JPS63124351A - X-ray tube device - Google Patents

Abstract

PURPOSE:To obtain excellent resolution by making a cathode structure be composed of a flat plate filament for a small focal point and a coiled filament for a large focal point, both of which are installed in a focusing electrode of the cathode structure. CONSTITUTION:When a positive potential to a flat plate filament 23 for a small focal point is applied to a focusing electrode 13 by a power source, a coiled filament 24 for a large focal point and the electrode 13 are operated essentially in equipotential states. Hence, an electron beam focal point formed at a X-ray focal point position X on a rotary anode target 11 has a single- humped distribution e1 of electron density generated by the filament 23 on a flat electronic radiation surface. A focal point distribution of electron density generated by the filament 24 is double-humped e2. The small focal point is a X-ray focal point less than 0.2 mm in diameter and its size can be more largely changed by the bias potential applied to the electrode 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an X-ray tube device, and particularly to an X-ray tube device having multiple focal points.

(Prior Art) X-ray tube devices are often used for medical purposes, for example, for X-ray diagnosis, and so-called rotating anode X-ray tubes are used for stomach examinations and the like. In some cases, a single X-ray tube can selectively use a small focus and a large focus.

An example of this will be explained with reference to FIG. Rotating anode target 1
Focusing grooves 14 and 15 are formed in the single focusing electrode 13 of the cathode structure 12, which is provided facing the cathode assembly 1, so as to face the X-ray focal position X on the target, and each of them has a coil-shaped groove. A small focus filament 17 and a large focus filament 17 are arranged.

In particular, small focus is essential for enlarged photography, and today it is
．． An ultra-fine X-ray focus of less than 2 mm, and even less than 50 μm, is required.

(Problems to be Solved by the Invention) The electron emitting cathode, each of which is made of a coiled filament, focuses a bimodal small focus electron density distribution e1 and a large focus electron density distribution e2 on the target. . Moreover, even at a small focal point, the electron distribution has a wide base, and when such a focal point is shaded by xis, sufficient resolution cannot be obtained, as shown by the dotted curve R in FIG.

In view of the above-mentioned circumstances, the present invention has been developed to provide an
The purpose is to provide a wire tube device.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a cathode assembly provided opposite to an anode target having a small focus plate thickness of 5.
This is an X-ray tube device comprising a flat filament of tungsten material with a diameter of 0 μm or less and a coil filament for a large focus.

(Function) According to the present invention, X-rays can be emitted by selectively forming X-rays at a minute focus of less than 0.2 mm and a large focus larger than that, and the flat filament for small focus is particularly effective. X-ray imaging with high resolution is possible.

(Example) An example will be described below with reference to the drawings. Identical parts are designated by the same reference numerals.

The embodiments shown in FIGS. 1 to 3 show cathode structures for X-ray tubes. 12 is a cathode structure, 13 is a focusing electrode, 2
1 is a focusing groove for a small focus, 22 is a focusing groove for a large focus, 23 is a flat filament for a small focus, 24 is a coil filament for a large focus, 25.26 is a pair of filament support pillars, 27
．． 28 is a supporting sleeve, 29 is a ceramic insulating support plate, 30 is a supporting cup, 31 is a shielding electrode, 32 is a ceramic fixing ring, 33 and 34 are coil filament rigid supporting irons, and 35 is a supporting cylinder.

The flat filament 23 has a thickness of 50 μm or less, for example, 25 μm.
m plate thickness of tungsten material (including tungsten alloy)
Both sides of the central flat part are folded back into a U-shape, and both ends 23a and 23b are supporting columns 25.2.
It is fixed to the tip of 6 by welding.

The shielding electrode 31 closely surrounds the electron-emitting flat surface at the center of the flat filament 23, is held by a support cup 30, and is electrically short-circuited to the filament 23 by a conductor (not shown) to have the same potential. . Ceramic fixing ring 29 is fixed to the lower end of focusing electrode 13 by support cylinder 35 . Thereby, the shielding electrode 31 and the focusing electrode 13
It is electrically separated from the

One end leg of the coiled filament 24 for large focus passes through the insulating ring 32 and is led out to the outside, and the other leg is electrically short-circuited and fixed to the focusing electrode 13 by a support rod 34.

During operation, a positive potential is applied to the focusing electrode 13 with respect to the flat filament 23 from a power source (not shown), and the coiled filament 24 and the focusing electrode 13 are operated at substantially the same potential. As a result, as shown in FIG. 4, the electron beam focus connected to the X-ray focus position becomes.

The focal electron density distribution due to the coiled filament 24 has a bimodal distribution e2. A small focus is an X-ray focus smaller than 0.2 mm, the size of which can be varied relatively significantly by the bias potential of the focusing electrode.

With this small focus filament, as shown by the solid line curve P in the diagram showing the spatial frequency and modulation transfer function (MTF) in Figure 6, the - 〇- It is proven that resolution and contrast can be obtained.

In the embodiment shown in FIG. 5, a filament 23 with a flat electron emitting surface for small focus is arranged in the first focusing electrode 13, and a coiled filament 24 is arranged in the focusing electrode 13a on the opposite side. This coil filament 24 is mainly used in the evacuation process to heat the anode target by electron bombardment and release gas.

In the figure, numeral 35 is a vacuum container, 36 is an X-ray emission window,
37 is a rotor part.

[Effects of the Invention] As explained above, according to the present invention, it is possible to selectively emit X-rays at a minute focus of less than 0.2 mm and a large focus larger than that within a single X-ray tube device. In particular, the small focal point flat filament provides excellent resolution.
Line photography is possible.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a main part showing an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view at 2-2 in FIG. 1, and FIG. 3 is a vertical cross-sectional view at 3-3 in FIG. , Figure 4 is a schematic diagram showing the electron beam trajectory and its focal electron density distribution, and Figure 5 is a schematic diagram showing the electron beam trajectory and its focal electron density distribution.
The figure is a longitudinal sectional view showing another embodiment of the present invention, FIG. 6 is a characteristic diagram without a modulation transfer function, and FIG. 7 is a schematic diagram of an electron beam in a conventional structure. 11... Anode target, 13.13a... Focusing electrode, 23... Flat filament with flat electron emitting surface, 2
4... Coiled filament.

Claims (5)

[Claims] (1) In an X-ray tube device in which an anode target and a cathode assembly are provided facing each other in a vacuum vessel, the cathode assembly is a small focus filament having a flat electron emitting surface provided in a focusing electrode. and a large focus coil filament. (2) The X-ray tube device according to claim 1, wherein the small focus filament having a flat electron emission surface is made of tungsten material with a plate thickness of 50 μm or less. (3) The small focus filament with a flat electron emission surface forms an X-ray focus of less than 0.2 mm on the anode target, and the large focus coil filament forms an X-ray focus of 0.2 mm or more on the target. An X-ray tube device according to claim 1, which forms an X-ray tube device. (4) A positive bias potential is applied to the focusing electrode covering the small focus filament, which has a flat electron emission surface, and the large focus coil filament and the focusing electrode covering it are at the same potential. An X-ray tube apparatus according to claim 1, which is operated. (5) The X-ray tube device according to claim 1, wherein the small focus filament and the large focus coil filament having a flat electron emission surface are arranged within a single focusing electrode.