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Патент USA US3086120

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April 16, 1963
2 sheets-säen 1
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FIG. 3
April 16, 1963
Filed March 2. 1959
2 Shee‘tSLShee'l'. 2
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United States Patent O ” ICC
3,0-86,l l0
Patented Apr. 16, 1963
Anton Martin Klopt‘er, Aachen, Germany, assigner t
North American Philips Company, Inc., New York,
N.Y., a corporation of Delaware
Fitted Mar. 2, 1959, Ser. No. 796,626
Claims priority, application Germany Mar. 15, 1958
1 Claim. (Cl. Z50-41.9)
quency plates, according to the invention two relatively
parallel plates are arranged parallel -to the direction of
the magnetic field and at right angles to the field-distri
bution rings adjacent the ends of these rings, said plates
having applied to them a negative voltage of several
-tens of volts with respect to the high-frequency plates
so that the tiow of ions towards the collector isa maxi
mum for both light and heavy ions.
The present invention builds further upon the recog
This invention relates to mass spectrometers for gases 10 nition that a positive electrostatic field between the
high-frequency plates and the field-distribution rings, pos
at low pressures in which a beam of electrons is shot in
sibly the plates through which the beam of electrons
the direction of a static homogeneous magnetic field be
tween two relatively parallel and electrically connected
plates, an electric high-frequency iield being produced in
enters and emerges, facilitates a movement of ions towards
the collector in planes parallel to the direction of the
the space between said plates, at right angles to the mag 15 magnetic field, whereas this field causes ions to move
towards the other electrodes in planes at right angles to
the magnetic field. The last-mentioned unfavorable iield
is not only lavoided due to the two side-plates being at
negative potential, but also the ions are assisted in their
electrode a collector being arranged for such ions as
movement towards the collector, so that interfering ef
describe paths of increasing radius by the action of the
fects, such as gas layers and electric charges of the elec
various fields.
trodes, cannot substantially influence the paths of the
In one of the oldest embodiments of the above-men
tioned mass spectrometer, which is also known under the
In order that the invention may be readily carried
name omegatron, the high-frequency plates are collec
tors. Between these plates there `also exists a weak 25 into effect, it will now be described in detail, by way
of example, with reference to the accompanying draw
static field which serves to deflect non-resonant ions at
netic field, between two likewise parallel plates, annular
intermediate electrodes being provided for homogenising
the high-frequency field and adjacent one high-frequency
ings, in which:
right angles to the direction of the magnetic field and
FIGS. l 4to 3 show three mutually perpendicular cross
of the electric high-frequency field. If desired the two
high-frequency plates may be connected separately to 30 sections of a mass spectrometer according to the inven
negative voltages with respect «to the field-distribution
FIGS. 4 and 5 show its circuit diagrams and
FIG. i6 shows the relative liow of ions towards the
collector` as a function of a negative voltage on the side
A construction is also known which has no -tield dis 35 plates, that is to say -for ions of two different masses.
In F-IGS. 1 to 3, the bulb of‘ the -mass spectrometer
tribution rings, but in which >the two plates between
In another embodiment, one of the field distribution `
electrodes serves also as a collector for the resonant ions.
which the beam of electrons is accelerated, together with
is indicated by 1. A plurality of current-supply wires
«two plates at right angles thereto, embrace the high-fre
are `arranged in the base of bulb «1. The electrode sys
tem is built up on these lead-through wires with the aid
quency space. In certain cases, these four plates have
applied to them a common negative voltage less than 1 40 of wire supports. The base has a tubular extension 2
in which the current-supply wire for the collector ex
volt with respect to the high-frequency plates (on account
of sensitivity variations of the omegatron).
Furthermore, a construction is known which has either
tends.- The cathode filament, indicated by 3, is arranged
inside a screen electrode 4 having an aperture for the
beam of electrons. An accelerating and focusing elec
field distribution rings or side plates embracing the high
frequency field. The collector is constituted by a strip 45 trode 5 is arranged in front of the aperture in screen
parallel to the high-frequency plates, the strip being
4. The two plates 6` provided with apertures for passage
either situated between the field distribution rings, or in
of the electron beam are connected to one high-frequency
troduced into a slot- in a side plate.
plate 7, the other high-frequency plate bearing the num
rIïhe electrodes ern
bracing the high-frequency space are at a weakly positive
ber 8i.
The plate 7 has a narrow aperture 9 through
potential with respect to the high-frequency plates.
50 which a collector 10> is passed. The current-supply wire
It has also been described to provide the high-fre
11 for collector 10 is surrounded by a screen structure
quency plates with a U shape.
It has been found that various types of omegatrons
The field-distribution rings, which are in total four
in the figure, but may alternatively be six or eight in
pressures of the components of a mixture of gases are to 55 number, are indicated by 12. A collector 14 for the
electrons is .arranged behind one of the plates 6. The
be determined.
An object of the invention is to provide an improve
side plates according to the invention bear the number
ment which allows of reproducible measurements.
ln a mass spectrometer for gases of low pressure, in
A tube leads from» the bulb to the apparatus from
which a beam of electrons is shot in the direction of a 60 the contents of which the composition of the gas is to
statical homogeneous magnetic ñeld between two rela
be determined.
do not yield reproducible results especially if the partial
tively parallel and electrically connected plates, in which
an electric high-frequency field is produced in the space
The direction of the magnetic field produced by pole
pieces 33, 34 is indicated by arrow H in FIG. l. The
between these plates, at right angles to the magnetic
figures show the correct relative proportions. Plate S
field, between two likewise parallel plates, in which an 65 has dimensions of 25 by l5 mms.
nular intermediate electrodes are provided for homoge
The electrodes consist of gold sheet of 0.3 mm. thick.
nising the high-frequency field and in which adjacent one
lf desired, it is possible to use gold-plated constantan
high-frequency electrode a collector is arranged for such
or platinum or a platinum alloy. If the mass spectrom
ions as describe paths of increasing radius by the action
eter can be sufficiently protected against oxidation, con
of the various fields, and in which the electrodes embrac 70 stantan is also permissible as the electrode material.
ing the high-frequency space have applied -to them a
In FlG. 4, reference numeral 21 indicates the heating
weakly positive potential wtih respect to the 4high-fre
current battery for -the cathode and 21 indicates the bat
tery for the accelerating voltage. The battery 23 applies
to the electrode 5 a positive voltage of about 10 volts
with respect to the electrode 6.
The electrodes 4 and
5, when suitably connected, may be used for stabilising
the flow of electrons. The battery 22 has a voltage
of about )0y volts. The collector-electrode 14 receives,
with the aid of `a battery 24 and a potentiometer 25, a
positive voltage of at most about 40» volts with respect
to the electrode 6.
obtain movements perpendicular to the magnetic ñeld H.
For certain ions for which the motion in the field corre
sponds to the frequency of the high-frequency field the
movement is in spirals of increasing radius such as is
known in the arrangements of the known art. Ulti
mately these ions are collected on collector electrode v110.
By varying the `frequency of the high-frequency ñeld,
ions of different mass can be collected.
From FIG. 6 it can be seen that a rather high nega
In FIG. 5, the high-frequency voltage is applied to a 10 tive Voltage on electrodes 15 is necessary to collect both
terminal 26. The maximum effective high-frequency
light and heavy ions which could not be the case in
voltage is 1 volt and the frequency lies between 8
the known arrangements.
mc./Sec. and 30‘ kc./sec. for the masses of from 1 to
What is claimed is:
260. The magnetic ñeld has a strength of 5,000 gauss.
A mass spectrometer for a gas at low pressures com
The tield~distribution rings 12 are coupled by means 15 prising means including a source of electrons and an
of resistors 27 each of 200` ohms and capacitors 23 each
accelerating electrode to project a beam of electrons into
of 1 nf. in a high-frequency manner to the plates ’i and
a gas in a given direction between a pair of spaced, rcla8. By means of a battery 29 and a voltage divider 30,
tively parallel, electrically connected plates; means to
the rings 12 receive a positive voltage of at most 1 volt
produce a static, homogeneous magnetic `lield between
with respect to the plates 7 and 8.
the plates in the same direction as said given direction;
A battery 31 and a potentiometer 32 impose on the
means to produce a high-frequency electric field between
plates 1S a negative voltage of at most 200 volts with
a second pair of plates in a direction perpendicular to
respect to the electrodes 7 and 8.
the direction of the magnetic iicld; a plurality of annu
FIG. 6 shows the relative flow of ions z'+/i+max towards
lar electrodes disposed between the latter plates for
the collector for the gases nitrogen and hydrogen as a 25 homogenizing the high-frequency electric field; a co1
function of the negative voltage V15 on the electrode
lector electrode disposed adjacent to one of said plates
15 at a pressure of 4.1041 mm. of Hg with otherwise
for the high-frequency electric ñeld to collect ions whose
optimum conditions for a mass spectrometer having 6
.paths have an increasing radius when subject to said
field-distribution rings. It will readily be evident that a
field; means to apply a positive potential to the accelerat
rather high negative voltage on the electrodes 15 is 30 ing electrode relative to the electrodes enclosing the
required for both the light and the heavy ions. The
space; a pair of relatively parallel plates disposed paral
lel to the direction of the magnetic field adjacent to the
value of the voltage is, of course, dependent upon the
distance between these electrodes and the field-distribu
ends of and at right `angles to the annular electrodes; and
tion rings, upon the dimensions and the number of these
means .to apply a relatively large negative potential to
rings. A beam of electrons is drawn from cathode 3
said latter plates to maximize the flow of light and heavy
through holes in shield 4, electrode 5 and ñrst electrode
ions to the collector.
6 in the space between high-frequency electrodes 8, 9
References Cited in the tile of this patent
and ñeld rings 12. The electron beam ionizes the gas
present in enclosure 1. The beam of electrons is col 40
lected through a hole in second electrode 6 on a col
lector electrode 14.
The ions formed come under the influence of the high
frequency ñeld between electrodes 8 and 9.
Due to the presence of the magnetic field H, the ions 45
Robinson ____________ __ Feb. 17, 1953
Jernakoff ____________ „„ Dec. 28, 1954
Lanneau et al ___________ -_ July 9, 1957
Langmuir ____________ __ Sept. 17, 1957
Lanneau et al. ________ __ Jan. 13, 1959
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