US2233779A - Electron discharge device - Google Patents

Description

March 4, 1941. K. FRITZ ELECTRON DISCHARGE DEVICE 3 Sheets-Sheet 1 Filed Nov. 2'?, 1936 9; Xxx xxxxxxxxx i @L f N y C L L L@ WM l. C L 3/, L@ @2% ln lv nl'. L T il... I" U z- .IIJ ...Il

INVENTOR KARL FRITZ ATTORNEY March 4, 1941. K, FRI-rz 2,233,779

ELECTRON DISCHARGE DEVICE INVENTOR KARL FRITZ IBY ATTORNEY March 4, 1941. K, FRlTZ 2,233,779

ELECTRON DISCHARGE DEVICE Filed Nov. 27, 19'56 3 Sheets-Sheet 3 WAN l A l O f l dangnaaaannn Patented Mar. 4, 1941 UNITED sTATEs PATENT OFFICE ELECTRON DISCHARGE DEVICE Germany Application November 27, 1936, Serial No. 112,940 In Germany November 30, 1935 14 Claims. (Cl. Z50-36) The present invention relates to short wave tube arrangements intended primarily for attaining high oscillation energies at favorable eiliciency.

A great many short wave tube devices are already known some of which operate with a control of the emission current, and others with a control of the distribution of the emission current emanating from the cathode with constant magnitude, and in which the transit time of an electron is about the same as the time of an oscillation of the produced frequency. The efficiency with which short waves have hitherto been produced is relatively low. In retarding field circuits such efficiency is of the order of approximately 15%, or in magnetron circuits with oscillations of the first order it has the value of approximately In some cases it has been possible to attain an efficiency of approximately 50% with oscillations of higher order and with the use of very strong magnetic fields.

The object of the present invention is to increase the efficiency beyond the usual values and especially beyond the value of In fact the given value of about 50% represents a limit value which cannot be exceeded by way of further experimental development on the basis of the usual conceptions known in the art for the oscillation performance in oscillations with travel periods. It will be explained hereinafter why the value of approximately 50% must be the limit for a continuous further development along the known lines.

The present invention does not deal with instructions which serve for the Asolution of the problems encountered in the short wave apparatus hitherto employed, but departs from obsolete laws, and shows principally novel ways which require, in order to be followed with success, novel tubes and circuits.

The short wave apparatus according to the invention, and having tubes with one or several cathodes or sources of emission and more particularly several electrodes ppsitively biased and in which the cathode is preferably not included in the circuit of the electrodes carrying alternating current, is characterized by such arrangement of the electrodes and choice of operating conditions that the electrons which, as regards the excitation oi.' oscillations, enter with proper phase relation the alternating field between the electrodes and deliver their energy. absorbed from the electrical direct acceleration field, as completely as possible and especially in several stages to an alternating field; for example, that of the cooperating electrodes, so that they impinge on an electrode or group of electrodes at a velocity that is low as compared with the incidental voltage effective between `the cathode or source of emission and the output electrode.

Tubes will preferably be used whose electrodes are at different distances from the cathode, and the arrangement of the electrodes and choice of the operating conditions will be such that a part of the electrodes (useful electrodes) primarily those which carry only alternating voltages, and no direct current or a fraction of the total emission current, and that another part of the electrodes (absorption electrodes) serves primarily only for receiving electrons without carrying an appreciable alternating voltage, and at least some having the frequency to be generated.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawings in which Figures 1 and 2 are diagrams showing electron movement in magnetic and electrical fields, Figure 3 is a diagrammatic showing of one form of electron discharge device embodying my invention, Figure 4 is a diagrammatic showing of another form of electron discharge device embodying my invention, Figures 5a, 5b and 5c are diagrammatic views of another form of electron discharge device embodying my invention, Figure 6 is a diagrammatic view of a push-pull type of electron discharge tube and circuit made according to my invention, Figures 7, 8, 9, 10 and 11 are diagrammatic showings of modifications of electron discharge devices embodying my invention.

The tube schematically shown in Figure 1 comprises substantially two parallel plates Ai and A2. It is assumed that between the plates there exists a transverse electrical field having constant strength and direction, and a magnetic field of constant magnitude and direction whose lines of force extend at right angles to the plane of the drawings. The projections of the lines of force i. e. the limits of the effective zone of the magnetic field H are indicated by small crosses, It is also assumed that the strength of the magnetic field is such that the radius of curvature of the electron paths is smaller than half of the interplate distance d. With` these assumptions, an electron at K' and having an initial velocity vo with any direction, will move in a cycloid shaped course either towards the left or towards the right depending on the direction of the magnetic field. 'I'his is due to the fact that the path of the electron prescribing a circle will be expanded when the electron approaches the plate havingy the high (positive) potential A1, while the said path undergoes a decrease of its curvature when approaching the plate having the lower potential, as compared with a circular course which the electron would prescribe where both plates have the same potential. These considerations are intended only to show that the electron without the use of a special acceleration electrode, can perform a progressing movement vm in the field at right angles to the magnetic and electrical lines of force, i. e. along the plates, if only an electrical transversal ileld exists.

Figure 2 shows schematically a similar tube. Contrary to the preceding example in addition to the constant transverse direct field, a transverse electrical field with alternating direction and intensity is assumed between the plates A1 and Aa. The electrons are assumed to originate at an emission source K located for instance in the centerplane between the plates, i. e. they pass from this side into the plate system and move towards an electrode N at the right side extending at right angie to the aforementioned center plane.

Figure 3 shows in principle a tube suited for carrying out the idea of the invention. The cathode K is backed by auxiliary electrode Z for concentrating the electron current, the A. C. carrying useful tubular electrodes A1 to Ac whose dimensions along the electron paths gradually decrease or increase in one direction and are positioned between cathode K and the absorption electrode or anode N. The electrode A1, the d-c voltage on which does not change with respect to the cathode K, serves as an accelerating electrode for the electrons moving from the cathode to the anode N. Adjacent electrodes are connected with each other by identical oscillatory circuits L and C, On their travel from the cathode K to the absorption electrode N the electrons must remain within each anode cage for a period equal to approximately the duration of one half oscillation cycle. The polaritles indicated at the connection points of the oscillatory inductance L relate to the superimposed alternating potential and are meant for electrons which happen to be at the end of the useful electrodes A1, A3 and As for instance. 'I'he length of the anode cages, or the distance between the center normal, or perpendicular center plane of an electrode and the center normal of the following electrode must be matched with the velocity of the electrons and the frequency to be generated. At the transit of the electrons from one cage to another one, the alternating field must just have the maximum. Thus the first of the electrons with respect to the cages or electrodes are properly controlled in accordance with the oscillations of the connected circuits. The electron accelerated by the direct bias potential thus loses in stages its velocity, and reaches the electrode N with zero velocity in the most favorable case. l

The operation of the form shown in Figure 3 may be described somewhat as follows: 'I'he electrode A1 being connected to the cathode K through the battery which for practical purposes has no impedance is at radio frequency ground potential with respect to the cathode. Hence A1 serves only to accelerate the electrons from the cathode K to the electrode A1. Assuming no voltages on any of the tubular electrodes A1 to Aa, a space charge will be formed around the cathode K when energized. If voltage is now applied to all electrodes including the collector electrode N. a beam of electrons will be accelerated toward the collector electrode N, through the tubular electrodes, electrode A1 serving merely as an accelerating electrode as is done in conventional cathode ray tubes. As the tip of the beam approaches electrode A1 since A1 is not grounded for radio frequency the beam induces on this electrode a negative charge, the charge increasing as the tip of the beam approaches closer to this electrode. Due to the fact that connected between A1 and A2 is an oscillating circuit comprising inductance L and capacity C, current will begin to ow into the condenser to charge the condenser since there will bea difference of potential between the electrodes A1 and A2. Inasmuch as the oscillating circuit has inductance, the condenser will continue to be charged so as to increase the negative potential on A1 even after the beam enters the electrode and exerts no further influence on the electrode. As a result of the increase in a negative direction of voltage on A2, electrons in the beam approaching A2 from A1 will be successively decreased in speed to a greater and greater extent so that when maximum negative voltage is applied to electrode A1, electrons approaching electrode A: will have the least velocity. Electrons within the electrode however continue to pass through the electrode Az at the velocity they had upon entering this electrode. This means that within the electrode Az at any given instant the electrons are advancing through the electrode at different velocities. The length of the electrodes and the oscillating frequency of the oscillating circuits is such that the rst group of electrons inl the tip of the beam reaches the end of the electrode A2 a half cycle after they entered so that the electrode A: has again returned to zero radio frequency potential, But due to the oscillatory-circuit, the condenser discharges carrying the electrode A2 into the positive half cycle. 'This means that the voltage on electrode A1 is beginning its negative half cycle as the first group of electrons approaches electrode A3. These electrons are slowed down giving up energy to the electrode A3. In the meantime as the voltage on Az increases in a positive direction the electrons approaching from A1 are accelerated. These accelerated electrons overtake the slower moving electrons within Az forming a second dense group of electrons projected to As. This results in velocity modulation, so called, oi electrons in the beam passing throughv the electrode Az. The second group of electrons which has been bunched by velocity modulation in A1 approaches A3 as Az begins its negative half cycle, the ilrst group of electrons having emerged from A1 as it started its positive cycle will approach A4 as it starts its negative cycle, the second group of electrons approaching As a half cycle later. It will thus be apparent that groups of electrons approach each electrode at such time that the electrode is passing through its negative half cycle. Thus energy is extracted successively by the successive electrodes maintaining the oscillating circuits energized, the energy initially being delivered to the electrons from the voltage source connected between A1 and the cathode.

Another theory which may be advanced is that the emission from the cathode is not constant so that as the beams is projected through successive electrodes by the accelerating electrode A1 the variations in emission which may be slight may be such that they will induce voltages in electrode A: which build up, the variations being responsible for shocking the circuit connected between Ai and Az into operation in the same manner that the tip of the beam as it approached electrode A: in the first case set the circuit into oscillation. Either theory may apply. However such tubes have been operated successfully in the laboratory and it is believed that one or the other of the two theories advanced above is explanatory of the action which takes place.

The method of producing oscillations described with reference to Figure 3, can in practice be carried out in an essentially simple manner, utilizing at the same time the magnetron principle. There is hereby utilized the physical fact that an electron moving along a rotational path in a magnetic field, has an angular velocity depending only on the magnetic held, and not on the voltage through which it passes. Hence if an electron rotates about a center point, its frequency of rotation and thus its reaction upon an oscillatory circuit as regards frequency, remains constant, while as regards amplitude it is dependent on its energy of movement, i. e. with a given magnetic field (frequency) on the radius of its circle. This is made use of in the following way:

Figure 4 represents a cross section through a rotation-symmetrical structure of a tube using the principle of the tube in Figure 3, with the exception that only two useful electrodes Ai and Az are provided, and this tube contains instead two cathodes Ki and K2. The absorption electrode N is situated at the axis of the system. For the sake of simplification there is omitted from the drawings a magnetic field produced by electromagnetic coll R and whose lines of force extend parallel to the axis of the system, and which in viewing the drawings extend towards the plane of the drawings. Electrons emanating from the cathodes Ki and K: and accelerated by the direct field and entering into the drumshaped discharge space through the slots S1 S'z at irst rotate in a circle with a suitable choice of the magnetic field strength, and electrical bias potentials. Now, if an alternating potential is generated between the two cylinder halves, and if the magnetic field strength is so chosen that the time of rotation of the electrons is justl equal to an oscillation cycle, then at first two principal conditions exist. In one case the electron moves in proper phase from K1. i. e. it just passes with its high velocity through the slot plane S1. if the transverse electrical field between the electrodes Ai and Az opposes its movement. 'I'hus the electron moves upon the electrode A1 negatively excited by the alternating field. In this case it furnishes energy to the outer circuit and slows down its sped of rotation, its path radius becomes smaller since the magnetic field remains constant. The angular velocity of the electron remains practically constant. It repeats its rotation until it has arrived on its spiral path at the absorption electrode N. The electron impinges `approximately with zero velocity, although this electrode N has a high positive potential. This signifies, therefore, that the electron has given up its entire energy received while entering the cylinder, to the alternating eld, i. e. to the oscillation electrodes. The einciency is about 100%. In the extreme case, the absorption electrode N needs not be cooled.

The second case, namely in which the electron enters with improper phase from K: through the slot Sz into the discharge space, therefore moving towards an electrode A positively excited at this moment by the alternating voltage disregarding the positive steady bias potential can be readily visualized. The electron derives additional energy from the alternating field, increasing thereby its velocity of rotation, its path will be widened and it flies towards the electrode A with the highest incidental voltage, and is thus removed from the alternating field. The same principal considerations are obviously also true where a single cathode k only is provided.

In summarizing it is found that importance is to be attached to removing from the region of the electrodes having alternating potential, the electrons which as regards excitation of oscillations leave the original source with improper phase, before they have increased additionally their energy obtained from the electrical direct acceleration field through their deriving of energy from the electrical alternating field.

Below two further measures will be explained furnishing means to cause the electrons leaving the source of emission in improper phase, usefully to contribute to the excitation of oscillations. These measures improve the production of oscillations according to the invention to a very high degree, but they may principally also be employed in other oscillatory arrangements, and for this reason they will be later referred to in order to logically continue the lines of thought so far laid down.

In accordance with the invention, the course of the electrons will furthermore be so influenced that they travel from their source no longer in any voluntary fashion, but proceed in a regulated sequence. On the one hand there exists the possibility of permitting the electron current to leave its source only at such moments that possibly all electrons enter in proper phase into the discharge space surrounded by useful electrodes, so that therefore they are compelled to contribute with an optimum to the excitation of oscillations at proper choice of the other operating conditions. Special auxiliary electrodes disposed in direct proximity of the cathode are suited to carry out this cathode control.

Figure 5a shows the top view of a tube according to the invention containing auxiliary electrodes. The discharge space has the form of the volute type turbine casing. It is limited by four useful electrodes A1. Az, m, and A4 gradually decreasing in size in the direction of the electron flight, and representing sectors of a prismatic hollow body. 'I'he cathode K is located at the circumference of the prism extending parallel to the surface lines of said prism, and surrounded at the outside by a directive semi-cylinder Z which concentrates the electron current up to a certain degree. Between cathode K and the inlet opening into the rst electrode sector A1 one or several perforated auxiliary electrodes G are provided which can take over the function of a pulling and control grid or both. Two oppositely disposed useful electrodes are always connected with each otherby a bent connection member B1; and Bia respectively. An electromagnetic coil R produces the magnetic field. Of course electromagnets could be used for this purpose also. The operating conditions and the dimensions of the electrodes are different and taken parallel to the electron travel path must be so chosen that at the travel of an electron from the center normal (radial center plane) of an electrode to the center normal of the following electrode, the sign of the superimposed alternating fleld is reversed.

An input circuit I is connected between the cathode K vand the grid G properly biased. The focusing electrode Z is biased negatively with respect to the cathode. 'I'he output circuit comprises an inductance L and a capacity C connected to oppositely disposed groups of electrodes Aa. A4 and A1, As. 'I'he voltage supply is represented at Ua. The input voltage has a frequency related to the natural frequency of oscillation of the output circuit such that the modulation of the electrons will cause the output circuit to oscillate at its natural frequency.

Figure 5b shows a side view of the same tube indicating clearly the' arrangement and the position of the side or absorption electrodes N.

Figure 5c likewise shows an elevation of the tube. There is indicated herein the discharge vessel E as well as the electrode connections. The two bent connections B1.: and Bm have an oscillatory circuit L C connected thereto which circuit is positioned preferably outside the discharge vessel E.

However, a control of the electron current with respect to magnitude must not necessarily be relied upon. It is possible to have a current of constant magnitude leaving the source of emission and to distribute this current in different directions in certain time intervals.

Figure 6 is a diagrammatic cross section through a push-pull tube similar to Figure 5. The lines of force of a magnetic eld produced by solenoid R extend parallel to the axis of the system, whichin this case coincides with the cathode K. 'I'hey extend therefore in the same direction in the left and right discharge spaces. It is assumed that the lines of force of the magnetic field pass from the viewer towards the plane of the drawings. The electrons therefore can execute movements only in a right hand rotation. Now in order to be able to control the electron c urrent in time intervals and in the proper direction, leaving the cathode with constant magnitude, which will be the case only in the space charge region, a grid-1ike electrode G'. is connected for instance conductively with the useful electrode Az and another perforated electrode G. is connected capacitively therewith. The useful electrode A"i has connected thereto corresponding pulling and control grids G". and G"|.

The electrons can enter the right hand discharge space through the space charge-or pulling grid G'. only when the control electrode G'. is positive relative to the cathode K. In the same' moment however, the useful electrode A'1 is negative, and the electron moving towards the electrode delivers in the desired manner, a part of its kinetic energy (taken from the direct acoeleration field) to the alternating field. Considering for the same moment the left hand discharge space, it will be found that the grid G". is negative, so that in the direction oi' the incidentally positive electrode A"2 no electrons can enter the left hand discharge space. After one half cycle of the oscillation T/Z the conditions are reversed. Hereby the double frequency appears between the absorption electrodes N' and N". If f necessary, the excitation of this frequency can be enhanced by a special oscillatory circuit L C', or suppressed through capacitive short circuits between the electrodes N and N" and cathode K.

With my invention it is possible to provide any (even number) multiple splitting up of the' useful electrode (anode). This has the advantage that the travel time (time of circular course) of an electron can be greater than the oscillation time for a complete cycle of the produced oscillations. The case is hereby exactly the reverse of that of -the known magnetron principle. The oscillations of higher order are in fact characterized in that the travel time of the electrons is greater than the oscillation cycle, for instance in oscillation of the second order the travel time nr=2r, where 1- is the oscillation time'for a complete cycle. This condition is of greatest importance to practical structures. Assuming equal tube dimensions and wave length, it is possible to employ much weaker magnetic fields, in fact the required strength oi' the magnetic field decreases in proportion to the number of useful electrodes, and there exists no limitation such as in the four place split magnetron in which the cathode is located at the axis of the discharge space.

Furthermore the following advantages are obtainable: When decreasing the alternating voltage of the oscillation, no regions appear in which the oscillations will be disrupted. The amplitude of the oscillations can therefore lbe gradually reduced to relatively low values. In case of low alternating voltages it is only the number of circular paths which increases before the electrons arrive at the anode. This phenomenon can be utilized in an especially favorable manner in modulationand controlor regulation circuits. A further favorable property of the tubes and circuits according to the invention resides in a gentle starting of oscillation which can be of importance especially for purposes vof reception.

If the cathode control is to be dispensed with for any particular reason or in tubes for special purposes of application, there are available to this end two possibilities of utilizing for the excitation of oscillations the electrons departing from their source in any irregular fashion, and also those which move with incorrect phase.

One possibility resides in that the electrons departing from the source with incorrect phase as regards excitation of oscillations, are compelled to undergo a phase reversal or to perform a. phase jump for the purpose of supporting the excitation of oscillations. The jump or reversal of the phase relates to the phase difference existing at the place of the discharge space considered between the periodically oscillating field, and the velocity component of the electron extending parallel to the electrical field.

In the following the manner will be shown in which this phase jump or phase reversal can be carried out in practice. Above it was frequently stated that the electrons moving in improper phase undergo an increase in velocity through deriving of energy from the alternating oscillation field, and that therefore, they impinge on an electrode following a small number of circullar movements, usually following a single circular movement. To this end openings are provided in the useful electrodes adjacent the cathode, and in back thereof further electrodes are arranged at a distance permitting a suitable travel time at the bias potentials employed and the frequency to be produced. The useful electrodes arranged one behind the other are so connected that with respect to the radially adjacent of the applied alternating field following the passage through a perforated electrode has its sign reversed. The placing in series of the electrodes can be extended in any `desired manner.

Figure 'I shows the principle of such electrode system. 'I'he electrode system may also be in twin arrangement (Figure 8) or in the form of a symmetrical cylinder (Figures 9 and l0). This box-like arrangement of electrodes can obviously be carried out in the proper sense in all oscillatory tube circuits to which the travel time of the electrons is of the order oi the time of oscillation for a complete cycle of the produced frequency.

In the arrangements indicated in Figures 7 and 8 the electrons going out from the cathode K go. through an alternating field in such phase that they deliver energy to this alternating field. Since electrons continuously come out of the cathode, only half of the electrons work in the desired way, while the other half come out of the cathode in the wrong phase; that is, they leave the cathode at such a point of time that the result is not a delivery of energy but an absorption of energy from the alternating field. In between, the energy balance will correspondingly be zero. In order now to convert all of the electrons to a delivery of energy, the electrodes of the alternating field are made perforated so that these electrons which absorb energy, that is are faster, go through the electrodes and thereupon come into a neld which is opposed to the first neld. With reference to this field, the electrons are then in the right phase, that is, they deliver energy to` this field. Figures 'l and 8 show very schematically the construction of a tube which makes use of this principle. In front of a cathode K dinerent grid-like electrodes A are arranged which are so connected to an external oscillating circuit that between the succeeding grids there appear alternating fields opposed to one another. The spirals shown in full lines indicate electron paths in which a decrease of the radii of the spirals indicates a delivery of energy of the electrons to the alternating field (right phased electrons) and an increase of the radii of the spirals indicates an absorption of energy (wrong phased electrons). The arrangement is so completed that the cathode is heated and the individual grid electrodes placed at positive potential; for example, all at the same potential or one after the other at increasing potential.

Figure 9 shows a magnetron tube. The electrodes are spaced at equal radial distances. Both electrodes A and A' receive positive bias potential relative to the cathode K. T'he outside electrode has the highest positive bias potential applied thereto. Electromagnetic coil R produces the field. I

Figure 10 shows a retarding ileld tube. It comprises cathode K and concentric apertured electrodes A1, Az, A3 and A4, The distances between the electrodes A1 to A4 become shorter from the inside towards the outside. Electrodes .c

oscillating in equal phase can now 'be connected -with each other and a common oscillatory circuit comprising inductances L and capacities C can be inserted between the two groups. If the mutual capacities of the electrodes which are added, cause a disturbing effect an oscillatory circuit can be inserted always between tw o adjacent electrodes.

Figure 11 shows schematically a tube which -includes all improvements as proposed in this furnishes the magnetic field. The electrons move along a kind of cycloidal helix i. e. along a heli cal path whose radius continuously decreases between the perforated useful electrodes A1 and Az and arrive with a minimum velocity at the absorption electrode N after having delivered their energy to the useful electrodes. In back of the useful electrodes A1 and A: further useful electrodes Ar and An may be arranged which transformthe electrons which entered the discharge space with incorrect phase whereby their radius of the path has undergone an additional increase, into electrons having the correct phase (phase Jump) after the former electrons have passed through the perforated electrod owing to their opposite excitation. The deflecting electrodes Gs which are relied upon to deflect the electron beam issuing from the cathode K are electrically connected for radio frequency voltage and currents to the electrodes Ar and An. The voltages existing on these two electrodes are applied to the deecting electrodes by means of the coupling condensers shown to cause the electron beam to be oscillated at the proper frequency to maintain the tube and its circuit in oscillation.

As regards modulation, demodulation, remote control, and stabilization, obviously all known and suitable methods of electrical or magnetic nature or combinations thereof can be employed with the use of the main electrodes or auxiliary electrodes.

While I have indicated the preferred embodiments of my invention of which I am now aware 4and have also indicated only one specic 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 claims. v

I`claim:

1. An electron discharge device having a cathode for supplying electrons. -an anode for receiving said electrons, .and a plurality of electrodes surrounding the space between said cathode and said anode and adapted to have an alternating potential applied thereto for creating an alternating electric field between said electrodes. means for directing electrons from said cathode through the space surrounded by said electrodes and means for applying a magnetic neld perpendicularly to the direction of travel of said electrons from said cathode to said anode, the magnetic ileld and alternating electric field decreasing the velocity of the electrons from said cathode an alternating potential applied thereto for creating an alternating electric field in said space, an electromagnetic coil for generating a magnetic iield substantially perpendicular to the travel oi' the electrons from the cathode to said anode, said alternating electric field and said magnetic neld causing the velocity of the electrons in their movement from the cathode to the anode to be decreased so that they arrive at the anode at a velocity low compared with the yelocity when leaving said cathode.

3. An electron discharge device having a cathode for supplying electrons and an anode for receiving said electrons, a plurality of electrodes surrounding the space traveled by electrons from the cathode to the anode and adapted to have an alternating potential applied thereto during operation or the tube for creating an alternating electric iield in said space, means for producing an electromagnetic field perpendicular to the travel of electrons from the cathode to the anode and other means for directing the electrons from the cathode into the space surrounded by said plurality of electrodes, the alternating electric field and the electromagnetic ileld induced in said space decreasing the velocity of the electrons in their travel from the cathode to the anode.

4. An electron discharge device having a cathode for supplying electrons .and an anode for receiving said electrons, a plurality oi' arcuate shaped electrodes surrounding the space traveled by the electrons from the cathode to the anode and adapted to have an alternating potential applied theretc for creating an alternating electric eld in said space, means for inducing a magnetic eld perpendicular to the path oi' the electrons in their movement from the cathode to the anode, and other means for directing the electrons from said cathode into said space, said electrons being decelerated in their movement i'rom the cathode to the anode by the alternating electric field and the magnetic eld.

5. An electron discharge device having a cathode for .supplying electrons and an anode for receiving said electrons, a plurality of arcuate shaped electrodes surrounding the space traveled by the electrons from the cathode to the collecting electrode, said anode being centrally positioned with respect to said electrodes, said electrodes being .adapted to have an alternating voltage applied thereto for creating an alternating electric eld in saidspace, means for producing a magnetic ileld perpendicular to the path of the electrons in moving from the cathode to the anode, said electrons traveling in a spiral-like path with decreased velocity in response to the action of said alternating electric field and said magnetic field, and means i'or directing the electrons from said cathode into the space surrounded by said electrodes.

6. An electron discharge device having a cathode for supplying electrons and an anode for receiving said electrons, a plurality oi.' electrodes bounding the space traveled by the electrons from said cathode to said anode and adapted to have .an alternating potential applied thereto, said electrodes having perforated portions near said cathode, electrodes positioned outside of said space and said perforated electrode for receiving electrons passing through said perforated portions, means for inducing a magnetic tleld substantially perpendicular to the travel of electrons from the cathode to the anode, and means for directing electrons into said Space.

7. An electron discharge device having a cathode for supplying electrons, an anode for receiving said electrons, a plurality oi' electrodes surrounding atleast part of the path ci the electrons between said cathodeand said anode and of successively decreasing length, means for applying an alternating potential to said electrodes for creating an alternating electric field between said electrodes, means for applying a positive potential with respect to the cathode to said plurality ot electrodes and means for directing electrons from said cathode through the space surrounded by said electrodes, said alternating electric field causing a decrease in the velocity of electrons moving from the cathode to the anode.

8. An electron discharge device having an electron emitting cathode and an anode for receiving the electrons, a plurality of electrodes surrounding the space traveled by the electrons from the cathode to the anode, circuit means connected to said plurality of electrodes for applying an alternating voltage to said electrodes, means for applying a positive potential with respect to the cathode tc said plurality of electrodes the irequency of the alternating voltage and the dimensions of the electrodes being such that successive paths of travel of the electrons successively through said plurality of electrodes become shorter and shorter and energy is successively subtracted by said circuit means as electrons travel from the cathode to the anode.

9. An electron discharge device having an electron emitting cathode and an anode for receiving the electrons from the cathode, a plurality of electrodes surrounding the space traveled by the electrons from the cathode to the anode and of successively shorter length, circuit means connected to said plurality oi.' electrodes for applying an alternating voltage to said electrodes, other means for applying a positive potential with respect to said cathode to said plurality of electrodes, the frequency of alternating voltage and dimensions of the electrodes being such that energy is successively subtracted by the circuit means as electrons pass through said plurality of electrodes from the cathode to the anode, the iirst electrode closest the cathode serving as an accelerating electrode.

10. The method of obtaining electronic oscillations which comprises projecting electrons at relatively high velocity, creating regions of electric potential oi' successively decreasing length along the path of said electrons, varying said electric potentials in accordance with said oscillations,4 opposing the motion of said electrons by the fields of force produced in the rst of said regions, subtracting energy from said electrons by said opposition and thereby reducing their velocity, opposing the motion of said electrons moving at said reduced velocity in said second region, subtracting energy from said electrons by the last mentioned opposition, and continuing the steps of reducing the velocity of the electrons at successive regions and subtracting energy until the velocity oi' the electrons approaches zero.

11. The method of obtaining electronic oscillations from a device including an emissive electrode, a plurality of electrodes, and an anode which comprises projecting electrons at relatively high velocity in a straight line path toward said anode, creating regions of electric potential of successively decreasing length along the' path of said electrons, varying said electric potentials in accordance with said oscillations, opposing the motion oi' said electrons by the ileld of torce produced in the first of said regions, subtracting energy from said electrons by said opposition and thereby reducing their velocity, opposing the motion of said electrons moving at said reduced velocity in said second region, subtracting energy from said electrons by the last mentioned opposition, and continuing the steps of reducing the velocity of the electrons at successive regions and subtracting energy as the electrons move along said straight line path until the electrons reach said anode.

12. In the method described in claim 10 the additional step of advancing or retarding the projection of said electrons in accordance with said electronic oscillations to thereby increase the eiiicie'ncy of the subtraction of energy therefrom. v

i3. The method of obtaining electronic oscillations which comprises projecting electrons at relatively high velocity, creating regions of electric potential of successively decreasing length along the path of said electrons, varying said electric potentials in accordance with said oscillations, opposing the motion of said electrons by the eld of force created in said iirst region, subtracting energy from said electrons by said opposition and thereby reducing their velocity,

opposing the motion oi said electrons moving at said reduced velocity in said second region, subtracting energy from said electrons by the lastmentioned opposition, and continuing the steps of reducing the velocity of the electrons at successive regions and subtracting energy until'the velocity oi.' the electrons becomes substantially lower than their initial projection velocity.

14. The method of obtaining electronic oscillations which comprises projecting electrons at relatively high velocity, creating regions of electric potential of successively decreasing length along the path oi' said electrons,'varying said electric potentials in accordance with said oscillations, opposing the motion oi.' said electrons by the field of force created in said iirst region subtracting energy from said electrons by said opposition and thereby reducing their velocity, opposing the motion oi said electrons moving at said reduced velocity in said second region, subtracting energy from said electrons by the lastmentioned opposition, and continuing the steps of reducing the velocity ot the electrons in successive regions and subtracting energy until substantially all oi the energy of said electrons has been subtracted.

KARL FRI'I'Z.

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