US2513933A - Cold cathode magnetron - Google Patents

Description

July 4, 1950 A. M. GUREwn-SCH y 2,513,933

QLD CATHQDE MAGNETRON y Filed March 28, 1.946

"MME

TN/ OT 2 Anatole urewitsoh H iS Att Orr-1 ey.

Patented July 4, 1950 com oATHonE MAGNETRON t Anatole M. Gurewitsch, Schenectady, N. Y., assignor to General Electric Cmpany,ta corporation Yof New York.

Appartenant/rama 2s, 1946,seria1'No. 553,716,

the cold cathode requires no separate heatingv circuit, as does the'hot emission type, considerably simplifies tube manufacture and, operation. This feature, together with the fact that it generally requires no electron emissive coating, fa-

cilitatesfthe design of rugged and durable tubel constructions which can better withstand the physical shocks to which electron tubes may be subjected in practical usage. Moreover, as is particularly the case with magnetrons, the cathode may be subjected to undesirable overheating and destruction by bombardment by. electrical particles within the; tube. Because of their generally more durable construction coldcathodes are more able to withstand such effects thereby lengthening the life of the tube and the cathode inoperation.

rIhe invention will'be better understood from the following description when considered in connection with the accompanying drawings in which'Fig. 1 represents a magnetron incorporate ingY the improved cathode of the invention; Fig, 2 represents a detailed View ofthe cathode, and Fig. 3 represents a cross sectional View of the anode-cathode structure taken along the line l--I of Fig. 1.

Referring to Fig. 1, it will be noted that the magnetron comprises the conventional elements including )an anodel I0 and permanent magnetic pole vpieces Il and l2'which supply the magnetic eldfor operation of the magnetron in thel well known manner. Useful output power of the magnetron may be `taken from the output y'loop I3 inserted within one of the anode cavities I4 in the usual manner. The entire ensemble including the novel cathode I5 to be hereinafter described, is supported in any suitable manner within an evacuated envelope I6 which may be of metal, glass, or any of the equivalent materials common in the art. A potential difference between the anode and cathode may be imposed by any source of intermittent or continuous voltage such as the pulser circuit l1 which has its negative terminal connected to the cathode l5 and its positive terminal connected to the 5 Claims, (Cl. 256-27.5)

t anode throughV the ground connections I8 rand,

the metallic envelope I6. Cylindrical cavities I9 and are provided in the magnetic p ole pieces l l and i2, respectively, to permit the introduction of suitabley leads 2l and 22 to the cathode sections 23 and 24, respectively.v

The cathode I5 comprises two generally cylindrical sections 23 and yZllhaving closed end por-V tio- ns 25 and 26, respectively, and juxtaposed open endsZland 28. The. cathodeA sections, 23 and,l 24 are ccaxially mounted as shown andvmaintained in fixed spaced relation by means of the insu-A lator 29 which maintains electrical insulation,between the members 23 and. 24, at least as. re-

u spects the direct current and low frequency. comfponente of the .varo1'1.s. electrical Currents 4involved in the operation of the tube.

As will be seen fromthe drawing, the. juxtaposed edges. ofthe openends 2l and 28 are so constructed asY toform sharpv or pointed surt faces which willrfacilitate the inductionwof Van electrical discharge, when a voltagev difference exists between the two sectionsl y23 and ,24. Alternatively, the openends 21 andZil may be pro.

vided with a-series of sharp points or serrations,

not shown. Asis well known, sharp edges or pointed surfaces createa high potentialvgradient inthe neighborhood of Vthe edge or point which gradient facilitatesthe initiationy of a discharge. It is to be understood, therefore, that. anyconstruction in which a series of sharp points are.

juxtaposedrin` such manner that a potential difference will readily create a discharge, may-be used inthe piace ofthe construction shown.l

The cathode section 23 isconnected by lead-2| directly to the negative terminal `of -the pulser circuit il. Thesection 24, on the other hand-is connected to ground, i. e tothe anode through lead22 and a relatively high impedance suchas resistanceft. kIt will be understood, therefore, thatwhena potential diierence is applied. be; tween the lanode l0 andthe cathode Ifby the pulser circuit Il the same potential difference will initially be imposed across the gap formed by the edges 21 and 28. Immediately, however, as the current across the gap produces a potential drop in the resistance 3Q, the potential of the section 24 will drop below that of the anode and tend to approach the potential of the section 23. ln the process, a sufcient number of electrons will be released by the gap to permit the operation of the anode and cathode as a conventional magnetron. If the supply should diminish, the current through resistance 3i) will likewise diminish thereby raising the potential of member 24 to increase the energization of the gap.

The foregoing construction will be found to be particularly useful in connection with electron tubes of the magnetron type for the reason that in operation there is an inherent tendency of such type of tube to return a, considerable number of electrons to the cathode with resultant overheating and destructive eii'ect on the cathode. Furthermore, it is particularly adapted to magnetrons operated in pulsing fash-` ion, such as pulsing oscillators in radio location work where the tube is required to oscillate only during periodic short intervals. This is for the reason that the gap will suii'ice to supply enough electrons for the short period required, Whereas it might not in all cases be suicient to supply.

al1 such changes and modiications as fall with-z in the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electron discharge device comprising a cathode of the cold emission type comprising juxtaposed members electrically insulated from each other and forming a gap of high electric field intensity, an electrode in electron receiving relation to said cathode, means connected to said electrode and to one of said cathode members for applying an operating voltage between said electrode and one of said cathode members,

a relatively high impedance connecting said electrode to another of said cathode members whereby said operating voltage is applied to said impedance and said gap in series to induce an electrical discharge at said gap.

2. An electron discharge device comprising an anode and a cathode of the cold emission type comprising spaced cylindrical members e1ectri` cally insulated from each other and having juxtaposed sharp edges forming a gap of high electric field intensity, means connected to said anoderand one of said spaced cylindrical members for applying an operating volta-ge between said anode and one of said cathode members, a relatively high resistance connecting said anode to the other of said cathode members whereby said operating voltage is applied to said resistance and said gap in series to induce an electrical discharge at said gap.

3. An electron discharge device of the magnetron type comprising a cathode of the cold emission type comprising juxtaposed members electrically insulated from each other and forming a gap of high electric field intensity, an anode, a relatively highimpedance connecting said anode to one of said cathode members, and means connected to said anode and said other of said cathode members for imposing a positive potential upon said anode with respect to said cathode.

4. An electron discharge device of the magnetron type comprising a cathode of the cold emission type comprising juxtaposed members electrically insulated from each other and forming a gap of high electric eld intensity, an anode positioned kin electron receiving relation to said cathode, means connected to said anode and to one of said cathode rmembers for applying an operating'voltage between said anode and said one of said cathode members, a relatively high resistance connecting said anode to the other of saidr cathode members whereby said operating voltage is applied in said resistance and said gap in series to induce an electrical discharge at said gap.

5. An electron discharge device of the magnetron type comprising a cathode of the cold emission type comprising spaced coaxial cylindrical members electrically insulated from each other and having juxtaposed sharp edges forming a gap of high electric field intensity, an anode spaced from said cathode, means connected to said anode and to one 0f said cathode members for imposing a positive potential upon said anode with respect to said one of said cathode members, a relatively high resistance connecting said anode to the other of said cathode members whereby said positive potential is applied across said gap at the initial moment of operation to initiate an electrical discharge in said cathode.

ANATOLE M. GUREWITSCH.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,230,004 Meikle June 12, 1917 1,279,850 Dubilier Sept. 24, 1918 1,309,704 Stoekle July 15, 1919 1,559,714 Lilienfeld Nov. 3, 1925 1,565,659 Lilienfeld Dec. 15, 1925 1,577,846 Nicolson Mar. 23, 1926 1,661,579v Rollinson Mar. 6, 1928 1,705,377 Robinson Mar. 12, 1929 1,863,702 Smith June 21, 1932 1,930,088 Foulke Oct. 10, 1933 1,965,589 Foulke July 10, 1934 1,984,877 Jobst et al. Dec. 18, 1934 1,986,894 Laurent Jan. 8, 1935 2,163,157 Samuel June 20, 1939 2,293,468 vKnipp Aug. 18, 1942 2,406,276 White Aug. 20, 1946 2,409,716 Slack et al.,y Oct. 22, 1946 2,456,896 Slack et al. Dec. 21, 1948

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