US3786296A - Evacuated elctron discharge tubes - Google Patents

Evacuated elctron discharge tubes Download PDF

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Publication number
US3786296A
US3786296A US00142943A US3786296DA US3786296A US 3786296 A US3786296 A US 3786296A US 00142943 A US00142943 A US 00142943A US 3786296D A US3786296D A US 3786296DA US 3786296 A US3786296 A US 3786296A
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United States
Prior art keywords
source
cathode
hollow
base
anode
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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US00142943A
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English (en)
Inventor
J Howorth
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English Electric Co Ltd
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English Electric Co Ltd
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Filing date
Publication date
Priority claimed from GB2361972A external-priority patent/GB1313829A/en
Application filed by English Electric Co Ltd filed Critical English Electric Co Ltd
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Publication of US3786296A publication Critical patent/US3786296A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J7/00—Details not provided for in the preceding groups and common to two or more basic types of discharge tubes or lamps
    • H01J7/14—Means for obtaining or maintaining the desired pressure within the vessel
    • H01J7/18—Means for absorbing or adsorbing gas, e.g. by gettering
    • H01J7/186—Getter supports
    • 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

  • An ion getter pump for providing a vacuum in a high power microwave discharge tube consists of a body of radio-active material which is arranged to act as the power source for the pump.
  • the pump has a glass support base concentrically surrounding a cathode.
  • Mounted within the tubular cathode is a layer of radio-active isotope material and a particle receiver from which extends an anode rod. Pins are fused through the base to support the cathode, the particle receiver and the isotope material.
  • a shield is provided to prevent sputtering of material on to the base.
  • a known getter ion pump however, has the serious'practical disadvantage of requiring an external electric power supply for its operation. Moreover, the getter ion pump will affect pumping only when the external power supply is switched in not when the tube is merely in storage. The present invention seeks to avoid these disadvantages.
  • an evacuated electron discharge tube apparatus comprises an electron discharge tube and an ion getter pumping device including a body of radioactive material arranged to act as the source of power therefor, said device being either within a vacuum tight housing constituted by the envelope of the tube or within a vacuum tight housing which includes the tube envelope, an envelope for said device and a communication channel between them.
  • the body of radio-active material may be an a particle source.
  • Preferred examples of such materials are cm and Amm. If either of these materials is employed means are preferably associated therewith for reducing undesired accompanying X-ray emission therefrom.
  • Such means may be constituted, for example, by thin mild steel sheet.
  • a source of B particles may be used for the body of radio-active material.
  • a preferred source of B particles is Tritium preferably Tritium dissolved in Ti.
  • the pumping device is so constructed as to combine the action of an ion getter pump with that of a chemical getter.
  • the device has an enclosure comprising a support base and a hollow cathode, and a body of radioactive material, a collector and an anode are supported from said base in the interior of said cathode, said enclosure being such as to provide a free path for gas from the interior to the exterior thereof and the whole arrangement being such that emitted particles are confined within said enclosure.
  • At least the interior surface of the cathode is preferably of chemical getter material, as also are, preferably, the collector and the anode.
  • the cathode and the base may each be in the form of a hollow cylindrical structure of particle-impermeable material open at one end only, the two said structures being of different diameters and mounted co-axially with their open ends overlapping and one within the other to leave an annular space between them where they overlap.
  • the cathode and the base are each in the form of a hollow cylinder open at one end only, the two cylinders being of different diameters and mounted co-axially with their open ends one within the other to leave an annular space between them, and the base supports the cathode cylinder and within the same, a source of 01 particles and a collector adjacent said source, there being an anode rod or wire which extends nearly to the closed end of the cathode cylinder and which is carried from the collector, a high resistance being connected between the collector and the a particle source, and a connection being provided between said source and said cathode cylinder.
  • the cathode and the base are each in the form of a hollow cylinder open at one end only, the two cylinders being of different diameters and mounted co-axially with their open ends one within the other to leave .an annular space between them, and the base supports the cathode cylinder and within the same, a source of B particles and a collector adjacent said source, there being an anode rod or wire which extends nearly to the closed end of the cathode and which is carried from said source, a high resistance being connected between the collector and the B particle source, and a connection being provided between the collector and the cathode cylinder.
  • the preferred ma terial for at least the interior of the cathode and also for the collector and the anode is Ti and a preferred material for the base is glass.
  • a shield, e.g. of M0, is preferably provided for preventing the sputtering of metal on the base.
  • a further form of pumping device comprises an outer support with a thin layer of radio-active material on its inner surface, a co-axial anode, at least one co-axial grid between said anode and said support and a pair of shields, one at each end of the anode and co-axial support structure.
  • the layer is an a particle source and there are two co-axial grids, the inner being connected to the source and to the shields and being a relatively transparent ioncollecting grid, and the outer being connected to the anode and being a relatively opaque a particle collecting grid.
  • the layer is a [3 particle source and there is only one grid which is connected to the shields, is operated at a negative potential and is a B particle collecting grid. In both these constructions electrons orbit around the central anode to cause ionisation.
  • FIGS. I and 2 are, respectively, a diagrammatic sectional elevation and a diagrammatic sectional plan of one form of pumping device for an apparatus in accordance with this invention
  • FIGS. 3 and 4 are views, respectively similar to those of FIGS. 1 and 2 of a modified form of pumping device having rather better disposition of the radio-active material
  • FIG. is a view showing one type of envelope construction
  • FIG. 6 is a view showing another type of enevelope construction.
  • the pump shown in the drawings is adapted to act both as what may be termed a radio getter pump, that is to say a getter pump which is powered by a radioactive isotope, and as a chemical getter.
  • 1 is a glass support base and 2 is a cathode in the form of a cylindrical can open at one end.
  • a layer of radioactive isotope material 3 on a support backing plate 4, and a particle receiver 5 from which extends an anode wire or rod 6 are supported from the base in the interior of the cathode.
  • the base 1 is also shaped as a cylinder, open at one end.
  • the value of resistance 11 could be l0 ohms.
  • At least the inner surface of the cylinder 2 may be made of a material such as Ti, Ta or Zr which is a satisfactory getter when in the form of a freshly sputtered layer.
  • the said cylinder 2 could be made entirely of such material or it could be of any suitable material with a sputtered layer of such getter material on its inner surface.
  • At present Ti is preferred.
  • the particle receiver 5, and the anode rod 6 are all also of getter material, eg all of Ti.
  • the isotope backing plate 4 may be of any suitable material, e.g., Al and the shield 10 may be of, for example, Mo.
  • the isotope layer 3 is of a radioactive material emitting 11 particles.
  • it is a radioactive material which is very low in 'y ray emission.
  • isotopes which comply with these requirements, namely Po Cm and Am the first named having a 'y ray emission of only about 0.001 percent.
  • this material has the defect of being volatileand the other two materials are therefore at present preferred. They both emit low energy X-rays but it is possible to reduce the X-ray count substantially by the use of X-ray protective material (not shown). Experiment indicates that it is possible, by the use of lmm thick sheet steel, to reduce the X-ray count to about 0.1 percent of the a emission rate.
  • the a particles will be confined to the interior of the device, the glass base 1 and cathode can 2, overlapping as shown, being of a particle impermeable material and sufficient to accomplish this. If, however, a different construction which does not in itself achieve this is adopted e.g., if a base made of a particle permeable material is used any known suitable external shielding (not shown) may be used to prevent escape of 0: particles away from the interior of the pump.
  • an a particle source constitutes a substantially constant current source and if such a source (the layer 3 in the illustrated embodiment) is separated from a collector (the collector 5) by a sufficiently high resistance (the resistance 11), a high voltage can be built up. This voltage is used, when the pump is in operation, as driving voltage for providing pumping action after the manner of an electro-static ion pump.
  • the device illustrated is adapted to provide pumping in three ways namely by chemical pumping, pumping by ionisation by a particles and electrostatic pumping as by an electrostatic ion pump. If one assumes a radioactive source giving approximately l0 disintegrations/sec., a resistance 11 of 10 ohms and a built-up voltage of 10 volts, the receiver 5 will be bombarded by 10 particles/sec and if one percent of this sputters new atoms available for chemical reaction with gas molecules, chemical gettering may be expected to remove 10 mols/sec.
  • the invention is not limited to the use of radioactive materials emitting a particles and materials emitting B particles e.g., Tritium dissolved in Ti may be used instead.
  • B particles would not sputter atoms from the collector and since such particles are negatively charged, the parts 5 and 3 of the illustrated embodiment would have to be interchanged if a B particle source is used instead of an a particle source. Because of the reduced sputtering obtained with a B particle source, a device employing such a source would (other things being equal) have a lower pumping speed than one employing an a particle source. On the other hand, some B particle sources do not emit 'y rays, and, by selecting such a source, 'y ray emission can be obviated.
  • FIGS. 3 and 4 are views, similar respectively to those of FIGS. 1 and 2 of another form of pumping device for an apparatus in accordance with this invention. This tral anode.
  • modified form of device has the advantage of providing a large area radioactive source. Both a and B sources work most efficiently when in thin film form and in many cases, therefore, large area sources are desirable.
  • an a particle source is constituted by a thin film 33 of suitable radioactive material on the inner surface of an openended cylindrical support backing member 44 which co-axially surrounds an anode rod 66.
  • a glass base disc 101 (not shown in FIG. 3) supports, directly or indirectly, the parts 33, 44 and 66 and also two end shields 110 (not shown in FIG. 3)
  • the outer grid 14 may be fairly opaque and designed to collect, say, about 70 percent of the 0: particles.
  • the inner grid 13 is intended to collect ions and may be relatively transparent.
  • the outer grid 14 and the anode 66 are connected together and operated at a suitable positive potential.
  • the inner grid 13, the source 33 with its backing support 44 and the shields 110 are connected together.
  • This pumping device operates after the manner of a so-called orbitron in the sense that electrons can orbit or circulate indefinitely around the central anode 66, thus causing ionisation. .
  • a high resistance 11 connectsthe anode with the inner grid.
  • FIGS. 3 and 4 show a pump device with an a particle source.
  • a design generally like that of FIGS. 3 and 4 (but not illustrated) could be used, differing, however, from that of FIGS. 3 and 4 in that there would be only a single grid between the central anode and the radio-active material (now, of course, a B particle source) on the inside of the cylindrical support.
  • This grid would be thick, designed to collectmost of the B particles, be held at negative potential, and be connected to the end shields.
  • the anode rod and the [3 particle source would be operated at positive potential.
  • the'getter device may be housed within the electron discharge tube envelope or it may have its own envelope communicating with that of the tube.
  • the getter device G is shown housed within the. envelope E which also houses the components (not shown) of the electron'discharge tube.
  • the getter device G is housed within an envelope e which, through the channel C, communicates with the interior of the electron discharge tube envelope E.
  • cathode means within said hollow interior and spaced from said anode means, said anode means and said cathode means being provided with electrical connector means for establishing an electrical potential therebetween when the electron discharge tube is in operation;
  • resistance means electrically connecting said source and said collector means for establishing a high voltage potential therebetween independently of electron discharge tube operation to effect ion getter pumping action even when the electron discharge tube is not in operation.
  • An apparatus as claimed in claim 3 wherein the particle source is Cm 5.
  • An apparatus as claimed in claim 3 wherein the particle source is Am 6.
  • cathode means comprises a hollow cathode and including a support base cooperating with said hollow cathode to form said means for defining a hollow interior, said collector means and said anode means being supported from said base in the interior of said hollow cathode, and the whole arrangement being such that emitted particles are confined within said hollow interior.
  • An apparatus as claimed in claim 11 wherein the confining of emitted particles within the hollow interior is obtained by making the hollow cathode and the base of particle-impermeable materials, forming them as structures open each at one end, and mounting them with their open ends overlapping, one within the other.
  • hollow cathode and base are each in the form of a hollow cylindrical structure of particle-impermeable material open at one end only, the two said structures being of different diameters and mounted co-axially with their open ends overlapping and one within the other to leave an annular space between them where they overlap.
  • hollow cathode and the base are each in the form of a hollow cylinder open at one end only, the two cylinders being of different diameters and mounted co-axially with their open ends one within the other to leave an annular space between them, and the base supports the cathode cylinder and within the same, said source in which the radioactive material is a source of 0: particles and said collector means disposed adjacent said source, said anode means being in the form of a rod or wire which extends nearly to the closed end of the cathode cylinder and which is carried from the collector means.
  • hollow cathode and the base are each in the form of a hollow cylinder open at one end only, the two cylinders being of different diameters and mounted co-axially with their open ends one within the other to leave an annular space between them, and the base supports the cathode cylinder and within the same, said source being a source of [3 particles and said collector means being adjacent said source, said anode means being in the form of an anode rod or wire which extends nearly to the closed end of the cathode cylinder and which is carried from said source.
  • An apparatus as claimed in claim 1 wherein said means for defining a hollow interior comprises an outer cylindrical support with a thin layer of radioactive material on its inner surface and a pair of shields, one at each end of the cylindrical support, said anode means being co-axial within said support, and at least one coaxial grid between said anode means and said cylindrical support.
  • An ion getter pumping device as defined in claim 1 including an envelope housing said device separate from but communicating with the envelope of the associated electron discharge tube.

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  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
  • Electron Tubes For Measurement (AREA)
US00142943A 1970-05-15 1971-05-13 Evacuated elctron discharge tubes Expired - Lifetime US3786296A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2361972A GB1313829A (en) 1969-09-18 1970-05-15 Transistors and aproduction thereof

Publications (1)

Publication Number Publication Date
US3786296A true US3786296A (en) 1974-01-15

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Application Number Title Priority Date Filing Date
US00142943A Expired - Lifetime US3786296A (en) 1970-05-15 1971-05-13 Evacuated elctron discharge tubes

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US (1) US3786296A (OSRAM)
DE (1) DE2124167B2 (OSRAM)
FR (1) FR2091704A5 (OSRAM)
GB (1) GB1294604A (OSRAM)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5459366A (en) * 1993-04-09 1995-10-17 Martin Marietta Energy Systems, Inc. Gamma radiation field intensity meter
US20030090202A1 (en) * 2001-11-12 2003-05-15 Alessandro Gallitognotta Discharge lamps using hollow cathodes with integrated getters and methods for manufacturing same
CN100550267C (zh) * 2004-08-27 2009-10-14 佳能株式会社 图像显示装置

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2715993A (en) * 1952-06-06 1955-08-23 W M Welch Mfg Company Ionization pump

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2715993A (en) * 1952-06-06 1955-08-23 W M Welch Mfg Company Ionization pump

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5459366A (en) * 1993-04-09 1995-10-17 Martin Marietta Energy Systems, Inc. Gamma radiation field intensity meter
US20030090202A1 (en) * 2001-11-12 2003-05-15 Alessandro Gallitognotta Discharge lamps using hollow cathodes with integrated getters and methods for manufacturing same
US20040164680A1 (en) * 2001-11-12 2004-08-26 Saes Getters S.P.A. Discharge lamps using hollow cathodes with integrated getters and methods for manufacturing same
US20050136786A1 (en) * 2001-11-12 2005-06-23 Alessandro Gallitognotta Hollow cathodes with getter layers on inner and outer surfaces
US6916223B2 (en) * 2001-11-12 2005-07-12 Saes Getters S.P.A. Discharge lamps using hollow cathodes with integrated getters and methods for manufacturing same
CN100550267C (zh) * 2004-08-27 2009-10-14 佳能株式会社 图像显示装置

Also Published As

Publication number Publication date
GB1294604A (en) 1972-11-01
FR2091704A5 (OSRAM) 1972-01-14
DE2124167B2 (de) 1973-07-26
DE2124167A1 (de) 1971-11-25

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