US2436835A - Control circuit for gas discharge tubes - Google Patents

Description

Marh 2, v1,948.

CONTROL CIRCUIT FOR GAS DISCHARGE TUBES P. w. STUTSMAN 2,436,835

Filed May 6, 1944 ."5 Sheets-Sheet l f M M,

March 2, 1948. P. w. sT'UTsMAN 435,835

CONTROLCIRCUIT FOR GAS DISCHARGE TUBES Filed May 6, 1944 .5 Sheets-Sheet 2 March2, 1948. P. w. sTuTsMAN l 2,433,835

l lCONTROL CIRCUIT FOR GAS DISCHARGE TUBES Filed May 6, 1944 3 Sheets-Sheet 5 Patented Mar. 2, 1948 VPaul-W.lStutsman, Needham, Mass., assignor, by

.mesne assignments, to Raytheon VManufacturing Company, Newton 'Delaware Mass., av corporation of Application l May` 6, 1944 Serial vNo.-.53.4,1-4,94

6 Claims. (Cl. 315-60) 1 .'Ihis invention relates .to an 4electrical .system utilizing a gaseous ,discharge .relaytube which v atively fine mesh of'nickel wire.

conducts current between acatho'deand .anode' Vin response Yto a predetermined valueof signal voltage applied lto ,a control. grid or electrode.

An `object of this inventionto Ydevisesucha tube and system having -ahigh ,grid Virripedance and which operates ,reliably with very'low grid power.

Another objectistodevisesuch.a 'tube v`and l system which operate consistently under variable description vof .an exempliiication thereof,A reference being hadto the .accompanying V4drawings wherein:

Fig. 1 isa verticaleross-secton of one. form of my novel tube for.uselinmynovelsystem;

Fig. 2 is across-section taken .along .line 2-2 of.Fig. 1;

Fig. 3 isa circuit diagram opone embodiment of my novel system;

Fig. 4 is a Aset otcurves illustratingthefstandby oonditionsin the systemoFgB; vand Figs. 5 and .6 are `characteristic .curves .ofta tube built and operated Jin accordance .withmy invention. 1

The tubeasillustrated inlFigs. l .and2 .comprises a ysealed glass .envelope .-i .containing va glow .discharge .cathode "2, an anode .3, and sa pair of ycathanode .grids 4, `4 disposed on .opposite sides-of a control grid ,5. .Theenvelope I vis filled with. a .suitable ionizable .gasata substantialpressure. rFor example. a mixture .pf ',kr-.Vptonand nmat ,about;10.mm.=of mercurymay be uti- "The l.cathode 1 .is supported by ...a plurality .of .conductingsupport rods-5 sealedinthe. upper .end .of a press .1 .formed,-on fthe. reentrant .stem .8 of ,the envelope ..I. .The cathode 2 `.may be made ...of aribbon of-anckel alloy and coated with-barium carbonate fused onto :said .ribbon'in fairv ait-apressureof about 5mm, raf-.mercury vOne of the conductingrods .6 maybefprovided with a ,leadin conduetor 9 .extending .through .the r.press I and aiording an external electrical connection to the cathode.

The grids tand .5 "arejprefertm1-tmatie o1 a rel.

The .anode 3 may .also be made of a disc of nickel. If relatively small voltages are used between the cathode and anode, the electrodes 3, 4 and 5 may be made of .bright nickel. Under these conditions, voltages of about theorder of 14'5 volts or less .may .be used. However, where higher voltages are present, it is desirable that the surface of the electrodes 3, 4 and y5 be coated with a poor electronemissive material. Thus these electrodes are preferably earbonized .by being .coated with .a layer of finely divided carbon. The electrodes 3, 4 and 5.are each in'the form of a iiat disc supported betweena pair of insulating washers I0. ."Each of these insulating Washers is provided with a central. opening II so as .to create an electron discharge passage between the Vcathode 2 and the anodeB., "The insulating washers Ill are clamped together by aplurality of hollow rivets I2 which thus bind' the assembly of the electrodes 3, 4 and A5 together into .a compact unit. This unit is supported `on the reentrant stem .8 'by means of aypair of .wire standards I3 sealed in the4 press 1. The upper ends .of the standards t3 may be welded to two of therivets I2. .Each of the cathanodegrids A4'has welded thereto a vconducting tab whichiin'turn is welded to a conducting rod I4 likewise v.sealed inthe press 'I and `provided with .an external lead-ingconductor I5.. The rod I4, vasitprojects above the press 1, is .surroundedby avglass. sleeve I 6 soas to protect said Vrod I4 against Yundesirable discharges. The glass Ysleeve .IB ts snugly into corresponding openings .in the insulating washers I0. The -control'grid .flikewise has Welded thereto a conducting tab whichin turnis weldedto a conducting rod I1 likewise sealed inthe press 1 and ,provided with an eXternallead-in conductor I8. The rodI'I .is also surrounded by-.aglass sleeve I9.t .ting snugly into .corresponding openings in the washersi.. The purpose of the. sleeve I9 is simi- ,lar to .that `.described .in connection with the sleeve I5, In order to .cut o'if all discharge ,paths betweenthe electrodes, exceptvthrough the discharge ,openings l] .in the washers I0, an additional nsulating washer 20 is placed over thetop of vthe electrode assembly and isprovided with a. single central opening for y,thepurpose .of Yenabling ana/electricalconnectionto be. made to the anode L3. l;l1oweve1.,-the washer 20 .covers the openings in the washers-.I Uthrough which thesleeves .I-B and ltproject and also .covers .the .upper ends Vof ,the rivets I2. .Therwashers Illand Valso the washer ZlifitV snugly within theside wallsof the envelo'pe l.. .thewasher .20 .being .retained in place by coming into contact with the lower portion of the upper curved section of the inner walls of said envelope. The anode 3 has welded to its upper surface a conducting stub 2| to which is welded a flexible lead-in conductor 22. This lead-in conductor dis sealed through the top of the envelope I and is connected to an external connector cap 23 cemented to the top of said envelope.

As is well known, if two electrodes in an ionizable gas are brought closer together, the voltage at which the gas breaks down and at which a discharge is initiated between said electrodes falls until a predetermined distance is reached at which said breakdown voltage is a minimum.

This distance is known as the minimum breakeVV down distance. If the separation between the electrodes is decreased still further, the voltage` a substantial width. it will be seen that if any substantial part of the active surface of the cathode 2 is at the minimum breakdown distance from the lower cathanode grid 4, breakdown at the minimum voltage value will occur between said electrodes. The anode 3 is spaced from the upper cathanode electrode 4 by a distance substantially less'than the minimum breakdown distance. The spacing between the electrode 5 and each of the adjacent grids 4 is .preferably substantially the same as that of the spacing of the anode 3 from the upper grid 4. In a practical case with the above-mentioned krypton-xenon mixture at 10 mm., the cathode was spaced about .040" from the lower grid 4, while the spacings between the electrodes 3, 4 and 5 were each about .015". Y

The tube vdescribed above may be utilized in a circuit such as that illustrated in Fig. 3, wherein the same reference numerals are applied where the elements are identical with those of Figs. 1 and 2. In. this circuit the cathode 2 is connected by its conductor 9 to ground. The anode 3 is connected through a suitable load 25, a conductor 26, and a source of potential 21, such as a battery, to ground, The battery 21 is polarized so as to make the anode 3 positive ,with respect to its cathode. The battery 21 is also connected through the conductor 26, a cathanode resistance 29, and a cathanode condenser 30 to the ground conductor 9. The cathanode 4 is connected by means of its conductor I5 to a point intermediate the resistance 29 and the condenser 30. A signal input voltage may be supplied to the primary winding 3| of a signal transformer 32 having a secondary winding 33. One end of said secondary winding is connected through a condenser 34 to the conductor I8 leading to the control grid 5. The other end of said secondary winding 33 is connected by a conductor 35 to the conductor I5 connected to theY cathanode 4. A leakage grid represents the manner in which the voltage on condenser 30 varies during such charging and discharging. This voltage rises along said curve a until a point :I: is reached when the Voltage between the cathode 2 and the cathanode 4 is at its breakdown value. Thereupon an ionizing discharge is initiated between said electrodes and .the condenser 30 is discharged by the resulting flow of current between said electrodes.

Thus, when the discharge is initiated at the point x, a current impulse b will flow between the cathode 2 and the cathanode 4. Due to the flow of the current impulse b, the voltage on the condenser 30 falls as indicated by the curve a beyond the curve When this voltage falls to a value less than that4 which it is suflicient to maintain the discharge, the current b decreases to substantially Zero and the discharge between the cathode 2 and the cathanode 4 is extinguished. Thereupon condenser 30 is recharged and the cycle is repeated. The cathanode resistance 29 is suiiiciently large so that the charging current to the condenser 30 remains at a substantially uniform value. This charging current Ika isrepresented by the curve c in Fig. 4. The current Ika is the standby drain which the battery 21 is called upon to deliver. In a practical case this standby current has been about 25 microamperes. This value is so small that the drain on the battery is negligible and its shelf life is in nowise decreased thereby.

With the present device only avery small bias on the grid 5 is required to prevent a discharge from being propagated to the anode 3. A typical characteristic curve `of the grid 5 is shown in Fig. 5 in which the Value of D. C. grid bias voltage required to prevent a discharge to the anode 3 is shown with various values of voltage of the battery 21 and various values of capacityV of the cathanode condenser 30. Values ofv grid voltage more positive than those indicated will cause a discharge to be propagated to the anode 3.

In the circuit Fig. 3, the grid 5, due to the presence of the highleakage grid resistance 33, will assume a negative bias sufcient to hold oil the anode discharge under conditions, of zero signal voltage. The electron ilow to the grid 5 to maintain said negative bias is only about .2 microamperes in a practical case.

If a signal voltage is applied to primary winding 3|, this signal voltage will be transferred through the transformer 32 and the condenser 34 and the grid 5. When the signal voltage swings in a positive direction so as to move the potential of thegrid 5 more positive than the critical grid voltage, as shown for example in Fig, 5, electrons of suiiiciently high speed projected into the spacev between the cathanode grids 4, 4 will be caused to pass in sufcient numbers to the anode 3 to initiate a self-sustaining discharge between the anode 3 and its cathode 2. As will be explained below, such projection of electrons occurs primarily at the begin'- ning of each of the cathanode current impulses b as shown in Fig. 4. When the ow of Vcurrent is initiated to the anode 3. the self-sustaining discharge which takes 'place is propagated throughout the entire ldischarge pathv between the cathode 2 and the anode 3. This causes the voltage drop between the cathanode 4 and the cathode 2 to fall to substantially the normal glow discharge value and vthereafter the voltage drop persists at this value. Under these conditions, the relaxation oscillations will be suppressed and thev device continues to 'operate with' a substany l i' -6 s v it'iallyteadyrdischslrge,dorzexamplamrdheiorder iixchxmibym-mtchlstheitube could be imade lcifzilvermilliamperesitie'tweenthe cathodeiziand ito periodically @discharge a condenser, :or the rthe .anode 3.- ;Infiorder iro. deastore :thefcircuit to mnndeivoltagetnouldiheaaipulsatingor alternating `its :standby fconditionut :would the fnecessary dan momezandiinithismavthaanodefdischarge would iinterrupt the .s'iinw of current iin this .circuit rat is bctlutomatically dnterruptediina periodicfirian- `sleastmiomentarilyeasiby openingv afswitchlal at ner. fifiertcinmi'inciples :of lthis iinvention might :tlrexcircuitzleadingfrom zthelbatterya's'lf. .Atypcal flikewiseiheautilizedinimsystem:in .which the glow operating characteristic ,umzugI 0f :the vgrid "5 its discharge lisrxeplaced by av ithelmionic shown in 'Fig. .5 dn'iwhich ithe .critical iM. S. iff inlmdef l'inns ether equivalents iWll value :ofsignalvoltage necessary vto refthetube um Suggest themselves 'fte ithOSe Skilled in the srt. Aisfsiiovrn with @various Naiues'dor l:the-tapaiiity:of i'It ssscccrdinelvidesiredzthatithefappended clalms the cathanode .condensern .and for warious be isiuen La l@broad iinterpretation :commensurate .vaines Gf thegrid registanceyg; with the scope of the invention withintherart. firneteireotivcnessisnd:reiiabiutyrftheautomne iis fciimcd :is: f

che :system :fas described l.stove .are nue, ritenere ,b5 ilnuf'eiectricalfsystemfcomprrsing nnelectrical :ataleastiinpartxtoithe stabiiizmglofithetubefcondischarge .tube .eenteming en Ienlznbie `ges 'at in .fditionsbystheffrelaxation.oscillatimn filhebreak- #substantiel Pressure. Se athode, kim Aallude fOi down sof ith'e 'discharge vspace ibetweenfthe lcathode maintaining :aadischarge atorsai'd cathode, an aux- 2 )and fthe cathanode .1 4tends itooccur .always wit iiiaryffelectrode im' maintaining `an auxiliary inzthefsameivoltagaiwhichwoltageiis dependent upon @o `telilillttellt@fiiseiimfgee'izo :said icathode, :and va conthe gas, its :pressure thsfcnnditionsiof thetsurfatc incl electrcde interposed iin the r'discharge :path of the .cathode .2 and the spacing between the fhetweenssaidfcathndefandyanode and adapted to cathode 2 and the cathanode 4. T hus, the actual fcuntrdl 'the :initiation fof said discharge 'between voltage of the battery 'lemaywary over wid-e said mnode'iand teathnde, fia fcircuit f101 applying' a ,limits andstill .the voltage.cngthcicathanode-.will alcitagebetween-seid cathode and-anode tending rise alongthe curve a (Fig. 4),and.-the.cathanodo no icausemrdischargeibetween them, a circuit 'inspace will break down at substantially the same iterconneeting said nfc-iilthode and auxiliary elecpeak valuem. 'Itfalso appearsthatthe speed at Ytrodefor causing:said-lintermittentdischarge,'and whichv the electrons from :the cathanode espace means:i'ortapplyingiafsignal yvoltage 'tosaid-con- .are projected into the space between ithef'cath- 'ftrl :electrode ito vcause #said discharge vbetween ,anode grids v4, 4 is aprimaryfcontrolling condi- :saidlanode dtirdicaithodefto bie-initiated vduring-ari .tion in;so. f.ar as thecontrol Iexerted by the: control mpulseiof;saiiii1itermittent discharge.

,grid Y5 and =.the initiationofconduction to *the 2,. An electrical system comprising an'elec'trical ianode'- areconcerned. :Duringithe non-.conduct- :discharge'itubemontaining van ionizable-gas at a ing portion of the relam-ation foscination article, `sa; fsubstantiaiipressure,avenir-dischargecathode, en

substantially no electrons are projected into the anode for maintaining a discharge to said cathspace between the cathanode grids 4, 4 and any ode, an auxiliary electrode for maintaining an electrons which do enter this space are of relaauxiliary intermittent discharge to said cathode, tively low speed. When, however, the gap beand a control electrode interposed in the distween the cathode 2 and the cathanode 4 breaks 40 charge path between said cathode and anode and down, the discharge is rapidly propagated between adapted to control the initiation of said discharge said electrodes, and substantially at that instant between seid anode and Cathode, a Circuit fOr electrons are projected through the lower cathapplying a voltage between said cathode and anode grid 4 at substantially the maximum voltanode tending to cause a discharge between them, age attained by the cathanode 4 with respect to 45 a circuit interconnecting said cathode and auxthe anode 3, Thereafter the Speed of the proiliary electrode for causing said intermittent disjected electrons falls off' substantially as indi- Charge, and means f01 applying a signal VOltage cated bythe falling portion of the curve a beyond to said control electrode to cause said discharge the point x in Fig, 4, As already indicated the between said anode and cathode to be initiated value of the cathanode voltage at the point a: is during an impulse of said intermittent dischargexed by the tube constants, and thus 11; w11] be 3. An electrical system comprising an electrical seen that the critical control voltage is xed discharge tube Containing an ionizable gas at a largely by said tube constants and varies over a substantial Pressure, a cathode, an anode fOr' relatively small range with additional circuit maintaining a discharge to said cathode, an auxvariations. The most important variation in ciriiialy electrode for maintaining an auxiliary incuit conditions which is met with in practice is termittent discharge t0 said CathOde, and a conthe variation of the battery voltage due, for extrol electrode interposed in the discharge path ample, to the aging of the battery. The extent between said cathode and anode and adapted to to which the critical grid voltage is independent control the initiation of said discharge between of such Vbattery voltages is typically illustrated@ said anode and cathode, a'circuit for applying in Fig. 5. In this figure it will be seen that with a voltage between said cathode and anode tendvariousy capacities for the cathanode condenser ing to cause a discharge between them, an oscil- 30, the battery voltage may vary from 140 to 180V .latry circuitV interconnecting' said cathode and volts and yet the critical grid voltage remainsauxiliary electrode for causing said intermittent below about one volt. 65 discharge, and means for applying a signal volt- From the foregoing it will be seen that a tube age to said control electrode to cause said disand system, constructed and operated in accordcharge between said anode -`and cathode to be ance with my invention, satisfy the objects of initiated during an impulse of said intermittent this invention to a remarkable degree. discharge, f

of course it is to be understood that this inven- '4- An electrical system comprising an electrical tion isp-not limited to the particular details as discharge tube containing an ionizeble gas at a described above as many equivalents will suggest Substantial Pressure, a Cathode, 9Ji1 anode fOl themselves to those skilled in the art. For exammaintaining a discharge t0 said, Cathode, an auX-.

ple, instead of using a source of direct current iiiery electrode fOr maintaining an auxiliary into energize the system and interrupting the anode, termittent discharge to said'ca'thode, and a con- -trol electrode interposed in the discharge path `between said cathode and anode and adapted to lcontrol the initiation of said discharge between said anode and cathode, a .circuitnjfor applying a voltage between said cathode 'and anode tendmaintaining a discharge to said cathode, an aux:- iliary electrode for maintaining an auxiliary intermittent discharge to said'cathode,l and a control electrode interposed in the discharge path between said cathode and anode and adapted to control the initiation of said discharge between said anode and cathode, a circuit for applying a voltage between saidcathode and anode tending to cause a discharge betweenthem, la ,2.5

condenser connected between said cathode vand auxiliary electrode, a high resistance connected between said control electrode and lsaid auxiliary1 electrode, and means for applyingl a signal Voltage to said control electrodev to cause said dis,- -charge between said anode and cathode to be initiated during an impulse of said intermittent discharge discharge tube containing an ionizable lgas as 35 2,084,157

a'substantial pressure, a cathode, anl anode for 'maintaining a discharge to said cathode, an auxiliary electrode for maintaining an auxiliary intermittent discharge to said cathode, anda control electrode interposed in the discharge path between said cathode and anode .and adapted to control the initiation of said discharge between said anode and cathode, a circuit for applying a voltage between said' cathode and anode tending to cause a discharge between them, a condenser connected between said cathode and aux- -iliary electrode, a source of potential connected in series with a high impedance across said condenser for producing relaxation oscillations causing said intermittent discharge, a high resistance connected between said control electrode and said auxiliary electrode, and means for applying a signa1 voltage through a condenser to said control electrode to cause saidl discharge between said anode and cathode to be initiated during an impulse of said intermittent discharge.

l PAUL W. STUTSMAN.

viile 'of this patent:

UNITED STATES PATENTS Number Name Date 1,962,158 Smith June 12, 1934 1,962,159 LeVan June 12, 1934 1,989,132 Edwards Q Jan. 29, 1934 2,171,215 Kauffeldt Aug. 29, 1939 2,054,882 Schlesinger Sept. 22, 1936 McLennan June 15, 1937

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