JPS6226752A - Method for generating soft x-ray of high intensity - Google Patents

Abstract

PURPOSE:To produce soft X-ray of high intensity by applying high-output electromagnetic milliwaves and submilliwaves to a vacuum case from outside the case in such a manner as to produce a region of electronic cyclotron resonance the frequency of which coincides with that of said electromagnetic waves. CONSTITUTION:A vacuum case 2 is installed either inside a mirror magnetic field coil 1 or inside both the coil 1 and a multipolar magnetic field coil 1'. Various types of gases are fed through the case 2 at proper pressure. High- output electromagnetic milliwaves and submilliwaves (A) are applied through a window 4 in such a manner as to produce a region of electronic cyclotron resonance the frequency of which coincides with that of the above waves (A) inside the vacuum case 2. The gases are completely ionized into high- temperature plasma by resonantly heating electrons. As the result, soft X-rays are produced and they are discharged through a window 5. Therefore, soft X-rays of high intensity can be produced by using a compact generator with a high gaseous pressure of 10<-1>Pa.

Description

DETAILED DESCRIPTION OF THE INVENTION As an X-ray generation method, one based on the collision of a high-energy electron beam with a solid material (target) is well known as an X-ray tube in various energy ranges. but,
When the energy of X-rays falls into the soft X-ray region of about 0.1-10 keV, the generation efficiency becomes extremely low and it cannot be used as a high-intensity source.On the other hand, one of the needs of recent new technology development is that There is a strong need for soft X-rays for processing, and high-intensity soft X-ray sources are attracting a lot of attention.

So far, candidates for soft X-ray generation methods include Sole (SOR Nishin Chrotron Orbital Radiation) and pulsed plasma sources, but Sole is said to have the best quality as a source. It is. However, the current situation is that there are many problems that need to be solved from a practical point of view, such as the beam size, the huge size of the device, and the cost.

On the other hand, research is being conducted on plasma X-ray sources that utilize short-pulse laser plasma or pinch plasma.

In contrast, the plasma generation method using ECR, that is, the electron cycloton resonance phenomenon, which will be described next, belongs to a completely new type of plasma generation method.

This ECR plasma source has been known for a long time and is widely used in fields ranging from nuclear fusion research to process technology9, and it is also known that X-rays can be generated depending on external conditions. However, soft x1a has not yet been investigated much, and its use as a radiation source has not been developed.

Based on this background, the present invention is based on nuclear fusion plasma and SO
This is a method of generating high-intensity soft X-rays that is much more compact than R, etc., has a long life, is electrodeless, and can easily obtain a variety of extremely strong emission line spectra, and is expected to be used in a wide range of new fields. It is intended to be utilized.

First, let's explain the basics of how it occurs. Various gases at appropriate pressures are flowed into a vacuum container in a simple mirror magnetic field or in an average minimal magnetic field in which a multipolar magnetic field is to be added, and 'Fi, a type of microwave, is applied from the outside. do. When there is a region inside a vacuum container where the microwave frequency and the cyclotron resonance frequency of electrons in a magnetic field match, even a small amount of microwave input will cause the electrons to be resonantly heated and reach a high temperature, generating plasma. From this, continuous X-rays such as bremsstrahlung radiation and recombination radiation of gases, and characteristic X-rays with line spectra corresponding to each gas are generated.

Now, conventionally, in ECR plasma generation in an open system magnetic field configuration such as a mirror magnetic field, the electromagnetic waves used are mostly in the so-called Senna wave region. Intensity of X-rays from plasma I! generally increases in proportion to its electron density N. At this time, the frequency f of the incident electromagnetic wave coincides with the electron cyclotron resonance frequency f, and the plasma circumference Ce is a function of N.
e wave number f (=8960 N
Therefore, in order to increase the X-ray intensity I, it is necessary to increase N, but at the same time e

Since this is accompanied by p, it is necessary to increase f accordingly. Then, when using electromagnetic waves in the range of millimeter waves to submillimeter waves compared to conventional Senna waves, Ne increases by two to three orders of magnitude to 19 due to the relationship f=f. This is an important point in terms of wood quality in obtaining high-intensity soft X-rays. Due to the relationship between the wavelength of electromagnetic waves and the electron density, in order to obtain a large plasma, the conventional centimeter waves have no practical meaning, and it is essential to use millimeter to submillimeter waves. Hail to you that you are in this condition.

Now, since real plasma is obtained by the ionization phenomenon of gas, it is necessary to increase the gas pressure at the same time to obtain a high electron density.6For example, in millimeter waves, the wavelength is 5 mm.
When the corresponding r is 60 GHz, the maximum N that can be obtained is approximately 4°5XIO13cm-3.

If the magnetic field structure has a high plasma confinement ability, a high electron density can be obtained even with a small gas pressure, but in the mirror magnetic field or composite minimum magnetic field structure considered here, the plasma loss in the axial direction is very large. Therefore, high neutral gas pressure corresponding to high Ne is required.
For example, the gas pressure corresponding to N mentioned above is approximately 2 X to
(Pa. Therefore, when creating ECR plasma using electromagnetic waves ranging from millimeter waves to submillimeter waves, to-2-1
A gas pressure state of about 0°Pa is an essential condition for generating high-intensity soft X-rays.

On the other hand, when the gas pressure increases, the collision phenomenon between particles becomes more intense, and the electron temperature decreases, dropping by as much as 1 degree Celsius, and soft X-rays are no longer emitted. Plasma generation with strong X-ray emission has not been reported so far in a magnetic field as described here and at a pressure as shown above. The reason for this is that the electromagnetic waves used were mainly centimeter waves, and the input per single mirror was less than a few kW, so it was not possible to evaluate them and it remained unclear. In contrast, in the present invention, the input to the plasma is several kW or more at shorter wavelengths such as millimeter waves and submillimeter waves.
As will be shown later, only in such cases, even at the above-mentioned high pressure, it became possible to create plasma that was completely ionized and accompanied by strong X-ray emission.

Figure 1 shows an outline of the generation method.As for the method of injecting electromagnetic waves, there are two methods: applying the electromagnetic waves from the direction perpendicular to the east of the magnetic field at the center of the vacuum vessel, and applying the electromagnetic waves from the axial direction along the lines of magnetic force. I'm cute.

Figure 2 shows an example of data obtained by this method. In this case,
From the direction perpendicular to the simple mirror magnetic field with a mirror ratio of 2, the wavelength is 5.
It shows the time change of the soft X-ray spectrum that occurs when electromagnetic waves of mm are incident. The millimeter wave input is 65kW, the gas used is argon gas, and the pressure is 2.3×10°l Pa.
It is. Further, the millimeter wave pulse width corresponds to the case of 100 zs. As is clear from the figure, alpha soft X-rays are generated from argon at 3 keV much more strongly than continuous X-rays. Furthermore, although the pulse width of the incident millimeter wave is Looms, the generation time of kα rays reaches 200 IllS,
This is an important feature because the high-temperature electrons generated by this ECR phenomenon remain for a long time even after the millimeter wave is cut off, and continue to generate strong soft X-rays while ionizing neutral gas. As shown in this figure, by applying such high output millimeter waves, powerful soft x! This shows that a occurs.

This π is further clarified in detail in FIG. 3 from the input dependence of the incident millimeter wave. That is, at a gas pressure of 2×10 (Pa), significant soft X-ray emission has been observed when the input Pg to the plasma is 204 or higher.Therefore, soft X-ray generation at high pressures as in the present invention requires a This can only be obtained by injecting high-power millimeter waves.

Now, it is very easy to obtain soft X-rays with different energies; all you need to do is change the type of gas used.1 For example,
Using the same rare gas neon, it is possible to obtain characteristic X-rays of 800 eV, and using carbon compounds etc., it is possible to obtain characteristic X-rays of 500 eV.
alpha rays are obtained from carbon of about 100%. Furthermore, by using a gas mixture having various characteristic X-rays, soft X-rays of various levels can be easily obtained.

It should be noted here that, according to the present invention, as shown in Figure 2, most of the incident energy becomes characteristic X-rays when it is converted into X-rays, and continuous X-rays also have the characteristic that they are strongest near the X-rays. is based on.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the soft X-ray generation method in the present invention,
FIG. 2 shows the time variation of α soft xVj in argon at 3 keV as an example obtained by this method. Figure 3 shows 3 keV, argon and α-ray intensity gas pressure 2, O
The electromagnetic wave input dependence at X tot Pa is shown. A: Electromagnetic waves B: Soft X-ray mirror magnetic field coil ■“Multi-pole magnetic field coil ■Vacuum container ■Magnetic field lines ■“Electron cyclotron +! 3i area・
■Electromagnetic wave entrance window ■Soft X-ray emission window Procedure amendment November 28, 1985

Claims (1)

[Claims] (I) A device in which a vacuum container is placed in a simple mirror magnetic field or a composite minimal magnetic field, and various gases at appropriate pressures are introduced into the container, in which a high-output electromagnetic wave is applied from the outside, and its frequency is It is characterized by creating a resonance region inside the vacuum container that matches the electron cyclotron resonance frequency, thereby resonantly heating the electrons and turning the gas into a fully ionized high-temperature plasma state, thereby generating high-intensity soft X-rays. Soft X
Line generation method. (II) To achieve the above purpose, millimeter waves and submillimeter waves are used as electromagnetic waves, and the pressure of the incoming gas is kept high to obtain a high electron density, and the electromagnetic waves used are increased to facilitate soft X-ray emission. It is characterized by being an output. (III) Regarding the types of soft X-rays generated, we mainly focus on characteristic X-rays, which are sharp resonance lines, and continuous X-rays around them, which are generated when using a single gas or a mixture of various gases. shall be.