port labeled EXTERNAL GAS SERVICE are located· on the
MPMS gas unit on the front of its control console. Together the toggle valve and gas port
can be used for attaching an external helium source to the system.

7.4 The Check ValveThe check valve shown in Figure 7-1 provides a steady flow of helium gas from the dewar to
the top of the sample transport mechanism. This flow will continuously purge the volume
between the two lip seals in the slide-seal assembly. (The construction of the slide-seal
assembly is discussed in more detail in chapter 5.) The helium gas which leaves the dewar
via this check valve is exhausted from the gas nozzle located on the rear of the sample
transport mechanism. Since the check valve is set for 1/3 psi, compared to the 1 psi setting
for the dewar relief valve on the top plate of the MPMS probe, the nozzle on the sample
transport will be the primary path for helium being vented from the dewar.

7.5 Attaching~ Helium Recovery System

If the system is to be attached to a helium recovery system, two connections are required
during normal operation. The vacuum pump outlet passes through an air filter mounted justinside the rear door of the console. The outlet of the air filter is a gas nozzle to which arecovery line can be attached. An additional recovery line must be attached to the gas nozzle
on the rear of the sample transport mechanism. During helium transfers you may also wish toconnect a third recovery line to the exhaust port of the helium transfer fitting.

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8-1

Chapter Eight:

SQUID Detection System

8.1 Description
The MPMS SQUID detection system comprises the SQUID sensing loops, asuperconducting transformer with an RFI shield, and the SQUID sensor itself with its control
electronics. In addition, the superconducting transformer includes a small heater winding
capable of driving the SQUID input circuit normal to eliminate persistent currents induced in
the pickup loops when changing the field in the MPMS superconducting magnet. A
schematic of the SQUID sensing loops and input circuit is shown in Figure 8-1.
The SQUID detection loops are configured as a highly balanced second-derivative coil set
with a total length of approximately 3 cm. The coils are designed to reject the uniform fieldfrom the superconducting magnet to a precision of approximately 0.1 percent, making the
SQUID detector relatively insensitive to drifts in the magnet following even very large fieldchanges. In fact, in the MPMS control software, no specific provision is made for delaying
measurements following a field change, although you can specify such a delay in thesequence programming menus if you wish to do so. (For more detailed information, see the
MPMS Software User's Manual.)
Signals detected in the second-derivative coils are coupled into the SQUID sensor through asuperconducting RFI isolation transformer with a -3 dB rolloff frequency of about 20 kHz.
This allows the system to operate in very noisy RFI environments without experiencing flux
jumps while sample measurements are being performed. The transformer heater, which isinstalled as part of the superconducting transformer, is designed to drive both sides of thetransformer normal so that all persistent currents in the SQUID input circuit are eliminated.
The heater is turned on during all magnet charging sequences and at the beginning of eachsample measurement (but not between individual scans of a measurement).
The Model 2000 VHF SQUID control electronics unit, mounted on the rear of the dewar
cabinet, is described in detail in its own manual (refer to the manual for a description of its
operation). The Model 1822 MPMS controller contains the signal processing card thatprovide the gain and filter settings. These settings are controlled from the
SQUIDNoltmeter Controls menu under the Diagnostic Menus (F7). This menu isdescribed in the PPMS Software User's Manual, as are the procedures for tuning the SQUID
electronics.

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Quantum Design

MPMS Hardware Reference Manual
LONGITUDINAL SQUID SYSTEM

Model 1822
External
Feedback

Signal
Coil

RF
Bias
Model 2000
SQUID
Amplifier

Isolation
TronsFormer

SecondDerivatian
Detector
Array

Figure 8-1 Longitudinal SQUID System

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Chapter Eight:

SQUID Detection System

8-3

8.2 Transverse Coil Set
The components of the transverse superconducting coil set are almost identical to that of theLongitudinal. The main difference is the configuration of the pickup loop.
The transverse pickup loop is wound orthogonal to the longitudinal pickup in an array. Thisis illustrated in Figure 8-2. As shown, both the longitudinal and transverse pickup loops
share a common center position. This allows for measurement with both axes, without
having to recenter the sample. Measurements for both axes are taken in the same manner, bymoving the sample up through the pickup loop.
Because the transverse pickup loop does contain some longitudinal components, samples
with small transverse moments will give a longitudinal signal when taking a transverse
measurement. Therefore it is recommended that when measuring a sample with thetransverse axis, the sample should have a transverse moment that is 80 percent larger than its
longitudinal signal.
If the sample to be measured does not have a large transverse signal, the measurement canstill be taken. Once the data has been collected, the longitudinal portion of the signal must be
subtracted from the transverse. This can be accomplished using a Fourier Transform
technique.
The transverse option is complete with its own SQUID sensor and associated electronics.
The only difference between the longitudinal and transverse electronics is the address setting
on the associated Model 2000 amplifier. For the longitudinal the address is "O". For thetransverse the address is "1 ".

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8-4

Quantum Design

MPMS Hardware Reference Manual
TRANSVERSE SQUID SYSTEM
Model 1822

External
Feedback

Signal
Coil

RF
Bias
Model 2000
SQUID
Amplifier

Isolation
Transformer

Figure 8-2 Transverse SQUID System

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Chapter Eight:

SQUID Detection System

8-5

8.3 Extended Dynamic Range
The Extended Dynamic Range option allows you to measure a sample with a magnetic
moment that is greater than 300 emu. This is accomplished by reducing the signal from the
pickup coil to a level that is suitable for the SQUID sensor. The amount the signal is reduced
is a constant calibrated factor. After the reduced signal is processed by the SQUID and its
associated electronics, the MPMS control software multiplies the value of the signal by thecalibration factor. The calculated value is the sample moment.
When the pickup coil signal becomes large enough to extend into the higher ranges, theMPMS software and controller will automatically adjust as required. Use of this option
requires no operator action. The actual emu ranges in the extended range will be determinedby the calibration factor for the individual MPMS unit. The default values are shown in
Table 8-1.

Table 8- 1 SQUID Ranges

Sensitivi!Y
Normal Ext. Range(emu)(emaj_

Ran_geComputer ACU.000125.000250.000625.00125.00250.00625
.0125
.0250
.0625
.125
.250
.625
1.250

lx
lx
lx
lx
lOx
lOx
lOx
lOOx
lOOx
lOOx
lOOOx
lOOOx
lOOOx

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1.875
3.750
7.500
18.75037.50075.000187.500
375.000

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(1)
(1)
(1)
(1)
(2)
(2)
(2)
(3)
(3)
(3)

(4)
(4)
(4)

Gain

lOx
5x
2x
lx
5x
2x
lx
5x
2x
lx
5x
2x
lx

Conversion Factor
NormalExt. Range
J..Volts/<Pj
J..Volts/<P)
10.00
5.00
2.50
1.00
.50
.25
.10
.05
.025
.010
.005
.0025
.0010

75.00
30.00
15.00
7.50
3.00
1.50
.75
.30

9-1

Chapter Nine:

Magnet Reset Option

9.1 Description
The Magnet Reset Option allows you to reduce the residual or remnant field that is left in the
superconducting magnet. Because the MPMS measures the current to the magnet and not
the actual magnetic field, there may be some amount of field left in the magnet after
operating at high fields, even though the field indicated is zero.
To reduce the amount of field left in the magnet, the Magnet Reset Option heats a small
portion of the magnet above its superconducting temperature. A chain reaction occurs andthe adjoining portions of the magnet are driven normal. This continues until the entire
magnet has been driven normal and quenches. This will reduce the remnant field to typicallyless than 2 gauss.
In order for this option to function, two criteria must first be met as follows:1.
2.

The helium level in the dewar must be greater than 50 percent. This is to ensure thatthe magnet is completely covered by the liquid helium.
The magnetic field must be set between 25000 and 35000 gauss.

A single reset of the magnet will use approximately 1 liter of liquid helium. The entire reset,
including initiation, reset, and recooling of the magnet will take approximately 3.5 minutes.
It is not recommended that the magnet be reset often. The recommended technique is toperform a series of high field experiments, then reset the magnet to perform low field
experiments. By lumping the high and low field experiments together, the number of resets
can be minimized.

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10-1

Chapter Ten:

Manual Insertion Utility Probe

Description
The Manual Insertion Utility Probe (MIUP) is a multifunction sample mounting platform.
The sample mount is constructed of copper to provide a good thermal connection of thesample to the sample space. A microconnector at the top of the MIUP is connected by 5
sets of phosphor-bronze wire to the 10 terminal board at the bottom. Each wire can carrya maximum of 100 mamps. Pin #1 is designated by an arrow on the microconnector, andis connected to the uppermost terminal on the terminal board. Pin #2 is the pin across the
microconnector from pin #1 and connects to the net terminal on the terminal board.

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Index1802 Bridge; 1-1, 1-5, 3-1, 4-10, 4-12,
4-14, 4-15
1822 Controller; 1-1, 1-5, 2-1, 4-10, 4-12,
4-14, 6-1, 6-3, 6-7, 6-8, 7-3, 8-1

A
airlock; 5-6, 5-7, 5-9, 7-1, 7-3, 7-4
amplifier, Model 2000 rf; 1-6, 1-13, 1-14,
8-1, 8-3

cclamp assembly; 5-3
computer; 1-1, 1-5, 1-6, 1-8, 1-10, 2-3, 3-1,
3-2,3-4,4-1,4-5,4-ll,4-12,6-3
control console cabinet; 1-1, 1-5, 1-8, 1-10, 1-11,
1-15, 3-1, 4-3, 7-1, 7-4
cooldown, high speed; 4-8
cooling annulus; 4-1, 4-7, 7-1

D
dewar
helium; 1-1, 1-11, 2-1, 2-3, 2-4, 3-1 to 3-4,
4-10, 5-1, 7-3, 7-4
nitrogen-shielded; 1-15

E
Extended Dynamic Range Option (EDR); 8-5G
gas handling system; 1-6

Hheaters; 4-7, 4-10, 4-13, 4-15
chamber;4-1,4-14
gas; 4-1, 4-3, 4-7, 4-14
heliumconsumption; 1-8
level; 2-1 to 2-3
safety; 2-4, 2-5transfering; 1-8, 3-1 to 3-4, 7-4
helium recovery systems; 1-8, 3-2, 3-4, 5-1, 7-4

I
impedance; 4-10, 4-12, 7-1
impedance tube; 3-2

Llevel meter; 2-1
lip seal; 5-1, 5-3, 5-4, 5-7, 7-4

Mmagnet; 1-1, 1-6, 2-1, 2-3, 3-2, 3-3, 6-1 to 6-8, 8-1
current; 6-1
high resolution; 6-1, 6-6
low resolution; 6-1, 6-6
mode
no overshoot mode; 6-5
oscillate mode; 6-4
operation; 6-1 to 6-3
persistent mode; 6-1, 6-4
reset; 6-1, 6-7
safety; 1-15 to 1-17
voltage; 6-7
Magnet Reset Option; 9-1
magnetic field; 1-9, 1-17, 3-3, 5-8, 6-1, 6-4, 6-8, 9-1
setting; 6-3, 6-8
Manual Insertion Utility Probe (MIUP); 5-3, 10-1,
10-2

0o-ring; 5-1
location; 1-13, 3-1, 3-3, 5-7, 7-3
maintenance; 5-9, 7-4

ppersistent switch; 6-1, 6-7
pickup coil; 8-5Power Distrubution Unit (PDU); 1-13, 3-1
probe; 1-1, 1-5, 1-8, 1-14, 2-1, 2-3, 3-2, 5-7, 7-3, 7-4
handling; 1-10, 1-13, 1-16
installation; 3-1
pumping lines; 3-1

R
reservoir; 4-1, 4-4, 4-8, 4-10 to 4-13, 7-1

ssafety; 1-10, 1-15 to 1-17, 2-4, 2-5
sample chamber; 4-1, 4-3, 4-4, 4-7 to 4-9, 4-14, 5-1,
5-3, 5-5 to 5-7, 5-9, 7-1, 7-3
sample holder; 5-4 to 5-6, 5-9
sample rod; 1-1, 1-8, 5-1, 5-3, 5-4, 5-6, 5-7, 7-3
sample space; 4-10, 5-3, 10-1
sample support assembly; 5-1, 5-2
sample translator; 1-6