US2349468A - Electron emission device - Google Patents

Electron emission device Download PDF

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Publication number
US2349468A
US2349468A US451902A US45190242A US2349468A US 2349468 A US2349468 A US 2349468A US 451902 A US451902 A US 451902A US 45190242 A US45190242 A US 45190242A US 2349468 A US2349468 A US 2349468A
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US
United States
Prior art keywords
metallic
envelope
conductors
spark
cathode
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
US451902A
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English (en)
Inventor
Charles M Slack
Louis F Ehrke
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.)
Westinghouse Electric Corp
Original Assignee
Westinghouse Electric Corp
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
Priority to BE483447D priority Critical patent/BE483447A/xx
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Priority to US451902A priority patent/US2349468A/en
Application granted granted Critical
Publication of US2349468A publication Critical patent/US2349468A/en
Priority to GB20797/47A priority patent/GB638642A/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
    • H01J35/22—X-ray tubes specially designed for passing a very high current for a very short time, e.g. for flash operation

Definitions

  • the present invention relates to electron discharge devices and particularly to such devices as a-high voltage X-ray tube of the type shown in the patent to C. M. Slack, No. 2,311,705,'issued February 23, 1943, and assigned to the same assignee as the present invention.
  • the discharge device operates upon what is termed field emission of electrons and is accordingly designed to pass high currents of the magnitude of amperes.
  • a high potential gradient is employed to initiate an arc dischargebetween an auxiliary electrode and the cathode of the device solely by field emission of electrons from the cathode, which are discharge thus becomes the source of electrons for the high currentfiow between the cathode and anode.
  • this high current flow is necessarily of extremely short duration being of the order of but a fraction to a few microseconds as' otherwise the device would be destroyed.
  • leading-in conductors for the various electrodes are spaced from each other the customary distance for the high voltage applied to prevent spark-over therebetween by ionization of the air-gap. This accordingly limited the dimensions of the device which formerly required an increase in size as-the operating voltage increased.
  • Another object of the present invention is the provision of an electron discharge device wherein the metallic parts of opposite instantaneous polarity are spaced from each other a reduced distance to enable the device to be greatly reduced in size and without spark-over occurring between such parts by ionization of the air-gap therebetween regardless of the applied voltage.
  • Another object of the present invention is the provision of an electron discharge device such as an X-ray tube which is operable by field emission of electrons, and wherein the air-gap spacing between metallic parts carrying opposite instantaneous polarity is greatly reduced to thereby reduce the overall dimensions of the tube without'attendant spark-over between such metallic entrant sleeve. "it will be seen that this auxiliary electrode l0,
  • Another object of the present invention is the provision of a field emission X-ray tube wherein variouspartsof the tube may be assembled in correctly spaced relation prior to insertion and sealing into the tube for complete fabrication thereof.
  • Fig. 1 is a fragmentary view partly in crosssection of an electron discharge device constructed in accordance with the present invention
  • Fig. 2 is an end view of the cathode electrode as viewed at the line II-II of Fig. 1 and looking in the direction indicated by the arrows;
  • Fig. 3 is a sectional view taken on the line IIIIII of Fig. 2" and looking in the direction indicated by the arrows;
  • Fig. 4 is an enlarged fragmentary sectional view of the cathode end of the device taken on the line IVIV of Fig. 2;
  • Fig. 5 is a fragmentary View partly in crosssection similar-to Fig. 1 showing a slight modification which the structure of the device may take;
  • Fig. 6 is a sectional view taken on the line VI-VI of Fig. 5;
  • Fig; 7 is a fragmentary view of a still further modification which the electrode construction may take, and
  • Fig. Bis a fragmentary view partly in crosssection of yet another modification which the electrode structure may take.
  • the electron discharge device shown in Fig. 1 comprises an X-ray tube of the type operable by field emission of electrons, such as shown and described in the above-mentioned pending application.
  • Such X-ray tube comprises an evacuated envelope 5 havingan anode 6 of a refractory metal, such as tungsten or the like, and supported by a leading-in conductor or rod 1 secured to a metallic'terminal 8,-the latter of which forms an hermetic seal with the envelope 5 as hereinafter described.
  • This block i4 is provided with an elliptical opening IS in the wall thereof and in the direction of the anode, the open end of the block converges to form parallel side walls I! extending normal to the longitudinal axis of the tube, as can be appreciated from Figs. 2, 3, and 4.
  • a cathode electrode l8 which, as shown, is in the form of a rectangular plate and of a low work function material, such as thorium, molybdenum or the like, is disposed in the rectangular opening I6 with the edge thereof spaced but a few millimeters from the edge formed by the converging side walls [1.
  • Such cathode is supported by a leading-in conductor in the form of a rod or the like l9 connected to a metallic terminal 26, the latter of which is hermetically sealed, in the same manner as the terminal 8, to an annular wall 22 formed interiorly of the reentrant tube 9.
  • the auxiliary electrode ID In order to conduct energy to the auxiliary electrode ID, the latter is provided with a lug 23 formed on the periphery of the metallic sleeve l2 which has a recess 24 telescopically engaged by a leading-in conductor or rod 25 likewise secured to a metallic terminal 26 sealed to the envelope '5.
  • the various terminals 8, 20 and 26 are of cup-shape with the peripheral edge thereof tapered and sealed to the vitreous envelope.
  • Such metallic terminals may be of copper with the leading-in conductors or rods soldered to the interior thereof or, if desired, they may be formed of an alloy having a coefficient of expansion closely approximating that of the vitreous envelope.
  • the electrostatic field readily influences the arc discharge which, together with reduction in space charge, results in the flow of electrons to the anode with substantially no accompanying flow of metallic particles or positive ion bombardment of the anode and the electron discharge alone serving for the flow of the entire available energy of a magnitude of amperes.
  • Fig. 1 which comprises a high tension transformer 30 provided with a primary winding 32 and a high voltage secondary Winding 33 which generates a voltage ranging from 20 to several hundred kilovolts.
  • the center point of the secondary winding is connected to ground high potential gradient is present which draws auxiliary electrode the air at the applied potential.
  • the bank of condensers 36 are grounded at 40 and a spark-gap 4
  • the condensers are charged by the transformer 30 during the full wave of the alternating circuit to the maximum energy delivered by the transformer which, however, is insufficient to cause breakdown of the spark-gap 31.
  • the control device 38 is set into operation. As shown in the above-mentioned pending application, this applies an additional charge to the bank of condensers 36 which exceeds the breakdown value of the spark-gap lit with the spark-gap 4
  • a high resistance 43 is connected in parallel with the X-ray tube, but since the current flowing through this resistance is but a minute fraction of the several hundreds or more amperes flowing between the anode 6 and cathode l8, such resistance serves to control the uniformity of breakdown voltage of the spark-gap 31 for its particular setting
  • the air-gap spacing between the metallic leadingin conductors or terminals for the anode, auxiliary electrode and cathode are shown spaced apart the customary distance required to prevent spark-over therebetween by ionization of
  • the entire period" of energization of the discharge device is much shorter than the period required 'forion'ization of the air-gap between metallic parts, which results in sparkover.
  • FIG. 5 and 6 A slight mechanical modification is shown in Figs. 5 and 6 wherein the metallic terminals and 26 are dispensed with and in lieu thereof the leading-in conductors 44, and 46 are sealed directly to the glass wall of the envelope.
  • fabrication of the tube of this mocli' fication is facilitated in that the leading-in conductors M and 46 form a threaded engagement with their respective electrode assembly.
  • the anode 6 in this particular modification is supported by a metallic sleeve 41 fitting over a reentrant stem 48 and held in place by a clamp 49.
  • the anode stem is provided with a threaded angular portion 50 which is readily engaged by the leading-in conductor 44 prior to sealing-in the latter to the envelope wall.
  • the auxiliary electrode I0 is provided with a metallic strip 52 having a threaded angular portion 53 also readily engageable by the leading-in conductor 45 prior to its being sealed into the glass wall of the envelope.
  • main and auxiliary electrodes may-be assembled in the correctly spaced relationship outside the envelope andsealed-in as a unit, thus' permitting more accurate and rapid assembly.
  • An electron discharge device comprising an envelope, electrodes in said envelope between which a high potential difference occurs during operation of said device, metallic leading-in conductors connected to said electrodes for transmitting energy thereto and having a spacing therebetween exteriorly of said device less than that necessary to prevent spark-over at the applied voltage, and means for energizing said device for a period of time so short that ionization of air with attendant spark-over between the closely spaced metallic conductors does not occur regardless of the high instantaneous potential difference existing between said conductors.
  • An electron discharge device comprising an envelope, electrodes in said envelope between which a high potential difference occurs during operation of said device, metallic leading-in conductors sealed to said envelope and connected to said electrodes for transmitting energy thereto having a spacing therebetween exteriorly of said device below that electrically necessary to prevent spark-over at the applied voltage, and means for energizing said device for a period of time less than that required to cause ionization of the air between the closely spaced metallic conductors to prevent the occurrence of spark-over therebetween regardless of the high instantaneous potential difference existing between said conductors.
  • An electron discharge device comprising an envelope, electrodes in said envelope between which a high potential difference occurs during operation of said device, metallic leading-in conductors connected to said electrodes for transmitting energy thereto and spaced apart exteriorly of said envelope a distance considerably less than the normal electrical requirements necessary to prevent spark-over therebetween at the applied voltage, and means for energizing said device to cause the field emission of electrons accompanied by an electron discharge between said electrodes and for a period of time less than that required to cause ionization of the air with resultant spark-over between said metallic conductors regardless of the high instantaneous potential difference existing between said conductors.
  • An electron discharge device comprising an envelope, electrodes in said envelope between which a high potential difference occurs during operation of said device, metallic leading-in conductors sealed to said envelope and connected to said electrodes for transmitting energy thereto and having a spacing therebetween exteriorly of said device considerably less than that normally electrically necessary to "prevent spark-over therebetween at the applied voltage, and an energizing circuit for supplying energy to said device for a period of time so short that ionization of air with attendant spark-over between the closely spaced metallic conductors does not occur regardless of the high instantaneous potential difference existing between said conductors.
  • An X-ray tube comprising an envelope, electrodes in said envelope between which a high potential difierence occurs during the production of X-rays, metallic leading-in conductors connected to said electrodes for transmitting energy thereto and having a spacing therebetween eX- teriorly of said tube less than that necessary to prevent spark-over at the applied voltage, and means for energizing said tube for a period of time so short that ionization of air with attendant spark-over between the closely. spaced metallic conductors cannot occur regardless of the high instantaneous potential difference existing between said conductors.
  • An X-ray tube comprising an envelope, electrodes in said envelope between which a high potential difierence occurs during the production of X-rays, metallic leading-in conductors sealed to said envelope and connected to said electrodes for transmitting energy thereto having a spacing therebetween exteriorly of said tube below that normally electrically necessary to prevent spark-over at the applied voltage, and means for energizing said tube for a period of time less than that required to cause ionization of the air between the closely spaced metallic conductors to prevent the occurrence of sparkover therebetween regardless of the high instantaneous potential diiTerence existing between said conductors.
  • An X-ray tube comprising an envelope, electrodes in said envelope between which a high potential difference occurs during the production of X-rays, metallic leading-in conductors connected to said electrodes for transmitting energy thereto and spaced apart exteriorly of said envelope a, distance considerably less than the normal electrical requirements necessary to prevent spark-over therebetween at the applied voltage,

Landscapes

  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
  • X-Ray Techniques (AREA)
US451902A 1942-07-22 1942-07-22 Electron emission device Expired - Lifetime US2349468A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE483447D BE483447A (enrdf_load_stackoverflow) 1942-07-22
US451902A US2349468A (en) 1942-07-22 1942-07-22 Electron emission device
GB20797/47A GB638642A (en) 1942-07-22 1947-07-31 Improvements in or relating to x-ray tubes and energising systems therefor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US451902A US2349468A (en) 1942-07-22 1942-07-22 Electron emission device

Publications (1)

Publication Number Publication Date
US2349468A true US2349468A (en) 1944-05-23

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US451902A Expired - Lifetime US2349468A (en) 1942-07-22 1942-07-22 Electron emission device

Country Status (3)

Country Link
US (1) US2349468A (enrdf_load_stackoverflow)
BE (1) BE483447A (enrdf_load_stackoverflow)
GB (1) GB638642A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2177793A1 (enrdf_load_stackoverflow) * 1972-03-24 1973-11-09 Energy Sciences Inc

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2177793A1 (enrdf_load_stackoverflow) * 1972-03-24 1973-11-09 Energy Sciences Inc

Also Published As

Publication number Publication date
BE483447A (enrdf_load_stackoverflow)
GB638642A (en) 1950-06-14

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