JPH0330239A - Grid-type electron gun - Google Patents

Abstract

PURPOSE:To prevent plastic deformation of a grid caused by concentration of stress due to thermal expansion by a method wherein a grid-type electron gun is constituted so that the shape of the grid is spiral. CONSTITUTION:A cathode 1 heated by a heater 6 generates thermions wherein current flow 5 due to these thermions is accelerated by an anode 2 extracted by a control grid 3. In order to reduce collision amount against the control grid 3, a shadow grid 4 is provided. These grids 3, 4 receive radiation from the cathode 1 and generate heat with collision of the current flow 5 to be high in temperature and elastically deformed by thermal expansion. However by making the control grid 3 and the shadow grid 4 spiral, the direction of deforming force can be dispersed into grid faces. Thus concentration of stress can be prevented to prevent plastic deformation from being reached.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a grid-type electron gun used in a microwave electron tube.

[Conventional technology]

Grid-controlled electron guns with grids are often used as electron guns for beam-type microwave electron tubes because they are easy to control output and have good cutoff characteristics in pulse operation. FIG. 3(A) is a cross-sectional perspective view showing a conventional grid-type electron gun shown in, for example, U.S. Pat. No. 4,321,505.
Figure 3 (CB) is a partially enlarged sectional view;
) is a simplified plan view of the grid plane viewed from above. In the figure, 1 is a cathode that emits electrons, 2 is an anode that accelerates electrons, and 31 is a mechanism that extracts the emitted electrons. 'lil grid, 4l is a shadow grid that forms the shadow of the electron flow, 5 is the electron flow (inside the broken line in the figure), and 6 is the heater.

Next, the operation will be explained. The cathode 1 is heated by a heater 6 and emits a large amount of thermoelectrons. These thermoelectrons are transferred to the control grid 3 by the electric field between the control grid 31 and the cathode l.
It is pulled out to the 1st side. The electron flow 5 due to the extracted thermoelectrons passes through the control grid 31 and is further accelerated toward the anode 2 . Here, in order to suppress the amount of electron flow 5 emitted from the cathode 1 that collides with the control grid 31,
Some devices are provided with a shadow grid 4l near the surface of the cathode 1, which plays the role of creating a shadow of the electron flow 5 with respect to the control grid 31 (FIG. 3(B)). The control grid 3l and the shadow grid 4l are generally formed by processing a high melting point metal such as molybdenum or tungsten. The shape is formed radially and concentrically from the center of the cathode l along the spherical surface of the cathode l, as shown in FIG. 3(C). Also, each grid 31.41 has a cathode l
The structure is such that it is supported from the outside around the periphery.

[Problems to be Solved by the Invention] Since the conventional grid-type electron gun is configured as described above, during operation, the electron flow 5 collides with the shadow grid 4l and the control grid 3l, and the radiation is emitted from the cathode 1. The stress generated by the thermal expansion concentrates toward the center and causes plastic deformation, which disturbs the high-precision alignment and changes the electron trajectory.As a result, the electron tube characteristics deteriorate. Furthermore, there were other problems such as the possibility of accidents due to heat generation and overload of the power supply. Also, if the deformation becomes severe, the grids will come into contact with each other! There was a topic.

This invention is like the above! ! ! ! The purpose was to obtain a grid-type electron gun in which the grid is less susceptible to deformation due to thermal expansion. [Means for Solving the Problems] A grid-type electron gun according to the present invention has a grid in which the grid pieces are spirally arranged from the periphery of the cathode toward the center.

[For production]

In the grid according to the present invention, each grid piece has a spiral shape, so stress due to thermal expansion is easily released within the grid plane, thereby making it difficult for plastic deformation to occur.

〔Example〕

An embodiment of this invention will be explained below with reference to the drawings. 1st
In the figure, 3 is a control grid formed in a spiral shape;
4 is a shadow grid having the same shape as the control grid 3; Other parts are the same as those shown in Figure 3 with the same symbols. Next, we will explain the operation. The cathode l heated by the heater 6 generates thermoelectrons. This electron flow 5 due to thermionic electrons is drawn out to the control grid 3 and accelerated at the anode 2. A shadow grid 4 is provided to reduce the amount of collision of the electron flow 5 with the control grid 3;
These grids 3.4 generate heat by receiving radiation from the cathode 1, and also generate heat by collision with the electron stream 5. Therefore,
Each grid 3, 4 becomes hot and elastically deforms due to thermal expansion. However, as shown in FIG. 1(C), the spiral control grid 3 and shadow grid 4 can disperse the direction of the deformation force within the grid plane, preventing stress concentration and leading to plastic deformation. can be prevented.

Furthermore, for the same reason, plastic changes are less likely to occur under thermal stress due to repeated operation and stop.

In the above embodiment, a shadow grid type electron gun having two grids 3.4 was explained, but FIG.
As shown in A) to (C), a negative grid type electron gun with one grid 3 may be used, and the same effects as in the above embodiments can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, since the grid-type electron gun is subjected to tI so that the grid has a spiral shape, the grid is not plastically deformed due to stress concentration due to thermal expansion, and high precision is achieved. This has the effect of providing highly reliable products.

[Brief explanation of drawings]

FIG. 1(A) is a cross-sectional perspective view showing a grid-type electron gun according to an embodiment of the present invention, FIG. 1(B) is a partially enlarged cross-sectional view of FIG. 1(A), and FIG. 1(C) 2 is a plan view showing a simplified grid surface, and FIGS. 2(A), 2(B), and 2(C) are a sectional perspective view, a sectional view, and a plan view showing a grid-type electron gun according to another embodiment of the present invention, respectively. , Figure 3 (A), (B
). (C) is a cross-sectional perspective view, a cross-sectional view, and a plan view, respectively, showing a conventional grid-type electron gun. 1 is a cathode, 2 is an anode, 3 is a control grid, 4 is a shadow grid, and 5 is an electron flow. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] a cathode that emits electrons; a grid in which a plurality of grid pieces are spirally arranged from the periphery of the cathode toward the center and provided on the top of the cathode to extract the emitted electrons; and a grid that extracts the emitted electrons; A grid-type electron gun equipped with an anode that accelerates electrons.