US1684263A - Hot-cathode device - Google Patents

Hot-cathode device Download PDF

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Publication number
US1684263A
US1684263A US738246A US73824624A US1684263A US 1684263 A US1684263 A US 1684263A US 738246 A US738246 A US 738246A US 73824624 A US73824624 A US 73824624A US 1684263 A US1684263 A US 1684263A
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US
United States
Prior art keywords
cathode
uranium
electron
anode
current
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
Application number
US738246A
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English (en)
Inventor
William D Coolidge
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Co
Original Assignee
General Electric Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by General Electric Co filed Critical General Electric Co
Priority to US738246A priority Critical patent/US1684263A/en
Priority to FR603584D priority patent/FR603584A/fr
Priority to DEA45885D priority patent/DE483337C/de
Priority to GB23210/25A priority patent/GB240166A/en
Application granted granted Critical
Publication of US1684263A publication Critical patent/US1684263A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/06—Cathodes
    • H01J35/064—Details of the emitter, e.g. material or structure

Definitions

  • the present invention relates to the construction of electrical discharge devices, in particular X-ray tubes, which contain a cathode operating at a high temperature, and in which the cathode is apt to become coated during operation by a. material having a higher electron emission than the material constituting the cathode.
  • an X-ray tube with a target consisting of a metal of higher atomic number than tungsten, such as uranium or thorium, for example.
  • a metal of higher atomic number than tungsten such as uranium or thorium, for example.
  • X- ray output of such a tube is greater than that of a similar tube with a tungsten target.
  • the cathode is maintained at a sufficiently high temperature, except for the ends unavoidably cooled by the leads,to prevent the deposition of material, and electron emission from the ends is controlled by the construction of the focusing member in its relation to the cathode so as to shield these points and increase space charge at these regions.
  • the cathode is so positioned with respect to the focusing device that electron emission from the entire cathode is controlled by space charge, so that for a given impressed voltage a given current is obtained regardless of variations of electron emission provided that the emission of electrons always exceeds a predetermined value for the given voltage.
  • FIG. 1 an X-ray tube as illustrating one of the devices in which my invention will be embodied
  • Figs. 2. 3 and 4 are detailed views of different cathode structures whereby the results above described may be secured
  • Fig. 5 is a sectional view of an anode having a target surface of metal of high atomic number. such as uranium or thorium.
  • the X-ray tube shown in Fig. 1 comprises as usual a bulb 2, a cathode 3 and an anode 4.
  • the cathode comprises a filament adapted to be heated by conductors connected to an external screw base 5. These conductors are merely indicated by a dotted line at 6 as passing through a stem 7 projecting into the X-ray tube.
  • the anode is cooled by 'water or other vfluid Vpassing' through the of uranium, and a backing plate 10 which preferably consists of copper.
  • the copper tubes 8, 8 are connected by means of a spiral 11 which is brazed or otherwise placed in ood heat conducting relation with the bac plate 10.
  • the target plate 9 when consisting of uranium is brazed to the back plate 10 by a binder layer 12 consisting of a copper-silver alloy, preferably an alloy consisting of 28 parts Acopper and 72 parts silver which is usually known as the eutectic alloy.
  • a binder layer 12 consisting of a copper-silver alloy, preferably an alloy consisting of 28 parts Acopper and 72 parts silver which is usually known as the eutectic alloy.
  • the three members that is the uranium-,face plate, the brazing alloy and the copper back plate, are heated in contact in a vacuum to the melting point of the bra-zing alloy. Under these conditions, if the time at the melt.-
  • the alloy will bind the face plate and back plate without harmful allowa e of the uranium with the constituents o? the brazin alloy.
  • This rocess may be carried out wit out melting t 1e coper, as the eutectic alloy has a materially ower kmelting point than copper.
  • the cathode 3 consists of a filament 13 of tungsten. It is surrounded by a' cylindrical member 14 which may consist of molybdenum and which preferably is provided with a flange 18, whereby positive ions which may be produced during exhaust of the tube are intercepted and prevented from injuring tube part-s back of the cathode.
  • the cathode spiral A13 preferably is connected at one end to the tube 14 and at the opposite end to a central wire or rod 15 which projects beyond the cathode spiral and preferably sli htly beyond the focusing tube 14.
  • the cathode is situated far enough Within the focusing member as shown in Fig. 4 not all of the 4electrons emitted from the cathode can reach the anode at a given operating voltage of the X-ray tube. In other words by means of a construction such as shown in this figure the current in the X-ray tube is determined by the impressed voltage, and not by electron emission.
  • the cathode spiral 13 is located close to the mouth of the focusing cylinder 14 and the electrons issuing from the main or spiral part of the cathode filament, therefore, are
  • the cathode filament is operated at a sulliciently high temperature to prevent uranium or thorium from remaining on the heated cathode filament.
  • a tungsten cathode when operated at about 2500 K. ork higher will not permit uranium from the anode to condense on .the highly heated .parts of the cathode spiral.
  • the ends of the cathode are connected tothe cylinder 14 and to the rod 15 at points removed from the periphery of the focusing ⁇ cylinder 14.
  • a material ofl high electron emissivity such as thorium or uranium, whether constituting part of the anode or being otherwise present, is an adeol vantage in improving the electron emissivity of the cathode, provided irregularities of emission are prevented as above described.
  • positive ion bombardment of the cathode tends to remove the layer of thorium, or other material of high emissivity, from the cathode surface, the operation of an electron device at high voltage would soon deactivate thel cathode if a renewal of the active surface were not provided for from a supply of this material in the device.
  • An electrical discharge device containing a cathode which is constructed to permit operation at a temperature of electron emission together with a material having a higher electron emissivity than said cathode and being capable of varying the electron emission at the cathode, the provision of means within the device for limiting the space current therein to a predetermined value for a given impressed voltage.
  • An Xfray device comprising a. bulb, a member therein comprising a metal having a higher electron emissivity than tungsten, a. tungsten cathode which is constructed to be heated by passage of current, and an electrostatic device so arranged about said cathode that an increase of electron current due to increased emission from volatilizable metal deposited upon the cathode is suppressed.
  • An X-ray device comprising an evac ⁇ uated bulb, an anode or target therein consisting of uranium, a cathode of tungsten which is adapted to be heated, and a focusing device said device being so arranged with respect to said cathode that an'increase ot electron current from the cathode due to the distillation of uranium thereon will be substantially prevented by space charge for a range of operating voltage.
  • An X-ray device having an anode or target consisting in part at least of a material having a lower work function than the material constituting the cathode, said device having an electrostatic focusing device so positioned with respect to the cathode that the space current in said device is lmaintained at a substantially constant value at a given operating voltage in spite of the deposition vof said anode material upon the cathode.
  • the method of preventing an increase of electron emission from a thermionic cathode by the deposition thereon of a ma terial of higher electron emissivity which consists in operating the main portion of said cathode at a temperature high enough to volatilize said material and preventing electrostatically an increase of current from said cathode at regions which unavoidably operate at a temperature at which said material can vary the emission of electrons.
  • An X-ray device having a thermionic cathode, portions of which are cooled by heat conduction to connected metal parts one of which parts comprises a focusing device, an anode or target consisting in part at least of a material having a lower work function,
  • An X-ray device having a thermionic cathode, an anode or target consisting in part at least of a material having a higher electron emissivity than the cathode, and means within the device for maintaining the space current therein substantially constant regardless of any deposition of the anode material upon the cathode.
  • an electrical discharge device containing a cathode constructed to permit operation at a temperature of electron emission and an anode including a material of higher electron emissivity than the cathode and capable of varying electron emission of the cathode, the provision of means within the device for limiting the space current therein to a predetermined value for a given impressed voltage.

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  • X-Ray Techniques (AREA)
  • Microwave Tubes (AREA)
US738246A 1924-09-17 1924-09-17 Hot-cathode device Expired - Lifetime US1684263A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US738246A US1684263A (en) 1924-09-17 1924-09-17 Hot-cathode device
FR603584D FR603584A (fr) 1924-09-17 1925-09-09 Perfectionnements aux dispositifs à décharge électronique
DEA45885D DE483337C (de) 1924-09-17 1925-09-13 Gluehkathodenroehre, insbesondere Roentgenroehre
GB23210/25A GB240166A (en) 1924-09-17 1925-09-17 Improvements in and relating to electron discharge devices

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US738246A US1684263A (en) 1924-09-17 1924-09-17 Hot-cathode device

Publications (1)

Publication Number Publication Date
US1684263A true US1684263A (en) 1928-09-11

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Family Applications (1)

Application Number Title Priority Date Filing Date
US738246A Expired - Lifetime US1684263A (en) 1924-09-17 1924-09-17 Hot-cathode device

Country Status (4)

Country Link
US (1) US1684263A (fr)
DE (1) DE483337C (fr)
FR (1) FR603584A (fr)
GB (1) GB240166A (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3526799A (en) * 1967-05-26 1970-09-01 Gen Electric Electron discharge device subject to hydrocarbon background pressure and having carbon-dissolving electrodes
US4322653A (en) * 1978-12-23 1982-03-30 Licentia Patent-Verwaltungs-G.M.B.H. Apparatus including an X-ray tube with shielding electrodes
US4969173A (en) * 1986-12-23 1990-11-06 U.S. Philips Corporation X-ray tube comprising an annular focus
JP2016529685A (ja) * 2013-09-10 2016-09-23 モックステック・インコーポレーテッド 電子エミッターのための二重管支持体

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2003214929B2 (en) * 2002-01-31 2006-07-13 The Johns Hopkins University X-ray source and method for producing selectable x-ray wavelength

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3526799A (en) * 1967-05-26 1970-09-01 Gen Electric Electron discharge device subject to hydrocarbon background pressure and having carbon-dissolving electrodes
US4322653A (en) * 1978-12-23 1982-03-30 Licentia Patent-Verwaltungs-G.M.B.H. Apparatus including an X-ray tube with shielding electrodes
US4969173A (en) * 1986-12-23 1990-11-06 U.S. Philips Corporation X-ray tube comprising an annular focus
JP2016529685A (ja) * 2013-09-10 2016-09-23 モックステック・インコーポレーテッド 電子エミッターのための二重管支持体

Also Published As

Publication number Publication date
GB240166A (en) 1926-03-11
FR603584A (fr) 1926-04-19
DE483337C (de) 1929-09-30

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