US3813571A - Insulated cathode gun device - Google Patents

Insulated cathode gun device Download PDF

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Publication number
US3813571A
US3813571A US00349157A US34915773A US3813571A US 3813571 A US3813571 A US 3813571A US 00349157 A US00349157 A US 00349157A US 34915773 A US34915773 A US 34915773A US 3813571 A US3813571 A US 3813571A
Authority
US
United States
Prior art keywords
cathode
heat
heat shield
shield
support member
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
US00349157A
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English (en)
Inventor
A Basiulis
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.)
Raytheon Co
Original Assignee
Hughes Aircraft Co
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 Hughes Aircraft Co filed Critical Hughes Aircraft Co
Priority to US00349157A priority Critical patent/US3813571A/en
Priority to GB1269574A priority patent/GB1433454A/en
Priority to NL7404192.A priority patent/NL163056C/nl
Priority to DE2415153A priority patent/DE2415153B2/de
Priority to FR7411221A priority patent/FR2224867B1/fr
Priority to JP49039569A priority patent/JPS503564A/ja
Application granted granted Critical
Publication of US3813571A publication Critical patent/US3813571A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/04—Cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment

Definitions

  • a traveling wave tube includes an electron gun assembly and a collector assembly coupled together by a slow-wave structure.
  • the electron gun assembly emits a stream of electrons which travels through the slowwave structure and is collected by the collector assembly.
  • the stream of electrons is caused to interact'with a propagating electromagnetic wave in a manner which amplifies the electromagnetic energy.
  • the electromagnetic wave is propagated along the slow-wave structure, such as a conductive helix wound about the path of the electron stream.
  • the slow-wave structure provides a path of propagation for the electromagnetic wave such that the traveling wave effectively propagates at nearly the velocity of the'electron stream.
  • An electron gun assembly may include a cathode heater, a cathode electrode, a focusing electrode, an
  • the cathode electrode is usually a tubular member having an electron emissive or dispensing cap commonly called a cathode at one end-
  • the cathode heater may be any convenient shape such as a helix, for example, that fits into the cavity of the cathode electrode.
  • the focusing electrode, disposed between the cathode electrode and the slowwave structure, is also a tubular member to which an electric field may be applied for focusing the electron stream emitted from the cathode electrode.
  • An accelerating anode may be used to accelerate the electrons in the stream before the-electrons enter the slow-wave structure.
  • the above-mentioned electrical components are positioned in a supporting structure which is attached to one end of the slow-wavestructure.
  • Thermionic emission from the cathode takes place when the cap is heated to approximately 1,000C by the cathode heater. Along with the cathode heater and the cathode being heated to 1,000C the other components and the support structure are also heated to approximately the cathode temperature by both radiation and conduction from the cathode electrode. Since essentially the entire electron gun assembly is heated by the cathode heater to a very high temperature, sufficient power must be supplied to the cathode heater to maintain the cathode at the proper thermionic emission temperature. The requirement of additional power to maintain the entire cathode gun assembly at an elevated temperature may place excessive demands on a limited power source such as in a space vehicle.
  • heating of components other than the cathode heater and the cathode induces problems of alignment of these other electrodes, i.e. metals expand causing position changes of these various electrodes making alignment difficult. High temperature operation may also tend to induce metal fatigue resulting in a shortened life for the cathode gun assembly.
  • a cathode gun device includes a cathode mounted to one end of a tubular cathode support member.
  • a cathode heater is provided within the tubular cathode support member with terminals extending away from the cathode end,
  • a first composite heat shield, comprising a plurality of concentric layers is disposed about substantially the outer surface of the cathode support member.
  • a first layer of the first composite heat shield is afiber metal having low thermal conductivity.
  • a second layer is a thin polished foil made of a low thermal conductivity, low emissivity metal sheet.
  • a second composite heat shield made of a plurality of flat layers is disposed about the end opposite the cathode end of the cathode support member.
  • An electrical insulating spacer is provided extending through the second heat shield for providing electrical insulation between one heater terminal and the second heat shield.
  • a first layer of the second composite heat shield is a thin polished foil made of a low thermal conductivity, low emissivity metal sheet.
  • a second layer is a fiber metal having low thermal conductivity.
  • a cathode electrode device may be seen to include a cathode electrode 10, a heater electrode 20, and a first heat reflective shield 30 and'a second heat reflective shield 40.
  • the cathode heater 20 heats the cathode electrode 10 to thermionic emission temperature, and the heat reflective shields 30 and 40 reflect back some heat that is radiated by the cathode electrode 10.
  • the cathode electrode includes an electron emitting cathode cap 11, a cathode support member 14, and a cathode sleeve 16.
  • the electron emissive cathode cap hereinafter. called cathode 11, is a cylindrically shaped disk with a concave surface at one end 12 from which electrons are emitted and a flat surface at the other end 13.
  • the cathode 11 may be made of a material suitable for electron emission when heated to the proper thermionic temperature such as molybdenum or tantalum, for example.
  • the flat end 13 of the cathode 11 is mounted to one end of a tubular cathode support member 14 which may be made of a metal such as mo-' lybdenum.
  • the other end 15 of the cathode support member 14 is mounted to a tubular cathode sleeve 16 that is made of a material having a lower thermal conductivity than the cathode support 14 such as tantalum.
  • a heat reflective shield 30 is disposed about the circumference of the cathode 11, the cathode support member 14, and, is attached to the cathode sleeve 16.
  • the heat reflective shield 30 is'tubular in shape with a substantial portion of its length having an inside diameter larger than the cathode 11 or the cathode support member 14 such that the heat reflective shield 30 is spaced away from cathode l1 and the cathode support 14.
  • One end of the heat reflective shield 30 has a sufficiently reduced'diameter to be attached onto the cathode sleeve 16 by any convenient method suchas spot welding, for example, along the circumference, one point of which is indicated as point 31.
  • the cathode heater 20 for heating the cathode 11 to thermionic emission temperature of approximately 1,000C.
  • the cathode heater 20 is in close proximity to the cathode 11 for maximum heat transfer to the cathode 11.
  • the heater 20 includes a hellical coiled wire forming the heater element 21 and terminals'22 and 23.
  • An insulating structure 24, such as a suitable high temperature potting compound, may be used tospace the cathode heater 20 away from the cathode 11 and the cathode support 14. Terminals 22 and 23 of the cathode heater element 21 may extend beyond the'cathode sleeve 16 for convenient electrical connection through the disk shaped ceramic insulator 25.
  • a second heat reflective shield 40 is disposed within the cathode electrode 10 near the region of the end 17.
  • the shield 40 is comprised of three individual heat reflective shields 41 that are 0.0002 inch thick discs having polished surfaces and are made of a low emissivity material such as molybdenum, for example.
  • Each disc has 2 holes, diametrically opposed on the face of the disc, through which tubular spacers 42 may be passed for separating the individual discs from each other and for providing electrical insulation between the shield 40 and the heater terminals 22 and 23.
  • the shield 30 will then radiate this heat energy to its surroundings; It is thereforeapparent that even using such a heat shield there is still loss of heat and undue consumption of power due to unnecessary heating of the entire electron gun assembly by the cathode electrode 10. Also, such a heat reflective shield 30 is unstable during period of mechanical vibration. Since one end of the heat shield 30 is unsupported, it is free to oscillate in response to mechanical vibration and may cause mechanical and electrical malfunction of the electron gun assembly by shorting out some of the neighboring electrodes and structure.
  • a cathode gun device may be seen to include a cathode electrode 10 containing a cathode heater 20, both as described in FIG. 1 above, and a composite heat shield disposed about the substantial outer'surface of the cathode electrode 10.
  • the composite heat shield 50 is composed of a plurality-of layers of thermal insulators and reflectors in an alternate arrangement'.
  • the first layer, placed closest to the cathode electrode 10 surface, is a high temperature thermal insulating heat shield 51.
  • the shield 51 may be a sintered metal or a foamedmetal material such as nickel,
  • Fiber metal can withstand the high temperatures necessary for thermionic emission and hasa relatively low thermal conductivity.
  • Mean free path between fibers refers to the distance along a given fiber between contact to other fibers.
  • a cross-sectional area a 'flber'to the heat flow in cm L mean free path or length of the fiber in cm;
  • a minimum A IL ratio is obtained by minimizing the cross-sectional area A and maximizing the length L. A, is minimized when there is a small diameter fiber,
  • insulation materials including, for example, a foamed metal and the invention is not limited to the above-described fiber metal.
  • the heat reflective shield 52 may be a thin sheet metal foil made of low thermal conductivity and low emissivity material such as molybdenum, for example.
  • the foil having a thickness of about-0.0002 inch is preferred for its relatively low mass and the resulting low heat capacity.
  • a heat shield with a polished inner surface 52A will reflect a substantial portion of radiant heat incident to'that surface andif it has low emissivity, a small amount of heat will be radiated by the outer surface 52B.
  • a third layer may be wrapped around the heat reflective shield 52, as described above, for further thermal insulation.
  • the third layer is a thermal insulator heat
  • another embodiment according to the present invention includes a cathode electrode 10, a heater electrode 20, encapsulated in an insulating structure 24, and a heat shield 60.
  • the cathode electrode 10, the heater electrode 20 and the insulating structure 24 around the heater element 21 are similar to the items in FIGS. 1 and 2 having-the same reference designations.
  • Heater terminals 22 and 23 extend outward from the heater element 21 through the ceramic insulator disk 25, and beyond the end 17 of the cathode electrode forv making an electrical connec tion.
  • Tubular electrical insulating spacers 70 having a shouldered end 71 are slipped over the terminals 22 and 23 with the shouldered end facing away from the heater element 21.
  • the spacer 70 may be made of any suitable high temperature material that is capable of I withstanding temperatures in excess of 1,000C such as shield 51 similar to the first layer'heat shield51 described above.
  • A' fourth layer may be wrapped about the third layer forming a heat reflective shield 52, similar to the second layer heat shield 52 described above, for providing additional insulation.
  • a composite heat shield 50 may be composed of as many individual-heat shields 51 and 52 as may be required or as there is room for in the cathode gun assembly.
  • the composite heat shield 50 may be considered as being made up of at least one 51 and one 52 shield.
  • the heat shields 51 and 52 may be interchanged with each other and they need not be in the order described.
  • the composite heat shield 50 may be fastened to the cathode electrode 10 by any one of a number of methods.
  • the individual shields 51 and 52 may be attached one at a time by spot welding or by placing a tubular sleeve 53, shown in dashed lines, over the outer layer.
  • Another convenient method to fasten the heat shield 50 is to assemble the individual shields-51 and 52 in a flat pattern and then sinter the layers together in a vacuum at a temperature between 900 and l,000C.
  • the sintered composite heat shield 50 may then be wrapped about the cathode electrode 10 and spot welded in place.
  • FIG. 3 the top view of the invention according to FIG. 2 is illustrated in FIG. 3.
  • the cathode electrode 10 is seen surrounded by the heat shield 50 which is composed of the individual shields 51 and 52.
  • the heat shield 50 is attached to the cathode electrode 10 by spot welding along the line extending downward (into the drawing) from the points 541 and 55.
  • An alternative method of mounting the heat shield 50 is by placing a sleeve 53 shown in the dashed line, around the shield 50, thereby holding the shield 50 in place by friction.
  • a disk-like composite heat shield 60 having two diametrically opposed holes 67 extending from face to face of the disk is placed over the two electrical insulating spacers 70.
  • the shoulder 71 on the spacer 70 is larger than the diameters of the holes 67 in the heat shield 60 so that the shoulder 71 rests against the face of the heat shield 60 that faces the heater element 21.
  • Tubular electrical insulating spacers 75 having larger outside diameters than the diameters of the holes 61 in the heat shield are slipped over the heater terminals 22 and 23 and rest against the back face of the heat shield 60.
  • the spacer 75 may be made of the same material as the spacer 70.
  • the heat shield and the spacers and are held in place on the heater terminals 22 and 23 by retainer bars 66 welded at the shouldered endof spacers 70 and next to the spacers 75.
  • the composite heat shield 60 is composed of a plurality of layers of thermal insulators and reflectors in an alternate arrangement similar to the arrangement of the heat shield 50.
  • the first layer, closesttothe heater element 21, is a heat reflective shield 61 which is made of the same material as the heat reflective shield 52 described in FIG. 2 above.
  • the second layer is an insulating shield 62 that is made of the same material as the shield 51 described in FIG. 2 above.
  • the third layer is another heat reflective shield 61, the fourth layer is a thermal insulating shield 62, and the fifth layer is a heat reflective shield 61. It is pointed out that additional shields 61 and 62 may be used to improve the insulating qualities of the heat shield 60.
  • the combination of at least one shield 61 and one shield 62 may be considered as an elemental heat shield 60.
  • the operation of the invention will be described in relation to the embodiments of FIGS. 2, 3, and 4. Power is applied to the cathode heater terminals 22 and 23 causing the'cathode heater to attain a thermionic emission temperature of approximately l,000C.
  • the cathode heater 20 heats the entire cathode electrode 10 and its supporting structure to about the same temperature.
  • the exterior surfacesof the cathode electrode 10 will radiate heat to its surroundings and the composite heat shield 50 will substantially reduce the amount of heat that is radiated away.
  • the first layer of the composite heat shield 50 is the thermal insulating shield 51 which has a low thermal conductivity and therefore conducts only a small amount of heat to the second layer, i.e., the thermal reflectiveshield 52.
  • the reflective shield 52 also being of low thermal conductivity will conduct only a small amount of heat from its inside sur' face to its outside surface.
  • the third and fourth layers of the heat shield 50 function substantially as described for the first and second layers 51 and 52.
  • heat shield 50 is mounted directly to the cathode electrode 10 along its entire length, it is sufficiently supported to prevent it from vibrating and causing any short circuits while providing substantial thermal insulation.
  • the cathode heater 20 will radiate heat axially to the cathode electrode 10 and the composite heat shield 60 will substantially reduce the amount of heat being radiated from the end 17 of the cathode electrode 10.
  • the operation of the heat shield 60 is substantially similar to the operation of the heat shield 50 as described above. Since the heatreflective'shields 61 are separated by the rigid thermal insulating layer 62, they are not free to vibrate and the possibility of the heater terminals 22 and 23 being. electrically shorted to each other is substantially eliminated.
  • the present invention provides a simple and reliable insulated cathode electrode. Moreover, the device may reduce the input power required to maintain the cathode v at thermionic emission temperature by a substantial amount. In fact, a cathode electrode according to FIGS. 2 and 4 has been constructed andtested and it was found to have an increased operating efficiency of percent.
  • a cathode gun device comprising:
  • a cathode for being heated to thermionic emission temperature
  • a heater electrode being mounted within said cathode support member
  • a first heat shield having a heat reflective surface and having a low emissivity being mountedabout the end oppositethe cathode
  • a cathode gun device according to claim 1 wherein: said second'heat shield is a fiber metal material. 1 v
  • a cathode gundevice comprising:
  • a cathode gun device comprising: i
  • a cathode for heating to thermionic emission temperature
  • a heater electrode being mounted within said cathode support member
  • a first heat shield having a heat reflective surface and having a low emissivity being mountedabout said cathode support member
  • a cathode gun device according to claim 4 wherein: said second heat shield is a fiber metal material.

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  • Microwave Tubes (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
  • Plasma Technology (AREA)
  • Solid Thermionic Cathode (AREA)
US00349157A 1973-04-09 1973-04-09 Insulated cathode gun device Expired - Lifetime US3813571A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US00349157A US3813571A (en) 1973-04-09 1973-04-09 Insulated cathode gun device
GB1269574A GB1433454A (en) 1973-04-09 1974-03-21 Thermionic emission cathode arrangement
NL7404192.A NL163056C (nl) 1973-04-09 1974-03-27 Kathode-inrichting voor thermische emissie.
DE2415153A DE2415153B2 (de) 1973-04-09 1974-03-29 Glühkathodenanordnung
FR7411221A FR2224867B1 (nl) 1973-04-09 1974-03-29
JP49039569A JPS503564A (nl) 1973-04-09 1974-04-09

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00349157A US3813571A (en) 1973-04-09 1973-04-09 Insulated cathode gun device

Publications (1)

Publication Number Publication Date
US3813571A true US3813571A (en) 1974-05-28

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ID=23371143

Family Applications (1)

Application Number Title Priority Date Filing Date
US00349157A Expired - Lifetime US3813571A (en) 1973-04-09 1973-04-09 Insulated cathode gun device

Country Status (6)

Country Link
US (1) US3813571A (nl)
JP (1) JPS503564A (nl)
DE (1) DE2415153B2 (nl)
FR (1) FR2224867B1 (nl)
GB (1) GB1433454A (nl)
NL (1) NL163056C (nl)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4587455A (en) * 1982-10-12 1986-05-06 Hughes Aircraft Company Controlled porosity dispenser cathode
EP0204541A2 (en) * 1985-06-04 1986-12-10 English Electric Valve Company Limited Discharge tube apparatus
US5698855A (en) * 1995-07-17 1997-12-16 Nec Corporation Electron gun assembly with improved heat resistance
EP3699947A3 (en) * 2019-02-21 2020-11-25 Varex Imaging Corporation X-ray tube emitter

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS51112166A (en) * 1975-03-27 1976-10-04 Matsushita Electric Ind Co Ltd Impregnated cathode
JPS52126919A (en) * 1976-04-17 1977-10-25 Uemura Koichi Method of and apparatus for mounting underground girder under structure
JPS5458344A (en) * 1977-10-19 1979-05-11 Hitachi Ltd Thermal electron radiation cathode
JPS6036056B2 (ja) * 1979-06-21 1985-08-17 株式会社東芝 陰極構体

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2518879A (en) * 1945-02-03 1950-08-15 Kenneth J Germeshausen Hydrogen thyratron
US2888592A (en) * 1954-07-22 1959-05-26 Gen Electric Cathode structure
US2899591A (en) * 1959-08-11 Electrical heating device
US3204140A (en) * 1961-07-10 1965-08-31 Gen Electric Hot cathode electron tube

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09334A (ja) * 1995-06-19 1997-01-07 Tsubaki Kk ヘアーカーラー

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2899591A (en) * 1959-08-11 Electrical heating device
US2518879A (en) * 1945-02-03 1950-08-15 Kenneth J Germeshausen Hydrogen thyratron
US2888592A (en) * 1954-07-22 1959-05-26 Gen Electric Cathode structure
US3204140A (en) * 1961-07-10 1965-08-31 Gen Electric Hot cathode electron tube

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4587455A (en) * 1982-10-12 1986-05-06 Hughes Aircraft Company Controlled porosity dispenser cathode
EP0204541A2 (en) * 1985-06-04 1986-12-10 English Electric Valve Company Limited Discharge tube apparatus
EP0204541A3 (en) * 1985-06-04 1987-08-12 English Electric Valve Company Limited Discharge tube apparatus
US4805180A (en) * 1985-06-04 1989-02-14 English Electric Valve Company Limited Discharge tube apparatus
US5698855A (en) * 1995-07-17 1997-12-16 Nec Corporation Electron gun assembly with improved heat resistance
EP3699947A3 (en) * 2019-02-21 2020-11-25 Varex Imaging Corporation X-ray tube emitter

Also Published As

Publication number Publication date
JPS503564A (nl) 1975-01-14
NL163056C (nl) 1980-07-15
DE2415153A1 (de) 1974-10-17
FR2224867A1 (nl) 1974-10-31
FR2224867B1 (nl) 1977-09-30
GB1433454A (en) 1976-04-28
DE2415153B2 (de) 1975-06-12
NL7404192A (nl) 1974-10-11

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