US2591012A - Electron tube of the high-frequency and high-power type - Google Patents

Description

Filed Sept. 17, 1949 April 1, 1952 w. w. SALISBURY 2,591,012

ELECTRON TUBE OF THE HIGH-FREQUENCY AND HIGH-POWER TYPE 2 SHEETS-SHEET l @qmmqmp unnmwfl FIG. 4.-

h 1:? K if a; OUTPUT I N VEN TOR. W/NF/ELD. w SALISBURY ATTO EY W. W. SALISBURY April 1, 1952 ELECTRON TUBE OF THE HIGH-FREQUENCY AND HIGH-POWER TYPE Filed Sept. 17, 1949 2 SHEETS-SHEET 2 vllllllldn Z VIII!!! 5! Patented Apr. 1, 1952 ELECTRON TUBE OF THE HIGH-FREQUENCY AND HIGH-POWER TYPE Winfield W. Salisbury, Cedar Rapids, Iowa, as-

signor to Collins Radio Company, Cedarltapids, Iowa, a corporation of Iowa Application September 17, 1949, Serial No. 116,365

6 Claims. 1

This invention relates to electron discharge tubes, and more especially it relates to such tubes capable of operating at very high frequencies and with high power output.

A principal object of the invention isto provide an improved tube of the type such as disclosed in U. S. Patent No. 2,405,762.

Another object is to provide an improved electron tube structure which is capable of use as an oscillator, modulator, or amplifier, at ultrahigh-frequencies, for example frequencies of the order of 1,000 megacycles per second, and with a high power output.

Another object is to provide an electron tube of the type which is capable of producing larger power outputs without requiringcorrespondingly higher electron accelerating potentials and without-employing so-called velocity modulationoi the electrons;

A feature of the invention relates to an electron discharge tube of the type having an electron multiplier section forming part of the tube mount and for increasing the power output for a given set of accelerating voltages.

Another feature relates to the novel organization, arrangement and relative location and interconnection of parts which cooperate to pro vide an improved ultra-high-frequency tube having high power output and employing electron density modulation as distinguished from electron velocity modulation.

Other features and advantages not specifically enumerated, will be apparent after a consideration of the following detailed descriptions andthe appended claims.

In the drawing,

Fig. '1-is an exploded view of the electrode array'according to the invention.

Fig. 2is a partial sectional view of the electron multiplier section of Fig. 1.

Fig. 3 is a top plan view of the multiplier partly illustrated in Fig. 2.

Fig. 4 is a composite structural and circuit schematic of a tube-according to the invention.

Fig. 5 is an elevational-sectional view of the tubeshown in Fig. 1.

Fig. .6 is asectional view of Fig. 5 taken along the line 6-6 thereof.

As is now well-known, the type tube illus trated in U. S. Patent No. 2,405,762 comprises an evacuated envelope or housing containing an-electron-emitting cathode which is mounted very close to a control grid so as to be .substantially coplanar with atleastpart of the grid structure, and an accelerating electrode is 10- cated between the control grid and anode'together with a boundary grid. When suitable high positive direct current potentials are anpled to the anode and accelerating grid andwith the control grid negatively biased, the-electro static lines of force from the anode and accelerating grid terminate almost entirely at the control grid boundary, so that electron emission is suppressed from the cathode to anode. However a very thin-walled lamina of negative space charge exists adjacent the cathode and control grid, and when the control-grid swings in potential in a positive direction, a "certain percentage of the accelerating electrostatic lines of force shift their terminations .ifromthe control grid to the cathode. When this happens, there is a'sudden burst of electrons which leave the cathode and penetrate the space charge lamina, and then progress at high velocity to the anode. However this momentary burst or explosion of electrons from the oathode to the anode occurs only during the peak portions of the cycle of excitation of the control grid. Because of the shallowness 'of'the space charge lamina adjacent the cathode, all the electrons at each burst or explosion, pass therethrough, but the loss of transittim'e in such passage is a very small fraction of the total transit time between cathode and anode. Furthermore, because of the explosive nature of the emission and the high accelerating potentials, substantially all the electrons in any given burst, reach the anode in substantially the same phase. This distinguishes thistype of tube from the conventional control grid tube, wherein the transit time between cathode andcontrol grid is a substantial fraction of the total transit'time between cathode and anode, and wherein the electrons reach the anode at different phases. Likewise this type of tube is distinguishedfrom the conventional velocity modulation tube, since the signal potentials applied to the control grid merely modulate the density of the electrons in each burst and without substantial "velocity modulation thereof. However, even while the space charge lamina may be considered 'as a reservoir of electrons which is instanteously opened or broken down to release the electrons to the anode in sudden burst, this spacecharge lamina doesyto a certain extent, act as'a limitation on the 'total number of electrons that can reach the anode in any 'given'burst-or explosion, and to that extent it reduces the maximum power output that can be obtained TfOl a given set of accelerating voltages. 1

. member 8.

I in the electron multiplier art.

I have found that this limitation can be overcome to a substantial extent, by incorporatin in the mount a series of sets of electron multi-. pliers. Referring to Fig. 1 of the drawing, there is shown in exploded view the electron array of a tube according to the invention. Merely for simplicity in illustration, the enclosing envelope or evacuated container for the several electrodes is omitted, and the various supply and transmission line lead-in connections for these elec trodes are likewise omitted. However these connections are schematically illustrated in 4. Inasmuch as these connections are well-known in the art and are fully illustrated and explained in U. S. Patent #2,405,762, their repetition is not deemed necessary herein. Furthermore, the showing of Fig. 1 is not intended to represent the actual spacing of the various electrodes. In general the mount or electrode array comprises a pair of concentric rings 1, 2, which are bridged by a series of radially-extending electron-emitting cathode elements 3. These cathode elements may be in the form of inverted U-shaped memhers attached to their respective rings, and are preferably equally radially spaced around the said rings. Suitably supported closely adjacent to the ring I is another metal ring 4 which carries a series of control grid units 5. Each of these grid units may be in the form of a pair of parallel spaced radially-extending metal rods 5, l. The grid units 5 are equal in number to the number of cathode sections 3, and they are mounted in radial alignment with the respective cathode sections. As indicated schematically in Fig. 4, each pair of grid rods 6, l, is mounted substantially coplanar with the corresponding cathode section 3. It will be understood, of course, that in view of the exploded illustration in Fig. 1, the spacing between the cathode sections and the corresponding aligned grids is greatly exaggerated. Suitably supported in spaced relation to the grids, is an electron multiplier section com prising for example a cylindrical metal member 8 having insulatingly supported through the wall thereof a plurality of sets of electron multiplier units 9, there being one of these multiplier units for each section 3 of the cathode and for each corresponding section 5 of the grid. Each multiplier section may comprise a series of staggered secondary electron-emitting electrodes H), H, 12,

I3, l4, l5, each of which is individually supr ported by a corresponding lead-in member It which insulatingly passes through the wall of While the drawing shows six such electron multiplier electrodes for each radial unit of the cathode and grid, it will be understood that a greater or less number may be employed. The electrodes ill-l5 are made of any material which acts as a copious source of secondary electrons when subjected to electron bombardment, and if desired, these electrodes may have their surfaces coated with a suitable material for releasing secondary electrons, as is well-known The secondary emission electrodes of each unit are arranged in vertically staggered relation so that the primary electrons which are passed by the corresponding grid unit 5, and as schematically represented by the trajectory ll, strike the first secondary emission electrode 10 to release second aries therefrom, which in turn strike the electrode II to release additional secondaries, and so on until the final secondary emission electrode l5 releases a much greater number of secondary electrons in the trajectory l8. In other words,

the trajectory ll of the primary electrons is in substantial alignment with the trajectory 18 of the secondary electrons. In order to effect this multiplication, each of the successive electrodes Ill-l5 is connected to a successively higher positive direct current potential than the preceding electrode, as indicated schematically in Fig. 4. Suitably mounted in spaced relation to the upper end of the member 8, is the accelerating grid 19 comprising, for example, a flat metal plate having a central opening 20 and a series of radially-extending slots or windows 21 equal in number and radially aligned with the grid units 5. The electrode 19 is designed to act as an accelerating electrode, and for that purpose is connected to a suitable high direct current positive potential, for example --10 kilovolts, approximately.

Also suitably mounted in spaced relatio to the grid 18 is the boundary grid 22 which may comprise a cup-like metal member having a central opening 23 and a series of radial openings 24 equal in number and radially aligned with the corresponding slots 21 above described. Preferably, although not necessarily, each of the openings 26 is surrounded by an integral flange 25. Suitably mounted in spaced relation to the electrode 22 is the anode 26, consisting for example of a circular metal block having a series of radially-extending and inverted V-shaped grooves 21 equal in number and radially aligned with the corresponding windows 2| and 24. The anode 26 is arranged to be connected to a suitable high positive direct current potential, as indicated schematically in Fig. 4. Merely for simplicity in the drawing, Fig. 4 shows only one section of the cathode, the corresponding section of the grid, and the corresponding section of the electron multiplier unit.

Preferably, although not necessary, the evacuated enclosing envelope 23 is of metal, and may be grounded. The operation of the tube is along the following lines. The cathode 3 may be grounded, and the grid 5 is suitably insulated from the envelope 28 and is connected by suitable tuned transmission line arrangement such as described in the said U. S. Patent- 412,405,762 to a source of input signals. The grid 5 is also suitably negatively biassed with respect to the cathode, for example by 1000 volts negative. The successive electrodes Ill-l5 of the corresponding multiplier unit are connected respectively to successively increasing positive voltage taps on the direct current power supply source which is schematically illustrated in Fig. 4 as a battery 29. It will be understood, of course, that this source may comprise any well-known highly regulated direct current power supply source, and of course the lead-ins lfi'for the various multiplier electrodes are insulated from the casing 20. The lead-in member 30 for the accelerator electrode I9 is likewise insulated from the casing 28 and is connected to a higher positive tap on the source 29, for example at 10,000 positive direct current volts. The boundary electrode 22 can be connected to the grounded casing 28. The lead-in 3| for the anode 26 is likewise insulated from the casing 28 and is connected to a suitable positive potential tap on the source 29, for example 12,000 volts positive. The anode 26 may form one of the walls of a cavity resonator 32 as explained in said Patent #2,405,'762, and a small inductive loop 33 may extend into this cavity and can be connected to a suitable output circuit.

When the tube is to be used as an oscillator; it will be understood that the output and input circuits are suitably coupled for feedback so that the anode and grid swing in potentialin the same sense, so that the grid reaches its positive peak potential at the same instant that the anode reaches its positive peak potential. By a suitable choice of potentials for the various electrodes, the transit time of the electronsfin each burst is substantially one-half cycle of the generated oscillations. Therefore, immediately after each electron burst has ceased, the anode starts to swing negatively. The secondary electrons from the final electrodes l of each of the multiplier sections reach their maximum velocity at approximately the plane of the accelerator grid 19, or more desirably, just as they pass the effective plane of the grid 22. Consequentlyas these secondary electrons approach the anode which is beginning to swing negatively, they are subjected to a decelerating field or at least to a decelerating component, andtherefore they deliver energy to the output circuit. Furthermore, when they deliver their energy at this instant, they are traveling at minimum relative velocity when they enter each of the slotsjfj'l.

Because of the instantaneous burst and high acceleration of the primary electrons that break through the space charge lamina adjacentf the cathode, the secondary electrons from the final multiplier electrodes l5 of the various setsarrive at the anode in groups which are correlated with the groups of electrons for each burst through the space charge lamina, and therefore substantially all the secondary electrons reach the anode in substantially the same phase.

It will be understood, of course, that thetube according to the invention can be used either as an oscillator, as an amplifier, or as a modulator.

While one particular embodiment has been described herein, it will be understood that various changes and modifications may be made therein without departing from the spirit'and scope of the invention.

What is claimed is:

1. An electron tube of the kind described, comprising an electron-emitting cathode having a plurality of discrete emitting sections, a control grid having alike number of discrete 'sections each disposed closely adjacent a corresponding cathode section, an electron multiplier having a plurality of discrete sections one foreach of said grid sections, high voltage accelerating means for said secondary electrons, and an anode for the accelerated secondary electrons.

2 An electron tube according to claim 1, in which said cathode sections, grid sectionsand electron multiplier sections are symmetrically and radially disposed around a common central axis and in alignment in the direction of the electron trajectories between the cathode and anode.

3. Apparatus for ultra-high-frequency operation, comprising a plurality of discrete primary electron emitters, a control grid having sections 5 with one section for each cathode section, each control grid section comprising a pair of parallel spaced rods located approximately in the same plane as the corresponding cathode section and closely adjacent thereto, an electron multiplier unit having a series of separate sections, each section having an initial target responsive to primary electrons passed by a corresponding control grid section, a final secondaryemission target, and a plurality of intervening electron multiplier targets, an accelerating electrode having a plurality of separate windows each in alignment with the final target of a corresponding section of said secondary electron multiplier unit, and an output anode for receiving the secondary electrons passed by the windows in said accelerating electrode.

' 4. Apparatus according to claim 3, in which all the control grid sections are negatively biassed with respect to the cathode sections and said accelerating electrode is biassed positively with respect to the control grid sections to cause electron emission to take place from the cathode to the anode only during the peaks of positive grid excitation waves.

5. Apparatus of the kind described, comprising an evacuated enclosing envelope, an electron tube array within said envelope consisting of a pair concentric rings bridged by a series of radially-extending electron-emitting cathodes, another ring mounted adjacent the first-mentioned rings and having a plurality of radiallyextending pairs of grid spokes each pair being closely adjacent and parallel to each other and approximately coplanar with a corresponding cathode section, a plurality of sets of secondary emission targets each set being mounted in alignment with a corresponding pair of grid spokes, an electron-accelerating electrode having a plurality of radially-extending windows in alignment with said grid spokes, and an anode to receive the secondary electrons passing through the windows of said accelerating electrode.

'6. Apparatus according to claim 5, in which said anode has a plurality of radially-extending grooves in its surface facing said cathodes and an electron boundary electrode is located between the accelerating electrode and the anode said boundary electrode having a series of beamconfining windows aligned with the windows in the accelerating electrode and with the radial grooves in said anode.

WINFIELD W. SALISBURY.

. REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,233,878 Snyder Mar. 4, 1941 2,264,269 Banks Dec. 2, 1941 2,291,767 Shore Aug. 4, 1942 2,405,762 Sloan Aug. 13, 1946 FOREIGN PATENTS 5 Number Country Date 540,893 Great Britain Nov. 4, 1941

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