US3441732A - Mass spectrometer comprising means for producing a high-frequency transverse electric field - Google Patents

Mass spectrometer comprising means for producing a high-frequency transverse electric field Download PDF

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Publication number
US3441732A
US3441732A US427340A US3441732DA US3441732A US 3441732 A US3441732 A US 3441732A US 427340 A US427340 A US 427340A US 3441732D A US3441732D A US 3441732DA US 3441732 A US3441732 A US 3441732A
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ions
plates
frequency
axis
mass
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US427340A
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English (en)
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Guy Gautherin
Albert Septier
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/26—Mass spectrometers or separator tubes
    • H01J49/34—Dynamic spectrometers
    • H01J49/42—Stability-of-path spectrometers, e.g. monopole, quadrupole, multipole, farvitrons
    • H01J49/4205—Device types
    • H01J49/421—Mass filters, i.e. deviating unwanted ions without trapping

Definitions

  • the present invention relates to a method and apparatus for isolating ions of a predetermined mass from a beam of ionized particles as in mass spectrometry.
  • the method of the present invention includes selecting those ionized particles of the beam which have a zero transverse velocity, passing those particles into a high frequency electric field oriented perpendicular to the axis of the ionized beam, and selecting from the resulting beam the ionized particles which still have a zero transverse velocity.
  • a mass spectrometer for carrying out the process of the present invention includes a polarizing ring through which the sample beam is admitted to the spectrometer.
  • a pair of parallel diaphragms are located in spaced relationship adjacent to the polarizing ring and each diaphragm includes a slit aligned with the beam axis to pass those particles having zero transverse velocity. Ionized particles emitted from the slits pass between a single pair of electrode plates which are energized by a high frequency alternating voltage to cause an electric field perpendicular to the beam axis.
  • a second pair of spaced parallel diaphragms are located behind the electrode plates, each diaphragm again having a slit oriented parallel to the electrode plates in alignment with the beam axis in order to pass those particles still having a zero transverse velocity.
  • the particles passing through the slits of the second pair of diaphragms define the beam of particles of predetermined mass which may be collected by a suitable electrode.
  • the present invention relates to a novel method of mass spectrometry which takes advantage of the influence of the mass of ions on their time of flight when they are subjected to the action of a high-frequency transverse electric field; the invention is also concerned with a device for the practical application of the above-mentioned method.
  • Mass spectrometers of the magnetic field type are cumbersome as a result of the curvature of the path followed by the ions which form the beam to be analyzed.
  • Said method is characterized in that ions which form a layer containing the axis of the beam and which have a zero transverse velocity are continuously admitted in the high-frequency field, and in that ions which form a noncontinuous layer parallel to the axis of the beam and which also have zero transverse velocity are collected near the exit of the high-frequency field whilst the high frequency of said field varies within a band width which is a iunction of the atomic mass of the ions which form the cam.
  • the device for the practical application of the method outlined above is further characterized in that it comprises an ion source which continuously directs between the parallel plates of a capacitor to which is applied a variable high-frequency voltage, a beam having an axis which is parallel to said plates through the slits of two spaced parallel diaphragms which are perpendicular to said plates thus defining a plane which is also parallel to said plates and which contains said beam axis, as -well as a coaxial collecting electrode which collects the ions derived from the high-frequency field which have passed through a third diaphragm then a fourth diaphragm having slits which are parallel to those of the two first diaphragms and located in a plane parallel to the capacitor plates, said third and fourth diaphragms being so arranged as to contain said beam axis in the case of a high-frequency field which is sinusoidal in time and to be displaced from said axis in the case of excitation by square-wave voltage or saw-tooth voltage
  • one of the capacitor plates is located within very close proximity to the axis of the beam.
  • the device according to the invention makes it possible to analyze beams of ions having an atomic mass which is either lower than or equal to 32.
  • FIG. 1 represents a mass spectrometer for the practi- 3 cal application of the method in accordance with the invention.
  • FIG. 2 is a sectional view along line 2--2 of FIG. 1 and shows a detail of the spectrometer of this figure.
  • FIG. 3 shows a preferred form of embodiment of the invention.
  • FIG. 4 represents a spectrum obtained by means of an apparatus in accordance with the invention.
  • the ion beam is directed continuously into the high-frequency field (er/2w) which is generated between capacitor plates (designated by the reference numerals 2, 4 in FIG. 1) which have a length L and to which is applied a pulsating voltage w.
  • the axis A of the beam is parallel to the plates and consequently perpendicular to the electric field.
  • the paths of the ions which pass into the capacitor all have the same ordinates and a zero transverse velocity.
  • the ions which are collected at the exit of the high-frequency field must have the same ordinate as at the input and a transverse velocity which is also zero.
  • the ions which pass out of the high-frequency field are selected by two diaphragms, the first being located at a distance L from the point of entry into the highfrequency field, and we have:
  • the oscillating circuit which controls the frequency of the high-frequency voltage comprises a variable-capacitance capacitor C
  • the mass of ions which corresponds to the current collected is also a function of the frequency, since we have:
  • the spectrometer 6 of FIG. 1 is contained within a casing 8 in the shape of a cross having four arms or branches 10, 12, 14, 16.
  • the lower branch 10 is connected to a pump 18 which has not been shown in the drawings.
  • the upper branch 12 is closed by a cover 20 fitted with two terminals 22, 24 for the transmission of a high-frequency voltage.
  • the branch 14 is connected to an ion source 26 which is not shown, and finally, a tubular portion 28 forms an extension of the branch 16 of the casing and contains the collecting element 30.
  • the central portion of the casing which has a horizontal axis A and is extended by the branches 14, 16 contains the horizontal plates 2, 4 which are symmetrical with respect to said axis A.
  • the ions could have two types of paths corresponding to the pulses (.0 and w (Equations 3, 4, 5, 6).
  • a simple arrangement makes it possible to eliminate the pulse paths m Accordingly, in accordance with a preferred embodiment of this invention as shown in FIG. 3, it is merely necessary to intercept the ions by placing one of the plates (4') at a very short distance 6 from the axis A.
  • FIG. 2 shows a cross-section along line 22 of FIG. 1 of the arrangement of the plates 2-4, the spacing of which is maintained by means of distance pieces 33, 32, 34 which can be formed of polytetrafiuoroethylene.
  • the plates 24 are respectively connected to the terminals 22-24 by means of braided metal conductors 2628. Said terminals are in turn connected to a high-frequency voltage source 27 which has not been illustrated in the drawings.
  • the entry of ions into the high-frequency field as well as the exit of said ions from said field are respectively defined by two sets of diaphragms 36-38 on the one hand and 40-42 on the other hand which are perpendicular to the axis and provided with slits which are parallel to the plates, said slits being traversed by said axis (since in this case the HF field is sinusoidally variable with respect to time).
  • pairs of diaphragms at the entrance (A) as well as at the exist (B) of the highfrequency field makes it possible to satisfy the conditions previously defined.
  • the widths of the slits of the two diaphragms which are placed at the input of the capacitor 2-4 which serves to impose the conditions of injection hereinabove defined (12) on the mean path determine the maximum angle of inclination of an entry path, this value being given in expression (11) of the resolving power.
  • the beam 41 which issues from the source 26 is directed towards the first diaphragm 36 which is cooled together with its support by a flow of water (circulated through the pipe 44).
  • the polarizing ring 46 which is coaxial with A and magnets 4850' prevent any errors resulting from secondary electrons produced by the impact of incident ions.
  • the collector 30 is surrounded by an electrode 52 which forms a screen.
  • the current which is collected by the electrode 30 is transmitted by a coaxial cable 54 which is connected to a display device.
  • a suitable electric polarization of the collector 30 which receives the analyzed ions prevents any disturbances arising from secondary electrons.
  • a spectrometer of the type which has just been described has been constructed by the present applicants.
  • the capacitor plates have an adjustable length of 0.25 mm.
  • a simple device permits the possibility of making the plates parallel to the axis of the beam.
  • the high frequency of the voltage applied between the plates 2-4 varies over two ranges between 0.6 and 2.7 mc./s. and between 2.7 and 6 mc./s. These ranges which are determined with a view to analyzing a beam of hydrogen of 30 kv. permit the possibility of studying ions having a mass which is lower than or equal to 32.
  • the amplitude of the high frequency field is 500 v./cm., so that the maximum amplitude of ionic oscillations is slightly smaller than the spacing of the plates.
  • the maximum peak intensity is of the order of 50x10 amps in respect of a current intensity of injected beam of 10- amps; the signal/noise ratio is of the order of 50 (the noise is due to stray ions having a high mass (a high value of K)
  • the current intensity of the diiferent peaks can be increased to a substantial extent if a low resolving power is considered sufficient (which in certain experiments is not a disadvantage). It is merely necessary for this purpose to enlarge the entry diaphragms.
  • FIG. 4 A spectrum supplied by the apparatus is represented in FIG. 4, wherein the frequencies (in megacycles) are plotted as abscissae and the current intensities (10* A.) are plotted as ordinates.
  • the mass resolving power is 60 under given operating conditions. It is possible to increase the resolving power by reducing the width of the selecting slits.
  • the resolving power of the apparatus can also be increased by applying a high-frequency square-Wave voltage or saw-tooth voltage to the capacitor plates instead of a sinusoidal voltage.
  • a mass spectrometer for separating ions of a predetermined mass from a beam of ionized particles including:
  • each of said diaphragms including a slit aligned with said axis to define a path for particles having zero transverse velocity
  • each said diaphragms including a slit parallel to said electrode plates in alignment with said axis to define a further path for particles having zero transverse velocity
  • a mass spectrometer as described in claim 1 further including a source of high frequency sinusoidal voltage connected to said electrode plates.
  • a mass spectrometer for separating ions of a predetermined mass from a beam of ionized particles includmg:
  • each of said diaphragms including a slit aligned with said axis to define a path for particles having zero transverse velocity
  • each said diaphragm including a slit parallel to said electrode plates and transversely displaced from said axis to define a further path for particles having zero transverse velocity

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Electron Tubes For Measurement (AREA)
US427340A 1964-01-31 1965-01-22 Mass spectrometer comprising means for producing a high-frequency transverse electric field Expired - Lifetime US3441732A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR962324A FR1393400A (fr) 1964-01-31 1964-01-31 Procédé de spectrométrie de masse utilisant un champ électrique transversal de haute fréquence

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US3441732A true US3441732A (en) 1969-04-29

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US (1) US3441732A (ja)
BE (1) BE658708A (ja)
CH (1) CH429234A (ja)
DE (1) DE1598195A1 (ja)
ES (1) ES308740A1 (ja)
FR (1) FR1393400A (ja)
GB (1) GB1100481A (ja)
LU (1) LU47882A1 (ja)
NL (1) NL6501028A (ja)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3532880A (en) * 1968-01-30 1970-10-06 Nasa Electrostatic charged particle analyzer having deflection members shaped according to the periodic voltage applied thereto

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1115501A (fr) * 1953-12-12 1956-04-25 Tno Spectrographe de masse
US2818507A (en) * 1946-03-22 1957-12-31 Roy J Britten Velocity selector method for the separation of isotopes

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2818507A (en) * 1946-03-22 1957-12-31 Roy J Britten Velocity selector method for the separation of isotopes
FR1115501A (fr) * 1953-12-12 1956-04-25 Tno Spectrographe de masse

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3532880A (en) * 1968-01-30 1970-10-06 Nasa Electrostatic charged particle analyzer having deflection members shaped according to the periodic voltage applied thereto

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Publication number Publication date
BE658708A (ja) 1965-05-17
NL6501028A (ja) 1965-08-02
LU47882A1 (ja) 1965-03-29
FR1393400A (fr) 1965-03-26
CH429234A (fr) 1967-01-31
ES308740A1 (es) 1967-06-16
DE1598195A1 (de) 1971-05-27
GB1100481A (en) 1968-01-24

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