JPH01128000A - Phase zone plate for x-ray microscope for bioobservation - Google Patents

Abstract

PURPOSE:To relieve the restriction on the intensity of a light source and the sensitivity of an image pickup medium and to enable bioobservation with high accuracy and high sensitivity by forming a phase ring band of titanium, vanadium chromium. CONSTITUTION:An X-ray microscope for which a phase zone plate is used is constituted of an X-ray source 4, a condensing phase zone plate 5, a sample holder 6, an objective position zone plate 7, an image pickup device 8 and a vacuum chamber 9. Since the X-rays of a wavelength region used for observation are absorbed by air, the entire part needs be put into the chamber 9 and, therefore, the holder 6 is hermetically closed and a window to allow transmission of X-rays is provided at the time of observing the vital samples which live in liquid. The condensing phase zone plate 5 and the objective phase zone plate 7 are formed of the ring band consisting of the titanium, vanadium or chromium. The bioobservation with the high accuracy and high sensitivity is thereby enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a phase zone grating for a biological observation X-ray microscope. More specifically, this invention
The present invention relates to a phase zone plate for X-ray IAtm that can be used in a wavelength range of 24 to 44 nm and enables high-resolution single-quadrant observation of biological samples.

(Background technology) In academic research such as biology, biochemistry, and biophysics,
In addition, 31 with long legs in recent years! In the development of biotechnology as an industrial technology that is making progress, there is a growing desire to observe the structure and intracellular movement of living biological samples, such as cell samples, at the molecular level and with high resolution. ing.

Conventionally, there are two known methods for observing biological samples: an optical microscope that focuses light using an optical lens, and an electronic mirror that focuses an electron beam using an electromagnetic lens. # In the case of tsl 9M, it is possible to see living biological samples in liquid, but the resolution is low (approximately 0.3 μl) due to the long wavelength of visible light, and in the case of an electron microscope, the resolution is low. However, the problem was that it could not be used for samples containing liquids because the sample had to be placed in a vacuum.

In addition, refrigeration electronic W!, which has recently been under development! In the case of a microscope, the problem is that although it is possible to rapidly freeze a biological sample and see the movement of the frozen specimen, it is not possible to observe the movement within the living body.

On the other hand, X-rays have been used for a long time as a method of so-called X-ray fluoroscopy because there are wavelength ranges depending on the type of material that are absorbed by certain materials and not absorbed by other materials.

Due to the characteristics of these X-rays, it has been considered that they can be used to observe living biological samples. In fact, for example, X-rays in the 24 to 44 wavelength range are absorbed by proteins but not by water, so they may be used to observe living biological samples in water.

However, at present, this has not yet been realized. This is because there are several jm subfocuses left to overcome.

Since X-rays cannot be focused by optical lenses or electromagnetic lenses, a unique focusing system is required, but this focusing system has not yet been developed.

In recent years, concave reflectors (Walter type) and Fresnel zone plates have been used as focusing systems for X-ray microscopes. J! However, a microscope with sufficient resolution has not been realized.

The Fresnel zone plate has attracted attention for its unique method, and will serve as a clue for the development of future X-ray microscopes. That is, as shown in FIG. 6 of the attached drawings, this Fresnel zone plate consists of a ring zone (A) that blocks X-rays and a ring zone (477) that passes through the X-rays, arranged concentrically and alternately. As shown in Figure 6, the radius of the 0-ring zone (A) and (B) becomes narrower toward the periphery so that the X-rays that have passed through the zone (A) gather at one point in the same phase. rl, r2.r3...rn,
....

If r n, then the Fresnel zone plate can be designed such that, for example, the following relationship holds between the wavelength λ of the X-ray and the focal length If.

This Fresnel zone plate has the function of concentrating X-rays at the rear distance f (principal focus) and diverging X-rays around the front distance f, so it can be used as either a convex lens or a concave lens. can.

Furthermore, this Fresnel zone play 1 ~ has distances of 11if/3, f15, ... (f/
(odd number) has a subfocal point.

In such a conventional Fresnel zone plate,
As is clear from Figure 7, which shows the cross section, about 50% of the incident X-rays are blocked, 25% pass straight through without being diffracted, 10% are at the main focus, and 5% are in large numbers. , and the remaining 15% diverges. For this reason, while the condensing efficiency of an optical lens is close to 100%, a Fresnel zone plate has a major drawback in that it focuses only 10% of the X-rays at the principal focus. This drawback requires a strong X-ray source and high sensitivity (LA medium), and its limitations have delayed the development of X-ray microscopy.

In order to overcome the drawback of the Fresnel zone plate's low X-ray focusing ability, a new method called a phase zone plate has been proposed.

In Fig. 7, the reason why a conventional Fresnel zone plate requires a shielding part is if this shielding part
If we consider a path in which the X-rays pass through the transparent part (1) and go to the focal point, the phase of the X-rays is shifted by π radians from the X-rays collected through the transparent part (1), and the intensity at the focal point is weakened by interference. The purpose is to prevent this from happening.

As shown in Fig. 8, when the part corresponding to the shielding part of Fresnel zone play 1- is replaced with a phase ring (O) which is transparent and has the effect of shifting the phase by π radians, The phase shift of π radians caused by the path difference of the X-rays is canceled out, and the phase matches the X-rays passing through the transmission part (1) at the focal point, causing constructive interference. A zone plate with such a configuration is called a phase zone plate.

According to this concept of the phase zone plate, if the phase zone (O) is completely transparent, the X-ray focusing rate is 4.
This will be improved to 0%.

However, in reality, these ideas remain only ideas, and no material has yet been found that is completely transparent to X-rays in the 24-44 wavelength range, which is suitable for observing biological samples. Gold and silver have been proposed as phase zone plates so far.

Copper, carbon, silicon, beryllium, aluminum.

It is made of lithium fluoride, polystyrene, etc., and in fact, there are only reports of phase zone plates for 8 being made using silver.

For this reason, there has been a strong desire to develop a concrete product that takes advantage of the characteristics of the phase zone plate, and in particular, to realize a phase zone plate for biological W4 detection that is effective for X-rays with wavelengths of 24 to 44 degrees.

(Objective of the Invention) The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to overcome the drawbacks of conventional biological observation microscope systems, and to alleviate restrictions on the intensity of the light source and the sensitivity of the imaging medium. ,
High precision, high sensitivity biological observation xi! The purpose of this invention is to provide a new phase zone plate that can be used as a jfi microscope.

(Disclosure of the Invention) In order to achieve the above object, the phase zone plate for biological observation X& of the present invention is characterized in that a phase zone is formed of titanium, vanadium or chromium.

The radius of this phase annular zone is the same as the conventional 7-Renel zone plate, r = ll · f · λ (r7: radius of the annular zone m from the center, f: focal length λ : X-ray wavelength). Further, regarding the thickness, the following relationship holds true. That is, the refractive index n of X-rays is smaller than 1 and varies depending on the wavelength λ. n
can be calculated using the values of the real part f1 and imaginary part f2 of the atomic scattering factor f"fi f2 for each wavelength. When an X-ray passes through a material of J"J length d, the same thickness The phase is d・(1-n)・than when passing through the vacuum of
Since it advances by 2π/λ, the phase ring to make this advance π is derived from π=d・(1−n)・2π/λ and determined by d=λ/2/(1−n) be able to.

In this invention, titanium, vanadium, or chromium is used to form the phase zone due to its characteristics against X-rays and physicochemical stability. Figure 1 shows this. The correlation is shown for titanium (1), vanadium (2) and chromium (3). For example, when titanium (1) is used, a thickness of approximately 1.2 μm is used as the standard for X-ray wavelengths of 24 to 44 μm.
The actual thickness can be determined from the combination with the light collection rate.

FIG. 2 shows the ratio R of light collection efficiency between the phase zone plate of the present invention and the conventional Fresnel zone plate.

Theoretically, this R can also be expressed as follows.

R=(1+'f')2 1''=eXp(-ρ°μmd/2) (ρ: !l!J material density, μ: material ray absorption coefficient T: amplitude transmittance) Such a phase of this invention Regarding zone plates,
The above-described thickness d+concentration ratio R2 and annular radius (r11) may be selected in consideration of the wavelength of the X-rays used, the desired focal length, manufacturing, the limit of L, etc.

For example, X-ray wavelength λ=36, focal length f=1011
I+, number of zones n=8, minimum zone radius r 1 ”Gμ
p, fit outer zone radius rs = 16.97 μr
e, the above R (condensing ratio) is 1 (for T=O1 conventional 7 Renel zone plate), 4 (theoretical phase zone plate, T=1), and R=2.25 ( 'I
Fig. 3 shows the X-ray intensity distribution in the radial direction on the focal plane for three cases where the phase zone grating is 0.5 (an example of phase zone grating).

Furthermore, FIG. 4 shows the X11 intensity distribution on the optical axis. The origin is the zone plate position, and the principal focus is at 10 degrees. The peak of the song is the secondary focus.

Based on such theoretical and practical considerations, the phase zone plate for the XAGM mirror of the present invention is constructed.

FIG. 5 shows an example of the configuration of an X-ray microscope using this phase zone plate.

The example of FIG. It is configured.

Since X-rays in the target wavelength range are absorbed by air, the entire device must be placed inside a vacuum chamber.

For this reason, when observing a biological sample living in a liquid, the sample holder (6) is sealed and has a window that does not allow the X-rays used to pass through.

Further, a passageway that opens to the atmosphere outside the vacuum chamber (9) is provided as necessary.

The focusing phase zone plate (5) and also the objective phase zone plate (7) are formed by rings made of titanium, vanadium or chromium.

(Effects of the Invention) As explained in detail above, the present invention realizes a phase zone plate for use in an X-ray microscope for biological observation with high precision and high sensitivity.

[Brief explanation of the drawing]

FIG. 1 shows the phase zone plate of the present invention.
It is an X-ray wavelength/thickness correlation diagram showing the relationship between the line wavelength and the thickness of the phase ring. FIG. 2 is a light collection ratio/wavelength correlation diagram showing the relationship between the collection ratio and wavelength. FIGS. 3 and 4 are intensity correlation diagrams showing the relationship between X-ray intensity, radius from the optical axis in the principal focal plane, and distance from the on-axis zone plate, respectively. FIG. 5 is a cross-sectional view showing an example of the configuration of the X4-enabled GM of the present invention. FIG. 6 is a pressure surface view of a conventional Fresnel zone plate. FIG. 7 shows its sectional view. FIG. 8 is a 1tli plane view of the phase zone plate. DESCRIPTION OF SYMBOLS 1... Titanium, 2... Vanadium, 3... Chromium, 4... X-ray source, 5... Focusing phase zone grating, 6... Sample holder, 7... Objective phase zone Plate, 8... Imager, 9... Vacuum chamber. Agent Patent Attorney Toshio Nishizawa No. 6
Drawing procedure amendment (voluntary) Chairman Nobuhisa Akabane “Detailed description of the invention” section of the specification

Claims (1)

[Claims] (1) A phase zone plate for a biological observation X-ray microscope, characterized in that a phase ring is formed using titanium, vanadium, or chromium.