US2136105A - Electron discharge device - Google Patents

Description

NOV.8, 1938. B T I 2,136,105

ELECTRON DISCHARGE DEVICE Filed Sept. 3, 1956 TIME V POTf/VIML INVENTOR QUNTHER JOBS! PUTENT/AL I Y i RNEY n K I] 341411 ANODE l L Patented Nov. 8, 1938 aren't ELECTRON DISCHARGE DEVICE Giinther J obst,

Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlcse Telegraphic in. b. 11., Berlin, Germany,

tion of Germany a corpora- Application September 3, 1936, Serial No. 99,231

In Germany 1 Claim.

My invention relates to electron discharge de' vices intended for the production of oscillations and more particularly to improvements in devices of the negative resistance type in which 5 with high anode potentials less current is taken by the anode than with smaller anode potentials.

The principal object of my invention is to provide an electron discharge device which can be used for amplification, rectification, mixing difl' ferent frequencies or for producing oscillations, and particularly to provide an improved type of such device having a negative resistance characteristic.

The novel features which I believe to be char-- acteristic of my invention are set forth with particularity in the appended claims, but the in vention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a diagrammatic representation of an electron discharge device. embodying my invention, and a circuit therefor; Figure 2 is a graphical representation of the operation of the device shown in Figure 1 under different conditions of anode voltage; Figure 3 shows a circuit arrangement embodying my invention; Figure 4 is a graphical representation of anode voltage con ditions during operation of the circuit embodying my invention and shown in Figure 5; Figure 5 shows another circuit arrangement embodying my invention; and Figure 6 is a diagrammatic representation of a modification of an electron discharge device embodying my invention.

By extending the field of application of the arrangement to very short waves where the transit time of the electrons is of importance with respect to the length of the period of the action, the more general formulation of above conditions applies namely that on the electrons that are taken upby anode the work (t) ALVA ds f be 45 nifies the elementary quantum, Vac the anode direct potential,

o O as E8t -55 controlled, which fulfills the condition above ex- September 18, 1935 pressed, or on secondary electrons, ions or space charge effects, or in the Barkhausen-Kura case on a sorting out of the elects in the present case the variable penetrability of the anode with respect to the electrons as a function of the anode potential or electron speed is the means relied upon for fulfilling the above condition.

There is produced by the thus presupposed variable penetrability relationship between potential in which there is first an increase of the internal resistance of the discharge plane with increased penetrability and with further inproperties of the anode a anode current and anode crease of penetrability of the anode as a function of a rising anode potential, a reversal of the sign of this resistance or a decrease. The latter action takes place when the internal resistance is already high due to additional means such as a screen grid between the cathode and anode or when working on the saturation point of the cathode filament. In case the resistance of the cathode-anode discharge path is already statically or dynamically negative due to some cause or other, for example controlling the grid in suitable phase, the means provided for the penetrability variation as a function of anode potential can be considered as adding these properties and result for instance in a reduction of the absolute value of the negative resistance or in an improvement of the efficiency.

It has been known since the experiments of Lenard that thin foils of a metal with small atomic weight for electrodes are the more permeable the higher the electron speed. In this manner the prior art was successful in having electrons with high potential leave the vessel through metallic foils that formed the closure of a vacuum vessel against air. The so-called Lenard windows nevertheless have still considerable thickness in order to be able to withstand the difference in air pressure between vacuum and atmosphere so that they have a proper permeability only for electrons of very high speed. If however, as can be done with the means available at the present state of the art, optically transparent foils are used as anodes inside the tube, eliminating a mechanical stress in above sense, the penetration of the anode is achieved at relatively small anode potentials or electron speeds. (See for instance German pattent 587,113, which likewise proposes the use of such a thin metallic foil, however for the entirely different purpose of releasing secondary elec trons by the penetrating primary electrons.) During the passage through the anode the electrons are subjected to an average velocity loss which results in a heating of the anode, and with smaller anode potentials or lesser electron speeds the passage of the electrons through the anode is prevented. The greater the anode potential or speed of the electrons the greater the probability of the electrons passing through the anode and the smaller therefore the anode current. The electrons passing through the anode are caught by an electrode disposed behind the anode: or the electrons may be reflected in the case of very short waves. In the first case this electrode may be a solid sheet or dense net and is impressed with a slightly positive potential, in the case of short waves it may have a negative potential.

In accordance with my invention I reproduce the atomic field conditions existing in the interior of metal foil electrodes by means of an arrangement of coarser type. Just as within the atoms the electron paths are more curved and finally are bound in the atomic bond, the smaller the speed of the shot-through electron, in the same way the electron paths are curved by means of the arrangement shown diagrammatically in Figure 1 in which the anode A consists of a pair of interposed electrodes for instance one of bars ill and the other of plates or slats II in alternating succession. Between these electrodes there is applied a constant potential difference and the higher potential is applied to the larger electrode or to the electrode comprising the plates. With higher anode potentials and hence greater electron speeds in the neighborhood of the anode the electrons are deflected relatively only a little by this potential difference and fly through the anode. For the case where the anode potential or electron speed in the vicinity of anode is small, the electrons are deflected much more strongly and so that most of the electrons move toward the more positive part of the anode. An electrode S positioned between the cathode K and the anode A is positively biased with respect to the cathode for accelerating the electrons from the cathode to the anode.

In Figure 2a the path of the electrons from the cathode K through the anode A to the plate P is designated by the lines provided with the arrow heads. It will be observed that under these conditions of high plate voltage that the electrons pass through the anode without being deflected to any considerable extent. In the case shown in 2b with the lower anode voltage applied, the electrons are deflected from their path and are caught and retained principally by the plate portions of the anode electrode.

In the circuit shown in Figure 3 an oscillating circuit comprising an inductance l2 and capacity I 3 is connected between the cathode K and the anode A. The fixed potential difierence between the two electrodes forming the anode may be established by a resistance and condenser combination M or by a suitable source of voltage in the form of a battery.

A type of feedback arrangement for producing oscillations is shown in the circuit in Figure 5. The plate electrode portion of the anode is connected to an intermediate point on the inductance 15 which is bridged by a capacity I6 to provide a tuned circuit. A battery I! is connected between the tuned circuit and the rod electrode portion of the anode so that the rod portion is at a lower potential. The voltage relationship on the rod portion of the anode and the plate portion of the anode is shown in Figure 4, which represents the voltage relationship with respect to time during operation of the tube. The lower fixed potential E1 represented by the lower horizontal line is that applied to the rod electrode portion of the anode, the AC potential existing on this portion of the electrode being represented by the curve whose axis is the fixed potential E1 applied to this electrode. The higher positive potential E2 is applied to the plate electrode portion of the anode and the superimposed AC potential is shown as the curve whose axis is the horizontal line representing E2. While a battery i1 is shown in Figure 5, it is of course possible to substitute a resistor and condenser combination such as shown in [4 of Figure 3.

While in the arrangements above the more or less large penetrability of the anode is the result of the field relations inside the anode proper. I may use an arrangement where the combination of elements produces electron shadows and hence electron beams, for instance diaphragms used in cooperation with geometrically adapted constructions of the anode to furnish the desired effect. It is for instance a well known fact that in larger tubes the grid struts shadows on the anode whereby it may be directly observed that the points of anode impinged upon glow, while the ones not or less impinged upon appear dark. According to the potential impressed on the grid causing the shadow and on the anode, these light and shadow points have different locations on the anode. By perforating or cutting out those portions of the anode which are primarily impinged upon with higher potentials I can produce the desired result. Factors to be considered for the geometric development of the tube depend upon whether the electron distribution on the anode is produced by a shadowthrowing electrode of fixed potential or of alternating potential coupled with the anode potential. Particularly in the latter case the optimum perforation or cutting out with respect to efiiciency may be made only for definite operating conditions with respect to the amplitudes of anode and grid alternating potentials as well as the direct potentials. The experimental basis for the placing of these perforations is obtained for example with the aid of a model tube of the type here in question which may be photographed for the momentary values of the potential combination. From these pictures are obtained the points to be perforated or cut out for a certain purpose of application. It may be pointed out that the perforations must not be-of such size that thereby considerable field variations, as compared to the field of the non-perforated or cut out anode, may occur at remoter distances from the cathode. The purpose in view would thus not be gained for the electron path would be deflected too early in the direction of the solid parts of anode.

A further embodiment of my invention is shown in Figure 6. The electrons pass through a diaphragm S having an aperture and to which is applied a positive potential with a certain velocity given by this potential and are deflected by the field of the anode disposed parallel to the path of the electrons passing through the diaphragm. If the anode potential is large, the deflection is greater, and the electrons fly through the perforated part A in the vicinity of the slot and land on the pick-up surface P located in the rear thereof. With smaller anode potentials the deflection of the electrons by the transverse field is less and the electrons land accordingly on the non-perforated parts of the anode A.

and wires form electron It may be added that the pick-up electrode last referred to may also be impressed with an alternating potential of su'table phase It is thus for instance possible to modify the circuits in Figures 3, 5 and 6 in such a manner that the pick-up electrode is impressed with a potential having a phase rotation of 180 with respect to the anode potential. But is must not in turn influence the control in the vicinity and inside the anode. This and the passage of secondary electrons from the one to the other electrode may be prevented by a grid of suitable permeability and impressed with fixed potential and positioned as a screen between P and A.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it

will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claim.

What I claim as new is:

An electron discharge device having a cathode and an anode permeable to electrons, said anode comprising a pair of interposed electrodes of different size elements electrically insulated from each other and a second electrode adjacent the anode for receiving the electrons which pass through said anode, and a grid disposed between the cathode and the anode.

GiiN'rHER JOBST.

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