US3783333A - X-ray tube with improved control electrode arrangement - Google Patents

X-ray tube with improved control electrode arrangement Download PDF

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Publication number
US3783333A
US3783333A US00229136A US3783333DA US3783333A US 3783333 A US3783333 A US 3783333A US 00229136 A US00229136 A US 00229136A US 3783333D A US3783333D A US 3783333DA US 3783333 A US3783333 A US 3783333A
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United States
Prior art keywords
anode
electrons
filament
cathode
auxiliary electrode
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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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US00229136A
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English (en)
Inventor
Z Atlee
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Philips Nuclear Medicine Inc
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Picker Corp
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Publication date
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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
    • H01J35/066—Details of electron optical components, e.g. cathode cups
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/06—Cathode assembly
    • H01J2235/068—Multi-cathode assembly

Definitions

  • Thoriated tungsten filaments have many desirable features and many efforts have been made to utilize them in x-ray tubes and other electron emissive devices. In come circumstances the thoriated tungsten filaments are adaptable, but in others, such as x-ray tubes, they are generally undesirable under control arrangements which have heretofore been available. Since thoriated tungsten filaments are operated at a lower temperature than pure tungsten filaments the cooling rate of a thoriated tungsten filament is slower than that of a tungsten filament and thus control of emission level by a decrease in filament current is frequently too slow in the case of a thoriated tungsten filament to permit its use. The use of a grid for control is undesirable for the reasons outlined above.
  • an x-ray tube or similar electron emissive device having an electron generating cathode filament, a focusing cup electrode and an anode is provided with an auxiliary electrode that is positioned behind the cathode filament with respect to the anode.
  • auxiliary electrode that is, positive with respect to the filament
  • electrons can be drawn from the filament to the electrode thus reducing the number of electrons which flow from the cathode to the anode.
  • reducing the potential will permit more electrons to flow to the anode.
  • the auxiliary electrode thus provides a means for controlling the level of electron flow to the anode.
  • the auxiliary electrode arrangement can also be utilized to control operation of x-ray tubes having dual filaments which are provided in order to produce focal spots of different sizes on the anode.
  • X-ray tubes have been provided heretofore with cathodes having two filaments, one being longer than the other and arranged so as to form on the anode, depending upon the filament which is operated, a large or a small focal spot.
  • the larger focal spot is utilized, for example, for spot film radiography whereas the small focal spot is utilized for fluoroscopic examination. In some instances it is desirable to be able to switch rapidly from one filament to another.
  • such rapid switching is enabled by constructing a cathode with two filaments mounted in electrically insulated focusing cup eletrodes. This enables both filaments to be operated continuously and the electron flow from the respective filaments cut off by selectively applying a negative bias to the respective focusing electrode, thereby cutting off the flow by reason of the space charge efiect accross the mouth of the focusing cup recess.
  • Each cathode portion may also be provided with an auxiliary control electrode behind the filament such as discussed above.
  • FIG. 1 is a side elevation of an x-ray tube constructed in accordance with the invention
  • FIG. 2 is a fragmentary view of the anode target looking in the direction of the arrows 2-2 of FIG. 1;
  • FIG. 3 is an enlarged end view of the cathode head taken generally along the lines 3-3 of FIG. 1;
  • FIG. 4 is a sectional view taken substantially along the lines 44 of FIG. 3;
  • FIG. 5 is a view similar to FIG. 3 of further embodiment of the invention.
  • FIG. 6 is a s ectional view lines 5 6 of FIG. 5.
  • the present invention is illustrated in connection with an x-ray generator comprising an envelope 10 of glass or other suitable material, having a cathode unit 12 suitably mounted in one of the envelope and a rotary anode unit 14 suitably mounted in the other end of the envelope.
  • the anode unit 14 comprises a rotating target element 16 preferably formed of a metal of tungsten or other refractory metal.
  • the anode 16 is provided with a frusto-conical target surface 18 defining a target area for the reception of electrons upon superimposed focal spots 22, 24 respectively.
  • the cathode 12 therein illustrated comprises a metal body 30 which is supported within a tubular nonconductive sleeve 32 supported from the envelope 10.
  • the body 30 is formed within an indented face adjacent the end facing the anode unit 14 defined by a pair of planar face portions 34-36.
  • the face portion 34 has an elongated focusing cup recess 38 formed therein and the face portion 36 has a shorter focusing cup recess 40 formed therein.
  • Mounted within the recess 38 is a filament 42 for generating electrons which are focused upon the anode target portion 18 so as to form the focal spot 24 thereon.
  • the focusing cup recesses 38-44 are each formed with a relatively narrow bottom slot or gap 46, 48 respectively, extending through the back face of the body 30 which in this instance is formed in a cup shape with a hallowed out back portion 50.
  • Leads for connecting the filaments to a source of electrical energy are provided including a lead 52 connected to one end of the filament 42 and a lead 54 connected to the corresponding end of the filament 44.
  • the leads extend through circular openings formed at the opposite ends of the slots 46, 48 from the cups to the back face of the body 30.
  • the opposite ends of the filament 42,44 are interconnected to a common lead 56.
  • auxiliary electrode 60 comprising a body made of conductive material such as metal, the body being mounted in closely spaced but electrically insulated relation with respect to the cathode body 30.
  • the body 60 is cylindrical and is secured to the body 30 by suitable means such as a screw 62 threaded into the body 30 and extending through an axial opening 64 in the body 60, but insulated therefrom by washers 66.
  • the screw 62 provides a means for connecting the body 30 to a source of electrical potential through a lead 68 which is secured to the screw by suitable means.
  • Means are provided for connecting the electrode 60 to a source of electrical potential comprising a lead 70 secured in position by a setscrew 72. It is to be understood that all such leads extend outwardly from the envelope through a suitable conventional arrangement for connection to sources of electrical energy and potential such as shown in U. S. Pat. No. 2,862,107 of H. R. Cummings granted Nov. 25, 1958.
  • the flow of electrons from an energized filament to the anode can be controlled by changing a positive voltage (with respect to the energized filament) applied to the auxiliary electrode 60.
  • the application of such a potential to the electrode will cause some of the electrons which are being boiled off the filament to be attracted to the auxiliary electrode thus diminishing the fiow of the electrons to the anode.
  • the potential applied to the electrode will not affect the focal spot size or electron distribution thereover.
  • This invention has particular advantage in the operation of x-ray tubes in which the filaments are thoriated tungsten.
  • Such filaments are operated at such a low temperature that the usual control by decrease of the current applied to the filament can not be utilized since the cooling rate of the filament is too slow.
  • Control by means of the application of potential to the auxiliary electrode 60 on the other hand is instantaneous and thus the emission level of the filament to the anode can be maintained substantially uniform.
  • the filaments 42-44 can be operated independently of each other only by selectively applying power to the filaments.
  • rapid switching from one focal spot to another is difficult, particularly with thoriated tungsten filaments because of the slow response time of the filaments.
  • control of emission by applying a bias to the cup 30 is difficult in the configuration of FIGS. 3 and 4 inasmuch as the application of a bias sufficient to cut off emission from the large filament 42 will place stress across the small gap 48 in the smaller cup 40.
  • the cathode structure therein shown comprises a cup comprising two separate semi-cylindrical sections 80, 82 suitably supported from the sleeve 32 and insulated from one another by a diametrically extending insulator 84.
  • the cup section has an elongated focusing cup 86 formed therein having a focusing slot 88 in the bottom thereof with a pair of openings 90, 92 for the passage of lead wires 94, 96 connected to the opposite ends of a filament 98.
  • the section 82 is provided with a shorter focusing cup 100 in the surface thereof facing the anode 14 in the bottom of which cup is provided a focusing slot 102 and suitable openings for passage of leads 104, 106 connected to the opposite ends of a filament 108.
  • the rear surfaces that is the surfaces of the cup sections 80, 82 remote from the anode 14, are c0- planar.
  • auxiliary electrodes 110, 112 mounted closely adjacent to such surfaces, but spaced therefrom, are a pair of auxiliary electrodes 110, 112, each of which is semi-circular in configuration and which are separated by a diametric insulator 114.
  • the electrodes 110, 112 are secured to the corresponding electrodes 80, 82, respectively, by means of bolts 116, 118, respectively, which are in electrical contact with the respective cup section but are insu' lated from the respective electrode by means of insulators 120.
  • An electrical lead 122 is connected to the bolt 1 16 to provide means for connecting the cup section 80 to a source of electrical potential and lead 124 is connected to the bolt 118 to provide means for connecting the cup section 82 to a source of electrical potential.
  • the various filament leads 94, 96, 104, 106 extend outwardly through the electrodes 110, 112, each filament lead being encased within a tubular insulator 126, which in turn is surrounded by a metal sleeve 128.
  • Means are provided for connecting the electrodes 1 10, 112 to source of electrical potential, the plate being connected to a lead 130, extending into the plate and held in place therein by a setscrew 132.
  • the plate 112 is connected to a lead 134, held in place by a setscrew 136.
  • the filaments 98, 108 can be simultaneously energized. If it is desired to secure a focal spot from the emission from the filament 98 sufficient bias is applied to the cup section 82 to suppress the emission from the filament of 108. If it is then desired to secure emission from the focal spot generated by emission from the smaller filament 108, the bias can be instantaneously switched from the cup section 82 to cup section 80 thus suppressing emission from the filament 98 while permitting emission from the filament 108 to pass to the anode.
  • the auxiliary electrodes 110, 112 function to control the amount of available electrons from each of the filaments in a manner similar to the control electrode 60.
  • a suitable power supply circuit will be energized to apply a positive potential to the auxiliary electrode 110. This will cause electrons to be drawn from the filament 98 through the openings 90 to the plate 110, thereby maintaining the electron flow to the anode at the desired level.
  • the auxiliary electrode 112 can be utilized to control the flow of electrons to the anode and cut off excessive flow when the desired level is reached. That is, when a desired level of current flow through the tube is sensed in the suitable control circuit, a voltage will be applied to the auxiliary electrode 112 to attract electrons from the filament 108 through the openings for the lead wires 104, 106.
  • An electron emissive device comprising:
  • a cathode means including an electron emitter for generating electrons
  • an auxiliary electrode positioned entirely behind said emitter of said cathode means with respect to said anode
  • cathode means comprising a metal body having an electron focusing cup recess therein,
  • auxiliary electrode being positioned adjacent to but spaced from said rear surface
  • said body having an opening extending from said rear surface into said recess
  • An x-ray tube comprising:
  • a cathode means including an electron emitter and a focusing electrode insulated from said emitter for generating electrons
  • an auxiliary electrode positioned behind said emitter with respect to said anode and insulated from said focusing electrode;
  • An x-ray tube in which the improvement comprises:
  • a cathode means including a pair of filaments for emitting electrons
  • a focusing cup structure for said filaments comprising a pair of metal bodies each having a focusing cup recess formed therein, said bodies being electrically insulated from each other;
  • said filaments being mounted one in each of said recesses and electrically insulated from said bodies;
  • At least one auxiliary electrode insulated from said focusing cup structure and positioned behind said filaments relative to said anode;
  • each of said bodies to a source of negative electrical potential relative to the filament potential independently of the other body whereby a cutoff bias can be applied selectively to said bodies to restrict flow of electrons from a selected on of said filaments to said anode.
  • auxiliary electrode and means for connecting said auxiliary electrode to a source of positive potential with respect to the filament in the adjacent body whereby upon application of said positive potential electrons will be drawn from such filament to said auxiliary electrode.
  • a focusing electrode comprising a conductive metal body having at least one focusing cup recess formed therein the surface facing said anode and at least one opening extending from said recess to the opposite surface of said body;
  • a cathode filament mounted in said recess for generating electrons for impingement upon said anode having a lead extending through said opening;
  • an auxiliary electrode of an electrically conductive material positioned behind said filament relative to said anode and adjacent to said opposite surface but electrically insulated from said focusing electrode;
  • auxiliary electrode to a source of electrode potential positive with respect to said filament whereby at least some of the electrons generated at said filament will be drawn to said electrode thereby lessening the flow of electrons from said cathode to said anode.

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  • X-Ray Techniques (AREA)
US00229136A 1972-02-24 1972-02-24 X-ray tube with improved control electrode arrangement Expired - Lifetime US3783333A (en)

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US22913672A 1972-02-24 1972-02-24

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US3783333A true US3783333A (en) 1974-01-01

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US (1) US3783333A (de)
JP (1) JPS48100087A (de)
CA (1) CA959108A (de)
DE (1) DE2231970A1 (de)
FR (1) FR2172949B1 (de)
NL (1) NL7209611A (de)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4104526A (en) * 1973-04-24 1978-08-01 Albert Richard D Grid-cathode controlled X-ray tube
US4685118A (en) * 1983-11-10 1987-08-04 Picker International, Inc. X-ray tube electron beam switching and biasing method and apparatus
US4689809A (en) * 1982-11-23 1987-08-25 Elscint, Inc. X-ray tube having an adjustable focal spot
US4764947A (en) * 1985-12-04 1988-08-16 The Machlett Laboratories, Incorporated Cathode focusing arrangement
US5007074A (en) * 1989-07-25 1991-04-09 Picker International, Inc. X-ray tube anode focusing by low voltage bias
US5844963A (en) * 1997-08-28 1998-12-01 Varian Associates, Inc. Electron beam superimposition method and apparatus
US6104781A (en) * 1992-09-16 2000-08-15 U.S. Philips Corporation X-ray generator for powering an X-ray tube comprising at least two electron sources
US6438207B1 (en) 1999-09-14 2002-08-20 Varian Medical Systems, Inc. X-ray tube having improved focal spot control
US20050175152A1 (en) * 2004-02-09 2005-08-11 Varian Medical Systems Technologies, Inc. Cathode head with focal spot control
US9524845B2 (en) 2012-01-18 2016-12-20 Varian Medical Systems, Inc. X-ray tube cathode with magnetic electron beam steering
JP2019036460A (ja) * 2017-08-14 2019-03-07 キヤノン電子管デバイス株式会社 Ｘ線管
CN109478486A (zh) * 2016-06-20 2019-03-15 佳能电子管器件株式会社 X射线管

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3008304A1 (de) * 1980-03-04 1981-09-17 Siemens AG, 1000 Berlin und 8000 München Roentgenroehre mit zwei kathodenwendeln
US5511105A (en) * 1993-07-12 1996-04-23 Siemens Aktiengesellschaft X-ray tube with multiple differently sized focal spots and method for operating same
DE19504305A1 (de) * 1995-02-09 1996-08-14 Siemens Ag Röntgenröhre

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3018398A (en) * 1958-10-27 1962-01-23 Dunlee Corp X-ray generator
US3178578A (en) * 1961-03-03 1965-04-13 High Voltage Engineering Corp Electron pulser for an x-ray tube to produce a pulsed beam of x-rays
US3250916A (en) * 1963-06-14 1966-05-10 Machlett Lab Inc Stereo x-ray device
US3549931A (en) * 1968-12-04 1970-12-22 Torr Lab Inc X-ray transmissive window assembly
US3665236A (en) * 1970-12-09 1972-05-23 Atomic Energy Commission Electrode structure for controlling electron flow with high transmission efficiency

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Publication number Priority date Publication date Assignee Title
GB232159A (en) * 1924-04-11 1925-10-08 Huth Erich F Gmbh Improvements in and relating to thermionic tubes
US3433955A (en) * 1966-09-26 1969-03-18 Picker Corp X-ray generator with emission control arrangement within the focusing cup
US3660712A (en) * 1970-12-09 1972-05-02 Atomic Energy Commission Electrode structure for controlling electron flow with high transmission efficiency

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3018398A (en) * 1958-10-27 1962-01-23 Dunlee Corp X-ray generator
US3178578A (en) * 1961-03-03 1965-04-13 High Voltage Engineering Corp Electron pulser for an x-ray tube to produce a pulsed beam of x-rays
US3250916A (en) * 1963-06-14 1966-05-10 Machlett Lab Inc Stereo x-ray device
US3549931A (en) * 1968-12-04 1970-12-22 Torr Lab Inc X-ray transmissive window assembly
US3665236A (en) * 1970-12-09 1972-05-23 Atomic Energy Commission Electrode structure for controlling electron flow with high transmission efficiency

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4104526A (en) * 1973-04-24 1978-08-01 Albert Richard D Grid-cathode controlled X-ray tube
US4689809A (en) * 1982-11-23 1987-08-25 Elscint, Inc. X-ray tube having an adjustable focal spot
US4685118A (en) * 1983-11-10 1987-08-04 Picker International, Inc. X-ray tube electron beam switching and biasing method and apparatus
US4764947A (en) * 1985-12-04 1988-08-16 The Machlett Laboratories, Incorporated Cathode focusing arrangement
US5007074A (en) * 1989-07-25 1991-04-09 Picker International, Inc. X-ray tube anode focusing by low voltage bias
US6104781A (en) * 1992-09-16 2000-08-15 U.S. Philips Corporation X-ray generator for powering an X-ray tube comprising at least two electron sources
US5844963A (en) * 1997-08-28 1998-12-01 Varian Associates, Inc. Electron beam superimposition method and apparatus
US6438207B1 (en) 1999-09-14 2002-08-20 Varian Medical Systems, Inc. X-ray tube having improved focal spot control
US20050175152A1 (en) * 2004-02-09 2005-08-11 Varian Medical Systems Technologies, Inc. Cathode head with focal spot control
US7257194B2 (en) 2004-02-09 2007-08-14 Varian Medical Systems Technologies, Inc. Cathode head with focal spot control
US9524845B2 (en) 2012-01-18 2016-12-20 Varian Medical Systems, Inc. X-ray tube cathode with magnetic electron beam steering
CN109478486A (zh) * 2016-06-20 2019-03-15 佳能电子管器件株式会社 X射线管
EP3474306A4 (de) * 2016-06-20 2020-02-26 Canon Electron Tubes & Devices Co., Ltd. Röntgenröhre
US10872741B2 (en) * 2016-06-20 2020-12-22 Canon Electron Tubes & Devices Co., Ltd. X-ray tube
CN109478486B (zh) * 2016-06-20 2021-01-01 佳能电子管器件株式会社 X射线管
JP2019036460A (ja) * 2017-08-14 2019-03-07 キヤノン電子管デバイス株式会社 Ｘ線管
CN111033673A (zh) * 2017-08-14 2020-04-17 佳能电子管器件株式会社 X射线管
EP3651180A4 (de) * 2017-08-14 2021-03-10 Canon Electron Tubes & Devices Co., Ltd. Röntgenröhre
US11217420B2 (en) 2017-08-14 2022-01-04 Canon Electron Tubes & Devices Co., Ltd. X-ray tube

Also Published As

Publication number Publication date
JPS48100087A (de) 1973-12-18
DE2231970A1 (de) 1973-08-30
FR2172949A1 (de) 1973-10-05
FR2172949B1 (de) 1976-05-21
NL7209611A (de) 1973-08-28
CA959108A (en) 1974-12-10

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