US2639407A

US2639407A - Closed end magnetron

Info

Publication number: US2639407A
Application number: US660604A
Authority: US
Inventors: Jr Willis E Lamb
Original assignee: US SEC WAR
Current assignee: United States, WAR, Secretary of; US SEC WAR
Priority date: 1946-04-09
Filing date: 1946-04-09
Publication date: 1953-05-19
Anticipated expiration: 1970-05-19

Description

IN V EN TOR.

ATTORNEY May 19, 1953 w. E. LAMB, JR

CLOSED END MAGNETRON Filed April 9. 1946 m n n m I WILLIS E.LAMB, JR. i .Aza 9,, ,Lu

FIGZ

Patented May 19, 1953 CLOSED. END MAGNETRONV Willis E. Lamb, Jr., New York, N. IL, assignor to United States of America as represented by the Secretary of War Application April 9, 1946, SerialNo. 660,604 7 Claims. (01. 315-40) I This invention pertains to a magnetron in which the cover plates are soldered directly to the ends of the anode, to thereby eliminate-the usual end zone.

One of the objects of this inventionis to provide a magnetron. having very goodmodeseparation.

Another object is to provide a magnetron having a low pulling figure.

Still another object is to provide amagnetron in which a high ratio of resonator lengths may be employed.

- Still another object is to provide an arrangement whereby a magnetron may be converted to operate at shorter wavelengthsthan that for which originally designed.

These and other objects will become apparent in the specification and in the. accompanying drawing in which:

Figure 1 shows the section through the closed end magnetron anode; and I Figure 2 shows a sectional view along line 2-2 of Fig. 1.

As shownin Figures 1 and 2 the magnetron anode is of the Rising Sun type and comprises the anode body In. providedwith .the usual. small and large cavities H and I2 respectively and with vanes l3 extending radially between the cavities toward the cathode. A pair of end plates l4 and I5 are soldered or otherwise attached directly to the ends of the anode body and are provided. with openings l6 and II, respectively, to permit passage-of the cathode, not shown.

In the construction shown the usual end space has been completely eliminated. The same anode with open ends has no variation of theiradio frequency field along its length and has a wave length of M for the 1r mode. Thisanode with. its ends closed in accordance with this invention has a sinusoidal variation of the radio frequency field along the height of the anode with. the result that the wave length x is smaller. The new value of A is given by the formula:

1 1 p w za where h is the height of the anode. Thus, the smaller the h the smaller is k for a given in. As

an example it may be assumed that it is desirable to have avalue vfor M of 2.77 cm. would be necessary. As a compromise, in order to compensate for the cf:- fect described above A0=1.60 cm. was used in constructing the sample described below requiring a corresponding h=0.394' v A possible. disadvantage of this construction may be considered to. lie in the fact that the percentage of mode separation is decreased by the.

lowering of wavelengths produced by the presence of the end plates namely,

were x A0 t From the sample dimensions given above obtained by simply using a high ratio R of. resonator lengths. Inthe example cited, the, 39% loss in modeseparation can be compensated for by increasingR. to a value of 2.0, from the expected value of 1.7, which, in the light of previous experiencewoulcl appear to be best in 18 .vane open ended anodes.

A typical example for an 18 cavity Rising Sun magnetron has the followingfldimensions:

Anode diameter Da=0.170" Cathodediameter Dc=0.l02" Small resonator. endv diameter Dm=0.324 Anode height =0.394" Large resonator end diameter DM=0.502"

According ,to well known empirical formulae them) forthis example would be 1.60 cm. and hence should have a value of 1.25 cm. Actually the constructed sample shows the 1r mode at 1.305 cm. with a low pulling figure of about 8 mega cycles. Open ended anodes do not decrease in pulling with increase in height, therefore, this reduction is good, indicating that the transformer slot can be widened with considerable simplification of construction.

Where 0 is the velocity of light and Qext=21r times the energy stored per cycle divided by the energy provided to the load per cycle. In an anode provided with closed ends and having approximate equality of anode height and transformer height only the central part of the anode is strongly coupled to the load due to the sinusoidal variation of the radio frequency field along the The pulling figure= 3 height. The stored energies in the open end and closed end anodes may difier for equal operating conditions, for in the closed end anode the overall size is larger and the decrease in Ee-l-Hz (tangential circumferential component of electric field and axial component of the, magnetic field) near the end plates is compensated for'bythe radial component of H which is not present in open ended anodes.

Thus, the stored energy may be as high or higher in the closed end anode and the higher Qext and the smaller pulling are accordingly understandable. The presence of the anode ends in the manner shown results in a shorter Wavelength. This arrangement may therefore also be used with existing anodes to increase the frequency of operation at the expense of slightly increased operating voltage. Thus my invention adds another variable to magnetron design, the use of closed. ends permitting improvement in either the direction of increased mode separation or lowered wavelength as may be desirable or necessary in a particular application.

Efliciencies of approximately 30% are obtainable in the 1 cm. range of wavelengths with closed end anodes constructed according to the figures given in the above example. Although I have disclosed my invention in conjunction with the Rising Sun type of anode, closed ends may be employed with magnetron anodes having any number of cavities and having cavities of any configuration.

While I have shown a single embodiment of my invention it will be apparent to those skilled in the art that many modifications and applications are possible and I do not intend my invention to be limited except by the scope and spirit of the appended claims.

I claim:

1. A magnetron anode, comprising a cylindrical body, radially disposed and inwardly extending vanes in said body, said vanes extending along less than the whole radius of the body and forming alternate like and adjacent unlike cavity resonators therebetween, said resonators being open at the ends of said body, and an end plate at each end of the body directly secured to said ends and said vanes to close said resonators, said plates being formed with a central aperture circumferentially coincident with the inner ends of said vanes.

2. A magnetron anode having alternate like and adjacent unlike cavity resonators, said resonators extending the full length of said anode, and end plates attached directly to the ends of said anode to eliminate the end space between said resonators.

3. A magnetron anode provided with a plurality of vanes, said vanes forming a plurality of cavity resonators, alternate ones'of said resonators having a like configuration, adjacent ones of said resonators having an unlike configuration, and end plates attached directly to each end of the body of said anode, said end plates completely closing the end spaces of said resonators, said end plates providing openings for the passage of a cathode.

4. A magnetron anode provided with a plurality of vanes, said vanes forming a plurality of cavity resonators, alternate ones of said resonators having a like configuration, adjacent ones of said resonators having an unlike configuration, and end plates attached directly to each end of the body of said anode, said end plates completely closing the end spaces of said resonators.

5. A magnetron anode having a plurality of cavity resonators, alternate ones of said resonators having a like configuration, adjacent ones of said resonators having an unlik configuration, and end plates attached directly to the ends of the anode to thereby avoid communication between said resonators at their ends.

6. A magnetron anode comprising an anode body having a plurality of cavity resonators therein,alternate ones of said resonators having a like configuration, adjacent ones of said resonators having an unlike configuration, said resonators being open at each end of said anode body, and end plates connected to the ends of said anode body to close the end spaces of said resonators at both ends of said anode body.

7. A magnetron anode comprising an anode body having a plurality of cavity resonators and two ends, alternate ones of said resonators having a like configuration, adjacent ones of said resonators having an unlike configuration, said resonators being open at said ends, and end plates directly soldered to said ends to eliminate the end spaces ofsaid cavity resonators.

WILLIS E. LAMB, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,154,758 Dallenbach Apr. 18, 1939 2,247,077 Blewett et al. I June 24, 1941 2,410,396 Spencer Oct. 29, 1946 2,415,470 De Vore Feb. 11, 1947 2,477,122 Garner July 26, 1949 2,523,841 Nordsieck Sept. 26, 1950 FOREIGN PATENTS Number Country Date 730,246 Germany Jan. 8, 1943