JPH0552015B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a collector for a straight beam type ultra-high power microwave tube.

A high-power microwave tube consists of an electron gun section that generates an electron beam, a high-frequency circuit section that converts the energy of the electron beam into high-frequency energy, a collector section that captures the electron beam, and a beam focusing device that focuses the electron beam. It is the main component.
Ultra-high power microwave tubes handle much more power than ordinary high-power microwave tubes, and the amount of power is several
Ranging from 100kW to several 10Mw (mega watts). In addition to continuous wave operation, such ultra-high power microwave tubes also include pulse operation. Even in the case of pulse operation, the pulse width ranges from several microseconds to several microseconds. Ten
There are cases of short pulses of msec, cases of long pulses whose pulse width is from several seconds to several tens of seconds, and of course cases of pulse widths in between. The present invention relates in particular to collectors for long-pulse operation, straight-beam ultra-high power microwave tubes.

A conventional collector structure of this type of microwave tube is shown in FIG.

In order to efficiently release the huge amount of heat generated in the collector (for example, several megawatts x several seconds) to the outside,
As a cooling method, an evaporative cooling method is normally used. In FIG. 1, 1 is an electron beam entrance hole, and 2 is an electron beam. 3 indicates a collector core, which performs electron beam trapping and forms part of the vacuum vessel. A large number of radially formed heat sinks 4 are installed outside the collector core 3. Power loss in the collector is several megabytes
It is very large, and the shape of the collector becomes very large in the case of long pulse operation (for example,
(diameter: 500 mm, height: 1,500 mm) Since it is difficult to process the collector as a single piece, the collector is usually divided into several pieces, manufactured individually, and then used by joining them together (for example, by brazing). FIG. 1 shows an example in which the collector is divided into four parts in the axial direction. Further, 5 indicates a jacket installed outside the collector, and the space between the collector core 3 and the jacket 5 is filled with distilled water 6.
filled with When the electron beam 2 enters, the kinetic energy of the electron beam is converted into thermal energy by the collector core 3, which converts water into steam through the heat sink 4, and releases the heat to the outside as heat of vaporization. be. A cross-sectional view of the outermost portion of the collector shown in FIG. 1 is shown in FIG.

The following drawbacks have been found in the conventional structure of this type of long-pulse operation ultra-high power microwave tube. In other words, after a relatively small number of beam applications are repeated, vacuum breakage (leakage) occurs from the joint between the collector and core 3 (section a or b in Figure 1), causing the microwave tube to operate instantly. It makes it impossible.

The inventors investigated the causes of these accidents and found the following. In other words, the temperature inside the collector core 3 increases within a few seconds after the beam is applied.
The temperature reaches around 500℃. On the other hand, since the outside of collector core 3 is in direct contact with water, its temperature is approximately
The temperature is 100-130℃. Due to this temperature difference between the inside and outside, the collector core 3 tends to be thermally deformed so that the inside of the core is warped. This thermal deformation occurs if the heat sink 4
If the mechanical rigidity of the collector core can be ignored, the beam will deform in a manner that roughly corresponds to the beam input distribution, but in reality, the mechanical rigidity of the heat sink 4 is so large that the heat sink 4 has a rib against the thermal deformation of the collector core. It acts as a reinforcement (reinforcing body), and places where thermal deformation can occur are concentrated in areas where there is no heat dissipation body 4, in other words, in the joint between the collector and the core. FIG. 3 shows changes in the collector shape before and after thermal deformation in a conventional collector. The solid line shows the shape before thermal deformation, and the dotted line shows the shape after thermal deformation. During thermal deformation, a tensile force is applied to the outside of the collector core at the joint (the part without a heat sink), and the collector core is
It can be seen that compressive force acts on the inside of the core. In the case of a microwave tube with long pulse operation, for example, if the pulse operation is performed with a beam application time of 10 seconds and a beam OFF time of 150 seconds, the thermal deformation described above will be 160 seconds.
This process is repeated every second, causing fatigue in the metal and eventually causing a crack, which progresses and eventually leads to vacuum failure.

An object of the present invention is to provide a collector for a microwave tube having a structure that is much more durable than the conventional collector, for use as a collector for a long-pulse operation ultra-high power microwave tube.

When looking at the circumferential section of the heat radiator, the heat radiator is divided into smaller parts in the tube axis direction and the direction perpendicular thereto than before, thereby increasing the mechanical rigidity of the heat radiator to the collector.
This method weakens the core significantly compared to that of the core. An embodiment of the present invention is shown in FIG. 6, in comparison with FIG. 5 of the prior art, showing how the heat sinks are lined up on the surface of the collector core. In Figure 6, the circumferential dimension (a in the diagram) of each heat sink is approximately 1/2 or less of the thickness of the collector core (t in the diagram), and the vertical dimension (b in the diagram) is t. The feature is that it is set to approximately twice or less than the actual value.

Next, differences between the present invention and the prior art will be explained. First, the conventional design policy for heat radiators was to mainly focus on ensuring heat dissipation characteristics, resulting in large rigidity of the heat radiator; however, in the present invention, thermal stress They are fundamentally different in that they are designed with a focus on mitigation. For this reason, in the prior art, the above t,
There are no restrictions between a and b. In addition, most conventional microwave tubes have an output level of several tens of kilowatts, so the collector can also be small.
The collector core could be fabricated as one piece. For this reason, problems such as splitting the collector core or leakage from the brazed portions associated with this have rarely occurred. Furthermore, in the case of long pulse operation, the aforementioned thermal fatigue problem arises.
In the prior art, no consideration was given to these problems. According to the present invention, it is possible to obtain a collector structure that is highly effective in solving these problems.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing a conventional collector structure, FIG. 3 is a cross-sectional view showing thermal deformation of a conventional collector, FIG. 4 is a cross-sectional view showing a collector structure according to the present invention, and FIG. 5 6 shows an external view of a heat radiating body of a conventional collector, and FIG. 6 shows an external view of a heat radiating body according to the present invention. 1...Electron beam entrance hole, 2...Electron beam,
3... Collector core, 4... Heat sink, 5... Jacket, 6... Distilled water.

Claims (1)

[Claims] 1. In a straight beam microwave tube composed of an electron gun section, a high frequency circuit section, a collector section, a beam focusing device, etc., the collector is of an evaporative cooling type, and the collector is composed of a plurality of members. It has a structure that is divided and manufactured individually and then hermetically sealed together, and each collector member consists of an annular or conical annular collector core and a plurality of heat sinks arranged radially outside the collector core. The dimension in the tube axis direction of the circumferential cross section of each heat radiator is b, the dimension in the direction perpendicular to the tube axis is a,
A microwave tube characterized in that it has a dimensional ratio of a1/2t and b2t, where t is the thickness of the collector core.