US2167275A - High voltage x-ray tube - Google Patents

High voltage x-ray tube Download PDF

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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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tube
cathode
anode
envelope
cup
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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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    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05GX-RAY TECHNIQUE
    • H05G1/00X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08Electrical details
    • H05G1/68Circuit arrangements for Lilienfield tubes; Circuit arrangements for gas-filled X-ray tubes
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00X-ray tubes
    • H01J35/02Details

Description

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L A TTG/NE YS July 25, 1939. M.. J. GROSS Er AL HIGH voLTAGE x-RAY TUBE Filed OCT.. 7, 1935 Patented July 25, 1939 UNITED STATES PATENT OFFICE assignors to General Electric X-Ray Corporation, a corporation of New York Application October 7 16 Claims.
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,
voltages in excess of two hundred kilovolts peak. Certain features of the invention, however, are of value in connection with tubes operated at voltages lower than that named, as will be described later herein.
Heretofore, X-ray tubes adapted for satisfactory operation at voltages up to two hundred kilovolt peak, have been available. Operation of such tubes, however, at voltages above two hundred kilovolt peak, seriously ourtails their useful life. The short life of tubes of the character heretofore provided, when run at such higher voltages coupled with the cost of building such tubes for high voltage operation, has rendered the operation of such tubes excessivel;7 expensive.
The operation of X-ray tubes of the class heretofore provided on voltages higher than three hundred kilovolt peak has been found to be substantially impossible since the expense burden is prohibitive for conventional medical and com- 25 mercial use, such as the radiographing of welds in heavy steel vessels, and the like.
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.
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,
comprising such tubes, are cemented together and the whole structure must be carefully aligned and mounted rigidly on a base.
In addition to the construction difculty just enumerated, 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. These twoI factors, 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 tubesactually require, for best results, a separate building for the tube and its energizing equipment.
It is an important object of the present invention to provide an X-ray tube especially adapted lor operation at the high voltages mentioned, three hundred kilovolt and above, independently 1935, Serial No. 43,816
of vacuum pumps, wherein the tube is relatively small permitting it to be housed in the structure which can be handled conveniently for therapeutic or commercial application.
As can be realized, some of the phenomena 5 which have been discovered and the interrelations of such phenomena may be difficult of numerical representation. It is felt, however, that the principles as outlined in this specication and as recited in the appended claims, if properly ap- 10 plied, will permit of the design and manufacture of a tube by which the objections inherent to previously built types of tubes are overcome, and satisfactory and economical operating characteristics assured.
With full knowledge of the existing art, and with the object of discovering the causes of rapid failure of tubes when operated at high voltages extensive research was undertaken. We found that X-ray tubes in operation are susceptible to 20 the formation of brown spot, which, as the name implies, is a discoloration of the glass envelope. These spots are produced by localized electronic or ionic bombardment of the envelope and initially cause no trouble. During the operating life of the tube, however, brown spot produces microscopic channels or canals in the envelope, which soon penetrate the entire wall thickness and thus destroy the tube. Consequently, We have directed our research to determine the cause and prevention of brown spot since no satisfactory solution for the problem has heretofore been offered.
The successful operation of a tube at high voltages, in accordance with the present invention, 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. In the operation of an X-ray tube, electrons impinge the target and are reiiected to the glass walls of the tube where such electrons produce a difference in potential between the inner and outer surfaces of the glass itself. The dielectric strength of the glass of the tube must be suiiciently high to withstand rupture under the strain so produced.
For voltages up to two hundred kilovolt, 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.
We have discovered that, as voltages are increased beyond two hundred kilovolts peak to five hundred and one thousand kilovolts peak, in the operation of X-ray tubes, the magnitude of the electron charge on the glass envelope becomes so great that some means for directing these excess electrons away from the glass envelope is imperative if the tube is to be saved from speedy destruction as a result of brown spot.
The control of electrons in an X-ray tube may take place in three different spheres, viz:
(a) Proper control of the emission of electrons at the cathode;
(b) Prevention of electron impingement on the envelope of the tube; and
(c) Prevention of cold cathode emission from any surface within the tube.
Failure to recognize each of these factors and to supply means for providing the necessary control thereof may result in the troubles, particularly the production of brown spot, which produce tube failure.
In addition to the above trouble, 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.
Our investigation has shown that the electron discharges, which produce brown spot can be eliminated by preventing cold cathode emission from the electrodes. The elimination of cold cathode emission can be realized by increasing the spacingof the electrodes in a tube,
' by decreasing the field intensity on the electrodes,
by increasing the radii of curvature of the electrodes, and by improving the cleanliness and smoothness of the surfaces of the electrodes by proper processing.V
' The dimensions of the glass envelope of aA tube which would appear to be important have been found to have no bearing whatever on "brown spot formation, although as a rule the size of the glass envelope cannot be reduced below *certain minimum value because of other factors.
Regardless of howlarge an envelope is made, brown spot -will inevitably make an appearance if the electrode design in the tube is not correct.
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) From the filament of a tube when the latter is heated to a point where emission normally takes place;
(b) From any point either on the anode or on the cathode having the proper geometrical relation with any other point whose potential is beyond a certain definite value with respect to the spacing between the electrode and such point; and
(c) Electrons emitted from the target of a tube as an incident to the target being bombarded by the main electron stream from the cathode` A structure which will permit of the operation of a tube at the desired high voltage and Linder the conditions which havebeen laid down as being best for the user must control all of the sources of electronic or ionic emission. Where such emission'cannot be avoided, the structure must provide for the absorption of its energy without unduly heating any portion of the tube. These results .have been accomplished by the vtube forming the subject matter of this application and in the preferred embodiment which will be described later.
Among the numerous objects of the present invention is` the provision of 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 positive ions that may beliberated in the operation of the tube; a tube of the character described having means whereby excessive charging of the glass walls of the tube is eliminated so that the tube may be operated at higher alternating current voltages than a tube of conventional design.
Among other important objects is to control electrostatic conditions within a tube of the character mentioned in. order to control free positive ions in the tube during operation of the same; to control electron discharge in the tube to prevent bombardment of the glass envelope thereof; to prevent undesired cold cathode effects within the tube; and in general to provide a tube `oi convenient commercial size including the methods of operating the same at high voltages over a substantially indenite service life.
While the principles of construction herein enumerated may be applied to a great number of different structures and to various types of vacuum devices, these principles have been worked out primarily for X-ray tubes and are for that reason best illustrated by reference to a tube of that sort, the preferred embodiment of the invention being shown in the attached single sheet of drawing hereby made apart of this application.
In the drawing:
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 ;Y
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.
Like reference characters are used to designate similar parts in the drawing and in the following description.
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.
In order, however, to reduce the absorption of primary radiation emitted from the tungsten button de and passing through the wall of the cylinder 52, a window of reduced section is cut into the thickened wall of cylinder 52 as shown at In the preferred embodiment of the invention 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. There is, of course, some additional heating of the window due to the section being so thin, but the proximity of the heavier walls to the thin section tend to absorb the heat from the window and thus prevent the metal comprising the window attaining too great a temperature.
In order to be most eflicient from a standpoint of stray electron absorption, there must be certain relations between the size of the opening of the shielding cylinder and its mean length. It has been found, for the best measure of absorption, that 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.
In practice, 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.
After the casting has been machined, 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 cylinder 5l' is positioned by means of the screws 58 and 5%.
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.
These dangers are avoided in the present structure by a design in which the entire head, together with a shielding cylinder, is cast in one piece of high heat conductivity copper to the one end of which an efficient cooling coil is attached by a joint of high heat transferring capacity. In this fashion not only is the absorption of the electrons had, but also any ill effects resulting from undue heating because of this absorption is avoided for the entire anode is cast in one piece thus avoiding losses in heat conduction from the point of absorption t-o the point of dissipation. This construction coupled with the fact that the structure is of very high conductivity deoxidized copper makes the anode highly efficient for its purpose.
A third source of electron emission not connected solely with either the anode or cathode, but rather associated with the spacing between them, is the so-called cold cathode emission. It has been found, however, that if the tube is to operate satisfactorily, certain minimum distances, which also depend to some extent on configuration and cleanliness of the electrodes, are required for each operating value of voltage.
In such tubes as those shown by Coolidge in the patents hereinabove referred to and which under practical operating conditions are permanently connected to pumping systems, no attempt is made to obtain cleanliness of surfaces. Very large electrode spacings are required if freedom from cold cathode effect is to be obtained. The dimensions of the spacings referred to are two to three times as great as those which are necessary with a tube built in accordance with the present invention.
In the present design, it has been found that a minimum of spacing of three and one-half inches is required for operation at ve hundred kilovolts peak, while a distance of three inches is required for four hundred kilovolts peak. If spacings smaller than these values are used at the voltages specied, there will be some cold cathode electron emission, which will directly or indirectly produce bombardment of the glass envelope.
The bombardment so procured will inevitably result in the appearance of brown spot and eventually there will be a rupture of the walls of the tube and the destruction of its usefulness.
In order to more clearly define what is herein termed minimum spacings, it is shown what spacings are best for the different values of operating voltage for a tube built in accordance with the present invention:
Four hundred kilovolts peak Three inches Five hundred kilovolts peak Three and onehalf inches Seven hundred kilovolts peak SiX inches One thousand kilovolts peak Ten inches material. In the preferred embodiment of the invention, this is made with one of the hard or borosilicate glasses, such as Pyrex. 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.
The 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. Y
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.
In practice, 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| is slipped back into the position in which the screws 32a may be inserted, after which the cathode cup is mounted in place is shown and the screws 32 inserted and s-crewed home.
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.
As was stated in one of the objects of the invention, it is essential that 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.
While it can be said that the general principles of focusing cup design used previously on tubes of lower voltage capacity apply also to the design of the cathode in the present tube, it is also true that factors disregarded in the design of such tubes of lower voltage must be borne in mind in the design of a tube of the type herein described. In the low voltage tubes, unequal distribution of energy on the focal spot is essentially a reflection of unequal distribution of the electron beam as it leaves the environment of the cathode structure.
In the new high voltage tubes herein described where relatively large spacing between the anode and the cathode is employed, 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. In the design of cathodes for use in tubes for operation with relatively low voltage, 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.
In order that control of the paths of the electrons be obtained, it has been found that the design of the cathode must conform to the following specifications:
(a) The filament diameter should not be more than ..100 inch smaller than the size of the focusing opening in the cathode structure. In the particular embodiment of the invention dcscribed herein, 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.
Another point which must be taken into consideration 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.
In the presently described embodiment of the invention, 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. In the case of the structure herein shown, the top iii Vcathode cup, causing the When tubes operate on a pumping system, these values are approximately doubled. While the minimum values have been set up for two of the voltages, it is understood that for safe operation Values in excess of those given as minimums are preferable. For instance, for a tube of the sort herein described, it has been found desirable to use from four to four and one-half inches for ve hundred kilovolts peak operation and from three and one-half to four inches for four hundred kilovolts peak operation.
As has been described previously, three leads are brought out of the cathode end of the tube. Two of these, 29 and 30, are the terminals of the filament wire. 'Ihe center lead 33 is connected to the cathode structure proper. The purpose of bringing these leads out is to use the structure just described as a means for measuring gas pressure within a tube, either during exhaust, operation or as a means of testing a tube previous to shipment.
As shown in the diagrammatic sketch illustrated with this portion or" the structure, 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.
In a manner well known in the art, the current will now pass from the filament to the milliammeter to defleet. By means of a resistance 66, this value should be set so that the milliammeter reads l, under the conditions as they have been standardized. In an absolute vacuum, 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.
In the particular conguration shown by this tube, it has been found that 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. As can be readily understood, 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.
Another use can be made of the system just described. Where due to excessive heating or for any other reason there has been a liberation of gas within the envelope of a tube, such gases can be cleaned up by passing low voltage electrons between the lament and the cathode structure by the arrangement just described. What occurs during this process is probably quite intricate. Theories attempting to explain why the desired results are obtainable need not be advanced here. It is sufficient to say that the device described is capable of producing this cleaning up effect and so serves as a means of reducing unwelcome gas pressures and thus prolongs the life of the tube.
While all of the processes of the structure have been described from the standpoint of rectified voltage operation, it is apparent to those skilled in the art that these same structures will be beneficial in case the tube is operated on unrectii'ied alternating current.
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. With the old type tubes operation on alternating circuits having voltages of approximately one hundred nity kilovolts peak was considered the maximum, even for a tube capable voltage of two hundred kilovolts peak.
With tubes of the character herein described, however, voltages oi four hundred kilovolts peak are permissible, while tubes capable of operation at higher voltages may be readily built. The reason for this is the proper control oi electron emission and bombardment. Thus cold cathode discharges and building up of charges on the glass are substantially elimmated, and with these, the main causes for the breakdown ci tubes using unrectied alternating current has been removed.
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.
What is claimed as new and is desired to be secured by Letters Patent of the United States is:
l. 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.
2. 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.
3. 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,
of operating on a rectiiied` said cathode and its focusing cup being wholly within the cylindrical midsection of the tube, an anode in said anode arm and comprising a target, and a cylindrical shield about said target and extending in the direction of said cathode, said shield terminating in the midsection of said tube, and the target being wholly within said anode arm.
4. 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.
5. The X-ray tube described in claim 4, and in which the cathode and anode arms have reentrant portions of glass and said anode and said cathode have cylindrical metal shielding members surrounding the re-entrant portions of said arms, said cylindrical members extending in substantial parallelism with the glass walls of said anode arm and of said cathode arm, respectively.
6. 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.
7. 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.
8. 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.
9. 1n 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.
l0. In an X-ray tube, 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.
ll. in an X-ray tube, 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.
l2. 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.
13. 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.
14. 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.
15. 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.
16. 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.
MALVERN J. GROSS.
ZED J ATLEE.
US43816A 1935-10-07 1935-10-07 High voltage x-ray tube Expired - Lifetime US2167275A (en)

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FR811639D FR811639A (en) 1935-10-07 1936-10-07 Advanced chi-ray tubes at high voltage

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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
EP1437757A1 (en) * 2001-10-19 2004-07-14 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 (11)

* 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
EP1437757A1 (en) * 2001-10-19 2004-07-14 Hamamatsu Photonics K.K. X-ray tube and method of producing the same
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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FR811639A (en) 1937-04-19

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