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EQP

EQP
M A S S

A N D

E N E R G Y

A N A LY S E R

F O R

P L A S M A

D I A G N O S T I C S

INTRODUCTION

A P P L I C AT I O N

The EQP mass spectrometer combines an
electrostatic sector energy analyser with a high
performance quadrupole mass filter in an instrument
designed for plasma diagnostics. The EQP can
acquire the mass spectra and energy distributions of
neutrals, radicals and ions (positive and negative).
Trends in intensity can be plotted against time. Fast
acquisition modes mean that transients and
afterglows can be studied.

The EQP operates in one of two modes:
PI Mode: Ions can be directly extracted from the
plasma. These plasma ions (PI) are formed in the
plasma, extracted from it and focussed into the
energy filter.

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C O N F I G U R AT I O N
The EQP mass spectrometer is a PC controlled
instrument for plasma analysis and diagnostics.
Spectra can be easily acquired, stored and
manipulated using Windows™ based MASsoft
software. The EQP uses an electrostatic sector field
energy analyser for ion energy analysis, the
transmission and resolution of this device making it
the instrument of choice for plasma diagnostics.

6

EI Mode: Neutrals and radicals are sampled from the
plasma and then ionised at low pressure (10 -5 torr)
inside an electron impact (EI) ion source. The energy
of the ionising electrons may be controlled to enable
the detection of radicals. Ions from the electron beam
source are first transferred and then focussed directly
into the energy filter.

7
1.80E+05

1.60E+05
m/e=41
1.40E+05

4

5mT, 15W
Capacitively coupled

1.20E+05

1.00E+05

1

2

3
8.00E+04

m/e=19
(x4)

6.00E+04

4.00E+04
m/e=28
2.00E+04

0.00E+00
0

20

40

60

80

Energy (eV)

The energy analyser is followed by a triple section
quadrupole mass filter. A pulse counting electron
multiplier, which can be configured for positive or
negative ion operation is used for ion detection. This
detector provides high sensitivity, fast response and
high dynamic range (>10 10) for plasma ions and
neutrals. Mass range options are 300 amu, 510 amu,
1000 amu and 2500 amu. An energy range of 100 eV
is standard and 1000 eV optional to provide the user
with analysis of positive and negative ions and
appearance potential spectra for radicals analysis.
Signal gating by direct TTL input is also available with
gating resolution to 1 µs for afterglow studies.

9
5
O P E R AT I O N
The main constituents of the EQP Plasma Diagnostic
System are as follows:
1 Sampling Orifice: The sampling orifice is removable and is

mounted at the probe tip. This can be configured in various ways
which include grounded, dc biased, heated, RF driven and
electrically floating.
2 Electron Impact (EI) Ion Source: The electron impact ion source

is not used in plasma ion mode. In EI mode the dual filament
electron impact ion source is used to create ions from the neutral
species which diffuse into the ion source. The selected filament
emits electrons with an energy defined by the variable electron
energy. The electron emission current is the current collected by
the ion source cage, this current is measured and used to stabilise
the filament current. The electron emission current can be user
controlled to enable the user to find the ionisation potential of
radicals and neutrals. The electron energy is scanned with other
parameters fixed and intensity is plotted against electron energy.

3 Transfer Ion Optics: A drift space and lens are used

7 Quadrupole Mass Filter: The quadrupole mass filter is constructed

to transfer the EI or PI ions to the input of the energy
filter. In this drift space ions are accelerated to a
higher kinetic energy. A lens is used to match the ion
(EI or PI) into the energy filter.

in three sections, prefilter (RF only), main filter (RF and dc) and post
filter (RF only). The mass filter resolution is electronically controlled
and is software adjustable to allow the user to easily optimise all
parameters according to the requirements of the experiment.

4 Quadrupole Lens: To focus ions in both x and y

8 Detector: The detector is an off axis mounted continuous dynode

Typical IEDs are shown in the figures. The spectra
show the energy distributions for mass resolved ions
as indicated. The energy range of the instrument is
100 eV with an option for 1000 eV operation. The
energy spectrum can be used to determine the
plasma potential, tailing on the energy spectra is an
indication of collisions taking place in the plasma
sheath.

directions into the energy filter.
5 Energy Filter: The energy filter is a 45° sector field

electrostatic energy analyser fitted with fringe field
correction apertures. The analyser radius is 75 mm
providing high resolution and transmission. Energy
pass band is 0.5 eV with 100% transmission within
pass band.
6 Decelerating Lens: A decelerating lens reduces the

kinetic energy of the ion beam before injection into
the quadrupole mass filter.

electron multiplier which operates in the pulse counting mode. The
three variables which control the detector are: (i) the first dynode
voltage - this is the voltage on the front of the detector; (ii) the
multiplier HT - this is the voltage across the detector; and (iii) a
discriminator which is used to set a counting threshold on the pulse
output from the multiplier. The pulses from the detector can be
electronically gated so that only pulses detected during the gate
time are included in the energy or mass spectra. This feature can be
used to study afterglows and transient phenomena.
9 Differential Pump Port: High conductance ConFlat® port for turbo

pump mounting.

140000

10V

120000
100000

15V

80000

5V

60000

20V

40000

Appl Bias=25V

20000
0V

0
0

5

10

15

20

25

30

35

e n e rg y : V

Hiden Analytical Ltd.
420 Europa Boulevard
Warrington
WA5 7UN
England

Tel: +44 (0) 1925 445225
Fax: +44(0) 1925 416518
Email: info@hiden.co.uk
Web: www.HidenAnalytical.com

quadrupoles for advanced science