JPS5941269B2 - rotating anode x-ray tube - Google Patents

Abstract

PURPOSE:To reduce the abrasion of the contact of an anode terminal and the frictional resistance, by completely floating a rotary anode magnetically while flowing the anode current to a contactless current path. CONSTITUTION:A rotary anode 12 is arranged in an insulator vacuum container 1. An umbrella-shaped target 13, a shaft 14 extended to both sides, a rotor 15 fixed to said shaft 14, permanent magnets 16, 17 for supporting in radial direction and permanent magnets 18, 19 for supporting in the thrust direction are secured to the rotary anode 12. A cathode structure 20 is provided to a portion of the vacuum container 11 while facing with the target 13. A stator coil 22 is provided at the outside of the container 11 while permanent magnets 16a, 17a and electromagnets 16b, 17b are arranged in correspondence with the radial supporting magnets 16, 17. While permanent magnets 18a, 19a and electromagnets 18b, 19b are arranged in correspondence with the thrust supporting magnets 18, 19.

Description

[Detailed description of the invention] The present invention relates to a magnetically levitated rotating anode X-ray tube.

An X-ray tube having a structure in which a rotating anode is magnetically supported so as to be rotatable at high speed in place of the conventional ball bearing has been proposed and is known. All of the previously proposed structures have a structure in which the rotating anode is in direct point contact with the anode terminal that penetrates the vacuum vessel in order to conduct the anode current, and therefore are magnetic support structures suitable for ultra-high speed rotation. However, there is a disadvantage that the intended purpose cannot be fully satisfied due to wear and frictional resistance at the contact point of the anode terminal. The present invention solves these inconveniences by providing a magnetically levitated rotating anode X-ray tube in which the rotating anode is completely levitated by magnetism and the anode current can flow through a non-contact current path. .

Examples thereof will be described below with reference to the drawings. Identical parts are designated by the same reference numerals. The embodiment shown in FIG.
is formed with a large diameter at the center and small diameters at both ends, and a rotating anode 12 is disposed inside the anode.

Note that a part of the vacuum container may be made of metal. Rotating anode 1
2 is an umbrella-shaped target, a target 13, a shaft 14 extending on both sides, a rotor 15 fixed to this shaft, a permanent magnet 16 for radial direction support, an IT, and permanent magnets 18 and 19 for thrust direction support are fixed respectively. ing. on the other hand,
A cathode assembly 20 is provided in a part of the vacuum container 11 so as to face the target 13, and a position detector 21 for detecting the position of the target 13 is also provided. On the other hand,
A stator coil 22 for rotating the rotor is provided outside the container 11, and a radial support magnet 16 is provided.
, 17, permanent magnets 16a, 1Ta,
Electromagnets 16b and 17b are arranged so that their N and S poles are located in the radial direction, as shown in the figure. Also, a permanent magnet 18a corresponds to the thrust support magnets 18 and 19.
, 19a) Electromagnets 18b and 19b are each axially N
, S poles are located. These electromagnets are used to finely correct the position of the rotating anode 12 by a controller (not shown) so as to be controlled by a position display signal from the target position detector 21. Of course, it also functions to appropriately compensate for the demagnetization of each permanent magnet. Now, on one end surface of the rotating anode 12, a bottomed cylindrical support 24 having an electron emitting layer 23 coated on its inner surface is electrically and mechanically connected and fixed to the shaft.

The electron emitter layer 23 is a hot cathode, such as an oxide cathode, in this embodiment. A heating filament 25 made of tungsten is disposed close to and opposite to this, and this filament 25 is an electron current collecting electrode connected and fixed to a lead wire 26 penetrating the vacuum vessel 11. This lead wire 26 is an electrode for applying a voltage to the anode of this X-ray tube and for passing an anode current. Such an X-ray tube of the present invention is
The rotating anode is completely magnetically levitated and rotated relative to the vacuum vessel and the fixed member.

Then, the heating filament 25 is heated with heating power supplied from a power source outside the container. As a result, the electron emitter layer 23 in the vicinity of this filament is also heated by the radiant heat from the filament, and becomes capable of emitting thermoelectrons. Of course, the cathode assembly 20 provided opposite the target 13 is also heated. When a high positive voltage (for example, 150 k) is applied to the lead electrode 26 of the cathode structure 20 in this state, there is a slight voltage drop between the rotating anode and the filament 25 due to thermionic electrons generated from the electron emitting layer 23. It becomes almost a short-circuit state, and it is generated from the cathode structure 20 and reaches the target 13.
The anode current path is completed by the electron flow incident on the anode. That is, the anode current reaches the cathode structure 20 from the lead electrode 26 via the collection electrode filament 25, the electron emitter layer 23, the shaft 14, and the target 13. This allows the rotating anode to operate completely non-contact and suspended from a fixed member such as a vacuum vessel, allowing it to maintain a long-life, high-capacity X-ray tube without wearing out even when rotating at ultra-high speeds of over 10,000 revolutions per minute. realizable.

Although a thermionic emitter was used as the electron emitter layer in the above embodiment, a cold cathode material such as MgO may be used instead. A filament for starting the cold cathode and an electron flow collecting electrode may be provided in the vacuum container so as to face the cold cathode.

In the embodiment shown in FIG. 2, a disk-shaped support 2 made of a material whose temperature is raised by high-frequency induction heating is attached to the shaft end of a rotating anode 12.
7 is fixed, and an electron emitter layer 23 is applied to the end face thereof.

Further, a collection electrode 25 is provided close to and opposite to this.
A high frequency induction coil 28 of several hundred KHz is provided outside the container, and the electron emitting material layer is heated by induction heating from the outside. In the embodiment shown in FIG. 3, a photoelectron emitter layer 23 such as PbO is provided on the shaft, and the photoelectron emitter layer 23 is excited by a light projector 29 from outside the container to emit electrons.

As described above, in the rotating anode X-ray tube of the present invention, an electron emitting material layer is provided on a part of the rotating anode, and an electron current collecting electrode that closely opposes this layer and forms an anode current path is fixed in a vacuum container. Since it is a non-contact type, and the anode is magnetically levitated, stable ultra-high speed rotation is possible.

Note that the electron emitting material layer provided on the anode is not limited to the shape shown above, but may have a double or more polymerized cylindrical shape, etc., in order to obtain a sufficient electron emitting area so that a current of 1000 mA or less can be extracted. , it can be made into a shape with multiple faces facing each other.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing one embodiment of the present invention, and FIGS. 2 and 3 are longitudinal cross-sectional views of essential parts showing other embodiments. 11... Vacuum vessel, 12... Rotating anode, 13...
Target, 16-19...Magnet for magnetic levitation, 23
...electron emitter layer, 25...electron flow collecting electrode.

Claims (1)

[Scope of Claims] 1. A rotating anode X-ray tube configured such that a rotating anode disposed within a vacuum vessel is magnetically levitated,
An electron emitter layer is formed on a part of the rotating anode, and an electron flow collection electrode connected to an anode voltage applying electrode is disposed close to and opposite to the electron emitter layer. Anode X-ray tube. 2. The X-ray tube according to claim 1, wherein the electron emitting material layer is made of a thermionic emitting material, and the material is heated by heating power applied from the outside.