US2242100A

US2242100A - Getter for x-ray generators

Info

Publication number: US2242100A
Application number: US275877A
Authority: US
Inventors: Zed J Atlee
Original assignee: General Electric X Ray Corp
Current assignee: General Electric X Ray Corp
Priority date: 1939-05-26
Filing date: 1939-05-26
Publication date: 1941-05-13
Anticipated expiration: 1958-05-13

Description

May 13, 194-1. z J ATLEE 2,242,100

GETTER FOR X-RAY GENERATORS Filed May 26, 1939 INVENT OR.

Zea l ffllee' W ATTORNEY-5 Patented May 13, 1941 GETTER FOR X-RAY GENERATORS Zed J. Atlee, Elmhurst, 111., assignor to General Electric X-Ray Corporation, Chicago, 111., a cor poration of New York Application May 26, 1939, Serial No. 275,877

4 Claims. (Cl.

My invention relates in general to X-ray generators, and has more particular reference to the provision of means to facilitate the conditionin of the generator for operation after the same has been fabricated.

An important object of the present invention K is to provide getter means in an X-ray generator for conditioning the same for operation.

Another important object is to provide an X- ray generator comprising cooperating anode and cathode means enclosed in a sealed envelope, the getter being disposed in the envelope in a pocket formed therein remote from the active portions of the anode and cathode means, whereby the actuation of the getter may not impair or'contaminate the anode and cathode means.

Another important object is to form and arrange the getter so that the forces generated in flashing the same will be directed into an encathode means.

Another important object is to provide getter means for X-ray generators comprising a material holder of improved form to direct the flash anode and cathode elements; a further object being to provide a mounting for supporting the getter holder on one of the active elements of the X-ray generator, the holder being formed from'the anode and cathode means, as in a pocket formed in the envelope of the X-ray generator.

Another important object resides in using a getter material characterized by a reluctance the material preferably comprising barium and/or aluminum or other suitable non-migratory material having a high melting point, where by the end products of the flash may be localized innocuously in the remote envelope pocket in which the getter means is preferably mounted.

The foregoing and numerous other important objects, advantages and inherent functions of the invention will become apparent as the same is velope pocket and away from the'anode and 1 products away from the active portions of the to support the holder element in position remote to migrate in the envelope upon flashing therein, T

more fully understood from the following descrip- 5 along line 2-2 in Figure 1, showing the details of the getter means illustrated in Figure l;

' Figure 3 is a sectional View taken longitudinally through the end of an X-ray generator to illustrate a modified form of getter means and the manner of mounting the same in accordance with the present invention; and

Figures 4 and 5 are sectional views taken substantially along the lines 4-4 in Figure 3 and lines 5-5 in Figures 2 and 4, respectively.

To illustrate my invention, I have shown on the drawing an X-ray generator comprising a cathode II and an anode in spaced-apart relationship and in position to cooperate to cause the anode to function as a source of X-rays when energized by electronic action set up by the operation of the cathode. The anode and cathode are enclosed in a preferably glass envelope l5, being sealed in the envelope at the opposite ends thereof. The envelope, as shown on the drawing, comprises a central enlarged portion l 9 formed at its opposite ends with sleeve-like extensions 2!. The outer ends of the extensions may be turned inwardly to form reentrant sleeve portions 23 on said envelope, and the active elements of the X-ray generator may be mounted on said reentrant sleeve portion and sealed thereon, as at H. Although in Figure 1 I have shown only the cathode seal, it will be understood that the anode likewise may be sealed in the opposite end of the envelope in like or other suitable or preferred fashion.

The cathode H is preferably provided with a dependent skirt portion 25 extending therefrom within the envelope extension 2| to enclose and form a shield for the seal I! in order to prevent impingement on said seal of stray electrons liberated within the envelope, thereby preventing the seal from becoming deteriorated through electron impact.

It will be noted that the envelope extension 2| and the reentrant sleeve portion 23 form therebetween an annular space 21 into which theterminal edges of the skirt portion 25 extend. The envelope walls also may be offset, as at 29, so that the terminal portions of said annular space 21 are of restricted character forming a pocket 3|.-

After the parts II and I3 have been assembled within the envelope 15, the device is evacuated by connecting the envelope with exhaust means, such as a molecular pump, the connection being made as at 33.

In conditioning the generator for operation, it is necessary to remove not only all of the gas that is present within the envelope, but also the occluded gas contained in the anode and cathode and in the material of the envelope itself. If such occluded gases are not removed, they will gradually be released Within the envelope and impair the exhausted condition at which the generator is designed to operate.

The removal of the occluded gases is accomplished by baking or otherwise heat treating the entire device at a temperature short of the softening point of the glass, while keeping the exhaust means in operation, and also by heating the electrodes to a high temperature, either by electron bombardment or by placing the electrodes in a magnetic field fluctuating at frequencies of the order of radio frequency.

After all of the occluded gases and other impurities have thus been removed from the envelope, the exhaust connection may be sealed off, as at 34. I propose, as a final step, to volatilize or flash a small quantity of a suitable getter 35 within the envelope after the envelope has been sealed, in order to form end products of the getter material and any remaining gases, the end products being innocuous and remaining in the envelope.

As a getter material, I prefer to employ a metal, such as ban'um and/or aluminum, and preferably a mixture of the named metals, the getter material having a high melting point and being characterized by a tendency to remain immobile in the envelope after being flashed.

The getter material 35 is preferably used in finely-divided or powdered form and is supported in a holder 31 which in turn is mounted on a support 39 anchored on one of the active elements of the X-ray generator and preferably on the skirt 25 in position such that the holder 3'! is disposed in the restricted pocket 3| in a position as far removed from the active portions of the anode and cathode as is possible.

The support '39 preferably comprises a sheet metal strip suitably secured, as at 5|, on the skirt and having an offset portion 53 terminating in a curled mounting forming a seat to which the holder 31 may be secured.

The support 39 and the holder 31 are so formed, arranged and mounted that the flange 49 substantially closes and forms a barrier between the space 3| and the remaining portions of the envelope in which the active elements H and l3 of the generator are disposed. The holder 3i, moreover, is disposed in the chamber 3| in position such that the flash products will impinge directly upon the facing surface of the envelope portions which define the side of the chamber 3| where said flash products will adhere as a film indicated in dotted lines at 59. The envelope surfaces defining the pocket 3|, being at the end of the envelope, comprise a cool region on which flash products will readily condense to form the film 59.

The operation of the getter may be accomplished in any suitable or convenient fashion,

as by heating the .getter by inductive action to a temperature above the flash point of the getter material. After flashing, the flash products will remain in filmed form, as at 59, in substantially immobile condition and ordinarily will not migrate nor deleteriously aifect the operation of the elements I and I3.

The getter material 35 is preferably arranged within a tubular wire SI of electrical conducting material, one side of which wire is of reduced section, as at 53. This wire may then be supported in any suitable or convenient fashion on the support 39, in position such that the portion of reduced section 63 faces into the pocket 3|. The getter may be flashed by heating the same in its enclosing sheath 6| inductively, whereupon the flash products will be expelled outwardly through the Wall of reduced section 63, to form the deposit 58 on the facing pocketforming walls of the envelope.

Preferably, however, the getter is flashed by providing for the heating of the same by passage of an electrical current through the sheath or container GI, and this may be accomplished by anchoring the member 6| at one end on the support 39, and by providing conductor means 65 electrically connecting the other end of the member 6| with a source of getter flashing electrical power outwardly of the envelope IS, the conductor means 65 being electrically connected witha seal conductor 61 extending outwardly of the envelope through the seal 69. This seal 69 also contains a ground conductor for electrically connecting the body of the electrode I including the skirt portion 25, outwardly of the envelope; and by utilizing this ground conductor and the conductor 61, electrical current for flashing the getter may be delivered within the envelope from a suitable external power source.

In certain electrode constructions the getter" flashing conductor 61 may comprise one of the cathode conductors, and in such constructions it is not necessary to provide an additional seal conductor for the sole purpose of flashing the getter, but the cathode lead may be used for that purpose.

As shown in Figures 1 and 2, the member 6| may be supported on a guard 13 similar to the guard 3'! and having a flange 19 adapted to serve as a guard and prevent the flash products of the getter material from passing out of the pocket 3|, the support member 13 having a plate portion 1| upon Which the member 6| is mounted, the member 6| being electrically connected at one end on the plate H and arranged in a spiral coil, as shown.

Means may be provided, if necessary, to support the several coils and insulate the same from the plate H, as by means of glass beads or predestals formed on the plate 1| to support the member 6| in place, the free end of the member 6| being connected with the conductor 65.

As shown in Figures 3 and 4, the member 6| is arranged as a substantially annular loop in the annular pocket 3|, with the wall portion 83 facing the bottom of the annular pocket, one end of the loop being supported on the member 39 and the other being connected with the conductor means 65. When mounted in such fashion, it is not essential to provide a guard similar to the flange 49 and 79. However, an annular plate 89 forming a guard may be provided, desired, and anchored on the member 39 to extend in the pocket 3|, and the member 6| containing the getter material may be supported on the annular guard 89 in position between said guard and the bottom of the pocket 3|.

The member 6| in such case may be electrically connected at one end on the guard 89 and thus grounded on the electrode body, and the other end of the member 6| may be electrically connected, as shown, with the flash conductor 65. The intermediate portions of the member 6| may be mechanically secured on and insulated from the guard 89 as by means of glass mountings or other suitable supporting and insulating means on the guard 89.

Flashing of the getter, however, substantially reduces the amount of occluded gas remaining in the envelope and permits the provision of an X-ray generator in which, occluded gases will not be liberated during the operation of the tube. Consequently, tubes flashed in accordance with my present invention will operate satisfactorily for extended periods without becoming soft.

It is thought that the invention and numerous of its attendant advantages will be understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing any of its attendant advantages, the form herein described being a preferred embodiment for the purpose of illustrating the invention.

The invention is hereby claimed as follows:

1. An X-ray generator comprising co -operating electrodes enclosed in an envelope, means on said envelope forming a pocket having a wall providing a cool zone at an end of the envelope, getter means comprising a tubular sheath form ing a holder for getter material, said sheath having a wall of reduced sectional thickness along a side thereof and being arranged in a spiral pancake coil, and means for supporting said sheath in said pocket with the wall portions of reduced section facing the pocket-forming wall.

2. An X-ray generator comprising co-operating electrodes enclosed in an envelope, means on said envelope forming an annular pocket having a wall providing a cool zone at an end of the envelope, getter means comprising a tubular sheath forming a holder for getter material, said sheath having a wall of reduced sectional thickness along a side thereof and being arranged as a loop extending in the annular pocket, and means for supporting said sheath in said pocket with the wall portions of reduced section facing the bottom of the pocket.

3. An X-ray generator comprising co-operating electrodes enclosed in an envelope, means on said envelope forming a pocket having a wall providing a cool zone at an end of the envelope, getter means comprising a tubular sheath forming a holder for getter material, said sheath having a wall of reduced sectional thickness along a side thereof, means to support said sheath on one of said electrodes, and a guard arranged in the pocket between the sheath and the electrode on which the sheath is mounted.

4. An X-ray generator comprising co-operating electrodes enclosed in an envelope, means on said envelope forming a pocket having a wall providing a cool zone at an end of the envelope, getter means comprising a tubular sheath forming a holder for getter material, said sheath having a wall of reduced sectional thickness along a side thereof, a support electrically connected with one of said electrodes, means to electrically connect a portion of said sheath on said support and to insulate the remaining portions of said sheath from said support, and means sealed in said envelope for electrically connecting a portion of said sheath remote from said support connected portion with a source of getter flashing power outwardly of said envelope.

ZED J. A'I'LEE.