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A small universal quadrupole mass spectrometer
Vacuum~volume33/number 1/2/pages 69 to 70/1983
0042-207X/83/010069-02$03.00/0 Pergamon Press Ltd
Printed in Great Britain P24
A small universal quadrupole mass spectrometer I Borecz, S Boh6tka, J G~I, L Kiss, G Langer, A PaSI and R M Kov6cs, Institute of Nuclear Research of the Hungarian Academy of Sciences, Bem tdr 18/c, Debrecen, t-14001, Hungary
A universal quadrupole mass spectrometer (type Q6OU) has been constructed for genera/laboratory and industrial purposes. Its 10 cm long analyser rod system, 1-60 amu mass range and 4 . 10 -'= A mbar-' sensitivity make it a good residual gas analyser. Due to its high mass resolution it can be used also as an analytical instrument. It works as a total pressure gauge, too, saving the cost of a vacuum gauge. The bias and gain controls and audio-frequency signal generator of its leak detection unit complete the quadrupole as a sensitive multi-test gas leak detector.
Introduction The need for a versatile residual gas analyser in vacuum technical laboratories is well known. We have had experience in constructing quadrupole mass spectrometers for various analytical purposes 1'2 and recently an urgent need for building a small instrument for general use appeared. The Q60U was constructed to fulfil the following functions: mass spectrometric analysis in a restricted mass range, total pressure measurement, leak detection. A more or less similar conception can be recognized in some commercially available mass spectrometers, too, e.g. AIG-50, Centronic; AGA-100 MUX, UTI; Quadruvac Q 100, Leybold Heraeus. The mass spectrometer The analyser head has a cylindrical, electron bombardment ion source and molybdenum rods of 100 mm length and of 8 mm dia. The rods are fixed into two ceramic rings at ¼ of their length. The position of the ceramic rings along the rods yields the least mechanical distortion in the rod system. The analyser head is mounted on a ND130 flange. The dimensions are not so small as that of an ion gauge but, as was proved in practice, the higher resolution and sensitivity is preferable to the small dimensions. The detector is a Faraday cup. The electronics consists of a control unit, RF-generator and electrometer amplifier. The RF-generator is attached to the analyser head with a short cable to reduce the power consumption. The high frequency is 3.25 MHz. This high frequency guarantees good resolution and high sensitivity. The mode ofoperation (mass spectrometer, vacuum gauge, leak detector) and the important parameters can be selected on the control unit. The main characteristics: Mass range: 1--60 ainu Sensitivity: 4 . 1 0 - " A m b a r - l Resolution: can be set in six steps between A M = 0 . 5 and AM = 1.5 amu at 10% peak height Scan speed: 0.1-300 s Electrometer: 10- 7-10-12 A
A typical spectrum taken with Q60U is shown in Figure 1.
L i-
0
x I00
I
IO
"-~t
, 40 J
3o
20 M,
_
~ 50 ,
,.Xl 60 ,
o.m.u.
Figure 1. A mass spectrum recorded with the Q60U. Vacuum gauge In this mode the ion source parameters are fixed and the whole mass range is swept repeatedly. The output signals of different masses are integrated and the mean value is proportional to the pressure. The pressure reading against a Bayard-Alpert gauge reading is shown in Figure 2. The relation is linear up to about 4 . 1 0 - 5 mbar. Leak detector It is possible to use a quadrupole as a leak detector. For convenience an audio-frequency generator, bias control and a post-amplifier circuit (max gain: 20) is built into the instrument as an additional unit. Setting the mass selector knob on the mass number of the test gas, the variation of this specific peak can be 69
I Berecz, $ Boh~tka, J G~/, L Kiss, G longer, A Paaland R M Kov~cs: A small universal quadrupole mass spectrometer
monitored visually on the front panel meter and acoustically by the frequency change (80 Hz-7.5 Hz) of the audio-frequency generator. The smallest detectable leak on a system pumped with 101 s -1 pumping speed is 5" 10 - j l mbar I s - l . -
../"
E GI
lO_~
/
/ i{~ G
./r
e~
l/
e/
eO Results The Q60U is a reliable small mass spectrometer with total pressure monitor and leak detector units. The high resolution and sensitivity qualify it as an analytical instrument in the 1-60 amu mass range, it is good for routine residual gas analysis, it can measure total pressure, and as a leak detector it can detect not only He but practically any test gases. In this mode both a visual and acoustic monitor are supplied.
oj °
/ $ 0
References I0
I
i6'
I
IIItll[
I
I LIIII11
I
I
I Illll~
io-" ~o-' Boyord oLpert gouge reoding,
I
,o-5
t li[lil]
I~"
tabor
Figure 2. The calibration of the vacuum gauge unit of the Q60U.
70
I Berecz, S Boh/ttka, J G/tl and A Pa~l, ATOMKI Ki~zleminyek, 19, 123 (1977). 2 1 Berecz, S Boh/ttka and G Langer, Proc 8th Int Vac Conor Cannes, Vol lI, 251 (1980).
0042-207X/83/010069-02$03.00/0 Pergamon Press Ltd
Printed in Great Britain P24
A small universal quadrupole mass spectrometer I Borecz, S Boh6tka, J G~I, L Kiss, G Langer, A PaSI and R M Kov6cs, Institute of Nuclear Research of the Hungarian Academy of Sciences, Bem tdr 18/c, Debrecen, t-14001, Hungary
A universal quadrupole mass spectrometer (type Q6OU) has been constructed for genera/laboratory and industrial purposes. Its 10 cm long analyser rod system, 1-60 amu mass range and 4 . 10 -'= A mbar-' sensitivity make it a good residual gas analyser. Due to its high mass resolution it can be used also as an analytical instrument. It works as a total pressure gauge, too, saving the cost of a vacuum gauge. The bias and gain controls and audio-frequency signal generator of its leak detection unit complete the quadrupole as a sensitive multi-test gas leak detector.
Introduction The need for a versatile residual gas analyser in vacuum technical laboratories is well known. We have had experience in constructing quadrupole mass spectrometers for various analytical purposes 1'2 and recently an urgent need for building a small instrument for general use appeared. The Q60U was constructed to fulfil the following functions: mass spectrometric analysis in a restricted mass range, total pressure measurement, leak detection. A more or less similar conception can be recognized in some commercially available mass spectrometers, too, e.g. AIG-50, Centronic; AGA-100 MUX, UTI; Quadruvac Q 100, Leybold Heraeus. The mass spectrometer The analyser head has a cylindrical, electron bombardment ion source and molybdenum rods of 100 mm length and of 8 mm dia. The rods are fixed into two ceramic rings at ¼ of their length. The position of the ceramic rings along the rods yields the least mechanical distortion in the rod system. The analyser head is mounted on a ND130 flange. The dimensions are not so small as that of an ion gauge but, as was proved in practice, the higher resolution and sensitivity is preferable to the small dimensions. The detector is a Faraday cup. The electronics consists of a control unit, RF-generator and electrometer amplifier. The RF-generator is attached to the analyser head with a short cable to reduce the power consumption. The high frequency is 3.25 MHz. This high frequency guarantees good resolution and high sensitivity. The mode ofoperation (mass spectrometer, vacuum gauge, leak detector) and the important parameters can be selected on the control unit. The main characteristics: Mass range: 1--60 ainu Sensitivity: 4 . 1 0 - " A m b a r - l Resolution: can be set in six steps between A M = 0 . 5 and AM = 1.5 amu at 10% peak height Scan speed: 0.1-300 s Electrometer: 10- 7-10-12 A
A typical spectrum taken with Q60U is shown in Figure 1.
L i-
0
x I00
I
IO
"-~t
, 40 J
3o
20 M,
_
~ 50 ,
,.Xl 60 ,
o.m.u.
Figure 1. A mass spectrum recorded with the Q60U. Vacuum gauge In this mode the ion source parameters are fixed and the whole mass range is swept repeatedly. The output signals of different masses are integrated and the mean value is proportional to the pressure. The pressure reading against a Bayard-Alpert gauge reading is shown in Figure 2. The relation is linear up to about 4 . 1 0 - 5 mbar. Leak detector It is possible to use a quadrupole as a leak detector. For convenience an audio-frequency generator, bias control and a post-amplifier circuit (max gain: 20) is built into the instrument as an additional unit. Setting the mass selector knob on the mass number of the test gas, the variation of this specific peak can be 69
I Berecz, $ Boh~tka, J G~/, L Kiss, G longer, A Paaland R M Kov~cs: A small universal quadrupole mass spectrometer
monitored visually on the front panel meter and acoustically by the frequency change (80 Hz-7.5 Hz) of the audio-frequency generator. The smallest detectable leak on a system pumped with 101 s -1 pumping speed is 5" 10 - j l mbar I s - l . -
../"
E GI
lO_~
/
/ i{~ G
./r
e~
l/
e/
eO Results The Q60U is a reliable small mass spectrometer with total pressure monitor and leak detector units. The high resolution and sensitivity qualify it as an analytical instrument in the 1-60 amu mass range, it is good for routine residual gas analysis, it can measure total pressure, and as a leak detector it can detect not only He but practically any test gases. In this mode both a visual and acoustic monitor are supplied.
oj °
/ $ 0
References I0
I
i6'
I
IIItll[
I
I LIIII11
I
I
I Illll~
io-" ~o-' Boyord oLpert gouge reoding,
I
,o-5
t li[lil]
I~"
tabor
Figure 2. The calibration of the vacuum gauge unit of the Q60U.
70
I Berecz, S Boh/ttka, J G/tl and A Pa~l, ATOMKI Ki~zleminyek, 19, 123 (1977). 2 1 Berecz, S Boh/ttka and G Langer, Proc 8th Int Vac Conor Cannes, Vol lI, 251 (1980).