JP2827678B2 - Microwave tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a microwave tube.

[0002]

2. Description of the Related Art A microwave tube is a kind of electron tube and is used in a wide range of fields such as a microwave communication network, radar and satellite broadcasting. Such a microwave tube is a vacuum tube in which the inside is made to have a high vacuum and a signal is amplified or oscillated by utilizing an interaction between an electron beam and a microwave. Therefore, it is necessary to maintain a high vacuum in the tube at all times. For this purpose, materials to be used are selected, and surface treatment of parts is strictly performed to prepare for gas generation.

[0003] Nevertheless, during the operation of the traveling wave tube, it is inevitable to release a small amount of gas from the inner parts of the tube or the inner wall of the airtight container.
Generally, a getter, which is a component for collecting the gas, is incorporated.

[0004] One of the getters used for such a purpose is a non-evaporable getter, which is Ti, Zr, Ta, Th, V
Metals active on isogas molecules and atoms are made into a plate or powder sintered body, and gas is collected by adsorption on the surface and diffusion inside.

Among these, non-evaporable getters mainly used in microwave tubes include Zr (zirconium) -based Zr-C (zircon carbon) getters, Zr-Al getters, and Zr-V-Fe getters. is there. The Zr-based getter has a function of releasing H during the evacuation and operation of the microwave tube.
_{2 It} is characterized by a particularly high absorption capacity for (hydrogen gas).

[0006] Such a non-evaporable getter (hereinafter referred to as getter).
In use of this gas, this getter
The lower the temperature near normal temperature, the more gas is absorbed,
At a temperature of 600 ° C. or higher, hydrogen is released. This is hydrogen
Is fixed in the form of hydride with getter material (zirconium)
Reversible reaction type that decomposes and releases hydrogen at high temperature
By absorbing. On the other hand, gases other than hydrogen, for example,
CO, CO ₂ , N ₂ , O _2, etc. are ZrC, Z
Make relatively stable compounds such as rN, ZrO ₂
An irreversible reaction-type absorption of immobilization occurs. Because of this hydrogen
For other gases, the higher the temperature, the higher the gas absorption rate,
The amount increases. Therefore, getter is 200 ~ 300 ℃
Most often used for hydrogen and other gases
Efficient and relatively high temperature inside the microwave tube
Select and attach parts that do not affect the electron beam or insulation
You. Generally, with the cathode room and the collector of the electron gun
Near is selected.

In using these getters,
The getter is heated to a predetermined temperature in a vacuum to remove a protective layer previously formed on the surface of the getter material and perform an activation process for expressing the getter function. In the activation process, the hydrogen (hydride) absorbed by the getter is thermally decomposed and released outside the getter, and other gases are diffused and absorbed inside by the concentration gradient. In commercial getters, Zr-
Al type, Zr-C type (high temperature activation type) and Z around 500 ° C
An r-V-Fe (low-temperature activation type) is known.

Particularly, a low-temperature activation type getter has an activation temperature at an exhaust baking temperature of a general microwave tube (500 degrees).
６００600 ° C.), so that heating for activation is not particularly necessary. In addition, this getter does not absorb hydrogen for a large amount of hydrogen gas released from the microwave tube in the exhaust baking process because the temperature is in a temperature range in which hydrogen is released at this temperature.

On the other hand, at this time, the high temperature activation type getter absorbs about 10% of the hydrogen at the time of full activation in the exhaust baking process. In a model with a Zr-based getter, the amount of hydrogen absorption is extremely large at a maximum of 20 cc Torr / mg after complete activation, so that a very large amount of hydrogen (2 cc Torr) even at 10% activity.
/ Mg), and this hydrogen is released by activation heating after evacuation, which is a problem described later.

[0010]

As a drawback when a non-evaporable getter is used for a microwave tube, there are various problems due to hydrogen released during activation as described below. That is, since the getter activity is performed in the final step of the exhaust,
From the viewpoint of ensuring the quality of the microwave tube, it is desired to quickly activate (dehydrogen) while maintaining the degree of vacuum in the tube within a predetermined limit. However, since the getter emits a large amount of hydrogen, the activation heating has to be slowed down, which may take ten and several hours. In particular, in a millimeter-wave microwave tube having a high working frequency, the inside diameter of the cross section of the above-described slow-wave circuit is on the order of several millimeters, and the exhaust resistance is several times greater than in the past. Also, under certain conditions, when the getter material layer is reabsorbed and a sudden exothermic reaction occurs and the getter material layer cracks due to thermal stress,
In some cases, it adversely affected the cathode and the like. Also electronic
It is common practice to have multiple getters to extend the life of the tube.
In this case, only low-temperature getters are used
As described above, gases other than hydrogen during exhaust baking
There is a problem that getter ability is reduced by absorption.
Was. Especially for high-reliability, high-power microwave electron tubes.
In some cases, exhaust baking may be performed
Low-temperature getter activated at baking temperature
There was an inconvenience that the points were rather damaged.

[0011]

According to the microwave tube of the present invention, one of the cathode side and the collector side, which is farther from the exhaust pipe, is separated from the cathode side or the collector side by a slow wave circuit or a cavity having a large exhaust resistance. In other words, the exhaust baking temperature (approximately 500 ° C.) for those who have a large exhaust resistance and are more difficult to discharge gas in the pipe.
Then, a low-temperature active getter that absorbs less hydrogen is installed.
On the other hand, a high-temperature activation type getter that does not reach the activation (degassing) temperature but absorbs a large amount of hydrogen due to partial activation facilitates the discharge of hydrogen gas released during the subsequent activation (about 950 ° C.). It is mounted on the front side of the slow wave circuit or cavity where the exhaust resistance is small. In other words, the high-temperature active getter is mounted on the electron gun and the collector on which the exhaust pipe is mounted, and the low-temperature active getter is mounted on the other side.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a traveling wave tube showing a first embodiment of the present invention. This microwave tube is called a coupled cavity traveling wave tube, 1 is an electron gun unit, 2 is a slow wave circuit unit, and 3 is a collector unit. Here, two non-evaporable getters are used, and the low-temperature active type getter 4a of the electron gun section is a ST172 series getter sold by Saes Getters, Italy. On the other hand, the high-temperature active type getter 4b of the collector is a getter of the ST171 series of SAES Getters. These are accommodated in an airtightly joined container, and an exhaust pipe 5 made of an oxygen-free copper pipe is attached to the collector section 3.

Each of the two getters has a built-in heater for activation, and its lead wires are insulated from each other and are connected to the external lead-out electrodes 6a and 6b provided at the respective mounting positions by resistance welding. It is connected. At the same time the getter is held in the tube with this lead. Since the assembling of the traveling wave tube and the exhaust baking process are completely the same as those in the related art, the description thereof is omitted.

After the evacuation, when the bulb temperature reaches about 300 ° C., a predetermined current is applied to the low-temperature active getter 4a,
Activate by heating. At this time, the release of gas was as small as 1/10 or less as compared with the conventional getter. Next, while keeping the temperature of the getter at 400 ° C.,
Activate b. At this time, a considerably large amount of hydrogen is released.
Activation (outgassing) was completed in 2 hours. Thereafter, through the same steps as those of the conventional traveling wave tube, such as the activity of the cathode, a coupled cavity traveling wave tube was completed.

FIG. 2 is a longitudinal sectional view showing the structure of a klystron according to a second embodiment of the present invention. Numeral 11 denotes an electron gun and numeral 12 denotes a cavity. This klystron has six resonant cavities. 13 is a collector unit. Here, an exhaust pipe 14 is attached to the tip of the electron gun section 11, and the first
ST17 marketed by SAES Getters, Inc.
A series of high temperature active getters 15b (Zr-C based) were mounted under the cathode room.

On the other hand, for the collector section 13, a tape-shaped low-temperature active type getter 15a (ST707 series manufactured by SAES Getters Co., Ltd.) in which a getter material powder is sintered and fixed on the surface of a metal tape is used. Since this getter does not have a heater for heating and activates only by exhaust baking heating, the getter exerts a sufficient getter effect. Therefore, the getter was inserted into the gap between the collector electrode and the envelope as shown in the figure and fixed by spot welding. The process of assembling and exhausting the klystron is the same as that of the conventional one and will not be described.

After the exhaust baking, the high-temperature active type getter 15b attached to the electron gun section 11 is energized to a temperature of 900.degree.
Hold for 0 minutes to activate. After evacuation was performed until the degree of vacuum in the pipe reached a predetermined value, the exhaust pipe 14 was cold-pressed to produce a sealed pipe. Thereafter, the klystron was completed by finishing, finishing, and adjusting in the same manner as in the conventional klystron manufacturing process.

[0018]

As described above, according to the present invention, a low-temperature active type getter which has a small amount of hydrogen absorption in an exhaust process is provided on the opposite side of a slow-wave circuit portion or a cavity portion having a large exhaust resistance. The high-temperature active type getters are mounted on the front side of the section, respectively, so that the exhaust efficiency is improved even in the situation where the exhaust resistance has to be several times larger than that of the conventional microwave band electron tube like the millimeter wave band electron tube There is a great merit in that it is performed in a dynamic way. In particular, it has been confirmed that the low-temperature active type getter mounted opposite the high exhaust resistance portion operates as a built-in mini-pump during exhaust, so that the degree of vacuum in the tube is improved and adverse effects on the cathode and the like are reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a structure of a traveling wave tube according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a structure of a klystron according to a second embodiment of the present invention.

[Explanation of symbols]

 1,11 electron gun section 2 slow wave circuit section 12 cavity section 3,13 collector section 4a, 15a low temperature activation type getter 4b, 15b high temperature activation type getter 5,14 exhaust pipe 6a, 6b extraction electrode

Claims (1)

(57) [Claims] 1. A These provided with a slow wave circuit portion or the cavity portion between the electron gun portion and the collector portion is accommodated in an airtight container integral to either one of the electron gun unit or collector portion of said airtight container in a microwave tube the exhaust pipe is attached, together with the activation temperature in front of the viewed from the exhaust pipe the slow wave circuit portion or the cavity portion is disposed a non-evaporable getter above 700 ° C., the slow wave A microwave tube having a non-evaporable getter having an activation temperature of 600 ° C. or lower disposed on the other side of the circuit or cavity .