US2167275A - High voltage x-ray tube - Google Patents

High voltage x-ray tube Download PDF

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Publication number
US2167275A
US2167275A US43816A US4381635A US2167275A US 2167275 A US2167275 A US 2167275A US 43816 A US43816 A US 43816A US 4381635 A US4381635 A US 4381635A US 2167275 A US2167275 A US 2167275A
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Prior art keywords
tube
cathode
anode
envelope
cup
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Expired - Lifetime
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US43816A
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English (en)
Inventor
Malvern J Gross
Zed J Atlee
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General Electric X Ray Corp
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General Electric X Ray Corp
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Publication date
Priority to BE417964D priority Critical patent/BE417964A/xx
Application filed by General Electric X Ray Corp filed Critical General Electric X Ray Corp
Priority to US43816A priority patent/US2167275A/en
Priority to FR811639D priority patent/FR811639A/fr
Application granted granted Critical
Publication of US2167275A publication Critical patent/US2167275A/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/68—Circuit arrangements for Lilienfield tubes; Circuit arrangements for gas-filled X-ray tubes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details

Definitions

  • the present invention relates in general to electronics and has more particular reference to vacuum tubes used in generating X-rays and which are operated at high voltages, namely,
  • Tubes for operation above three hundred kilovolts have been designed to operate only while connected to vacuum pumps as shown in Letters Patent of the United States, Numbers 1,936,424 and 1,967,689 issued to Coolidge.
  • Coolidge tubes having a capacity of three hundred kilovolt or more are relatively large structures.
  • the Coolidge tubes have an over-all length on the order of fourteen feet. Two, or more, sections,
  • an exhaust system is, of necessity, connected to the tubulation of the tube.
  • the vacuum pumps, forming a part of the vacuum system must be started about a half hour before the tube is placed in operation, and must be operated continuously While energy is applied to the tube.
  • a carefully applied base and a vacuum exhaust system make it necessary for one of the large tubes of the Coolidge type to be mounted in a xed location.
  • Such tubes actually require, for best results, a separate building for the tube and its energizing equipment.
  • the successful operation of a tube at high voltages depends primarily upon an ability to govern the behavior of all electrons that are emitted purposely from a tube lament and to eliminate emission of electrons from any other source than from such filament.
  • the dielectric strength of the glass of the tube must be suiiciently high to withstand rupture under the strain so produced.
  • the dielectric strength of the glass wall of a tube can. be raised sufficiently by increasing the thickness of the walls.
  • the thickness of glass that is made necessary for this purpose is within the practicable limits of glass work.
  • the control of electrons in an X-ray tube may take place in three different spheres, viz:
  • failure of a tube also may occur from a bombardment of the seals in the glass which difficulty we find may be cured by proper shielding methods.
  • Electrons, and to some extent other atomic and sub-atomic particles, may be emitted under the conditions which are named herein from the following sources:
  • a tube of the character mentioned and so constructed that electron. bombardment of the glass portions of the tube is'y substantially eliminated; a tube of the character mentioned having an anode to cathode spacement and a rounded design for such anode and cathode so that cold cathode eiiects are substantially eliminated; a tube of the character mentioned having a hooded anode structure to cause absorption of secondary electronic emission from the focal spot of the tube without undue heating; a tube of the character mentioned having a cathode structure formed and arranged to control and maintain the emitted electrons in substantially parallel paths; a tube of the character mentioned having a cathode structure permitting the addition thereto of metering devices and auxiliary Voltage sources for the measurement of gas pressures during the exhaust and the operation of the tube; a tube of the character described having a cathode structure so arranged that an auxiliary low voltage electron discharge may be used for the purpose of electrically cleaning up any
  • Figure 1 is a longitudinal elevation of a tube embodying the invention, said tube having parts shown in section and being illustrated with connections to sources of power, measuring devices, and the like, all of which are diagrammatically shown ;
  • Figure 2 is an enlarged fragmentary cross-section of the central portion of the tube shown in Figure i, the View being at right angles to Figure 1;
  • Figure 3 is a fragmentary section taken along the line 3 3 of Figure 2 looking in the direction of the arrows;
  • Figure 4 is a section taken on the line 1 -4 of Figure 3 and looking in the direction of the arrows:
  • Figure 5 is a section taken along the line 5 5 of Figure 3 and looking in the direction of the arrows.
  • the tube illustrated in Figure l comprises an envelope lil Vof glass or other suitable insulating of the filament was set approximately .016 inch below the focusing edge 34.
  • the anode arm il is a reentrant tube iii sealed to the arm at 4l to form an anode support.
  • a centering ring 42 has attached thereto at t3, with silver solder or in any fashion desired, a tapered metal sleeve 44 forming the metal side of a glass to metal seal 45.
  • the centering ring i2 has within it two apertures 46 through which the ends 43 and 49 of a nickel tube which forms a part of the cooling system pass.
  • the tube ends are silver soldered in position in the centering ring 42 as shown.
  • the tube whose ends are shown at 48 and 49 is wound in the form of a flat helix, as shown in Figure 5, which helix is soldered to the rear face of the main anode casting, as shown at 5i).
  • the main anode casting comprises essentially7 a cylinder 52 having an inner transverse wall 53 near one end.
  • the inner wall 53 has cast in its face a tungsten button 54 which serves as a target to be bombarded by electrons from the cathode for the production of X-rays.
  • That portion of the cylinder 52 which is nearest the tungsten button Ed has a heavier wall than the remainder of the cylinder. This is due to the fact that it is necessary to absorb more secondary electron emission from the anode at this point than at a point further from the anode, and for that reason, more heat absorption capacity is essential.
  • a window of reduced section is cut into the thickened wall of cylinder 52 as shown at
  • the thickness of the wall of the cylinder closest to the button 54 is on the order of T35 inch, while the window thickness is approximately .086 inch.
  • the mean length of the cylinder should be at least four times and maybe as long as ten times the diameter of the opening. Such proportions insure that any stray electrons from the anode are prevented from reaching the envelope of the tube.
  • the entire anode is cast in a vacuum from deoXidized copper in a manner well known in the art, after which the tungsten button is cleaned, the casting machined, and the window 55 milled to thickness size.
  • the cooling coil previously described is soldered into position as shown, and the centering ring at the s( .ie time soldered to the cooling coil extensions i8 and 4Q. Glass then is placed on the sleeve ffili to complete the metal to glass seal @5.
  • the next step is to seal the structure just described to the glass anode support 4l] at a point approximately indicated by the numeral Before the latter is flared as a preliminary to making the seal at 4
  • a guard ring 61 designed to present rounded surfaces to the cathode and to the envelope for purposes to be later described, is attached to the near end of the cylinder 52 in any desired fashion, as for instance by means of the screws B8.
  • the design of the anode just described has for its primary purpose the absorption of any stray electrons from the target or from the electron stream. As an incident to such absorption, a large amount of heating takes place and, unless the anode is designed properly, its temperature is increased to such a point that it will cause a deposit of copper on the bulb or the liberation of suiiicient gas from the target body to cause destruction of the tubing.
  • the envelope IB has an anode arm I I and a cathode arm Arms II and I2 are cylindrical in crosssection and are each connected to an enlarged portion I3 which is also cylindrical in crosssection. Attention is called to the fact that the location of the enlarged portion I3 is approximately central with respect to the anode-cathode space and that the point of emission of the radiation is located within the anode arm for a purpose to be described later.
  • Arms II and I2 are in axial alignment one with another and with the axis of cylindrical portion I3.
  • the walls of the envelope I0 are relatively thick, being approximately three-eighths of an inch in thickness for the particular tube illustrated which tube is designed to operate at approximately five hundred kilovolts peak.
  • constricted anode and cathode arms lend themselves to a closing up of such arm to prevent electrons from getting back into the arms.
  • Such constricted anode arm permits the employment of a core in close proximity to the point of emission of the X-rays.
  • the cathode arm I2 has sealed within it a reentrant cathode support I 4, which is made of glass and is maintained in position at its outer end by means of an end seal I5.
  • the cathode support I4 has a section of reduced diameter indica-ted at Iii and which is shown in section in Figure 2.
  • a three-wire pinch seal Il is attached to the reduced section Iii in any desired fashion as, for instance, by means of a ring seal I8.
  • a centering cylinder I9 has silver soldered to it at one end a tapered nickel steel cone 2li to form the metal portion of a glass to metal seal shown at 2l.
  • the glass portion of this glass to Ymet-al seal is attached to the inner end of the reduced portion I6 of the cathode support I4 of approximately the point 22.
  • the cathode proper of the X-ray tube is indicated by the filament 23 which in a five hundred kilovolts peak.
  • tube of the present design may consist of .0085 inch undoped tungsten wire wound in the form of a pyramidal spiral having a maximum diameter of .281 inch.
  • the terminals of the filament 23 are secured to molybdenum filament leads 24 and 25 in any desired fashion as, for instance, by binding them with nickel wire and then arc welding.
  • the filament 23 so mounted is supported in position in cathode cup 26 by meansV of support clamps 2'! between opposing faces of which lilament leads are supported through the medium of insulating blocks 28. Connections between the filament leads 2li and 25 are made to outside pinch seal wires 29 and 3l! in any desired fashion as, for instance, by welding.
  • a support sleeve 3! serves as an electrostatic shield to the various joints, and the like, around the cathode.
  • Sleeve 3l is secured to the cathode cup 26 by means of screws shown at 32 and to the centering ring I9 by means of screws at 32a.
  • the filament 23 is first mounted in the cathode cup 26 and the cathode support assembled complete with the centering ring I9.
  • the support tube il is then slid back on the cathode support Iii away from the pinch seal Il as far as it will go.
  • the welds joining the lilament leads 24 and 25 to the pinch seal leads 29 and 3l! are then made, after which the support sleeve 3
  • Center lead 33 of the pinch seal is connected to the metal portions of the cathode structure, as shown in Figure 3, by means of the screw fi.
  • the lead 33 is brought out independently of the other two leads for a purpose which will later be described.
  • the cathode design be such that the paths of the electrons be substantially parallel with one another. This is necessary not only in order to obtain distribution of energy on the focal spot of the tube, but also to avoid the impingement of the electrons upon other portions of the anode structure or even upon the glass envelope itself to cause undue heating and eventually destruction of the tube.
  • the other error .in the distribution of energy on the focal spot is that due to failure tokeep the paths of the electrons parallel one with another after leaving the environment of the cathode.
  • this factor may be and is entirely disregarded.
  • the present invention does away with the necessity for magnetic focusing means such as are disclosed in Coolidge, supra.
  • the filament diameter should not be more than ..100 inch smaller than the size of the focusing opening in the cathode structure.
  • the diameter of the filament been given at .28.1. inch, while the aperture in the cup is .312 inch, or a difference of .approxi ately .030 inch. This difference, it has been found, prevides adequate control of the electron paths and at the same time permits of sufficient clearance between the filament and the cup.
  • the depth to which the filament is set within the cup is the depth to which the filament is set within the cup. It has been found that the cup must be relatively deep, not less than .350 inch in the present type of tube.
  • a cup having a focusing opening whose depth is .46S inch is used.
  • lIhe relation between the filament setting and the focusing opening is usually controlled by the position of the ilament with respect to the focusing edge indicated by the numeral 3d in the drawing. It has been found that for best control the filament position should be such that the distance of its central portion above or below a plane passing through the bottom of the focusing edge 554i is within twenty per cent of the filament coil diameter.
  • the top iii Vcathode cup causing the When tubes operate on a pumping system, these values are approximately doubled.
  • the terminals 29 and 3d are connected to a source of filament current 53 of the proper voltage. Between one of these terminals and the terminal 33 is connected a source of power 60, capable of delivering one hundred ten volts direct current. This is connected so that the positive pole is connected to conductor 33 and the negative pole to the filament wire Sii.
  • a milliammeter 64 is interposed in the line 33 for the purpose of measuring the current passed from the lament to the cathode cup.
  • Attached to the anode is a lead El which extends to the filament current conductor 29 and in which a micro-ammeter 62 is inserted.
  • the lead 6i is connected to a battery G5 or to another source of direct current so that the anode is at a negative potential of twenty-two volts with respect to the lament.
  • the current will now pass from the filament to the milliammeter to defleet.
  • this value should be set so that the milliammeter reads l, under the conditions as they have been standardized.
  • the microammeter @2 will not register, but if there are any gas molecules present, they will be split up and the positive ions driven from the lament and cathode cup to the anode Where they will give up their charge, the accumulated values of which will be registered on the micro-ammeter 62.
  • each micro-ampere deflection of the meter 62 represents a gas pressure of .02 micron, when the gas within the tube is of approximately the same composition as air. Where other gases are present, suitable corrections must be made.
  • the structure now being discussed provides a convenient and accurate method of measuring pressures and is used as a check on the condition of a tube after it has been installed.
  • the present structure permits of the use of unrectied alternating current at voltages greatly in excess of that permissible with the old type high voltage tubes.
  • While the most desirable embodiment of the present invention is an X-ray tube, it is to be understood that some or all or the structures herein described can be easily applied to other high voltage vacuum devices, such as cathode ray tubes, rectiers, and the like, with the same satisfactory results that have been obtained in X-ray tubes. It isthe intention to cover each individual structure as well as all operable combinations of them as far as the present state of the art permits, as it is the belief that the use o the invention in such structures is within the scope of the present invention.
  • An X-ray tube comprising an envelope, an anode having a target, a cathode, and a tubular shield surrounding said target and extending in the direction of said cathode, said cathode comprising a focusing cup having a hemispherical depression and a filament disposed centrally in said hemispherical depression, the conguration of the lament being such that the wall of the hemispherical depression causes the electrons emitted from said lament to fiow in substantially parallel lines for a substantial portion o1" the length of the electron beam and to diverge within said anode shield to form a larger focal spot upon the target.
  • An X-ray tube comprising an envelope, an anode having a target, a cathode, a shield surrounding said target, said anode and said shield being of highly conductive material, the shield being cylindrical and of a length at least four times its diameter, said cathode having a focusing cup hemispherical in configuration and an opening into the bottom of said cup, and a pyramidally coiled filament in the inner most section of said cup and having its lower edge in substantial alignment with the plane passing through the outer edge of the opening therein.
  • An X-ray tube comprising an enlarged cylindrical midsection, an anode arm, and a cathode arm, a cathode comprising a focusing cup, the outer periphery of said cup being rounded,
  • An X-ray tube comprising an envelope having an enlarged central section and two arms, a cathode and a focusing cup with a hemispherical concavity and having a rounded outer periphery in the central section of said tube and extending from one of said arms, an anode in the other of said arms and comprising a target, and a cylindrical shield projecting from said anode and surrounding said target and extending into the central section of said tube.
  • An X-ray tube comprising an envelope having a central cylindrical section and two cylindrical arms, an anode structure sealed to the envelope in one of said arms, said anode structure comprising a target, a shield about said target and extending into the central cylindrical section of said envelope, a second cylindrical shield extending rearwardly of the target, and a transverse member in said second cylindrical shield, the second cylindrical shield and the transverse member in said second cylindrical shield preventing bombardment of the seal between said envelope and said anode structure, a cathode structure sealed to said envelope in the other of said arms, said cathode structure comprising a lament, a focusing cup, conductors to said filament, a cylindrical shield extending from said cup, and a transverse member in said cylindrical shield whereby the seal between said envelope and said cathode structure is protected from electron bombardment.
  • a cathode In an X-ray tube, a cathode, an envelope having a re-entrant portion, and an anode structure comprising a sleeve sealed at one end to said re-entrant portion, a cap member engaging the other end of said sleeve, a cylinder having a transverse partition therein, an open end of said cylinder facing the cathode, a target secured to one face of said partition, a second sleeve secured to said cap member and said cylinder, said second sleeve extending over the first sleeve and over said re-entrant portion.
  • a cathode In an X-ray tube, a cathode, an envelope having a re-entrant portion, and an anode structure comprising a sleeve sealed at one end to said re-entrant portion, a cap member engaging the other end of said sleeve, a cylinder having a transverse partition therein, an open end of said cylinder facing the cathode, a target secured to one face of said partition, a second sleeve secured to said cap member and said cylinder, said second sleeve extending over the first sleeve and. over said re-entrant portion, a coiled conduit supported by said cap member and secured to said partition in heat conducting relation thereto, and means for circulating a cooling medium through said conduit for dissipating the heat generated at the target.
  • an X-ray tube an envelope having reduced cylindrical end portions and an enlarged center portion, a cathode extending from one end portion into said center portion, an anode, said anode comprising a cylinder extending from the opposite end portion of the envelope into the center portion, said cylinder having a transverse partition disposed Within said last mentioned end portion of the envelope and the open end of said cylinder facing toward said cathode, a target secured to one face of said partition, means for conducting a cooling medium across the other face of said partition for dissipating the heat generated at the target.
  • an envelope having reduced cylindrical end portions and an enlarged central portion, a cathode extending from one end portion into said central portion, an anode, said anode comprising a cylinder extending from the opposite end portion of the envelope into the central portion, said cylinder having a transverse partition disposed within said last mentioned end portion and a thickened wall portion adjacent and forwardly' of said partition, an open end of said cylinder facing said cathode, a target secured to one face of said partition, said thickened portion of the cylinder absorbing a portion of the heat generated at the target, and means for conducting a cooling medium across the other face of said partition for further dissipating the heat generated at the target.
  • an envelope having an enlarged central section, arms extending oppositely from said central section and re-entrant portions in said arms, a sleeve sealed to one of said re-entrant portions, a cap member supported by said sleeve, a focusing cup having a hernispherical concavity and located Within the central section of the envelope, a filament in said focusing cup, a second sleeve supporting said cup and extending within one of the arms of the envelope and over said cap member, said first sleeve and said re-entrant portion, said second sleeve being supported on said re-entrant portion by said cap member and said first sleeve.
  • An X-ray tube for operation at voltages of the order of four hundred kilovolts comprising a cathode and an anode providing a long electron path, said cathode comprising a focusing cup having a central opening extending axially from the bottom of the cup, a coiled filament within said cup and extending into said axially directed opening, the depth of the cup being not less than .350 inch and the radial clearance between the filament and the wall of the axially directed opening being not more than one-tenth of an inch, the distance of the central portion of the coiled lament above or below the plane passing through the bottom of the cup at the edge of said axially directed opening being not greater than twenty per cent of the diameter of the coiled filament, the internal wall of the cup which forms the focusing edge for the filament being substantially hemispherical in configuration.
  • An X-ray tube comprising a glass envelope having a central cylindrical section and two cylindrical arms, an anode structure sealed to the envelope in one of said arms, said other arm having a re-entrant portion, a cathode structure having a glass-to-metal seal with said re-entrant portion and comprising a focusing cup, a lament in the focusing cup, and a metal sleeve extending from the focusing cup over the glass-tometal seal and over the re-entrant portion of the envelope well beyond said seal.
  • An Xeray tube comprising a glass envelope having a re-entrant portion, an anode structure .having a glass-to-metal seal with said re-entrant portion and comprising a target and a metal sleeve extending from said target over said seal and over the re-entrant portion of said envelope Well beyond said seal.
  • An X-ray tube comprising a glass envelope having a re-entrant portion and an anode structure having a glass-to-metal seal with said reentrant portion and comprising a target, a shield about said target and extending oppositely from said re-entrant portion, a second cylindrical shield extending from the target over said seal and over said re-entrant portion well beyond said seal, and a transverse member in said second shield and cooperating with said second shield to prevent bombardment of the seal between said re-entrant portion and said anode structure.
  • An X-ray tube comprising an envelope having a re-entrant portion, a cathode structure sealed to said re-entrant portion and comprising a iilament and focusing cup, a cylindrical shield extending from said cup over said seal and over said re-entrant portion Well beyond said seal, and a transverse member in said shield cooperating with said shield to prevent electronic bernhardment of said seal.

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US43816A 1935-10-07 1935-10-07 High voltage x-ray tube Expired - Lifetime US2167275A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE417964D BE417964A (enrdf_load_stackoverflow) 1935-10-07
US43816A US2167275A (en) 1935-10-07 1935-10-07 High voltage x-ray tube
FR811639D FR811639A (fr) 1935-10-07 1936-10-07 Perfectionnement aux tubes à rayons chi à haute tension

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US43816A US2167275A (en) 1935-10-07 1935-10-07 High voltage x-ray tube

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US2167275A true US2167275A (en) 1939-07-25

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BE (1) BE417964A (enrdf_load_stackoverflow)
FR (1) FR811639A (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2688709A (en) * 1949-11-12 1954-09-07 Westinghouse Electric Corp X-ray anode and method of making same by electric welding
US2821650A (en) * 1951-09-28 1958-01-28 Gen Electric Method of obtaining vacuum tightness in cast metal structures of thin section and resulting products
US3179832A (en) * 1960-01-12 1965-04-20 Field Emission Corp Temperature enhanced field emission x-ray tube
US3331975A (en) * 1965-02-19 1967-07-18 Varian Associates Cooling apparatus for cathode getter pumps
US20050058253A1 (en) * 2001-10-19 2005-03-17 Hamamatsu Photonics K. K. X-ray tube and method of producing the same
US20050184640A1 (en) * 2004-02-25 2005-08-25 Hirofumi Yamashita Cold-cathode fluorescent lamp and backlight unit
US20050201519A1 (en) * 2002-04-02 2005-09-15 Bathe Christoph H. Device for generating x-rays having a heat absorbing member

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2688709A (en) * 1949-11-12 1954-09-07 Westinghouse Electric Corp X-ray anode and method of making same by electric welding
US2821650A (en) * 1951-09-28 1958-01-28 Gen Electric Method of obtaining vacuum tightness in cast metal structures of thin section and resulting products
US3179832A (en) * 1960-01-12 1965-04-20 Field Emission Corp Temperature enhanced field emission x-ray tube
US3331975A (en) * 1965-02-19 1967-07-18 Varian Associates Cooling apparatus for cathode getter pumps
US20050058253A1 (en) * 2001-10-19 2005-03-17 Hamamatsu Photonics K. K. X-ray tube and method of producing the same
US7058161B2 (en) * 2001-10-19 2006-06-06 Hamamatsu Photonics K.K. X-ray tube and method of producing the same
EP1437757B1 (en) * 2001-10-19 2011-05-18 Hamamatsu Photonics K.K. X-ray tube and method of producing the same
US20050201519A1 (en) * 2002-04-02 2005-09-15 Bathe Christoph H. Device for generating x-rays having a heat absorbing member
US20050184640A1 (en) * 2004-02-25 2005-08-25 Hirofumi Yamashita Cold-cathode fluorescent lamp and backlight unit
US7595583B2 (en) * 2004-02-25 2009-09-29 Panasonic Corporation Cold-cathode fluorescent lamp and backlight unit

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BE417964A (enrdf_load_stackoverflow)
FR811639A (fr) 1937-04-19

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