US2656489A

US2656489A - Electron discharge device and processing thereof

Info

Publication number: US2656489A
Application number: US221034A
Authority: US
Inventors: Gaylon T Ford
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1951-04-14
Filing date: 1951-04-14
Publication date: 1953-10-20
Anticipated expiration: 1970-10-20

Description

Oct. 20, 1953 G. T. FORD 2,656,489

ELECTRON DISCHARGE DEVICE AND PROCESSING THEREOF Filed April 14, 1951 lNVENTOR a. 7? FORD ATTORNEY Ii the view being taken just below the upper insulator; and

Fig. 3 is a schematic representation of one activating and decontaminating circuit employable in accordance with this invention.

Referring now to the drawing, the electron discharge device illustrated in Fig. 1 comprises an envelope Hi having an exhaust tabulation H and leads I2 in the base thereof. The electrode structure is situated within the envelope between two insulators M, as of mica, and includes a flat hollow cathode l5 having a heater element i3 located therein, a control grid 16 mounted by side rods H, a screen grid l8 mounted by-side rods l9, and an anode 20. A shield 2| is advantageously located on each insulator l4 between the side rods I1 and I9 and the remainder of the tube.

Two decontaminator electrodes 23 are directly attached to the ends of two leads [2 extending through the lower of the insulators l4 and are Dositioned on each side of the cathode and grid structure. The decontaminator electrodes 23 have coated on their surfaces a gettering material 24 such as zirconium, thorium, a thorium-caesium composition known commercially as Ceto, or other gettering material as is known in the art. The particular materia1 chosen will depend on the configuration of the electron discharge device and the temperatures attained by the device and the decontaminator electrodes, particularly during the activation process.

After the elements have been assembled in the device the envelope I0 is exhausted and the metallic elements within it are out-gassed, as is known in the art. Generally this is accomplished by heating the anode and the other elements by high frequency induction. In the illustrative embodiment of this invention disclosed, the two decontaminator electrodes would be parallel to the direction of the induced field if it is applied normal to the major anode surfaces, as is generally done. To provide an improved coupling with the high frequency induction field, the two decontaminator electrodes 23 may be joined by straps adjacent the insulators M. The temperature attained by the decontaminator electrodes 23 during this process should be sufiioient to outgas the metallic electrodes but insuflicient to cause the gettering material 24 positioned on the electrodes to remove any substantial amounts of impurities from the atmosphere, as it is more desirable that contaminants and impurities evolved during the out-gassing be exhausted from the envelope.

The temperature to be attained by the decontaminator electrodes during this out-gassing process will also depend on whether the gettering material itself needs to be activated prior to the aging or activation process. Thus, if zirconium hydride is coated onto the decontaminator electrodes '23, it must be heated to break the hydride down to metallic zirconium.

Another method of attaining the desired heating of the decontaminator electrodes that may advantageously be employed in the illustrative embodiment of the invention disclosed is to have the anode a completely enclosed member thereby serving as an oven to raise the temperature of the decontaminator electrodes 23. It is thus apparent that numerous variations may be made by those skilled in the art in the particular structure disclosed in order to attain the desired correlation between the temperature of the decontaminator electrodes during the out-gasd sing and the exhausting of the device and the particular gettering material coated thereon.

Following the exhausting of the device it is sealed and is ready to be aged or activated. One such activation circuit in accordance with this invention is shown in Fig. 3. As there shown, the anode 20 and screen electrode it are held positive with respect to the cathode I5 by

voltage supplies

25 and 26, respectively. If desired, the anode and screen electrode could be electrically tied together to a single voltage supply. The control electrode l6 may also be held positive with respect to the cathode 15 by a voltage supply 21. The decontaminator electrodes 23, however, are connected to the negative side of a voltage supply 28 so as to be negative with respect to the cathode [5.

During the aging process, positive ions produced by electron collison or by bombardment. of the elements are collected by the negative decontaminator electrodes and then held by the getter material thereon. The natura1 afiinity that the getter material has for the impurities or contaminants present in the atmosphere of the envelope and generated from the elements during the aging process is thus accentuated and increased because of the negative potential applied to the decontaminator electrodes whereby the positive ion impurities are more easily attracted to the getter material.

Subsequently, during normal operation of the device the decontaminator electrodes are advantageously operated at cathode potential, as by being directly connected to the cathode lead, or by being connected together in the external circuit. As the decontaminator electrodes 23 are outside of the electron paths and are at cathode potential, they do not enter into the operation of the device.

Additionally, the electron bombardment of the decontaminator electrodes by electrons impinging thereon is negligible so that the impurities trapped by the getter material thereon are not released to the atmosphere of the device during its operation.

While this invention has been disclosed as incorporated in a particular tetrode and with the getter material on decontaminator electrodes of a particular configuration, it is, of course, apparent that the invention is capable of employment in devices including different numbers of electrodes and of different configuration. Similarly, the invention is not limited to the getter material on the decontaminator electrodes as shown, for the getter material and the decontaminator electrodes could be of various forms to which the negative potential could be applied during the aging process. It is, therefore, to be understood that the above-described arrangements are illustrative of the principles of the invention and that numerous other arrangements could be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. The combination of a cathode, at least one electrode cooperating with said cathode and defining discharge means therewith, a gettering material adjacent said discharge means, and means applying a potential to said gettering material negative with respect to said cathode during the aging of said cathode whereby positive ion impurities are attracted to said gettering material.

2. In combination with an electron discharge device comprising an envelope, a cathode within said envelope, an electrode adjacent said cathode, and a gettering material in said envelope, means creating an electron discharge between said cathode and said electrode to age said cathode, and means applying a potential to said gettering material negative to said cathode during the aging of said cathode.

3. The combination of a cathode, at least one electrode cooperating with said cathode and defining discharge means therewith, a second electrode adjacent said cathode, a coating of getter material on said second electrode, and means applying a potential negative with respect to said cathode to said second electrode during the aging of said cathode.

4. The combination of a cathode, at least one electrode cooperating with said cathode and defining a discharge path therewith, a decontaminator electrode having a coating of getter material thereon adjacent said cathode but removed from said path, and means applying a potential negative with respect to said cathode to said decontaminator electrode during the aging of said cathode.

5. In the fabrication of electron discharge devices, the method of decontaminating an electron discharge device which comprises positioning getter material within said device, maintaining a discharge within said device, and applying a negative potential to said getter material while maintaining said discharge.

6. In the fabrication of electron discharge devices, the method of decontaminating an electron discharge device which comprises positioning a getter material within said device, evacuating said device, maintaining a discharge within said device between the cathode and anode thereof, and applying a negative potential to said getter material while maintaining said discharge.

7. In the fabrication of electron discharge devices, the steps comprising positioning a getter material within the device, evacuating said device, applying a potential to the getter material negative with respect to the cathode within said device during the activation of said cathode, and connecting said getter material electrically to said cathode subsequent to the activation of said cathode.

8. The method of decontaminating an electron discharge device which comprises coating a getter material on an auxiliary electrode, positioning said auxiliary electrode within said device removed from the discharge path between the cathode and anode of said device, maintaining a, discharge between said cathode and anode to activate said cathode, and applying a potential to said auxiliary electrode negative with respect to said cathode while maintaining said discharge.

GAYLON T. FORD.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,412,302 Spencer Dec. 10, 1946 2,445,993 Beggs July 22, 1948 2,547,200 Dorgelo Apr. 3, 1951 FOREIGN PATENTS Number Country Date 221,625 Great Britain Sept. 18, 1924