US2044369A - Electron discharge device - Google Patents

Electron discharge device Download PDF

Info

Publication number
US2044369A
US2044369A US747139A US74713934A US2044369A US 2044369 A US2044369 A US 2044369A US 747139 A US747139 A US 747139A US 74713934 A US74713934 A US 74713934A US 2044369 A US2044369 A US 2044369A
Authority
US
United States
Prior art keywords
conductor
anode
control electrode
metallic
electron discharge
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US747139A
Inventor
Arthur L Samuel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US747139A priority Critical patent/US2044369A/en
Application granted granted Critical
Publication of US2044369A publication Critical patent/US2044369A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J5/00—Details relating to vessels or to leading-in conductors common to two or more basic types of discharge tubes or lamps
    • H01J5/02—Vessels; Containers; Shields associated therewith; Vacuum locks

Definitions

  • This invention relates to electron discharge devices and more particularly to such devices capable of generating and amplifying ultra-high frequency impulses.
  • an electron discharge device comprises an enclosing vessel having vitreous end portions and an intermediate metallic cylindrical portion which serves as the anode of the device.
  • the metallic portion is provided on its inner surface with a plurality of substantially cylindrical grooves or recesses in each of which a control electrode and a cathode are disposed.
  • the control electrodes may comprise wire helices carried by a metallic member or fins which are supported by a single metallic rod sealed in one of the vitreous end portions.
  • the cathodes may be linear filaments supported by and electrically connected to two metallic rods sealed in the other vitreous end portion.
  • Fig. 2 is a cross-sectional view along line 2-2 of Fig. 1 showing the configuration and relative positions of the electrodes, and
  • Fig. 3 is a view partly in cross-section showing the combination of the electron discharge device illustrated in Fig. 1 and cylindrical conductors associating the anode with the cathode and control electrode, in accordance with this invention. 5
  • the electron discharge device shown in Fig. 1 comprises an enclosing vessel having vitreous end portions I0 and II and an intermediate metallic portion l2, which may be of copper, hermetically sealed at its ends to the vitreous portions l0 and It.
  • the metallic portion l2 serves as the anode of the device and is provided on its outer surface with a cylindrical raised portion l3 forming spaced shoulders l4 and I5.
  • the inner surface of the metallic portion I2 is provided with two parallel diametrically opposite grooves or recesses l6 which may be substantially cylindrical as shown clearly in Fig. 2.
  • a control electrode assembly comprises a single metallic support or rod I l sealed in the vitreous end portion I I of the enclosing vessel and serving as a leading-in conductor.
  • the inner end portion of the support or rod I I is provided with a slot or groove for receiving a relatively large area plate member or fin which may comprise two plates i8 suitably secured together and to the rod H, as by welding.
  • the opposite lateral edges of the plates l8 are provided with outwardly bent lips I9 to which each turn or a suitable number of turns of wire helices or grids 20 are secured, as by welding.
  • the helices 20, which constitute control electrode elements, are disposed one within each of the grooves or recesses I 6 and coaxial therewith. Inasmuch as the plate members l8 are of relatively large area, they will radiate heat rapidly so that the grids 20 will be maintained at a relatively low temperature during operation of the device.
  • Disposed within each of the helices 20 and 00- axial therewith is a linear filamentary cathode 2
  • are secured at their ends to flexible metallic members or springs 22 which are individually supported by supports or rods 23 sealed in the vitreous end portion I 0 of the enclosing vessel and preferably disposed parallel to the support or rod IT.
  • the supports or rods l1 and 23 are maintained in the proper relation by insulating members 24 which are frictionally fitted on the support or rod l1 and held in position by wire stubs 25 secured to the rod.
  • the insulating members 24 are provided with apertures for receiving the supports or rods 23. The latter may fit loosely in the apertures in the insulating members 24 to allow free expansion and contraction of the supports or rods I1 and 23.
  • the enclosing vessel may be encompassed by two metallic conductors in the form of cylinders 26 and 21 which may fit loosely about cylindrical insulating mem-" bers 28, for example, mica sheets, suitably secured about the anode i2 and abutting against the shoulders l4 and I5. erably is coaxial with the control electrode leading-in conductor I1 and provides a portion of the external circuit between the control electrode and the anode.
  • the conductor 21 preferably is disposed coaxially with the cylinder 28 and provides a portion of the external circuit between the cathode and the anode.
  • the electrode structures, the cylindrical conductors 26 and 21, and the leading-in conductors I1 and 23 form distributed constant circuits, the tuning of which is controllable by the length thereof.
  • the length of the control electrode-anode system may be adjusted by a tie wire or short-circuiting disc 30 contacting with the rod i1 and the cylindrical conductor 28 and slidable along the rod and conductor. If there is no impedance discontinuity between the coaxial conductor system comprising the cylinder 26 and rod I1 and the distributed constant system comprising the anode and the control electrode or grid structure, the tie wire or disc 30 will be positioned substan tially one-quarter of the wavelength of the operating frequency from the remote end of the control electrode or grid structure.
  • the requisite position of the tie wire or short-circuiting disc to tune the anode-control electrode system to a desired frequency may be calculated readily in ways known to those skilled in the art.
  • An output or utilization circuit may be coupled to the control electrode circuit by a looped or U-shapedconductor 3
  • the distributed constant system including the conductors 23 and 21 may be terminated by a movable assembly including metallic discs 33 and '34 insulated from each other as by a disc of mica 35.
  • Each of the discs 33 and 34 engages a corresponding one of the rods 23 and is provided with an oversized aperture, as shown in. Fig. 3, through which the other rod extends.
  • One of the discs, for example the disc 33 engages the cylindrical conductor 21.
  • the length of the system affects the tuning of the device only indirectly and the position of the discs 33 and 34 may be varied to obtain the optimum operating condition.
  • the heating current for the cathode may be supplied from a suitable source, such as a battery, connected between the leading-in conductors 23, one terminal of the source being grounded.
  • a suitable source such as a battery
  • suitable potentials may be applied to the anode and control electrode by suitable sources, such as batteries, connected to the raised portion 13 of the anode and to the rod I' l respectively, one terminal of each of these sources also being grounded.
  • An electron discharge device comprising an enclosing vessel including vitreous end portions and an intermediate cylindrical metallic portion, said metallic portion having a plurality of recesses in its inner wall and serving as the anode of the device, a support extending from one of said end portions, a plate member carried by said support and having edges adjacent said recesses, helical grids secured to said edges and disposed in said recesses, a plurality of supports extending from the other of said end portions, and filaments carried by said second supports and disposed within said grids.
  • An electron discharge device comprising an enclosing vessel including a vitreous portion and a metallic portion, said metallic portion serving as an electrode of the device, an electrode within said envelope and cooperatively disposed with respect to said metallic portion, a leading-in conductor for said second electrode extending from said vitreous portion, and a hollow conductor encampassing said first conductor and said vitreous portion and portions of said metallic portion.
  • An electron discharge device comprising an enclosing vessel having vitreous end portions and an intermediate metallic portion constituting the anode of the device, a control electrode and a cathode within said vessel, 9. leading-in conductor for said cathode extending from one of said end portions, and a leading-in conductor for said control electrode extending from the other of said end portions, and tubular conductors encompassing said end portions and coupling said anode with said leading-in conductors.
  • An electron discharge device comprising an enclosing vessel including a vitreous portion and a metallic portion forming an electrode of the device, another electrode within said enclosing vessel, a leading-in conductor for said second electrode extending from said vitreous portion, a tubular conductor encompassing said first conductor and a part of said metallic portion, and a conductor insulated from and extending through said tubular conductor and having a portion in proximity to said leading-in conductor.
  • An electron discharge device comprising an enclosing vessel having a portion serving as an anode, a cathode, a control electrode, means carried by said vessel and disposed adjacent one end thereof for varying the capacitance and inductance between said anode and said control electrode, and means carried by said vessel and disposed adjacent the opposite end thereof for varying the capacitance and inductance between said cathode and said anode.
  • An electron discharge device comprising a pair of electrodes, a leading-in conductor extending from one of said electrodes, a metallic member in juxtapositionto said conductor and the other of said electrodes, and means electrically connecting said conductor and said memher, said means being movable along said conductor and said member whereby the inductance andcapacitance between said electrodes may be varied.
  • An electron discharge device comprising an anode, a cathode, and a. control electrode, a leading-in conductor extending from said cathode, a leading-in conductor extending from said control electrode, means including a tubular metallic member encompassing said first conductor and a portion of said anode and forming a distributed constant system therewith, and means including another tubular metallic member encompassing said second conductor and another portion oi said anode and forming a distributed constant system therewith.
  • An electron discharge device in accordance with claim 8 including means for varying the length of said second distributed constant system.

Description

ELECTRON DISCHARGE DEVICE Filed 001;. 6, 1934 INVENTOR By AL. SAMUEL AT TORNEV Patented June 16, 1936 UNITED STATES PATENT OFFICE Telephone Laboratories,
Incorporated, New
York, N. Y., a corporation of New York Application October 6, 1934, Serial No. 747,139
9 Claims.
This invention relates to electron discharge devices and more particularly to such devices capable of generating and amplifying ultra-high frequency impulses.
One object of this invention is to increase the power capacity and the efficiency of high frequency electron discharge devices.
Another object of this invention is to expedite the control of circuits including high frequency electron discharge devices.
In one embodiment of this invention, an electron discharge device comprises an enclosing vessel having vitreous end portions and an intermediate metallic cylindrical portion which serves as the anode of the device. The metallic portion is provided on its inner surface with a plurality of substantially cylindrical grooves or recesses in each of which a control electrode and a cathode are disposed.
The control electrodes may comprise wire helices carried by a metallic member or fins which are supported by a single metallic rod sealed in one of the vitreous end portions.
The cathodes may be linear filaments supported by and electrically connected to two metallic rods sealed in the other vitreous end portion.
The enclosing vessel may be encompassed by two coaxial conductors disposed one about the control electrode supporting rod and the other about the cathode supporting rods. These conductors and rods form external circuits between the cathode and anode, and control electrode and anode, and the effective impedance between the several electrodes may be controlled by varying the length of these conductor systems.
The conductor encompassing the grid supporting rod may be connected directly to the rod by a movable short circuiting wire or disc whereby the operating frequency of the device may be adjusted. This conductor need not be so connected, but may also be coupled to the grid rod solely through the distributed oapacitances and inductances between the conductor and the rod.
The invention and the features thereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawing in which:
Fig. 1 is a perspective view of an electron discharge device constructed in accordance with this invention, portions of the enclosing vessel being broken away to show the internal structures more clearly;
Fig. 2 is a cross-sectional view along line 2-2 of Fig. 1 showing the configuration and relative positions of the electrodes, and
Fig. 3 is a view partly in cross-section showing the combination of the electron discharge device illustrated in Fig. 1 and cylindrical conductors associating the anode with the cathode and control electrode, in accordance with this invention. 5
Referring now to the drawing, the electron discharge device shown in Fig. 1 comprises an enclosing vessel having vitreous end portions I0 and II and an intermediate metallic portion l2, which may be of copper, hermetically sealed at its ends to the vitreous portions l0 and It. The metallic portion l2 serves as the anode of the device and is provided on its outer surface with a cylindrical raised portion l3 forming spaced shoulders l4 and I5. The inner surface of the metallic portion I2 is provided with two parallel diametrically opposite grooves or recesses l6 which may be substantially cylindrical as shown clearly in Fig. 2.
A control electrode assembly comprises a single metallic support or rod I l sealed in the vitreous end portion I I of the enclosing vessel and serving as a leading-in conductor. The inner end portion of the support or rod I I is provided with a slot or groove for receiving a relatively large area plate member or fin which may comprise two plates i8 suitably secured together and to the rod H, as by welding. The opposite lateral edges of the plates l8 are provided with outwardly bent lips I9 to which each turn or a suitable number of turns of wire helices or grids 20 are secured, as by welding. The helices 20, which constitute control electrode elements, are disposed one within each of the grooves or recesses I 6 and coaxial therewith. Inasmuch as the plate members l8 are of relatively large area, they will radiate heat rapidly so that the grids 20 will be maintained at a relatively low temperature during operation of the device.
Disposed within each of the helices 20 and 00- axial therewith is a linear filamentary cathode 2|, which may be of thoriated tungsten or other material having good thermionic emission characteristics. The filamentary cathodes 2| are secured at their ends to flexible metallic members or springs 22 which are individually supported by supports or rods 23 sealed in the vitreous end portion I 0 of the enclosing vessel and preferably disposed parallel to the support or rod IT.
The supports or rods l1 and 23 are maintained in the proper relation by insulating members 24 which are frictionally fitted on the support or rod l1 and held in position by wire stubs 25 secured to the rod. The insulating members 24 are provided with apertures for receiving the supports or rods 23. The latter may fit loosely in the apertures in the insulating members 24 to allow free expansion and contraction of the supports or rods I1 and 23.
As clearly shown in Fig. 3, the enclosing vessel may be encompassed by two metallic conductors in the form of cylinders 26 and 21 which may fit loosely about cylindrical insulating mem-" bers 28, for example, mica sheets, suitably secured about the anode i2 and abutting against the shoulders l4 and I5. erably is coaxial with the control electrode leading-in conductor I1 and provides a portion of the external circuit between the control electrode and the anode. The conductor 21 preferably is disposed coaxially with the cylinder 28 and provides a portion of the external circuit between the cathode and the anode.
It will be apparent that the electrode structures, the cylindrical conductors 26 and 21, and the leading-in conductors I1 and 23 form distributed constant circuits, the tuning of which is controllable by the length thereof. As shown in Fig. 3, the length of the control electrode-anode system may be adjusted by a tie wire or short-circuiting disc 30 contacting with the rod i1 and the cylindrical conductor 28 and slidable along the rod and conductor. If there is no impedance discontinuity between the coaxial conductor system comprising the cylinder 26 and rod I1 and the distributed constant system comprising the anode and the control electrode or grid structure, the tie wire or disc 30 will be positioned substan tially one-quarter of the wavelength of the operating frequency from the remote end of the control electrode or grid structure. If an impedance discontinuity does exist between the coaxial conductor system and the distributed constant system noted, the requisite position of the tie wire or short-circuiting disc to tune the anode-control electrode system to a desired frequency may be calculated readily in ways known to those skilled in the art.
An output or utilization circuit may be coupled to the control electrode circuit by a looped or U-shapedconductor 3| extending through insulating bushings 32 fitted in the metallic cylinder 26, the conductor 3| extending adjacent, but not contacting with the support or rod H.
The distributed constant system including the conductors 23 and 21 may be terminated by a movable assembly including metallic discs 33 and '34 insulated from each other as by a disc of mica 35. Each of the discs 33 and 34 engages a corresponding one of the rods 23 and is provided with an oversized aperture, as shown in. Fig. 3, through which the other rod extends. One of the discs, for example the disc 33, engages the cylindrical conductor 21. The length of the system, affects the tuning of the device only indirectly and the position of the discs 33 and 34 may be varied to obtain the optimum operating condition.
The heating current for the cathode may be supplied from a suitable source, such as a battery, connected between the leading-in conductors 23, one terminal of the source being grounded. Suitable potentials may be applied to the anode and control electrode by suitable sources, such as batteries, connected to the raised portion 13 of the anode and to the rod I' l respectively, one terminal of each of these sources also being grounded.
Although in the specific embodiment of the invention shown and described. the anode is provided with two grooves or recesses in which cath- The conductor 26 prefportion ode and control electrode elements are disposed, it will be understood, of course, that it may be provided with a diflerent number of grooves or recesses, each having therein a cathode and a control electrode element. It will be understood also that various modifications may be made in the specific structure shown and described without departing from the scope and spirit of the invention as defined in the appended claims.
What is claimed is:
1.- An electron discharge device comprising an enclosing vessel including vitreous end portions and an intermediate cylindrical metallic portion, said metallic portion having a plurality of recesses in its inner wall and serving as the anode of the device, a support extending from one of said end portions, a plate member carried by said support and having edges adjacent said recesses, helical grids secured to said edges and disposed in said recesses, a plurality of supports extending from the other of said end portions, and filaments carried by said second supports and disposed within said grids.
2. An electron discharge device comprising an enclosing vessel including a vitreous portion and a metallic portion, said metallic portion serving as an electrode of the device, an electrode within said envelope and cooperatively disposed with respect to said metallic portion, a leading-in conductor for said second electrode extending from said vitreous portion, and a hollow conductor encampassing said first conductor and said vitreous portion and portions of said metallic portion.
3. An electron discharge device comprising an enclosing vessel having vitreous end portions and an intermediate metallic portion constituting the anode of the device, a control electrode and a cathode within said vessel, 9. leading-in conductor for said cathode extending from one of said end portions, and a leading-in conductor for said control electrode extending from the other of said end portions, and tubular conductors encompassing said end portions and coupling said anode with said leading-in conductors.
4. An electron discharge device comprising an enclosing vessel including a vitreous portion and a metallic portion forming an electrode of the device, another electrode within said enclosing vessel, a leading-in conductor for said second electrode extending from said vitreous portion, a tubular conductor encompassing said first conductor and a part of said metallic portion, and a conductor insulated from and extending through said tubular conductor and having a portion in proximity to said leading-in conductor.
5. An electron discharge device comprising an enclosing vessel having vitreous end portions and a metallic portion serving as the anode of the device, a cathode and a control electrode within said anode, leading-in conductors for said cathode extending through one of said end portions, a leading-in conductor for said control electrode extending through the other of said end portions, a tubular conductor encompassing said first conductors and a portion of said anode, a metallic member slidably contacting with said tubular conductor and one of said first conductors, another tubular conductor encompassing a of said anode and the leading-in conductor for said control electrode, and a metallic conductor slidably contacting with said second tubular conductor and said control electrode leading-in conductor.
6. An electron discharge device comprising an enclosing vessel having a portion serving as an anode, a cathode, a control electrode, means carried by said vessel and disposed adjacent one end thereof for varying the capacitance and inductance between said anode and said control electrode, and means carried by said vessel and disposed adjacent the opposite end thereof for varying the capacitance and inductance between said cathode and said anode.
7. An electron discharge device comprising a pair of electrodes, a leading-in conductor extending from one of said electrodes, a metallic member in juxtapositionto said conductor and the other of said electrodes, and means electrically connecting said conductor and said memher, said means being movable along said conductor and said member whereby the inductance andcapacitance between said electrodes may be varied.
8. An electron discharge device comprising an anode, a cathode, and a. control electrode, a leading-in conductor extending from said cathode, a leading-in conductor extending from said control electrode, means including a tubular metallic member encompassing said first conductor and a portion of said anode and forming a distributed constant system therewith, and means including another tubular metallic member encompassing said second conductor and another portion oi said anode and forming a distributed constant system therewith. a
9. An electron discharge device in accordance with claim 8 including means for varying the length of said second distributed constant system.
AR L. S.
US747139A 1934-10-06 1934-10-06 Electron discharge device Expired - Lifetime US2044369A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US747139A US2044369A (en) 1934-10-06 1934-10-06 Electron discharge device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US747139A US2044369A (en) 1934-10-06 1934-10-06 Electron discharge device

Publications (1)

Publication Number Publication Date
US2044369A true US2044369A (en) 1936-06-16

Family

ID=25003804

Family Applications (1)

Application Number Title Priority Date Filing Date
US747139A Expired - Lifetime US2044369A (en) 1934-10-06 1934-10-06 Electron discharge device

Country Status (1)

Country Link
US (1) US2044369A (en)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2420314A (en) * 1943-04-26 1947-05-13 Sperry Gyroscope Co Inc High-frequency resonator-tube
US2423443A (en) * 1942-12-31 1947-07-08 Bell Telephone Labor Inc High power electronic discharge device for generating ultra high frequency radiations
US2435984A (en) * 1944-06-02 1948-02-17 Raytheon Mfg Co Tunable magnetron
US2449090A (en) * 1943-02-11 1948-09-14 Raytheon Mfg Co Temperature compensated magnetron
US2450629A (en) * 1944-03-14 1948-10-05 Gen Electric Ultra high frequency magnetron generator
US2456579A (en) * 1942-10-30 1948-12-14 Rca Corp Electron discharge device for ultra high frequencies
US2533280A (en) * 1943-03-16 1950-12-12 Int Standard Electric Corp Multiunit vacuum tube
US2558021A (en) * 1939-03-08 1951-06-26 Univ Leland Stanford Junior Thermionic vacuum tube and circuit
US2655616A (en) * 1944-05-24 1953-10-13 English Electric Valve Co Ltd Magnetron
US2660667A (en) * 1943-02-23 1953-11-24 Bell Telephone Labor Inc Ultrahigh frequency resonator
US3114044A (en) * 1959-09-30 1963-12-10 Westinghouse Electric Corp Electron multiplier isolating electrode structure
US3122671A (en) * 1962-01-31 1964-02-25 John M Bennett Mount structure for filamentary cathodes

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2558021A (en) * 1939-03-08 1951-06-26 Univ Leland Stanford Junior Thermionic vacuum tube and circuit
US2456579A (en) * 1942-10-30 1948-12-14 Rca Corp Electron discharge device for ultra high frequencies
US2423443A (en) * 1942-12-31 1947-07-08 Bell Telephone Labor Inc High power electronic discharge device for generating ultra high frequency radiations
US2449090A (en) * 1943-02-11 1948-09-14 Raytheon Mfg Co Temperature compensated magnetron
US2660667A (en) * 1943-02-23 1953-11-24 Bell Telephone Labor Inc Ultrahigh frequency resonator
US2533280A (en) * 1943-03-16 1950-12-12 Int Standard Electric Corp Multiunit vacuum tube
US2420314A (en) * 1943-04-26 1947-05-13 Sperry Gyroscope Co Inc High-frequency resonator-tube
US2450629A (en) * 1944-03-14 1948-10-05 Gen Electric Ultra high frequency magnetron generator
US2655616A (en) * 1944-05-24 1953-10-13 English Electric Valve Co Ltd Magnetron
US2435984A (en) * 1944-06-02 1948-02-17 Raytheon Mfg Co Tunable magnetron
US3114044A (en) * 1959-09-30 1963-12-10 Westinghouse Electric Corp Electron multiplier isolating electrode structure
US3122671A (en) * 1962-01-31 1964-02-25 John M Bennett Mount structure for filamentary cathodes

Similar Documents

Publication Publication Date Title
US2169396A (en) Signal-translating apparatus
US2416565A (en) High-frequency electronic device
US2044369A (en) Electron discharge device
US2692372A (en) Wide band radio frequency choke coil
US2108900A (en) Ultrashort wave oscillation generator circuit
US2342896A (en) Electron discharge device and circuit
US2446017A (en) Ultra high frequency electric discharge device and cavity resonator apparatus therefor
US2063341A (en) Electron discharge device
US2402600A (en) Electron discharge device
US2412998A (en) Electron discharge device
US2750535A (en) Electron discharge tubes
US2489872A (en) Envelope and electrode mounting structure for electric discharge devices
USRE15278E (en) Electron-discharge apparatus
US2465801A (en) Ultra high frequency apparatus
US2081415A (en) Electron emitter
US2444242A (en) Magnetron
US2445992A (en) Electric discharge device for space resonant circuits
US3247420A (en) Distributed amplifier with inductanceconnected anode segments
US2209923A (en) Magnetron
US3317785A (en) Magnetron assembly having dielectric means, external to envelope, for setting the center operating frequency
US2428609A (en) High-frequency electric discharge device
US2573397A (en) Mount for electron discharge devices
US2060508A (en) Short wave oscillator
US2139685A (en) Electron discharge device
US3177393A (en) Cathode for an electric discharge tube