Pfeiffer Vacuum QMA 125 User manual

Operating Instructions
BG 805 988 BE (2004-04) 1
Quadrupole Analyzer
QMA 125

2BG 805 988 BE (2004-04) QMA125.oi
In all communications with Pfeiffer Vacuum, please specify the information given on
the product nameplate.
This document applies to QMA 125, with Faraday cup or 90°off-axis SEM and
Faraday cup and the ion sources described below.
We reserve the right to make technical changes without prior notice.
The QMA 125 analyzers are designed for gas analysis in the high vacuum and ultra
high vacuum range. They are parts of the Pfeiffer Vacuum quadrupole mass spec-
trometry system and may be used only in connection with system components
defined for this purpose. The instructions in this user’s guide and in those of the
accessories must be conscientiously followed.
Product Identification
Validity
Intended Use

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Contents
Product Identification 2
Validity 2
Intended Use 2
1 Safety 5
1.1 Symbols Used 5
1.2 Personnel Qualifications 5
1.3 General Safety Instructions 5
1.4 Liability and Warranty 6
1.5 Training 6
2 Description 7
2.1 System Structure 7
2.2 Ion Sources 7
2.2.1 Axial Beam Ion Source 8
2.2.2 Gas-Tight Ion Source 9
2.2.3 UHV Grid Ion Source 9
2.2.4 Crossbeam Ion Source 9
2.2.5 Cathode Materials 10
2.3 Mass Filter 10
2.4 Ion Detectors 11
2.4.1 Faraday Cup 11
2.4.2 C-SEM 11
2.4.3 SEM 217 Secondary Electron Multiplier With Discrete Dynodes 12
2.4.4 Ion Deflection Unit (For SEM 90° Operation) 13
3 Technical Data 14
4 Installation 16
4.1 Preparation 16
4.2 Installing the Analyzer 17
4.2.1 Mounting Orientation 17
4.3 EP 422 19
4.4 CP 400 19
4.4.1 Removing / Installing the SEM Connector Plate 19
4.5 Electrical Connections 19
5 Start Up 22
5.1 First Time operation 22
5.1.1 Operation With Faraday cup 22
5.1.2 Operation With the C-SEM or SEM 23
5.2 Settings 23
5.2.1 Axial Beam Ion Source (Also Applies to Gas-Tight Version) 24
5.2.2 Grid Ion Source 25
5.2.3 Crossbeam Ion Source 25
5.2.4 C-SEM 26
5.2.5 Analyzer With 90°Off-Axis SEM 26
5.2.6 DEGAS Mode 27
5.3 Operating - and Bakeout Temperatures 27
6 Maintenance 28
6.1 General 28
6.2 Removing and Cleaning the Ion Sources 29
6.2.1 Mounting Tool 30
6.2.2 Axial Beam Ion Source (Also Applies to Gas-Tight Version) 31
6.2.3 Grid Ion Source 32
6.2.4 Crossbeam Ion Source 33
6.3 Removing and Cleaning the Mass Filter 33
6.3.1 Analyzer With Faraday Cup 33
6.3.2 Analyzer With C-SEM 34
6.3.3 Analyzer With 90° SEM 35
6.3.4 Taking Apart the Mass Filter 36
6.3.5 Cleaning the Rod System 37
6.3.6 Cleaning the C-SEM 37
6.3.7 Cleaning the SEM 217 37
7 Repair 38
7.1 Replacing the Filament 39
7.1.1 Axial Beam Ion Source (Also Applies to Gas-Tight Version) 39

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7.1.2 Grid Ion Source 39
7.1.3 Crossbeam Ion Source 40
7.2 Replacing the SEM 217 / C-SEM 41
7.2.1 SEM 217 41
7.2.2 C-SEM 42
7.3 Removing the Connector Housing 42
7.3.1 All Connector Housings Except the Housing for the SEM 217 42
7.3.2 Connector Housing for the 90° off-axis SEM 217 43
7.3.3 Connector Housing SEM 43
7.4 Checks to be Made After Maintenance Work on the Analyzer 43
8 Accessories 44
9 Spare Parts 44
10 Storage 44
11 Returning the Product 45
12 Disposal 45
13 Anhang 45
A: Literatur 45
B: Electrical Connections and Pin Assignment 46
Declaration of Contamination 50
For cross-references within this document, the symbol (→XY) is used, for cross-
references to further documents, listed under literature, the symbol (→[Z]).

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1 Safety
DANGER
Information on preventing any kind of physical injury.
WARNING
Information on preventing extensive equipment and environmental damage.
Caution
Information on correct handling or use. Disregard can lead to malfunctions or mi-
nor equipment damage.
Skilled personnel
All work described in this document may only be carried out by persons who
have suitable technical training and the necessary experience or who have been
instructed by the operator of the product.
• Adhere to the applicable regulations and take the necessary precautions for the
process media used.
Consider possible reactions between the materials (→10, 15) and the pro-
cess media.
Consider possible reactions (e.g. explosion) of the process media due to the
heat generated by the product.
• Adhere to the forwarding regulations and prescriptions of the countries and
forwarding agencies concerned and attach the necessary warning labels in the
appropriate places.
• In case of toxic or explosive gases being measured by the QMA125, exhaust
gases have to be treated according to the regulations.
• Adhere to the applicable regulations and take the necessary precautions for all
work you are going to do and consider the safety instructions in this document.
• The instructions in the user’s guides of all system components must be con-
scientiously followed.
• Before beginning to work, find out whether any vacuum components are con-
taminated. Adhere to the relevant regulations and take the necessary precau-
tions when handling contaminated parts.
• Communicate the safety instructions to all other users.
1.1 Symbols Used
1.2 Personnel
Qualifications
1.3 General Safety
Instructions
Process media
Safety measures

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Pfeiffer Vacuum assumes no liability and the warranty becomes null and void if the
operator or third parties
• disregard the information in this document
• use the product in a non-conforming manner
• make any kind of changes (modifications, alterations etc.) to the product
• use the product with accessories not listed in the corresponding product docu-
mentation.
The end-user assumes the responsibility in conjunction with the process media
used.
Caution
Caution: Inappropriate use
Inappropriate use leads to contamination and/or damage of the cath-
ode or the secondary electron multiplier.
Adhere to the instructions in this document in order to avoid damages
not covered by liability and warranty.
Training
Pfeiffer Vacuum offers application, operating and maintenance courses for the
best use of this product. Please contact your local Pfeiffer Vacuum representa-
tive.
1.4 Liability and Warranty
1.5 Training

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2 Description
A quadrupole analyzer consists of:
• Ion source
• Rod system (mass filter)
• Ion detector (cup)
• Connector housing
• Ion deflection unit 1)
EP controller
CC 125
SEM or
C-SEM
QMA 125
QME 125
EP 422
Controller
QMS 422
EP
Ion source Mass filter (90°-Ion-
deflection
unit) 1)
Faraday collector
Ion source
supply
IS 125 RF-generator
RF 125
High-
voltage
supply
HV 125
1) For optional SEM 90° operation
All the ion sources contain the following elements:
• One or two electron sources con-
sisting of a filament (1), a device to
accelerate (3), focus (2) and collect
the emitted electrons
• An appropriate ion optics system that
focusses the ions formed in the for-
mation chamber so that they enter
the mass filter (7)
1
2
3
7
The following types of ion sources are available:
• Axial beam-ion source
• Gas-tight model of the-axial beam ion source
• UHV grid-ion source
• Crossbeam-ion source
Ions are formed in collisions between the electrons emitted by the filament and the
molecules in the gas mixture being analyzed.
2.1 System Structure
2.2 Ion Sources
General

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All the ion sources suited for use in the QMA 125 analyzer feature the following:
• The voltage between the formation chamber and the mass analyzer entry ap-
erture (ground) is higher than that between the formation chamber and the fila-
ment. This arrangement also results in the filament being at a positive potential
with reference to ground. To assure that the ions in the mass filter can be de-
celerated to the required low energy of several eV, the axis potential of the
mass filter may only be a few volts lower than that of the formation chamber.
This type of arrangement is advantageous from two points of view:
• No electrons are emitted into the environment where they could cause interfer-
ence to other units.
• The ions pass through the deleterious transitional fields between the grounded
entry aperture and the mass filter fast enough to minimize the effect of these
fields.
The illustration shows the basic design
of an axial beam ion source.
The acceleration voltage between the
filament emitting the electrons (1) and
the ionization chamber through which
the electrons flow (4) is ≈100 V. The
Wehnelt electrode (ground potential)
directs the electron flow in the ionization
chamber. In the formation chamber the
electrons collide with the gas molecules
present, forming ions. The formation
chamber is at 150 V. The grounded
entry aperture extracts the ions thus
formed and directs them into the mass
filter.
Three types of filament are available:
• Rhenium (Re), tungsten (W) and
yttria oxide iridium (YOx-Ir).
1
4
2
5
3
This type of ion source supplies ions with narrow energy distribution and low ve-
locity components perpendicular to the axis, which achieves good resolution and
high sensitivity with that particular mass filter. This is a result of the strong collima-
tion of the electron beam. The disadvantage of this arrangement is the high elec-
tron space charge which can cause non linear behavior at pressures in the
10−5mbar range. Lower emission is indicated if this should be avoided.
The relatively open design of this ion source guarantees low error of measurement
caused by self-degassing and surface reactions.
2.2.1 Axial Beam Ion Source

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The design of the gas-tight ion source corresponds closely to that of the axial beam
ion source. In the gas-tight source the grid is placed over a smaller aperture to
allow entry of the electrons. The gas to be analyzed is fed directly into the ion
source formation chamber (4) via a metal capillary at ground potential (6) and an
insulating intermediate piece (5). Two ceramic rings (7) and a disk (3) are used as
the sealing elements. Conductance is ≈1 l/s. The filament is outside the sealed
chamber in an area of high conductance where it interferes little with the gas to be
analyzed.
4
3
56
7
The open design of this ion source is
especially suited for residual gas analy-
sis in ultra high vacuum.
The selection of the construction materi-
als used, its design and the degassing
possibilities it offers through electron
bombardment result in very low outgas-
sing and desorption rates during opera-
tion.
The electrons emitted by the ring ca-
thode (2) are accelerated to the grid (1).
The ions formed through collisions with
electrons inside the grid area are ex-
tracted through the grounded mass filter
entry aperture and into the mass filter
through the central aperture opening.
The filament is divided into two parts
with a center contact.
The filament is made of tungsten (W).
2
1
The cross beam ion source has two filaments that can be operated one at a time as
required. They allow the direct entry of molecular beams perpendicular and parallel
to the system axis. It is highly linear. Compared to the axial beam ion source, how-
ever, its sensitivity is lower.
2.2.2 Gas-Tight Ion Source
2.2.3 UHV Grid Ion Source
2.2.4 Crossbeam Ion Source

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The electrons emitted by one of the two
filaments (1) are accelerated into the
formation chamber (2) perpenticular to
the system axis. The emitted electrons
are collimated by the Wehnelt electrode
(3) mounted on the filament block and
connected to the filament at one end.
The extraction aperture (4) generates a
weak electrical field in the formation
chamber which is used to extract the
ions. The lens (5) focusses the ions into
the rod system. The design of the ion
source does not allow it to be operated
at fixed voltages applied to the extrac-
tion aperture and the ion optics i.e. the
applied voltages must be continuously
adjustable (→25).
Three types of filaments are available:
• Rhenium (Re), tungsten (W) and
yttria oxide iridium (YOx-Ir).
2
3
1
4
5
The ion sources can be equipped with cathodes (filaments) which are best suited
for the planned application. Certain cathode materials are not available for all
source types (→44).
In contrast to tungsten, rhenium does not form any stable carbides, since no CO2
cycle as known with W takes place. In addition, Re is not embrittled by recrys-
tallization.
The vapor pressure of Re is approximately 50 times higher than that of W, and the
filament life is accordingly shorter. Getter effects may occur due to the evaporation.
Tungsten is used when the higher vapor pressure of Re is undesirable, when a
long filament life is required, or when the advantages of Re are not important to the
application.
Since yttria oxide iridium does not form oxides, it is quite insensitive to air inrushes.
The emission temperature of yttria oxide iridium filaments is lower than that of Re
and W filaments. Reactions with residual gas are weaker because the ion source
temperature remains low.
The contamination may be stronger in the presence of substances with a low vapor
pressure.
The mass filter consists of four cylindrical rods. They must be precisely aligned for
proper functioning (mass separation, stability, and sensitivity). An adjustable radio
frequency voltage and a superposed DC voltage proportional to it are applied to the
rod system. The trajectories of the ions in the electrical field inside the rod system
are dependent on the m/e (mass/charge) ratio of the particular ion. Only ions of one
specific m/e ration reach the detector while all other ions are filtered out.
2.2.5 Cathode Materials
Rhenium (Re)
Tungsten (W)
Yttria oxide Iridium (YO
x
-Ir)
2.3 Mass Filter