US3307774A - Vacuum ion pump - Google Patents

Vacuum ion pump Download PDF

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Publication number
US3307774A
US3307774A US409653A US40965364A US3307774A US 3307774 A US3307774 A US 3307774A US 409653 A US409653 A US 409653A US 40965364 A US40965364 A US 40965364A US 3307774 A US3307774 A US 3307774A
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US
United States
Prior art keywords
anode
cathode
ion pump
spacing
exhaust port
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US409653A
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English (en)
Inventor
Bannock Roy Robert
Pressel Otto
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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Filing date
Publication date
Application filed by US Philips Corp filed Critical US Philips Corp
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Publication of US3307774A publication Critical patent/US3307774A/en
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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
    • H01J41/12—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps
    • H01J41/18—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps with ionisation by means of cold cathodes
    • H01J41/20—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps with ionisation by means of cold cathodes using gettering substances

Definitions

  • the present invention is directed to an improved construction' of vacuum pump of the type operating on the well known Penning principle.
  • Such pumps are now commonly known as vacuum ion or electrical pumps and depend for their operation on the ionization of residual gas molecules by the establishment of an electrical discharge between an anode surface and a cathode surface.
  • a magnetic field is provided to impart an oscillatory motion to the electrons thereby increasing the probability of collision with gas particles and consequential ionization.
  • Ionized gas particles are accelerated by the applied electrostatic field towards the cathode surface, which is usually made of a reactive metal such as titanium.
  • Suchknown arrangements provide a plurality of discharge paths each of which contributes to the ionization and the consequential increase in pumping action.
  • optimum pumping conditions can be related to cell dimensions and the relative spacing between anode and cathode. Furthermore, under operating conditions the applied electrostatic and magnetic field strengths have a significant influence on the pumping action. All these parameters are more or less interdependent and alter with pressure. Physical dimensions are generally chosen as a compromise between economic"considerations and the desired range of pumping pressures.
  • an ion pump of the known type comprising a plurality of cells each having a cross-sectional area of 12 12 mm. in which the anode depth facing the exhaust port was 6 cells deep and having a constant anode to cathode spacing of 2.5 mm., was shown to have a calculated unit cell pumping speed of approximately 0.5 litre/sec.
  • the cells farthest from the exhaust port "ice contributed only 0.3 litre/sec. due to the impedance be tween the port and the remote cell discharge area. This means that the cells farthest away operated at only of their optimum pumping speed.
  • a further disadvantage noted in known vacuum io pump constructions is the difiiculty in re-establishing a discharge at low pressures. For example, if an initial pumping operation is taken down to 1()' torr. and then temporarily switched off, difficulty will be experienced in re-establishing the discharge for continuing the-pumping operation because pressure X discharge distance is a constant (Paschens Law).
  • -It is an object of the present invention to provide an improved ion pump structure which mitigates the above disadvantages and at the same time provides an enhanced pumping speed over a greater range of pressures when compared to known structures.
  • spacing between at least one anode and an associated cathode is tapered in a direction which provides spacing which increases towards an exhaust port.
  • a vacuum ion pump of the type described wherein a wedgeshaped anode section is secured between parallel cathode surfaces and the thin edge of the said wedge-shaped anode is positioned towards an exhaust port.
  • an ion pump of the type described is provided with a substantially parallel anode structure arranged in spaced relationship between two cathode surfaces which converge but do not contact the anode part remote from an exhaust port.
  • Yet a further modification of the present invention resides in a construction in which the anode structure is stepped to provide an increased anode to cathode spacing in a direction towards an exhaust port.
  • Ion pumps constructed in the manner described according to the present invention have advantages in that arcing between electrodes is substantially restricted to that part where the electrode spacing is closest and the increased spacing towards the incoming gas particles allows such particles a freer access to the discharge areas. Furthermore, the increased electrode spacing allows an easier re-establishment of a discharge at low pressures.
  • FIGURE 1 illustrates an ion pump comprising a box like housing 3 which is constructed of stainless steel and in which is supported a wedge-shaped cellular anode structure 5 of titanium.
  • the anode structure 5 comprises three columns of cells each column 8 cells deep.
  • the anode structure 5 is held by rods 6 which also serve as terminals for the application of an electro-static potential.
  • the rods 6 are insulated from the housing 3 in a gas tight manner by feed-through insulators 8.
  • Sputter guards 17 surround the internal rod parts to prevent the deposition of sputtered material around the insulators 8.
  • the housing 3 is provided with cathode surfaces 4 which may be of titanium or other reactive metal and are positioned adjacent the open ends of the wedge-shaped cellular anode structure 5.
  • An exhaust port 7 is provided in the housing 3 in a position adjacent the thin end of the wedge-shaped anode 5 and magnetic pole pieces 1 and 2 are shown as part of a permanent magnet system which provides a magnetic field substantially parallel with the walls of the cells'of the anode 5.
  • FIGURE 2 shows a modified anode structure comprising a number of cells 10, the lengths of the walls of which are reduced by steps '9.
  • this anode structure is intended to be mounted in a pump housing (not shown) in which the cathode surfaces are parallel and in which an exhaust port is positioned in the vicinity of the shortest cell length and the longest discharge path.
  • FIGURES 1 and 2 afford a further advantage in that the anode structure is secured to the pump housing at a point where the anode weight is greatest and this gives for better rigidity and ruggedness and allows such pump structures to be incorporated in equipment which may be in motion or vibrated.
  • FIGURE 3 illustrates a modified ion pump structure according to the present invention in which a multi-cellular anode 11 is provided with substantially constant cell lengths and the varying electrode spacing is effected by converging cathode surfaces 12 contained within a pump housing 13. Permanent magnet pole pieces 16 are included for providing the magnetic field substantially parallel with walls of the anode cells.
  • the anode structure 11 is held in position by rods 18 which together with feed-through insulators 14 serve as terminals for the application of an electro-static potential.
  • An exhaust port 15 is provided opposite the anode 11 where the anode to cathode spacing is greatest.
  • the loss due to the increased electrode spacing in the vicinity of the port was shown to have dropped from the previous 0.5 litre/sec. to only 0.41 litre/ sec.
  • the total pumping speed for the pumping structure in accordance with the present invention results in an increase from the previous 0.08 litre/sec. to 0.89 litre/see, i.e. an increase of 12% in the overall pumping speed.
  • a vacuum ion pump as claimed in claim 1 in which the anode has a wedge-shaped section and is secured between parallel cathode surfaces, the thin edge of said' wedge-shaped anode being positioned towards an exhaust port.
  • a vacuum ion pump as claimed in claim 1 in which the anode comprises a substantially parallel structure arranged in spaced relationship between two cathode surfaces which converge but do not contact the anode part remote from an exhaust port.
  • a vacuum ion pump as claimed in claim 1 in which the anode is provided with stepped section which increases the anode to cathode spacing in a direction towards an exhaust port.

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  • Electron Tubes For Measurement (AREA)
  • Particle Accelerators (AREA)
US409653A 1963-11-08 1964-11-09 Vacuum ion pump Expired - Lifetime US3307774A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB44173/63A GB1021064A (en) 1963-11-08 1963-11-08 Improvements in or relating to vacuum ion pumps

Publications (1)

Publication Number Publication Date
US3307774A true US3307774A (en) 1967-03-07

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Family Applications (1)

Application Number Title Priority Date Filing Date
US409653A Expired - Lifetime US3307774A (en) 1963-11-08 1964-11-09 Vacuum ion pump

Country Status (4)

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US (1) US3307774A (de)
CH (1) CH427128A (de)
DE (1) DE1238608B (de)
GB (1) GB1021064A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4936452A (en) * 1989-06-05 1990-06-26 Pauley Helena R Bathroom tissue container
WO2008051603A2 (en) * 2006-10-26 2008-05-02 Brooks Automation Inc. Method and apparatus for shielding feedthrough pin insulators in an ionization gauge operating in harsh environments
DE102010055420A1 (de) * 2010-12-21 2012-06-21 Vacom Vakuum Komponenten & Messtechnik Gmbh Elektrodenvorrichtung für eine Ionenzerstäuberpumpe
US9960026B1 (en) * 2013-11-11 2018-05-01 Coldquanta Inc. Ion pump with direct molecule flow channel through anode

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3080104A (en) * 1958-09-25 1963-03-05 Gen Electric Ionic pump
US3239133A (en) * 1961-04-01 1966-03-08 Leybold Holding A G E Pump

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3080104A (en) * 1958-09-25 1963-03-05 Gen Electric Ionic pump
US3239133A (en) * 1961-04-01 1966-03-08 Leybold Holding A G E Pump

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4936452A (en) * 1989-06-05 1990-06-26 Pauley Helena R Bathroom tissue container
WO2008051603A2 (en) * 2006-10-26 2008-05-02 Brooks Automation Inc. Method and apparatus for shielding feedthrough pin insulators in an ionization gauge operating in harsh environments
WO2008051603A3 (en) * 2006-10-26 2009-04-23 Brooks Automation Inc Method and apparatus for shielding feedthrough pin insulators in an ionization gauge operating in harsh environments
US7847559B2 (en) 2006-10-26 2010-12-07 Brooks Automation, Inc. Method and apparatus for shielding feedthrough pin insulators in an ionization gauge operating in harsh environments
DE102010055420A1 (de) * 2010-12-21 2012-06-21 Vacom Vakuum Komponenten & Messtechnik Gmbh Elektrodenvorrichtung für eine Ionenzerstäuberpumpe
US9960026B1 (en) * 2013-11-11 2018-05-01 Coldquanta Inc. Ion pump with direct molecule flow channel through anode

Also Published As

Publication number Publication date
GB1021064A (en) 1966-02-23
DE1238608B (de) 1967-04-13
CH427128A (de) 1966-12-31

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