RU2239822C2 - X-ray microscope - Google Patents

Abstract

FIELD: roentgen technology for microscopes.

SUBSTANCE: proposed X-ray microscope has long X-ray source, means for disposing subject of inquiry 3, as well as recording means, and X-ray capillary lens inserted in-between. Channels of the latter run toward recording means. Means for disposing subject of inquiry is mounted between long X-ray source and smaller butt-end of X-ray capillary lens. Device is characterized in that walls of X-ray transport channels 14, 16 are covered with or made of material absorbing or dissipating X-rays and their side surfaces are made in the form of truncated cone or pyramid, or cylinder, or prism. Such material provides for eliminating full external reflection, and rectilinear longitudinal channels ensure their operation as collimators. Therefore these channels entrap only rays from fragments of subject of inquiry 3 occurring precisely opposite their inputs. As compared with prior art, provision is made to avoid entrapping ray entering channel 18 at angle ranging between 0 and critical full external reflection angle θ _c . That is why resolving power fully depends on capabilities of reducing input dimensions of channel.

EFFECT: reduced exposure time and power requirement of roentgen tube.

1 cl, 6 dwg

Description

Technical field

The invention relates to projection microscopy using radiation methods, and more particularly to means for obtaining an increased shadow projection of an object, including its internal structure, using x-ray radiation.

State of the art

Known x-ray microscope, which allows you to get an image of the internal structure of objects. The action of such a microscope is based on the principle of shadow projection of an object in a diverging beam of x-rays emitted by a point source (Encyclopedic Dictionary “Electronics”, Moscow, Soviet Encyclopedia, 1991, p. 478 [1]). This microscope is called a shadow or projection. A projection microscope usually contains a microfocus x-ray tube, a camera for placement of the studied object and recording means. The resolution of the projection x-ray microscope is the higher, the smaller the size of the radiation source and the distance from it to the object. It is known, in particular, to use x-ray tubes in such microscopes with a focal spot of 0.1-1 μm in diameter [1]. To further reduce the effective source size, aperture is used (Physical Encyclopedic Dictionary, Moscow, Soviet Encyclopedia, 1984, p.639 [2]).

However, with a decrease in the size of the source or with aperture, its intensity becomes insufficient to obtain acceptable contrast of the enlarged image. Overcoming this drawback requires a significant increase in exposure time. Increasing the size of the source to increase its effective intensity leads to blurring of the resulting image and a decrease in resolution.

With the creation of x-ray capillary optics of total external reflection, it became possible to use extended (comparable with the object under study) x-ray sources in x-ray microscopes. In such microscopes, a camera with an object to be studied is placed between an extended x-ray source and the input end of the x-ray lens with channels diverging towards the means for recording the image (international application PCT / RU 94/00189, international publication WO 96/01991 of 01.25.96 [3] ) Specifically, the specified source describes the use of conical x-ray lenses and lenses in the form of a bell, and noted the higher efficiency of the latter. An increase in the size of the source does not affect the resolution of these microscopes, since it corresponds to the size of a fragment of an object falling into the field of view of an individual channel of an x-ray capillary lens. An x-ray microscope of this design is the closest to the offer.

However, with a decrease in the diameter of individual channels to the level achieved with modern technologies in monolithic and, in particular, in integral lenses (US patent No. 6271534, published 07.08.2001 [4]), the size of the inlet of a separate channel of the x-ray lens ceases to be a determining factor . This is because the size Δ of the aforementioned field of view of an individual channel of the lens is of the order

where d is the input diameter of an individual channel,

L is the distance between the investigated object and the input channel of the x-ray lens,

θ _c is the critical angle of total external reflection from the material of the channel walls.

For small diameters d and low radiation energies used, in particular, in the study of biological objects, when the angle θ _c can reach 10 ^-2 radians, the second term in the above expression (1) becomes dominant. So, for example, with L = 1 mm and d = 0.1 microns, we have

d = 0.1 micron = 10 ^-7 m << 2 · 10 ^-5 m = 2 · l · 10 ^-3 m · 10 ^-2 = 2Lθ _c .

As a result, the improvement of the technology for manufacturing X-ray lenses does not allow to increase the accuracy of X-ray microscopes of the described known design using extended sources.

Disclosure of invention

The present invention is aimed at obtaining a technical result, which consists in increasing the resolution of a projection microscope using x-ray radiation by reducing the diameter of the channels of the used capillary lens while maintaining the possibility of using an extended (including exceeding the size of the studied object) source while eliminating the dependence of resolution on energy of radiation used. The indicated types of technical result are combined with a short exposure time.

To achieve this technical result, the proposed x-ray microscope, as described above, closest to it, known from the patent [3], contains an extended x-ray source, as well as means for placing the object under study and means for recording and an x-ray capillary lens located between them, having radiation transmission channels diverging towards the means for recording. In this case, a means for placing the object under study is installed between an extended x-ray source and the input (smaller) end of the x-ray capillary lens.

Unlike the closest known device in the proposed X-ray microscope, the walls of the channels of the X-ray capillary lens are internally coated or made of a material that absorbs or scatters X-ray radiation to exclude the phenomenon of total external reflection and have the form of either a side surface of a truncated cone or pyramid or cylinder or prisms.

In the first two named forms of the surface shape of the walls of the radiation transport channels, their cross section evenly increases in the direction from the entrance to the output, and in the last two it remains constant along the length of the channel. It is important that in all these cases, the optical axis of the channels are straightforward. The implementation of the walls of the channels for transporting radiation from a material that absorbs or scatters X-ray radiation, or coating them from the inside with such material ensures the absence of reflection of radiation when it passes through the channels. As a result of this, the channels operate on the principle of collimators and it is impossible to capture radiation, which upon further propagation in the channel will meet the wall. As a result, each channel can only capture radiation that has passed through a fragment of the object under study, located exactly opposite the entrance of this channel. Therefore, the size of the field of view of an individual channel is determined by formula (1) without the second term on the right side.

Brief Description of the Drawings

The invention and the invention are illustrated by drawings, which show:

figure 1 - General layout of the nodes of the x-ray microscope;

figure 2 - implementation is part of the x-ray microscope lenses with diverging channels for transporting radiation, with increasing cross-section towards the exit side;

figure 3 - the implementation is part of the x-ray microscope lenses with diverging channels for transporting radiation, having a constant cross-sectional length;

figure 4 is a cross-sectional view of the lens in the case corresponding to figure 2, with two forms of walls of the channels for transporting radiation;

figure 5 is a cross-sectional view of the lens in the case corresponding to figure 3, with two forms of the walls of the channels for transporting radiation;

figure 6 - field of view of individual channels of the lens and the propagation path of the quanta of x-ray radiation in the channels of the proposed and known devices.

Embodiments of the invention

The proposed x-ray microscope contains (Fig. 1) an x-ray source 1 with an extended aperture 2, which is no less than the size of the test object 3. The latter is in the tool (chamber 4) for placing the test object. In the closest proximity to this tool is the input (smaller) end face 5 of the X-ray capillary lens 6. Near the output (larger) end 7 there is an X-ray sensitive instrument 8 for registration. The picture 9 of the distribution of the density of x-ray radiation registered through this object 3 and transferred by the lens 6 from its input end 5 to the output 7 registered by this means is reproduced by the monitor 10. In this case, the linear dimensions of the image of the object 3 increase in proportion to the ratio of the linear sizes of the output 7 and input 5 the ends of the lens 6.

Previously, the output signals of the means 8 for registration can be processed in a personal computer or specialized computing tool 11 provided with a control unit 11a. So, for example, in the tool 11, a picture can be fixed in the absence of the studied object 3, reflecting the unevenness of the radiation intensity over the aperture 2 and the unevenness of its losses when passing through the walls of the camera 4, the lens 6, as well as the uneven sensitivity of the detecting elements over the area of the means 8 for recording 9. In the future, when observing the investigated object, this previously fixed picture can be used to correct the resulting image so that it reflects only the uneven density of the investigated object. Due to this, in the picture 9 on the screen of the monitor 10, images 12 of heterogeneities 13 of the internal structure of the object 3 are correctly represented.

The actual function of lens 6 is to divide the shadow image of object 3 at the input end of lens 6 into elements according to the number of lens channels and transport each of these elements (in the form of the corresponding x-ray radiation transmitted through a particular fragment of object 3) to the corresponding detecting element funds 8 for registration. A resolution equal to the input diameter of the lens channels can be realized if the output signal of each of the lens channels can be fixed separately, without “mixing” with the output signals of other channels. Therefore, the aforementioned magnification should correspond to the size of the resolution element (individual detecting element) of the registration means 8.

Ensuring such a correspondence does not necessarily require an actual increase in the size of the image element at the output of the lens 7 compared with the size at the input. It is enough to realize the mentioned possibility of separate reception of signals corresponding to each of the image elements. This condition can be fulfilled in any of the lens designs shown in FIGS. 2 and 3.

In the first of them (figure 2), the channels 14 fill almost the entire volume of the lens, changing their cross section along the length according to the same law as the cross section of the lens as a whole. The channels in the lens construction of FIG. 2 may take the form of, in particular, a circular cone or a hexagonal pyramid. Their cross section is shown in figure 4. This form is the most technologically advanced. The ratio of the output D and input d diameters (with a round cross-sectional shape) determines the mentioned degree of increase. In order for the potential resolution to be realized, the sizes of the sensitive detecting elements of the registration means 8 should be no more than D, and they should be located opposite the outputs of the lens channels. Figure 2 shows several of these elements 15. The same condition must be satisfied when using the lens shown in figure 3, in which the cross section of the channels 16 is constant in length and their output diameter is equal to the input diameter d. Several detecting elements 17 satisfying this condition are also shown in FIG. 3. The most technologically advanced channel shapes in the lens design of FIG. 3 are a circular cylinder and a hexagonal prism. Their cross section is shown in figure 5.

The gaps between the radiation transport channels must be opaque to the x-ray radiation (otherwise they would also have to be considered as “channels”).

The design of FIG. 2 is energetically somewhat more advantageous. Perceiving radiation from the same size fragment of the object as in the construction of FIG. 3, and providing approximately the same resolution, it allows you to capture most of the radiation of this fragment due to the expanding nature of the channels.

In both structures, radiation can only be captured from points of fragments of the object located strictly in areas bounded by channel extensions (see Figs. 6a and 6c). Due to the proposed selection of the material of the channel walls or the material of their coating, radiation entering the channel at an angle to its wall is absorbed or scattered and does not pass to the exit. 6a and 6c, dashed lines show the propagation paths of X-ray quanta passing to the channel output, which can only be rectilinear. In contrast, in the known device [3], using the principle of total external reflection, radiation propagating through the channels 18 can also be transmitted to the channel inputs from fragments of the object located outside the zones shown in figa and 6b (see Fig. .6s). This can occur if the direction of radiation propagation at the entrance to the channel forms an angle less than critical θ _s with its walls. Therefore, as shown in Fig. 6c, quanta propagate along the channel along straight lines (shown by dashed lines) and along broken lines (shown by solid lines).

In the experiments, the image of the object was obtained with a resolution of the order of 1 micron with a source with linear dimensions of the order of 0.1 mm, i.e. the area of the source aperture exceeded the resolution element by about 10,000 times. There are all prerequisites for obtaining in the future a resolution of 0.1 microns or better.

An essential factor determining the prospects for the practical application of the proposed microscope is the speed of obtaining information. According to estimates, it can be (10-100) thousand times higher than when using the conventional method of projection x-ray microscopy.

This gain is achieved by removing the restriction on the intensity of the source used. Since it does not have to be microfocus and can have finite dimensions, a high effective intensity is achievable even at low powers of the x-ray tube.

The above examples relate to a tube with a power of less than 10 W and a conical x-ray lens with a number of channels of the order of 10 ⁶ .

Industrial applicability

The proposed device can be implemented in practice in any of the many possible options described, allowing the choice of both the lens design and the specific shape of the channels, depending on technological capabilities and other grounds for certain preferences.

Confirmed in the experiment, the indicators can rely on the widespread use of the proposed X-ray microscope both directly in industry, in particular in microtechnologies, and in scientific research, primarily in biology and medicine.

All of the above, concerning the principles of construction and the achieved result, is equally applicable to microscopes using other types of radiation in the form of a stream of neutral particles, in particular neutrons, gamma rays, ultraviolet and infrared radiation, visible light, and radiation in the form of a stream charged particles, such as ions.

Claims (1)

An X-ray microscope containing an extended X-ray source (1), as well as a means (4) for placing an object under investigation (3) and a means (8) for recording and an X-ray capillary lens (7) located between them, having radiation conveying channels diverging to the side means (8) for recording, while means (4) for placing the test object is installed between an extended x-ray source (1) and a smaller end face (5) of the x-ray capillary lens (7), characterized in that the channel walls (14, 16) are conveyor irovki radiation ray capillary lens (1) made of or coated with material that provides exception total reflection phenomenon, and have the shape of a side surface or a truncated cone or pyramid or of a cylinder or prism.

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