US2411515A - Electron discharge device - Google Patents

Description

Nov. 26, 1946.

C. E. BRIGHAM ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 1 Filed April 17, 1943 IN VEN TOR. CFC/L E. BRIG/4AM AITORNEY 2 Sheets-Sheet 2 INVENTOR. CECIL 5. lama/114M ATTORNEY Nov. 26, 1946- c. E. BRIGHAM ELECTRON DISCHARGE DEVICE Flled Aprll 17, 1945 Patented Nov. 26, 1946 ELECTRON DISCHARGE DEVICE Cecil E. Brigham, East Orange, N. J., assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware l ipplication April 17, 1943, Serial No. 483,378 In Great Britain December 31, 1940 2 Claims. (Cl. 25027.5)

'This invention relates to electron discharge apparatus and more particularly to electronicdetectors and amplifiers and to electronic oscillators operable at ultra-high frequencies.

The invention comprises an electron discharge device comprising a cathode and an anode, and interposed. therebetween an accelerating elec trode, all of the said electrodes being of linear form and disposed in parallel relation; the said cathode being of circular cross-section and designed to be non-emitting over an area facing the said accelerating electrode and symmetrically disposed thereto, whereby the proportion of electrons captured by the said accelerating electrode is reduced, the device being operated in the manner to be described below.

According to another feature of the invention, the cathode may instead be given a cross-section consisting of a figure with two straight sides facing the said accelerating electrode and including an angle which is less than 180 degrees in the side away from the said accelerating electrode.

According to another feature of the invention, a cathode of either type may be used in an electron discharge device for generating oscillations comprising a cathode, an accelerating electrode and a plurality of output electrodes, for reducing the proportion of electrons captured by the accelerating electrode, when the device is operated as described below.

The invention will be more clearly understood by referring to the following detailed description and to the drawings, in which Fig. 1 is a diagram of a type of electron dis-- charge tube to which the invention is applicable, showing the electron paths in the usual construction and operation of such tube; v

Fig. 2 is a similar view showing the electron paths when the tube is provided with a cathode having an uncoated surface portion opposite the accelerator electrode;

Fig. 3 is a similar view in which the cathode is rectangular;

Fig. 4 is a similar view in which the cathode has intersecting faces in alignment with the ac:- celerator electrode arranged at an angle of 150;

Fig. 5 is a view similar to Fig. 4. with the oathode faces at an angle of 130; and

Fig. 6 is a similar view showing a diamond shaped cathode with said faces at an angle of 60.

In the Bruce Patents Nos. 2,254,264 and 2,254,-

265 there is disclosed a detector or amplifying ator electrode and a control electrode, all such electrodes being disposed in parallel relation. A linear auxiliary electrode is also positioned on the side of the anode remote from the cathode and all the previously-mentioned electrodes are encompassed by a cylindrical shield electrode. With the auxiliary and shield electrodes at cathode potential and the anode electrode at a relatively high positive potential with respect to the cathode, the accelerator electrode at a less positive potential, and the control electrode at a slightly negative potential, electrons emanating from the cathode are accelerated towards the anode by the accelerating electrode and a concentration of electrons occurs in the immediate vicinity of the anode whereby 'a dense charge region and potential minimum is set up in proximity tothe control electrode and anode. This space charge region is augmented by electrons which miss the anode in their original flight and come under the influence of the retarding field of the auxiliary electrode and shield. Such electrons revolve or spiral about the anode before being collected by it, and the control electrode can, therefore, exercise effective control upon this region sothat a very high transconductance is obtainable.

Figures 1 to 6 are diagrams illustrating the results of experiments made on a rubber sheet model with arrangements of the kind described above. In these figures, C is the cathode, AC the accelerator electrode, CG the control electrode, A the anode, AE the auxiliary electrode,

- S'the cylindrical shield and E the envelope. The

electron paths are indicated by broken lines.

It has been found that a large proportion of the electrons emitted from the cathode are absorbed by the accelerator electrode, resulting in excessive accelerator current. This condition must necessarily be very ineflicient and will affect the characteristics of the tube in regard to its slope and noise etc. due to inherent excessive division of current. Experiments have indicated that, as shown in Fig. l electrons emitted over an arc of 100-120 of the cathode surface immediately opposite the accelerator electrode are absorbed by the latter and never reach the anode.

It has now been found that an improvement may be effected by leaving uncoated a portion of the cathode surface immediately opposite the accelerator electrode over a substantial area, an angle of the order of as shown in Fig. 2, having been found particularly effective.

An even more eflicient arrangement is to employ a cathode of such cross-section that two adjacent flat sides facing the accelerator electrode form an angle of less than 180 on the side remote from the accelerator electrode. It has been found experimentally, however, that the most effective angles lie between 60 and 90. A cathode of rectangular or rhombic cross-section may be conveniently employed with a diagonal of the rectangle or rhombus in line with the line passing through the centres of the linear electrodes.

Fig. 3 shows a rectangular cathode, while Figs, 4, 5 and 6 show arrangements in which the sides of the cathode form angles of 150, 130 and 60 respectively.

Fig. 3 shows clearly that with a cathode of square cross-section the flow of electrons to the accelerator electrode is considerably reduced and that a greater proportion of the electrons emitted by the cathode reach the anode. Tests on sample valves having circular cathodes showed an anode current of 800 micro-amperes and an accelerator electrode current of 2.25 milliamperes for given conditions. Similar valves employing a square cathode showed under similar conditions an anode current of 1.0 milliampere and an accelerator current of only 510 microamperes. Tests also indicated that the slope characteristics of the valve are improved by use of a square cathode construction.

The abovementioned Bruce patents also disclose a tube having linear electrodes and intended for use as an oscillator. In a tube of this type which is shown in Fig. 7 the central linear electrode l is maintained at a positive potential relative to the cathode c, and a plurality of similar output electrodes 2, -3 operated substantially at cathode potential are provided in place of the anode electrode and accelerator electrode of the type of tube previously described. By the use of the improved cathode constructions described above the conduction currents to the central positive electrode I are reduced and the efiiciency of the tube as a generator of high frequency energy is increased.

What is claimed is:

1. An electron discharge device comprising a cathode and an anode, and interposed therebetween an accelerating electrode, all of the said electrodes being of linear form and disposed in parallel relation; the said cathode having two flat intersecting sides facing the said accelerating electrode and at an angle to each other which is less than 180 degrees on the side away from the said accelerating electrode, and symmetrically disposed thereto, whereby the proportion of the electrons captured by the said accelerating electrode is reduced.

2. An electron discharge device as set forth in claim 1, in which said angle has a value between and CECIL E. BRIGHAM.

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