JP2001276048A - Cathode scanning type x-ray generator and x-ray ct scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a very high-speed CT scanner reducing the scanning time of an X-ray CT scanner and a cathode scanning type X-ray generator for realizing the above scanner. SOLUTION: The very high-speed CT scanner and the cathode scanning type X-ray generator for realizing the above scanner have a cathode-side rotator assembly CR, at least one electronic gun assembly EG, a cathode for discharging thermoelectron, and an annular cathode power supply mechanism SL1 in a doughnut-shaped vacuum vessel VV, and makes a cathode orbit around an examinee body while supplying the power to the cathode, to make an accelerated electronic beam incident on the surface of an annular X-ray target TG to generate X-rays orbiting at high speed. The cathode-side rotator assembly is freely rotatably supported by a bearing mechanism consisting of a hidrodynamic slide bearing lubricated by metal liquid lubricant. There is an annular low- pressure cavity between the hidrodynamic slide bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode scan type X-ray generator for an X-ray CT scanner which is small in size and emits X-rays from an X-ray orbiting at a high speed and can perform ultra-high-speed scanning. And an X-ray CT scanner capable of performing ultra-high-speed scanning using the same. By limiting the rotating part for orbiting the X-ray focus to small parts in the vacuum vessel, the X-ray focus can be stabilized around the specimen at high speed without a mechanical rotation mechanism in the atmosphere. Provided is a small-sized X-ray CT scanner capable of obtaining a three-dimensional image by instantaneously photographing a subject by orbiting the subject. A dynamic pressure sliding bearing using a liquid metal as a lubricant is used to rotate the electron gun assembly in the vacuum vessel, and the components circulating in the vacuum vessel are energized from outside the vacuum vessel.

[0002]

2. Description of the Related Art A conventional X-ray CT scanner will be described with reference to FIG. Conventional X
The line CT scanner includes a fixed base 1001 and a bearing 1003.
And a rotating gantry 1002 that rotates through the. The rotating gantry 1002 is rotated in the air by a rotation driving mechanism 1009 controlled using a controller 1008. An X-ray tube 1004 for generating X-rays, a high-voltage power supply (not shown) for supplying a high voltage thereto, a detector 1006 for receiving X-rays, and other electronic circuits 10
07 and the like are attached to the rotating frame 1002. A signal of an electronic circuit attached to the rotating gantry 1002 is transmitted to the fixed gantry 1001 by a slip ring (not shown). For this reason, the sum of the masses of the components attached to the rotary gantry 1002 increases, and if the scanning speed of the X-ray CT scanner is increased, a large centrifugal force acts, and the components mounted on the rotary gantry 1002 and the rotary gantry 100
2 has a drawback that the scanning speed cannot be increased because it cannot withstand excessive stress.

[0003] X-rays used in conventional X-ray CT scanners
The wire tube 1004 is a disk-shaped X-ray target having a diameter of about 10 cm and 3,000 rpm in a cylindrical vacuum vessel.
The X-ray is rotated at a high speed of about m, and collides with electrons emitted from the cathode of the electron gun assembly to emit X-rays 1005 in one direction. The entire structure is cylindrical.
An X-ray tube for an X-ray CT scanner, which needs to generate a large amount of X-rays, requires a cooler, and the sum of both masses is 1
The rotation frame 1002 for attaching and rotating it in the air becomes large, and the entire X-ray CT scanner becomes large, which is not only inconvenient to handle, but also requires a large installation space. And the operating costs were large. Further, in recent years, as the use of X-ray CT scanners has expanded, there has been a demand for instantaneous observation of blood and a contrast agent. In order to respond to this, it is necessary to rotate the X-ray tube 1004 around the subject at a high speed. The highest orbiting speed so far is 2r
ps, which is considered the limit. on the one hand,
There is a demand to increase the X-ray dose to enhance the image quality and enhance the diagnostic performance, and it is necessary to increase the size and mass of the conventional X-ray tube 1004. Simultaneously satisfying these conflicting requirements has been impossible with an X-ray CT scanner having a conventional structure.

On the other hand, an X-ray CT scanner of the electronic scan type has been developed in the past in order to increase the scanning speed. This is done by taking out electrons from an electron gun assembly fixed at the bottom of a vacuum vessel in the shape of a thermos bottle placed on its side, and electromagnetically controlling the position of the electrons while traveling about 100 cm in the vacuum vessel. After orbiting around the subject, the electrons are made incident on an arc-shaped X-ray target to extract an X-ray that makes a half circle. With this structure, high-speed scanning with a scan time of about 0.1 second is possible,
Poor image quality due to insufficient X-ray dose, too large X-ray focus, difficulty in maintaining stable operation, and difficulty in handling because the entire device is large They have disadvantages such as high cost and are used only for special purposes.

[0005]

The problem to be solved is that the scan time of the X-ray CT scanner is greatly reduced to eliminate motion artifacts and to provide a sufficient level of X-ray dose in imaging a fast moving subject. An object of the present invention is to provide an X-ray CT scanner which can obtain a high-quality image with less photon noise by securing the X-ray CT scanner, and which is small in size and easy to handle. In particular, to achieve this, a bearing mechanism that can be used reliably in a vacuum, and a power supply mechanism that can supply power to components rotating in a vacuum. In spite of the fact that this bearing has a large diameter and a large height drop at the bearing opening, not only does the liquid metal lubricant not leak out of the bearing mechanism, An object of the present invention is to provide a cathode scan type X-ray generator in which a liquid metal lubricant does not move to the outside of a bearing mechanism even when an extremely high pressure is generated, and an X-ray CT scanner using the same.

[0006]

SUMMARY OF THE INVENTION In the present invention, all rotating parts of an X-ray CT scanner are mounted in a donut-shaped vacuum vessel so as to be reduced to a minimum, eliminating the need for mechanical rotating parts in air. By doing so, an X-ray CT scanner capable of ultra-high-speed scanning is realized. The vacuum container is formed in a donut shape, and the subject is placed on a bed in the atmosphere near the central axis of the vacuum container. Electrons are emitted from the cathode of the electron gun assembly that circulates in the vacuum vessel, and accelerated electrons collide with the annular X-ray target mounted in the vacuum vessel in opposition to the orbit of the cathode to generate X-rays. generate. The generated X-ray passes through an X-ray emission window provided on the small-diameter wall of the vacuum vessel, and is applied to the subject in the atmosphere.
X-rays that have passed through the subject are detected by an annular X-ray detector mounted in the air coaxially with the vacuum container, reconstructed into a tomographic image by a computer, and displayed on a display device. The rotating part for rotating the X-ray focal point in the vacuum vessel is limited to a lightweight electron gun assembly, etc., and its volume is small, and it is almost symmetrical as a whole. Even when rotating, the stress applied to the rotating body can be sufficiently reduced, and stable high-speed rotation can be continued. Also, since about three electron gun assemblies are mounted on the same cathode side rotating body assembly, the scan time is 0.0%.
An ultra-high-speed scan of about 3 seconds can be performed.

An X-ray CT scanner of the type in which an electron gun is rotated inside a donut-shaped vacuum vessel has been proposed in the past, but has not been realized so far. One of the reasons is that a means for continuing stable rotation in a vacuum and a reliable means for stably setting the potential of the rotating body to a constant value have not been found. In the present invention, as a bearing mechanism that can be used reliably in a vacuum, an annular dynamic pressure sliding bearing using a liquid metal that is a liquid during operation as a lubricant is adopted,
This provides a means for preventing the liquid metal lubricant from leaking out of the bearing mechanism despite the fact that the diameter of the bearing is large and the height drop of the opening of the bearing is large. Further, the potential of the rotating body is set to a constant value via the liquid metal lubricant.

When the bearing rotating body constituting the rotating part of the bearing mechanism is rotating, the liquid metal lubricant is confined inside by the suction action of the bearing groove provided on the surface of the bearing. Generally, when the bearing rotating body stops rotating, leakage of the liquid metal lubricant is prevented by the surface tension of the liquid metal lubricant generated in the opening at the end of the bearing. However, in the X-ray CT scanner of the present invention, the center of rotation of the bearing rotating body is substantially horizontal, and the diameter of the bearing is approximately 10 mm.
Since the height is as large as 0 cm, the height difference in the bearing gap is large, and the liquid metal lubricant in the portion located vertically below the bearing gap receives a large static pressure due to the gravitational acceleration. In the opening of the bearing, the size of the bearing gap vertically below is extremely small so that the pressure effect of the surface tension generated in the liquid metal lubricant overcomes this static pressure. As one of the means to achieve this,
Limit the bearings adjacent to the bearing opening to thrust bearings,
The size of the bearing gap in this area is kept small.
Due to this effect, the pressure effect of the surface tension in the vertical downward direction becomes larger than the static pressure of the liquid metal lubricant, and the leakage of the liquid metal lubricant to the outside is prevented, and stable operation is guaranteed. However, it is necessary to prevent the liquid metal lubricant from moving to the outside of the bearing mechanism even when a problem such as expansion of residual gas occurs inside the bearing mechanism.

According to the present invention, the angle of the surface located outside the opening of the bearing is increased, so that even if the liquid metal lubricant swells outward due to an increase in the pressure inside the bearing, this portion is surrounded by the surroundings. As the pressure returns to normal, the liquid metal lubricant returns to the inside of the bearing. In addition, a ring-shaped depression having a large volume and a low pressure is provided between the bearings. Even when gas is generated in the bearing, the pressure is reduced by the low-pressure depression near the bearing, and the liquid metal lubricant is removed. The effect of pushing the bearing out of the bearing does not occur. Further, the low-pressure depression communicates with the vacuum space so that the low-pressure depression is always kept at a low pressure. Therefore, the cathode scan type X-ray generator of the present invention can continue stable operation for a long period of time without the liquid metal lubricant leaking out of the bearing even if an abnormal pressure change occurs in the bearing. .

According to the present invention, the bearing surface is in thermal communication with the vacuum vessel, and the vacuum vessel is forcibly cooled from the outside. , The thermal expansion is small, and stable operation can be continued for a long time. Further, components that generate heat, such as an electron gun assembly and an X-ray target, are also forcibly cooled via the liquid metal lubricant present in the bearing gap, thereby suppressing thermal expansion and the like.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A cathode scan type X-ray generator is wrapped in a donut-shaped vacuum vessel, and the vacuum vessel is installed so that its central axis is substantially horizontal. A subject (human body) is placed in the atmosphere, and the vacuum container is arranged so as to surround the subject. The vacuum container is fixed without rotating, and the angle with the subject and the position in the horizontal direction can be changed. X-rays are generated toward the subject while moving the X-ray focus so that the X-ray focal point orbits around the subject inside the vacuum vessel. The use of the orbiting X-ray realizes an X-ray CT scanner having no rotating mechanism in the atmosphere. Cathode scan type X for X-ray CT scanner that can perform ultra-high-speed scanning and obtain large output, which was impossible with an X-ray CT scanner having a conventional structure
A ray generator and an ultra-high-speed X-ray CT scanner using the same have been realized with a simple structure at low cost and with high reliability.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a cathode scan type X-ray generator according to one embodiment of the present invention and an X-ray CT scanner using the same will be described below with reference to the drawings. FIG. 2 shows a cathode scan type X-ray generator of the present invention and an X-ray using the same.
FIG. 3 is a schematic cross-sectional view of the entire structure of the X-ray CT scanner, FIG. 3 is a principle view, and FIG. 4 is a cross-sectional view of a part of a cathode scan type X-ray generator according to the present invention which is located vertically above at a certain moment. Is an enlarged view of a part of a cross section around the electron gun assembly in a state of being located vertically above at a certain moment. The same parts have the same symbols.
FIG. 5 is an enlarged sectional view of a main part of the cathode scan type X-ray generator of the present invention, FIG. 6 is an enlarged sectional view of a lower part of FIG. 5, and FIG. It is a part of the enlarged sectional view showing.

As shown in FIG. 2, the donut-shaped vacuum vessel VV is installed so that its central axis is substantially horizontal, and is constantly evacuated to a high vacuum state from an exhaust port VC by a vacuum pump (not shown). As shown in FIG. 2 or FIG.
A cylindrical cathode-side rotating body assembly CR is provided in a vacuum space inside the vacuum vessel VV. The cathode-side rotating body assembly CR is a bearing mechanism CBG comprising a dynamic pressure sliding bearing using a liquid metal which is a liquid at room temperature as a lubricant. , Which are rotatably supported in a vacuum, and their central axes coincide with CC ′. Three electron gun assemblies EG are attached to the cathode side rotating body assembly CR separately in the circumferential direction. As shown in FIG. 2 or FIG. 4, a cylindrical rotor RT2 made of copper is provided on the cathode side rotating body assembly CR.
Are mounted coaxially, and a magnetic path cylinder made of a magnetic material is mounted coaxially with the shaft. Rotor RT2
An arc-shaped stator LM2 is attached to the outside of the vacuum vessel VV along the vacuum vessel wall in a state facing the vacuum vessel VV. The rotor RT2 includes the magnetic path cylinder and the stator L.
It is arranged in a state sandwiched by M2. The rotor RT2 receives a rotational torque from the stator LM2 through the wall made of the non-magnetic material of the vacuum vessel VV and receives a rotational torque, so that the cathode side rotating body assembly CR rotates. The cathode side rotating body assembly CR electrically and thermally passes through the vacuum vessel V through a liquid metal lubricant in a bearing mechanism CBG including a dynamic pressure sliding bearing.
Connected to V.

As shown in FIG. 4, a cathode 1 for emitting thermoelectrons 2 is attached to the tip of the electron gun assembly EG. An annular X-ray target TG is attached to face the orbit of the cathode 1. As shown in FIG. 2, the X-ray target TG is a cylindrical anode-side rotating body assembly A.
It is mechanically coupled to R. The anode side rotating body assembly AR is rotatably attached to a part of the vacuum vessel VV via a bearing mechanism ABG including a dynamic pressure sliding bearing using liquid metal which is liquid at room temperature as a lubricant. Anode rotating body assembly AR
Is equipped with a rotor RT1 made of a copper tube.
A magnetic path cylinder made of a magnetic material is mounted coaxially with the magnetic path cylinder. An arc-shaped stator LM1 is attached along the vacuum vessel wall outside the vacuum vessel in a state facing the rotor RT1. The rotor RT1 is disposed between the magnetic path cylinder and the stator LM1. The rotor RT1 is given a rotating torque by receiving electromagnetic induction from the stator LM1 through a wall made of a non-magnetic material of the vacuum vessel VV, so that the anode side rotating body assembly AR rotates. The center axis of rotation of the X-ray target TG and the center axis CC 'of rotation of the cathode 1 of the electron gun assembly EG.
In the state where the cathode 1 always faces the surface of the X-ray target TG, the two rotate in opposite directions.

Referring to FIG. 2 or FIG. 4, cathode feeding mechanism SL
1 will be described. In the embodiment shown in FIG. 2 or FIG.
The two cathode power supply mechanisms SL1 are coaxially mounted, and form three independent current paths. In these figures, the internal structure of the cathode power supply mechanism SL1 is simplified. The cathode 1 of the electron gun assembly EG is electrically connected to the high voltage terminal HT through an annular cathode feeding mechanism SL1 having a center axis substantially the same as the circulating center axis CC ′ of the electron gun assembly EG in the vacuum vessel VV. ing. High voltage terminal HT
Is supplied with a negative high voltage of about -150 KV and power for heating the cathode 1 of the electron gun assembly EG from a high voltage power supply (not shown) provided outside the vacuum vessel VV. Each cathode power supply mechanism SL1 has a fixed portion and a rotating portion, and the fixed portion is mechanically fixed to a part of the vacuum vessel VV via an insulator 220 while maintaining electrical insulation. The rotating part and the fixed part of the cathode power supply mechanism SL1 constitute a dynamic pressure sliding bearing using liquid metal as a lubricant, and electricity is supplied between the two via the liquid metal lubricant. The rotating part of the cathode power supply mechanism SL1 is an electron gun assembly EG
The cathode power feeding mechanism SL1 rotates together with the electron gun assembly EG while allowing a certain degree of eccentricity and axial displacement.

The X-ray target TG is an anode side rotating body assembly A
It is electrically and thermally connected to the vacuum vessel VV via the liquid metal lubricant present in the R bearing mechanism ABG. The vacuum vessel VV is at the ground potential and is forcibly cooled with cooling water or the like. Therefore, the X-ray target TG is set to the ground potential, and a large amount of heat generated from the X-ray target TG is efficiently removed by the cooling water flowing through the wall of the vacuum vessel VV via the liquid metal lubricant. Since the thermal resistance between the X-ray target TG and the cooling water is sufficiently small,
Since the temperature of the line target TG is kept low, a large input is allowed and an extremely large amount of X-rays can be generated in a short time.

The electron gun assembly EG includes F1 and F shown in FIG.
As shown in F2 and F3, three are mounted at equal intervals around the cathode side rotating body assembly CR. Here, F1, F2, and F3 indicate three focal points of X-rays that are generated when the electrons 2 are accelerated and collide with the X-ray target TG. X-ray focus F
1, F2 and F3 simultaneously rotate in the same direction as shown in FIG. 3 while simultaneously generating X-rays. The current positions of these X-ray focal points are detected by an angle detection mechanism (not shown) attached to the cathode side rotating body assembly CR. The X-rays emitted from the X-ray focal points F1, F2, F3 are shown in FIG.
As shown in the figure, the fan is shaped like a fan by the X-ray distribution limiting mechanism inside the X-ray target TG, and after passing through the fan direction distribution shaper WF (see FIG. 4) attached to the cathode side rotating body assembly CR, the vacuum X-ray emission window XW of container VV
(See FIG. 4), and after passing through the external annular slit SLT, pass through the subject M and pass through the X-ray target TG.
Annular X-ray detectors D mounted coaxially with
F and DB are reached.

As shown in FIG. 3, X-ray focal points F1, F2,
The X-rays emanating from F3 are received by the subdivided detection elements, each of which is in the opposite part D1, D2, D3 of the detector. The irradiation field range and the like are determined so that the detector portions D1, D2, and D3 do not overlap each other. Since the sum of the detector portions D1, D2, and D3 occupies almost the entire annular detector, all the detection elements in the X-ray detectors DF and DB are effectively used, and the cost / performance ratio is improved. Each of the annular detectors DF and DB is also divided into a large number of detection element rows in the direction of the central axis CC ′, and a signal detected by each detection element is converted into a digital signal by an electronic circuit (not shown). The image is reconstructed into a tomographic image by a computer (not shown) and displayed on an image display device (not shown) to obtain a multi-slice CT image.

FIG. 4 is an enlarged view of a part of the cross section around the electron gun assembly at a moment when it is positioned vertically above, and the same parts are denoted by the same symbols. The cathode-side rotating body assembly CR has a generally rotationally symmetrical structure as a whole, and the components such as the electron gun assembly EG attached thereto are small and lightweight, so that they can sufficiently withstand high-speed rotation of about 10 rps. In this case, since there are three X-ray focal points, the scan time can be reduced to 0.03 seconds. The X-ray target TG has a large diameter of 120 cm, rotates in the direction opposite to the X-ray focal points F1, F2, and F3, and is forcibly cooled as described above, so that the surface temperature of the X-ray target TG increases. Since it is difficult to input a large amount of power, a sufficient amount of X-rays can be generated in a short time, and a high-quality CT image with little photon noise can be obtained despite ultra-high-speed scanning. In addition, since the multi-slice scan is realized, X-rays can be effectively used, not only can the resolution in the direction parallel to the central axis CC 'be increased, but also a wide range of imaging can be completed in a short time to achieve three-dimensional scanning. Real-time CT image can be obtained.

In order to realize the X-ray CT scanner having the above configuration, it is inevitable that the bearing mechanisms CBG and ABG comprising dynamic pressure sliding bearings which can be practically used in the above-described device configuration and the cathode power supply mechanism SL1 be used. An object of the present invention is to realize a hydrodynamic sliding bearing that rotatably supports a rotating part. Conventionally, dynamic pressure sliding bearings having a diameter of 5 cm or less and having an opening on only one side have been put to practical use. In this case, the liquid metal lubricant inserted into the dynamic pressure sliding bearing is retained inside the bearing opening by the action of surface tension at the bearing opening. In order to obtain a sufficient bearing pressure of the hydrodynamic sliding bearing, the size of the gap between the rotating part and the fixed part has been limited to several tens of μm. For example, when the size of the gap in the opening of the bearing is 50 μm and the height drop of the liquid metal lubricant exceeds about 18 cm, the static pressure of the liquid metal lubricant due to gravitational acceleration overcomes the surface tension at the opening of the bearing and the liquid Metal lubricant leaks out. This becomes a serious problem when the rotating part of the bearing stops rotating. Particularly, a dynamic pressure sliding bearing having a height drop of about 100 cm in the circumferential direction of the opening of the bearing as in the case of the present invention cannot be realized by the conventional technology.

Referring to FIGS. 5, 6 and 7, a description will be given of a bearing mechanism CBG comprising a dynamic pressure sliding bearing. FIG. 5 is an enlarged view of a part of the cross section of the cathode side rotating body assembly CR and the cathode side bearing mechanism CBG. The upper part of FIG. 5 shows a part that is vertically located at a certain moment in actual use,
The lower part shows the part located vertically below at the same moment. In FIG. 5, the central part is omitted and is shortened and displayed. 6 and 7 are enlarged views of a part located below FIG. 5 and show different embodiments.
A bearing rotating body 102, which is a rotating part of the bearing mechanism CBG, is coaxially attached to the cathode side rotating body assembly CR. A bearing fixed body 101 which is a fixed part of the bearing mechanism CBG is fitted to the bearing rotating body 102 with a gap. A part of the bearing fixing body 101 is mechanically and thermally connected to the vacuum vessel VV. The vacuum vessel VV is attached to a support base (not shown) so that an appropriate posture and a horizontal position with respect to the installation floor can be maintained. The bearing fixed body 101 and the bearing rotating body 102 have surfaces facing each other, and the facing surfaces are the first bearing gaps 103 and 10.
8, the second bearing gap 104,109, the third bearing gap 106,111. At least one of the opposing surfaces forming the bearing gap has a herringbone-shaped bearing groove. In the first, second and third bearing gaps, a liquid metal that is liquid at room temperature, preferably gallium,
Lubricant made of alloy of Injum and bell is filled, each bearing gap is a radial bearing, a first thrust bearing and a second thrust which are mounted facing each other with a distance between them. The bearing gaps constitute the bearings. Bearing gap 1
The reference numerals 03 and 108, the bearing gaps 104 and 109, and the bearing gaps 106 and 111 are the same, and different numbers indicate differences in the indicated positions. Here, it is shown that at least one of the surfaces facing the bearing gap has the bearing groove.

When a rotational torque is applied to the cathode side rotating body assembly CR, a dynamic pressure is generated in these bearings, so that the rotating portion can be floated and rotatably supported. When the bearing rotating body 102 is rotating, the liquid metal lubricant in each bearing gap undergoes an action of confining the inside of the bearing, so that it does not leak from the bearing gap to the outside vacuum space.

As shown in FIGS. 5 and 6, first and second end gaps 105 and 110 and second and end gaps 107 and 112 are formed on opposing surfaces formed by the bearing fixed body 101 and the bearing rotating body 102, respectively. Bearing gap 1 for radial bearings
03, 108 and first end gaps 105, 110,
The central axes of the opposing surfaces constituting the second end gaps 107 and 112 coincide with CC ′ in a state where they are substantially horizontal. Bearing gap 10 of first thrust bearing
4,109, and bearing gap 1 of the second thrust bearing
06,111 are flat, and the bearing gap 104 of the first thrust bearing,
Reference numeral 109 denotes a bearing gap between the radial bearings 103 and 108 and the first end gaps 105 and 110, and bearing gaps 106 and 111 of the second thrust bearing correspond to the bearing gaps 103 and 108 of the radial bearing and the second end gap. 10
7, 112. First end gap 10
The diameter of each of the opposing surfaces forming the second end gaps 107 and 112 is smaller than the diameter of the opposing surfaces forming the bearing gaps 103 and 108 of the radial bearing. The size of the first end gaps 105, 110 and the size of the second end gaps 107, 112 are larger than the size of the bearing gaps 103, 108 of the radial bearing and the first end gaps 105, 110.
And the second end gaps 107, 112 are both in communication with the vacuum space, and have opposing surfaces which are not wetted by the liquid metal lubricant (not shown). Bearing gaps 104, 109 of the first thrust bearing
There are annular bearing openings 121, 121 'between the first end gap 105, 110 and the second end gap 1 with the bearing gaps 106, 111 of the second thrust bearing.
07, 112 between the annular bearing openings 120, 12
There is 0 '. These bearing openings have opposing surfaces that are not wetted by the liquid metal lubricant and a gap sandwiched therebetween. End gaps 105 and 110, end gaps 107 and 112, bearing openings 120 and 120 ',
The bearing openings 121 and 121 'are the same, and different numbers indicate different positions. Here, at least one of the surfaces facing the end gap has the non-wetting surface.

The vertically lower portion will be described with reference to FIG. The description here will be made only for the vertically lower part shown in the figure. The bearing opening 120 and the bearing opening 121, which form a substantial boundary between the region where the liquid metal lubricant is present in the bearing mechanism CBG and the vacuum space, have a surface that is not wet by the liquid metal lubricant. The surface tension acts on the liquid metal lubricant in the portion, and the bearing rotating body 10
Even when the rotation of the motor 2 stops, the liquid metal lubricant is prevented from leaking to the outside. The static pressure in the liquid metal lubricant due to gravitational acceleration is proportional to the depth of the liquid metal lubricant from the waterline. In other words, the static pressure in the liquid metal lubricant becomes higher as it is located vertically downward. On the other hand, the pressure effect of the surface tension that pushes back the liquid metal lubricant is inversely proportional to the size of the gap of the bearing opening. Therefore, if the size of the gap of the bearing opening is made sufficiently small, it is possible to prevent the liquid metal lubricant from leaking from the inside of the dynamic pressure sliding bearing having a large diameter. This can be achieved by forming a bearing opening at the end of the thrust bearing. The reason is that it is difficult to keep the gap size of the radial bearing at a sufficiently small value because the diameter of the bearing used in the present invention is as large as about 100 cm. Is short so that it is hardly affected by thermal expansion.Because it is mounted with a horizontal rotation center axis CC ', it is hardly affected by gravity and centrifugal force. It is easy to maintain high accuracy because it is made. Further, the thrust bearing has a feature that even if the size of the bearing gap is reduced, the bearing loss can be prevented from becoming excessive by reducing the width of the bearing. The size of the gap at the bearing opening can be as small as the size of the bearing gap of the adjacent thrust bearing.

However, during the process of evacuating the inside of the vacuum vessel VV to a vacuum state or during a long-time operation, the gas contained in the liquid metal lubricant and the bearing surface are formed. The gas remaining in the material to be expanded may expand, and the liquid metal lubricant may be pushed out of the bearing opening. Even in this case, it is required that an action of pushing the liquid metal lubricant back into the bearing is generated. Even if the liquid metal lubricant is irreversibly pushed out of the bearing opening, it is necessary to prevent the lubricant from scattering into the vacuum space inside the vacuum vessel. In the present invention, in order to meet these requirements, as described below, having a space not filled with the liquid metal lubricant,
Annular low-pressure depressions 151, 152, 153 having low pressure are provided between the bearings.
152 and 153 are always kept at the same pressure as the vacuum space.

This will be described in more detail with reference to FIG. The description here will be made only for the vertically lower part shown in the figure. Bearing gap 11 of the second thrust bearing
1, and the bearing gap 109 of the first thrust bearing
Has annular bearing openings 120 and 121 that define respective substantial boundaries with the vacuum space. The bearing rotating body 102 is provided with annular low-pressure depressions 151, 152, and 153. In these portions, the size of the gap between the rotating surface and the fixed surface is as large as 1 mm or more.
There is substantially no bearing pressure. The low pressure recess 152 is adjacent to the bearing gap 111 of the second thrust bearing,
The low-pressure depression 153 is adjacent to the bearing gap 109 of the first thrust bearing, and a third low-pressure depression 151 is located between the low-pressure depression 152 and the low-pressure depression 153. Between the low pressure depressions 152 and 151 and the low pressure depressions 153 and 151
Between them, radial bearings are formed. In the above description, these bearing gaps are collectively referred to as 108.
Indicated by. Annular low-pressure depressions 151, 152, 15
The amount of the liquid metal lubricant is determined so that at least a part of 3 is not filled with the liquid metal lubricant in any case.

Annular low-pressure depressions 151, 152, 153
The means for controlling the amount of the liquid metal lubricant present therein will be described. A pipe opening at the vertical lower end of any of the low-pressure depressions 151, 152, 153
1, the pipe is guided outside the vacuum vessel VV, and the pipe is connected to a lubricant container provided outside the vacuum vessel VV. The liquid metal lubricant is allowed to move into the lubricant container, and the height of the lubricant container in the vertical direction can be changed so that the inside of the vacuum container VV is maintained in a high vacuum state. The height H of the liquid metal lubricant in the low-pressure depressions 151, 152, 153 is controlled from outside the vacuum vessel VV according to the principle of the communication pipe. For example, when the bearing rotating body 102 has stopped rotating, the lubricant container is moved vertically downward to lower the liquid level H in the lubricant existing area, and conversely, the bearing When the rotating body 102 is rotating, the lubricant container is moved vertically upward to increase the liquid level H in the low-pressure depressions 151, 152, and 153. By doing so, the low pressure depression 151,
The amount of the liquid metal lubricant in 152, 153 is
Can always be controlled to the optimum value from outside. In addition, not only the best lubrication state can be always maintained, but also the maintenance of the bearing becomes easy.

Next, the operation will be described. First, FIG.
An example will be described. Environmental low pressure depression 151,
Each of 152 and 153 has a sufficiently large volume, and the volume of the liquid metal lubricant stored therein is relatively small. When the bearing rotating body 102 stops rotating, no dynamic pressure is generated in each of the dynamic pressure sliding bearings. In addition, since the diameters of these bearings are large and the height difference is large, the liquid metal lubricant vertically above moves vertically below to create a space, and it is easy to form a gas passage to the vacuum space. Therefore, in this state, the low pressure depressions 151, 152, 15
The space inside 3 is in the same high vacuum state as the vacuum space of the vacuum container.

When the bearing rotating body 102 is rotating, a dynamic pressure is generated in each bearing. Bearing rotating body 102
When residual gas appears in the bearing, the bearing fixed body 101 or the liquid metal lubricant, the movement of the gas is hindered by the dynamic pressure of the bearing. However, when the rotation speed stops, the pressure of the gas relatively increases and the gas moves. These gases reach any of the annular low-pressure depressions 151, 152, and 153, and their volumes expand to lower the pressure. The gas collected in these annular low-pressure depressions 151, 152, and 153 is exhausted to a high vacuum through the passage formed by the movement of the liquid metal lubricant as described above when the bearing rotor 102 stops rotating. Is done. In this manner, the pressure in the bearing can be prevented from becoming excessively high, so that the liquid metal lubricant can be prevented from leaking out of the bearing mechanism, and stable operation can be continued for a long time.

Next, another preferred embodiment will be described with reference to FIG.
This will be described with reference to FIG. The description here will be made only for the vertically lower part shown in the figure. Between the low pressure depressions 151, 152, 153, there are provided communication paths 162, 163 composed of a large number of communication holes formed evenly over the entire circumference of the bearing rotating body 102, and a liquid metal lubricant is provided. Can be moved. Annular low pressure depression 151,
The amount of the liquid metal lubricant is determined so that at least a part of 152 and 153 is not filled with the liquid metal lubricant in any case.

The bearing rotating body 102 has an annular bearing opening 12.
An annular dent 132 is provided adjacent to zero, and an annular dent 133 is also provided near the other annular bearing opening 121. These annular recesses 132 and 133 are connected to the annular low-pressure recess 151 by communication passages 160 and 161 formed of a number of fine pores formed evenly around the entire circumference of the bearing rotor 102. Communicating passages 160, 1 consisting of these pores
Numeral 61 has a surface that is not wetted by the liquid metal lubricant and has sufficiently small holes that the surface tension of the liquid metal lubricant is large, so that the liquid metal lubricant does not normally enter these. As described above, the low pressure depressions 151, 15
Since at least a part of the second and second parts 153 is provided with a space which is not filled with the liquid metal lubricant in any case, the annular shape is formed through at least one of the communication paths 162 and 163 having a large number of communication holes. Low pressure depression 151
The interior space is maintained in a high vacuum state comparable to the vacuum area.
The annular low-pressure depression 151 corresponds to the annular depression 132,1.
The diameter is larger than 33 and the low pressure depression 15
Subject to centrifugal force in the direction of 1.

For unexpected reasons, when the liquid metal lubricant comes out of the annular bearing opening 120 or 121 into the vacuum space side and reaches the annular depressions 132 and 133, it receives centrifugal force and receives this liquid. The metal lubricant is moved to the low-pressure depression 151 through the communication passage 160 or 161 formed of a fine hole. This effect further reduces the possibility that the liquid metal lubricant leaks into the vacuum space outside the bearing mechanism CBG. Communication path 16 comprising communication hole
2,163 all annular low pressure depressions 151,15
2 and 153 are maintained in the same vacuum state as the low-pressure depression 151 through the movement of the liquid metal lubricant or through the space in the vertical upper part. In this manner, the pressure in the bearing can be prevented from becoming excessively high, so that the liquid metal lubricant can be prevented from leaking out of the bearing mechanism, and stable operation can be continued for a long time.

In the above description, the bearing mechanism CBG used for the cathode side rotating body CR has been described. However, the bearing mechanism ABG used for the anode side rotating body assembly AR also includes the rotating mechanism of the cathode power feeding mechanism SL1. The bearing mechanism composed of the hydrodynamic sliding bearing used in the part has the same structure.

When the bearing rotating body 102 is rotating at a sufficiently high speed, a relatively large bearing loss occurs in each of the above-described bearing gaps.
Is also thermally connected to the vacuum vessel VV, which is forcibly cooled from the outside, so that the temperature is kept low. The bearing rotator 102 is thermally coupled to the bearing fixed body 101 via a liquid metal lubricant in each bearing gap, and is kept at a sufficiently low temperature. In addition, the bearing rotating body 10
2, a cathode side rotating body assembly CR is mechanically connected,
A heating element such as an electron gun assembly EG is attached to the cathode side rotating body assembly CR. Particularly, in the anode-side bearing mechanism AGB, a large amount of heat flows from the X-ray target TG which generates a large amount of heat. Even in these cases, the temperature of the bearing mechanism can be kept sufficiently low for the above-described reason.

Although the present invention has been described with reference to illustrative embodiments, the present invention is not intended to be limited to the structure and form of the illustrated embodiments, but is to be departed from the spirit and scope of the invention. It is to be understood that various embodiments are possible and that various changes and modifications can be made. For example, in the present invention, three electron gun assemblies are attached, but one or three or more electron gun assemblies may be used. Further, in the present invention, the structure in which both the cathode side rotating body assembly CR and the X-ray target TG are rotated is shown. However, the cathode scan type X-ray having a structure in which the X-ray target TG and a portion connected thereto are fixed. It includes a generator and an X-ray CT scanner using the same. Needless to say, the bearing fixing body 101 may be configured as a part of a vacuum vessel. Also,
In the above embodiment, an example is shown in which a liquid metal that is liquid at room temperature is used as a lubricant.However, even if it is a solid at room temperature, it has a slightly higher melting point and is heated and liquefied before operation. Of course, the same effect can be obtained by operating. Further, the X-ray emission window for taking out the X-rays generated from the X-ray target outside the vacuum vessel may be integrated with the vacuum vessel or may be configured as a part of the vacuum vessel. If the X-ray attenuation rate at a portion is small, it can be regarded as an X-ray emission window. Vacuum container V
It is needless to say that V need not have a rotationally symmetric shape. It goes without saying that the center axis of the vacuum vessel and the center axis of the cathode side rotating body assembly or the anode side rotating body assembly may be deviated to some extent. It is needless to say that the X-ray target is divided and each divided part may have a gap. Of course, the low-pressure depression may be provided in the bearing fixing body. In the present invention, the size of the gap means the shortest distance from any point on one of the opposing surfaces forming the gap to the other of the opposing surfaces forming the gap. .

The present invention realizes an X-ray CT scanner capable of performing ultra-high-speed scanning as described above. The present invention can be applied to an electron beam irradiation device for irradiating an electron beam from a device. That is, the X-ray target and the parts related thereto, the X-ray X-ray distribution limiting mechanism, the fan direction distribution shaper WF, and other X-ray related parts are omitted from the device configuration described in the above embodiment, and the X-ray The emission window XW is changed to an electron beam emission window made of a thin titanium plate, and the direction of emitting electrons from the electron gun assembly EG is changed to the direction of the electron beam emission window. When this is used, it is possible to provide an electron beam irradiation apparatus which can be used for plastics, glass, and other modification treatments and has a large industrial effect.

[0037]

As described above, when the cathode scan type X-ray generator of the present invention is employed, the rotating part can be formed into a structure in which light parts are attached to a substantially rotationally symmetric structure inside the vacuum vessel, so that centrifugation is performed. Ultra-high-speed scan type X-ray C with less influence of force, for example, a scan time of 0.03 seconds
The T scanner can be realized at a low cost with a simple structure. In particular, a large amount of X
Lines can be generated, and a sufficiently high-quality image with little photon noise can be obtained. The generated X-rays are effectively received by the annular surface detector, and a large number of cross-sections in a wide area can be instantaneously photographed. Using this data, the three-dimensional internal structure of the subject can be instantaneously obtained. Be able to inspect. For this reason, it is possible to provide an X-ray CT scanner capable of faithfully and immediately imaging even a portion that moves quickly, such as a human heart, inside the subject. The bearing mechanism uses a hydrodynamic sliding bearing that uses liquid metal as a lubricant, so it can be used stably in a vacuum for a long time, and can keep the potential of the rotating part constant, and it is very small. The occurrence of unstable phenomena such as discharge can be prevented. Further, the heat generated inside through the dynamic pressure sliding bearing can be effectively guided to the outside of the vacuum vessel to be cooled. The bearing mechanism can be operated stably with sufficient reliability in a high vacuum environment. Since there is no external mechanical rotation mechanism and the related power supply and electronic circuits can be used in a stationary state, the overall reliability is high and the whole X-ray CT scanner is compact. It is possible to provide a highly reliable cathode scan X-ray generator that is not affected by operating characteristics even when a sudden inconvenience occurs inside the bearing mechanism, and an ultra-high-speed X-ray CT scanner using the same.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic cross section of a conventional X-ray CT scanner.

FIG. 2 is a cross-sectional view of a main part of an overall structure of a cathode scan type X-ray generator according to the present invention and an X-ray CT scanner using the same.

FIG. 3 is a diagram illustrating the principle of a cathode scan type X-ray generator according to the present invention and an X-ray CT scanner using the same.

FIG. 4 is an enlarged view of a cross section of a part of the cathode scan type X-ray generator according to the present invention, which is located vertically above at a certain moment.

FIG. 5 is an enlarged sectional view of a part of a cathode side rotating body assembly which is a main part of the cathode scan type X-ray generator according to the present invention.

FIG. 6 is a further enlarged sectional view of a part of FIG. 5, which is a main part of the cathode scan type X-ray generator according to the present invention.

FIG. 7 is an enlarged sectional view of a main part of another embodiment of the cathode scan type X-ray generator according to the present invention.

[Explanation of symbols]

ABG Anode-side bearing mechanism AR Anode-side rotating body assembly B Bed CBG Cathode-side bearing mechanism CR Cathode-side rotating body assembly DB Rear detector assembly DF Front detector assembly D1 Part of detector DF, DB D2 Detector DF, Part of DB D3 Detector DF, Part of DB EG Electron gun assembly F1 X-ray focal point F2 X-ray focal point F3 X-ray focal point HT High-voltage terminal LM1 Arc-shaped stator LM2 Arc-shaped stator M Subject RT1 Rotor RT2 Rotor SL1 Cathode feeding mechanism SLT Slit TG X-ray target VC Exhaust port VV Vacuum container WF Fan direction distribution shaper XW X-ray emission window 1 Cathode 2 Electron beam 101 Bearing fixed body 102 Bearing rotating body 103 Vertical upper part of radial bearing gap 104 Vertically above the bearing gap of one thrust bearing 105 Vertically above the end gap Part 106 Vertical upper part of the bearing gap of the second thrust bearing 107 Vertical upper part of the end gap 108 Vertical lower part of the radial bearing gap 109 Vertical lower part of the bearing gap of the first thrust bearing 110 Vertical lower part of the end gap 111 Vertical lower part of the bearing gap of the second thrust bearing 112 Vertical lower part of the end gap 120 Vertical lower part of the bearing opening 120 'Vertical upper part of the bearing opening 121 Vertical lower part of the bearing opening 121' Vertical upper part of the bearing opening 132 Annular depression 133 Annular depression 151 Low-pressure depression 152 Low-pressure depression 153 Low-pressure depression 160 Communicating path composed of fine pores 161 Communicating path composed of fine pores 162 Communicating path composed of communicating holes 163 Communicating path composed of communicating holes 217 Rotating torque Transmission mechanism 220 Insulator 1001 Conventional X Fixed frame of CT scanner 1002 Rotary frame of conventional X-ray CT scanner 1003 Bearing of conventional X-ray CT scanner 1004 X-ray tube of conventional X-ray CT scanner 1005 X-ray of conventional X-ray CT scanner 1006 Conventional X-ray Detector of CT scanner 1007 Electronic circuit of conventional X-ray CT scanner 1008 Controller of conventional X-ray CT scanner 1009 Rotation drive mechanism of conventional X-ray CT scanner

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G21K 5/02 G21K 5/02 X 5/04 5/04 E 5/08 5/08 X 5/10 5/10 M H01J 35/08 H01J 35/08 C 35/26 35/26

Claims (10)

[Claims] 1. A donut-shaped vacuum container for forming a vacuum space by maintaining a vacuum state inside the vacuum container, and supported in the vacuum space inside the vacuum container so as to be rotatable coaxially with a center axis of the vacuum container. A cathode side rotating body assembly, an electron gun assembly attached to a part of the cathode side rotating body assembly, a cathode attached to the electron gun assembly and emitting electrons, and A rotating portion of a cathode power supply mechanism for supplying power from the outside, an annular X-ray target mounted facing a surface including the orbital path of the cathode, and an X-ray generated on the surface of the X-ray target. An X-ray emission window for taking out of the vacuum vessel, a rotation drive mechanism for applying a rotational force to the cathode-side rotating body assembly, and a bearing rotatably supporting the cathode-side rotating body assembly in the vacuum vessel. Mechanism and the cathode And a bearing mechanism for rotatably supporting a rotating part of the power supply mechanism in the vacuum vessel. At least one of these bearing mechanisms is a part for fixing the bearing mechanism. Bearing fixed body,
A plurality of hydrodynamic sliding bearings which use a liquid metal, which is a liquid during operation, as a lubricant between these bearing fixed bodies and the bearing rotary bodies. Each of the dynamic pressure sliding bearings has an opposing bearing surface with a gap, and at least one of these bearing surfaces is provided with a herringbone-shaped bearing groove. The slide bearing includes a first thrust bearing that generates a dynamic pressure in a rotation axis direction, at least one radial bearing that generates a dynamic pressure in a rotation radius direction, and a second thrust bearing facing the first thrust bearing with a distance. Thrust bearings, and any two of these
A first low-pressure recess arranged in an annular shape having a low bearing pressure between the two bearings and having a space portion not filled with the liquid metal lubricant. Cathode scan type X-ray generator and X using the same
Line CT scanner. 2. A donut-shaped vacuum vessel for forming a vacuum space by holding the inside of the vacuum state, and supported so as to be coaxially rotatable in the vacuum space inside the vacuum vessel with the center axis of the vacuum vessel. An anode-side rotator assembly, an annular X-ray target attached to the anode-side rotator assembly, and an electron gun assembly attached to orbit around an X-ray target in a trajectory facing the surface of the X-ray target. A cathode mounted on the electron gun assembly and emitting electrons,
A cathode power supply mechanism for supplying power to the cathode from outside the vacuum vessel, and X-rays generated on the surface of the X-ray target.
An X-ray emission window for taking out the radiation outside the vacuum vessel;
It has a rotary drive mechanism that applies a rotational force to the anode-side rotating body assembly, and a bearing mechanism that rotatably supports the anode-side rotating body assembly in a vacuum vessel. And a bearing rotating body that is a part for fixing the bearing mechanism, and a bearing rotating body that is fitted to and rotated by the bearing fixing body, and a liquid is generated between the bearing stationary body and the bearing rotating body during operation. A plurality of hydrodynamic sliding bearings using a liquid metal as a lubricant, each hydrodynamic sliding bearing has a bearing surface facing with a gap, and at least one of these bearing surfaces has A herringbone-shaped bearing groove is provided, and the dynamic pressure sliding bearing includes a first thrust bearing that generates a dynamic pressure in a rotational axis direction, and at least one radial bearing that generates a dynamic pressure in a rotational radial direction. ,
A second thrust bearing facing the first thrust bearing at a distance is included, the bearing pressure is low between any two of these bearings, and the liquid metal lubricant is used. A cathode scan type X-ray generator comprising an annularly disposed first low-pressure depression having an unfilled space portion, and an X-ray CT scanner using the same. 3. Any two of said hydrodynamic sliding bearings are connected to a bearing opening which forms a substantial boundary between said liquid metal lubricant existing area and said vacuum space,
The bearing opening has a first surface in the bearing rotating body, a second surface in the bearing fixing body, and a gap sandwiched between the first surface and the second surface. Wherein the minimum radius of the surface forming the first low-pressure depression is larger than the maximum radius of the first surface or the second surface forming the bearing opening. 3. A cathode scan type X-ray generator according to claim 1, wherein the X-ray CT scanner uses the same. 4. Any two of the dynamic pressure sliding bearings are connected to a bearing opening forming a substantial boundary between a region where the liquid metal lubricant exists and the vacuum space,
This bearing opening, the first surface of the bearing rotating body,
A second surface of the bearing fixed body, and a gap sandwiched between the first surface and the second surface, wherein the first low-pressure depression is formed in the bearing opening. The cathode scan type X-ray generator according to any one of claims 1 to 3, wherein the cathode scan type X-ray generator has a communication path connected to the first surface or the second surface. X-ray CT scanner used. 5. An annular arrangement between any two of said hydrodynamic sliding bearings, having a space with a low bearing pressure and not filled with said liquid metal lubricant. 4. The method according to claim 3, wherein a second low-pressure depression is provided, and the second low-pressure depression has a communication passage connected to the first low-pressure depression. A cathode scan type X-ray generator and an X-ray CT scanner using the same. 6. A cathode scan type X-ray generator according to claim 4, wherein said communication passage has a surface which is not wetted by said liquid metal lubricant. , And an X-ray CT scanner using the same. 7. The communication path is characterized in that a pressure effect of a surface tension greater than a static pressure generated in the liquid metal lubricant occurs at an end of the communication path. A cathode scan type X-ray generator according to claim 6, and an X-ray CT scanner using the same. 8. A pressure effect of a surface tension generated in the liquid metal lubricant at an end of the communication passage is smaller than a pressure effect of centrifugal force acting on the liquid metal lubricant. A cathode scan type X-ray generator according to claim 7, and an X-ray CT scanner using the same. 9. A passage opening to said first low-pressure recess and leading to the outside of said vacuum vessel, through which the amount of liquid metal lubricant present in said first low-pressure recess is provided. The method according to any one of claims 1 to 8, wherein, while maintaining the inside of the vacuum vessel in a high vacuum state, the vacuum vessel can be changed from outside the vacuum vessel. A cathode scan type X-ray generator and an X-ray CT scanner using the same. 10. A donut-shaped vacuum container for forming a vacuum space by maintaining the inside of the vacuum state, and supported so as to be coaxial with the center axis of the vacuum container in the vacuum space inside the vacuum container. A cathode-side rotating body assembly, and an electron gun assembly attached to a part of the cathode-side rotating body assembly,
A cathode attached to the electron gun assembly for emitting electrons, a rotating portion of a cathode power supply mechanism for supplying power to the cathode from outside the vacuum vessel, and electrons accelerated by the cathode are emitted. An electron beam emission window for taking out, a rotation driving mechanism for applying a rotation force to the cathode side rotating body assembly,
A bearing mechanism for rotatably supporting the cathode side rotating body assembly in the vacuum vessel; and a bearing mechanism for rotatably supporting the rotating part of the cathode power supply mechanism in the vacuum vessel. At least one of these bearing mechanisms has a bearing fixed body that is a part for fixing the bearing mechanism, and a bearing rotating body that is fitted into the bearing fixed body and rotates. A plurality of hydrodynamic sliding bearings using a liquid metal, which is liquid during operation, as a lubricant are formed between the fixed body and the bearing rotating body, and each of the hydrodynamic sliding bearings has a bearing surface opposing a gap. A herringbone-shaped bearing groove is provided on at least one of these bearing surfaces, and the dynamic pressure sliding bearing includes a first thrust bearing that generates a dynamic pressure in the rotation axis direction, and a rotation radius. To generate dynamic pressure in the At least one radial bearing and a second thrust bearing facing the first thrust bearing at a distance are included. The bearing pressure is low between any two of these bearings, and An electron beam irradiator comprising: a first annular low-pressure depression having a space portion not filled with the liquid metal lubricant.