US2252565A

US2252565A - Electron discharge device

Info

Publication number: US2252565A
Application number: US323071A
Authority: US
Inventors: Andrew V Haeff
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1940-03-09
Filing date: 1940-03-09
Publication date: 1941-08-12
Anticipated expiration: 1958-08-12

Description

Aug. 12, 1941. A. v. HAEFF ELECTRON DISCHARGE DEVICE Filed March 9, 1940 3 Sheets-Sheet 1 ELECTRON BEAM ELECTRON BEAM ELECTRON BEAM fl 4m 0111 (AM EMA M 06 0! N 0 mu Ma Q,

.n llllll lllllllllllllllllllllllll 1 HEN/ml /8EAM INVENTOR. ANDREW M HAEFF By A vfikmkam 0 ATTORNEY.

Aug. 12 1941. A. v. HAEFF 2,252,565

ELECTRON DISCHARGE DEVICE Filed March 9, 1940 3 Sheets-Sheet 2 INVENTOR. ANDREW 1/. HAEFF ATTORNEY.

Aug. 12, 19411 A. v. HAEFF ELECTRON DISCHARGE DEVICE Filed March 9, 1940 3 Sheets-Sheet 3 T WN R. l a 2 5 25 MM h J a k A If? I T 1 #1 Q l/ f; a L

my u MA m EH c 0 W n 1 W m N A Patented Aug. 12, 1941 OFICE ELECTRON DISCHARGE DEVICE Andrew V. Haeff, East Orange, N. 3., assignor to Radio Corporation of America, a corporation of Delaware Application March 9, 1940, Serial No. 323,071

Claims.

My invention relates to electron discharge devices, more particularly to such devices utilizing a plurality of electron beams.

One of the difficulties encountered with tubes utilizing electron beams has been the eifeot of space charge. Space charge causes the lowering of space potential between the cathode and anode, thus setting an upper limit to the perveance of the electrode system and changing the electron velocity distribution over the cross section of the beam. Space charge may also give rise to hysteresis eifects.

It is therefore the principal object of my invention to provide an electron discharge device utilizing an electron beam or beams in Which the effects of space charge are substantially reduced or eliminated.

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 Figure 1 is a longitudinal section diagrammatically showing an electron discharge device employing a beam, Figure 2 is a section taken along the line 2--2 of Figure 1, Figure 3 is a diagram representing the space potential for difierent current densities of an electron beam passing through the tube shown in Figure 1, Figures 4, 5, 6 and 8 are transverse sections of tubular electrodes and beams extending through said electrodes, Figures 7 and 9 are diagrams showing' space charge potential transverse 0f the tubular members shown in Figures 6 and 8,

Figure 10 is a side elevation partially in section of a beam tube employing the principles of my invention, Figure 11 is a transverse section of the tube shown in Figure 10, Figure 12 is a longitudinal section of another form of beam tube made according to my invention, Figure 13 is a longitudinal side view of the tube shown in Figure 12, and Figure 14 is a section taken along the line l4l4 of Figure 13.

To illustrate the problem and solution provided by my invention reference is had to Figures 1 to 9 inclusive.

In the electrode arrangement shown in Figure 1 the cathode l0 supplies a beam of electrons, which is collected by the anode or collector II. The beam may be formed by electrode 12 which may be at a positive or negative potential with respect to the cathode l0 and may, if desired, be modulated by the electrode I2 before passing through shielding electrode !3, the sheath electrode l4 and the shielding electrode 15. This sheath electrode 14 is preferably maintained at a positive potential with respect to the cathode. The position of the beam with respect to the sheath M is shown in Figure 2. As shown in Figure 3 with no current flowing through the sheath the space potential inside the sheath is uniform as indicated by the line a. As the beam current is increased the spacepotential will decrease. The distribution of the space potential across the beam for different values of the in jected current is shown by lines I), '0 audit. Curve d represents the distribution for the maximum current flow. If the injected current is increased above this maximum current the space potential will drop discontinuously to zero at the center of the beam at some point along'the length of the beam, thus forming a virtual cathode at that point. Partial electron reflection from the virtual cathode back to the cathode will result in a decrease of the collected current with any further increase in the injected current. The magnitude of the maximum current that can be passed through the sheath electrode depends upon the transverse dimensions and shape of the beam and the sheath electrode, upon the current distributions over the cross section of the beam and is proportional to the 3/2 power of potential of the sheath electrode. If the sheath electrode is' long compared to" its opening and the beam cross section is kept con-' stant by proper focusing, such as by a magnetic field in the direction of electron flow, then the maximum current does not depend 'upon the length of the beam and upon the potential of the end electrodes. The perveance G511 of the sheath electrode may be defined as the ratio of maximum current to the 3/2 power of sheath potential (Vsh), that is max V s/z In general, the perveance of the tube can be quired when the clearance between the beam and the sheath electrode is made smaller.

In accordance with my invention I provide an eifective method of minimizing the eifects of space charge. In Figure 6 is shown a sheath electrode of rectangular tubular cross section with a centrally positioned beam of rectangular cross section. The space potential is indicated in Figure 7. In accordance with my invention I subdivide the sheath into a plurality of closely adjacent cellular passageways by longitudinal partitions so that each of the passages or cells passes only a fraction of the total current. The space potential is then that shown in Figure 9 and it will be observed that the depression of the space potential is only slight. Because the perveance of the multi-cellular sheath electrode is proportional to the square of the number of cells for the same total cross section, the potential distribution for the same total current is more uniform throughout the cross section for the multi-cellular electrode. At the same time, the required focusing field is approximately the same for the two cases, because the reduction in the space charge field compensates for the reduced spacing between the beam and the sheath.

My invention can be applied to the so-called velocity modulation type of high frequency beam tube to provide a tube of this kind having a high perveance, which characteristic is particularly desirable with this type of tube. In this type of tube the negative conductance when the tube is used as an oscillator or the transconductance when used as an amplifier is proportional to the ratio of beam current to beam potential. Also, it is desirable to reduce the spread of electron velocities over the cross section of the beam because of the desirability of obtaining uniform electron transit time. Both of these requirements necessitate the reduction of space charge eifects which can be accomplished best by the use of multi cellular structures according to my invention. Another important advantage of multi-cellular structures in tubes having a plurality of electrodes in succession and used at high frequency is that because of the closely spaced partitions of the cells, the penetration of the potential field of one electrode into the adjacent electrode separated by a small gap is considerably reduced. This reduces the effective length of the gap and hence the electron transit time across it with a consequently more effective interaction between the electron stream and the active electrodes.

In Figures 10 and 11 is shown a socalled pushpull delay-grid oscillator making use of velocity modulation in which my invention employing the multi-cellular structure is used. The cathode may comprise two or more independently supported indirectly heated cathode elements, each of which supplies oppositely disposed streams of electrons. These electron streams are formed into a plurality of beams which may be focused by electrode 2| to pass through the accelerating electrodes 22 having cellular passages registering with each of the electron beams. The magnitude of the average current may be controlled by the flat type space charge grid 2|, to which a modulating voltage may or may not be applied. The accelerating electrodes 22 also serve to screen the cathode 20 from the radio frequency part of the tube. The electrons are collected by collector 24 after passing through output electrodes 23. All of the electrodes are mounted within evacuated envelope 25 and supported from the stem 25. The multi-cellular electrodes 23 may, as best shown in Figure 10, be connected to an oscillating circuit 28 in a push-pull arrangement, the positive voltage being supplied through the midpoint of the circuit from voltage source 21. The magnets 26-26 supply the magnetidfield parallel to the electron beams for maintaining the beams focused.

The electron streams are velocity modulated in the gaps between the

electrodes

22 and 23; that is, electrons approaching the electrodes 23 across the gap between

electrodes

22 and 23 at the time that the voltage on these electrodes is negative with respect to the average voltage are slowed down whereas electrons approaching this electrode when the potential on the electrode is positive are accelerated. Thus the electrons after passin the gap are moving at diiferent speeds through the electrode 23. Inside the output electrodes 23 the slow electrons are overtaken by the fast electrons so that the electrons leave electrode 23 in more or less well defined groups and in so doing the velocity modulated stream is converted into a current modulated stream so that as the electrons emerge from the electrodes 23 and flow across the gap between it and the collector 24 they induce a radio frequency voltage and current in electrode 23 and the oscillating circuit 28 connected to these two electrodes purely by the inductive action of the electron stream on the two electrodes 23. Energy is absorbed from the electrons as they leave the electrode 23 if the potential on the electrodes 23 is positive. The electrons absorb energy from these electrodes and connected circuit if the electrodes are negative as the electrons leave the electrodes 23. The length of the electrode 23 and the associated circuit elements are such however that there is a net transfer of energy from the modulated electron stream to the output electrodes 23 and their associated circuit. Thus the electrons are decelerated in the gaps between these output electrodes 23 and the collector electrode 24. The use of the multicellular electrodes in tubes of this type is advantageous for the reasons pointed out above.

Another example of an electron discharge device made according to my invention is shown in Figures 12 to 14 inclusive, in which a velocity modulated type of amplifier tube is shown. An envelope 35 is provided at one end with a circular re-entrant portion 36 through which lead wires extend to the various electrodes within the envelope. The electrodes, which as best shown in Figure 13 as supported between insulating spacing members 31 and 38, are so arranged as to provide a push-pull modulated tube. The cathode 39 is provided with a plurality of coextensive emitting sections indirectly heated and registering with longitudinal slots in the beam forming grid 46, the two portions of the cathode 39 being connected to different lead-in wires. A cellular type tubular electrode 4| is next provided for accelerating the beams of electrons directed through the cellular portions of this electrode. This is followed by the cellular type input control or modulating electrode comprising the

portions

42 and 42 which are electrically separated from each other and which register with the cellular passages through the accelerating electrode ll. The electron transit time through the modulating or input electrodes may be made approximately equal to a half period of oscillation. The six-cell drift electrode 43 provides a space in which the fast electrons of the velocity modulated beams tend to catch up with the slow electrons so that upon emerging from the drift electrode 43 the electron stream becomes current modulated and induces current in the

pushpull ouput electrodes

44 and 44". These output electrodes are provided with cellular passageways registering with the cellular passages in the drift space electrode. They are in turn followed by the electrode 45 having a plurality of cellular passages registering with the other passages and a collector electrode 46 which is suitably supported on the re-entrant stem 4! of the envelope. The push-pull input circuit is connected between the control electrodes 42 and 42' biasing being supplied by the biasing battery 52 connected to the mid-point of the input circuit 49. The grid electrode 40 is suitably connected to the voltage source 52* to provide a biasing potential. Accelerating electrode 4|, the drift tube 43 and the electrode 45 are connected to source 5| for proper bias. The

output electrodes

44 and 44 are connected to the opposite sides of the output circuit 50 to which voltage is applied to the mid-point by proper connection to the voltage source 52. The leads to the input and output electrodes may be provided as shown in Figure 13 at 421 and 441. A magnetic field for focusing purposes is provided by the solenoid 54 surrounding the tube envelope. This tube operates in substantially the same manner as that shown in Figures and 11, except that the three important functions, namely, velocity, modulation, conversion of velocity modulation into current modulation and extraction of energy from the electrons are performed by three separate electrodes, 42, 43, 44, so that the tube can be used for amplification as well as for generation of radio frequency energy.

While I have indicated the preferred embodiments ofmy 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 claims.

What I claim as new is:

1. An electron discharge device having means for supplying electrons, means for forming said electrons into a plurality of closely adjacent parallel beams, electrode means adapted to receive an alternating potential for simultaneously controlling said plurality of beams, other electrode means including a tubular electrode having a plurality of electrically connected partitions extending longitudinally of said electrode for providing a plurality of closely adjacent parallel cellular passages extending therethrough I and through which said electron beams are directed, each of said beams substantially filling its respective cellular passage whereby said beams are closely adjacent each other but have no electrical effect on'each other, and electrode means for receiving said beams.

2. An electron discharge device having a cathode for supplying electrons, means for forming said electrons into a plurality of closely adjacent parallel beams and for simultaneously controlling said plurality of beams, means including a tubular electrode having aplurality of electrically connected partitions extendinglongitudinally of said electrode for providing a plurality of closely adjacent parallel cellular passages extending therethrough and through which said electron beams are directed, each of said beams substantially filling its respective cellular passage whereby said beams are closely adjacent each other but have no electrical'effect on each other and a second tubular electrode adjacent said first and provided with a plurality of electrically connected partitions extending longitudinally of said electrode for providing a plurality of closely adjacent parallel cellular passages extending therethrough and registering with the cellular passages in the first tubular electrode, and electrode means for receiving said electron beams after passage through said tubular electrodes.

3. An electron discharge device having a cathode for supplying electrons, means for forming said electrons into a plurality of closely adjacent parallel beams, electrode means for receiving said electrons, electrode means positioned between the cathode and receiving means adapted to receive an alternating potential for simultaneously controlling said'plurality of beams, electrode means including a tubular electrode having a plurality of electrically connected partitions extending longitudinally of said electrode for providing a plurality of closely adjacent parallel cellular passages extending therethrough and through which said electron beams are directed, each of said beams substantially filling its respective cellular passage whereby said beams are closely adjacent each other but have no electrical effect on each other and a second tubular electrode adjacent said first but spaced therefrom to provide a gap and provided with a plurality of electrically connected partitions extending longitudinally of said electrode for providing a plurality of closely adjacent parallel cellular passages extending therethrough' and registering with the cellular passages in the first tubular electrode, energy being transferred to said second tubular electrode provided with cellular passages when said beams of electrons pass across the gap between the tubular electrodes.

4. An electron discharge device having means for supplying electrons, means for forming said electrons into a plurality of closely adjacent parallel beams and for simultaneously controlling said plurality of beams, a first tubular electrode having a plurality of electrically connected partitions extending longitudinally of said electrode for providing a plurality of closely adjacent parallel cellular passages extending therethrough through which said electron beams are directed, each of said beams substantially filling its respective cellular passage whereby said beams are closely adjacent each other but have no electrical effect on each other, a second tubular electrode having a plurality of electrically connected partitions extending longitudinally of said electrode for providing a plurality of closely adjacent parallel cellular passages extending therethrough and positioned closely to said first tubular electrode but separated therefrom by a small gap, the cellular passages of said second electrode registering with the cellular passages of said first tubular electrode, energy being transferred between the electron beams and the second tubular electrode upon passage of the beams across the gap between the tubular electrodes, and electrode means for collecting the electron beams after passage of the beams past said gap.

5. 'An electron discharge device having means for supplying electrons, means for forming said electrons into a plurality of closely adjacent parallel beams, and means for simultaneously controlling said plurality of beams for modulating said beams, a first tubular electrode having a plurality of electrically connected partitions extending longitudinally of said electrode for providing a plurality of closely adjacent parallel cellular passages extending therethrough through which said electron beams are directed, each of said beams substantially filling its respective cellular passage whereby said beams are closely adjacent each other but have no electrical efiect on each other, a second tubular electrode provided with a plurality of electrically connected partitions extending longitudinally of said electrode for providing a plurality of closely adjacent parallel cellular passages and positioned closely to said first tubular electrode but separated therefrom by a smal1 gap, the cellular passage ways of said second electrode registering with the cellular passages of said first tubular electrode, energy being transferred between the modulated electron beams and the second tubular electrode upon passage of the beams across the gap between the tubular electrodes and electrode means for collecting the electron beams after passage of the beams past said gap.

6. An electron discharge device having a cathode for supplying electrons, means for directing electrons from said cathode in streams in opposite directions and for forming each of the streams into a pluralit of closely adjacent electron beams, said means being adapted to receive a controlling alternating potential for simultaneously modulating all of said beams, a tubular electrode positioned on each side of said cathode and each provided with a plurality of cellular passage ways extending therethrough and registering with the electron beams, a collector electrode surrounding the cathode, the beam forming means and the tubular electrodes and a tubular electrode positioned between each of said first tubular electrodes and said collector electrode and provided with a plurality of cellular passage ways extending therethrough and registering with the cellular passage ways in the first tubular electrodes.

'7. An electron discharge device having a cathode for supplying electrons, means for directing electrons from said cathode in streams in opposite directions and for forming each of the streams into a plurality of closely adjacent electron beams, said means being adapted to receive a controlling alternating potential for simultaneously modulating all of said beams in one stream, a tubular electrode positioned on each side of said cathode and each provided with a plurality of cellular passage ways extending therethrough and registering with the electron beams, and a collector electrode for receiving the beams of electrons and surrounding said cathode, directing means and tubular electrode, and means for providing a magnetic field parallel to and extending through said tubular electrode.

8. An electron discharge device having means for supplying electrons, means for forming said electrons into a plurality of closely adjacent beams, a plurality of electrically separated tubular electrodes positioned adjacent the beam forming means and each provided with a plurality of closely adjacent cellular passage ways extending therethrough and registering with the plurality of electron beams, a second group of tubular electrodes provided with cellular passage Ways extending therethrough and registering with the passage ways in the first tubular electrode, said second group of tubular electrodes being adapted to receive an alternating potential for separately modulating the electron beams emerging from the tubular electrode registering with each of the second tubular electrodes, output electrodes each having a plurality of cellular passage ways therethrough registering with the passage ways of the first and second tubular electrodes and a collector electrode for receiving electrons after their passage through said last tubular electrode.

9. An electron discharge device having means for supplying electrons, means for forming said electrons into a plurality of closely adjacent beams, a plurality of electrically separated tubular electrodes positioned adjacent the beam forming means and each provided with a plurality of closely adjacent cellular passage ways extending therethrough and registering with the plurality of electron beams, a second group of tubular electrodes provided with cellular passage ways extending therethrough and registering with the passageways in the first tubular electrode, said second group of tubular electrodes being adapted to receive an alternating potential for separately modulating the electron beams emerging from the tubular electrode registering with each of the second tubular electrodes, output electrodes each having a plurality of cellular passage ways therethrough registering with the passage ways of the first and second tubular electrodes and a collector electrode for receiving electrons after their passage through said last tubular electrode, and a suppressor electrode positioned between the collector and each of the output electrodes and comprising atubular electrode provided with cellular-like passage ways extending therethrough registering with the cellularlike passage ways of said other tubular electrodes.

10. An electron discharge device having a cathode for supplying electrons, means for forming said electrons into a plurality of closely adjacent beams, a plurality of electrically separated coextensive tubular electrodes positioned adjacent the beam forming means and each provided with a plurality of closely adjacent cellular passage Ways extending therethrough and registering with the plurality of electron beams, a second group of tubular electrodes provided with cellular passage ways extending therethrough and registering with the passage ways in the first tubular electrode, said second group of tubular electrodes be ing adapted to receive an alternating potential for separately modulating the electron beams emerging from the plurality of tubular electrodes registering with each of the second tubular electrodes, output electrodes each having a plurality of cellular passage ways therethrough' registering with the passage ways of the first and second tubular electrodes and a collector electrode for receiving electrons after their passage through said last tubular electrode, and a third tubular electrode positioned between each of the first and second tubular electrodes and provided with cellular-like passage ways extending therethrough registering with the cellular-like passage ways of said other tubular electrodes.

ANDREW V. HAEFF.