US3153738A - Cooling system for anode sections separated by cylindrical X-ray window - Google Patents

Description

Oct. 20, 1964 3,153,738

G. W. STEEN COOLING SYSTEM FOR ANODE SECTIONS SEPARATED Bi CYLINDRICAL X-RAY WINDOW Filed April 26, 1961 INVEN TOR.

GOTTFRID W. STEEN AGENT United States Patent F 3,153,738 COOLING SYSTEM FDR ANODE ECT10NS SEEP- ARATED BY CYLINDRICAL X-RAY WINDOW Gottfrid W. Steen, Stamford, Conn, assignor to The Machlett Laboratories, Incorporated, Springdale, Conn.,

a corporation of Connecticut Filed Apr. 26, 1961, Ser. No. 105,607 9 Claims. (Cl. 313-22) This invention relates to X-ray tubes and has particular reference to X-ray tubes constructed and arranged to emit X-radiation throughout an angle of 360 around the anode. More specifically, this invention has reference to a novel anode structure for X-ray tubes which permits tubes made with beryllium windows to operate at higher temperatures than previously were believed practical, and to novel means for air cooling the heated portions of such tubes, and particularly of the window which forms a part of the anode structure.

In X-ray tubes constructed in accordance with the prior art, maximum operating temperatures must be carefully controlled to avoid damage to or destruction of the tubes as a result of overheating. Such damage may occur in the term of cracking or crazing of the windows. Tubes which are provided with circumferential X-ray transparent windows, for the emission of X-radiation throughout an angle of 360 around the tube, are difiicult to cool because of their particular structure which requires cooling throughout the circumference of the tube instead of in smaller areas such as in tubes where relatively small disclike windows are used.

Many tubes are cooled by locating at least a portion of the anode externally of the tube Where it may be subjected to the flow of liquid coolant. This, however, gen erally involves circulation means interposed in the field of radiation, or restriction of cooling to only the ends of the windows, or would entail cumbersome arrangements outside of the effective radiation field to provide liquid cooling to the portions of the anode nearest the target as well as to the attached window. Usually, the circulation of cool air over heated portions of air-cooled tubes with beryllium windows is not enough to maintain the parts at satisfactorily low temperatures. Therefore, attempts have been made to solve these problems by forming the annular windows of materials such as copper or nickel which, however, still require means for circulating liquid coolant over the surfaces of the windows, impairing the X-ray transmission characteristics. These materials also are known to be relatively easily workable and windows of these materials can be soldered into their supporting structures by known techniques, compared to beryllium which is not easily workable or readily soldered. Furthermore, regardless of the metal used, it has generally been found necessary to locate the windows as far as possible from the targets to subject them to as little secondary electron bombardment as possible and to remove them from the hottest areas of the tubes.

Accordingly, it is a primary object of this invention to provide a novel anode structure for X-ray tubes which permits the tubes to operate efficiently at relatively high temperatures.

Another object is to provide an X-ray tube with a novel anode structure which permits efiicient air cooling of the anode and particularly of the window thereof.

Another object is to provide an anode and window structure with means for circulating cool air over the window and thence into a cooling radiator.

A further object is to provide efficient air cooling means for the anode of an X-ray tube which permits the use of relatively small diameter annular windows which are located relatively close to the source of X-radiation.

3,153,738 Pajtentedflct. 20, 1964 ice V A still further object is to provide an anode with cooling means of the above character which is entirely outside the effective field of X-ra-diation.

These and other objects are accomplished by the provision, in an X-ray tube, of an anode which comprises a tubular metal extension of the envelope of the tube, the extension being disposed in longitudinal alignment with the electron emitting cathode enclosed within the envelope. The major portion of the extension is exposed externally and at its outer end is sealed to one end of a slecvelike window which is in turn sealed at its outer end to an anode block which carries the ray generating target on its inner surface within and relatively closely encircled by the window. The window is of relatively small diameter to closely encircle the target whereby the annular beam of X-radiation is enabled to cover a wider area. The window is made of beryllium for best transmission of X-rays and may be relatively short in an axial direction to impart ruggedness .to the structure. Hard soldering of the window to the supporting parts of the anode is accomplished by a method such as shown and described in US. Patent No. 2,770,033, Zarth, assigned to the same assignee as the present invention, or other efiicient beryllium soldering method, and permits operation of the tube at temperatures only limited by the melting temperatures of the solders used to braze other seals of joints in the structure remote from the window, by the temperatures at which the anode may be heated without gas evolution, or by maximum tube ratings as determined by target temperatures. Furthermore, novel means is provided for circulating cool air over the window and adjacent parts of the anode, which air is directed into a finned radiator carried by the anode block for dissipation of heat from the block. Although the tube may be operated for short periods of time at higher than normal temperatures without cooling means, such air circulation enables the anode, including the window, to be maintained at temperatures low enough to prevent damage by heat when the tube is operated for longer periods of time.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawing wherein the figure is an elevational view of the anode end portion of an X-ray tube embodying the invention, showing the anode in axial section.

Referring more particularly to the drawing, the X-ray tube 119 comprises a generally tubular envelope structure including a portion 11, of glass or other selected material, which encloses an electron emitting cathode, not shown. The envelope also includes a tubular anode support sleeve 12 disposed in coaxial alignment with portion 11 and vacuum-sealed thereto at one end by known metal-to-glass sealing methods.

One end of a tubular anode body 13 extends within the support 12 and has a circumferential flange 14 which is sealed to the other end of the sleeve 12 by a suitable metal sealing ring 15. The inner wall of anode body 13 is hollow to provide a tunnel through which electrons flow from the cathode.

The outer end of the body 13 is provided with an annular groove in which is located one end of a hollow cylindrical sleeve-like window 16 of X-ray transparent or translucent material such as beryllium or other selected material having low X-ray absorbing characteristics. The end of the window 16 is sealed within a bezel 17 which is in turn sealed to anode body 13 by suitable hard solder means, and is similarly sealed at its opposite end by bezel 18 and hard solder within an annular groove formed in the adjacent surface of an anode block 19 of copper or other material having high thermal conductivity.

The inner end of the anode block 19 has a target 20 embedded in its surface within the encircling window 16.

The target is preferably formed of tungsten or other selected material and is in position to receive the stream of electrons passing through the anode body 13 from the cathode, in the normal operation of a tube of this type, and to generate a copious supply of X-rays in response to such electron bombardment. The X-rays will be emitted in all directions from the target surface and, since the window is substantially transparent to X-radiation, will irradiate a circumferential area extending throughout an angle of 360 around the tube.

In accordance with this invention, the diameter of the window 16 is relatively small which permits a relatively wide X-ray beam to be emitted by the tube, compared to a beam in a tube having a larger diameter Window of the same length. The end of the window is very close to the target; that is, the thermal path between the target and window is very short compared to known prior art strucures. Ruggedness and good thermal conductivity are imparted to the structure by making the window relatively thick and short in the axial direction without impairing its transparency to X-rays because compared to other materials beryllium has excellent transparency to X-rays.

In such operation of the tube, the generation of heat at the target causes resultant heating of the anode block 19 and window 16. In order to dissipate such heat, the anode block carries an encircling radiator 21 which is provided for the purpose of dissipating heat by the circulation of cool air within the spaced fins thereof. To accomplish this, the radiator comprises a hollow cylinder 22 which is mounted in firm encompassing relation to the anode block 19, and the longitudinally extending fins 23 thereof are sealed along one edge directly to the cylinder in a spaced radially-projecting array.

Thus, heat within the block 19 is transmitted by conductivity directly through cylinder 22 to the fins 23. The rear or outer end of the block 19 is bored or otherwise recessed as at 24 to reduce the mass of the anode while still providing an adequate heat flow to the radiator.

In order to adequately cool the window and the adjacent portions of the anode body 13 and the block 19, means is provided for circulating cool air over the surfaces of these elements. The anode body 13 is provided with a portion having a reduced outer diameter which forms a circumferential recess 25. A groove is provided in the body 13 adjacent the bottom of recess 25, and in the groove is secured one end of a tubular jacket or collar 26 which encircles the recess 25 and extends toward the anode block 19 in spaced relation with body 13. A connection 27 is fixed in the jacket 26 in communication with recess 25 and provides means whereby cool air may be forced under pressure into the recess whereupon the jacket 26 will direct the flow of air upwardly where it will be expelled over the surface of the window 16 and then into the radiator 21. In this way the anode body 13, the window 16, and the adjacent end of anode block 19 are all subjected to the flow of the circulating cool air.

The free end of the jacket 26 terminates at or below the end of the anode body and thus is not located in the field of radiation where it might intercept usable X-rays emitted by the target 20.

In the illustrated structure, the window 16 is of substantially smaller diameter than the adjoining anode body 13 and block 19. Thus, there is formed an external circumferential recess at the window which in some cases might tend to trap and prevent circulation of air, consequently permitting the window to assume undesirably high temperatures. In order to overcome this problem and to provide for continuous circulation of cool air over the outer surface of the window, the adjacent end of the anode block 19 is provided with an enlarged annular rim or flange 28 which preferably has an outer diameter substantially equal to the outer diameter of the radiator cylinder 22. Cylinder 22 is of a length to extend over the major portion of anode block 19 but terminates at rim 28 as shown. However, fins 23 project beyond the 4! cylinder and overlie the rim 2:; and actually preferably extend to the plane of the target indicated by line P. Furthermore, the periphery of rim 23 is provided with a beveled surface 29 which deflects circulating cool air passing over the window into the downwardly projecting portions of the fins 23, as indicated by arrows in the drawing, whereby the temperature of the window and adjacent portions of body 13 and block 19 are effectively lowered.

The fins 23, by being made to extend beyond the end of the cylinder 22 into the vicinity of the window, aid in effecting efiicient cooling of the window without being interposed in the field of radiation. By terminating in the plane of the target, the fins do not interfere with the X- radiation in any way.

From the foregoing it will be apparent that a novel X-ray tube anode structure has been provided which embodies a circumferential window encircling and in relatively close proximity to the X-ray generating target to provide a large field of X-radiation, which anode has a novel air cooling means whereby the tube may be operated at relatively high temperatures without becoming damaged by heat. Modifications may be made, however, in the structure shown and described, without departing from the spirit of the invention as expressed in the accompanying claims.

I claim:

1. An X-ray tube anode comprising a tubular anode body, a sleevelike window sealed at one end to one end of the anode body with its interior in communication with the interior of the anode body, an anode block sealed to the opposite end of the window, a target on the end of the anode block, a finned radiator closely encircling the anode block, and means for directing circulating air from within the anode body to the vicinity of the window then into the radiator.

2. An X-ray tube anode structure comprising a tubular anode body, a sleevelike window sealed at one end to one end of the anode body with its interior in communication with the interior of the anode body, an anode block sealed to the opposite end of the window, a target on the end of the anode block within and closely encircled by the window, a finned radiator encircling the anode block, a jacket encircling the end of the anode body adjacent the target and in spaced relation thereto, and means for directing cool air into the jacket for circulation over the anode body, the jacket terminating in an open end adjacent the window whereby the circulating cool air is directed over the surface of the window and into the radiator.

3. An X-ray tube anode structure comprising a tubular anode body, a sleevelike window sealed at one end to one end of the anode body with its interior in communication with the interior of the anode body, an anode block sealed to the opposite end of the window, the outer diameters of the anode block and anode body being greater than the outer diameter of the window whereby a circumferential recess is provided in the outer wall of the anode structure at the window, a target on the end of the anode block within the window, a finned radiator encircling the anode block, and means for directing circulating air from the anode body into the vicinity of the annular recess and then into the radiator.

4. An X-ray tube anode structure comprising a tubular anode body, a sleevelike window sealed at one end to one end of the anode body with its interior in communication with the interior of the anode body, an anode block sealed at its inner end to the opposite end of the window, the outer diameter of the inner end of the anode block being greater than the outer diameter of the window whereby an annular recess is provided in the outer wall of the anode structure at the window, a target on the inner end of the anode block within the window, the surface of the target defining a target plane, a radiator encircling the anode block and comprising a support cylinder mounted closely upon the anode block and of a length terminating short of the inner end of the anode block, a plurality of fins disposed in a radially spaced array on the outer surface of the cylinder and extending longitudinally thereof in the direction of the anode body beyond the cylinder and overlying the portion of the anode block between the cylinder and the target plane, said portion of the anode block having its surface shaped to deflect circulating air from the recess at the window into the radiator.

5. An X-ray tube anode structure as set forth in claim 4 wherein the inner peripheral edge of said portion of the anode block has a bevel throughout its circumference.

6. An X-ray tube anode structure comprising a tubular anode body, an annular circumferential X-ray transparent window, and an anode block sealed together in that order in coaxial alignment, the outer dameters of the anode body and block being greater than the outer diameter of the window whereby a circumferential recess is provided in the structure in a position to receive air intended for cooling the window, a target in the inner end of the anode block and closely encircled by the window, a finned radiator encircling the anode block, and means within the anode body for directing air from the recess into the radiator.

7. An X-ray tube anode structure comprising a tubular anode body, an annular X-ray transparent window, and an anode block sealed together in that order in coaxial alignment, the outer diameters of the anode body and block being greater than the outer diameter of the window whereby a circumeferntial recess is provided in the structure in a position to receive air intended for cooling the window, a target in the inner end of the anode block and closely encircled by the window, the surface of the target defining a target plane, and a radiator encircling the anode block and comprising a support cylinder mounted closely upon the anode block and of a length terminating short of the inner end of the anode block, and a plurality of fins disposed in a radially spaced array on the outer surface of the cylinder and extending longitudinally thereof in the direction of the anode body beyond the cylinder and overlying the portion of the anode block between the cylinder and the target plane, said portion of the anode block having its surface shaped to deflect circulating air from the recess at the window into the radiator.

8. An X-ray tube anode structure as set forth in claim 7 wherein the inner peripheral edge of the anode block has a bevel throughout its circumference.

9. An X-ray tube comprising an envelope including a bulb having an open end, and an anode supported by the bulb and comprising a tubular anode body sealed adjacent one end to said open end of the bulb, a sleevelike window sealed at one end to the opposite end of the anode body with its interior in communication with the interior of the anode body, an anode block sealed to the opposite end of the window, a target on the end of the anode block and closely encircled by the adjacent end of the window, a finned radiator encircling the anode block, and means for directing circulating air from within the anode body over the window and then into the radiator.

References Cited in the file of this patent UNITED STATES PATENTS 1,665,638 Morrison Apr. 10, 1928 2,222,549 Verhoeif Nov. 19, 1940 2,324,034 Skene July 13, 1943 2,909,686 Zunick Oct. 20, 1959 3,069,590 Walter et al Dec. 18, 1962 FOREIGN PATENTS 574,758 Great Britain Jan. 18, 1946

Claims (1)

1. AN X-RAY TUBE ANODE COMPRISING A TUBULAR ANODE BODY, A SLEEVELIKE WINDOW SEALED AT ONE END TO ONE END OF THE ANODE BODY WITH ITS INTERIOR IN COMMUNICATION WITH THE INTERIOR OF THE ANODE BODY, AN ANODE BLOCK SEALED TO THE OPPOSITE END OF THE WINDOW, A TARGET ON THE END OF THE ANODE BLOCK, A FINNED RADIATOR CLOSELY ENCIRCLING THE ANODE BLOCK, AND MEANS FOR DIRECTING CIRCULATING AIR FROM WITHIN THE ANODE BODY TO THE VICINITY OF THE WINDOW THEN INTO THE RADIATOR.

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