Aml catalogue 13

Catalogue
Arun Microelectronics LimitedArun Microelectronics LimitedArun Microelectronics Limited
Vacuum Mechatronics
www.arunmicro.com

Arun Microelectronics Ltd
www.arunmicro.com
TSP2 Titanium Sublimation Pump Power Supply
Features
Sublimation pump controller
Sublimation current settable over the range 30 to 55A in increments of 0.1A
Self-timed delay between getter renewal adjustable from 1 minute to 9.9 hours
Suitable for a wide range of cartridges with up to 4 filaments,
85% Ti, 15% Mo filaments from 1.8 to 2.1mm diameter
Sublimation inhibit / trigger function by external switch or relay
Filaments are warmed and cooled gently to avoid thermal shocks. The sublimation current contains
minimal harmonics to reduce the risk of early filament failure due to magnetostrictive stress or
mechanical resonance
Pump current is accurately regulated in order to automatically compensate for mains variations and
pump cable warming
Filaments may be run for degassing at currents between 5 and 25A to prevent overloading the ion pump.
Filaments can be kept warm at the end of a system bake
Indicates open-circuit filament, shorted cable / filament, inhibit and overtemperature
Thermal overload protection
No in-service adjustment is required
2U (88mm) high full-width, steel cased instrument for easy rack-mounting
The TSP2 titanium sublimation pump power supply will controll most pump cartridges with
up to 4 filaments. It regulates the quantity of material sublimated from the filaments,
compensating for changing conditions and eliminating the need for operator attendance or
adjustment.

Arun Microelectronics Ltd.
www.arunmicro.com
10 to 40°C for rated performance. Operation up to 50°C is possible at longer sublimation intervals
i.e. below 10-6 mbar
Operating Temperature
Supply Voltage
Power Consumption
Output Current
220 / 240V (Option H) OR 100 / 110V (Option L), 50Hz or 60Hz, to order
SPECIFICATIONS:
SPECIFICATIONS:
Less than 20 watts when idling, less than 700 watts when sublimating at 55A with a maximum-length cable.
Regulated at 30 to 55A RMS x 0.1A in sublimation, 5 to 25A RMS x 5A in degass.
The output voltage is determined by the cable and cartridge resistance. Maximum output voltage is 9.5V RMS at 45AOutput Voltage
Sublimation period 0.1 to 3 minutes x 0.1 min.. Delay interval 1 to 59 minutes, 1 to 9.9 hours.
Degas time 1 to 99 minutes. All timing is derived from mains supply frequency.Timing
100% at 300w output power and less than 30°C ambient temperature.Output Duty Cycle
Dimensions
Weight
2U high (88mm), full width (483mm) x 366mm deep.
11kg
Order Code
Accessories
TSP2-H Ti. Sublimation pump power supply. 220/240V
Ti. Sublimation pump power supply. 100/110V
6 metre non-bakeable pump lead
6 metre pump lead with 1 metre 200°C
bakeable section
TSP2-L
TSP2L6
TSP2BL6
Fitzalan Road
Arundel
West Sussex BN18 9JS
England.
Tel: +44 (0)1903 884141
Fax: +44 (0)1903 884119
Email: sales@arunmicro.com
AML pursues a policy of continuous product improvement and reserves the right to make detail changes to specifications without consultation.
Unless otherwise stated all specifications are typical and at 25º Celsius, after 1 hour operation. E and OE.
TSP2

Vacuum Gauges
Vacuum Mechatronics
www.arunmicro.com

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NGC2D Process Controller
Features
UHV Dual Bayard-Alpert Ion Gauge Controller
Continuous measurement range: 1000 mBar to 3 x 10-11 mBar range.
Controls 2 Ion gauges (sequentially), 2 Pirani gauges and 1 Capacitance Manometer.
Bright green LED display shows bar-graph or numeric pressure, trend, diagnostics, etc..
Display in mBar, Torr or Pascal. Permanent bar-graph of Pirani pressures.
Simple, guided setup is re-entrant and can be password protected.
Reduced emission current. Instrument can advise optimum current or may be set manually.
Variable Ion gauge sensitivity. Filament in use selectable from front panel
Automatic start of Ion gauge in pump-down and can be interlocked by Pirani or external signal.
Manual and automatic electron-bombardment degas programs.
Integral, variable sensitivity leak detector with audio output on Pirani 1 or Ion gauge.
4 power relays for process control (5A, 240V) flexibly assignable to gauges.
System bakeout program with control of temperature, time & over-pressure limit. Integral
K-thermocouple amplifier.
Automatic control of titanium sublimation pump controller with optional countdown / cancellation
of imminent firing.
RS-232C interface for data-logging and control
Recorder output 1.0 volt/decade.
1U high full-width, steel cased instrument for easy rack-mounting.
Operates from 100V to 240V, 50/60Hz supply.
The NGC2D is a high-accuracy Ion Gauge controller that offers
integrated pressure measurement and process control;
with a large, clear display, an intuitive
user interface and serial
communications.

www.arunmicro.com
Ionization Gauge
AML AIG1xG are recommended. Bayard-Alpert gauges from many other manufacturers are suitable without
adjustment other than sensitivity
Gauge Type
Range
Accuracy and
Repeatability
Gauge Supplies
From 1 x 10-3 to below 3 x 10-11 mB with a UHV gaugehead with tungsten filaments. The low limit is dependent on
gaugehead, cable construction and length and conditions of use. The upper limit is determined by the acceptable
life of the filament and may be extended by the use of thoria or yttria-coated iridium filaments.
SPECIFICATIONS:
SPECIFICATIONS:
Determined principally by the gaugehead: controller errors are much smaller. Emission at 0.5mA is recommended.
Electrometer logarithmic conformance <1% within any decade from 0.1 mA to 10 pA, <5% to 1 mA and <20% to
2 pA at 25ºC incoming air temperature. Slope temperature compensation <0.02% per degree Celsius. Differential
linearity of the 12- bit A to D converter is less than 0.1 LSB. Emission current initial accuracy <2%, stability <1%.
Grid: +200 volts in emission, +500 volts at £60 mA in degas.
Filament: +50 volt bias, 12 volts at ≤4.2 A (Tungsten) ≤2.6 A (Yttria) with filament power limited at > 30 watts.
Pirani Gauge
AML types PVU and PVB.
A constant-voltage bridge circuit reduces contamination at high pressures. AML Pirani gaugeheads may be
exchanged or extension leads may be connected without adjustments being necessary.
Gauge Type
Capacitance Manometer
Capacitance Manometers of any manufacture having a +10 volt full-scale output at 1, 10, 100 or 1000 mBar or Torr
and which are self-powered are suitable. Pressure indication can be in units different to the full-scale units defined
for the Capacitance Manometer.
Gauge Type
General Specifications
Scientific notation or bar-graph displays in mBar, Torr or PascalPressure Display
Operating Temperature
Supply Voltage
Power Consumption
5º to 35º Celsius for specified performance. Incoming air temperature is measured and displayed and operation
is inhibited at >40°C.
100 V to 240 V nominal at 48 to 65 Hz, without adjustment.
<20 watts idling, <75watts in emission.
Dimensions 1U high, full width x 270mm Deep
Order Code
SPECIFICATIONS:Accessories
NGC2D Dual (Sequential) Ion Gauge Controller
UHV Ion Gauge. 2 x Tungsten filaments
UHV Ion Gauge. 2 x Thoria coated filaments
UHV Ion Gauge. 2 x Yttria coated filaments
3, 6 or 9 metre bakeable Ion gauge cable
Pirani Gauge. Non-bakeable with 3m cable
Pirani Gauge. Bakeable with 3m cable
Pirani 10 metre extension cable, non-bakeable
AIG17G
AIG18G
AIG19G
AIGL3 (6) or (9)
PVU3
PVB3
PVX10
Fitzalan Road
Arundel
England.
Tel: +44 (0)1903 884141
Fax: +44 (0)1903 884119
AML pursues a policy of continuous product improvement and reserves the right to make detail changes to specifications without consultation.
Unless otherwise stated all specifications are typical and at 25º Celsius, after 1 hour operation. E and OE.

AIG Ionisation Gauge & Lead
UHV Bayard-Alpert Ion Gaugeheads, leads & filaments
Arun Microelectronics Limited
www.arunmicro.com
AML AIG Issue K
The AML AIG nude ionization gauge is a high-sensitivity UHV Bayard-Alpert gauge covering the
vacuum range of 1x10-3
to 3x10-11
mbar and is intended for electron-bombardment degas. It has
an NW35CF flange with individual glass compression seals, closed-end grid and a choice of fila-
ment materials.
Individual glass compression seal around each feedthrough pin are more economical and
robust than ceramic, resulting in a less expensive and more rugged gaugehead, with the
central collector pin inherently guarded against leakage currents by the grounded bulk of
the flange.
Replaceable twin Tungsten filaments are fitted as standard with Thoria or Yttria-coated
Iridium as an option.
The molybdenum grid has a closed-end, light, rigid structure, resulting in high sensitivity.
The X-Ray-induced electron desorption current at the collector is minimised by geometry
and screening.
Connector pins are gold-plated, shrouded and polarized. Gold plating ensures that oxida-
tion on the air-side cannot occur even after repeated bakeouts.
Maximum bakeout temperature 250°C. Sensitivity 19 per millibar for nitrogen. X-Ray as-
ymptote 3x10-11
millibar.
Emission Degas
Collector +0V +0V
Grid +200V +500V
Filament
bias
+50V +0V
Max.
emission
10mA
10mA W,
60mA Ir
Recommended Operating Conditions
H2O 19 N2
O2 19 CO
H2 9 CO2
He 3 Ne
Ar 24 CH4
Sensitivity, S mbar-1
19
20
27
6
27
Divide S by 100 for Pa-1
. Multiply S by 1.33 for Torr-1

www.arunmicro.com
AML AIG Issue K
AIG17G UHV Bayard-Alpert gauge. Twin tungsten fila-
ments
AIG18G UHV Bayard-Alpert gauge. Twin thoria-coated
iridium filaments
AIG19G UHV Bayard-Alpert gauge. Twin yttria-coated
iridium filaments
AIGL3, (6), (9) 3, (6), (9) metre, screened, bakeable Ion Gauge
Cable.
FIL17 Replacement filament assembly.
Twin tungsten
Ordering Information:
FIL18 Replacement filament assembly.
Twin thoria-coated iridium
FIL19 Replacement filament assembly
Twin yttria –coated iridium
Fitzalan Road
Arundel
England.
Tel: +44 (0)1903 884141
Fax: +44 (0)1903 884119
AML pursues a policy of continuous product improvement and reserves the right to make detail
changes to specifications without consultation. Unless otherwise stated all specifications are typical
and at 25º Celsius, after 1 hour operation. E and OE.
AIGL Gauge Lead.
The AIGL is a 250°C-bakeable lead for use with AIG and similar ionisation gauges connected to AML controllers.
They are available in 3, 6 and 9 metre versions or custom lengths to order. AML use gold-plated connectors ex-
clusively: these are essential for reliable long-term measurement of the ion current after baking.
The cable is rated for the worst-case operating conditions of 50 watt degas with a new tungsten filament during a
200°C bake. This product incorporates a fully screened and guarded collector with >1x1015
insulation. The con-
nector housing is machined from PEEK and the cable clamp is anodized aluminium.
Filament Types.
Filament power varies over the useful life of a filament, due to gradual erosion of bare tungsten or loss of the oxide
coating. In general, Thoria-coated iridium filaments require about one quarter the power of tungsten at mid-life. Yt-
tria has similar properties and runs less than 50°
C hotter in normal emission. Yttria also has better adhesion and
consequently longer life. Oxide-coated filaments absorb water in storage and may require more power initially to
evaporate it.
The filament power supply must be capable of providing high currents to develop adequate power in the low resis-
tance of a cold filament and sufficient voltage to compensate for drops in a long, hot cable. A power-limited supply
of 40 watts capable of providing up to 12 volts and up to 4 amps will drive any AIG17G gauge operating under any
conditions, (including degassing during bakeout at 250°
C) with an AIGL9 lead. AML BA gauge controllers exceed
these requirements and include comprehensive filament protection features.
Replacement Filaments
Replacement filament assemblies are available in tungsten, thoria and Yttria-coated iridium. The assembly is
held by Allen set screws in socket receptacles and a key and replacement screws are provided.

PVU3 & PVB3 Pirani Gaugeheads
Pirani Gaugeheads for use with AML Ion Gauge Controllers
www.arunmicro.com
AML PVU Issue D
Pirani gauges detect the cooling effect of residual gas molecules on a heated filament. The rate of heat
transfer to the gas is related to pressure and causes a change in the electrical resistance of the filament or
the amount of power required to maintain it at constant temperature. The filament is normally connected in
a bridge circuit.
PVU3 is a low-cost non-bakeable gaugehead with an integral 3-metre lead and connector. The feedthroughs
use matched glass-to-metal seals which have better life and leak performance than the epoxy or compression
seals used on other low-cost Pirani gaugeheads. The standard flange is NW16KF.
PVB3 is a UHV-compatible stainless-steel Pirani gauge with an integral 3-metre lead and connector which
can be baked at 200ºC. The standard flange is NW16CF.
PVX10 is a 10 metre extension cable for use with PVU or PVB. These cables extend the Kelvin sensing of
AML controllers, so that the extension does not affect the calibration.
AML Pirani gaugeheads are intended for use in constant-voltage bridge circuits, which reduces the
filament temperature and the rate of filament corrosion or contamination at high pressures.
Range: 200 mbar to 1 x 10-3
millibars.
May be interchanged between any AML NGC / PGC series or equivalent controllers without re-
calibration. Extension cables do not affect the calibration.
Supplied calibrated for vertical installation in dry nitrogen. Internal calibration adjustments enable them
to be used with other orientations and gases.
Materials exposed to the vacuum are stainless steel, nickel-cobalt-iron, glass and tungsten.

www.arunmicro.com
AML PVU Issue D
Ordering Information:
PVU3 Pirani Gauge, non-bakeable, 3m lead. NW16KF
PVB3 Pirani Gauge, bakeable, 3m lead. NW16CF
PVX10 Pirani extension lead, non bakeable, 10 metres
Fitzalan Road
Arundel
West Sussex BN18 9JP
England.
Tel: +44 (0)1903 884141
Fax: +44 (0)1903 884119
AML pursues a policy of continuous product improvement and reserves the right to make detail
changes to specifications without consultation. Unless otherwise stated all specifications are typical
and at 25º Celsius, after 1 hour operation. E and OE.
Gauges are supplied calibrated for dry nitrogen. Calibration instructions are supplied with all gauges. AML Pirani gauges are
intended for use with AML Pressure gauge controllers and 1U-high controllers manufactured by AML for other vendors. Such
controllers may be identified by the AML copyright marks on the printed circuit boards.
PVU2
3000
PVB2
3000

UHV Stepper Motors
Vacuum Mechatronics
www.arunmicro.com

• 1.8° Step angle
• Suitable for use below 1 x 10-10
mBar
• Bakeable to 200°C
• Embedded K type thermocouple
• Operational range -65°C to +175°C
• Custom options available
Model Holding
Torque
mNm
Detent
Torque
mNm
Rotor
Inertia
gcm2
Max.Axial
Force
kgf
Max.
Radial
Force (1)
kgf
Mass
g
Current
Per Phase
A
Phase
Resistance
at 20°C
Phase In-
ductance
mH
D35.1 70 8 10 9 15 190 1.0 4.7 3.8
D42.1 180 8 35 9 15 350 1.0 5.3 6.6
D42.2 360 14 68 9 15 470 1.0 6.8 10.5
D42.3 450 20 102 9 15 610 1.0 8.5 19.5
D57.1 800 30 300 20 60 700 1.0 10.5 27.0
Operating temperature -65°C to +175°C
Bakeout temperature 200°C
Step angle 1.8°
Step angle tolerance 5%
Lead length 1.5m (1) Refer to application note 27 for details
AML stepper motors are speci cally designed for use in UHV environments making them ideally suited for low
speed precision in-vacuum manipulation without the use of particle generating motion feed-throughs. The consid-
erable reduction in mechanical complexity, absence of metal to metal sliding surfaces and low outgassing charac-
teristics make these motors especially suitable for sensitive handling applications
The model D motors are two phase hybrid stepper motors, available in a range of standard sizes and torque rat-
ings. Standard motors provide 200 full steps per revolution and are suitable for use between -65°C to +175°C.
Extended low temperature range (-196°C) versions, radiation hard versions (1 x 107
Gy), shaft modi cations and
hybrid bearings are all available options.
All motors are designed, cleaned and hand assembled to UHV standards in an ISO Class 7 cleanroom.
Fourth Generation Hybrid UHV Stepper Motors
Technical Data
www.arunmicro.com
Ultra High Vacuum Stepper Motors
Version 1.7

Speed vs torque characteristics
The performance shown on these graphs was obtained using an SMD210 drive operating with standard settings
for step division.
SMD210 is a switch-mode, bipolar, current-regulating drive with a nominal source of 67volts, optimised for use with
vacuum motors. At low speed where step division is active the RSS (root sum of squares) of phase current is set
to the nominal current. Over most of the speed range the drive operates in wave mode with nominal set current in
only one energised phase.
Different drives will produce different speed / torque curves. Drives capable of producing a total phase current of
more than 1A RSS may damage the insulation. Drives with signi cantly lower source voltages may result in poor
high speed performance. Use of the embedded thermocouple is essential for motor protection.
3 30 300 3000
200
250
300
350
400
450
500
Speed (rpm)
orque(mNm)
D42.2
1.0A
0.8A
0.6A
0
50
100
150
200
10 100 1000 10000
To
Step Frequency (Hz)
SMD210 Drive, nominal source of 67 Volts.
0.4A
3 30 300 3000
100
150
200
250
Speed (rpm)
orque(mNm)
D42.1
1.0A
0.8A
0.6A
0
50
100
10 100 1000 10000
To
Step Frequency (Hz)
0.4A
100
150
orque(mNm)
D35.1
1.0A
0.8A
0.6A
0
50
10 100 1000 10000
To
Step Frequency (Hz)
0.4A
3 30 300 3000
250
300
350
400
450
500
550
600
650
700
750
800
850
900
Speed (rpm)
Torque(mNm)
D57.1
1.0A
0.8A
0.6A
0.4A
0
50
100
150
200
250
300
10 100 1000 10000
T
Step Frequency (Hz)
3 30 300 3000
200
250
300
350
400
450
500
Speed (rpm)
orque(mNm)
D42.3
1.0A
0.8A
0.6A
0.4A
0
50
100
150
200
10 100 1000 10000
To
Step Frequency (Hz)
www.arunmicro.com

Dimensions
D35.1
Leads terminated with
1.5mm Crimp sockets
ITT Cannon P/N 192990-0090
6.35
1.6
6.34
55±120
38.13
38.07
5.4
47
56
56
47
1.35m
Lead length
5.2 X 4
Mounting Holes
8-off Ø3.3 Pumping ports
on 44.0 PCD. Both Ends.
31
42
42
31
1.35m
Lead length
8 x Ø3.2 Pumping
ports on 31.0 PCD.
Both ends
Motor Length L
D42.1 35
D42.2 49
D42.3 61
2.0
L
21.9
123.0
22.0
5.00
4.98
M3 thread x 8.5
1.5mm crimp sockets
D57.1
D42.X
www.arunmicro.com
4 x Ø3.2 Pumping
ports on 26.0 PCD.
Both ends.
2635
26
1.5m
Lead length
35
1.5mm crimp sockets
27±120
5.00
4.98
2.0
22.0
21.9
M3 thread x 6.5

Fitzalan Road
Arundel
West Sussex
BN18 9JS
Tel: +44 (0)1903 884141
Fax: +44 (0)1903 884119
email: sales@arunmicro.com
Ordering information
Order Code
D35.1 70mNm UHV Stepper Motor
Related products
SMD210 Stepper motor drive
MLF18F 18-way electrical feedthrough
MLF18NBL 3-metre lead, SMD210 to MLF18F
www.arunmicro.com
Bearings:-
Standard motors are tted with open stainless steel bearings lubricated with NyeTorr®
6300 UHV grease.
Option ‘H’ motors have hybrid bearings with silicon nitride ceramic balls, dry lubricated with molybdenum disul de.
Options:-
H. Hybrid ceramic bearings
R. Radiation hardened to 1 x 107
Gy
X. Shaft modi cation. Please provide a sketch of your requirement
C. Cryogenic. Extended operating temperature range. -196°C to +175°C
Order code format
D42.1 R
Order Code
Option
AML pursues a policy of continuous improvement and reserves the right to make detail changes to speci cations without consultation. E and OE.

www.arunmicro.com
SMD210 Stepper Motor Drive
Features
Dual sequential stepper motor controller
• Drives 2 UHV stepper motors sequentially.
• Advanced low-power drive techniques for minimum motor temperature rise and outgassing and maximum
operating time.
• Phase currents can be set from 0.1 to 1A in increments of 0.1A.
• Holding torque can be controlled independently of dynamic torque under program control, to reduce
power.
• Full, half, ÷4, ÷8 step drive modes with automatic transition at user selectable speeds. (Stops on full step
positions only. Micro-stepping used for control of resonance and smoother step transition.)
• Thermocouple amplifiers (type K) for motor temperature indication, protection and control of motor
bakeout.
• RS232C interface for host computer control. Drive programs can be developed and run from the computer
console (Remote Program Control) or downloaded for stand-alone operation (Internal Program Control).
• Motors may be operated manually with the front panel 'STEP' switches or with a joystick. Single-step or
multiple-step operation with smooth acceleration to the selected speed.
• 3 user inputs for interaction with program execution, in addition to two "End of travel" inputs for each
motor.
• 3 user outputs for switching under program control.
• Simple control language has many powerful commands which allow control of all aspects of motion or
position. Conditional operation, loops and jumps are possible.
• 1U high full-width, steel-cased instrument for easy rack-mounting.
• Operates from 100 to 240V, 50/60 Hz supply.
The SMD210 Vacuum-Compatible Stepper Motor Drive is designed to match AML motors. Two
motors may be driven sequentially under host computer control or by an internally stored
program. Manual operation is also available from the front panel switches or a hand-held
joystick.

www.arunmicro.com
Command Summary
Ax Set user output x
Bx Select motor x
b Bakeout selected motor. (175°C)
Cx Clear user output x
Dx Delay x milliseconds, where x is 1 to 65535
E Start execution of a resident program
F Status request. (Busy, ready or error condition)
fx Preset position counter to x. (Sets a reference location at x=0)
G+/-x Go to a defined location x steps from a reference location
g+/- Rotate at preset speed indefinitely in the specified direction
H+/- Go to a location 8 steps inside the specified (EOT+ or EOT-) limit switch
hx,y Set the power reduction parameters (time and phase current after hold time)
In Initialise user output or position counter, as defined by n
J,j Jump to another part of the program
K Abort program execution
Ln Loop through a sequence n times, where n is 1 to 255
M Set the step rates for automatic ministep mode transition
P Enter or exit the programming mode of operation
Q Read the program resident in memory back via RS232C
Tx Define the current slew speed in steps per second, where x is between 10 and the maximum rate
defined by the x command (<6000)
Ux Until. Continue executing the resident program until user input x is“low”
Vx Status request. (Position, user inputs, temperature, software version, dynamic parameters)
Wp Wait for user input p to go“low”before executing the next instruction
Xx,y,z Define the acceleration / retardation parameters, where x is the start speed, y is the maximum
slew speed and z is the number of steps in the acceleration or retardation ramp
Z Reduce speed to zero with the defined retardation
+/-x Rotate x steps in the defined direction, where x is between 1 and 10E+6
SPECIFICATIONS:
Order Code
SPECIFICATIONS:Related products
SMD210 Dual UHV-Compatible Stepper Motor Drive
UHV Compatible Stepper Motors
18-way Feedthrough (CF70)
Lead. SMD210 to MLF18F
C14.1, C17.1, C17.2
MLF18F
MLF18NBL
Fitzalan Road
Arundel
England.
Tel: +44 (0)1903 884141
Fax: +44 (0)1903 884119
AML pursues a policy of continuous product improvement and reserves the right to make detail changes to specifications without consultation. E and OE.
The above is given for information purposes only and is not intended to be a rigorous specification for programming purposes
SMDJOY SMD210 Joystick
Switch-mode current-regulating power stage with a nominal source of 67volts, for bipolar control of 2-phase vacuum
stepper motors.

ARUN MICROELECTRONICS LTD. AML DATA SHEET: MLF Issue G
AML produce a range of wiring accessories to complement their UHV compatible Stepper motors. These
components make installation of motors and other electrical items in vacuum much easier.
MLF18VCF is a 18-way electrical female connector for use in UHV and is bakeable to 250 C. It mates with the
MLF18F feedthrough and the MLF18VCM male connector. The insulated body is PEEK, which has exceptional
outgassing performance. All internal spaces are well-ventilated. The gold-plated, barbed crimp-contacts are attached
to wires before insertion into the body and removed with a standard pin extraction tool, if required. Individual contacts
can be inserted or removed without disturbing others. All AML motors are supplied with this type of crimp-contacts.
MLF18F 18-way feedthrough on a NW35CF (70mm OD) flange which mates with the MLF18VCF UHV connector,
MLF18L lead or MLF18AC air-side connector. It has individual glass compression seals which are much more robust
than ceramic seals and is bakeable to 250 C. The 1.5mm diameter pins are gold-plated. For non-motor applications
observe the maximum ratings of 200V, 5A maximum per pin and 15A maximum per feedthrough.
MLF18NBL is a 3 metre non-bakeable lead for use with AML stepper motor drives and up to 3 motors installed in
one vacuum chamber. It mates with the MLF18F feedthrough.
MLF18AC is the bakeable air side connector which mates with the MLF18F feedthrough. Use this for non-motor
applications or for connecting to other manufacturer’s drives.
MLF18VCM is the male counterpart of MLF18VCF. It is useful for
extension cables or on de-mountable sub assemblies. This item may be
ordered pre-wired to one, two or three vacuum stepper motors.
This document and the designs depicted are the copyright of Arun Microelectronics Ltd. Specifications are subject to change, confirm before ordering. E & OE
AML acknowledges the rights of the owners of all trademarks and registered names.
MLF18VCF
MLF18VCM
CONNECTORS, LEADS, FEEDTHROUGHS AND WIRING ACCESSORIES
FOR UHV STEPPER MOTORS AND OTHER ELECTRICAL VACUUM DEVICES
MLF18VCF MLF18F MLF18L

ARUN MICROELECTRONICS LTD. AML DATA SHEET: MLF Issue G
PWB is a set of 4 PEEK wiring bushes
and M3 x 10mm vented screws. The
four phase wires and thermocouple
from a single motor are a light fit in the
hole in the bush. Use one in situations
where a 'P' clip would be used in air.
The wiring hole may be reamed out
with hand tools for other wiring
applications. Bakeable to 250 C.
Fitzalan Road, Arundel,
West Sussex BN18 9JP, England.
Tel: 01903 884141 Fax: 01903 884119
International Tel: +44 1903 884141
www.arunmicro.com

Mechanisms
Vacuum Mechatronics
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Ultra High Vacuum Translation Stage
• Resolution 5 m or 1 m per full step
mBar
• Directly stackable for XYZ
• Gamma radiation hard to 1x107
Gy
Speci cation Unit LTVL LTVH
Travel mm 50 / 100 / 150 / 200 / 250 50 / 100 / 150 / 200 / 250
Resolution in full step m 5 1
Max. Speed mm/s 15 5
Repeatability m 1 0.2
Load Capacity (Horizontal) kg 20 20
Backlash m Negligible Negligible
Roll, Pitch & Yaw rad <25 <25
Roll, Pitch & Yaw Compliance rad/Nm 33 33
Straightness of Travel m <1.3 m / 100mm <1.3 m / 100mm
Stepper Motor D35.1 D35.1
Vacuum mBar 1 x 10-10
1 x 10-10
Max. Temperature °C 200 200
MTBF (5kg load and 30% duty cycle) hrs 15,000 10,000
AML ultra high vacuum compatible linear translation stages provide long travel with minimum height for loads of up
to several kilograms They have widely spaced ‘V’ roller guides and are useful in simpler compound mechanisms
where torsional loads are small. They are manufactured with UHV compatible material and construction methods
and utilize AML UHV stepper motors.
Smooth motion is provided by a diamond corrected lead screw and a matched, precision lapped nut to ensure
good positional stability and incorporate a preloaded leadscrew nut to eliminate backlash.
LTV UHV Translation Stages
Technical Data
www.arunmicro.comV1.1

Fitzalan Road
Arundel
West Sussex
BN18 9JS
Tel: +44 (0)1903 884141
Fax: +44 (0)1903 884119
Dimensions
Order Code
LTVLxxx Translation stage, 5 m (xxx = travel in mm)
LTVHxxx Translation stage, 1 m (xxx = travel in mm)
Related products
www.arunmicro.com
AML pursues a policy of continuous improvement and reserves
the right to make detail changes to speci cations without con-
sultation. E and OE.
LTVL
LTVH

Ultra High Vacuum Rotation Stage
• Resolution from 0.036° to 0.003° per
full step
mBar
• Directly stackable to AML linear stages
• Open construction
Model CRS10K CRS20K CRS30K CRS60K CRS90K CRS120K
Rotation range 360°
Resolution in full steps 0.036° 0.018° 0.012° 0.006° 0.004° 0.003°
Steps per revolution 10,000 20,000 30,000 60,000 90,000 120,000
Maximum loaded speed
1kHz
10sec/rev
1kHz
20sec/rev
1kHz
30sec/rev
2kHz
30sec/rev
2kHz
45sec/rev
2kHz
60sec/rev
Load capacity Vertical 1kg
Load capacity Horizontal 10kg
Backlash (Unloaded) Less than resolution
Vacuum 1 x 10-10
Max.Temperature 200°C
Motor D35.1
Weight, including motor 640g 710g 710g 940g 940g 940g
AML ultra high vacuum compatible rotation stages are intended for intermittent rotation of balanced loads or as
a precision gearbox. They are manufactured with UHV compatible material and construction methods and utilize
AML D35.1 UHV stepper motors.
The CRS10K/20K/30K can be mounted directly on AML LTV translation stages or stacked on another CRS without
additional hardware. Standard xing - hole patterns are provided on the side “B”, base “A” and rotating table “C”
CRS UHV Rotation Stages
Technical Data
www.arunmicro.comV7.0
As standard CRS rotational stages are supplied lubricated with Nyetorr® 6300 low-vapour pressure (6 x 10-12
mbar) grease. Dry lubrication with molybdenum disul de is available as an alternative option but this will reduce
the expected life of the worm wheel to <500 hours of motion.

Fitzalan Road
Arundel
West Sussex
BN18 9JS
Tel: +44 (0)1903 884141
Fax: +44 (0)1903 884119
Dimensions
Order Code
CRSxxK Rotation stage
Related products
LTVxxL Translation stage, 1 m (xxx = travel in mm)
www.arunmicro.com
AML pursues a policy of continuous improvement and reserves
the right to make detail changes to speci cations without con-
sultation. E and OE.
CRS10K CRS20K CRS30K
CRS60K CRS90K CRS120K

Application Notes
Vacuum Mechatronics
www.arunmicro.com

Page | 1
ARUN MICROELECTRONICS Ltd.
Application notes for Vacuum Compatible Stepper Motors
V4.2
Page
1 Index
2 Operation of stepper motors in vacuum
2 The vacuum environment
2 Temperature rise
3 Outgassing
3 Baking vacuum systems containing motors
3 Corona discharges
3 Low-temperature operation
3 The magnetic environment
4 Adverse chemical environments
4 Care and maintenance
4 Bearing damage
4 Debris inside the motor
4 Overheating
5 Design of mechanisms for use with vacuum compatible stepper motors
5 Rotation (position control)
5 Rotation (speed control)
5 Translation
6 Linear guides
6 Reduction gearing
6 Bearings
7 Resonances
7 The effect of load inertia, friction and drive characteristics
7 Control of resonance

Page | 2
OPERATION OF STEPPER MOTORS IN VACUUM
It is assumed that the reader is familiar with the production of UHV and the handling of UHV
components.
This note does not attempt to describe the theory of operation of hybrid stepper motors.
The vacuum environment.
The successful application of vacuum stepper motors requires an appreciation of their thermal as well
as their mechanical properties. Compared to motors operated in air the available cooling means for
motors in vacuum are much less effective, and until development of the B-series motors continuous
operation was difficult to achieve.
Operation at low temperature improves the outgassing performance of motors. For this reason
minimum running times and motor currents should always be pursued. Selection of the largest motor
possible for the application will result in longer running times, lower motor temperature and lowest
outgassing. This is because of the larger mass and higher efficiency of larger motors.
Stepping motors only perform useful work while the load is moving. This may only be for a period of a
few milliseconds for each step. Users of the SMD210 drive will find the 'h' command may be used to
reduce the phase currents after each step and produce a holding torque which is intermediate
between the pullout torque and the detent torque, with a consequential reduction of power.
At low speeds the torque of a motor is roughly proportional to the phase current but the motor power
is proportional to the square of the current. Where the load inertia dominates the dynamics of the
system it is often possible to reduce the phase current, provided the motor is accelerated more
slowly.
Many applications that appear to require continuous running, for example substrate rotation for
ensuring uniformity of deposition or implantation, can be equally well performed by intermittent short
periods of stepping at low duty cycle. This will reduce the temperature rise.
Where intermittent motion is required design mechanisms with balanced loads whenever possible, to
eliminate the torque required to hold them stationary. Alternatively, increase the static friction in the
system or add reduction gearing so that the motor detent torque will hold position without power.
Maximum efficiency of AML motors is achieved between 500Hz and 1 kHz full-step rate using the
SMD210 drive.
Temperature rise.
The maximum recommended running temperature of AML motors is 175 Celsius, as measured by
the embedded type K thermocouple. Take care to ensure that any measuring equipment connected
to the thermocouple is not affected by the high electrical noise environment within the motor under
drive
Irreversible deterioration of the winding insulation will begin to occur above 230 and the motor may
subsequently produce larger amounts of gas, even at lower temperatures.
The temperature rise at step frequencies above 1kHz will progressively reduce with a typical drive,
which will be unable to establish the set phase current during the step period.
Continuous running with low outgassing can readily be achieved at medium phase currents. Run
times at higher currents can be increased by additional heatsinking at the flanged end of the motor.
The predicted temperature rise will be increased if radiation from other sources within the vacuum
chamber is incident on the motor. Screening may be necessary.

Page | 3
Outgassing.
Newly-installed motors will outgas, mainly due to water-vapour retention in polyimide. As this material
is microporous the water is released rapidly and the rate will subside after a few hours. The rate may
be accelerated by running the motor to self-heat it.
Baking vacuum systems containing motors.
Vacuum-baking of AML Motors at up to 200 Celsius is permissible, and a 24-hour bake at this
temperature will normally reduce the outgassing to its minimum, provided there is pumping capacity
of 100 litres at the site of the motor. Outgassing test-chambers with limited conductance between
measuring points will require baking for several days or weeks to fully outgas a motor.
Motors are typically operated at some distance from the chamber walls, which is where heat is
applied and the bakeout temperature is most often controlled. If the thermal conductance from the
chamber to the motor is low the motor may not reach the desired temperature. Fortunately, the motor
thermocouple allows its temperature to be monitored and controlled to ensure adequate degassing.
If the temperature indicated by the motor thermocouple during bakeout is not high enough when the
bakeout period is well advanced it may be increased to 175 by applying drive power. The preferred
method of doing this is by using the SMD210 "b" command. This energises both phases and keeps
the motor stationary in a half-step position. Power is supplied until the indicated temperature reaches
175 C and is then removed. Power will be re-applied if the temperature falls to 165 C during
execution of the "b" command. Keeping the motor hot by this means while the rest of the vacuum
system cools is recommended, as this will prevent condensation on the motor. This is important,
since the motor is likely to run hotter than the chamber in most applications.
Where internal infra-red heaters are used for bakeout it is advisable to shield the motor from direct
radiation and to achieve the desired temperature during bakeout by running the motor.
Corona discharges
Switchmode stepper motor drives have source voltages of up to 100 volts which may be sufficient to
produce a discharge at high pressure. This is most likely to occur on adjacent pins of the feedthrough
but un-insulated joins in the motor wiring or small holes in the insulation are other possible sites. The
drive may not be protected against this type of discharge and may be damaged. The insulation
material near a persistent discharge will progressively deteriorate.
Low-temperature operation
Standard AML motors are suitable for operation at -65°C. Low temperature versions are available
suitable for use at -196°C. The leads of the motor will be very brittle at low temperatures and should
not be allowed to flex. The normal mechanical and electrical properties of all materials are recovered
on return to room temperature.
Because the resistance of the windings at low temperatures is small the efficiency of the motor is
much greater than at normal temperatures. A resistance of a few ohms should be connected in
series with each winding, in order to present a normal load to the SMD210. Drives which are voltage
sources and which rely solely on the resistance of the motor to define the phase current should not be
used for low-temperature applications.
The magnetic environment
Motors should not be operated in fields of greater than 50 millitesla (500 gauss), as this will affect the
performance while the field is present. Fields significantly greater than this may cause partial de-
magnetisation of the rotor, reducing the torque. Demagnetised motors can be restored by AML.
The leakage field of a motor is of the order of 1 microtesla (10 milligauss) at 10 cm from the centre of
the motor in an axial direction and is present when the motor is not powered. Under drive an
alternating component is added at the step frequency and its harmonics up to a few kHz. The field is
easy to screen with Mumetal or similar high-permeability foil at the sides of the motor, but is more
difficult around the projection of the shaft. Early consideration of the interaction of stray fields on
nearby equipment is recommended.

Page | 4
Adverse chemical environments
AML stepper motors are specified for use in clean UHV although they are often used in deposition
systems. Where it is possible to screen the motor from the line of sight of the deposition source this
should be done. Where chemical vapours are being used careful consideration of the effect on the
motor materials will be required. AML are generally unable to answer on the effect of exotic
chemicals but may be able to provide sample materials for test. The materials used, in approximate
descending order of exposed surface area are:
Polyimide
Diamond-like carbon
Stainless steel 440, 304, 316, 303
Silicon steel
Samarium Cobalt
Poly ether ether ketone (PEEK) 450G
Alumina ceramic
Silicon nitride ceramic
Silver
Fluorinated ethylene polymer (FEP). (Not used on radiation-hard motors.)
Copper
Chromel/Alumel (Chromel and Alumel are registered trade marks of Hoskins Manufacturing Co..)
Care and Maintenance of VCSMs.
VCSMs are inherently robust and have only a single moving component consisting of a simple rotor
assembly, supported on ball bearings. The maximum speed of this type of motor is very low so that
the bearings have an extremely long predicted service life in vacuum. There are no commutators, slip
rings or any other components having sliding contact between surfaces. Given reasonable care in
handling there will be no need for any maintenance.
Stepper motors should not be disassembled as this partially demagnetises the permanent magnet in
the rotor and permanently reduces the torque.
Vacuum motors must be de-magnetised before dis-assembly and re-magnetised and cleaned after
repair. For these reasons motors with faults will need to be returned to AML for repair. The notes
below offer guidance on the avoidance of the most common problems and diagnostic advice.
Debris inside the motor.
Foreign material can enter the motor via the pumping holes and gaps in the bearings. Particles of
magnetic materials are particularly likely to be attracted through the pumping holes and they
eventually migrate into the gap between the rotor and stator. They usually cause the rotor to stick at
one or more points per revolution and can often only be felt when rotating in a specific direction.
Fortunately, the larger motors have enough torque to grind them into a dust.
Overheating
Motors which have been heated to 230 C will produce a much greater gas load thereafter, although
their electromechanical performance may not be affected. Rewinding is practical provided the
windings are not discoloured and the vacuum performance will be subsequently improved. If the
windings are darker than a golden-brown colour the motor will not be repairable. In extreme cases
the insulating material will ablate and deposit itself as a yellow powder inside the motor case and on
any cool surfaces in line with the pumping holes.
Motors can overheat extremely quickly in vacuum. This is very unlikely to happen with a properly-
connected SMD210 drive. Never use a drive capable of providing more than 1 amp of phase current
and ensure that the drive current is removed as soon as the indicated temperature exceeds 175 C.

Page | 5
DESIGN OF MECHANISMS FOR USE WITH VACUUM COMPATIBLE STEPPER
MOTORS (VCSMs)
The following section is an introduction to this topic and is intended to indicate the major mechanical and
vacuum considerations for various types of mechanisms. A working knowledge of mechanics and
vacuum construction techniques is assumed. AML supply a range of standard mechanisms which can
be customised and also design special mechanisms and components.
Rotation ( Position Control ).
The load inertia coupled to the motor shaft should ideally be small compared to the rotor inertia of the
motor. Load inertia up to two or three times that of the motor can be driven, without significant difference
to the maximum start speed and acceleration which is achieved by the unloaded motor. Load inertia of
around ten times that of the motor can be driven with absolute synchronism, provided care is taken over
specifying the ministep and acceleration parameters. Larger inertia loads should be driven through
reduction gearing.
Significant loads should have their centre of gravity on their axis of rotation, unless they are rotating in a
horizontal plane.
Angular resolution at the motor shaft is limited to a single step of 1.8 . The actual rest position within the
step is determined mainly by the load friction and any torque imposed by the load on the motor at rest. If
the rotor position is displaced from the nominal step position the restoring torque increases
approximately in proportion to sin(100 x ) . The maximum torque at the half step position is either the
detent torque or the holding torque, depending on whether the motor is powered at rest. If the static
friction and any torque due to an unbalanced load are known, this allows the rest position error to be
estimated using the above approximation. The friction within the motor bearings is very low, so that a
completely unloaded D42.2 motor will normally settle within 0.2 of the desired position if brought
suddenly to rest from full stepping at 300Hz.
Angular resolution may be improved by reduction gearing: this is discussed below.
Increasing angular resolution by step division is not recommended for vacuum applications, since the
motor must be continually powered to maintain the ministep position. The absolute improvement which
could be gained by this method is small because of the increased significance of the uncertainty in the
rest position.
Rotation ( Speed Control ).
In some applications the precise position of a rotating load is not important or can be deduced by other
means but the speed of rotation may need to be controlled very precisely. Beam choppers and sample
rotators for control of deposition uniformity are applications of this type. An increased load inertia may
be desirable to smooth out the stepping action of the motor. Loads of up to about 1000 times the inertia
of the motor can be controlled by using long acceleration ramps. Some steps may be lost during
acceleration and retardation of such loads, but precise synchronism at constant stepping frequency is
easily achieved and recognised.
Significant rotating loads should be balanced, at least to the extent that the torque presented to the
motor shaft is less than the detent torque of the motor. The motor torque requirement will then be
dominated by that required to accelerate the load.
Translation.
Translation may be produced by a leadscrew and nut, wire-and-drum or rack-and-pinion mechanisms.
The choice depends on the precision, length of travel, force and speed required.

Page | 6
Leadscrew-based translators are capable of exerting forces of kilograms with resolutions of a few
microns per step. Accurate leadscrews are practical up to 300 mm long. With anti-backlash gearing
between the motor and leadscrew, a resolution of one micron is practical. Anti-backlash nuts are not
normally necessary for vertical motions. If a conventional nut is used with the leadscrew the load will be
dominated by friction, especially if there is a reduction gear between the lead screw and the motor shaft
which reduces the reflected load inertia. Because of the lubrication restrictions and the slow speeds of
UHV mechanisms the static friction is usually much more significant than dynamic friction. The optimum
material for nuts is phosphor bronze and for lead screws is stainless steel with a diamond-like coating
(DLC). DLC has a very low coefficient of friction in vacuum. Burnishing or sputtering a layer of pure
Molybdenum Disulphide on the leadscrew may be useful in reducing friction and wear. The typical
coefficient of friction between these materials is 0.1 and typical efficiencies are 40% with ground
trapezoidal threads. The gas load generated by frictional heating of the leadscrew is usually somewhat
less than that of the motor. This may be reduced by changing to either a Molybdenum Disilicide or
Tungsten Disilicide leadscrew coating.
For short translators with resolutions of a few microns AML can supply motors with integral leadscrews
formed on an extended motor shaft. This eliminates the need for a coupling arrangement and for the
additional bearings which would be required to support a separate leadscrew.
Recirculating ball nuts for vacuum use are available. These offer much higher efficiencies but at very
high cost. They produce a very low gas load due to their low friction and can be used to exert forces of
tens of kilograms. They can be loaded with selected balls to reduce backlash to an extremely low level.
The form of the associated lead screw is special and longer lengths are available.
The frictional losses in drum or rack drives are lower than in conventional leadscrew drives and
considerations of inertia usually dominate. Rack and pinion drives are suitable for travel up to a few
hundred millimetres and wire-and drum mechanisms may be made several metres long. The
repeatability and backlash of all these alternative translation drives are much worse than with screw-
driven schemes.
Linear guides.
Low-cost translation mechanisms can use simple bushes running on ground stainless-steel rods. A
variety of carbon-reinforced polymer materials, such as PEEK, are suitable for the bushes, although
these are more expensive than phosphor bronze.
'V' groove rollers and tracks and crossed-roller guides are suitable for more accurate translators. The
former have the advantage of being practical to 1 metre and have minimal overall length for a given
travel. Crossed-roller slides are more rigid and can support larger loads, but at higher cost. Both types
have preload adjustments. 'V' rollers have smaller load-bearing surfaces and only have a rolling contact
at a single point and are consequently liable to greater wear if heavily loaded.
Reduction Gearing.
The inertia of loads coupled by reduction gearing is reduced at the motor in proportion to the square of
the reduction ratio. Where reduction gearing is used for load matching, the spur gear meshing with the
motor pinion will normally dominate the load inertia and it is important to keep its diameter small. Anti-
backlash gears and standard pinions should be used in the gear train to damp any resonances in the
mechanism. Gears for use in UHV should be designed for low friction without lubrication and with
dissimilar materials in contact to avoid cold-welding. Nitrogen ion-implantation of the rolling surfaces or
complete Titanium Nitride coating of gears are effective means of achieving this and other desirable
properties in all-stainless-steel gear trains.
Bearings.
Bearings for use in UHV should be unshielded and have a stainless steel cage and race. The balls
should be either stainless steel coated with some other material or solid ceramic. As an alternative, all-
stainless bearings having a PTFE composite component in the race (which is designed to transfer to the
balls) are also suitable.

Page | 7
RESONANCES
The most common application problems with Stepper motors are concerned with resonances.
Stepper motors are classic second-order systems and have one or more natural resonant frequencies.
These are normally in the 50 - 100Hz region for unloaded motors. Operation at step rates around these
frequencies will excite the resonances, resulting in very low output torques and erratic stepping. Another
set of resonances can occur in the 1 - 2kHz region, but these do not normally present any practical
problems.
The effects of load inertia, friction and drive characteristics.
The primary (lower) resonant frequency cannot be
stated with any precision, since it is modified by
the friction and inertia of the load, the temperature
of the motor and by the characteristics of the drive.
Coupling a load inertia reduces the resonant
frequency and decreases the damping factor.
Load friction increases damping. Because the
drive circuits of the SMD210 produce a controlled
phase current this produces heavy damping.
Drives which are voltage sources and which rely
on the motor winding and other resistance to
define the current have a lower damping factor.
The effect of changing the damping on the single
step response of the motor is shown in the
diagram.
Control of Resonance.
The simplest method of controlling resonances is to avoid operation of the motor close to the resonant
frequencies. It is usually possible to start a motor at rates in excess of 300Hz if the load inertia is small,
thereby completely avoiding the primary resonance. Resonances are not usually a problem when the
motor speed is accelerating or retarding through the resonance frequency region. The SMD210 allows
independent selection of the starting speed and the number of steps in an acceleration profile.
If it is necessary to operate at slow speeds or with large load inertia the step division feature of the
SMD210 (ministep) helps. It effectively increases the stepping rate by the step division factor and
reduces the amplitude of the transients that excite the resonances. This is shown in the diagram below.
Because both phases are energised in ministepping there are some other processes of interchange of
energy between the windings which do not occur in the single step mode and these increase the
damping factor.
In particularly difficult cases modifying the step
frequencies at which transitions of the step divisions
(ministep modes) occur can be useful.
Be careful not to specify step division at excessive
frequency, as this reduces the available torque. The
frequency of step division is the product of the step
frequency and the number of ministeps in a full step.
As a general guide, 500Hz is the maximum useful
limit.
A typical motor response to a single step and to a
single step subdivided into eight ministeps is shown
in the diagram.

ARUN MICROELECTRONICS Ltd.
APPLICATION NOTE No 11, Issue D, March 2004
C-SERIES MOTOR VACUUM PERFORMANCE
Some remarkable improvements in the outgassing performance of AML vacuum-compatible stepper
motors have been achieved in the last year. Most of these have resulted from a reduction in the
temperature rise of the windings, although the outgassing from most of the metal surfaces has also been
reduced by new surface treatments.
Experimental determination.
The motor was suspended in a 400 litre sec-1
(nominal) ion-pumped UHV system equipped with a Hiden
(HAL1000) RGA and AML Bayard-Alpert ( AIG17 + PGC2) and Inverted Magnetron ( AMG10 + PGC4D
) ionisation gauges and controllers. The motor was driven by an AML SMD2 drive. The system was
pumped down and baked at 200 C for 24 hours. During the period in which the system cooled close to
ambient temperature the motor was run at 1 Amp phase current using the SMD2 'Bake' program. This
program controls the motor winding temperature with a setpoint of 175 C, and a hysteresis of around
20 , using drive current to self-heat both windings. The motor was then switched off to allow the system
to attain its base pressure of 4 x 10-10
millibar.
In order to ensure that the motor was adequately degassed the SMD2 'Bake' program was run again.
After an initial rapid rise in temperature this produced a temperature oscillation with an initial period of
about 40 seconds, with a synchronous oscillation in the system pressure as the drive power was
switched on and off. The excursions in pressure and the steady pressure on which they were
superposed reduced to a steady minimum over a few hours, showing that the motor was substantially
outgassed.
The motor was then run continuously for long periods at various smaller phase currents, in order to allow
its temperature to stabilise at a number of points in the range between 50 and 175 C. The total and
partial pressures were then measured.
Results.
The only significant outgassing products were Hydrogen
(90%) and Carbon Monoxide (10%). All other peaks
in the spectrum were below 1% of the Hydrogen
peak height and were characteristic of the system
and independent of the motor temperature.
The derived outgassing rates for the C17.1 motor
with respect to temperature are shown in the graph
opposite.
The outgassing rates of the three sizes of motors
were found to be very similar, with a 2:1 spread.
Since this variation is well within the measurement
errors and the variation from unit-to-unit, the curve
may be used for all types.
From the outgassing rate curve it can readily be seen that operation of a motor at the lowest possible
temperature will be beneficial in reducing the gas load it produces. For example, operation at 100 C will
produce about 10% of the gas compared to operation at 140 C. Selection of the largest possible motor
for a given power requirement will result in the lowest temperature rise.

Estimating the gas load and pump capacity.
A simple application of the rate data will give a very conservative estimate of either the required pumping
rate, S, or the ultimate pressure, Pu, for a given pump.
1. Select the minimum motor phase current which will provide the required motor torque and speed.
2. Use the winding temperature graph on the last page of this note to predict the approximate
temperature rise.
3. Use the outgassing rate curve to estimate the gas load, Q.
4. Derive the result required from Q = S. Pu
Improving the vacuum performance.
In practical situations the temperature rise is somewhat smaller than predicted, giving a substantially
smaller gas load. An appreciation of the factors affecting temperature rise allows users to tailor their
applications for minimum outgassing. The relative importance of these factors depends on the type of
application: those which require continuous operation of the motor being the most challenging.
Since the curves of motor temperature were derived with minimal heatsinking, they are conservative in
predicting temperature rise in real applications. It is very easy to reduce equilibrium temperatures of
100 C and over by 30 to 40 by relatively simple means, such as mounting the motor on a plate or
mechanism. Additional heatsinking has little effect on the curves before some
tens of minutes heating, because the transient thermal impedance of the motor is not reduced.
The temperature curves were obtained with both motor phases being driven with a steady direct current,
which is only representative of low-frequency stepping. Since the motor windings are inductive, it takes
a finite time to establish a current in them and this delay begins to become significant at stepping rates of
a few hundred Hertz. The effect is that the average winding current is progressively less than the set
current at increasing speeds. This means that a motor running at faster than a few hundred steps per
second reaches a lower final temperature than predicted. Beyond about 2kHz the reduction is dramatic,
however, the available torque is much reduced.
Wherever possible applications should be designed so that the load may be held in position by the
detent torque of the motor, so that power may be removed between periods of motion.
The power output of the motor is proportional to the product of the output torque and the step frequency.
At low step frequencies each step is taken in a few milliseconds, after which no useful work is done,
although power continues to be dissipated. The effect of this is that the electromechanical efficiency of
the motor increases with speed until other factors reduce it, reaching a peak between about 500Hz to
1kHz. Operation in this range of speeds will, therefore, minimise the temperature rise for a given power
output. Where gearing is involved, as in most mechanisms, this is in any case the optimum range of
speeds for mechanical reasons.
For slow speed applications the SMD2 drive allows the phase current to be reduced after each step.
This increases the efficiency at low speeds.
For many applications motion is intermittent, with relatively short periods of motion and long periods of
rest (low duty-cycle ). Provided the temperature rise during each cycle is small it is valid to multiply the
phase current by the duty-cycle to estimate an effective phase current. If interpolation between the
curves is required, it should be remembered that the heat dissipated in the motor is proportional to the
square of the phase current.

APPLICATION NOTE No 28, Issue 2 , February 2011
Magnetic leakage fields of AML stepper motors.
AML stepper motors are hybrid types and contain an axially-magnetised permanent magnet in the rotor. D-series
motors are magnetised with the north-seeking pole at the flanged end of the motor. A small proportion of the total
magnetic flux leaks out of the motor, which behaves as a very weak bar magnet. The leakage fields of typical
samples are shown below. These were measured inside a cylindrical magnetic shield with its axis at right angles
to the horizontal component of the earth's magnetic field, which was 0.75μT at the test location. The screening
became ineffective at displacements of 150mm along the motor axis.
D35.1 D42.1 D57.1
Flux density μT Flux density μT Flux density μT
Disp. mm On axis On
side
Disp. mm On axis On side Disp. mm On axis On side
40 50 15 40 40 20 40 n/a 100
60 16 5.5 60 13 8 60 90 40
80 6 2.2 80 5 3 80 30 16
100 2.8 1.1 100 3 1.5 100 16 8
120 1.8 0.6 120 2 0.8 120 11 4
140 1.2 0.3 140 1.4 0.4 140 6 2
Under drive conditions the magnetic field is modulated by an alternating field at the stepping frequency. This is
not usually as significant as the steady field, for a combination of reasons. The amplitude of the stepping-
frequency field reduces with increasing step frequency and is only comparable to the steady field below a few
hundred Hz. At low step rates it is normal (for mechanical reasons) to use ministepping, which produces a
sinusoidal flux waveform. Above a few hundred Hz it is normal to use full-step drive, which attempts to produce a
rectangular flux waveform. However, the filtering action of the winding inductance progressively reduces the
amplitudes of all frequency-components of the field above a few hundred Hz so that the alternating component of
the leakage field at stepping frequency can be considered sinusoidal for all practical purposes. Most modern
stepper motor drives achieve current-regulation in the windings with a switching action, which also modulates the
magnetic leakage field. For SMD210 the switching frequency is 22kHz. The amplitude of this is usually very small
compared to the steady and step-frequency components of the field, typically less than 10%. In most situations the
switching is disabled for the first few milliseconds after each step and is therefore not present at all above step
rates of 500Hz. Stepping motors achieve their greatest electromechanical efficiency between 500Hz and 1kHz
step rates and it is standard practice to design motorised vacuum mechanisms to slew at these rates, in order to
minimise the total energy input and hence the outgassing. It is fortunate that this also reduces the alternating
components of the leakage flux.
Vacuum motorised mechanisms should be designed to hold their rest position without the need for the motors to be
powered. This is desirable for a number of reasons, including the reduction of outgassing. If the analysis or
process within the vacuum system is only active when the mechanism is stationary then the alternating
components of leakage fields need not be considered.
The axial fields of motors are about three times greater than the radial fields at a given displacement. This, and the
presence of the shaft means that the fields can be screened more easily at the sides of the motors. Where
possible, the optimum orientation for the motor is with the shaft at right angles to the line between the motor and
the point where the field is to be minimised and at the maximum displacement. If there are several motors in the
mechanism some field-cancellation can be achieved by mounting them in pairs, aligning their axes in opposing
directions. Where motors are to be screened using Mumetal or other material it is more effective to place the
screens much closer to the motors than to the volume where the field is to be minimised. Where significant
torques and minimal leakage flux are required in the same installation it is better to use D35 or D42 motors and
reduction gears than D57 motors.
END.

APPLICATION NOTE No 27, Issue 2 , July 2010
Axial and Radial loads on AML stepper motor bearings.
AML stepper motors are fitted with two bearings, which support the rotor at each end of the housing. They are
extremely reliable in clean vacuum situations and have useful service lives of decades with low imposed loading.
The two principal causes of failure are both due to misuse: break-up of the ball cage due to ingress of
contaminants or damage due to extreme shock loads such as are caused by dropping the motor on its shaft end.
Axial and radial loads imposed on the motor should be avoided where possible by the design of the mechanism to
which the motor is applied. Loads comparable to the bearing ratings will shorten their lives in unpredictable ways.
It will usually be more convenient to replace bearings in a mechanism than in a motor, which has to be de-
magnetised, cleaned, re-magnetised and baked during any service.
Axial loads.
The bearing at the opposite end to the principal mounting face of the motor is preloaded against the motor end cap
by a spring. The free travel of the spring is about 0.3mm and is fully exercised by a force of 2½kg against the shaft
end. It is important to design linear mechanisms so that this free travel is not added to the backlash in the
mechanism. This can be achieved by preload springs, gravity or by decoupling the motor from the load by gearing.
Linear mechanisms with leadscrews can exert considerable axial forces if they are stalled against rigid end stops.
All AML mechanisms are designed with vernier stops, which stall the motor directly, avoiding this potential problem.
If there is any possibility of a linear mechanism crashing into rigid obstructions it may be necessary to use torque-
limiting to reduce the resulting force. If a linear mechanism stalls due to excessive friction no additional axial load
is imposed on the leadscrew.
For all AML motors direct axial loads of greater than 10kg are not recommended.
Radial loads.
Radial loads on motors arise in two main ways. The first is a simple cantilever extension on the shaft, where the
forces on the bearings can be easily calculated by reference to drawing Q47015, which is appended. Note that the
radial forces on the bearings are magnified by the extension acting as a lever. The second arises in linear
mechanisms where the leadscrew or other extension is directly coupled to the motor shaft and supported or
constrained by a nut or bearing. Any misalignments will give rise to significant radial forces on the motor bearings.
For all AML motors direct radial loads of greater than 10kg are not recommended.

Vacuum Mechanisms from AML
Arun Microelectronics Ltd. (AML) design and manufacture automated precision
mechanisms for use in UHV, using well-proven vacuum-compatible stepper motors.
AML motors have been manufactured and applied
since 1986 and are a mature and accepted UHV
technology. Thousands of motors are in regular
use. AML have unrivalled experience in the
application of VCSMs to mechanisms, with several
hundred succesful designs completed. There are
standard ranges of linear mechanisms and rotation
stages, although most mechanisms supplied are
customised to some extent.
Application areas.
Stepper motor–based mechanisms should not be
regarded merely as replacements for those based
on other techniques, since they offer specific
advantages and are suitable for applications not
addressable by other means. The advantages of
internally motorised mechanisms are that the
number and range of motions, rigidity, accuracy,
repeatability, speed, reliability and crosstalk
between motions are much better than is possible
with motion feedthroughs. Where there are
several axes, or if the range of linear motion
exceeds a few centimetres, or if the sample is
large or heavy then stepper motors offer price as
well as performance advantages. The main
application areas are in clean vacuum systems,
where the magnetic leakage fields of motors (a few
microtesla) are not significant. These include
sample transfer and sample scanning for surface
analysis, mass analysis, ellipsometry, radioisotope
dating, MBE, electron channelling, Rutherford
Backscattering, deposition uniformity control, beam
chopping, cluster-processing and VUV/X-ray
monochromators.
AML vacuum mechanisms are not economic in
non-vacuum applications.

Position control.
When driven correctly, stepper motors are inherently self-encoding digital devices.
Provided the recommended speeds and accelerations are not exceeded then
desired and actual positions remain exactly synchronised. There is no need for
expensive encoders, other feedback devices or limit switches or the inconvenient
wiring and feedthroughs that they need. A convenient reference location is
provided for each axis so that any location on each axis can be achieved by
execution of a single command by an SMD2 controller. Position information is
maintained in the SMD2, even in the absence of power, and there is normally no
need to re-establish the reference locations after an initial setup.
Speed Control.
The speed of rotation of a stepping motor is precisely controlled by the frequency
of its drive: there is no slip or other uncertainty and no feedback devices are
necessary. Above a few hundred Hz the stepping action of an unloaded motor is
smoothed by the low-pass filtering of the kinetic energy stored in its rotor. The
use of step division at lower speeds smooths the motion further and increases the
damping factor.
Vernier stops.
Stepper motors may be stalled indefinitely without damage. AML mechanisms are
designed so that they can be driven into their mechanical end-stops without
affecting their performance in any way. The range of uncertainty in the position of
an end-stop may be reduced by fitting a vernier stop. These are arranged so that a
pin attached to the output plate of
the mechanism moves into the plane
of a radial arm attached to the motor
shaft. The position at which this
stalls the motor has a range of
uncertainty of three steps, which
can often be reduced to a single
step. The repeatability of positions
is usually more important than
absolute position and this is typically less than a single step. Usually it will not be
necessary to re-establish the end-stop position after installation and commissioning
is complete. Vernier stops are inexpensive and effective.
Range of motion.
A practical maximum length of travel for linear mechanisms using leadscrews is
300mm. For longer travels, belt or wire drives are appropriate, but these have
lower resolution. For rotation mechanisms with position-control, the maximum
range may be restricted to slightly more than 360°. This limitation is necessary to
ensure that the wiring from any sample-connection, heating device or other
motorised stage mounted on the rotation stage can be brought out. Most rotation
stages in stacked multi-axis mechanisms will require much less than 360° range: it
is important not to over-specify range of rotation as this increases cost.
1μm / step
1.8º / step

Resolution
Resolutions of 1 micron or 1 millidegree per step are easily achieved. For linear
mechanisms, specifying 4 micron resolution minimises the cost. For rotation
stages the optimum resolution is determined by the available space and load-
matching considerations. Specifying the coarsest resolution acceptable will reduce
the cost but better-than-specified resolution may be offered because of loading.
Because a stepping motor is a digital device, the motion resulting from a single
step has a defined tolerance, usually about 5% of a single step at the shaft of an
unloaded motor. The motion resulting from any number of steps still has an overall
tolerance of a fraction of a single step. Step division is not a satisfactory way of
increasing resolution.
Repeatability
Repeatability of any position at constant temperature and approached in a
consistent way is normally better than the resolution. Wherever possible, thermal
expansion of the mechanism is equalised about the centre of travel. Thermal
expansion of leadscrews of linear mechanisms due to self-heating may need to be
considered where there is a very high duty-cycle motion. Thermally decoupling the
motor from the leadscrew will reduce this effect by a large factor in low-resolution
applications. AML will advise in specific cases.
Backlash.
Most motorised mechanisms are supplied with active backlash-control means
fitted. Backlash is usually negligible, compared to resolution. The orientation of all
axes with respect to gravity is significant in controlling backlash. In some cases
gravity alone may be used to control backlash, reducing complexity and mechanical
loading, although in other cases it may present challenges. For example, rotation
of loads whose center of gravity is offset from the axis may result in a reversal of
static torque: such cases can usually be avoided by careful analysis and design.
Crosstalk.
Multi-axis mechanisms based on multiple motion feedthroughs through the
chamber wall incorporate universal and sliding joints to couple to compound
mechanisms. This inevitably leads to crosstalk between motions and large
backlash, both of which are negligible in mechanisms with internal motors.
Stability.
Hybrid stepper motors have a detent torque (without drive current) of about 10%
of their rated torque. AML design mechanisms so that the combination of detent
torque, static friction and gearing is sufficent to maintain the position of each axis
with no movement when the phase current is removed. Position information is
maintained in the SMD2 drive in the absence of power. Where the best stability is
required all sources of vibration must be decoupled from the chamber: this is
particularly important in the case of turbomolecular pumps.

Stacking order.
The stacking order of motions using vacuum motors is relatively unconstrained and
this can lead to considerable advantages and operational convenience. Together
with negligible backlash and crosstalk this makes accurate eucentric goniometers
for large samples practical. Stacking order is an important concept, which is best
illustrated by a typical example. Consider the requirement to illuminate any spot on
a sample with a focused beam, which is fixed with respect to the vacuum
chamber. The angle of incidence of the beam is to be varied over a cone or square
pyramid, whose axis is normal to the sample surface, with its vertex on the
incidence point.
Using an edge-welded
bellows approach, the X
and Y axes of linear
motion usually have to be
fixed with respect to the
mounting port. This
means that the location of
the incidence point is
convolved with the axes of rotation XR and YR, which define the angle of incidence.
The motion of the point of incidence across the sample is not the same as that of
the X Y stage and it moves if the angle of incidence is changed. Because of the
convolution of rotation and translation it will be necessary to have a Z motion along
the axis of the port to restore the point of incidence to the focus of the beam. If
the axis of the mounting port is not accurately aligned to the axis of the beam then
it may be necessary to have a port-aligner.
Using vacuum motors the
XY axes are fixed on the
sample surface and the
rotation axes are the
same. Therefore, if the
angle of incidence is
changed the point of
incidence does not
change. The incidence
point moves across the sample surface by exactly the same amount as the XY
motion, regardless of the angle of incidence. Normal incidence and the centre
point of the sample are defined by four numeric addresses (which may be zero) set
into the SMD2 controllers. There is no need for a Z motion or port aligner.
Maximum Speed.
The speed of the output plate of the mechanism is the product of the stepping rate
and the resolution. The maximum slewing speed of a mechanism is dependent on
the load imposed, and the gearing between the motor and the output. The load is
dominated in most cases by the weight of other mechanisms stacked on the
output plate. Lightly loaded mechanisms can slew at >2kHz and the most heavily
loaded will slew at 500Hz stepping rate. Because of the absence of the high loads
due to atmospheric pressure, internally motorised mechanisms can be ten times
faster than those based on edge-welded bellows and motorised externally. With
high-resolution mechanisms translations of a few mm per second and rotations of a
few degrees per second are practical.
FOCUSED BEAM
CONE OF
INCIDENCE
SAMPLE
AXES ON PORT
FOCUSED BEAM
CONE OF
INCIDENCE
SAMPLE
AXES ON SAMPLE SURFACE

Orthogonality and concentricity.
Orthogonality of linear axes will be set to ±0.5° and concentricity of rotations
within 0.2mm. If finer settings are required then micrometer adjustment screws
can be provided together with metrology attachments for adjustment after
installation.
Loads and Forces.
Standard translation mechanisms can exert forces of about 10kg, which is limited
by the leadscrew and nut combination. The rolling resistance of a translation
mechanism is usually a few hundred grams. Mechanisms will usually support
much larger masses than 10kg, depending on the guidance system. The effect of
static torques exerted by offset loads must be considered. Standard rotation
mechanisms are not designed to produce large output torques, so if the axis of
rotation is not vertical it is important to keep the centre of gravity of the load close
to the axis. Custom-designed large-force mechanisms and high-torque reduction
gears can be provided.
Sample heating and cooling.
AML will supply and fit heaters, thermocouples and cooling braids for attachment
to cryostats, as required.
Outgassing and bakeout.
AML motors and mechanisms are designed specifically for UHV, using appropriate
materials, handling and construction techniques. For use in UHV, baking at 175°
to 200°C is essential, after which outgassing rates of the order of 10-8
millibar litre
per motor will be achieved. The actual gas load depends on the duty cycle of the
motions and the phase current of the motors. Mechanisms are designed so that
the motors can be switched off when the load is stationary and most motions can
be swept over their entire range in less than a minute. As a ‘rule of thumb’, 100
litres sec-1
of additional pumping capacity per motor will be necessary to achieve
ultimate UHV.
Sample holders and Sample changing.
De-mountable sample holders can be provided. They can be insulated and have
pluggable electrical connections. Mechanised sample entry via a load-lock is
performed either with a magnetically coupled linear feedthrough or with a
passive mechanism activated by one of the motorised axes or an additional
motorised mechanism. Typical situations are illustrated and discussed in AML
Application Note 30.

Reliability
The only components in UHV stepper motors subject to wear are the bearings,
which have a life of decades in normal service. Where there are moving parts in
rolling contact dissimilar materials and surface treatments are selected to avoid
galling or wear. Aluminium-bronze nuts (used in conjunction with leadscrews)
have a life of several thousand hours of full-speed motion and are easy to
replace. Worm drives are used only when necessary because of space
constraints and are arranged to have low speeds and loadings and to be
accessible for easy replacement. Linear guidance systems are designed to avoid
sliding contacts.
Lubrication.
Sliding surfaces in leadscrews and worm drives are lubricated with NyeTorr TM
5200 synthetic lubricating gel for mechanisms which are not intended to be
baked. Lubrication increases the life of these components. Various dry-film
lubricants and low-friction surface treatments can be used, according to the
requirements of the application.
Space Requirements.
It is very important to consider the realistic space requirements of mechanisms
before designing the chamber to accommodate them. Single axis mechanisms
with light loads can usually be made with an output plate height of 30mm. They
are designed for direct stacking, but where more than three mechanisms are
stacked additional space for increasing the rigidity of the lower stages may be
necessary.
Where space is very restricted, the design costs quickly escalate. For example, the
additional cost of designing a six–axis goniometer to fit a minimal space can easily
exceed the cost of a larger chamber.
Controls, cables and feedthroughs.
Mechanisms are designed for use with, and are normally supplied with SMD2
drives cables and feedthroughs. Usually one MLF18 feedthrough and cable per
three motors and one SMD2 drive per two motors are required. All internal and
external cables are are pluggable onto the electrical feedthroughs. Motors are
wired to intermediate VTB6 terminal blocks fitted near the motors, where
appropriate.

Specification of multi-axis mechanisms
Describe or define:-
1. the application
2. the axes with respect to either the mounting plane or the sample surface, as
appropriate
3. the orientation of the axes and the sample surface at centre-travel with respect
to gravity.
4. the stacking order of motions, if critical
5. the sample size, weight and position of centre of gravity, including any sample
holder
6. the resolution and limits of motion for each axis
7. the maximum duty-cycle of motion for each axis
8. whether there is a requirement for a clear view through the sample or any
cones or other volumes in front of the sample which must remain clear
9. heating, cooling, electric insulation or electric connection to the sample to be
supplied or accommodated
10. the method of sample changing, if any
11. acceptable lubricants
12. the space available
13. the chamber wall temperature in normal operation and in bakeout.
14. any electromagnetic or ionising radiation, electric or magnetic fields or
materials being deposited
15. the base pressure

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