US2496500A

US2496500A - Electron discharge device

Info

Publication number: US2496500A
Application number: US605755A
Authority: US
Inventors: Percy L Spencer
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1945-07-18
Filing date: 1945-07-18
Publication date: 1950-02-07
Anticipated expiration: 1967-02-07

Description

P. L. SPENCER ELECTRON DISCHARGE DEVICE Filed July 18, 1945 OUTPUT 2 Sheets-Sheet l AWN/rm.

FHFOV l. S y/05 P. L. SPENCER ELECTRON DISCHARGE DEVICE Feb, 7 195@ 2 Sheets-Sheet 2 Filed July l8, 1945 Patented Feb. 7, 1950 ELECTRON DISCHARGE DEVICE Percy L. Spencer, West Newton, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application July 18, 1945, Serial No. 605,755

3 Claims (01. 250-275) My present invention relates to electron-discharge devices, and more particularly to electrondischarge devices of the so-called magnetron type, which are adapted to generate electrical oscillations having wave lengths of the order of a few centimeters, or less.

It is difficult to obtain appreciable power from magnetrons operating at the very short wave lengths above referred to because of the sizeto which said wave lengths necessarily limit the anode structures thereof. Furthermore, such magnetrons can be tuned only over relatively narrow bandwidths.

It is, therefore, one of the objects of my present invention to so construct a magnetron that, notwithstanding the very short wave length at which it is intended to operate, appreciable power may be obtained therefrom.

It is another object of my present invention to so construct said magnetron that the frequency of the oscillations generated thereby may be varied over an appreciable range.

These, and other objects of my present invention, which will become more apparent as the detailed description thereof progresses, are attained, briefly, in the following manner:

I provide the magnetron of my present invention with an anode structure which includes at least two groups of cavity resonators, each dimensioned to oscillate at a different frequency, and all of said frequencies, preferably, bearing a harmonic relationship to each other. Said groups of cavity resonators are axially displaced with respect to each other, preferably, along a centrallylocated cathode structure, and said groups of cavity resonators are, in addition, preferably, disposed at different distances from said cathode structure.

A magnetic field is established transversely of the electron-path between said cathode and anode structures, said magnetic field being variable so that the orbital frequency of the electrons emitted by said cathode structure may be adjusted so as to excite the above-mentioned differently-dimensioned cavity resonators simultaneously at any I that by combining these oscillations, resultant oscillations are obtained which contain appreciable power at the average of the constituent frequencies, namely, at a frequency correspond-,- ing to a wave length of 7.5 cm. If the magnetic field is altered so that the orbital frequency of the electrons emitted by the cathode structure is such that the group of l0-cm. cavity resonators oscillates more strongly than .the other group, the frequency of the combined oscillations increases, and vice versa. I have further found that by the means described, I can obtain appreciable power at any frequency between the frequencies corresponding to the dimensions of the diiferent groups of said cavity resonators.

In the accompanying specifications I shall describe, and in the annexed drawings show, an illustrative embodiment of the electron-discharge device of my present invention. It is, however, to be clearly understood that I do not wish to be limited to the details herein shown and described for purposes of illustration only, inasmuch as changes therein may be made without the exercise of invention and within the true spirit and scope of the claims hereto appended.

In said drawings,

Fig. 1 is a vertical sectional view taken substantially through the center of an electrondischarge device made in accordance with the principles of my present invention; and

Fig. 2 is a fragmentary, perspective view taken substantially at the same line as Fig. 1.

Referring now more in detail to the aforesaid illustrative embodiment of my present invention, and with particular reference to the drawings illustrating the same, the numeral 5 generally designates an electron-discharge device of the magnetron type. Said device includes a centrally-disposed cathode structure 6, an anode structure 1 surrounding said cathode structure, and means 8 for establishing a magnetic field transversely of the electron-path between said cathode and anode structures.

The anode structure 1, preferably, comprises a cylindrical body -9, made of highly conductive material, such as copper, and provided with at least two'axially displaced groups it and II of highly conductive, vertically aligned vanes 12 and I3, one of said groups, for example, the group I0, being radially disposed and extending inwardly from a boss l4 formed on the interior surface of the body 9, and the other group, likewise, being radially disposed, but extending inwardly from the interior surface, itself, of said body 9.

Each adjacent pair of the vanes l2 and I3 of each of the groups theref constitutes, together with that portion of the cylindrical body 9 lying therebetween, a cavity resonator whose natural resonant frequency is dependent upon the inductance and capacitance built therein as a function, primarily, of the physical dimensions of the elements making up the same.

The vanes of one of the groups, here shown as the vanes I 2 of the group [0, are smaller than'the vanes of the other group, so that the cavity resonators formed by the first-mentioned group frequency corresponding to a wave length of 7.5

are resonant at a higher frequency .than thoseformed by the remaining group. For example,

the dimensions of the smaller cavity resonators may be such that they have a natural resonant frequency corresponding to a wave length of 5 cm., while the dimensions of the remaining cavity resonators may be such that they resonate at a frequency corresponding to a wave length of cm. It is preferred that the smaller vanes extend to within a shorter distance of the cathode structure 6 than do th'elarger vanes. Under these conditions, it is possible, as will be hereinafter more fully described, to obtainappreciable power at any frequency corresponding to any wave length between 5 and 10 cm.

It is preferred, althoughnot necessary, that the alternate vanes of both groups l0 and II thereof be electrically interconnected, for example, by conducting straps I5 to 22, inclusive, in order to suppress spurious oscillations at undesired frequencies.

The cathode structure 6, preferably, comprises a cathode sleeve 23 made, for example, of nickel, and provided with a highly electron-emissive coating 24, of the well-known alkaline-earth metal oxide type. The sleeve 23 is provided with heating filament, not shown, having

terminals

25 and 26 connected to lead-in conductors 21 and 28 which enter the device through lass seals, not shown, at the ends of

pipes

29 and 30 threadeclly engaged and hermetically sealed-into the cylindrical body 9, said lead-in conductors being connected to a suitable source of filament voltage.

The cylindrical body 9 is closed at its ends by plates 3| and 32, the junctions between said plates and said body being hermetically sealed. The plates are provided with central apertures 3.1 and 34 to receive stepped portions of

pole pieces

35 and 36, the latter being provided with

windings

31 and 38 connected in series with each other and with an adjustable-source v39 of unidirectional voltage, for example, a battery 40 having a potentiometer 4| across the same.

When a device such as has been described is provided with a suitable voltage between its cathode and anode structures, and the magnitude of the magnetic field, which is transverse of the electron-path between said cathode and anode structures, is appropriately adjusted, the cavity resonators formed by the groups In and l I of-the vanes l2 and i3 will have electrical-oscillations generated therein. At a certain, what I shall call, intermediate value of magnetic field, both groups of cavity resonators will be equally excited. At a higher value of magnetic field, the oscillations will be stronger in the cavity resonators nearer to the cathode structure, in this case, those formed by the group "of vanes l2. At a lower value of magnetic field, the other group of cavity resonators will have the stronger oscillations generated therein.

Now, power may be extracted from the device by means of a loop 42 which may enter the device through a pipe 43, the loop being so disposed cm., and thepower at this frequency can be picked out by applying the output of the device to a properly tuned circuit 44.

-' n power at a higher frequency is desired, the

magnitude of the magnetic field may be increased by adjusting the source of voltage 39 to favor oscillation in the shorter wave length cavity resonators, and correspondingly retuning the circuit 44.

Finally, if poweriat a lower frequency is desired, the magnitude of the magnetic field may be reduced so that oscillation will be favored in the longer wave length cavity resonators, and again, correspondingly tuning the circuit 44.

This completes the description of the aforesaid illustrative embodiment of my present invention.

It will be noted from all of the foregoing that Ihave provided a magnetron which is so constructed that appreciable power can be obtained therefrom notwithstanding the very short wave length at which it is intended to operate. It will further be noted that merely by altering the magnitude of the magnetic field of said magnetron I am enabled to obtain said power at any frequency within a band of considerable width.

Other objects and advantages of my present invention will readily occur to those skilled in the art to which the same relates.

What is claimed is:

1. An electron-discharge device comprising: a cathode; an anode structure, spaced from said cathode, and incorporating a plurality of groups of differently dimensioned cavity resonators; the entrances to the cavity resonators of each of said groups of cavity resonators being disposed at different distances from said cathode; adjustable means, adjacent said cavity resonators, for establishing a magnetic field of variable magnitude transversely of the electron path between said cathode and anode structure; and output means coupled in common with all of said groups of cavity resonators.

2. An electron-discharge device comprising: a a cathode; an anode structure, spaced from said cathode, and incorporating a plurality of groups of differently dimensioned cavity resonators; said groups of cavity resonators being axially displaced along the length of said cathode and the entrances to the cavity resonators of each of said groups thereof being disposed at different distances from said cathode; adjustable means, adjacent said cavity resonators, for establishing a magnetic field of variable magnitude transversely of the electron path between said cathode and anode structure; and output means coupled in common with all of said groups of cavity resonators.

3. An electron-discharge device comprising: a cathode; an anode structure, spaced from said cathode, and incorporating a plurality of groups of differently dimensioned cavity resonators; each group of said cavity resonators including a plurality of inwardly-directed, radially-disposed anode vanes each adjacent pair of which, together with that portion of said anode structure lying therebetween, constitute one of said cavity resonators; said groups of cavity resonators being axially displaced along the length of said cathode, and the inner ends of the anode vanes of each group terminating at a different distance from said cathode; adjustable means, adjacent said cavity resonators, for establishing a magnetic field of variable magnitude transversely of the electron path between said cathode and anode structure; and output means coupled in common with all of said groups of cavity resonators.

PERCY L. SPENCER.

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

UNITED STATES PATENTS Number Name Date 2,114,114 Roberts Apr. 12, 1938 2,250,698 Berline July 29, 1941 2,295,315 Wolfi Sept. 8, 1942 2,402,983 Brown July 2, 1946 2,404,212 Bondley July 16, 1946 2,414,085 Hartman Jan. 14, 1947 2,419,172 Smith Apr. 15, 1947 15 2,423,161 Spencer July 1, 1947