US2217860A - Split cathode multiplier - Google Patents

Split cathode multiplier Download PDF

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Publication number
US2217860A
US2217860A US132325A US13232537A US2217860A US 2217860 A US2217860 A US 2217860A US 132325 A US132325 A US 132325A US 13232537 A US13232537 A US 13232537A US 2217860 A US2217860 A US 2217860A
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United States
Prior art keywords
cathode
electrons
cathodes
input
electron
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Expired - Lifetime
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US132325A
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English (en)
Inventor
Philo T Farnsworth
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Farnsworth Television and Radio Corp
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Farnsworth Television and Radio Corp
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Priority to US132325A priority Critical patent/US2217860A/en
Priority to GB6211/38A priority patent/GB512040A/en
Priority to FR835580D priority patent/FR835580A/fr
Application granted granted Critical
Publication of US2217860A publication Critical patent/US2217860A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/76—Dynamic electron-multiplier tubes, e.g. Farnsworth multiplier tube, multipactor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
    • H01J43/04—Electron multipliers
    • H01J43/06—Electrode arrangements
    • H01J43/18—Electrode arrangements using essentially more than one dynode
    • H01J43/20—Dynodes consisting of sheet material, e.g. plane, bent

Definitions

  • Hitherto electron multipliers have been roughly divided into two general types. First, the socalled direct-current multiplier, where the generation of secondaries takes place by successive impact of an electron stream with a series of emitting elements energized to successively increasing steady potentials; and second, that type of multiplier where repeated impacts are made between a pair of operatively opposed surface elements energized by alternating potentials.
  • radio-frequency amplifier and as an oscillator and oscillator-amplifier.
  • My invention possesses numerous other objects and features of advantage, some of which, to-
  • Figure l is a longitudinal sectional view of one preferred embodiment of my improved multiplier tube.
  • Figure 2 is a graph delineating input characteristics of a tube such as shown in Figure 1.
  • Figure 3 is a circuit diagram showing the device of Figure 1 connected as a radio-frequency amplifier.
  • Figure 4 is a circuit diagram showing the tube illustrated in Figure 1 connected as an oscillation amplifier.
  • Figure 5 is a circuit diagram showing the tube illustrated in Figure 1 connected as a directcurrent multiplier.
  • Figure 6 is a circuit diagram showing the tube illustrated in Figure 1 connected as a detectoramplifier.
  • Figure '7 is a circuit diagram showing the tube illustrated in Figure 1 connected as a modulatoramplifier.
  • Figure 8 is a circuit diagram showing the tube of Figure .1 connected for alternating-current energization.
  • Figure 9 is a circuit diagram showing the tube of Figure 1 connected to have the first cathode energized by alternating current, and the second cathode energized by direct current.
  • an envelope I is provided at one end with a re-entrant stem 2. Passing through the stem 2 are a pair of heater leads 4 supporting a heater coil 5, which is of high-resistance material, such as tungsten,v for example, and which may be raised to incandes cence by the passage of current therethrough; I prefer to form this coil in the form of a conical spiral.
  • a conical electron input source 6 supported by a lead I and closed at the open end by an insu- 55 lator 9 through which heater leads 4 may pass.
  • the source 6 is preferably of metal, and is preferably covered on the outside with a good electron emitter, such as barium and strontium ox-- ides. I prefer, in the embodiment shown, that the longitudinal section of the cone exhibit a cone angle of approximately twenty-three degrees.
  • a conical grid I0 Surrounding the conical electron source, I position a conical grid I0, having the same sectional angle as the cathode, coaxial with and spaced slightly from the source surface.
  • This grid may be in the usual form of a spiral refractory wire wound on supports, or it may be any other apertured control electrode, as' is well known in the art.
  • the side walls of the envelope I are utilized to support a pair of secondarily emissive ring cathodes II and I 2, these two cathodes being placed one above the other and shaped to describe a truncated cone, the small end of which surrounds an apical portion of the grid structure just described.
  • the lower cathode II is supported from the side wall by leads l4 and I5, and the upper cathode I2 is supported in like manner by leads I6 and Il.
  • Leads I5 and I! are brought entirely through the side wall to afford electrical connection to the two cathodes.
  • the large end or base of the truncated cone described by the cathodes is surrounded by a cup 20 provided with a.
  • is closed by a relatively coarse-meshed output screen 25, and extending downwardly, attached to the cup 20, is an accelerating anode 26 formed of relatively fine-meshed screening shaped into a truncated cone coaxial with cathodes II and I2, and positioned relatively close to the inner surface of the cathodes.
  • the accelerating anode extends the full length of both cathodes, and I prefer to form the body of the screen of small-diameter wire so that the total aperture area is greater than the total wire area.
  • the concave surface is preferably treated to prevent secondary emission, and for this purpose may be carbonized.
  • the final step in the processing of the tube I is the sensitization of cathodes II and I2 to be secondarily emissive when impacted by an electron traveling at the proper speed.
  • I prefer to sensitize the inner surface of the cathodes II and I2 with materials of extremely low work function, such as, for example, caesium or caesium on silver oxide, processed to have as high a secondary-emission function as possible.
  • materials of extremely low work function such as, for example, caesium or caesium on silver oxide
  • a caesium-silver oxide surface may be processed to give as high as ten and twelve secondary electrons per impacting primary electron, and to produce secondary emission at a ratio greater than unity at electron velocities in the vicinity of twenty volts.
  • Electrons emitted from source 6 in an amount depending upon the potential on grid I0 are accelerated outwardly along radial paths by the potential on accelerating anode 26. Most of them pass through the meshes of accelerating anode 26 and impact the first cathode H, sensitized for secondary emission. Secondaries are emitted having a low initial velocity, and these secondaries are accelerated back through the apertures in anode 26, passing through the space encompassed by anode 26' and through the opposite apertures of the anode to impact the second cathode I2, which is also secondarily emissive.
  • the secondaries emitted from the second cathode I2 are accelerated back into the space inside of anode 26, and pass out of the space through output screen 25 and are then drawn to collecting electrode 21.
  • the number of electrons reaching collecting electrode 21 is a function of the number which pass through grid III at the input end of the device.
  • the angles involved are such that when electrons leave cathode 6, they take an upward direction to impact first secondary cathode II, and that when they leave this cathode the angle is such that they will be certain to impact the second cathode I2, as they follow radii perpendicular to the emitting surface. There will thus be but one impact per cathode, and therefore, when used in this manner, the number of secondary generating impacts is equal to the number of cathodes.
  • the device may also be used as a detector simply by varying the grid bias, for example, or by handling the input grid H) in exactly the same manner as that of the ordinary triode tube would be handled.
  • the detector circuit is shown in Figure 6 and is identical with that shown in Figure 5, with the exception that the input is a radio-frequency signal, the choke coil used to connect the bias to the grid [0 is a radio-frequency choke coil 44, and the device has a by-pass condenser 45 from the output resistor to ground.
  • Figure 3 shows the device used as a radio-fre- Radio-frequency current is fed through input condenser 40, the grid being connected to ground through input resonant circuit 45, and the output from the collecting electrode being provided with a parallel resonant circuti 46, tuned to the same frequency as the input circuit. Under these conditions the device operates as a straight radio-frequency amplifier.
  • the device is an amplifier, it can readily be seen that it is an extremely eificient selfoscillator, and, referring to Figure 4, if the input grid Ill be connected to the input source by a tuned circuit 45, and the collecting electrode 2'! be grounded through an output resonant circuit 46, then it is possible for the device to self-oscillate. In this case I prefer to parallel-feed the collecting anode 21 through feed choke coil 41.
  • the radio-frequency amplifier circuit shall not oscillate. This may be done in a number of diiferent manners, such as detuning either the input or output circuit, neutralizing as with a triode, or by other expedients readily understandable to those skilled in the art.
  • the tube of my invention is shown connected as a modulator-amplifier in Figure 7.
  • die-frequency current is supplied to grid l0 through input condenser 40, and the grid is through a modulation resistor 5
  • bias source 4 I biased for proper amplification by bias source 4 I.
  • the usual energizing sources 35, 36, 3! and 38 are applied as described for other circuits, but,
  • modulation energy from a modulator is supplied to the first secondary cathode l I
  • a resonant output circuit 46 is used in this case as a work circuit, lead 54 being utilized to draw energy therefrom.
  • this tube simply acts as a radiofrequency amplifier of the energy received by grid l0.
  • Grid [0 regulates the number of electrons reaching secondary cathode ll.
  • the potential on secondary cathode l I is not constant, due to the fact that it is being changed by modulator tube 50.
  • secondary stream emitted from cathode ll' will therefore vary in accordance with the r-f input and with the modulation, and this stream will be amplified upon impact with secondary cathode l2, where the stream will generate new secondaries to be picked up by collector 21.
  • both cathodes II and I2 are supplied with alternating-current from oscillator 60 through radio-frequency transformer BI, and in addition, the secondary cathodes II and I2 are usually additionally supplied with a steady positive bias from sources 35 and 36 respectively, source 36 being by-passed with a condenser 62 as it is in thealternating-current path.
  • the circuit shown in Figure 9 is a modulator circuit similar to that shown in Figure 7, with the exception that in this case the modulation potentials are supplied through input condenser 40, and the radio-frequency current to be moduinput potential may be given to grid l0, and generator 60 and transformer 6
  • the tube can be used as a straight amplifier wherein several secondary generating impacts may be obtained on the lower cathode by the use of alternating current thereon, whereas only a single secondary generating impact will be obtained on the upper cathode l2.
  • the electrode assembly without including collecting electrode 21, can be made to self-oscillate.
  • a diode comprising accelerating anode 26 and only one cathode, H or l2, will self-oscillate, provided they are connected by a resonant circuit as described in my prior and copending application, Serial No. 61,042, filed January 27, 1936, now United States Patent No. 2,137,528 issued November 22, 1938. It is therefore obvious that when used as an oscillation generator, and high potentials utilized between collecting electrode 21 and screen 25, an extremely high power oscillating output may also be obtained. In other words, whether used as a direct-current amplifier, alternating-current amplifier or self-oscillator,
  • the output may be controlled, varied or modulated at the beginning of the multiplication cycle where control energy may be small, whereas high power may be obtained from the device by the use of high potentials at the output end.
  • multipliers of the character herein described may be readily stabilized as to frequency.
  • oscillator 60 be stabilized as, for example, by crystal control thereof, the multiplied output will be stable.
  • a relatively unstable source 50 may be used and a stiff high-Q circuit may be used for the transfer circuit 6
  • the stabilizing elements are required to carry only a small fraction of the power dissipated in the device, and the tube may be stabilized independently of the input grid.
  • input source 6 may be a thermionic cathode controlled by a grid II]. It is obvious that source 6 may be, for example, a photoelectric cathode subject to the influence of light. It is also possible to liberate electrons from other apparatus so that they will travel in directions suitable to land them on the first cathode I I. I therefore use the term input source in this specification in its broadest meaning, and do not desire to be limited to any particular method for generating or obtaining the input electrons, since the fundamental operation of [the tube is entirely independent of the type of input source.
  • the tube I have described here in one preferred physical embodiment is an extremely efllcient electronic tool, and one which is capable of being used in practically any circuit where heretofore a standard grid-controlled electron relay has been used, with the additional feature that extremely high outputs are obtainable because of the amplification which takes place after the first control of primaries, and that combinations of function can be obtained which heretofore have required a plurality of tube structures.
  • the angular relationships shown and described are also important, because the paths of the electrons become longer as the electron density increases, thus reducing space charge limitations, as has heretofore been described in my application Serial No. 80,194, of which the present application is a continuation in part, and which is referred to at the beginning of this specification.
  • an envelope containing a hollow apertured accelerating anode having a small input end and a larger output end, a plurality of coaxial unheated cathodes surrounding said anode and serially positioned along said anode from input to output end, means for generating electrons adjacent the inner surface of the small+ end, and means for collecting electrons adjacent the large end after a plurality of cathodic impacts between generation and collection.
  • an envelope containing a plurality of orbital unheated. cahodes positioned serially to describe a truncated cone and energized to successively increasing potentials in accordance with size, means for generating and controlling electrons positioned adjacent the inner surface of the smallest cathode, means for directing generated electrons against inner surfaces of said cathodes in order, beginning with the smallest, and means for collecting secondary electrons emitted from the largest cathode.
  • an envelope containing a plurality of orbital unheated-cathodes positioned serially to describe a truncated cone and energized to successively increasing potentials in accordance with size means for liberating electrons adjacent the smallest cathode, a single accelerating electrode positioned to accelerate electrons emitted from the inner surface of one cathode ring in a direction insuring impact with an area on the inner surface of the next largest ring substantially diametrically opposite the point of origin of the secondary electrons, said accelerating electrode being at a higher potential than any of said cathodes, and means for collecting secondary electrons emitted from the largest cathode.
  • .tal cathodes of increasing size, means for liberin the space bounded by one cathode into the v aameao cathodes for directing electrons within the space enclosed by one cathode to the inner surface of the next, and means for collecting electrons emitted from the largest cathode.
  • an envelope containing a plurality of orbital unheated cathodes positioned serially to describe a truncated cone means for energizing said cathodes to potentials increasing in relation to size, means for directing electrons in the space bounded by one cathode into the space bounded by the next larger cathode, a conical electron source having at least its apex entering the space bounded by the smallest cathode, and electron-collecting means adjacent the largest cathode.
  • an envelope containing a plurality of orbital unheated cathodes positioned serially to describe a truncated cone means for energizing said cathodes to potentials increasing in relation to size, means for directing electrons space bounded by the next larger cathod, a conical electron source having at least its apex entering the space bounded by the smallest cathode, a conical control electrode surrounding said source, and electron-collecting means adjacent the largest cathode.
  • An electron multiplier comprising an envelope containing a plurality of cathode rings describing a truncated cone, a coaxial apertured accelerating electrode enclosed by said rings, means for energizing said rings 'to potentials increasing with respect to the size thereof, means for energizing said accelerating electrode to a potential higher than any of said cathodes, means for emitting electrons within the bounds of the smallest cathode, and means for collecting electrons emitted from thelargest cathode.
  • An electron multiplier comprising an envelope containing a plurality of cathode rings describing a truncated cone, a coaxial apertured accelerating electrode enclosed by said rings,
  • Anelectron multiplier as set forth in claim 7, with additional means for applying an alternating potential on one of the rings 01' a frescribing a truncated cone, a coaxial apertured accelerating electrode enclosed by said rings,
  • means for energizing two adjacent rings to the same steady potential means for energizing said two rings with an alternating potential, means for energizing said accelerating electrode to a potential higher than any of said cathodes, means for emitting electrons within the bounds of the smallest cathode, and means for collecting electrons emitted from the largest cathode.
  • An electron multiplier comprising an envelope containing a plurality of cathode rings describing a truncated cone, a coaxial apertured accelerating electrode enclosed by said rings, means for energizing two adjacent rings to the same steady potential, means for energizing said two rings with an alternating potential in opposite phase, means for energizing said accelerating electrode to a potential higher than any of said cathodes, means for emitting electrons within the bounds of the smallest cathode, and means for collecting electrons emitted from the largest cathode.

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  • Electron Sources, Ion Sources (AREA)
US132325A 1937-03-22 1937-03-22 Split cathode multiplier Expired - Lifetime US2217860A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US132325A US2217860A (en) 1937-03-22 1937-03-22 Split cathode multiplier
GB6211/38A GB512040A (en) 1937-03-22 1938-02-28 Improvements in or relating to electron multipliers
FR835580D FR835580A (fr) 1937-03-22 1938-03-22 Dispositif multiplicateur d'électrons

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US132325A US2217860A (en) 1937-03-22 1937-03-22 Split cathode multiplier

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GB (1) GB512040A (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2777948A (en) * 1951-06-14 1957-01-15 Farnsworth Res Corp Blanking circuit for electron multiplier
US20030151341A1 (en) * 2002-02-13 2003-08-14 Dayton James A. Electron source
FR2999797A1 (fr) * 2012-12-19 2014-06-20 Thales Sa Dispositif de generation d'ondes hyperfrequences a double cathodes
US11588421B1 (en) 2019-08-15 2023-02-21 Robert M. Lyden Receiver device of energy from the earth and its atmosphere
US12136824B2 (en) 2019-08-15 2024-11-05 Robert M. Lyden Device for receiving and harvesting energy from the earth and its atmosphere

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE884388C (de) * 1939-02-01 1953-07-27 Sueddeutsche Telefon App Reihenvervielfacher mit einer Photokathode und mit magnetischem Querfeld
DE859182C (de) * 1948-09-28 1952-12-11 Philips Nv Hochvakuumroehre mit Bariumoxydkathode

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2777948A (en) * 1951-06-14 1957-01-15 Farnsworth Res Corp Blanking circuit for electron multiplier
US20030151341A1 (en) * 2002-02-13 2003-08-14 Dayton James A. Electron source
US7071604B2 (en) * 2002-02-13 2006-07-04 Genvac Aerospace Corporation Electron source
FR2999797A1 (fr) * 2012-12-19 2014-06-20 Thales Sa Dispositif de generation d'ondes hyperfrequences a double cathodes
EP2747117A3 (fr) * 2012-12-19 2016-03-30 Thales Dispositif de génération d'ondes hyperfréquences à double cathodes
US11588421B1 (en) 2019-08-15 2023-02-21 Robert M. Lyden Receiver device of energy from the earth and its atmosphere
US12136824B2 (en) 2019-08-15 2024-11-05 Robert M. Lyden Device for receiving and harvesting energy from the earth and its atmosphere

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Publication number Publication date
FR835580A (fr) 1938-12-26
GB512040A (en) 1939-08-28

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