JPH0630231B2 - Plasma X-ray generator - Google Patents

Description

The present invention relates to a plasma X-ray generator for generating soft X-rays by forming high-temperature and high-density plasma by pulse discharge of a discharge tube using a coaxial electrode. Regarding

BACKGROUND OF THE INVENTION Plasma focus is known as a typical example of a discharge tube using a coaxial electrode. In this plasma focus, a discharge tube in which cylindrical electrodes are coaxially arranged is filled with a gas such as deuterium, and a pulse voltage is applied from a capacitor to turn the gas into plasma, and the plasma is sandwiched between the electrodes. It is accelerated in a closed space to cause the tip of the electrode to focus. Further, this plasma focus has a high temperature and high density plasma formed therein, and serves as a radiation source for generating neutrons.

However, since high-temperature, high-density plasma generated in this plasma focus emits strong soft X-rays, it has recently attracted attention as an X-ray source.

As mentioned above, this plasma focus has a simple structure and operation, and the high brightness of the source makes it excellent in X
Although it has the potential of becoming a radiation source, there is the problem that the position of the spot that emits soft X-rays changes with each discharge.

That is, it is expected that the spots of the plasma focus will be formed on the axis of the cylindrical electrode, but in reality, they are often off-axis, and even if they occur on the axis, their position may fluctuate. . This state is, for example,
W. H. Bostick.V.Nardi and W.Prior: X-ray fime Str
ucture of dense plasma in a coaxicl accelerator, JP
It becomes clear from the literature of lasma Physics. Vol8, pt1, pp7 (1972). The instability of the plasma itself is known as the cause of such fluctuations, but other causes are not clear.

As a solution to such a problem, in Japanese Patent Application No. 59-234925 filed by the same applicant, in the space in front of the open end of the coaxial electrode, the disturbance or distortion of the electric field and magnetic field that disturb or disturb the plasma pinch is removed. Thus, there has been proposed one in which the spot of the plasma focus is set at a fixed position. This is to provide a shield with good electrical conductivity whose inner surface is a sphere or a shape close to a sphere to cover the space including the end of the coaxial electrode, and the potential of the shield is equal to or close to that of the outer cylindrical electrode. It is configured to maintain a constant potential.

However, the structure thus constituted has a problem that X-rays of high brightness cannot be extracted as compared with the structure without the shield.

[Object of the Invention]

It is an object of the present invention to provide a plasma X-ray generator capable of extracting X-rays of high brightness, as well as being able to set the spot of the plasma focus at a fixed position without fluctuation.

[Outline of Invention]

In order to achieve such an object, the present invention is such that the shield covering the space including the end of the above coaxial electrode is made of a mesh metal. By thus forming the shield body in a mesh shape, it becomes possible to prevent the gas density near the shield body from rapidly increasing during plasma focus, and the X-rays having high brightness generated at the end of the coaxial electrode can be prevented. It can be taken out almost as it is without being affected by the gas density.

Example of Invention

Hereinafter, the present invention will be described using examples. FIG. 1 is a sectional view of a plasma focus discharge tube according to the present invention.
In this discharge tube, an inner cylindrical electrode 1 which is an anode and an outer cylindrical electrode 2 which is a cathode are coaxially arranged, and both electrodes are
They are insulated from each other by a glass insulator 3. These are housed in a discharge vessel 4 and have neon, argon,
A gas such as krypton or xenon is filled at 0.1 to 1 Torr. A charged capacitor 5 is connected to both electrodes via a discharge switch 6. When this discharge switch 6 operates, a high voltage pulse is applied between both electrodes,
Dielectric breakdown occurs on the surface of the glass insulator 3 and plasma is generated. The plasma receives a force from an electric field and a magnetic field between the electrodes and moves along the electrodes, and if the end of the electrodes is excessive, the plasma receives the pressure of the magnetic field to focus, and the vicinity of the axis of the tip of the inner cylindrical electrode 1 A plasma hot spot is formed on the soft X
It emits a line.

At the tip of the electrode, a shield 7 made of a spherical mesh metal is provided so as to enclose the electrode. The center of the spherical shield 7 is aligned with the axis of the tip of the inner cylindrical electrode 1 and covers a portion of the coaxial electrode, thereby enclosing a space 8 in which plasma is pinched, and having the same potential as the outer cylindrical electrode 2. Is kept at.

In this shield 7, a beryllium window 9 is formed on the axis of the inner cylindrical electrode 1, and the other portions are reticulated.

As described above, in this embodiment, since the shield 7 has a mesh shape, the gas density in the vicinity of the shield 7 in the gas space 8 is
It is possible to prevent a rapid increase in plasma focus. That is, when the gas density is high, the transmittance of soft X-rays is poor, and even if the tip of the inner cylindrical electrode 1 has high brightness X
Even if a line is generated, it is attenuated in the gas space near the shield 7. However, since the shield 7 has a net-like shape in this embodiment, neutral gas molecules during plasma focus pass through the mesh. Since it escapes to the outside, there is no increase in gas density near the plasma focus point. Therefore, the generated X-rays can be effectively extracted to the outside.

In the discharge tube of this example, the outer diameter of the inner cylindrical electrode was 25 mm, the inner diameter of the outer cylindrical electrode was 60 mm, and the length was 1 mm.
It has a diameter of 50 mm and a shield of 150 mm. The openings 9 may also be used as the mesh of the shield 7.

FIG. 2 shows another embodiment according to the present invention, which is an example in which a hemispherical metallic shield 7 is provided with a large number of circular holes 11 and the same effect of meshing the shield 7 is obtained. Have.

Further, FIG. 3 shows another embodiment of the present invention, and in this case also, the same effect as when the shield 7 is meshed is obtained.

FIG. 4 shows another embodiment according to the present invention, in which the shield 7 is composed of a set of a plurality of metallic fingers 13a to 13e curled in the axial center direction.

〔The invention's effect〕

As described above, according to the present invention, in the plasma X-ray having the shield covering the space including the tip of the coaxial electrode,
Since the shield has a through hole for allowing gas between the electrodes to pass therethrough, it is possible to take out high-intensity X-rays generated at the tip of the electrode without weakening.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the plasma X-ray generator according to the present invention, and FIGS. 2 to 4 are block diagrams showing other embodiments of the shield of the plasma X-ray generator. is there. 1 ... Inner cylindrical electrode that is an anode, 2 ... Outer cylindrical electrode that is a cathode, 3 ... Glass insulator, 4 ... Discharge container, 5 ...
... condenser, 6 ... discharge switch, 7 ... shield according to the present invention, 9 ... opening for extracting X-ray, 10 ... X-ray extracting window.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Hirasawa 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Ltd. Central Research Center

Claims (1)

[Claims] 1. A X-ray is generated by charging or injecting gas into a discharge tube provided with at least a pair of electrodes arranged coaxially, charging and applying a pulse voltage from a capacitor to plasma the gas. In the plasma X-ray generator, a shield body is provided at the tip of the pair of electrodes, the shield body being bent toward the axial center side of the outer electrodes, and the shield body is formed with a passage hole portion for allowing gas between the electrodes to pass therethrough. A plasma X-ray generator characterized in that.