WO1990006582A1

WO1990006582A1 - Structure for influencing the effect of x-ray or gamma radiation on a target sensitive to the radiation

Info

Publication number: WO1990006582A1
Application number: PCT/HU1989/000058
Authority: WO
Inventors: Péter Teleki
Original assignee: Teleki Peter
Priority date: 1988-11-28
Filing date: 1989-11-28
Publication date: 1990-06-14
Also published as: AU4633189A; KR900702537A; JPH03502489A; EP0400125A1; BR8907213A

Abstract

The present invention refers to a structure for influencing the effect of X-ray or gamma radiation on a target sensitive to the radiation (R), having a first and a second side, the X-ray or gamma radiation (R) striking the first side, the structure comprising at least one group of layers (1, 3, 5, 7) emitting a secondary radiation under the influence of the X-ray or gamma radiation (R) or the secondary radiation of layers (1, 3, 5, 7) arranged behind the first side in the way of propagation of the X-ray or gamma radiation (R). The essence of the invention lies comprising in the group at least a basic layer (1) and a second (3) layer arranged in a sequence of the atomic numbers of elements forming the layers (1, 3, 5, 7), wherein the basic layer is made of a metal selected from the group consisting of 28Pb, 74W and 73Ta, the second layer of a metal selected from the group consisting of 47Ag, 42Mo, 41Nb, 29Cu, 28Ni, 23V and 13Al.

Description

STRUCTURE FOR INFLUENCING THE EFFECT OF X-RAY OR GAMMA RADIATION ON A TARGET SENSITIVE TO THE RADIATION

FIELD OF THE INVENTION

The present invention .refers to a laminar structure for influencing the effect of X-ray or gamma radiation on a target sensitive to the radiation which comprises at least two groups of layers wherein each group of layers emits a secondary radiation under the influence of the X-ray or gamma radiation or the secondary radiation of the previous layers. The structure proposed by the invention is capable of improving quality of a picture received by the means of the radiation and it can be applied also for securing protection of increased safety level against X-ray and gamma radiation. BACKGROUND OF THE INVENTION

A method and a modifying body for influencing the effect of X-ray or gamma radiation on a target sensitive to the given kind of radiation and in particular for selective modification of a radiograph of an object is known from the U.S. Patent Document 4764946 (granted to P. Teleki in August 1988), wherein the effect of the X-ray or gamma radiation is proposed to be influenced by the means of a structure comprising at least two layer groups intended to modify the energy spectrum of the radiation in order to ensure increased level of excitation in a substance sensitive to radiation, e.g. in an AgBr layer prepared for making X-ray radiographs. The layer groups include different metals, especially antimony (₅₁Sb) and strontium

(₃₈Sr). The method and modifying body disclosed in the mentioned U.S. patent specification offers a very simple solution for improving the conditions of preparing X-ray radiographs especially in industrial applications. The metals forming the layer groups ensure a gradual energy transposition from one layer to the other by excitation. In this method the energy transposition is the basis of improving the quality of the received radiographs.

The reflection of the beams constituting X-ray or gamma radiation is a problem difficult to solve. In the last decade the investigations have been directed to creating thin layer systems capable of applying in image forming processes. The known X-ray mirrors include a plurality of thin film layers, e.g. about 80 to 100 layers made alternatively of tungsten and carbon. The thickness of the layers in the systems which have become known is comparable with the wavelength of radiation applied. However, the level of the scattered radiation is relatively high what results in the fact that the quality of the visible radiographs received is rather poor.

In the radiology a further problem arises from the fact that both X-ray and gamma radiation require applying different kinds of shield structures for securing protection of human beings and goods against radiation. The shields proposed according to the background art are relatively heavy and complicated, they consist of heavy structural elements.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a more layer structure for influencing the effect of X-ray or gairma radiation, in particular for improving the quality of pictures received by the means of radiography and/or for increasing the safety level of means ensuring protection against the mentioned kinds of radiation.

The invention is based on the recognition that the thin layer structures can be applied for controlled scattering the radiation. This means, depending on the composition the structure can be applied for absorbing radiation and simultaneously or only for reflecting radiation in a manner which results in improved quality of the radiographs.

It is known that on the boundary surface consisted of layers built-up from ideal crystals the X-ray or gamma radiation is scattered. It is also known that the primary back- scatter phenomenon of extinction results in improved conditions of scattering and in absorbing radiation having relatively low energy. In a system comprising many reflecting layers the Compton effect shows also changes in a series of interactions, the radiation becomes softer (its energy decreases) and this is advantageous in protecting systems. The intensive scattering process is also preferred in protecting structures having thickness exceeding a minimal value because of ensuring a longer way for the propagation of the radiation in the material of the structure; this results in improved absorption conditions. The mechanism shown here can be influenced by doping the material, by controlling the crystallization process thereof.

Hence, the invention refers to a laminar structure for influencing the effect of X-ray or gamma radiation on a target sensitive to the radiation which comprises at least one group of layers wherein the only one or each group of layers emits a secondary radiation under the influence of the primary X-ray or gamma radiation or the secondary radiation of the previous layers. The essence of the invention is to provide a structure including the layers in at least one group, the layers being arrranged in a predetermined space sequence which can be symmetric with regard to basic materials applied. The predetermination means that the layers are arranged in the sequence of the atomic numbers of the elements constituting them, if a reflecting system is required. The layer system to be applied for reflecting X-ray or gamma radiation should consist of at least 32 layers with preferred thickness in the range from 0.0001 to 0.01 mm, wherein the value range from about 0.001 mm to about 0.002 mm is especially advantageous.

The group of the layers should include at least one layer made of ₈₂Ph (lead), ₇₄W (tungsten) or ₇₃Ta (tantalum) and the further layers can be made from at least one of the following metals:

first group associated with ₂₈Pb

₄₇Ag (silver), ₂₉Cu (copper), ₂₈Ni (nickel),

1₃Al (aluminium)

second group associated with ₇₂W and ₇₃Ta

4₂Mo (molybdenum), ₄₁Nb (niobium), ₂₃V (vanadium) The elements of the first group are characterized with crystalline lattice built-up according to the face-centered system (FCC) and those of the second group with lattice of body-centered system (BCC). If the proposed structure is intended to ensure reflexion of X-ray or gamma radiation it is important to prepare the layers with homogeneous distribution of their material having as low density of dislocations and level of contamination as possible.

The structure proposed by the invention, if contaminated and includes dislocations may be applied also for increasing the safety level of protecting systems applied in an environment of X-ray or gamma radiation and this effect is increased by applying before the layers defined above and/or between two of them an iron based body made of iron including at least four of the following additives: ₁₅P, ₁₆S, ₂₇Co, ₃₉Y and ₄₀Yr. Iron completed with the mentioned additives and the physical and chemical contamination of the crystalline lattice, i.e. the dislocations and the strange atoms exert intensive scattering effect on X-ray or gamm a radiation entering the structure and the scattered beams of radiation can be absorbed or reflected by the structure more intensively than the beams entering directly. The dislocations and the strange atoms constitute centers of the scattering process. The proposed structure can be equipped with a protective layer arranged on the outer surface (on the first side striked by radiation), the protective layer being comprised of ₂₄Cr or another substance showing high resistance against different corrosive and other dangerous factors.

The structure built-up according to the invention can be applied in the cosmic space and in normal gravity conditions. It constitutes a system of relatively low density which can be easily realized.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described in more detail on the basis of preferred embodiments and with reference to the attached drawings showing layers and layer systems not according to the real scale, for the sake of visibility. In the drawings

FIG. 1 is a schematical view of a two-layer basic embodiment of the structure proposed by the invention, the structure advantageously being equipped with a scattering layer

FIG. 2 is a schematical view of another basic embodiment of the structure proposed by the invention comprising more (e.g. ten) layers in a symmetric arrangement

FIG. 3 is a schematrical view of a preferred arrangement of the layers of the structure proposed by the invention, the structure beg divided into subsystems of layers and

FIG. 4 is a further schematical view of another preferred arrangement of the layers constituting a relatively sophisticated part of a structure proposed by the invention. BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

The structure for influencing the effect of X-ray or gamma radiation on a target sensitive to the radiation consists of layers of equal or different thicknesses. The target arranged in the way of the reflected radiation produced by the structure proposed by the invention from primary radiation R is not shown in the drawings. The target can be a film being sensitive to X-ray or gamma radiation or a screen or any image-sensing means, e.g. Nal or Csl crystal detector doped by T1. The structure of the invention can be applied also, if the components allow to do so, for preparing a screen or shield protecting the environment against the X-ray or gamma radiation.

The structure of the invention is consisted of a basic layer 1 and at least a second layer 3 (Fig. 1). The basic layer 1 is made of ooPb or ₇₄W or ₇₃Ta and the second layer 3 consists of any one of ₄₇Ag, ₂₉Cu, ₂₈Ni or ₁₃Al (metals associated generally with ₈₂Pb), ₄₂Mo, ₄₁Nb or ₂₃V (associated with ₇₄W and ₇₃Ta). The basic layer 1 is arranged either as the first in the way of radiation R after a scattering layer 2 (Fig. 1) and/or a covering layer 4 which will be described later or in the middle part of a symnetric layer system.

The basic layer 1 is followed (Fig. 1) or preceded and followed (Fig. 2) by the second layer 3 and if necessary, by third, fourth and fifth layers 5, 7, 9 consisting of the other elements listed up above. The elements are arranged always in a sequence according to their increasing (structure as shown in Fig. 2) or decreasing (structure as shown in Fig. 1) atomic numbers given in the above lists, too. In a more layer system the second layer may be consisted of ₇₃Ta, too.

According to the invention the basic and further layers 1, 3, 5, 7, 9 of a reflecting system are made of metals crystallizing in the face-centered crystalline lattice (FCC) and/ /or in the body-centered crystalline lattice (BCC), characte rized with only one lattice constant.

The elements are the following:

In the structures comprising more layers than five the arrangement is built-up from symmetric pieces including the basic layer(s) 1 in the middle part (Fig. 3 and 4). The number of the layers is advantageously at least thirty-two, between two layers it is preferred to prepare separating layers 6 consisted of an appropriate oxide, having thickness not exceeding about 0.0001 mm.

The invention renders possible to create material systems showing double effect. If the layers 1, 3, 5, 7, 9 consist of a substance characterized by crystalline disorder, relatively high density of dislocations and/or prepared with selected alloying components or additives, they cause intensive scattering effect with backscatter phenomenon, i.e. scattering effect acting backwards practically without any remarkable order. The dislocations, the surface of the grains comprising the strange atoms consitute the centers of scattering. It is therefore advantageous to apply such layers 1, 3, 5, 7, 9 together with those prepared of pure material having low density of dislocations which act together as an active system reflecting the radiation.

The scattering (protecting) layers 2 can include also the metals listed above. It is also advantageous to apply iron (₂₆Fe) for the basic material of a such layer, wherein iron comprises at least four of the following alloying components, additives and elements: ₃₉Y, ₄₀Zr, ₂₇Co, ₁₅P , ₁₆S. The thickness of the scattering layer 2 is not limited, however, it is proposed to prepare it with thickness lower than that of the basic and further layers 1, 3, 5, 7, 9 of a reflecting system. Because of high thermal resistivity, the scattering layer 2 can be applied for covering X-ray tubes.

The scattering layer 2 is arranged either on the surface of the structure directed to the source of radiation R or in its depth, between two layers 1, 3, 5, 7, 9 of a reflecting system.

The outer surface of the structure can be made with a covering layer 4 consisted of any material of required characteristics, e.g. of ₂₄Cr which is advantageous because of excellent heat and light reflecting features, high corrosion resistivity, etc.

The basic and further layers 1, 3, 5, 7, 9 of reflecting capability are arranged in a sequence following that of the atomic numbers, because this is very advantageous with regard to the absorption processes: the characteristic radiation is absorbed in the adjacent metal layer. The radiation scattered and backscattered by the basic and further layers 1, 3, 5, 7, 9 is also intensively absorbed by the structure if the basic layer 1 is arranged in the middle part and the second and further layers 3, 5, 7, 9 constitute in both directions a symmetric system. The other and preferred possibility is to arrange the basic layer 1 consisted of the first metal in the FCC or BCC group (see Table 1.) or of ₇₃Ta as first to receive the primary radiation.

It is especially preferred to prepare the structure from at least three metals, e.g. in the following arrangements given only by way of example and, for the sake of simplicity, without the atomic numbers: Pb , Ag , Al , Al , Ag , Pb , Ag , Al

Pb , Cu , Al , Al , Cu , Pb , Cu , Al

W, Mo , V, V, Mo , W, Mo , V

W, Nb , V, V, Nb , W, Nb , V

Ta, Mo , V, V, Mo , Ta, Mo , V

Pb, Mo , V, V, Mo , Pb , Mc , V

W, Cu, Al , Al , Cu, W, Cu, Al

Of course, other arrangements can be selected, too.

The scattering layer 2 is generally applied between the source of the radiation R and the basic and further layers 1, 3, 5, 7, 9 of the reflecting system, it consists of iron and the additives mentioned above. Of course, the normal contaminating elements of iron, as silicon or carbon, etc. are always present, they can not be exluded.

The structure of the invention preferably consists of thirty-two layers, consisting of two- and three-component subsystems. The examples of the last are given above. Some examples of the two-components systems:

Pb, Al, Al, Pb, Al

W, Al, Al, W, Al

Ta, V, V, Ta, V etc.

It is also preferred to apply a high heat and corrosion resistance layer made of e.g. ₂₄Cr between the two- and more- -layer subsystems.

The basic and further layers 1, 3, 5, 7, 9 of the structure proposed by the invention have thickness in the range from 0.0001 to 0.002 mm, however, the lower and higher values in the range from 0.0001 to 0.01 mm or more may be also selected, if required.

The scattering layer 2 can be thicker than the basic and further layers 1, 3, 5, 7, 9, but generally it should be not thicker than the reflecting system built-up with the basic and further layers 1, 3, 5, 7, 9.

The structure realized according to the present inven tion results in remarkable improvement of the quality of radiographs, i.e. pictures registered by the radiologic means. It can simultaneously constitute a high effectivity shield securing protection against X-ray and gamma radiation showing high resistivity against chemical substances and thermal effects. The shield can be produced in form of plate-like elements of high elasticity, too.

The layers can generally be made by known techniques of preparing thin layers, e.g. by vapour deposition, however, the thicker layers can be prepared by rolling and united by the means of an adhesive and/or the oxide layers.

The main advantage of the proposed structure is the possibility of double use.

Claims

CLAIMS: 1. A structure for influencing the effect of X-ray or gamma radiation on a target sensitive to the radiation, having a first and a second side, wherein said X-ray or gaimia radiation strikes said first side, said structure comprising at least one group of layers emitting a secondary radiation under the influence of said X-ray or gamma radiation or the secondary radiation generated by layers arranged behind said first side in the way of propagation of said X-ray or gamma radiation,

characterized in

comprising in said group at least a basic layer and a second layer arranged in a sequence of atomic numbers of elements forming said layers, wherein said basic layer is made of a metal selected from the group consisted of lead (₈₂Pb), tungsten (₇₄W) and tantalum (₇₃Ta), and said second layer of a metal selected from the group consisted of silver (₄₇Ag), molybdenum (₄₂Mo), niobium (₄₁Nb), copper (₂₉Cu), nickel (₂₈Ni), vanadium (₂₃V) and aluminium (₁₃Al).

2. The structure as set forth in claim 1,

characterized in

comprising said second layer made of a metal selected from the group consisted of ₂₃V and ₁₃Al.

3. The structure as set forth in claim 1,

characterized in

comprising at least two groups of layers, said groups of layers including a symmetric arrangement of said layers with regard to said basic layer.

4. The structure as set forth in claim 1,

characterized in

symmetry of said groups of layers with regard to the material of said layers.

5. The structure as set forth in claim 1,

characterized in

comprising a group of layers comprising said basic layer at said first side, said group of layer including in sequence of the atomic numbers said basic layer and at least two further layers made of different elements selected from at least one of the first and second subgroups, said first subgroup including elements ₄₇Ag, ₂₉Cu, ₂₈Ni and _{1 3} Al, said second subgroup including elements ₄₂Mo, ₄₁Nb and ₂₃V and additionally ₇₃Ta if said basic layer consists of ₇₄W.

6. The structure as set forth in claim 1,

characterized in

consisting of thirty-two layers divided into groups of layers comprising layer systems made with basic and further layers prepared from two or three metals selected from said group of metals, wherein the layers form subroups having symmetric arrangement with said basic layers with regard to the material of said layers.

7. The structure as set forth in any of claims 1 to 6, characterized in

comprising a scattering layer arranged on said first side or between said first side and the layer limiting said structure from second side, said scattering layer comprised of iron including at least four elements from the group consisted of the ₁₅P, ₁₆S, ₂₇Co, ₃₉Y and ₄₀Yr.

8. The structure as set forth in claim 7,

characterized in

that at least one of at least one group of layers and said scattering layer is made of a material featured by high density of dislocations, said layers of said group including at least one or more kind of strange atoms forming grains scattering said X-ray or gamma radiation.

9. The structure as set forth in any of claims 1 to 8, characterized in

including a covering layer on said first side, said covering layer being made of ₂₄Cr.

10. The structure as set forth in any of claims 1 to 8, characterized in

including a covering layer between two layers belonging to two different groups of layers, said covering layer being made of

24^Cr.

11. The structure as set forth in any precedent claim, characterized in

including separating layers between the layers of at least one of said groups, said separating layers comprising at least one oxide.