JPS63193443A - Rotary anode x-ray generating device - Google Patents

Abstract

PURPOSE:To obtain an X-ray generating device with clearance sealing which is small in length and excellent by using a pair of radial magnetic bearings and forming clearance sealing over the approximately whole length of an anode rotary axis. CONSTITUTION:Two positions of an anode rotary axis 18 are supported by radial magnetic bearings which are composed of radial bearing stators 21 and radial bearing rotors 20. A space, which is surrounded with the surfaces of these radial bearings, an axial surface of the anode rotary axis 18 formed between the radial bearings, and a housing 19, is exhausted through an exhaustion path 23 which is linked with a vacuum pump so as to form clearance sealing. Since magnetic bearings are used as bearings in this structure and the same operations of these magnetic bearings are obtained irrespective of ambient pressures, that is, under either atmospheric pressure or vacuum, excellent bearings are available. Further, since exhaustion is performed over the whole length of the magnetic bearings, better clearance sealing can be obtained.

Description

[Detailed Description of the Invention] [Summary] In a rotating anode X-ray generator, an anode rotating shaft is supported by a pair of radial magnetic bearings and a thrust magnetic bearing, and the gap between these bearing surfaces and the anode rotating shaft is used to Consists of clearance seals.

[Industrial application field]

The present invention relates to a rotating anode X-ray generator, and in particular to improvements to its bearing and vacuum seal. Rotating anode X-ray generators used in X-ray lithography and the like need to operate at high speeds as output increases to improve throughput. For this reason, non-contact type bearings and vacuum seals are used, and the present invention relates to improvements in such bearings and vacuum seals.

[Conventional technology]

Conventionally, an apparatus shown in FIG. 4 has been used, in which 31 is a rotating anode, 32 is an electron gun, 33 is an electron beam (EB), and 34 is a rotary anode.
35 is an X-ray extraction window made of Be foil, 36 is a target chamber, 37 is an anode rotation shaft for the rotating anode 31,
38 is a thrust plate, and 39 is a casing.

The rotating anode 31 is rotated at a high speed of about 10,000 RPM by a motor (not shown) connected to an anode rotating shaft 37. The reason is that the metal on the surface of the rotating anode 310 is irradiated with EB,
X-rays are emitted from the metal, and more than 99% of the energy of EB is converted into heat, so the purpose is to disperse that heat. The rotating anode is 10-6 to 10-”T
The target chamber 36 is placed within a target chamber 36 maintained at a degree of vacuum of about 1.5 to 100 m of vacuum.

A radial air bearing 40 is used to maintain the center position of the anode rotating shaft 37 within the casing 39 and enable the above-described high speed rotation, and a radial air bearing 40 is used.
Air at a pressure of approximately g/cm2 is sent to maintain the anode rotating shaft 37 within the air film, and the air is exhausted from the exhaust path 42.

Although the distance between the anode rotating shaft 37 and the casing 39 is suppressed to 10 μm or less, air from the air supply path 41 still enters the target chamber 35 having the above-mentioned degree of vacuum, so a pump (not shown) is used to suppress this. Exhaust passage 42 using
Exhaust from. This portion is called a clearance seal 44.

Furthermore, in order to prevent the anode rotating shaft 37 from shifting in the axial direction, a thrust plate 38 is provided around the shaft 37,
Air is sent through an air supply path 45 and exhausted through an exhaust path 46.

This part is called a thrust air bearing 47.

In the figure, 48 is an exhaust path.

[Problem that the invention seeks to solve]

In the radial air bearing 41, the anode rotating shaft 37
To ensure the resilience of the
A length of mm is required.

In order to suppress air leakage into the target chamber 36, the clearance seal 44 requires a certain length in the axial direction while minimizing the gap between the anode rotating shaft and the casing. 50m
The length should be about m.

In the thrust air bearing 47, the thrust plate 38
If it is made too thin, it will deform, so it must have a certain degree of thickness, and requires a total length of 80 to 100 mm.

For the above reasons, in the conventional device, the clearance seal 44, the radial air bearing 41, and the thrust air bearing 47 are simply arranged in series, resulting in the problem that the overall length of the device is too long.

The present invention was created in view of these points, and an object of the present invention is to provide a compact rotating positive iX-ray generator.

[Means for solving problems]

FIG. 1 is a diagram of the first embodiment of the present invention, in which 11 is a rotating anode, 12 is an electron gun, 13 is an electron beam (EB), 14 is an X-ray extraction window, 15 is an X-ray, and 16 is not shown. a target chamber which is evacuated by a vacuum pump, 17 is an exhaust path, 18
is an anode rotating shaft, 19 is a housing, 20 is a radial bearing rotor, 21 is a radial bearing stator, 22 is a radial sensor, 23 is an exhaust path, 24 is a thrust bearing rotor,
25 is a thrust bearing stator, and 26 is a thrust sensor.

In the first embodiment of the present invention, two locations on the anode rotating shaft 18 are the radial bearing stator 21 and the radial bearing rotor 2.
0, and the radial magnetic bearing surface and between the shaft surface of the anode rotating wheel 18 and the housing 19 are evacuated through an exhaust passage 23 connected to a vacuum pump (not shown) to seal a clearance. That is.

(Function) In the above configuration, a magnetic bearing is used as a bearing,
This magnetic bearing can operate in the same way regardless of the surrounding pressure, i.e. at atmospheric pressure or in a vacuum, thus providing a good bearing, and because it is evacuated over the entire length of the magnetic bearing, it provides better clearance than conventional examples. You will get a seal.

C Embodiment] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Returning to FIG. 1 again, in the first embodiment of the present invention, the mechanism for extracting the X-rays 15 and the arrangement of the rotating anode 11 within the target chamber 16 are the same as in the conventional example.

The anode rotating shaft 18 has a radial magnetic bearing consisting of a pair of radial bearing rotor 20 and radial bearing stator 21,
Thrust bearing rotor 24 and thrust bearing stator 25
A pair of radial magnetic bearings are supported in a non-contact manner by one thrust magnetic bearing consisting of a
0 mm) apart.

An annular groove 2 is formed in the portion between the magnetic bearings of the housing 19.
3a is formed and this? 1423a is exhausted through an exhaust path 23 connected to a vacuum pump (not shown).

FIG. 2 is a sectional view taken along the line nn in FIG. 1, and the anode rotation axis is centered by the magnetic field created by the radial bearing stator (magnet) 21. In order to achieve accurate centering, a radial sensor 22 is arranged as shown in FIG. 1 to magnetically detect the position of the shaft, and the value of the current flowing through the magnet is controlled according to the result of this detection. Ensures that the anode rotation axis remains in a constant position.

The gap between the anode rotating shaft 18 and the housing 19 is 10μ.
m, and a gap extending over the entire length of the anode rotating shaft 18 from the atmosphere side opening (not shown on the right side in the figure) to the target chamber 16 is evacuated through an exhaust path 23 connected to a vacuum pump (not shown). Acts as a clearance seal. The length of this clearance seal is much greater than that of conventional clearance seals, and since the clearance seal increases its effectiveness with length, the amount of air leaking into the target chamber 16 is significantly reduced.

In the embodiment shown in FIG. 1, a thrust magnetic bearing consisting of a thrust bearing rotor 24 and a thrust bearing stator 25 is used, and a thrust sensor 26 is used to control the position of the thrust bearing rotor 24.

FIG. 3 is a diagram of a second embodiment of the present invention, in which a thrust magnetic bearing is provided between a pair of radial magnetic bearings. This embodiment has the advantage of being smaller in length than the embodiment shown in FIG. 1, and the exhaust passage 23 is connected to a vacuum pump (not shown) for exhaustion in order to provide a sufficient clearance seal.

〔Effect of the invention〕

As described above, according to the present invention, by using a pair of radial magnetic bearings and configuring a clearance seal over almost the entire length of the anode rotating shaft, although the length is smaller than that of the conventional example, a sufficient clearance can be achieved. X with a sticker
A line generator is obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the first embodiment of the present invention, Figure 2 is a sectional view taken along line nn in Figure 1; FIG. 3 is a diagram of the second embodiment of the present invention, FIG. 4 is a diagram of a conventional example. In Figures 1 to 3, 11 is a rotating anode; 12 is an electron gun, 13 is EB. 14 is an X-ray extraction window; 15 is X-ray, 16 is the target room, 17 is the exhaust path, 18 is the anode rotating shaft; 19 is the housing, 20 is a radial bearing rotor, 21 is a radial bearing stator, 22 is a radial sensor, 23 is the exhaust path, 23a is a groove; 24 is a thrust bearing rotor; 25 is a thrust bearing stator; 26 is a thrust sensor.

Claims (2)

[Claims] (1) A rotating anode (
In an X-ray generator that extracts X-rays (15) by irradiating an electron beam (13) onto an object (11), the anode rotating shaft is connected to a radial bearing rotor (
20) and a radial bearing stator (21), the gap between the radial magnetic bearing surface and the surface of the anode rotating shaft (18) therebetween and the housing (19) is evacuated to form a clearance seal. A rotating anode X-ray generator characterized by: (2) The apparatus according to claim 1, wherein a thrust magnetic bearing consisting of a thrust bearing rotor (24) and a thrust bearing stator (25) is arranged between the radial magnetic bearings.