US3009629A - High vacuum pumps - Google Patents

High vacuum pumps Download PDF

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Publication number
US3009629A
US3009629A US746256A US74625658A US3009629A US 3009629 A US3009629 A US 3009629A US 746256 A US746256 A US 746256A US 74625658 A US74625658 A US 74625658A US 3009629 A US3009629 A US 3009629A
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United States
Prior art keywords
pump
chamber
gases
trap
pumping
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Expired - Lifetime
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US746256A
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English (en)
Inventor
Garin Paul
Prugne Pierre
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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
    • 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

Definitions

  • vapour tension of the liquid that is used limits the final vacuum that is obtained; means (often constituted by liquid air traps) are generally provided to prevent the mercury (or oil) vapour from entering the space to be evacuated; such means are described for instance in pages 214 and 215 of the book of S. Dusham (Scientific Foundations of Vacuum Technique, Ed. Wiley & Sons, New York 1949);
  • the object of the present invention is to provide a getter pump including a low temperature trap and making it possible to obtain high pumping speeds for all gases (even for rare gases) at low pressure.
  • This pump is essentially characterized in that high pumping flow rates for all gases at low pressure, either chemically active or not, are obtained by combining the getter effect due to a vaporized metal, sensitive to chemically active gases, and the condensation of the neutral gases on the cold wall of a very low temperature trap.
  • a pump according to this invention therefore includes, in combination, means for vaporizing a getter substantially in continuous manner and means for condensing the gases that have not been extracted by the getter.
  • FIG. 1 is a diagrammatic axial section of a pump made according to the invention.
  • FIG. 2 is an axial section of the vaporizing crucible mounted on the high voltage electrode and forming a portion of the getter vaporizing device of the pump of FIG. 1.
  • FIGS. 3, 4, 5 and 6 show, in logarithmic coordinates, the flow rates plotted in ordinates in liters per second of the pump of FIGS. 1 and 2, respectively for air, nitrogen, oxygen and hydrogen, the pressures being plotted in abscissas, in millimeters of mercury.
  • the pump includes a pump body C constituted by a metal plate 1 and a cylindrical ICE casing 2 fixed thereon and cooled by circulation of water in conduits 3.
  • a high voltage electrode 4 (to be more fully described hereinafter) supports a crucible 5 made of a refractory material such as tantalum carbide.
  • a mechanical feed system (diagrammatically illustrated by its casing 8) of a known type (including for instance two driving rollers rotating in opposed directions), fixed under plate 1 on the outside of the pump body C, ensures, through a guide 9, the continuous feed of a metal wire 10 along the axis of crucible 5.
  • the feed mechanism 8 is located on the outside of the pump body so as to be protected against the depositing of condensed metal.
  • This chamber E is fixed on casing 2.
  • This trap includes, on the one hand, a cylindrical outer casing 14 in which is placed the vessel 15a which contains the liquefied gas 15, thermally insulated and precooled by suitable means constituted for instance by a liquid nitrogen jacket 16 and, on the other hand, a system of screens 17 placed at the temperature 'of jacket 16. Vessel 15a is fed with liquefied gas through tube 18.
  • Jacket 16 and screens 17 are disposed in such manner as to provide a sufficient passage for the flow of gas toward an intermediate zone F evacuated by a preliminary pumping system constituted for example, by a mechanical pump G.
  • a metallic sealing valve 19 for molecular vacuum located at thelower part of trap P, permits of insulating the pump system C, D, P, F and the chamber E to be evacuated from this preliminary pumping tem G.
  • FIG. 2 shows that the high voltage electrode 4 includes a steel rod 4a, surrounded by a tube 26 of steatite and a tungsten rod 4b carried by rod 4a.
  • Tube 26 is fixed on rod 4a by a brass cup shaped member 27 brazed at 28 on rod 4a and welded at 29 to tube 26 itself.
  • a brass ring 30, welded at 31 to the steatite tube 26, is provided with two grooves 32 and 33 in which are housed respectively a metallic seal 34 and a rubber seal 35, a connection 36 making it possible to establish a vacuum between these two seals.
  • the refractory material crucible 5 is fixed to the end of thetungsten rod 412 by means of a graphite sleeve 39 and of pin 40.
  • a cap 41 made of lava protects steatite tube 26 against the depositing of condensed metal thereon and a metallic casing 42 surrounds the lower portion of electrode 4a, 4b,
  • the pump made according to the invention has the following characteristics given merely by way of indication: the vaporizing metal is titanium; the source of cold of the trap is liquid helium, the boiling temperature of which is 4.2 K.; the temperature of chamber E is close to 300 K., that of jacket 16 close to 100 K.
  • the rate of vaporization of titanium which depends upon the rate of feed of the metal wire may be adjusted from 2 milligrams per minute to 20 milligrams per minute.
  • titanium fixes the chemically active gases such as hydrogen, oxygen and nitrogen.
  • the rare gases which are but little fixed by titanium, condense upon the cold wall of the liquid helium trap (of course with the exception of helium). These rare gases form only one percent of the composition of air, so that the pumping speed of the trap must be equal to at least one hundredth of the rate of pumping of the whole of the pumping system.
  • the device for heating the crucible constitutes in itself an ionisation pumping system which is quite sufficient to eliminate the helium present in air.
  • the geometry of the system including the chamber E to be evacuated, the titanium pump C and the trap P is such that air or another gas pumped from chamber E first passes through titanium pump; therefore, the gases coming into contact with liquefied gas are mostly rare gases and in particular argon.
  • Diameter of the titanium wire 0.5 mm. Nature of the crucible: tentalum'carbide Temperature of the crucible: 2000 C.
  • Curve I shows the pumping rate as a function of the pressure, the measurements being made from the initial vacuum obtained in chamber E which is little degassed and Where there are still some micro-leaks,
  • curve II shows the pumping rates from the final vacuum obtained in the chamber which has been better degassed and the gas-tightness of which ha been improved.
  • FIG. 3 shows a curve III giving the pumping rates for air when only the titanium vaporizing system is in operation and the liquefied helium trap is not being used (only the chemically active gases being mainly pumped).
  • the comparison with the curves of FIG. 4 which relate to notrogen shows that the ratio of nitrogen pumping speed to that of the air pumping speed for a residual pressure in the chamber to be evacuated equal to 210* millimeters of mercury is about 30 (FIG. 4 and curve III of FIG. 3). When the liquid helium trap is brought into operation, this ratio is reduced to about 1 (FIG. 3: curves I and II; FIG. 4: curves I and II).
  • a pump according to the invention comprises in combination:
  • means which act chiefly on the chemically active gases such as oxygen, nitrogen and hydrogen, these means being capableof a 4 higher efliciency since this efiiciency depends upon the area of condensation;
  • condensation means liquid helium trap which pump all the other gases with the exception of helium.
  • a pump according to the present invention makes it possible to obtain for air a rate of pumping equal to that obtained for chemically active gases. Up to the present time, the known apparatus did not achieve this characteristic although they made use of a heavy electronic system to eliminate the rare gases.
  • a high vacuum pump which comprises, in combination, a pump body, means for continuously feeding an elongated element of getter metal into said pump body, means in said pump body for heating said getter metal element as it is being fed and vaporizing it, a chamber to be evacuated in communication with one end of said body, a gas trap chamber in communication with the other end of said body, a vessel in said gas trap chamber containing a gas liquefied at low temperature, means for preventing heat transfer from the outside of said gas trap chamber to said vessel and means for continuously evacuating said gas trap chamber.
  • a vacuum pump according to claim 1 in which said vessel contains liquefied helium.
  • a vacuum pump according to claim 1 in which said means for preventing heat transfer include a jacket fed with a gas liquefied at a low temperature higher than that of the liquefied gas contained in said vessel.
  • a pump according to claim 1 including, between said pump body and said gas trap chamber, a passage of small cross-section and a helical bafile in said passage.
  • a vacuum pump according to claim 1 further comprising, between said chamber to be evacuated and the portion of said pump body adjacent thereto, a plurality of concentric cylinders for stopping the metallic vapours.
  • a vacuum pump according to claim 1 further including means forming a space adjoining said gas trap chamber and adapted to be evacuated by said evacuating means, and valve means adapted to separate, when closed, said space from said evacuating means.
  • a high-vacuum pump comprising a pump body with a first and a second opening, said pump body communicating through said first opening with a vessel to be evacuated, means for continuously feeding a gettering' substance in said pump body, means in said pump body for continuously vaporizing said getter-ing substance in 5 said pump body, screen means located in said first-opening for preventing a material quantity of said gettering substance, when vaporized, to reach said vessel through said first opening, a gas trap chamber communicating with said pump body through said second opening, a container located in said gas trap chamber and containing a liquefied gas at a very low temperature, a cold jacket located in said gas trap chamber, around said container, for isolating said container from heat transing means openatively connected to said gas trap chamber for continuously evacuating said gas trap chamber.

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  • Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
US746256A 1957-07-05 1958-07-02 High vacuum pumps Expired - Lifetime US3009629A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR1080257X 1957-07-05

Publications (1)

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US3009629A true US3009629A (en) 1961-11-21

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ID=9609525

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US746256A Expired - Lifetime US3009629A (en) 1957-07-05 1958-07-02 High vacuum pumps

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US (1) US3009629A (fr)
BE (1) BE568937A (fr)
CH (1) CH349739A (fr)
DE (1) DE1080257B (fr)
FR (1) FR1180717A (fr)
LU (1) LU36210A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3144756A (en) * 1962-07-23 1964-08-18 Ion Physics Corp Vacuum system cooling trap
US3156406A (en) * 1962-03-26 1964-11-10 Varian Associates High vacuum pumping method and apparatus
US3209150A (en) * 1962-02-12 1965-09-28 Lockheed Aircraft Corp Coolable multi element infrared detector assembly
US3258193A (en) * 1959-04-27 1966-06-28 Ibm Vacuum method
US3300992A (en) * 1964-11-03 1967-01-31 Pittsburgh Activated Carbon Co High vacuum pumping with impregnated adsorbents
US4770007A (en) * 1986-12-04 1988-09-13 Mitsubishi Denki Kabushiki Kaisha Vertically compact cryostat
WO2022261526A1 (fr) * 2021-06-11 2022-12-15 Helion Energy, Inc. Pompe de diffusion à gettering hybride

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1501070A (en) * 1920-08-24 1924-07-15 Western Electric Co Vacuum pump
US2850225A (en) * 1955-11-10 1958-09-02 Wisconsin Alumni Res Found Pump

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2167852A (en) * 1935-10-22 1939-08-01 Rca Corp Electron discharge device
US2636664A (en) * 1949-01-28 1953-04-28 Hertzler Elmer Afton High vacuum pumping method, apparatus, and techniques
DE1010695B (de) * 1955-08-05 1957-06-19 Commissariat Energie Atomique Verfahren zur Vakuumerzeugung mittels einer Diffusionspumpe

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1501070A (en) * 1920-08-24 1924-07-15 Western Electric Co Vacuum pump
US2850225A (en) * 1955-11-10 1958-09-02 Wisconsin Alumni Res Found Pump

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3258193A (en) * 1959-04-27 1966-06-28 Ibm Vacuum method
US3209150A (en) * 1962-02-12 1965-09-28 Lockheed Aircraft Corp Coolable multi element infrared detector assembly
US3156406A (en) * 1962-03-26 1964-11-10 Varian Associates High vacuum pumping method and apparatus
US3144756A (en) * 1962-07-23 1964-08-18 Ion Physics Corp Vacuum system cooling trap
US3300992A (en) * 1964-11-03 1967-01-31 Pittsburgh Activated Carbon Co High vacuum pumping with impregnated adsorbents
US4770007A (en) * 1986-12-04 1988-09-13 Mitsubishi Denki Kabushiki Kaisha Vertically compact cryostat
WO2022261526A1 (fr) * 2021-06-11 2022-12-15 Helion Energy, Inc. Pompe de diffusion à gettering hybride

Also Published As

Publication number Publication date
BE568937A (fr)
FR1180717A (fr) 1959-06-09
DE1080257B (de) 1960-04-21
LU36210A1 (fr)
CH349739A (fr) 1960-10-31

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