JP2827121B2 - X-ray tube with switchable point focus and line focus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray tube having a water-cooled target, and more particularly to an X-ray tube capable of switching between a point focus and a line focus.

[Prior Art] In an X-ray tube, an electron beam from an electron gun is linearly applied to a target to generate X-rays. Therefore, the portion where X-rays are generated becomes linear. Depending on the direction in which this linear X-ray is taken out from the X-ray tube, it is used as a point-focus or line-focus X-ray source.

In an analyzer using X-rays or the like, it is necessary to use a point focus and a line focus depending on the purpose of use, and it is convenient if one X-ray tube can properly use these. Conventionally, these are properly used depending on the direction of extracting X-rays from the X-ray tube.

[Problem to be Solved by the Invention] If the point focus and the line focus are to be switched in one specific direction, in the sealed X-ray tube,
Rotating the entire tube by 90 degrees will cause the setting to be reset.On the other hand, in the case of an open X-ray tube, the vacuum will be returned to the atmosphere and the mounting angle of the target and electron gun will be changed. In both cases, it takes time. In the latter case, in principle, switching can be performed simply by changing the attachment angle of the electron gun, but the shape of the cooling water jet on the back of the target becomes linear in accordance with the area where the electrons hit. Therefore, there is a situation that the mounting angle of the target also needs to be changed.

In view of the above, an object of the present invention is to provide an X-ray tube that can switch between a point focus and an X-ray focus in the same direction with a very simple operation.

[Means for Solving the Problems] To achieve the above object, X according to the invention of claim 1 is used.
In the wire tube, the cooling water jet on the back side of the target surface to which the electron beam is applied has a cross shape, and the electron gun is rotatably mounted on the vacuum vessel.

Further, in the X-ray tube according to the second aspect of the present invention, the shape of the cooling water jet on the back side of the target surface on which the electron beam is applied is formed in a cross shape, and the traveling direction of the electron beam from the electron gun toward the target is changed. A lens is provided in a vacuum container, and the polarity of a current flowing through the electromagnetic lens can be switched.

[Operation] In the invention of claim 1, if the electromagnetic gun is rotated by 90 degrees with respect to the vacuum vessel, the linear electron beam irradiation area on the target surface rotates by 90 degrees, and the point focus becomes the line focus. Or, conversely, switching is possible. Since the cooling water jet on the back of the target has a cross shape, the electron beam irradiation area is always sufficiently cooled by the cooling water even if the linear electron beam irradiation area on the target surface is rotated by 90 degrees. Will be. That is,
The target remains fixed.

In the invention of claim 2, instead of rotating the electron gun, the traveling direction of the electron beam from the electron gun toward the target is changed. That is, the electron gun may be fixed. By switching the polarity of the current flowing through the electromagnetic lens, a linear electron beam irradiation area on the target surface is rotated by 90 degrees. The shape of the cooling water jet on the back surface of the target is the same as that of the first aspect, and the target is similarly cooled.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a partial sectional front view of an embodiment of the first aspect of the present invention. This X-ray tube 10 is an open type,
Inside, a target 14 and an electron gun 16 are included. Electron gun 16
Is vacuum-sealed by an O (o) ring 18 and a bearing 20
Is rotatably attached to the vacuum container 12.
The O-ring 18 can be changed to another sealing means, for example, a sealing means using a magnetic fluid.

As shown in FIG. 2, the target 14 is of a water-cooled type. The cooling water 22 passes through the inner passage 24 of the target 14 and gushes out of the outlet 26 to cool the back side of the target surface 28 on which the electron beam is applied. Thereafter, the cooling water is discharged through the outer passage 30. As shown in FIG. 3, the ejection port 26 has a cross shape, and sufficiently cools the target surface 28 within the cross shape.

Next, a method of using the X-ray tube will be described. First, as shown in FIG. 4, it is assumed that the electron gun is set so that the filament 32 is oriented vertically. In this case, the electron beam 34 emitted from the filament 32 is a line extending in the vertical direction, hits the target surface 28, and a linear X-ray beam 36 is emitted toward the front left of FIG. That is, an X-ray 38 having a line focus is obtained. The broken line drawn on the target surface 28 indicates the position of the cooling water jet 26 on the back surface.

Next, the electron gun 16 is turned clockwise when viewed from the right in FIG.
When the filament 32 is rotated by 90 degrees, the filament 32 is rotated 90 degrees clockwise in FIG. 4 to the state shown in FIG. In this state, the electron beam 34 emitted from the filament 32 becomes a line extending in the horizontal direction, and as a result, a point-focus X-ray 40 is obtained in the left front direction in FIG.

FIG. 6 is a partial sectional front view of one embodiment of the second aspect of the present invention. The X-ray tube 50 includes a target 14 and an electron gun 16 inside a vacuum vessel 12. This tube has no mechanically movable parts and may be of an enclosed type or an open type. The electron gun 16 is fixed to the vacuum container 12. The filament 32 of the electron gun 16
As shown in FIG. 7, it is fixed in a state inclined at 45 degrees from the vertical direction. Returning to FIG. 6, an electromagnetic lens 52 is provided outside the vacuum vessel 12. The electromagnetic lens 52 is
It is formed by a coil 56 whose periphery is covered with a ferromagnetic material 54 such as iron. A part of the ferromagnetic material 54 is open, and a magnetic field 58 is formed in the vicinity thereof. This magnetic field 58 affects the electron beam.

The coil 56 of the electromagnetic lens 52 is connected to a power supply 60, and the polarity of the current flowing through the coil 56 is switched by a changeover switch 62. That is, the two-pole double-throw changeover switch 62
6 can be switched to the right or left in FIG. 6 to switch the polarity of the current. The target 14 of the X-ray tube 50 has the same cooling structure as shown in FIGS. 2 and 3. I have.

Next, a method of using the X-ray tube 50 will be described. First,
It is assumed that the changeover switch 62 is tilted to the left in FIG. In this case, in FIG. 7, the electron beam 34 emitted from the filament 32 of the electron gun 16 travels at first as a line inclined at 45 degrees with respect to the vertical direction. When the whole rotates in the direction of 64 and hits the target surface 28, it is in a vertical state. Therefore,
At this time, an X-ray 38 having a line focus is obtained in the left front direction in FIG.

Next, when the changeover switch 62 in FIG. 6 is tilted to the right, the polarity of the current flowing through the coil 56 of the electromagnetic lens 52 switches,
The magnetic field 58 reverses. Then, in FIG. 8, the electron beam 34
This time, it rotates 45 degrees as a whole in the direction of arrow 64 and hits target surface 28. As a result, a point-focus X-ray 40 is obtained.

7 and 8, the target surface 28 is sufficiently cooled by the cooling water jetted from the cross-shaped jet port 26.

The rotation angle of the electron beam from the electron gun to the target is determined by the distance from the electromagnetic lens to the target surface, the strength of the magnetic field by the electromagnetic lens, and the acceleration voltage of the electrons. Can be rotated by 45 °. In the present embodiment, when the distance from the center of the magnetic field by the electromagnetic lens to the target surface is 130 mm, the inner diameter of the electromagnetic lens is 34 mm, the ampere turn of the electromagnetic lens is 920 to 950 ampere, and the applied voltage of the X-ray tube is 50 KV. , The electron beam is rotated by 45 °.

[Effects of the Invention] The invention of claim 1 is that the cooling water jet of the target is formed in a cross shape and the electron gun is rotatably mounted. There is an effect that the focus can be switched.

According to a second aspect of the present invention, the cooling water jet port of the target is formed in a cross shape and the polarity of the current flowing through the electromagnetic lens is switchable, so that the electric circuit of the electromagnetic lens can be operated without moving the target and the electron gun at all. There is an effect that the point focus and the line focus can be switched only by the switch operation.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional front view of one embodiment of the invention of claim 1, FIG. 2 is a longitudinal cross-sectional view of a target, FIG. 3 is a cross-sectional view taken along line III-III of FIG. The figure is a perspective view showing the trajectories of the electron beam and the X-ray, FIG. 5 is a perspective view similar to FIG. 4 showing another operation state, and FIG. 6 is a partial cross section of one embodiment of the invention of claim 2. FIGS. 7 and 8 are perspective views similar to FIGS. 4 and 5. FIG. 10 X-ray tube 12 Vacuum container 14 Target 16 Electron gun 20 Bearing 26 Cooling water jet 38 X-ray at line focus 40 X-ray at point focus 52 … Electromagnetic lens 62 …… Changeover switch

Claims (2)

(57) [Claims] In an X-ray tube including an electron gun and a water-cooled target inside a vacuum vessel, a cooling water jet on the back side of a target surface to be irradiated with an electron beam has a cross shape, and the electron gun is The electron beam irradiation area on the target surface in a state before the electron gun is rotated by 90 degrees, and the electron beam on the target surface in a state after the electron gun is rotated by 90 degrees. An X-ray tube switchable between a point focal point and a line focal point, wherein the cross-shaped cooling water jet port is disposed so as to be located behind a region including a line irradiation region. 2. An X-ray tube comprising an electron gun and a water-cooled target inside a vacuum vessel, wherein a cooling water jet is formed in a cross shape on the back side of a target surface on which an electron beam is applied. An electromagnetic lens that changes the traveling direction of the electron beam toward the target is provided in the vacuum container, and the electron beam irradiation area on the target surface is rotated by 90 degrees by switching the polarity of the current flowing through the electromagnetic lens, The cross-shaped cooling water jet is positioned so as to be located behind a region consisting of an electron beam irradiation region on the target surface before switching the polarity and an electron beam irradiation region on the target surface after switching the polarity. An X-ray tube capable of switching between a point focus and a line focus, wherein an exit is disposed.