US2958775A - Ion sources for mass spectrometers - Google Patents

Ion sources for mass spectrometers Download PDF

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Publication number
US2958775A
US2958775A US766074A US76607458A US2958775A US 2958775 A US2958775 A US 2958775A US 766074 A US766074 A US 766074A US 76607458 A US76607458 A US 76607458A US 2958775 A US2958775 A US 2958775A
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United States
Prior art keywords
ionizing
hole
ion source
electrode
plate
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Expired - Lifetime
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US766074A
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English (en)
Inventor
Robbins Eric John
Mcknight James Alan
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UK Atomic Energy Authority
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UK Atomic Energy Authority
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Publication date
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/10—Ion sources; Ion guns
    • H01J49/14—Ion sources; Ion guns using particle bombardment, e.g. ionisation chambers

Definitions

  • This invention relates to ion sources for mass spectrometers and it provides an ion source suitable for use with gaseous samples such as uranium hexafluoride.
  • an ion source for a mass spectrometer comprises means providing an ionizing beam consisting of a beam of electrons, means providing molecular beam flow of material to be ionized across said ionizing beam, and an electrode of skeletal form providing a small surface area but maintaining a uniform electric field along the path of the ionizing beam where it traverses the molecular flow beam.
  • the skeletal form of the ion source of the invention with its consequent reduction of surface area and increase in the pumping speed of material from the ion source gives reduced corrosion. In this way the memory effect is reduced and the ion source life is increased.
  • the ionizing beam of electrons is increased by a large factor (cg. ten times) over conventional practice and the incoming material to the ion source is beamed into the ionizing beam by passing it through a hole, the diameter of which is less than its length, i.e. a molecular beam is formed.
  • an ion source 1 comprises a cathode 2, an anode 3 and a plate 4 on which is mounted an elec- 2,958,775. Patented Nov. 1, 1960 2 trode 5. A hole 6 is provided through the plate 4 and the electrode 5.
  • the hole 6 has a diameter equal to or less than its length to promote molecular beam flow in gas passing through the hole 6.
  • the hole 6 is fed from a tube (not shown) underneath the plate 4, the tube having the same internal diameter as the hole 6 to assist in promoting molecular beam flow.
  • the cathode 2 has an electron screen 9 having an aperture 10, and the electrode 5 forms a channel 8 and is secured to the plate 4 by bolts 11.
  • the plate 4 and the electrode 5 are mounted on insulators in the normal manner and are maintained at a potential of 2000 volts positive with respect to the ion target of the spectrometer.
  • the cathode 2 and the screen 9 are maintained at a potential of volts with respect to the plate 4 and the anode 3 is maintained at a potential of +25 volts with respect to the plate 4.
  • a heating current is applied to the cathode 2 to provide an ionizing beam of electrons passing from the cathode 2 to the anode 3 along the channel 8 as indicated by arrows 12.
  • the sample being analysed is fed in gaseous form through the tube and the hole 6 to emerge in the channel 8 having molecular beam flow, as indicated by arrows 13.
  • the gas is ionized by the electrons of the ionizing beam, and the ions are collected at the target by known methods.
  • the diameter of the hole 6 is less than the width of the channel 8 and of the same order as the elfective width of the ionizing beam, typical dimensions being:
  • Diameter of hole 6 0.04 inch.
  • Width of channel 8 0.25 inch.
  • the tip of the cathode 2 protrudes through the aperture 10 in the screen 9, so that it is between the screen 9 and the nearer end of the channel 8.
  • the relative distances of these components are adjusted so that the required ionizing electron beam is obtained with an efficiency exceeding by many times that of conventional designs.
  • the focussing of the electron beam is assisted by a magnetic field as in conventional practice.
  • the electrode 5 is designed to provide a uniform potential along the path of the ionizing beam where it traverses the molecular beam flow of gas, this being necessary for good resolution.
  • Ion sources according to the invention have been shown to have a life many times longer than conventional ion sources.
  • a mass spectrometer ion source suitable for use with gaseous samples such as uranium hexafluoride comprising means for providing an ionizing electron beam, means for providing molecular beam flow of the sample to be ionized across said ionizing beam, and an electrode for maintaining a uniform electric field along the path of the ionizing electron beam, said electrode having a base and two similar and parallel upstanding walls which provide a path for said ionizing electron beam, each of said walls having defined therein a series of apertures to substantially reduce the surface area of the wall whereby the electrode has a small surface area while providing for a uniform electric field along the path of the ionizing electric beam Where it traverses the molecular flow beam.
  • a mass spectrometer ion source suitable for use with gaseous samples such as uranium hexafluoride comprising a plate, an electrode mounted on said plate, the
  • 4 electrode having a base secured to the plate and two similar and parallel upstanding walls integral with the base, said base and Walls defining a channel therebetween, said walls each having defined therein a series of apertures to substantially reduce the surface area of the wall, said plate and base having defined therein a hole communicating with said channel, the hole having a diameter equal to or less than its length, a cathode insulatingly mounted on said plate and positioned at one end of said channel and an anode insulatingly mounted on said plate and positioned at the other end of said channel.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Tubes For Measurement (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
US766074A 1957-10-11 1958-10-08 Ion sources for mass spectrometers Expired - Lifetime US2958775A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB31903/57A GB837140A (en) 1957-10-11 1957-10-11 Improvements in or relating to ion sources for mass spectrometers

Publications (1)

Publication Number Publication Date
US2958775A true US2958775A (en) 1960-11-01

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US766074A Expired - Lifetime US2958775A (en) 1957-10-11 1958-10-08 Ion sources for mass spectrometers

Country Status (4)

Country Link
US (1) US2958775A (pl)
BE (1) BE571975A (pl)
FR (1) FR1214231A (pl)
GB (1) GB837140A (pl)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3115591A (en) * 1959-06-22 1963-12-24 Atlas Werke Ag Ion source for mass spectrometer
US3142752A (en) * 1959-08-17 1964-07-28 Atomic Energy Authority Uk Means for reducing the memory effect in a mass spectrometer ion source
US3527937A (en) * 1967-04-11 1970-09-08 Perkin Elmer Corp Electron bombardment type ion source for a mass spectrometer

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1205202B (de) * 1963-04-18 1965-11-18 Hitachi Ltd Elektronenstossionenquelle

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3115591A (en) * 1959-06-22 1963-12-24 Atlas Werke Ag Ion source for mass spectrometer
US3142752A (en) * 1959-08-17 1964-07-28 Atomic Energy Authority Uk Means for reducing the memory effect in a mass spectrometer ion source
US3527937A (en) * 1967-04-11 1970-09-08 Perkin Elmer Corp Electron bombardment type ion source for a mass spectrometer

Also Published As

Publication number Publication date
GB837140A (en) 1960-06-09
BE571975A (pl)
FR1214231A (fr) 1960-04-07

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