US2665390A - Anode target - Google Patents

Description

1954 M. J. ZUNICK ETAL ANODE TARGET Filed Aug. 18, 1951 INVENTORS'- MICHAEL J. ZUNIGK HOWARD W. GOODRICK ATT'Y Patented Jan. 5, 1954 AN ODE TARGET Michael J. Zunick, Greenfield, and Howard W. Goodrick, Brookfield, Wis., assignors to Gen- Yor oral Electric Company,

a corporation of New Application August 18, 1951, Serial N o. 242,466

25 Claims.

The present invention relates in general to electronics and has more particular reference to electron targets, more especially targets fo1 use in electron flow devices such as X-ray generators.

An X-ray generator commonly comprises an assembly of elements including an electron emitter, an electron target, conventionally comprising a block or platze of metal, such as taungsten, and a sealed envelope enclosing the emitter and the target, the assembly commonly being referred to as an X-ray tube. X-rays are produced in such a tube by applying electrical potential for electron driving purposes between Ehe emitter and the target: to thus constitute the emitter and the target, respectively, as a cathode and an anode. The so applied potential is thus made efiective i;o impel, toward the anode target, electrons emitted at t;he cathode, X-rays being generated a1: the target as a result of electron impingement thereon.

Impingement of electrons on t;he anode target; results in the generation of substantial quantities of heat which, especially in high power tuloes, tends to deteriorate and ultimately to destroy the target element. In t;he interests of efi'icient X-1ay production, the generator tube is usually operated under conditions producing high temperatures in the target short: of the melting temperature of the target material. Various expedients are employecl for cooling the anode target: in oraler t;o hold the same ab a temperature, during operation of the tube, safely below a temperature at which the target becomes damaged or burned. Presently available expedients for cooling X-ray tubes, and particularly the anode elements thereof, impose limitatsions upon the electrical loadings under which t:he device may be safely operated, since it is neeessary t:o dissipate approximately 95% of the energy which is applied 130 the taube, for the operation thereof. This energy has to be dissipated from within t:he relatively thin layer of metal which constitutes the target, and such heat energy, especially in atube designed'for continuous operation, must be removed as rapidly as it: is generated as, ooher- Wise, the target: will reach a temperature approaching or exceeding the melting temperature of its constituent material, thus resulting in destruction of the target and failure of the taube. Tungsten is presently considered 110 be the best available target material, the same being most highly resistant to deterioration at the high tem peratures imposed by electron bombardment at; high intensity. As a consequence, for optimum performance, Xway. tubes embodying tungsten 2 targets are commonly designed for operation under the maximum loadings allowed by the limits of the physical characteristics of tungsten targets.

Commercial X-ray tubes employ either water; oil, or air, as media for the transfer of heat; away from the target. T0 this end, the cooling medium is commonly delivered continuously through a chamber formed behind t:he target, t:he medium being circulated between t;he chamber and an external cooler so that heat may be absorbed from the target: into the medium and then extracted from the medium at the cooler. Water and 011 have relatively 10W boiling points and relatively poor heat; storing capacity, which limits their effectiveness for heat absorbing and transferring purposes.

An important object; of the present invention is 150 provide an improved electsron target from which heai; may be readily dissipated.

Another important object is t7o utilize metal in liquid condition for electron target: purposes; a further object being employ liquid mercury as an electron target.

Another object is t;o use any metal having relatively low melting temperature as a liquid elentron target; a further object being to employ lead, bismuth, thallium, sodium, potassium, lithium, t;in and like metals, or alloys thereof, in liquid condition, for electron target purposes.

Another important object is to provide for coutinuously circulating the liquid metal from target; forming position to cooling means, in order t;o continuously extract from the liquid metal t:he heat generated therein through use thereof as an electron targec.

Another important: object is to provide an anode target for X-ray generation comprising means, substantsially transparent t;o X-rays and electrons, forming a contsainer for a metal in liquid condition, vvhereby to ret;ain the liquid metal in position to serve as an electron target; a further object being t;o provide for circulating the metal in liquid condition through the charnber and thence to a cooler in order co maintain the liquid 1t:argetz material at: a desired operating temperaure.

Another important object resides in providing a new method of generating X-rays by causing electrons 1:0 impinge upon the surfaoe of a body of liquid metal 1:0 constitute the same as an X-ray generating anocle.

The foregoing and numerous other important objects, advantages and inherent functions of the invention will become apparent as the same is 5 vided for rr'1aintaining the metals in fused condition, or for draining them from the anode structure when the X-ray tube is not in use.

'Ihe present invention thus contemplates an anode target structure i3 providing means for supporting a, muss or pool of metal target material in liquid condition in position such that a surface cf said pool may form an anode target surfa-ce for thc impingement thereon o1 electrons, the invention further contemplating means for continuously cooling the liquid metal, as by circulating the same between the target structure and suitable cooling means for the extraction of operating heai: therefrom, and the consequent removal cf such hea.t from the generating tube, along with the circulating liquid metal. T these ends the target structure may ccmprise chamber er conduit forming means 24 disposed at theanode end cf the envelope und providing a chamher er container for supporting a pool of liquid metal in position, in the generator tube to function a.s an anode target.

As shown more particularly in Fig. 2 of the drawings, the chamber forming meang 2 1 may comprise a chamberecl member adapted to be sealingly secured in Ehe end cf the tubular envelope portion E3 as by welding, brazing er other-- wise sealing the, end edges of said tubular portion, as at 26, in a peripheral groove 277 formed in the member 2.5. The member 25 also may be formed With a. central b0re 01 channel forming a cham her 28 opening ab the opposite encls of th member 25, said member ab one end being formed With an annular seat 2i3 for the sealing reception of a preferably cup-shaped cover cap 3EB in positiou closing that, end cf the chamber 23 which fa.ces into the tubular portion I8 of the envelope. The member preferably comprises material Which is inert to bot mercury or other liquid ta1get forming substance. T0 this end, iron, nickel, molybdenum, 01' al1oys thereof may be employed, ferrous alloys containing nickel being especially suitable. 'Ihe cap 01 cover 30 is formed cf beryllium, or ocher material high1y perme able to electrom anal X-rays. 'Ihe member 3 may be sealingly secured. 021 the member '25, in the seat 29, by braziug the parts together With a layer 3l comprising a suitable bonding material, such as nickel, tha1; is inert to the hot target forming substance. Ib Will be seen that the end of the chamber 28 remote from the cover member 353 opens outwardly of the member 25 at the end cf the tubular euvelope portion H8. A preferably removable closure member 32 may be provided for normally ccvering the open end of the charaber 28, whereby to adapt the same 170 retain a meta1 in liquid condition as a pooi extending immeciiately behind tll cover element 3ti. The closure member 32 may comprise a plate sealed in position 011 the member 25 as by means cf bolts 33 anal a. gasket M. Conduits 35 und 36 may extend in the closure plante 32 in order to provide for circulating liquid meta1 into and out of the chamber 23, the conduits 35 and 35 being sealed in the closure plante 32. The conduit 36 may extend through the plate 32 and into the cavity 28, preferably centrally thereof, with the end cf the conduit opening within and directly behind izhe cover .member 3B. The other conduit 35 may open through the plate 32 directly into the chancber 28 ab the end thereof remote from the cover member 3ii. These conduits 35 and 36 may extend 150 and communicate With suitable co0ling apparatus whereby the anode metal in cooled liquid condition may be delivered. through the conduit 36 immediately behind the covr member 39 anal displace previously delivered liquid from the chamber 28 through the conduit 35 the cooling apparatus.

From the foregoing it Will be seen that the structure provides a, body or pool cf liquid metal immediately behind the cover mcmber 39. Such poo1 has a surface defined by saiol cover membei in position to receive the impact cf electrons delivered fron1 ehe cathode, the enclosing cover member 3ii beim; substantially transparent or pervious the so delivered electrons. The surface cf the pool, defined by the member 30, thus forms an anode target Which, when subjectecl to electron impingemcnt may be constituted as a source cf X-rays. Since the member 39 comprises material that is also substantially transparent to X-rays, any rays developed ab the surface cf the pool, as the resul1; of electron impact thereon, may pass thence through the member 3%, as at the sides thereof, for emission laterally cf the envelope portion I8, as through the X-ray window 23.

As shovvn in Figs. 3-7, the present invention is susceptible 0f embocliment as an exceeclingly simple structure merely comprising a tube or pipe 3 disposed in the envelope portion I8 in positicn exposed to electrons emitted. by the cathode i2. Thls tube 36 preferably c0mprises beryllium or other material substantially transpareni: Eo X-rays and electrons. The tube 36' may be mounted in diametrally disposed openings f0rmed in the envelope portion Hi and suitably sealed. in said openings, as by welding or brazing, as indicated at 34. The opposite ends 35' und 35' of the tube ma.y be connected with cooling und circulating mechanism for the delivery of liquid metal continuously from the cooling mechanism thrcugh the tube 3G anal thence back to the cooling mechanism. In such a construction the terminal end of the envelope portion HE, behind the tube 3G, may be providecl With a cover 32' suitably sealed i:o the end of the envelope portion Hi, as by welding or brazing the parts together as at 255. As indicated in Figs. 4'7 the portions of the tube 30 disposed within the tubula.r portion 28 of the envelope may ha.ve any dcsirecl or preferred cross-sectional configuration, including the circular, oval and rectangular shapes shown; anal where the sectional shape is other than circular, as shown more particularly in Fig. 6 of the drawings, the taube may be mountecl at any desired inclination in oraler to disperse Xrays, generated at such inclined target element, outwardly o1 the X-ray taube in a desired direction. Where the anode structure comprises a tube iia mounted diametrally of the envelope portion i, as shown in Figs. 4, 5 anal 7, it; Will be seen that X-rays may be emitteol ab opposite sides 0I" the envelope, as through windows 23 anal '23.

Ii desirecl, supplementary cooling means may be provided, the same comprising means for circulating a coo liug fiuid, such as oil, water or Ehe like, in heat exchange relationship With the anocie end cf the X-ray tube. Such means, in a. structure cf the sort sh0vvn in Fig. 2 of the drawingsor in a structure emloodying an open pool 01 liquid in the X-ray tube envelope may comp1ise ducts or channels formed in the liquid meta.1 containing member, in heat exchange relaionship with the liquid metal therein, anal including means for circulating a cooling fiuid between externem] coolin-g apparatus and such coolingcoi1duitsf0rmed in the member 25.

As shown in dotted lines in Fig. 3, however, the supplementary cocrling means may comprise a preferably sheet metal jacket str'u0ture 31 sealed upon the anode end of the envelop portiori i8, such jacket means providing an inlet and outlet conduit 39 communicating with the chamber 38 for the circulation cf a cooling fluid in heat exchange relationship with the anode end 01: the X-ray tube, including the anode structure 14 comprising the pipe 3il', the jacket including meang 40 for sealing the jacket around the opposite ends of the pipe 30' outwardly of the envelope portion I8.

It is thought that the invention and its numerous attenclant advantages will be fully understoocl from the foregoing description, and it is obvious tliat numerous changes may be macle in the form, construction and arrangement of the severa-l parts without departing from the spirit er scope of the invention, 01 sacrificing any of it5 attendant advantages, the form herein disclosed being a preferred embodiment for the purpose of illustrating the invention.

Tlle invention is hereby claimed as -followsz 1. An anode comprising a member providing a cavity having a wall of material substantially transparent to electrons and a metal in liquid condition in said cavity and forming an electren target behind saiol wall.

2. An anode comprising a member provicling a cavity having a wall portion of beryllium, and a metal in liquid condition in said cavity and forming an eleetron target behind said. wall.

3. An anode comprising a tuloular conduit member having a wall of material substantially transparent t .electrons, and means to circulate a metal in liquid condition in said vtuloular member in position forming an electron target behincl said wall.

4. An anode comprising a tubular conduit member oi' circular sectional shape having a 1wall cf material substantially transparent to elentrons, and means to circulate a metal in liquid condition in said tubular member in position ferming an electron target behind said. wall.

5. An anode comprising a tubular conduit member of rectangular sectional shape having a wall of material substantially transparent 120 electrons and 1neans to circulate a meta1 in liquid condition in said tubular member in position forming an electron target behind said Wall.

6. An anode comprising a tubular conduit member of elliptical sectional shape having a Wall of material substantially transparent to .electrons, and means to circulate a metal in liquid conditlon in said tubular member in position forming an electron target behind said Wall.

7. A.n anode comprising a member providing a eavity having a Wall of material substantially transparent to electrons, a metal in liquid condition in said cavity ancl forming an electron target behind said. Wall, cooling means remote from said anode, and means forming metal cir culating conduits interconnected with said eavity and with said cooling means ior the circulation of liquid metal to and from the cooling means through said cavity.

8. An anode comprising a container having a wall material substantially transparent to electrens anal means to circulate metal in liquid cendition centinuously througn said container to provide a body ;of liquid metal behind said wall in position to serveas a target for electrons deliv ered through said all.-

9. An anodeqomprising a qontainer embody- Ing a relativezly thin Wall portion of berylliuni and means to deliver metal in liquid condition continuously behind said Wall portion in position to serve as a target for electrons delivered through said Wall portion.

10. An anode comprising a container embodying a wal1 of beryllium, liquid cooling means remote from said container, and means circulate metal in liquid condition irom said cooling means continuously through said container and back to said cooling means to provide a body 0f liquid rnetal behind said wall in position to serve as a target for electrons delivered through said wall.

l1. An anode eomprising a metal member providing a cavity having an open end therein, a relatively thin plate of metal transparent to electrons sealed at its edges in said opening, and means to circulate a liquid metal medium cantinuously in said cavity and behind Sa'id plate in positien to serve as a target for electrons delivered through said plate.

12. An anode comprising a metal member providing a cavity having an open end therein, a relatively thin plate cf beryllium sealed at its edges in said opening, anal rneans so circulate a liquid metal medium continuousiy in said cavity anti behind seid plate in position to serve as a target for electrons delivered througn said plate.

l3. An anode cornprising a container having a wall of material substantially transparent to electrons, means to circulate metal in liquid condition eentinu-ously through said container to proviole a body cf liquid metal behind said Wall in positio-n to serve as an electron target, and auxiliary cooiing means for circulating a cooling; fiuid in heat exchange relationship With said container, to cool tne same and tne 'quid metal circulating therein.

14. An X-my tube enflnodying a cooperating anode and cathode eneloserl in a sealed envelope, said anode comprising a member providing a c avity having a wall o1 material substantially transparent to electrons and a metal in liquid condition in said cavity and forming an electron target behind said wall.

15. An X-ray tube emnodying a cooperating anode and cathocle enclcsed in a sealed envelope. said anode comprising a member providing a cavity having a Wall of material substantially transparent to eleetrens, cooling means, and means to circulate a metal in liquid condition to ancl from seid cooling means anal through eaid cavity in position forming an electron target behind said Wall.

16. An X-ray tube e1nb-ed3 ing a cooperating anode and cathode enelose in a sealed envelope, said anode eomprising a member provicling a cavity having a Wall of beryllium, and a metal in liquid condition in said cavity in position providing an electron target behnd said wall.

l'l. An X-ray tu'oe embodying a cooperating anode and cathode enclosed in a sealed envelope, said anode comprising a tubular conduit mernber having a Wall o1 material substantially transparent to electrons, and means to circulate a 1netal in liquid condition in said tueular member in position forming an electron target behind said Wall.

18. An X-ray tube emoodying a cooperating anode anal cathode enclosed. in a sealed envelope, said anode comprising a tubular conduit memher of circular sectional shape having a wall of -material substantially transparent to electrons andmeans to circulate a metal in liquid 9 condition in said tubular member in position forming an electron target behind said wall.

19. An X-ray tube embodying a cooperating anode and cathode enclosed in a sealed envelope, said anode comprising a tubular conduit memher of rectangular sectional shape having a wall of material substantially transparent 150 electrons, and means 120 circulate a metal in liquid condition in said tubular member in position forming an electron target behind said wall.

20. An X-ray tube embodying a cooperating anode and cathode enclosed in a sealed envelope, said anode comprising a tubular conduit memher of elliptical sectional shape having a Wall of material substantially transparent so electrons, and means to circulate a metal in liquid condition in said tubular mem-ber in position forming an eleetron target behind said wall.

21. An X-ray tube embodying a cooperating anode and cathode enclosed in a sealed envelope, said anode comprising a meoal structure providing a cavity, anal a pool of metal in liquid condition in said eavity in position forming an anode target, and means to circulate a cooling fiuid in heat exchange relationship with said structure and the liquid metal in said cavity.

22. An X-ray tube embodying a cooperating anode anal cathode enclosed in a sealed envelope, said anode comprising a container having a wall of material substantially transparent 120 electrons and means to circulate metal in liquid coudition continuously through said container to provide a body of liquid metal behind said wall in position to serve as a target for electrons delivered thrcugh said wall.

23. An X-ray tube embodying a cooperating anode and cathode enclosed in a sealed envelope, said anode comprising a container having a wall of beryllium, liquid cooling means outwardly cf said envelope, and means to circulate metal in liquid condition continuously from said cooling means through said container and back 120 the cooling means, whereby to provide a. body oi liquid metal behind said Wall in position to serve as a target for electrons delivered through said wall.

24. An X-ray tube embodying a cooperating anode and cathode enclosed in a sealed envelope, said anode comprising a container embodying a relatively thin Wall portion of beryllium and means deliver metal in liquid eondition comtinuously behind said wall portion in position to serve as a target for electrons delivered through said wall portion.

25. An X-ray tube embodying a cooperating anode and cathode enclosed in a sealed envelope, said anode ccmprising a metal member providing a cavity having an open end therein, a relatively thin platze of metal transparent to electrons sealed at its edges in said opening, and means to circulate a liquid metal medium continuously in said cavity and behind said platze in position to serve as a target for electrons delivered through said platze.

MICHAEL J. ZUNICK. HOWARD W. GOODRICK.

References Cited in the file 0f this patent UNITED STATES PATENTS Number Name Date 1182291 Meikle May 9, 1916 1,226383 Robinson May 15, 1917 1,554,'720 Ferguson Sept. 22, 1925 1685928 Morrison Oct. 2, 1928 1712032 Donle May 7, 1929 1938946 Wantz Dec. 12, 1933 2333842 Cascio et a1. Nov. 9, 1943 2459199 Stutsman Jan. 18, 1949

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