JPH05182619A - Rotating cathode x-ray tube - Google Patents

Abstract

PURPOSE:To perform the baking of an insulator, which supports a fixed anode of a rotating cathode X-ray tube, efficiently. CONSTITUTION:An infrared ray transmitting plate 6 is arranged in the periphery of an insulator 5, and an infrared ray heater 7 is arranged in the periphery of the infrared ray transmitting plate 6. Furthermore, a reflecting mirror 8 is provided in the periphery of the infrared ray heater 7. The infrared ray emitted from the infrared ray heater 7 directly passes through the infrared ray transmitting plate 6 and directs the surface of the insulator 5, or the infrared ray emitted from the infrared ray heater 7 is reflected by the reflecting mirror 8 to pass through the infrared ray transmitting plate 6 and directs the surface of the insulator 5. The surface of the insulator 5 is heated for baking treatment by this irradiation of the infrared ray. Deposition of the evaporation powder of the infrared ray heater 7, which is heated in the vacuum, to the surface of the insulator 5 is prevented by the infrared ray transmitting plate 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary cathode provided with an electron emitting portion for X-ray generation in an annular vacuum container surrounding the subject, and a rotary cathode disposed opposite to the rotary cathode. The present invention relates to a rotating cathode X-ray tube equipped with a fixed anode that converts electrons into X-rays, and more particularly to baking an insulator that supports a fixed anode that is kept at a high potential during thermionic emission.

[0002]

2. Description of the Related Art A gas discharged from a vacuum container or a vacuum internal structure in vacuum lowers the degree of vacuum and promotes spark discharge. Therefore, in order to reduce the amount of gas released into the vacuum, baking of the vacuum container or the structure inside the vacuum, that is, so-called gas discharge processing is performed before using the vacuum device. The treatment is also performed on a medical X-ray tube utilizing vacuum insulation.

A generally known medical X-ray tube, as shown in the schematic cross-sectional view of FIG. 7, has a filament 18 for emitting thermoelectrons in an envelope 17 of a glass bulb to be evacuated, and this filament. The anode 19 is disposed opposite to 18 and converts the thermoelectrons into X-rays. Reference numeral 20 indicates a focusing electrode that focuses the thermoelectrons. The baking for such a medical X-ray tube is performed as follows. The entire envelope 17 is heated from the surroundings, and the envelope 17 and the filament 18 are heated.
The temperature of the anode 19 is raised, and the gas molecules adsorbed on these surfaces are desorbed while exhausting.

[0004]

By the way, a rotary cathode X-ray tube as a medical X-ray tube which has been proposed in recent years has an annular shape as shown in the longitudinal sectional view of FIG. Inside the vacuum container 1, an annular rotating cathode 3 having a filament 2 for emitting thermoelectrons for X-ray generation, an annular fixed anode 4 for receiving thermoelectrons and generating X-rays, and a fixed anode 4 are provided. The supporting insulator 5 is provided, and the electric power from the external power sources 13 and 14 is supplied to the filament 2 through the power feeding brush 15 and the slip ring 16 to emit thermoelectrons.

As described above, as compared with the conventional medical X-ray tube shown in FIG. 7, the volume of the vacuum container 1 and the size of the internal structure (fixed anode 4, rotating cathode 3, etc.) of the container are extremely large, and the baking treatment is performed. When the method of heating the entire envelope (vacuum container 1) as applied to a conventional medical X-ray tube is used, the heating time and the heat consumption required for heating become enormous, and the rotating cathode 3 May cause problems such as thermal expansion and deformation.

Therefore, at least the vacuum container 1, the fixed anode 4,
It is conceivable that only the porous insulator 5 having a larger amount of gas molecules adsorbed is baked as compared with the metal material such as the rotating cathode 3. However, in the rotary cathode X-ray tube shown in FIG. 6, even when only the insulator 5 is heated, the attachment site of the insulator 5 must be intensively heated from the outside of the vacuum container 1 and the thermal conductivity is high. It is impossible to efficiently heat the entire insulator 5 having a low temperature.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a rotating cathode X-ray tube capable of efficiently baking an insulator.

[0008]

In order to achieve the above object, the present invention has the following constitution. That is, according to the present invention, an annular fixed anode supported by an insulator is provided inside an annular vacuum container surrounding the subject, and thermoelectrons for generating X-rays are emitted toward the fixed anode. In a rotary cathode X-ray tube having a rotary cathode provided with a filament, a heater is installed in a space around the insulator, and an annular infrared transmitting plate is installed between the heater and the insulator. And

[0009]

The function of the present invention is as follows. Infrared rays emitted from the heater pass through the infrared ray transmitting plate and are applied to the insulator. This radiant heat raises the temperature of the insulator, and the gas molecules adsorbed on the surface are desorbed. Since it is heated not by the outside of the vacuum container but by the heater arranged in the space around the insulator, the temperature of the insulator rises uniformly and in a short time. In the process of degassing by heating as described above, the heater in a vacuum may evaporate, and evaporated powder may be deposited around the insulator, significantly impairing the electrical insulation of the insulator. Therefore, an infrared transmitting plate is arranged between the heater and the insulator to guide only infrared rays to the insulator to block vapor deposition powder.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partial vertical cross-sectional view of a rotary cathode X-ray tube according to this embodiment, in which the same reference numerals as those in FIG. 6 as a conventional example indicate the same components. An annular rotary cathode 3 having a filament 2 for X-ray generation mounted inside an annular vacuum container 1 made of stainless steel that has been evacuated, and an annular fixed anode fixedly installed so as to face the rotary cathode 3. 4 and 4 are deployed. Reference numeral 12 is an electromagnet device that includes an electromagnet that magnetically levitates the rotating cathode 3 and a stator that generates a rotating magnetic field to drive the rotating cathode 3 to rotate.

During X-ray photography, the filament 2 is heated by supplying electric power from a power source (not shown) to the rotating cathode 3 to heat the filament 2, and by applying a potential difference between the rotating cathode 3 and the fixed anode 4. Thermionic electrons are emitted from the fixed anode 4 toward the fixed anode 4, and X-rays are generated from the fixed anode 4. Since the fixed anode 4 has a high electric potential when the thermoelectrons are emitted, it is attached to the inner wall surface of the vacuum container 1 through the plurality of insulators 5.

As shown in FIG. 2, which is a schematic cross-sectional view taken along the line AA of FIG. 1, an annular infrared transmitting plate 6 is provided around each insulator 5 so as to surround it. The infrared transmitting plate 6 is formed of a transparent member such as quartz glass, and is configured to transmit infrared rays emitted from an infrared heater 7 arranged around the infrared transmitting plate 6 and guide the infrared rays to the insulator 5. There is. Further, an annular reflecting mirror 8 having an inner peripheral surface formed in a parabolic shape is installed around the infrared heater 7. A terminal of the infrared heater 7 is connected to an AC power source 9 provided outside the vacuum container 1, and a switch 10 is attached in the middle of the circuit.

Baking of the insulator 5 having such a structure is performed as follows. The switch 10 is operated to connect the AC power source 9 and the infrared heater 7, and the infrared heater 7 is heated to emit infrared rays. As shown in the cross-sectional view of FIG. 4, the infrared rays radiating around the infrared heater 7 directly go to the insulator 5 through the infrared transmitting plate 6 or are parallel to the parabolic inner peripheral surface of the reflecting mirror 8. Is reflected by the infrared ray transmitting plate 6 toward the periphery of the insulator 5. By this infrared irradiation, the temperature of the surface of the insulator 5 rises uniformly, and the gas molecules adsorbed on the porous surface are desorbed and released.

The time required for baking is not constant,
This is performed until the desorbed gas molecules are exhausted and the degree of vacuum is restored to some extent. In the meantime, the infrared heater 7 heated in vacuum evaporates slightly, and the evaporated powder is released. However, the emitted evaporation powder is shielded by the infrared transmitting plate 6 and does not go to the surface of the insulator 5, and therefore the insulation of the insulator 5 does not deteriorate due to the adhesion of the evaporation powder.

In the above embodiment, the infrared heater 7 wound in a circumferential shape is taken as an example, but the present invention is not limited to this. For example, as shown in FIG. 3, a plurality of infrared heaters are provided. 11 may be arranged in the surrounding space of the insulator 5. Further, as shown in FIG. 5, a plurality of infrared heaters 7 may be arranged along the longitudinal direction of the insulator 5. In this case, it is not necessary to form a parabolic recess on the inner peripheral surface of the reflecting mirror 8, and a vertical surface as shown in the drawing may be used.

[0016]

As is apparent from the above description, according to the rotary cathode X-ray tube of the present invention, the heater is installed in the space around the insulator supporting the fixed anode to heat the surface of the insulator. Therefore, the baking can be performed quickly and uniformly. Further, since the infrared ray transmitting plate is arranged between the heater and the insulator, even if the heater heated in vacuum during baking evaporates the evaporated powder on the surface of the insulator. However, the creeping discharge of the insulator due to the evaporated powder is prevented. Further, since the device (heater or the like) required for baking is arranged inside the vacuum container, baking can be performed at any time when the vacuum is broken for some reason, which is practically effective.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view of a rotary cathode X-ray tube according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a transverse sectional view of an insulator portion showing a modified example.

FIG. 4 is a vertical cross-sectional view of an insulator portion for explaining infrared emission.

FIG. 5 is a vertical sectional view of an insulator portion showing a modified example.

FIG. 6 is a vertical cross-sectional view of a conventional rotating cathode X-ray tube.

FIG. 7 is a cross-sectional view of a general medical X-ray tube.

[Explanation of symbols]

 1 ... Vacuum container 3 ... Rotating cathode 4 ... Fixed anode 5 ... Insulator 6 ... Infrared transmitting plate 7 ... Infrared heater

Claims (1)

[Claims] 1. A circular fixed anode supported by an insulator inside an annular vacuum container surrounding the subject, and a filament emitting thermoelectrons for X-ray generation toward the fixed anode. In a rotating cathode X-ray tube having a rotating cathode provided with a heater, a heater is installed in a space around the insulator, and an annular infrared transmitting plate is installed between the heater and the insulator. Rotating cathode X-ray tube.