US2411538A - Electron discharge apparatus - Google Patents

Description

Nov. 26, 1946. F. D. GOODCHILD 5 ELECTRON DISCHARGE APPARATUS Filed June 25, 1941 Fig. 2.

J. MM'

Patented Nov. 26, 1946 &4115 38 signor to International Standard Electric co'r- 'poration, New ifiirk, N. Y.

- Application J'une 25,*1941, Serial No. 399599 In Great Britain June 21, 19510.

1 Claim. (Cl. aso-27.5)

This invention relates to electron discharge apparatus incorporating high frequency resonators of coaxial-conductor type and to insulating seals for co-axial conductors.

In co-pending U. S. application Ser. No. 361401, filed November 27, 1940, corresponding to British Patent No. 531490, June 24, 1941, various electron discharge devices are disclosed comprising lengths of co-axial conductor line constituting Very high frequency resonators and means for passing electron beams through the fields of the resonators for the Velocity modulation of the electrons. i

In such arrangements, and generally where coaxial-conductor-type resonators are employed as frequency determining circuits interacting directly with electron streams in electron discharge apparatus, it is desirable to provide means for tuning the resonator and a convenient way of doing this is to vary the electrical length of the conductors, that is, the sp-acing between nodal points. Obvious difficulties immediately arise if the resonator is wholly contained within an envelope. Diiculties also arise in reducing radiation loss to a satisfactorily small value if the co-axial conducto-rs are split into mechanically separate parts respectively inside and outside the envelope, these difficulties arising mainly because of the necessity' of a glass or other partiticn bee tween the parts. i

The invention in one aspect thereof resides in an electron discharge device comprising co-axial conductors sealed in a, vacuum tight glass envelope, electrodes within the envelope adapted to set up an electron beam traversing the field of the co-axial conductors for the direct interaction of the electrons and the field and means Operating upon the part of the co-axial conductors outside the envelope for Varying the electrical length of said conductors.

The invention also resides in a, method of making an insulating sea between co-axial conductors consisting in fusing a glass ring on to the inner surface of the outer conductor, fusing a glass bead on to the inner conductor and inserting the inner conductor into the outer conductor while the glass ring and the glass bead are molten I so that these glass parts become united.

invention for making a seal for bringing a coaxial conductor transmission line out of an evacuated envelope will now be described with reference to Figs. 1 and 2 of the accompanying drawing.

In the first figure there is shown a length of co-axial conductor transmission line comprising a Copper tube A and a centre rod B; C is a button of glass and D a stem sealed to the outside of the tube and adapted to be sealed in known manner in a bulb which in the present case surrounds the tube A. 'The Copper tube A is machined down to a wall thickness ,of 0.015" in the region of the glass button and is feathered in the well known manner at the point where the stem is sealed on the outside.

. on to the Copper wall. A bead of glass is also fused to the centre rod at G. Both these small pieces of glass are heated simultaneously and while still molten the rod is pushed into the tube so that the two pieces of glass are joined together.

The rod B may be wholly of Copper of uniform diameter or the part passing through the glass button may be a squirrel cage structure or a Copper sheath as will be clear from the disclosures in British Patent No. 538,485, August 6, 1941. It is also possible for the rod to be of tungsten and the glass bead of hard glass.

In Fig. 3 of the accornpanying drawing is shown a dscharge device utilising the principles of electron velocity modulation and incorporating a coaxial-conductor-type resonator. The device embodies theseal described with reference to Figs. 1 and 2, and shows by way of example how the co-axial concluctors may be brought out from the evacuated envelope and tuned by means external to the envelope.

Referring to Fig. 3 the co-axial conductors A and B are provided with apertures K in a common diameter and fins L in the apertures and projecting from a part M of the wall which serves to collect the electrons. A cathode N and a fccussing electrode O are required outside the tube A opposite the aligned apertures. These constructiona features and th principles of operation for the generation of high frequencies are fully described inthe above mentioned U. S. ap-

plication Ser. No. 367 ,401.

The co-aXial conductors extend through the" UNITED STATES einem' oFFcef f stem E, the sealing arrangeinents being as already described. The frequency of oscillation depends upon the length of the conductors between short-circuiting conductive b ridging members. One of these conductive bridging members is constituted by a plunger or piston H slidable within the part of the tube A and along the part of the rod B which projects through the stem E. Any convenient screw or other adjusting mechanism may be provided for the plunger. The arrangement provides continuous adjustment of the Operating frequency with a range of frequencies.

Modifications within the scope of the invention as well as different applications of the features claimed will be readily appreciated.

What is claimed is: v

Electron discharge device comprising co-axia] 4 conductors' s'ealed substantially within a vacuum tight envelope and having aligned apertures, part of said coaxial conductors being outside said envelope, electrodes within the envelope in line with said apertures and adapted to set up an electron beam traversing the apertures of the co-axal conductors for the velocity modulation of the electrons an annular insulating seal between the inner conductor and an intermediate portion of the outer conductor of reduced wall thickness a coaxial sea] between an end of the outer conductor and a glass tube forming part of the envelope, and adjustable means within the part of one of the co-axial conductors outside the enve lope for Varying the electrical length of said conductors.

FRANK DOUGLAS GOODCHILD.

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