US2317140A

US2317140A - Electron discharge apparatus

Info

Publication number: US2317140A
Application number: US423164A
Authority: US
Inventors: Gibson William Thomas
Original assignee: International Standard Electric Corp
Current assignee: International Standard Electric Corp
Priority date: 1940-05-28
Filing date: 1941-12-16
Publication date: 1943-04-20
Anticipated expiration: 1960-04-20
Also published as: BE482822A; CH259592A; GB541529A; FR58577E

Description

w. T. GIBSON 2,317,140

ELECTRON DISCHARGE APPARATUS Filed Dec. '16, 1941 gm;lymmmmmlll l fl INVEN TOR w T 0 135cm HTFOPN E Y Patented Apr. 20, 1943 ELECTRON DISCHARGE. APPARATUS William Thomas Gibson, London, England, assigner to International Standard Electric Corporation, New York, N Y.

4 Claims. (CL 250-27) This invention relates to electron discharge apparatus foroperation at high frequencies and particularly to apparatus utilising the principles of velocity modulation of electron beams and of the excitation of high frequency resonators by the passage of electrons in pulses or bunches.

In one aspect the invention is concerned with electron discharge apparatus wherein an electron beam modulated by the field of one resonator is utilised to excite a second resonator and consists in feeding back high frequency energy from the second resonator to the first resonator by means of an auxiliary electron beam.

In another aspect the invention resides in electron discharge apparatus comprising a pair of hollow resonators having aligned apertures, means for directing an electron beam through said apertures, so that the beam is velocity modulated in traversing the first resonator, and is bunched on arrival at the second resonator and adapted to yield energy thereto and means for setting up an auxiliary electron beam and directing it through the second resonator and then through the first resonator to feed back energy to the first resonator.

Preferably means are provided for varying the density and mean velocity of the auxiliary beam to permit adjustment of the amplitude and phase of the feedback.

The invention will now be described in more detail with reference to the accompanying drawing, Fig. 1 of which is a diagrammatic representation of a known device for efiecting velocity modulation of an electron beam; whilst Fig. 2 shows an electron discharge apparatus according to one embodiment of the present invention.

One known means of generating large amounts of power at very high frequencies is by use of the device known as a Klystron. By high fre quencies is meant frequencies of the order of 300 megacycles and above.

In this device a beam of electrons is fired successively through two hollow resonators tuned to the same frequency. A diagrammatic drawing of such a device is shown in Fig. 1 of the accompanying drawing. In this figure, l represents a source of electrons, which may be an indirectly heated oxide coated cathode. 2 is a focussing cylinder, which co-operating with the cylinder 3 adjusted to appropriate voltages produces a beam of electrons which passes through the central tube and finally arrives at a collecting anode 8. Electrodes 3 and 8 are maintained at appropriate high potentials, and 2 may be at a negative, zero, or slightly positive potential with respect to the cathode. t and 5 represent hollow resonators formed by revolution about the axis of the figure, and should be made of a very good electrical conductor with very clean inner surface.

At 6 and 1 are two sets of grids separated by small gaps. These grids should present as small an area for the collection of electrons as possible. If an oscillation is assumed to exist in resonator a then electrons in the beam will be alternately accelerated and decelerated in passing through the grid gap at 6. During the flight through the tube to the next set of grids l, the accelerated electrons will advance with respect to the decelerated electrons and by appropriate 1 adjustment of the velocity of the electron stream,

conditions can be found such that the electron stream arrives at grid gap I substantially in dense bunches separated by intervals when relatively few electrons arrive. If the bunches arrive at such moments that the field across the grids due to the local oscillation tends to decelerate them, then the electrons will do work on the system, with resulting amplification of the oscillation in resonator 8.

If a coupling represented by 9 is used to feed back oscillations to resonator t then by appropriate adjustment conditions can be found where the oscillations will rapidly build up to very high amplitude. It is possible to extract power for useful purposes by a second coupling coil Ill in the resonator 5 which feeds power via a concentric line formed by l and tube 2 to an antenna or other absorber.

In operating a device of this type, the adjustment of the coupling 9 is an important matter, and it is necessary to adjust it to the correct magnitude for best results. Furthermore, there is a delay in the flight of electrons from 6 to I which may amount to several cycles. It is necessary, therefore, to ensure that the phase lag in the coupling 9 is adjusted so that the phase lag between the two resonators suits the distance 6 to I and the time of flight of the electrons.

With mechanical systems as shown it is difficult to secure these variations without complicated mechanical motions which must usually be operated under high vacuum.

An alternative system to facilitate adjustment and control of feedback coupling is now proposed and will be particularly described with reference to Fig. 2 of the drawing.

In Fig. 2, dashed numerals apply to parts whose disposition and function is unchanged from Fig. 1. In addition is shown another cathode In! and shield I02 sending a beam of electrons through a separate and relatively small diameter tube ofi'set in the resonators. The beam passes through grid gaps at I03 and I and through drift tube I04. The current required in this beam is very small compared with that in the main beam and the left-hand grid at I05 may actually be a disc at which the electrons are collected.

The performance of this beam is identical with that of the main beam, and its object is to transfer very small amounts of power back from resonator 5' to resonator 4'.

The amplitude of the feedback is controlled by variation of the density of the electron beam, for example by variation of potential of shield I02 or by variation of the temperature and total emission of cathode IN.

The phase delay between resonator 5' and 4 can be compensated for by adjustment of the velocity of the electrons in the tube I04, which is done by variation of the potential between the whole resonator system and the cathode It".

In general, the voltage developed in resonator 5' will be very large and only a small voltage is required to modulate the feedback beam. This is accomplished by the offsetting of the electron beam from the central position.

It will be appreciated that the resonators may take various different shapes and that various dispositions of the several parts particularly the auxiliary beam system are possible. For example, the use of flattened resonators of an axial length comparable with the lengths of the gaps I03, I05 may simplify the construction. The auxiliary beam may be inclined to the axis so that the couplings between the resonators and the auxiliary beam are not equal. For example,

if the gap I05 is brought closer to the axis of the resonators, the bunched auxiliary beam will tend to set up a larger voltage in resonator 4'.

What is claimed is:

1. Electron discharge apparatus comprising first and second hollow resonators having two sets of aligned apertures, means for producing a main electron beam, means for directing said main electron beam through one set of aligned apertures in the direction from said first resonator to said second resonator so that the said beam is velocity modulated in traversing said first resonator and is bunched on arrival at said second resonator and yields energy thereto, and means for producing an auxiliary electron beam and for directing it through the other set of aligned apertures in the direction from said secand resonator to said first resonator whereby said auxiliary electron beam is velocity modulated and feeds back energy from said second resonator to said first resonator.

2. Electron discharge apparatus according to claim 6 wherein said aligned apertures through which said main beam is directed are disposed along the center line of the said resonators and the aligned apertures through which said auxiliary beam is directed are disposed along a line off-set but parallel to said center line.

3. Electron discharge apparatus comprising first and second hollow resonators having two sets of aligned apertures, means for producing a main electron beam, means for directing said main electron beam through one set of aligned apertures in the direction from said first resonator to said second resonator so that the said beam is velocity modulated in traversing said first resonator and is bunched on arrival at said second resonator and yields energy thereto, a cathode for producing an auxiliary electron beam for directing it through the other set of aligned apertures in the direction from said second resonator to said first resonator whereby said auxiliary electron beam is velocity modulated and feeds back energy from said second resonator to said first resonator, means for applying a positive potential to said resonators relative to said cathode and means for varying the potential difference between said resonators and said cathode for varying the phase of the energy fed back.

4. Electron discharge apparatus comprising first and second hollow resonators having two sets of aligned apertures, means for producing a main electron beam, means for directing said main electron beam through one set of aligned apertures in the direction from said first resonator to said second resonator so that the said beam is velocity modulated in traversing said first resonator and is bunched on arrival at said second resonator and yields energy thereto, a cathode for producing an auxiliary electron beam, a focusing electrode for directing said auxiliary electron beam through the other set of aligned apertures in the direction from said second resonator to said first resonator whereby said auxiliary electron beam is velocity modulated and feeds back energy from said second resonator to said first resonator, means for creating a potential difference between said focusing electrode and said cathode, and means for varying said potential difference for varying the amplitude of the energy fed back.

WILLIAM THOMAS GIBSON.