US3920988A - Mass spectrometer - Google Patents

Mass spectrometer Download PDF

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Publication number
US3920988A
US3920988A US467788A US46778874A US3920988A US 3920988 A US3920988 A US 3920988A US 467788 A US467788 A US 467788A US 46778874 A US46778874 A US 46778874A US 3920988 A US3920988 A US 3920988A
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Prior art keywords
lens
entrance
electrostatic
ion beam
exit
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US467788A
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English (en)
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Shunroku Taya
Hisashi Matsuda
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Hitachi Ltd
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Hitachi Ltd
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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
    • H01J49/28—Static spectrometers
    • H01J49/32—Static spectrometers using double focusing

Definitions

  • FIG. 1 is a schematic diagram for explaining an example, in which (a) illustrates the focusing action in the radial (x) direction and (b) that in the axial (y) direction.
  • numeral 1 designates an ion source, 8 an ion beam, 3 a cylindrical electrostatic field device, 5' a uniform magnetic field device, and 7 a collector.
  • This lens system effects focusing in the radial (x) direction, but it has no focusing in the axial (y) direction. It is, therefore, inferior in the transmission factor of ions.
  • a toroidal or spherical electrostatic field device In order to apply the focusing action in the axial direction, accordingly, a toroidal or spherical electrostatic field device has been used. Alternatively, a nonuniform magnetic field or a uniform magnetic field device with non-zero entrance and exit angles has been utilized. It has been recognized, however, that where the electromagnetic fields having axial focusing action are utilized, the focusing merely in the first-order approximation is unsatisfactory, which necessitates a system of the smallest possible second-order aberrations.
  • a radial width x of a focused image is expressed in the second-order approximation by the following equation:
  • x A x +A oz -l-A 8 +A x +A x 01 A p X0 8 Aug (1 A a a 8 0 1111 yo ufi ya Bo pp B0
  • x,, a 6 y and 3 denote the states of an ion beam, x and d the expanding width and angle in the radial direction, respectively, 8,, the energy spread, and
  • Aberration coefficients A, App are determined by an ion optical system.
  • A denotes the width of the image in the radial direction, and A and A become zero in case of the double focusing.
  • the coefficients of and after A are generally called the second-order coefficients. How small especially those A A 5 and A55 of these second-order coefficients can be made, has been a problem on the ion optical system in the prior art.
  • H. Hintenberger Z. Naturforsch. 2a 773 (1957) has suggested an ion optical system in which, by suitablyv selecting the parameters of a cylindrical electrostatic lensand a uniform magnetic lens with non-zero entrance and exit angles on the basis of numerical calculations, the second-order coefficients A A s andA55 become very small.
  • the toroidal electrostatic lens when used as the electrostatic lens of the double focusing mass spectrometer, the second-order aberrations can be reduced very sharply.
  • the axial 3 width of a collector slit is expanded in order to increase the quantity of ions, the influences by the bend of the image cannot be removed.
  • An object of the present invention is to provide a double focusing mass spectrometer in which the second-order aberrations are the smallest, and besides, which has axial focusing action.
  • Another object is to provide a double focusing mass spectrometer in which the transmission factors of an ion beam within electrostatic and magnetic fields are large.
  • Still another object is to provide a double focusing mass spectrometer of high resolution and high sensitivity.
  • Yet another object is to provide a double focusing mass spectrometer in which, even when the expanding angle of an ion beam or the energy spread is large, the resolution does not become lower.
  • the present invention for accomplishing these objects is characterized by a toroidal electrostatic lens in which an electrode edge on the entrance side of an ion beam forms a concave surface, and a uniform magnetic lens with non-zero entrance and exit angles.
  • the entrance angle of the ion beam is in the positive direction (a case where the angle defined between the plane normal to the incident beam and the plane of magnetic poles is measured clockwise from the former plane is made the positive direction) while the exit angle is in the negative direction (a case where the angle defined between the plane normal to the emergent beam and the plane of the magnetic poles is measured clockwise from the former plane is made the negative direction).
  • Ratio between the electrostatic lens radius and the magnetic lens radius 1.0 r-,./r,,, 1.1
  • FIG. 1 is a schematic diagram for explaining the radial focusing (a) and the axial focusing (b) of a prior art double focusing mass spectrometer which is based on the combination between a cylindrical electrostatic field and a uniform magnetic field;
  • FIG. 2 is a perspective view ofa toroidal electrostatic field arrangement
  • FIG. 3 is a diagram showing the relations of the second-order aberrations to the constant C of a toroidal electrostatic lens and the width and expanding angle thereof in the axial direction;
  • FIG. 4 is a schematic view for explaining a double focusing mass spectrometer according to the present invention.
  • FIG. 5 is a schematic view showing the axial focusing of the device of the present invention.
  • FIGS. 6 to 11 are diagrams each showing the relations between the parameters and the second-order aberrations of the device of the present invention.
  • FIG. 12 is a schematic view, partly in section, of the essential portions of an embodiment of the mass spectrometer according to the present invention.
  • FIGS. 13 and 14 are spectral diagrams obtained with the mass spectrometer of the present invention, respectively.
  • FIGS 4 and 5 The outline of a device based on the present invention is illustrated in FIGS 4 and 5.
  • FIG. 4 shows the focusing action in the radial (.r) direction
  • FIG. 5 shows the focusing in the axial (y) direction.
  • numeral 1 designates an ion source
  • 2 a slit of the ion source
  • 3 a toroidal electrostatic lens
  • 4 a shield electrode
  • 5 a uniform magnetic lens with non-zero entrance and exit angles
  • 6 a collector slit
  • 7 a detector and 8 an ion beam.
  • the ion beam 8 drawn out from the ion source 1 is subjected to the directional focusing as a part A in the figure by means of the toroidal electrostatic lens 3.
  • the ion beam is subjected to the double focusing (the directional focusing and the velocity focusing) at the collector slit 6 (a part B in the figure).
  • the focusing action in the axial direction is as seen in FIG. 5.
  • the ion beam 8 (the ion beam expanding from one point of the ion source 1) is focused on a part C near the exit of the magnetic lens 5 with nonzero entrance and exit angles, while a beam 8' emerging from the ion source 1 in parallel is focused on a part D near the entrance of the magnetic lens 5.
  • the axial width of the ion beam in the magnetic lens is accordingly reduced considerably.
  • the transmission factor of the ion beam becomes larger in comparison with the prior art device having no axial focusing, such as the double focusing mass spectrometer which comprises the cylindrical electrostatic lens and the uniform magnetic lens in combination.
  • the parameters of the device are determined so that all the second-order aberrations may become the least at the same time.
  • FIG. 12 shows a schematic view, partly in section, of the essential portions of an embodiment in which r,,, 200 mm.
  • numeral 1 indicates an ion source
  • 2 an ion source slit
  • 3 a toroidal electrostatic lens
  • 9 an a-slit
  • 10 a B-slit
  • 11 an ion monitor
  • 5 a mag: netic lens with non zero entrance and exit angles
  • 6 a collector slit
  • 7 a collector composed of a multiplier.
  • r denotes the radius of the electrostatic lens and r,,, the radiusofthe magnetic l'ens l .06
  • the second-order aberrations in the ion optical system thus constructed as calculated in microns are as follows:
  • FIGS. 13 and 14 Measured results obtained with the device of the embodiment are illustrated in FIGS. 13 and 14.
  • the results in FIG. 13 were obtained under the state under which neither the a-slit nor the B-slit was mounted.
  • the mass differences of CO and N were 12 milli mass, and a high resolution above 20,000 was obtained in a 10% valley from this degree of separation.
  • the spectrum in FIG. 14 was obtained when the resolution adjustment was made by mounting the a-slit and the ,B-slit.
  • the resolution in this case was 60,000 in the 10% valley. Since,
  • the resolution is approximately 20,000 at r 200 mm, the performance which is about three times higher is acquired with the mass spectrometer of the present invention.
  • the transmission in the device 80% of the incident ions was measured by the ion monitor ll. Further, where the ion beam passed through the magnetic lens, 50% of the ions incident on the magnetic lens was measured by the collector portion. In contrast, with the prior art device as illustrated in FIG. 1, the former value is 40% and the latter value is 2%. It is, accordingly, understood that the mass spectrometer of the present invention is about times higher in transmission than the prior art device.
  • FIGS. 6 to 11 illustrate to what extent the secondorder aberrations change depending on the values of the parameters of the device.
  • FIG. 6 depicts the relationship between the ratio of the orbital radii of the electrostatic and magnetic lenses (r /r and the second-order aberrations
  • FIG. 7 the relationship between the deflection angle of the electrostatic lens and the second-order aberrations
  • FIG. 8 the relationship between the toroidal electrostatic lens constant (C and the second-order aberrations
  • FIG. 9 the relationship between the concave edge of the electrostatic lens on the entrance side (r,,/d and the second-order aberrations
  • FIG. 10 the relationship between the exit angle from the magnetic lens (6 and the second-order aberrations (e, 30).
  • FIG. 11 the relationship between the distance from the ion source to the entrance of the electrostatic lens (1,) and the second-order aberrations.
  • the mass spectrometer of the present invention reduces the various aberration coefficients, particularly the second-order aberration coefficients, at the same time, and therewith, it enhances the transmission factors of the ion beam within the electrostatic and magnetic lenses.
  • the invention makes a high-resolution and high-sensitivity mass spectrometer possible, and is very greatly effective in industry.
  • a mass spectrometer including means generating an ion beam, a toroidal electrostatic field device and a uniform magnetic field device with end portions disposed with respect to said ion beam to provide nonzero entrance and exit angles
  • the improvement characterized in that an edge of said toroidal electrostatic field device on the entrance side of the ion beam forms a concave surface, and that the entrance angle into said uniform magnetic field device is oriented in the positive direction while the exit angle therefrom is oriented in the negative direction, whereby the elimination of se- 7 cond-order aberrations and focusing in the axial direction are made possible.
  • deflection angle I of the electrostatic lens is 83 deflection angle I', of the magnetic lens is 85 I',
  • entrance and exit angles 6 and 6 of the uniform magnetic lens are 28 e 33 and 8 6 l 2;
  • distance 1 from an ion source to the entrance of the electrostatic lens is 1.2 r, 5 l 5 1.3 r,,,; whereby the elimination of second-order aberrations and the focusing in the axial direction are made possible.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Tubes For Measurement (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
US467788A 1973-05-07 1974-05-07 Mass spectrometer Expired - Lifetime US3920988A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4307295A (en) * 1979-03-15 1981-12-22 University Of Manchester Institute Of Science & Technology Mass spectrometers
US4418280A (en) * 1980-06-13 1983-11-29 Jeol Ltd. Double focusing mass spectrometer
US4634931A (en) * 1983-08-10 1987-01-06 Hitachi, Ltd. Ion implanter
US5317151A (en) * 1992-10-30 1994-05-31 Sinha Mahadeva P Miniaturized lightweight magnetic sector for a field-portable mass spectrometer
US20130126730A1 (en) * 2011-11-17 2013-05-23 National University Of Singapore Sequential radial mirror analyser
CN114709129A (zh) * 2022-03-16 2022-07-05 中国核电工程有限公司 一种质量分析器系统及质谱仪

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5721832B2 (enrdf_load_stackoverflow) * 1975-02-14 1982-05-10

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3061720A (en) * 1960-02-29 1962-10-30 Ewald Heinz Spectrograph
US3194961A (en) * 1962-02-28 1965-07-13 Ewald Heinz Double deflection system for focusing ions of selected mass and charge at a predetermined point
US3671737A (en) * 1969-05-07 1972-06-20 Bell & Howell Co Method for focusing a double focusing mass spectrometer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3061720A (en) * 1960-02-29 1962-10-30 Ewald Heinz Spectrograph
US3194961A (en) * 1962-02-28 1965-07-13 Ewald Heinz Double deflection system for focusing ions of selected mass and charge at a predetermined point
US3671737A (en) * 1969-05-07 1972-06-20 Bell & Howell Co Method for focusing a double focusing mass spectrometer

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4307295A (en) * 1979-03-15 1981-12-22 University Of Manchester Institute Of Science & Technology Mass spectrometers
US4418280A (en) * 1980-06-13 1983-11-29 Jeol Ltd. Double focusing mass spectrometer
US4634931A (en) * 1983-08-10 1987-01-06 Hitachi, Ltd. Ion implanter
US5317151A (en) * 1992-10-30 1994-05-31 Sinha Mahadeva P Miniaturized lightweight magnetic sector for a field-portable mass spectrometer
US20130126730A1 (en) * 2011-11-17 2013-05-23 National University Of Singapore Sequential radial mirror analyser
US8723114B2 (en) * 2011-11-17 2014-05-13 National University Of Singapore Sequential radial mirror analyser
CN114709129A (zh) * 2022-03-16 2022-07-05 中国核电工程有限公司 一种质量分析器系统及质谱仪

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JPS502591A (enrdf_load_stackoverflow) 1975-01-11
JPS5520637B2 (enrdf_load_stackoverflow) 1980-06-04

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