EP1611593B1 - Jauge à ionisation et méthode pour déterminer une pression d'ions totale - Google Patents

Jauge à ionisation et méthode pour déterminer une pression d'ions totale Download PDF

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Publication number
EP1611593B1
EP1611593B1 EP02808369A EP02808369A EP1611593B1 EP 1611593 B1 EP1611593 B1 EP 1611593B1 EP 02808369 A EP02808369 A EP 02808369A EP 02808369 A EP02808369 A EP 02808369A EP 1611593 B1 EP1611593 B1 EP 1611593B1
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EP
European Patent Office
Prior art keywords
electron beam
ion
ionization
beam stop
louvers
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Expired - Lifetime
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EP02808369A
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German (de)
English (en)
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EP1611593A2 (fr
Inventor
Robert E. Ellefson
Louis C. Frees
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Inficon Inc
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Inficon Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J41/00—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas; Discharge tubes for evacuation by diffusion of ions
    • H01J41/02—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas
    • H01J41/04—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas with ionisation by means of thermionic cathodes

Definitions

  • This invention pertains to the field of ionizing gas samples for analysis, and in particular to reducing the residual current in an ionization gauge due to the X-ray effect by using a louvered beam stop.
  • the low pressure measurement limit of total pressure gauges is largely limited by the generation of x-rays when electrons strike grid surfaces in the gauge structure.
  • the x-rays generated have a cosine squared distribution of intensities leaving the surface. Some of these energetic photons can strike the total pressure collector and eject an electron from the ion collector. This loss of an electron is indistinguishable from the arrival of an ion at the collector.
  • the photoelectron ejection is recorded as an ion current which at very low pressures produces an "X-ray limit" for low pressure for any gauge.
  • This X-ray limit is particularly high for the triode type of ion gauge where the collector surface is a cylinder around the central filament and grid.
  • Prior art in minimizing this problem includes:
  • GB-A-1 194 943 provides a gauge for measuring, by means of electron beam, the rate of evaporation of substances in an evacuated enclosure.
  • Said gauge comprises an electron source, an electron collector located in relation to the vapour jet on the side opposite the electron source, a collision collector and at least one measuring instrument located outside the enclosure. Based on the construction of said gauge, the executed measurements show inaccuracies resulting from simultaneously collecting electrons and ions in said gauge.
  • louvered beam stop creates shadow regions having no X-rays, thus minimizing the amount of X-rays striking the collector plate and reducing the X-ray effect portion of the residual current.
  • the beam stop in an ionization gauge having an electron beam shaped by an anode, in which gas molecules are ionized by the electron beam for analysis, and a beam stop which collects substantially all electrons in the electron beam not interacting with the gas molecules, the beam stop includes a plurality of louvers on the beam stop.
  • an apparatus for determining a total ion pressure of a gas includes an ionization chamber; the ionization chamber having first and second ionization regions, wherein a boundary between the regions is defined by an anode grid; means for producing an electron beam passing through the first and second ionization regions, whereby an interaction between the electron beam and molecules of the gas within the ionization chamber produce first and second ion streams from a same gas density; an electron beam stop which collects substantially all electrons not interacting with the gas molecules, the electron beam stop including a plurality of louvers; means for directing the first ion stream to an analyzer; and means for directing the second ion stream to an ion collector.
  • a method for determining a total ion pressure of a gas includes (a) providing an ionization chamber, the ionization chamber having first and second ionization regions, wherein a boundary between the regions is defined by an anode grid; (b) producing an electron beam passing through the first and second ionization regions, whereby an interaction between the electron beam and molecules of the gas within the ionization chamber produce first and second ion streams from a same gas density; (c) using an electron beam stop which collects substantially all electrons not interacting with the gas molecules, the electron beam stop including a plurality of louvers; (d) directing the first ion stream to an analyzer; and (e) directing the second ion stream to an ion collector.
  • a method for reducing a residual current in an ionization gauge includes (a) providing an ionization chamber containing gas molecules of a gas to be analyzed; (b) producing an electron beam passing through the ionization chamber, whereby an interaction between the electron beam and the gas molecules within the ionization chamber produce at least one ion stream; (c) directing at least a portion of the ion stream to an ion collector; and (d) using an electron beam stop which collects substantially all electrons not interacting with the gas molecules, the electron beam stop including a plurality of louvers, wherein the louvers direct a plurality of X-rays formed by the electrons interacting with the electron beam stop away from the ion collector.
  • an ionization gauge 8 is shown in which an electron beam 10 is emitted from a filament 12.
  • the electrons in electron beam 10 are focused by a three-sided repeller 14 which is mounted such that a center of filament 12 is preferably at the center of diagonals drawn from the corners of repeller 14.
  • Repeller 14 is connected to the negative side of filament 12, thus making repeller 14 more negative than the potential of emitted electrons by an amount equal to the filament voltage with respect to the negative lead at the point the electron is emitted. This is approximately one-half the voltage across the filament ( ⁇ 1.5 V).
  • the electrons in electron beam 10 are drawn to an anode 16, preferably a square anode, by a voltage that is positive with respect to filament 12.
  • Anode 16 is preferably biased at 70 V.
  • Anode 16 separates a first region (partial pressure) 20 from a second region (total pressure) 22.
  • Electron beam 10 forms ions in both the first and second regions 20, 22.
  • a plurality of ions 30 from first region 20 are extracted by a focus lens 24 and directed to a mass analysis device (not shown), where they form ion currents proportional to pressures of gas components in region 20.
  • a plurality of ions 32 from second region 22 are collected by an ion collection device, such as a collector plate 26, to produce a current proportional to the total pressure of gas components in second region 22.
  • the electrons in electron beam 10 continue through first and second regions 20, 22 and impact on a beam stop 28.
  • Anode 16 and beam stop 28 together function as an anode for electron beam 10, resulting in the path of electrons in electron beam 10 being perpendicular to the equipotential lines established by the structure, thus resulting in a focused beam.
  • louvers 36 in beam stop 28 controls the direction of the emitted X-rays 34. Louvers 36 are in the portion of beam stop 28 that is approximately +/- 20 degrees from the central axis of electron beam 10. The angle of louvers 36 is preferably 30-45 degrees from the vertical plane of beam stop 28 as shown in Fig. 2 .
  • X-rays 34 are produced whose energy is less than the electron energy and whose angle of emission from the surface of louvers 36 of beam stop 28 is a cosine-squared distribution about an axis normal to each louver 36.
  • This design minimizes the number of X-rays emitted parallel to louvers 36, thus creating a shadowed region with no x-rays behind each plate and behind a line extending parallel to each angled plate.
  • Collectively the effect is to minimize x-rays striking the collector plate 26.
  • the dimensions of collector plate 26 are designed to be in the shadowed region and yet create the necessary field to efficiently attract and collect ions.
  • Fig. 3 the ion current measured vs pressure for the total pressure collector with a flat beam stop is shown. Note that below 2E-8 Torr the output ion current is constant at 1E-10 A. Also shown in Fig. 3 is the ion current vs pressure for the louvered beam stop of the present invention. The extension of a linear response to the ion current is clearly shown.

Landscapes

  • Measuring Fluid Pressure (AREA)
  • X-Ray Techniques (AREA)

Claims (7)

  1. Jauge à ionisation (8) présentant un arrêt de faisceau (28), ladite jauge à ionisation (8) présentant un faisceau d'électrons (10) mis en forme par une anode (16) et dans laquelle des molécules de gaz sont ionisées par ledit faisceau d'électrons (10) pour une analyse, ledit arrêt de faisceau (28) étant agencé pour recueillir essentiellement tous les électrons dans ledit faisceau d'électrons (10) n'interagissant pas avec lesdites molécules de gaz, caractérisée en ce que ledit arrêt de faisceau (28) comprend en outre une pluralité d'ailettes (36) agencées de manière angulaire entre environ 30 et 45 degrés depuis un plan vertical dudit arrêt de faisceau (28), ledit plan vertical étant essentiellement perpendiculaire à un axe longitudinal du faisceau d'électrons (10) et
    dans laquelle ladite pluralité d'ailettes (36) est disposée essentiellement sur une portion centrale dudit arrêt de faisceau (28) approximativement à +/- 20 degrés de l'axe central dudit faisceau d'électron (10).
  2. Appareil (8) selon la revendication 1, comprenant :
    une chambre d'ionisation ;
    ladite chambre d'ionisation présentant des première (20) et seconde zones d'ionisation (22), une limite entre lesdites zones étant définie par une grille-anode (16) ;
    des moyens (12) pour produire un faisceau d'électrons (10) passant à travers lesdites première (20) et seconde zones d'ionisation (22), ce par quoi une interaction entre ledit faisceau d'électrons (10) et des molécules dudit gaz à l'intérieur de ladite chambre d'ionisation produit des premier et second flux d'ions d'une même densité de gaz ;
    des moyens (24) pour diriger ledit premier flux d'ions vers un analyseur ;
    des moyens pour diriger ledit second flux d'ions vers un collecteur d'ions (26).
  3. Appareil (8) selon la revendication 2, caractérisé en ce qu'il comprend en outre :
    des moyens pour recueillir ledit premier flux d'ions audit collecteur d'ions (26) ;
    des moyens pour mesurer un courant de référence produit par ledit second flux d'ions audit collecteur d'ions (26) et
    des moyens pour, en utilisant ledit courant de référence, calculer ladite pression d'ions totale dudit gaz à l'intérieur de ladite chambre d'ionisation.
  4. Appareil (8) selon la revendication 2, caractérisé en ce que ladite pluralité d'ailettes (36) est seulement sur une portion centrale dudit arrêt de faisceau (28).
  5. Appareil (8) selon la revendication 4, caractérisé en ce que ladite pluralité d'ailettes (36) est à un angle entre 30 et 45 degrés depuis un plan vertical dudit arrêt de faisceau (28).
  6. Appareil (8) selon la revendication 2, caractérisé en ce que ladite pluralité d'ailettes (36) est à un angle entre 30 et 45 degrés depuis un plan vertical dudit arrêt de faisceau (28).
  7. Méthode pour déterminer une pression d'ions totale d'un gaz, comprenant les étapes consistant à :
    fournir une chambre d'ionisation, ladite chambre d'ionisation présentant des première (20) et seconde zones d'ionisation (22), dans laquelle une limite entre lesdites zones est définie par une grille-anode (16) ;
    produire un faisceau d'électrons (10) passant à travers lesdites première (20) et seconde zones d'ionisation (22), ce par quoi une interaction entre ledit faisceau d'électrons (10) et des molécules dudit gaz à l'intérieur de ladite chambre d'ionisation produit des premier et second flux d'ions d'une même densité de gaz ;
    diriger ledit premier flux d'ions vers un analyseur ;
    diriger ledit second flux d'ions vers un collecteur d'ions (26) ; et
    utiliser un arrêt de faisceau d'électrons (28) qui recueille essentiellement tous les électrons n'interagissant pas avec lesdites molécules de gaz, caractérisé en ce que
    ledit arrêt de faisceau d'électrons (28) comprend une pluralité d'ailettes (36), ladite pluralité d'ailettes (36) étant agencée de manière angulaire entre environ 30 et environ 45 degrés depuis un plan vertical dudit arrêt de faisceau (28), ledit plan vertical étant essentiellement perpendiculaire à un axe longitudinal dudit faisceau d'électrons (10), et dans lequel ladite pluralité d'ailettes (36) est disposée essentiellement sur une portion centrale dudit arrêt de faisceau (28) approximativement à +/- 20 degrés de l'axe central dudit faisceau d'électrons (10).
EP02808369A 2002-05-28 2002-05-28 Jauge à ionisation et méthode pour déterminer une pression d'ions totale Expired - Lifetime EP1611593B1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2002/011321 WO2005091330A2 (fr) 2002-05-28 2002-05-28 Arret de faisceau a volets permettant de reduire la limite des rayons x d'une jauge de pression totale

Publications (2)

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EP1611593A2 EP1611593A2 (fr) 2006-01-04
EP1611593B1 true EP1611593B1 (fr) 2009-09-02

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EP (1) EP1611593B1 (fr)
JP (1) JP4252064B2 (fr)
DE (1) DE60233607D1 (fr)
WO (1) WO2005091330A2 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPWO2011040625A1 (ja) * 2009-09-29 2013-02-28 有限会社真空実験室 イオン源を有する真空計測装置

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2834280A (en) * 1954-02-10 1958-05-13 Robertson Co H H Louver

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB185834A (en) * 1921-06-10 1922-09-11 George Chappell Minnitt Improvements in or relating to louvre window or like shutters
US2820946A (en) * 1954-02-01 1958-01-21 Cons Electrodynamics Corp Apparatus for leak detection and pressure measurement
CH490678A (fr) * 1967-04-21 1970-05-15 Battelle Development Corp Jauge de mesure de la vitesse d'évaporation sous vide
US3971359A (en) * 1975-04-14 1976-07-27 Richard Curtis Bourne Louvered selective solar energy collector
US5889281A (en) * 1997-03-21 1999-03-30 Leybold Inficon, Inc. Method for linearization of ion currents in a quadrupole mass analyzer
US6187359B1 (en) * 1999-05-12 2001-02-13 Anthony Mark Zuccarini Method and apparatus for baking foods in a barbeque grill

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2834280A (en) * 1954-02-10 1958-05-13 Robertson Co H H Louver

Also Published As

Publication number Publication date
EP1611593A2 (fr) 2006-01-04
DE60233607D1 (de) 2009-10-15
JP4252064B2 (ja) 2009-04-08
WO2005091330A2 (fr) 2005-09-29
WO2005091330A3 (fr) 2005-11-10
JP2006510036A (ja) 2006-03-23

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