X-ray generator

<img file="US2329318A_D0001.tif" />

1943.

Z. J. ATLEE ETAL

X-RAY GENERATOR

2,329,318

Filed Sept. 8, 1941

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Patented Sept. 14, 1943

2,329,318

UNITED STATES PATENT OFFICE

2,329,318

- X-RAY GENERATOR Zed J. Atlee, Elmhurst, and Howard W. Brackney, Chicago,IIl.,assignorstoGeneraIElectricXRay Corporation, Chicago, ΙΠ., a corporation of .· New York

Application September 8, 1941, Serial No. 409,934

Claims. (Cl. 250—89)

This invention relates in general to electronics and has more particular reference to the construction of X-ray generators, more especially a generator for use in the application of X-rays in body Cavities for therapeutic and other purposes. .5:

An important object-is to provide an X-ray generator for. contact and cavity therapy, and to this end to provide a shock proof generator having: facilities for cooling the same whereby to prevent patient discomfort when under treat- 10 ment in contact with the generator.

Another important object is.to provide a generator of the character mentioned having a generating. anode formed for insertion as in a body cavity including, means to jacket the anode for 15 heat dissipation without materially reducing effective X-rays emitted by said anode when the generator is in operation; a 'further object being to utilize jacketing means-having a window at the X-ray emitting, portion of the anode and 20. formed of material -substantially transparent to X-rays; a still·further object being to form the jacket window of beryllium. . :

' A still further object is'to form the jacket as a tube Of suitable material surrounding the pro- ,25 jecting anode and having a beryllium disc secured.in fluid tight fashion at the'end of the tube adjacent to the X-ray emitting end of the anode;

Another important object is to utilize a pair of concentric tubes around the projecting anode $0 whereby to. accomplish jacketing by flow, and counterflow,of a suitable cooling fluid through the concentric anode, jacketing tubes.

Another important object is.to form t he pro jecting anode-as a tube of metallic material such Sa as copper having an anode, target fitted at the projecting end of the tube; a further object being to .utilize..gold -as-, a.-target material; a still further object being to utilize as a target a plate of gold, or other suitable material, made just thick 4.0 enough to stop a,substantial percentage of primary, electrons to thereby maintain X-ray absorption at a minimum; yet another object being to support the target plate upon a beryllium disc sealed in the end of the tube and carrying the 45 target material plated thereon to the desired thickness of the order of 0.00004 inch or 2.0 microns, which, is the thickness of gold capable of stopping 90% of the electron beam applied on the target at 70 kv. p. 50

Another important object is to form the anode as a metal tube preferably comprising copper having a monel bushing silver soldered at the end of the tube and upon which bushing is secured a

Window, disc: of beryllium brazed to-the bushing 55 preferably; with copper silver soldered and having a thin gold plated film upon the inner surface of the window disc.

Another important object of the invention is to provide a,n improved electrode configuration and relationship, and more particularly to immerse the cathode in the anode whereby to ensure that the electron source at the cathode and the entire electron beam between the source and. the anode target are completely shielded from the intense electric ’ charges that collect upon the walls of the generator envelope during, operation, thereby eliminating completely the biasing effect that would otherwise be imposed by said’wall charges on the electron beam and result in deflection thereof.

Another important object resides in providing a generator comprising a tubular projecting anode mounted in a collar or flange forming a support frame, the flange carrying an annular rim extending on the side of .the flange opposite from the tube and supporting a preferably glass envelope having a glass-to-metal seal with said rim, the glass envelope serving to support the cathode structure therein in alignment with the anode tube and said flange carrying a sleeve-like shield in concentric alignment with the anode tube,, the cathode being supported in position with , its electron emitting element immersed within , the shield. .

. Another important object is to provide a shock proof supporting casing for.the generator including facilities for jacketing the. projecting anode for the circulation of a cooling. fluid such as water thereabout; a further object being to form the casing, with, means, for focusing electrons upon the anode target during the passage thereof through the anode tube from .the cathode; a further object, being to utilize ap annular magnet in the casing in. position surrounding the projecting anode of a tube supported in the casing; a further object being to provide the casing internally with conduit means for supplying and circulating a cooling fluid such , as water around the anode portions of ..a generator in the casing.

Another important object is to. provide a casing for a generator of the character mentioned wherein the casing comprises cooperating parts including a preferably ‘ tubular portion forming a container in which the generator may be insulated as by immersion in oil and an external housing adapted to enclose the casing arid generator including the projecting anode portion of the generator, the external housing carrying facilities for cooling the projecting anode portion of the generator and for focusing the electron beam therein when the generator is in operation; a further object being to form the inner casing as a cylindrical tube affording a mounting at one end for the generator and a mount- 5 ing at the other end of the casing for a bushing containing electrical connections for powering the mounted generator from an external source of electrical energy.

Another important object resides in provld- 10 ing means to compensate for the expansion and contraction of insulating oil within the inner casing; a further object being to utilize expansion means preferably comprising synthetic rubber forming a bellows within the insulating chamber. 15

Among the numerous other important objects of the invention is to provide a safe X-ray generator for contact and cavity thereapy; a generator of simplified design having an improved anode structure in combination with an im- 20 mersed cathode thereby improving the operating characteristics of the device more particularly with respect to uniformity of electron flow; a device cf the character mentioned having a shock proof casing in which all high voltage _2gparts are oil immersed and thus safely insulated, the casing including novel means to compensate for expansion and contractions of the insulating oil therein; a device in which the anode structure is jacketed for cooling the same with- ₃θ out impairing X-ray emitting efficiency, and wherein, more particularly the anode and its cooling jacket is sized for insertion easily as in a body, cavity to thereby facilitate X-ray treatment of body tissues in direct contact with the ₃₅X-ray generating source.

The foregoing and numerous other important objects, advantages and inherent functions of the invention will become apparent as the same is more fully understood from the following de- 40 scription, which, taken in connection with the accompanying drawing, discloses a preferred embodiment of the invention.

Referring to the drawing:

Figure 1 is a sectional view taken longitudi- 45 nally through an X-ray generator and casing embodying the present invention;

Figure 2 is a sectional view, along the line 2—2 of the X-ray generator shown in Figure 1; and

Figure 3 is a sectional view taken substan- ₆q tially along the line 3—3 ih Figure 1.

To illustrate the invention the drawing .shows an X-ray generator II comprising an anode 13. a.cathode 15 and envelope means 1.7? enclosing the anode and cathode. _gg

The anode 13 preferably comprises, a disc 19 of material, such as beryllium, which is substantially transparent to X-rays. The. disc is sealed in the end of a preferably copper tube 21 Which forms a part of the hermetic envelope .17. The „_ beryllium disc 19 may be secured at the end ⁶⁰of the tube 21 by brazing it with preferably 50-50 copper silver solder to a bushing 23 preferably made of monel metal, which is secured as by silver solder in the end of the tube 21. _ggit will be understood that X-rays generated at the disc 19 by electronic impact thereon will be projected through the disc and outwardly of the end of the tube .21 and thus made available for therapeutic purposes. By utilizing a tube 70 of small diameter the same may be inserted as in a body cavity in order to allow treatment, of tissues: within the cavity. In order to develop. X-rays at the disc 19 it is necessary to provide a suitable target for the reception of electrons 75 and capable of developing X-rays in response to electron impingement thereon. To this end the target may comprise any suitable target material but we prefer to employ gold for the purpose. Consequently, the surface of the disc 19 facing into the tube 21 carries a layer of gold 25 thereon for the purpose of providing an anode target. The gold forming the target 25 is preferably applied on the beryllium disc 19 by electroplating the gold thereon to a thickness of the order of 2.0 microns or 0.00004 inch, which is the thickness of gold capable of stopping substantially all electrons Impinging thereon thereby providing for the efficient generation of X-rays substantially all of which may escape outwardly through the disc 19.

The end of the tube 21 opposite from the end in which the disc 19 is fitted, is sealed in an opening 27 formed through a plate 29 which forms a part of the envelope 17 and which provides a means for mounting the generator in operating position._: .

The generator envelope 17, in addition to the tube 21 and plate 29, comprises a preferably cylindrical portion 31 which may conveniently comprise glass, the portion 21 being sealed at one end by means of an annular glass-to-metal seal 33 upon the rim of a metallic sealing member 35 which has an inwardly flanged portion sealed as at 37 upon an annular seat formed in the plate 29 around the opening 27 thereof. The end of the envelope portion 31 remote from the seal 33 is preferably formed with a re-entrant sleeve 39 having an annular edge extending withip the portion 31 and scaled, as by the glassto -metal seal 41, upon the rim of a metallic cup shaped end seal 43 which serves also as a support for the cathode structure 15.

The cathode structure 15 comprises a head 45 formed with a socket 47 in alignment and facing toward the plate mounted end of the tube 21. An electron emitting element, preferably a fllament 49, is supported on the head 45 adjacent the bottom of the socket 47. The head 45 is supported as by the intermediate frames 51 and 53 on a stem 55 which projects through and which is sealed in a central Opening formed in the bottom of the cup shaped end Seal member 43. The head 45 and the support members 51 and 53 are hollow to accommodate electrical conductors 57 which are connected with the filament 49 and which extend thence through the head and the Hollow support members and through seals formed in the bottom of the seal member 43. The member 51 may also carry a cylindrical skirt 59 which surrounds and encloses the support member 53, the seal member 43 and the glass-to-metal seal 41 for the purpose of Shielding the seal 41 from impingement by stray electrons. The skirt 59 also defines a chamber in which may be disposed gettering means 61 illustrated as a hollow metallic wire containing a gettering medium such as barium, one end of the wire being grounded as on the frame member 53 and the other end being connected to a conductor 63 which extends through a seal in the member .43. :

In conditioning an X-ray generator for operation, it is necessary to remove all gas present within the envelope, and also any gas occluded in the electrodes and in the material of the envelope itself. If such occluded gases are not substantially entirely removed, they will gradually be released within the envelope and impair

2,329,318 the exhausted condition, at which the device , is designed to operate. Removal of gases from the envelope is accomplished by baking or otherwise heat treating the entire device at a temperature short of the softening point of the glass, while maintaining the envelope in connection with a suitable exhaust pump, and by heating the electrodes to a high temperature, either by electron bombardment or by placing the electrodes in a magnetic field fluctuating at frequencies at the order of radio frequency.

After all gas including occluded gases and other impurities have thus been removed from the envelope, the exhaust connection may be sealed off, as at 65, and as a final step the gettering material may be volatilized within the envelope in order to form gettering end products in which any trace of gas or. other impurities are combined with the gettering material to form inert and innocuous material which remains within the envelope during the service life of the device in the form Of a fllm-Iike deposit upon the inner surfaces of the skirt 59 upon which the gettering end products condense as a result of the gettering operation.

The gettering material,' which is preferably barium and/or magnesium contained in the hollow wire 61 may be volatilized by applying electrical potential between the conductor 63 and the stem 55 thereby heating the wire 61 and vaporizing the gettering material contained therein, the wire having a weakened wall portion longitudinally thereof through which weakened wall portion the vaporized gettering material may be expelled into the chamber enclosed by the skirt 59.

It should be understood that an X-ray generator functions to produce X-rays at the target 25 by the impingement thereon of electrons generated and emitted at the cathode element 49 and directed as a stream upon the target under the influence of electrical potential applied between the cathode filament and the anode target. The cathode is energized for electron emission by the application of filament energizing potential between the conductors 57.

Although the operating potential applied'between cathode filament and anode target serves to direct the electrons in a stream focused upon the target, various disturbances may cause some of the electrons to escape from the stream and become stray electrons within the envelope, which stray electrons impinging on the envelope walls and particularly upon the glass portions of the envelope may build up charges haying deleterious effects upon the. generator. Such charges may etch and weaken the walls and may puncture the envelope particularly. at the end seals 33 and 41. Furthermore, when operated at high voltage, the charges built up on the walls as a result of stray electron impingement may exert electrostatic effects upon the electron stream arid cause it to deviate from the desired flowpath .between the cathode and the target 25. In order to minimize the effects of stray electrons we immerse the electron emitting portions of; the cathode within the anode by providing a preferably cylindrical shield 67 in positiori embracing the electron emitting portions of the cathode, said portions being, immersed in said shield, one end of which is secured as by soldering the same upon a mounting ring 69 which is fastened as ,by means of screws 71 upon the plate 29 in position surrounding the opening 27. The shield 67 not only serves to minimize the occurrence of stray electrons in the envelope but also aids in guarding the electron stream from the electrostatic effects of envelope wall charges.

It will be seen from the foregoing that our in5 vention contemplates the provision of an X-ray generator having an anode target forming an X-ray source arranged in a fashion to permit the same to be inserted as in. a body cavity for the treatment of the tissues of the cavity; and it 10 will be seen that the arrangement , of the anode target at the end of the relatively slender elongated tube 21, which may be anywhere from 6 to 18 inches in length, affords a convenient treatment of body cavity tissues.

j₅ It should be understood, however, that the operation of an X-ray generator is accompanied by the generation of appreciable quantities of heat particularly where the generator is designed for. high; tension operation. We contemplate ap₂₀ plication of our present invention in high voltage generators adapted to operate at voltages of the order of 70 kv. p. and our invention embraces means not only for rendering the device shock proof but also for cooling the anode structure to enable the device to be used for therapeutic pur²⁵ poses in body cavities without causing undue patient discomfort. To this end we provide casing means serving not only to render the device shock proof but also to cool the anode structure.

The casing means comprises a preferably cylin³⁰ drical shell II for receiving the generator, the shell preferably comprising relatively thin sheet metal stock and haying a mounting ring 73 sealingly secured at one end of the shell 71 in position to form an annular support for the marginal edge of the generator mounting plate 29. The plate 29 may be secured on the mounting ring 73 as by means of the fastening screws 75 to support the generator with its anode structure projecting _ outwardly of the.casing 71 at one end thereof, the cathode end of the generator including the envelope portion 31 and the seal member 35 being enclosed within the shell 71, and the mounting plate 29 forming a sealed closure at the end of the shell 71. The other end of the shell 71 has ⁰ a mounting ring 77 sealed thereto in position to form support for a cable bushing 79 which may be secured in place by means of a clamp ring 81 and fastening screws 83 to receive a standard cable plug 85. The bushing 79, of course, may be °^υ provided with contact means 87 adapted to form electrical ' connection with the conductors 57 which are suitably anchored on a terminal block 89 carried on the stem 55 outward of the generator in position to engage the bushing contacts 87.

The shell 7 ( forms a chamber 91 within which the generator is enclosed preferably in position immersed in a suitable insulating medium such as oil. The chamber 91 around the generator may be charged with oil through a filling opening ⁶⁰ defined by a bushing 93 Which is normally sealed as by means of a closure plug 95. In order to accommodate for expansion and contraction of the Insulating oil within the chamber 91 we provide compressible means. 97 in the form of an 6? inflation device within the chamber. This-inflation device comprises, in the illustrated embodiment, a hollow annular expansion element filled with a suitable gas under -slight pressure, the inflation device being adapted to expand un70 der the influence of the gas therein and accommodate any contraction of the insulating oil within the chamber 91. The inflation device 97 preferably comprises an annular member of rubber-Iike material, , such/as neoprene, or other suitable elastic material which is impermeable

4- 2,32 and .not subject to deterioration in coiltact with oil. The annular member 91 is preferably assembled in the shell 11 in position embracing the generator and may be conveniently-anchored by forming the member* 97 with an annular groove 99 at one end in position to receive an annular flange 10 i formed oh the mounting ring 73.

The device is rendered, substantially shockproof by grounding the shell 71 and the anode structure of the generator mounted thereon and 1 by applying the high operating potentials to the generator through the shock-proof insulated structure comprising' the plug device 85 and the bushing 79 on the high tension conductors.

For the purpose of cooling the anode structure, 1 we provide jacketing means 103 surrounding the anode tube 21, together with facilities for circulating a cooling ·' fluid ^: through ^! the jacketing means and around the anode. The jacketing means comprises a pair of concentric tubes'105 2 and 107 interconnected by spacing means 109 which also carries a beryllium end closure disc 111 at one end of the tubular jacket structure. The tubes 105 and 107 at the other end of the jacket structure are secured in a support collar H3 2 which in turn may be anchored'on the generator mounting plate 29 as by means of screws 115. The support collar 113 also carries an inlet pipe 117 and an outlet pipe 119 for the circulation, of a cooling fluid,. preferably water, to and from the 3 jacket structure 103. To this end the inlet Pipe 117 is connected through the outer jacket tube 105 and into the inner tube ί 07 to deliver the cooling fluid within the inner tube and directly upon the outer... surfaces of the. anode tube 21, 3 near the plate, anchored end of said anode tube. The. cooling fluid: may flow thence toward and around the target end of the tube 21 and pass thence between the inner tribe .1.07 and the outer tube 1.05 to the outlet pipe 119 which is fitted int o the outer tube adjacent, the mounting plate 29. Tiie pipes 117 and 119 extend radially from, the jacket structure to the marginal edge of the mounting plate 29 and thence, extend longitudinally of the shell 71 to the remote end thereof ₄where they may be fitted with means for connection to suitable apparatus for circulating the cooling fluid.

For the purpose pf focusing the electron stream upon a localized area of the target 25 we mount c ail annular magnet 121 in position encircling the anode tube 21 near the end thereof which is secured on the plate 29. This focusing magnet 121 may comprise merely an annular ring of magnetic material forming. a permanent magnet _eor may take the form of an electromagnet comprising cooperating members 123 and 125 forming an annular shell containing a winding 127 adapted to be energized through conductors 129. The focusing magnet 121 has a central opening _cthrough which the anode tube 21 and the jacketihg shells 105 and 107 extend so that the magnet may be mounted against the pipe carrying collar 113; and the magnet may be enclosed in mounted position by an outer casing131 having cylindrical g walls 133 enclosing the casing 71 and the pipes 117 and 119, and a portion 135 enclosing ^!the magnet 121 and formed with an opening through which the j acketing means 103 and the anode tube 21 extends. The casing 131 at its end remote 7 from the magnet enclosing portion 135 may be secured to the casing 71 by suitable fastening devices.

It will be seen. that the device pi our present invention is of simplified construction affording 7,

9.318 convenient means for contact and cavity therapy ; that the several parts may be readily torn down for repair or replacement; that all parts are thoroughly insulated to thereby afford maximum 5 protection agaihst electrical shock; that effective means is provided for adequately cooling the anode to permit the application thereof in contact with body tissues without discomfort; and that the device affords a convenient means for the 0 accomplishment of X-ray therapy.

It is thought that the invention and its numerous attendant advantages will be clearly understood from the foregoing description; and it is obvious that numerous changes may be made in 5 the form, construction and arrangement of the several parts without departing from the spirit and scope of the invention, and without sacrificing its attendant advantages, the form herein disclosed being merely for the purpose of demon0 strating the invention.