US2669674A

US2669674A - Traveling wave tube

Info

Publication number: US2669674A
Application number: US107287A
Authority: US
Inventors: Diemer Gesinus
Original assignee: Hartford National Bank and Trust Co
Current assignee: Hartford National Bank and Trust Co
Priority date: 1948-09-09
Filing date: 1949-07-28
Publication date: 1954-02-16
Anticipated expiration: 1971-02-16
Also published as: GB682515A; NL80722C; NL142247B; CH275641A; FR994736A; DE807518C; BE491016A

Description

Feb. 16 1954 I DIEMER 2,669,674

TRAVELING WAVE TUBE Filed July 28, 1949 IN VEN TOR.

Gmsmvs DIEMER,

fi m #4 AGENI Patented Feb. 16, 1954 TRAVELING WAVE TUBE Gesinus Diemer, Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 28, 1949, Serial No. 107,287

Claims priority, application Netherlands September 9, 1948 1 Claim.

This invention relates to arrangements for amplifying centimeter and decimeter waves, comprising a travelling wave tube, that is an electron tube in which an electron beam is adapted to interact with an electromagnetic wave adapted to travel along one or a plurality of helical conductors.

In order to avoid oscillations, it is known to make the helical conductor from material of poor electrical conductivity. More particularly if the helical electrode is provided inside the tube, it is almost impossible afterwards to vary the damping of the helix to be matched to the operating conditions of the tube. The present invention provides means for varying the damping, if desired, during the operation of the tube.

According to the invention an arrangement for amplifying centimeter and decimeter waves, comprising an electron tube in which an electron beam is adapted to interact with an electromagnetic wave adapted to travel along one or more helical conductors is characterized in that a layer of a material of poor electrical conductivity, i. e. a material having a resistance of about 0.1 to ohms per cubic centimeter, is provided in the vicinity of the helix and outside the tube. The simplest embodiment of the invention is that in which the layer of poor conductivity (for example graphite obtained from a colloidal solution) is provided directly on the outer side of the wall of the tube. The damping may be varied and be provided at any desired area along the helix by enlarging the said layer, partly wiping it off or a similar operation. Preferably, however, the layer of the material of poor conductivity is provided on a cylinder which is slidable about the tube, so that the damping may be provided at any desired area, whereas the value of the damping may be varied by screening part or all of the layer of the material of poor conductivity with respect to the tube by means of a cylinder of conductive material. If the layer of poor conductivity occupies the whole surface of the cylinder, the screening operation requires to be effected by a sliding movement of the conductive cylinder. If, however, the layer of poor conductivity occupies only a portion of the cylinder, the screening effects may be obtained by rotational movement of a conductive part of this cylinder, by which the control of the apparatus during its use is simplified considerably.

The invention will now be explained more fully by reference to the accompanying drawing showing diagrammatically, by way of example, part of one embodiment of the arrangement for amplifying centimeter or decimeter waves according thereto.

In the figure, the reference numeral I designates the glass wall of a tube. one end of which contains an incandescent cathode 2. a so-called Wehnelt cylinder 3 and a suction anode 4, which anode 4, during operation of the tube, has a positive potential relative to the cathode 2. An electron beam is produced which moves in the direction of two cylindrical electrodes 5 which are connected to the exterior and between which a helix 1 is provided. The electron beam is collected by an electrode 6. Each extremity of the helix is surrounded by a waveguide 8, 9 respectively, provided outside the tube. Between the two waveguides the tube is surrounded by a conductive cylinder i0. Reference numeral ll designates a coil which serves to generate a magnetic field in the direction of the axis of the tube. The tube is surrounded by a glass cylinder l2, which is internally covered with a layer of graphite. A copper cylinder I3 is adapted to be introduced into the cylinder I2. Damping may be provided at any desired area of the helix over a length not greater than that of the cylinder I2 by sliding the cylinders I2 and I3 by means of operating members (not shown).

What I claim is:

A travelling wave tube for amplifying short waves comprising a tubular envelope, 9. conductive helix disposed within said envelope, means to direct an electron beam along the axis of said helix disposed within the envelope, and means for varying the attenuation of said tube, said latter means comprising a hollow cylindrical member outside of and surrounding said envelope and said helix and adapted to slide thereabout, a layer of a material of poor electrical conductivity on the inner surface of said hollow member, and a second cylindrical member of conductive material surrounding said envelope and adapted to be inserted into said hollow member whereby the portions of said layer covered by the conductive member are screened from the helix.

GESINUS DIEME'R,

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,197,123 King Apr. 16, 1940 2,300,052 Lindenblad Oct. 27, 1942 8 Di Toro Dec. 31, 1946 2,541,843 Tiley Feb. 13, 1951 2,575,383 Field Nov. 20, 1951 2,585,582 Pierce Feb. 12, 1952 FOREIGN PATENTS Number Country Date 934,220 France Jan. 7, 1948 OTHER REFERENCES Article by A. V. Hollenberg, pp. 52-58, Bell System Tech. Jour. for January 1949.