# US 4,395,656 A · Gyrotron transmitting tube

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- Number: US 4,395,656 A
- Document ID: US4395656A
- Status: Granted
- Kind: A
- Application number: 06/220,212
- Filed: 1980-12-24
- Granted: 1983-07-26
- Earliest claimed: 1980-12-24
- Assignees: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
- Inventors: Henry G. Kosmahl
- Web page: https://patentgrep.com/patent/US4395656A

## CPC

- H01J 25/025: {with an electron stream following a helical path}
- Y10S 505/88: Inductor
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

An improved R.F. transmitting tube for the 20 GHz to 500 GHz range comprises a gyrotron (10) and a multistage depressed collector (11) as shown in FIG. 1. A winding (19) provides a magnetic field which acts on spent, spinning or orbiting electrons changing their motion to substantially forward linear motion in a downstream direction. The spent electrons then pass through a focusser (18) into the collector (11). Nearly all of the electrons injected into the collector will remain within an imaginary envelope designated by dashed lines 8 and 9 as they travel forward toward the end collector plate (26). The apertures in the collector plates (22-25) are at least as large in diameter as the envelope (8,9) at any particular axial position. FIG. 2 illustrates magnetic field strength from the cathode (13) of FIG. 1 to the collector entrance in focusser 18.

## Claims

### Claim 1

An electromagnetic wave generator operating in the 20 GHz to 500 GHz range and comprising:
a gyrotron tube having an electron emitting cathode at one end;
an electron collector disposed at the other end of said gyrotron tube, said other end having disposed thereat a focusing ring through which electrons are injected into said collector;
a solenoid disposed around said gyrotron tube establishing a first magnetic field which causes electrons emitted by said cathode to follow helical paths; and
means for establishing a second magnetic field between said first magnetic field and said focusing ring, said second magnetic field being characterized by decreasing from the B value of said first magnetic field to substantially zero over an axial distance of from 1.lambda..sub.c to 3.lambda..sub.c in a direction away from said cathode, and at such a rate as to establish optimum conversion of spiral energy of the spent electrons into forward motion.

### Claim 2 (depends on 1)

The generator of claim 1 wherein said focusing ring is a coil having a d-c current flowing therethrough.

### Claim 3 (depends on 1)

The generator of claim 1 wherein said means for establishing a second magnetic field comprises a coil disposed around said gyrotron between said solenoid and said collector.

### Claim 4 (depends on 1)

The generator of claim 1 wherein said collector is a multistage depressed collector.

### Claim 5 (depends on 4)

The generator of claim 4 wherein said multistage depressed collector comprises a plurality of centrally apertured plates bowed toward said cathode and a conical end electrode having a spike extending from its apex toward said cathode.

### Claim 6 (depends on 5)

The generator of claim 5 wherein the aperture diameters increase at a rate at least as great as the rate of expansion of an imaginary envelope within which 90 percent of the electrons injected into said collector would be contained before falling back onto the collector plates.

### Claim 7 (depends on 1)

The generator of claim 1 wherein said means for establishing a second magnetic field comprises a permanent magnet surrounding said gyrotron.

### Claim 8 (depends on 1)

The generator of claim 1 wherein said means for establishing a second magnetic field comprises a superconducting magnet.