JPH0451427A - Electron gun structure of microwave tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention relates to an electron gun assembly for a microwave tube, and particularly to an electron gun assembly for generating a hollow electron beam such as a gyrotron. Regarding.

(Prior Art) As is well known, a gyrotron is an electron tube whose operating principle is cyclotron maser action, and is being used as a high-frequency high-power source in the millimeter wave to submillimeter wave band. A type of gyrotron consists of a hollow electron beam formed by a group of electrons in cyclotron motion, and an electromagnetic wave that interacts with this electron beam in a single resonant circuit such as a resonant cavity, and is accumulated in the resonant circuit. The gyromonotron, which generates oscillation when the energy of the electron beam is lost due to the electromagnetic energy generated by the electromagnetic wave, the gyroklystron, which uses a similar electron beam and multiple resonant cavities to amplify electromagnetic waves, and the similar electron beam and transmission circuit. There are gyro traveling wave tubes that interact with the traveling waves of the gyro, and backward wave gyrotrons that combine with the backward waves in the transmission circuit.

Such a gyrotron usually consists of an electron gun structure, an electron beam introduction section, a resonant cavity section, a collector section that also serves as a waveguide for guiding electromagnetic waves, an output window section, and the like.

By the way, an electron gun assembly that generates this kind of hollow electron beam has a cylindrical skirt, a band-shaped electron emitting part provided adjacent to the skirt, and a band-shaped electron emitting part provided close to the band-shaped electron emitting part on the downstream side of the beam. and a cylindrical accelerating anode coaxially disposed around the nose.

The skirt part and the nose part are essential electrodes for shaping the electron beam emitted from the band-shaped electron emitting part into a predetermined hollow shape, and their outer peripheral surfaces form a smooth continuous surface together with the band-shaped electron emission surface. must be maintained. If there are discontinuous portions in some of these surfaces, not only will beam shaping be adversely affected, but also discharge will likely occur between the accelerating anode and the opposing accelerating anode, which will have a fatal adverse effect on the operation of the microwave tube. Therefore, conventionally, these cathode components are generally integrated by soldering or the like so that no protrusions are formed at each connection portion.

(Problem to be Solved by the Invention) However, in the configuration in which the skirt portion, the band-shaped electron emitting portion, and the nozzle portion are integrated, it is easy to form a continuous surface, but on the other hand, the heat of the heater that heats the electron emitting portion is・It also affects the parts and nose of the body and heats them to high temperatures. These skirt parts and nozzle parts are made of high melting point metal such as molybdenum, and although electrons are not emitted from the surface at the initial stage of operation, barium etc. evaporate from the electron emitting part with long-term operation. There is a risk that the electron-emitting substance may adhere to the surface of these skirt portions or nose portions, causing undesired electron emission. The electromagnetic field for beam focusing of the electron gun structure is
Since there is no proper focusing effect on electrons generated from areas other than the band-shaped electron emitting portion, electrons generated from the scar 1 portion or the nose portion surface directly flow into the anode or the like.

The present invention solves the above-mentioned disadvantages, and aims to provide an electron gun structure for a microwave tube that can reliably suppress electron emission from the skirt portion, etc. other than the band-shaped electron emitting portion. shall be.

[Structure of the Invention] (Means for Solving the Problems) This invention comprises a heat shield cylinder having a plurality of turns arranged in a space between the inner circumferential wall of the skirt portion and the cathode support inside the skirt portion. This is a microwave tube electron gun structure.

(Function) According to the present invention, the heat shield cylinder is disposed between the cathode support holding the band-shaped electron emitting part and the heater and the skirt part located on the outer periphery of the cathode support, so that the temperature rise in the skirt part is prevented. This is reliably suppressed, and thermionic emission from the outer surface is almost completely eliminated. Therefore, stable operation is maintained for a long time.

(Example) An example will be described below with reference to the drawings. Identical parts are designated by the same reference numerals.

The main parts of an example in which this invention is applied to a gyrotron are shown in FIGS. 1 to 3.

Cylindrical cathode support 1 supported by cathode terminal 11
A heater 13 is embedded and held at the tip of the heater 2 . A ring-shaped electron emitting section 14 made of an impregnated cathode is supported and fixed on the outer periphery of the tip of the cathode support 12 .

The outer peripheral surface of this electron emitting section 14 is a band-shaped electron emitting surface 1
4a. A cylindrical skirt portion 15 is coaxially provided on the outer periphery of the cathode support 12, and its tip portion is folded inward close to the band-shaped electron emitting portion 14, and an edge portion 15a forms a part of the electron emitting portion 14. point or line contact with the part. A tip nose portion 16 is provided on the beam downstream side of the electron emitting portion, the lower end of which is also close to the electron emitting portion, and is folded inward so that an edge portion 16a points to a part of the electron emitting portion. Or there is line contact. These skirt parts 15,
and the nose portion 16 are both made of a high melting point metal such as molybdenum. In this way, the skirt part 15,
The outer peripheral surfaces of the band-shaped electron emitting portion 14 and the nose portion 16 form a continuous surface with a smooth slope.

Accelerating anodes 17 made of thick-walled members are coaxially disposed at predetermined intervals around the outer peripheries of these cathodes.

The outer peripheral part 17a of this accelerating anode constitutes an external terminal part, and insulating cylinders 20 and 21 made of ceramic are hermetically sealed to the upper and lower sides of the outer peripheral part 17a through sealing rings 18 and 19, respectively. Note that auxiliary rings 22 and 23 made of ceramic are arranged between the sealing ring and the outer circumference of the accelerating anode.

Therefore, in the space between the cathode support 12 and the skirt portion 15 located on the outside thereof, a heat shield tube is formed by wrapping a thin plate of a high melting point metal such as molybdenum at approximately equal intervals, for example, four times. 24 are arranged. In assembling, this heat shield tube 24 is inserted into the space between the two from below in the figure, and is held from below by three molybdenum thread-shaped holders 25, while its tip 25a is formed into a skirt section. It fits into a certain small through hole and is welded and fixed at the welding part 26.

In the heat shield cylinder 24, the innermost cylindrical part has the longest length in the axial direction, and gradually becomes shorter on the inside, corresponding to the shape of the inner space of the skirt part, so that heat from the heater part and the cathode support is absorbed. It is designed so that it is not radiated directly to the skirt part through the space. Note that the holding body 25 has an inner large diameter portion 25.
Since the b1 stopper portion 25c is provided, the heat shield tube can be stably held and easily fixed to the skirt portion. Further, a part of the heat shield cylinder is welded and fixed to a part of the holder to prevent it from undesirably moving or vibrating.

Note that the heat shield cylinder may be formed by fitting a plurality of metal cylinders with different diameters to each other to form a multiple cylindrical body.

Furthermore, a similar heat shield member can be arranged in the space between the inner circumferential wall of the nose portion and the heater portion.

During operation, the band-shaped electron emitting section is heated to a high temperature by the heater, but the skirt section, etc. is thermally shielded by the thermal silt tube and does not reach too high a temperature, and electron emission from the outer peripheral surface is reliably suppressed. .

[Effects of the Invention] As explained above, according to the present invention, the rise in temperature of the skirt portion located on the outer periphery of the cathode support holding the band-shaped electron emitting portion and the heater can be reliably suppressed. As a result, almost no thermoelectrons are emitted from the outer surface of the skirt portion. In this way, stable operation by the hollow electron beam shaped into a predetermined shape is maintained over a long period of time. Also, if you use a heat shield tube with multiple wraps,
Assembly becomes easier.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view showing the main parts of an embodiment of the present invention;
The figure is an enlarged view of the main part, and FIG. 3 is a partial perspective view. 2... Cathode support, 3... Heater, 4... Band-shaped electron emitting part, 5... Skirt part, 6... Nose part, 7... Accelerating anode, 24... Heat shield Tube.

Claims (1)

[Scope of Claims] A band-shaped electron-emitting section provided close to the skirt portion, a heater placed inside the band-shaped electron-emitting section, and a nose provided close to the band-shaped electron-emitting section on the downstream side of the beam. and a cylindrical accelerating anode coaxially arranged around these parts, and a cathode support holding the band-shaped electron emitting part and the heater is located inside the skirt part. In the gun assembly, in the space between the inner circumferential wall of the skirt portion and the cathode support,
A microwave tube electron gun assembly characterized by being provided with a heat shield tube.