US1210678A - Thermionic amplifier. - Google Patents

Description

A. McL. NICOLSON.

THERMIONIC AMPLIFIER.

APPLICATION FILED MAY 19, m5.

Patented Jan. 2,1917. F/g 2 SHEETSSHEETI mvenfor A/Iy [alaialela flma I I l I I I as? W M Alexander NH em A/fco/son.

A. McL. NICOLSON.

THERMIONIC AMPLIFIER.

APPLICATION FILED MAYIQ, I915.

Patented Jan. 2, 1917.

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ALEXANDER MOLEAN NICOLSON, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGN- MENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented an. 2, 1917.

Application filed may 19,1915. Serial No. 29,077.

-fiers, and more particularly to an improved organization of electrodes for the purpose of producing a large output therefrom.

In a copending application, Serial No. 21,918, I have described the advantages to be derived from the use of a so-called equipotential cathode in a thermionic amplifier, that is, a cathode surface, all parts of which are at the same potential with respect to the anode. v

This invention provides for rendering such a cathode surface active by electronic bombardment from another cathode.

It further provides for the employment of a series of such cathode surfaces of successively increasing electron-emitting capacity, in an arrangement for increasing the volume of the cathode stream, each cathode surface being rendered active by bombardment from the preceding cathode of the series.

The invention further provides for the association of such a series of cathodes with one or more input electrodes whereby the magnitude of such a cathode stream may be varied at any stage of its amplification in accordance with variations in a relatively feeble input energy which it is desired to amplify.

For a more complete understanding of the invention, reference may be had to the accompanying drawings in which- Figure 1 represents a simple thermionic repeater arrangement employing an equ1-. potential cathode rendered active by thermionic bombardment, Fig. v2 glves a fragmentary view of a modification of the arrangement of Fig. 1; Fig. 3 represents an arrangement for the amplification of energies in which a plurality of inputelectrodes are employed for the purpose of increasing the variations in magnitude of the thermionic stream; and Fig. 4 shows in fragmentary detail a mechanical arrangenperi t of the electrodes used in the system 0 .3.

Re erring to Fig. 1, 10 is the customary highly evacuated vessel inclosing an anode 11, a grid or input electrode 12, equipotential cathode 13 and auxiliary cathode .or filament 1 1. The cathode 14 may be of tungsten or of platinum suitably coated with a thermionically active material, such as a mixture of strontium and barium oXids, and when heated to incandescence by battery 15 emits a stream of electrons which will bombard the cathode 13 by virtue of the fact that cathode 13 is maintained positive with respect to filament 14 by means of battery 16. Cathode 13 is preferably made from thin sheet metal, such as platinum or tungsten, and has a thermionically active coating applied to the side away from the filament 14, which produces the bombarding electronic stream. The cathode 13 is heated by this bombardment and becomes electronically active, and by virtue of the larger active surface and energy imparted to the system by battery 16, the volume of its electronic emissions will be much greater than that of the filament 14. It is thus seen that the arrangement of two cathodes here employed provides an effective means for amplifying the volume of the cathode emissions and thus increasing the energy output of the tube. If desired, a still further increase in the electronic emissions may be obtained by using a plurality of equipotential cathode surfaces of successively increasing electron-emitting capacity, each of which is made positive with respect to the preceding one of the series and rendered active by bombardment therefrom. A convenient arrangement for accomplishing this result is shown in Fig. 2, in which the electrode elements are in the form of concentrically arranged cylinders having their external surfaces coated with active material. Each of the equipotential cathodes 13, 13*, 13 and 13 receives a bombardment from the 'cathode surface which it incloses, batteries 16, 16, 16 and 16 bei provided to keep each succeeding cath d e positive withrespect to the preceding cathode.

Where currents of relatively low periodicities are to be amplified the modification illustrated in Fig. 3 may be used. In this case an additional input electrode 17 is employed in parallel with electrode 12 and closely associated with the filament 14. T1118 arrangement operates to increase the varia-' tion of the space current caused by the input electromotive force impressed through transformer 18, an increase in the volume of the thermionic stream being occasioned by the employment of an intermediate bombarded cathode 13. The operation is some what as follows: If we consider the input electromotive force to be such as to make the electrode 17 momentarily positive, it is well known that there will result an increase in the space current flowing to the cathode 18, which, in this case, serves as an anode with respect to the -filament 1-1. The thermionic stream emanating from filament 11 bombards cathode 13 and causes it to deliver to anode 11 an electronic stream of increased volume. The arrangement described is thus seen to be productive of current variations of large amplitude in the output transformer 22. An inductive resistance 20 is employed in series with cathode 13 to prevent the leak of the alternating current impulses from cathode 18 to the output circuit, which circuit includes battery 21 and the output transformer The additional electrode 17 may conveniently be in the form of a wire, as shown in Fig. 1, and may be supported in close proximity to the filament 14 by quartz or glass beads 19 into which both the filament 14 and Wire 17 are fused, care being taken, of course, to keep the two out of electrical contact with each other.

IV hat is claimed is:

1. A thermionic amplifier having two cathode surfaces, one of which is rendered electronically active from bombardment by an electronic stream emanating from the other.

2. A thermionic amplifier having two cathode surfaces, one of which is render d electronically acti e from bombardment by a thermionic stream emanating from the other.

3. In a thermionic amplifier, a. series of cathodes of successively increasing electronemitting capacity, each of said cathodes being rendered electronically-active by bombardment from the next preceding cathode of the series;

.4. In a thermionic amplifier, a. series of cathodes of successively increasing electron emitting capacity, each of said cathodes being rendered electronically active by bombardment from the next preceding cathodeof the series, and an input circuit including an input electrode and one of said cathodes for varying the electronic emissions from said cathode.

5. In a thermionic amplifier, a series of cathodes of successively increasing electronemitting capacity, all but one of said cathodes being rendered electronically active by bombardment, and an input circuit including a plurality of input electrodes and a like number of said cathodes for varying the electronic emissions from said cathodes.

6. In a thermionic amplifier, a plurality of cathodes of successively increasing electron-emitting capacities, and means for maintaining each of said cathodes positive with respect to the preceding cathode of the series.

7. In a thermionic amplifier, a series of cathode surfaces of successively increasing electron-emitting capacities, means for maintaining a flow of space currentbetween each cathode and the next succeeding cathode, and an input electrode adjacent one of said cathodes for varying said space current.

In witness whereof, I hereunto subscribe my name this 18th day of May A. D., 1915.

ALEXANDER MCLEAN NIGOLSON.

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