JP2002350593A - Method and device for condensing x-ray - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate inconvenience in measurement with conventional X-ray condensation method performed with coaxial two-dimensional zone plate and resulting fluctuation of focus position according to the wave length λ (energy) of incident X-ray. SOLUTION: Two one-dimensional fresnel zone plates are arranged perpendicularly and the inclination angles of the plates are varied according to the wave length λ (energy) of incident X-ray so that a focus position is made stable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is used in an analysis or measurement apparatus using X-rays, and typical examples include an X-ray microscope and an X-ray microprobe. When X-rays are slightly condensed and irradiated on an object, local information is obtained and quantitative analysis can be performed. Physical quantities to be measured include transmitted X-rays, fluorescent X-rays, and photoelectrons. Furthermore, each element has a characteristic X-ray absorption edge, and the absorption coefficient (or transmittance) differs by about one digit even before and after the absorption edge even with a slight energy difference. This is an invention particularly effectively used for analysis.

[0002]

2. Description of the Related Art As a conventional technique for collecting X-rays, there is a two-dimensional Fresnel zone plate utilizing Fresnel diffraction. As shown in FIG. 2, in the case of the intensity modulation type, the intensity modulation type has a disk shape in which zones opaque to X-rays and zones transparent to X-rays are alternately repeated. In radius r _n of the n th zone to the X-ray wavelength λ is approximately, when the relation of r _n ² = nfλ, X transmitted through a transparent zone adjacent
The optical path difference of the line becomes λ (the phase difference is 2π), and they strengthen each other at the light condensing point and serve as a lens. Here, f is a focal length.

As is clear from this equation, the focal length f
Is inversely proportional to wavelength λ, that is, proportional to energy.

[0004]

The element has a characteristic X-ray absorption edge, and the absorption coefficient (or transmittance) differs by about one digit before and after the absorption edge, even with a slight difference in energy. By utilizing this property, it becomes possible to select and analyze only a specific element, thereby enabling precise analysis. However, when the zone plate is used for the light-collecting element, the focal length f varies in inverse proportion to the wavelength λ (proportional to the energy) as shown in the above equation, so that the sample position changes every time the wavelength is changed. There was a problem that it had to be done.

[0005]

The present invention uses two one-dimensional Fresnel zone plates, and adjusts the tilt of the one-dimensional Fresnel zone plate in accordance with the fluctuation of the energy of X-rays to thereby adjust the focal position. To immobilize. As shown in FIG. 1, the two zone plates are arranged orthogonally and are held on a turntable that can freely set an incident angle. They are used for light collection in the horizontal and vertical directions, respectively. In the case of oblique incidence, _assuming that the incident angle is θ (θ = 90 degrees at normal incidence), it can be expressed as rn = (nfλ) ^1/2 / sin θ. As a result, the same focal length f can be obtained.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS For example, a wavelength of 2.3 nm to 4.
X-rays with a wavelength of 4 nm are hardly absorbed by water, but are absorbed by an order of magnitude or more by proteins. By using X-rays in this wavelength range, it is possible to observe the organisms in water and the internal tissues of the organisms including water with high contrast. Further, the wavelength at the absorption edge of carbon is 4.48 nm, but the wavelength is 4.4 nm.
X-rays have a property of being more easily absorbed in carbon by about one digit than X-rays having a wavelength of 4.5 nm. Similarly, the wavelength at the absorption edge of nitrogen is 3.16 nm, and is 3.1 nm to 4.5 nm.
If it is possible to collect and analyze the wavelength range up to one element, the component ratio of carbon and nitrogen can also be analyzed. According to the present invention, the same can be performed for all the elements.

[0007] The zone plate can be manufactured by ultraviolet holographic lithography or electron beam lithography. Ultraviolet holographic lithography is a technique developed at the University of Göttingen in Germany. Two lasers with a wavelength of about 400 nm are used as light sources, and the pattern of the zone plate is directly formed by interference fringes from the lasers, exposing the photoresist. Then, it is a method of manufacturing by reactive ion etching or the like.

[0008] Electron beam lithography is a method most widely used at present for producing an X-ray zone plate. The pattern of the zone plate is scanned with a narrowly focused electron beam to expose a resist such as polymethyl methacrylate. Then, similarly, it is a method of processing by reactive ion etching or the like.

As a material for the zone plate, gold, silver, nickel, tantalum, germanium, or the like is used according to the energy of the X-ray used. The smallest outermost zone width of the zone plate manufactured so far is several tens nm.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Assuming that a target wavelength λ is 4.5 nm and a focal length f is 20 mm in a one-dimensional zone plate, n = 30.
At about 00, the line width becomes about 86 nm. In this case, the size of the entire zone plate is about 1 mm. If nickel is used as the material of the zone plate, in this case 8
A light collection efficiency of about 15% can be obtained with a thickness of about 0 nm. When the wavelength is scanned while tilting this, the focal point is continuously changed while being constant, and the wavelength is 3.1 nm when tilted by 34 degrees.
Met.

[0011]

As described above, the conventional X-ray focusing is performed by a concentric two-dimensional zone plate. In this case, the focal position fluctuates due to the wavelength λ (energy) of the incident X-ray. According to the method of the present invention, it is not necessary to change the focal position even when the wavelength of X-rays changes.

[Brief description of the drawings]

FIG. 1 is a layout diagram of a one-dimensional zone plate of the present invention.

FIG. 2 is a diagram of a conventional disk-shaped Fresnel zone plate.

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Claims (4)

[Claims] 1. An X-ray focusing method using a Fresnel zone plate, wherein two one-dimensional Fresnel zone plates are orthogonally arranged on an X-ray line so that a focal position is fixed. X-ray focusing method. 2. The X-ray focusing method according to claim 1, wherein
An X-ray focusing method, wherein the one-dimensional zone plate is inclined according to the wavelength of incident X-rays. 3. An X-ray condensing apparatus using a Fresnel zone plate, wherein two one-dimensional Fresnel zone plates are orthogonally arranged on an X-ray line, and a focal position is fixed. Light collector. 4. The X-ray focusing apparatus according to claim 3, wherein
An X-ray focusing apparatus wherein the one-dimensional zone plate is tilted according to the wavelength of incident X-rays.