US2253145A - Gaseous conduction device - Google Patents

Gaseous conduction device Download PDF

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Publication number
US2253145A
US2253145A US130268A US13026837A US2253145A US 2253145 A US2253145 A US 2253145A US 130268 A US130268 A US 130268A US 13026837 A US13026837 A US 13026837A US 2253145 A US2253145 A US 2253145A
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United States
Prior art keywords
cathode
tube
caesium
anode
vapor
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Expired - Lifetime
Application number
US130268A
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English (en)
Inventor
Charles G Smith
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Raytheon Co
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Raytheon Manufacturing Co
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Filing date
Publication date
Priority to FR632685D priority Critical patent/FR632685A/fr
Priority claimed from US111278A external-priority patent/US2077961A/en
Priority to GB8466/27A priority patent/GB271419A/en
Application filed by Raytheon Manufacturing Co filed Critical Raytheon Manufacturing Co
Priority to US130268A priority patent/US2253145A/en
Application granted granted Critical
Publication of US2253145A publication Critical patent/US2253145A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J17/00—Gas-filled discharge tubes with solid cathode
    • H01J17/38—Cold-cathode tubes
    • H01J17/40—Cold-cathode tubes with one cathode and one anode, e.g. glow tubes, tuning-indicator glow tubes, voltage-stabiliser tubes, voltage-indicator tubes

Definitions

  • This invention relates to devices of .the type having a tube containing electrodes separated by a gaseous medium, preferably at a low pressure, and particularly to gaseous conduction rectifiers, objects of the invention being to produce a device of this type having low total voltage loss, little if any cathode disintegration, small reverse current when used as a rectifier, little if any gaseous clean-up, protection against deleterious effects of ions and radiation upon the insulating material embodied in the tube, low starting voltage, stability of operation, and generally to improve devices of the aforesaid type.
  • the invention comprises a gaseous conduction tube having an anode, a cathode, and a cathode coating of caesium or other alkali metal or alkali earth metal or other material characterized by a low work function, a low vaporizing temperature, and/or being highly electropositive, the cathode being constructed and arranged to operate at a temperature below that at which the coating is driven oil and the anode being constructed and arranged to operate at a temperature above said temperature, whereby coating material deposited upon the anode during manufacture or during operation is driven off and the action of the material is confined to the cathode.
  • the tube when used as a rectifier, for example, permits current to flow freely when the cathode is negative while permitting practically no reverse current when the anode is negative. While some of the material may be driven off the cathode, particularly when operating under conditions which cause the discharge to are from a hot-spot, the cathode is sufficiently large to permit the discharge continuously to shift to coated areas.
  • the cathode coating serves to facilitate the gaseous conduction and to lower the potential drop in the region of the cathode, thereby lowering the total potential drop between cathode and anode.
  • the cathode By making the cathode large it can be maintained at an average temperature well below that at which the coating is rendered ineffective and by making the cathode hollow the coating material which is driven off may redeposit upon other areas so that even in the case of a wander- I ing arc each spot from which the coating is driven oif is soon recoated by material driven off other spots.
  • the construction of the cathode and the gas filling may be correlated to maintain the discharge without a hot-spot on the cathode, in some cases in the form of a flow discharge and in other cases in the form of an are without a hot-spot, as disclosed in Patent No. 1,929,123, dated October 3, 1933.
  • the anode may be heated by an auxiliary source of heat, but the preferred way of keeping the anode free from the coating material is to make it so small that it normally operates at a temperature above that at which the coating will adhere.
  • the cathode coating may be very thin, even to the extent of being invisible. Indeed, for certain purposes satisfactory results may be obtained with the coating in the form of a layer of the vapor of the material adsorbed on the surface of the cathode, the vapor not only increasing the electron emission when deposited in or on the surface of the cathode but also affording a copius supply of ions in the gap between cathode and anode by virtue of its low ionization voltage.
  • caesium has the advantage of a low vaporization temperature, this metal having an appreciable vapor pressure even at room temperature. 4
  • the cathode coating adheres better and is more effective if the cathode surface is rough.
  • the cathode of carbon is more electronegative than most surfaces and therefore serves better to bind the caesium or other electropositive material to its surface.
  • the cathode particularly when formed of metal instead of carbon, may be coated with an oxide, for example, an oxide of an alkali earth metal, or with chromium, before applying the electropositive material, such as caesium. Or, the cathode, if formed of metal, may merely be oxidized to make its surface highly electronegative.
  • the invention comprises the use of an inert gas with caesium or other of the aforesaid materials which have vapor pressures too low, at normal tube temperatures, alone to maintain gaseous conduction.
  • the inert gas serves for starting purposes, and when ionized by the discharge, its radiation ionizes the vapor of caesium or the like, affording a very low voltage drop.
  • neon is particularly effective for the reason that the radiation from glowing neon is a powerful ionizing agency for caesium vapor.
  • This combination of gas and vapor is particularly useful in gaseous rectifiers since the vapor alone, at temperatures high enough to produce suificient vapor pressure" to maintain conduction, would tend to permit current flow in both directions between cathode and anode.
  • the anode may extend through a restricted opening in the cathode with means adjacent the opening to obstruct the small amount of radiation which would otherwise emanate through the opening, and the spacing between the anode and cathode opening and/or between one or both electrodes and the obstructing means may be restricted substantially to the mean free path of electrons in the gas for insulation purposes.
  • the discharge may be caused to assume the characteristics of arc without heating the cathode to the usual high temperature required to maintain an arc by thermionic emission from a hot-spot, as more fully explained in the aforesaid application, Serial No. 111,279, filed May 24, 1926.
  • Still another advantage in making the cathode hollow consists in that the coating material which is vaporized or otherwise disloged from any area of the cathode is redeposited upon other areas of the interior surface of the hollow cathode, thereby conserving the coating material and restricting its escape to other parts of the tube where its effect is deleterious.
  • a highly electropositive material such as caesium
  • Fig. 1 is an axial section of a tube
  • Fig, 2 is a section on line 22 of Fig. 1;
  • Fig. 3 is a section on line 33 of Fig. 1;
  • Fig. 4 is a side elevation of the tube shown in Fig. 1 before it is completed
  • Fig. 5 is a side elevation of a cathode-anode assembly as viewed from the left of Fig. 1;
  • Fig. 6 is a detail view of the filling capsule.
  • Fig. '7 is a detail view of a modification.
  • pose of illustration comprises a tube l of lime glass or other suitable material, a cathode 2, two anodes 3, leads 4 to the anodes respectively, a lead I to the cathode, a shield 6, a support I for the' shield, and a support 8 for the cathode.
  • the cathode comprises a cylindrical wall 8 and ends [0 and II.
  • One of the ends may be formed integrally with the cylindrical wall, but they are both preferably formed separately and mounted over the ends of the wall.
  • the ends may have cylindrical flanges which fit over the cylindrical wall as shown at l0 and H' in Fig. 5, or they may be in the form of disks as shown in Fig. 1. In either case they are preferably welded to the cylindrical wall, either continuously around the periphery or at circumferentially spaced spots.
  • the lower end II has two openings with exterior flanges surrounding the reduced ends of the anodes in spaced relation thereto, the outer diameter of the flanges preferably being approximately equal to the diameter of the larger portions of the Mounted within the cathode are rings or washers 12 having integral flanges to hold them in spaced relation, the spaces between the washers being very small to provide crevices from which the electronic discharge emanates more freely than from a flat surface.
  • the cathode is approximately one inch in diameter, thus indicating the order of spacing between the washers l2.
  • the washers may be mounted in the cathode in any suitable manner, as for example, merely by a tight fit within the cylindrical portion of the cathode.
  • the interior surface of the cathode is preferably rough, and is preferably coated with caesium or other material having a low work function.
  • the rough surface may be provided merely by oxidizing the surface of the cathode or by first coating it with carbon or with a layer of oxide, as elsewhere explained. Such a surface will adsorb more of the caesium or other electropositive vapor than will a smooth surface.
  • the cathode may be formed of nickel, iron, or more refractory metal, such as tungsten or molybdenum, or it may be formed of carbon, in which case it naturally has a rough surface without being coated on the inside, although even in that case it may have a coating of oxide.
  • the anodes may be formed of nickel, iron, or more refractory metal, and, as illustrated in Fig. 1, the lead-in wires .4 extend through axial openings in the ends and are secured to the anodes at the upper ends by being pinched in the tips of the anodes. As shown in Fig. 1, the anodes rest upon hollow protuberances upon the reentrant stem 13 of the tube l.
  • the shield 6 is preferably formed from a single piece of sheet metal, as shown in Fig. 3.
  • the space between the shield and each anode, as well as between the shield and each flangeof the cathode, is preferably confined approximately to the mean free path of electrons in the gas, for insulation purposes.
  • the space between each cathode flange and each anode is also preferably of the same order for the same purpose.
  • the shield 6 not only serves for insulation purposes, but also obstructs radiation from the interior of the cathode to any part of the tube l, including the junction between the tube and the anode where disintegration would otherwise occur by interaction between the caesium and the tube material.
  • the air within the tube is preferably replaced with an inert gas, such as neon.
  • an inert gas such as neon.
  • the neon pressure may be' of the order of mm. while for higher voltage tubes the pressure should be somewhat lower.
  • the deposit of caesium or the like, above referred to, is indicated in Fig. 1 on the inside of the tube and on the inside of the cathode by stippling.
  • Fig. 4 One methodof filling the tube is illustrated in Fig. 4 wherein l4 indicates a pump connection. 15 connection to a source of inert gas, and iii an integral appendix on the tube l.
  • a metallic capsule ll containing ingredients which react to produce the metallic vapor, such as caesium.
  • this capsule may contain calcium and caesium chloride, the calcium being somewhat in excess of the amount necessary'to react with all of the caesium chloride to produce caesium.
  • the partition is formed as a wad of steel wool through which the ingredients may pass when melted or vaporized.
  • a similar wad is preferably placed at the mouth of the capsule normally to hold the materials in place.
  • the inert gas is I shut off and the tube is heated to drive off impurities.
  • the inert gas and caesium are admitted. While the inert gas may be'admitted first, it is preferably first to distill the caesium into the tube inasmuch as it passes in more free 1y at the lower pressure within the tube. After both the inert gas and the caesium or the like have been admitted into the tube, the connections are sealed oif at l8 and I9, as indicated in Fig. 1.
  • ingredients in the capsule I! may be caused to react in various ways, the best way of which I am aware is to heat the ingredients by current induced in the metallic capsule I! from a high frequency source, such as indicated at 20, outside the tube.
  • chloride melts at approximately 647 C. and calcium at about 810 0., the latter subliming readily at 725 C.
  • the whole tube or at least the capsule I1 is preferably heated only to approximately 600 C. to drive off impurities during the pumping operation, and subsequently to approximately at 850 C. to cause the ingredients to react to give off caesium vapor.
  • the capsule I! is mounted in an appendix, as shown in Fig.
  • caesium mounted in the body of the tube, as for example, on the cathode 9, as illustrated at II in Fig. 5, in which case the caesium vapor penetrates to the interior of the cathode through the restricted openings in the lower end of the cathode more readily. In this case the capsule is not removed.
  • the capsule i1 is mounted within the cathode, and may be heated either by current induced in the cathode by high frequency current around the tube or by passing a discharge between cathode and anodes.
  • This method has the advantage of depositing most of the caesium or the like upon the interior of the cathode; and by heating the'cathode hot enough, the coating material may be caused to combine chemically with the cathode, particularly if the latter is formed of nickel.
  • the cathode shown in Fig. 7, as well as that shown in Fig. 5, may have interior surfaces corresponding to washers l2 in Fig. 1. Instead of using calcium, magnesium may be used; and instead of caesium, potassium or the like may be used.
  • a unidirectional gaseous discharge tube comprising a hermetically sealed vessel containing a gaseous atmosphere arranged to be ionized to maintain a glow discharge, a cathode constituting a hollow chamber with an interior electrode surface enclosing a portion of said atmosphere in said vessel, the interior of said cathode chamber having an increased electrode surface formed of a plurality of closely-spaced, projecting wall portions constituting a plurality of narrow, intercommunicating cells terminating into a common space within said hollow chamber, and a small-area anode disposed outside said cells and arranged to maintain a'glow discharge through said atmosphere with the interior conducting surfaces of said cathode through said common space.
  • a crater cathode comprising a plurality of parallel disks having alined perforations forming the crater

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  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)
US130268A 1926-05-24 1937-03-11 Gaseous conduction device Expired - Lifetime US2253145A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
FR632685D FR632685A (enrdf_load_stackoverflow) 1926-05-24
GB8466/27A GB271419A (en) 1926-05-24 1927-03-28 Improvements in electric discharge devices
US130268A US2253145A (en) 1926-05-24 1937-03-11 Gaseous conduction device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US111278A US2077961A (en) 1926-05-24 1926-05-24 Gaseous conduction device
US130268A US2253145A (en) 1926-05-24 1937-03-11 Gaseous conduction device

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US2253145A true US2253145A (en) 1941-08-19

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US130268A Expired - Lifetime US2253145A (en) 1926-05-24 1937-03-11 Gaseous conduction device

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US (1) US2253145A (enrdf_load_stackoverflow)
FR (1) FR632685A (enrdf_load_stackoverflow)
GB (1) GB271419A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2650736A (en) * 1949-01-29 1953-09-01 Oliver B Curry Popcorn service
US2804563A (en) * 1954-01-19 1957-08-27 Machlett Lab Inc Electron tube generator
US2888592A (en) * 1954-07-22 1959-05-26 Gen Electric Cathode structure
US2890319A (en) * 1957-09-16 1959-06-09 Tung Sol Electric Inc Fast-heating hydrogen reservoir

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE755658C (de) * 1934-06-22 1953-08-10 Siemens & Halske A G Vorrichtung zum Einbringen von Fuellstoff in Gas- oder Dampfentladungsapparate

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2650736A (en) * 1949-01-29 1953-09-01 Oliver B Curry Popcorn service
US2804563A (en) * 1954-01-19 1957-08-27 Machlett Lab Inc Electron tube generator
US2888592A (en) * 1954-07-22 1959-05-26 Gen Electric Cathode structure
US2890319A (en) * 1957-09-16 1959-06-09 Tung Sol Electric Inc Fast-heating hydrogen reservoir

Also Published As

Publication number Publication date
FR632685A (enrdf_load_stackoverflow) 1928-01-13
GB271419A (en) 1928-05-03

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