METHOD AND MODIFYING BODY FOR INFLUENCING THE EFFECT OF X-RAY OR GAMA RADIATION ON A TARGET SENSITIVE TO THE RADIATION

Abstract: Method and modifying body for influencing the effect of X-ray or gamma radiation on a target (7) sensitive to radiation, in particular for selective modification of a radiograph of an object (10). According to the invention a modifying body comprising at least two layer groups (31, ...3n) is arranged in front of the target (7), wherein each layer group (e.g. 32) emits a secondary radiation under the influence of the X-ray or gamma radiation or the secondary radiation of the previous layer group (e.g. 31), respectively, the energy of which is lying above the absorption energy level defined by the electron shell K of an element being present in the following layer group (e.g. 33) or in the target (7) arranged behind the last layer group (3n), respectively.

Description: METHOD AND MODIFYING BODY FOR INFLUENCING THE EFFECT OF X-RAY OR GAMMA RADIATION ON A TARGET SENSITIVE TO THE RADIATION Technical field The invention relates to a method for influencing the effect of X-ray or gamma radiation on a target sensitive to the radiation , preferably for selective modification of an image of an object formed 5 on a target by X-ray or gamma radiation, as well as to a modiiying body for implementing the method according to the invention. Background art For producing radiographs amplifying foils are known which convert the incident X-ray radiation into a radiation falling in the 10 range of the visible light. In general , these amplifying foils used to be arranged before and behind the film to be shot. In this case blackening of the film is primarily caused by the radiation falling into the visible range . Application of amplifying foils enables reduction of exposure time however, it is accompanied by the deterior tion of the sharpness of - a the image . From the PCT Application PCT /HU 83/00062 published under the number WO 84-/02399 a method for producing radiographs is known, in which a modifying body of laminar structure is placed between the object to be examined and the film. The modifying body consists of 2o thin. Pb layers arranged on one another, which are applied onto a carrier sheet .If in the object examined material thickness correspond- ing to different ray paths is changing, e . g. the object is a pipe , the modifying body automatically acts as a compensator. In such a manner, on the image thus obtained far more details of the object can be seen and evaluated, however , the exposure times have to be increased. In radiologic practice materials of the films used for preparing radiographs respond only to an X-ray or gamma radiation, the energy of which surpasses a given limit of energy level. In general , sensitivity is the highest immediately above said energy level, thereafter with increasing energy it drops consider ably. Just in order to eliminate this dependency on energy, sensitivity of usual films used to be modified by means of filters so as to achieve nearly equal sensitivity in a broader range of energy. This , however, in¬ volves a poor sensitivity of the film in the whole energy range , requiring an increased radiation intensity or a longer exposure time in course of preparing radiographs . Disclosure of invention The aim of the invention was to develop a method and means , by the aid of which an image formed by X-ray or gamme radiatio can be advantageously influenced so that quality of the image could be improved without prolongating the exposure time , and if possible , even with a shorter exposure period. Accordingly, the invention relates to a method for influenc¬ ing the effect of X-ray or gamma radiation on a target sensitive to the radiation, preferably for selective modification of an image of an object formed on a target by X-ray or gamma radiation, in the course of which a modifying body having laminar structure is arranged in front of the target in the path of the radiation beam. The improve¬ ment according to the invention is that in front of the target at least two layer groups are disposed, each of said layer groups comprises a plurality of superimposed layers emitting a secondary radiation under the influence of the primary radiation or the secondary radiation of the previous layer group, respectively, the energy of which is lying above the absorption energy level defined by the electron shell K of an element being present in the following layer group or in the target arranged behind the last layer group, respec¬ tively. By proper selection of the material of said layer groups it can be achieved that at least a part of the primary X-ray or gamma radiation is converted gradually within the layer groups into a radiation with an energy range in which the sensitivity of the target is maximal. By the better utilization of the target a reduction of exposure time becomes possible. The target can be a film being sen¬ sitive to X-ray or gamma radiation or a screen or any image- sensing means, e. g. a Nal or Csl crystal detector doped by Tl. It has also been recognized that it can be advantageous , if a layer group is disposed in front of the target, with which the energy of the secondary radiation emitted by said layer group is lying betwee the absorption energy level and the emission energy level defined by the electron shell K of an element being present in the following layer group or in the target. By means of this secondary radiation the following layer group or the target can be quasi pre -excited, accordingly, it will be more sensitive to the radiation with an energy lying above the absorption energy level. In accordance with the invention material and location of the layer groups are to be selected expediently so that when progress ing "in direction to the target, the successive layer groups should contain elements with ever decreasing atomic numbers. Sharpness of the radiograph thus obtained can be increas- ed if at the layer groups an electric field with a direction corres¬ ponding or opposite to the radiation beam is generated , e. g. so, that a proper voltage is applied onto the insulated Al layers formed on the two extreme boundary surfaces of the layer groups lying above one another. In such a manner electrons generated by the X-ray or gamma radiation can be well controlled. For absorbing scattered radiation arriving from the object to be examined and from the environment it is expedient to dispose Pb layers between the object tested and the first layer group facing the object. In order to absorb re-scattered radiation it can be ad¬ vantageous to dispose Pb layers lying on one another behind the target. The invention also relates to a modifying body for in- fluencing the effect of X-ray or gamma radiation on a target sensitive to such radiations, said modifying body comprises a plurality of superimposed layers . The modifying body according to the invention comprises at least two superimposed layer groups, each layer group comprising a plurality of superimposed layers containing an element which emits a secondary radiation under the influence of the X-ray or gamma radiation or the secondary radiation of the previous layer group, respectively, the energy of which is lying above the absorption energy level defined by the electron shell K of an element being present in the following layer group or in the target, respectively. It is considered as advantageous for the sake of the afore¬ mentioned pre -excitation that the modifying body comprises a layer group which contains an element emitting a secondary radiation, the energy of which is lying between the absorption energy level and the emission energy level defined by the electron shell K of an element being present in the following layer group or in the target, respectively. Advantageously, layer thickness in the modifying body according to the invention is less than 100 um, expediently less than 30 um ' . Most advantageously the thickness lies in the range betwe 0, 1 and 10 u , in this case namely the radiation is compelled to travel through a plurality of boundary surfaces, which involves an increased probability of interactions and thus the increase of absorption of the primary radiation. In case if the Compton-effect dominates in the modifying body, it can be advantageous to use one or more layers or coatings consisting of graphite or carbon or a carbon compound in the modify¬ ing body. It can be expedient, if the surfaces of the layers of the modifying body are provided with substantially monoatomic coatings which reduce the escape energy of electrons , consisting of alkali metal or alkali-earth metal or the oxids thereof or any other compound thereof. A positive ion reduces the potential barrier of the constituent element of the layer, representing the pre -requisite for the tunnel effect. Evaporation of the coating is not to be afraid of, accordingly, Li O . . . CS2O compounds , as well as oxids of alkali -earth metals are well suitable for this purpose. One has to reckon also with a secondary electron emission, said coatings are well suitable for this purpose , too. Due to the secondary electron emission smoothness of surfaces is imperative , otherwise the electrons are easily trapped on the porous surface . In respect to the arrangement of the modifying body in an electric field it is advantageous , if there is at least one layer made of a conductive material - preferably of Al - being insulated from the other layers and provided with an electric contact and a terminal connected thereto . The modifying body according to the invention can be prepar¬ ed so that all layers of a layer group are applied onto a carrier sheet being substantially transparent for X-ray or gamma radiation, and between the layers separating layers are inserted. According to another embodiment all the layers of all layer groups are applied to one single carrier sheet one after the other . The carrier sheet can be made of paper or plastic or aluminium foil. It is considered as very advantageous , if all the layers as well as the separating layers in¬ serted inbetween - e . g. made of AI2O - are applied onto a single carrier sheet by vacuum deposition. In the same manner, most easily , eventual coatings on the layers can be applied also by evaporation. In case if as a target an AgBr film is used, from the point of view of sensitivity, expediently a modifying body is to be selected, with which the energy of the secondary radiation emitted by the element of the last layer group surpasses by 100 % at most, preferably by 50 % the most, the absorption energy level of the element of the target. b. a given case it can be favourable if the modifying body according to the invention comprises a layer group which contains an element emitting a secondary radiation , the energy of which is approximately an integer multiple of the energy level corresponding to the transition between the electron shellsK and L of the element in the target. Thereby, energy of the exciting secondary radiation is selected so that it equals to an integer multiple of the energy of radiation emitted by the excited material. In case e . g. of an X-ray film containing Br , a Pb layer group can be used in the modifying body, with which the ratio is approximately sixfold. In such a manner inter - ference amplification can be obtained between two radiations , which may result in an increased blackening of the X-ray film. Brief description of the drawing The invention will be described in detail by means of pre¬ ferred embodiments serving as examples , by the aid of the drawing enclosed, wherein Figure 1 is a schematical view of the modifying body according to the invention and the application thereo in sense of the invention, and Figures 2 to 4- are schematical views of embodiments of the modifying body according to the invention being suitable for an X-ray film target. Modes for carrying out the invention In Fig. 1 a radiation beam 9 emitted onto an object 10 to be examined by a radiation source 1, which can be a usual industrial X-ray apparatus, is confined by an aperture 2. Due to the radiation beam 9 travelling through the object 10 radiograph of the object 10 appears on the target 7, e. g. on an X-ray film. The modifying body according to the invention is arranged between the object 10 and the target 7. The modifying body consists of n layer groups 31, 32 , 33, . . . 3n which are superposed on one another and are lying approximately perpendicularly to the radiation beam 9. Every layer group is compose of a plurality of layers superposed on each other, so e . g. the layer group 32 contains jc layers 81 , 82 , . . .8k . Adjacent layers e . g. 81 an 82 are separated by a thin separating layer /not to be seen in the figure For the sake of visibility in Fig. 1 layers and layer groups are not illustrated according to the actual scale , similarly, Figs . 2 to 4- are not accurately scaled, either. la case if the target 7 is an AgBr X-ray film being sensitive to X-ray radiation, materials of the layer groups 31 , 32 , 33, . . . 3n are selected so that the energy of the X-ray beam entering into the first layer group 31 will be transposed gradually by the layer groups into the range of maximum sensitivity of the X-ray film forming the target 7. Further on, before symbols of the elements the atomic number Z will always be indicated. The energy level of absorption defined by the electron shell K of an element, representing the limit value of excitatio of said element, expressed in unit keV, will be indicated with K. The most probable energy levels of emission corresponding to the transition between the electron shells K and L of the excited element, expressed also in unit keV, are marked with 0(1 and ° 2. For the aforemention gradual energy transposition the constituent element - of the layer groups 31 , . . . 3n for the AgBr X-ray film can be selected according to the following columns: 44Ru 60Nd K =22,12 K =43,57 « 1 = 11,92 o l = 37,36 <X2 = 11,88 (X 2 =36,84 J I 41Nb 55Cs K = 18,99 K = 35,98 < ! = 16,61 CXI =30,97 (X 2 = 16,52 (X2 = 30,62 38Sr 51 Sb K = 16,11 K = 30,49 0(1 = 14,16 <X 1 =26,36 K = 13,47 K = 25,51 o 1 = 11,92 <X 1 =22,16 «2 = 11,88 < 2 = 21,99 As it becomes obvious from the columns, the elements are to be selected so that the energy of the exciting radiation falling onto the element should surpass the energy level Ε. of absorption, at the same time the emission energy levels <Xl and<X2 of the characteristic radiation emitted by the excited element should be higher than the absorption energy level K of the following element. Series of excitation of 35Br prior to 44Ru can be as follows: 74W-68Er-62Sm-57La-52Te-48 Series of excitation of 47 Ag prior to 60Nd can be as follows: 78Pt-71Lu- -65Tb. In respect to the practice here the series can be closed. Limit energy level of sensitivity of AgBr X-ray film is defined by the absorption energy level K of 47 Ag. However, we found that it is advantageous if energy of radiation falling onto the X-ray film is fitted also to 35Br, e. g. in accordance with the previously described 35Br series, as in such a manner efficiency of blackening of the X-ray film can be increased. Fig. 2 illustrates a modifying body with such a layer arrange¬ ment wherein in the path of the radiation beam arriving in. the direction as indicated by arrow 17 first a layer group 41 containing layers with 51 Sb material is arranged, followed by a layer group 42 contain¬ ing layers with 38Sr material. Emission energy levels o< l and oc2 of characteristic radiation emitted by 5lSb are on the one hand fitted to the absorption energy level K of the component 47Ag of the AgBr X-ray film i. e . to the target 7, on the other hand higher than the absorption energy level of 38Sr, as a consequence , the latter will be excited. Energy levels « 1 and«2 of characteristic radiation emitted by 38Sr are matched to the absorption energy level K of 35Br. Accordi the layer group 42 containing layers with 38Sr material allows to pass a part of the incident radiation to the target 7 , while the other part is absorbed and emits instead a radiation with an energy matched to 35Br. In addition, the modifying body according to Fig. 2 is provided with two graphite coatings 15 and 16, which are - with the embodiment described here - applied onto the first layers of the layer groups 41 and 42. Graphite coatings 15 and 16 contain 6C with a low absorption energy level K , behaving as an electron donor. Layers of the layer groups 41 and 42 can be additionally provided with a mono -atomic coating /not illustrated here/ reducing the escape energy of electrons . Layer groups 41 and 42 are surrounded by layers 11 and 12 of Al-mater serving as plates for generating an electric field, and they are connect ed with terminals 13 and 14 via contacts not illustrated here . By insert ion of an insulating layer, the layers 11 and 12 can be applied onto the layer groups 41 and 42 by evaporation. In the modifying body according to the invention, from the series of elements having been described in connection with Fig. 1, one or more members may be left out. In the course of transposition of energy level larger steps are also permitted. In Fig. 3 such an ---__-_ embodiment is to be seen, wherein in front of the AgBr film target 7, in the path of the radiation beam coming in the direction as indicated by the arrow 17, two layer groups 51 and 52 are arranged. Material of the layer group 51 is selected so that energy levels 0.1 and 0(2 of the characteristic radiation emitted should be approximately the integer multiple of the energy level defined by the transition between the electron she lls Ε. and L of 47Ag in the target 7 - At the same time , material of the layers of the layer group 52 is selected so that energy levels cxl and <*2 of the characteristic radiation emitted thereby should be approximately the integer multiple of the energy level defined by the transition between the electron shells K and L of 35Br being present in the target 7. So e . g. 82Pb 35 Br K = 88,01 K = 13,47 CX 1 = 74,96 -« — »■ C* l = 11,92 0 ( 2 = 72,79 -* — *• OC 2 = 11,88 Accordingly, the material of the layer group 51 can be 66Dy /double / or 79Au /triple /, that of the layer group 52 can be 49In /double /, 60Nd /triple /, 68Er /quadruple /, 75Re /quintuple / or 82Pb /sextuple/. Advantageously, 66Dy is paired with 49In or 68Er, while 79Au with 6θNd or 82Pb . With such a formation interference gain can be achieved between the two radiations . In another possible embodiment the materials are selected so that characteristic radiations emitted by the material of the layer group and the target, respectively, are weakening i. e . partly extingui ing one another. For this phenomenon ratios of energies are to be chosen so that the larger wavelength should give the uneven multiple of the half of the smaller wavelength. This requirement can be met, if ratio of energy levels amounts to 1 ,5; 2,5 ; 3,5 ; 4,5 etc. If the uneven number has the form 3 , wherein n is an integer, ratios 1,5 ; 4,5; 13,5 etc. are obtained . Expediently, the ratio 4,5 is to be selecte Elements matching to 35Br with a ratio of 1,5 are 28Ni, 44Ru, 56Ba, 72Hf and 91Pa, those matching to 47 Ag are 37Rb, 6θNd and 77Ir. With the ratio 4,5 17C1 and 74W are matching to 35Br and 22Ti and 97Bk to 47 Ag. This formation may be advantageous , if unde sired radiation effects are to be eliminated. So e . g. in making X-ray photographs of the human body it may be advantageous to weaken the radiograph of human bone, because of the considerable 20Ca content of it, with ele¬ ments l6S , lONe or 6C . On the radiograph the weakened object appears more transparent without fading of th e other parts of the film, at the same time parts behind the object examined, having been covered up to now, will be seen better. In Fig. 4 a modifying body for a AgBr X-ray film target 7 can be seen, in which in the path of the radiation beam coming in the direction as indicated by the arrow 17 layer groups 6l , 62 , 63 and 64 are arranged one after the other. Layers of the layer group 61 contai 51 Sb, layers of the layer group 62 contain 5θSn, layers of the layer group 63 contain 38Sr and layers of the layer group 64 contain 37Rb . la this embodiment elements 5lSb and 38Sr play the same role as in the embodiment according to Fig. 2 , that means that 5lSb is matched to the component 47Ag of the X-ray film and 38Sr to the component 35Br The role of the elements 5θSn and 37Rb lies in to produce a radiation for the component 47 Ag and 35Br, respectively, the energy level of which is lower than the corresponding absorption energy level however it is advantageously higher than the corr sponding OCl energy level. In such a manner atoms 47Ag and 35Br are quasi pre-excited in order to obtain a better efficiency in respect to the absorption of the radiation emitted by 5lSb and 38Sr, respectively. So e . g. 50 Sn • 47Ag K = 29 ,20 K = 25,51 C< 1 = 25,27 0 ( 1 = 22, 16 <X2 = 25,04 < 2 = 21 ,99 It can be well seen that the characteristic radiation of 50Sn is lying between the absorption and emission energy levels of 47 Ag. 48Cd and 49ϊn are suitable pre -exciting elements to 47 Ag. Characteristic radiation emitted by 37Rb performs pre-^xciting of 35Br. In the embodiment according to Fig. 4 before the first layer group 61 layers 18 with 82Pb material are arranged for absorb¬ ing the scattered radiation coming from the object examined and the environment, as well as for the simultaneous emission of secondary radiation. Behind the target 7 layers 19 with 82Pb material are arranged for absorbing the re -scattered radiation. Immediately before the target 7 one or more layers 20 containing 82Pb are arranged for absorbing the scattered radiation arising in the layer groups 61 , . . . 64 The embodiment according to Fig. 4 can be well used for radiographs serving for industrial purposes. In this case total thick - ness of the layers 18 amounts to 100 to 500 am, while this layer group is composed of 82Pb layers of the thickness of 1 m or even less. Layers 19 can be similarly formed. The single layer 20 may e a 82Pb lawyer of the thickness of 10 to 30 urn. Layer groups 6l , . . . 64 are of the thickness of 25 to 125 urn each, being formed of layers of 5lSb, 50Sn, 38Sr and 37Rb , respectively, in a thickness of 1 urn or even less. Between adjacent layers e . g. Al D separating layers of 0, 1 urn are to be found. Any element of the series can form a separating layer, so e . g. in the layer group 61 separating layers of 5θSn of the thickness 0, 1 rum can be used between the layers of 51 Sb. For the sake of order it should be mentioned that the thickness of the layer groups 61, . . . 64 need not be necessarily identical, within one layer group layers may have different thicknesses . The modifying body according to the invention can be realized differently from the embodiments shown in the drawing. So e. g. it can be prepared as a flexible sheet, which is well matching to targets having not a plain surface .

Claims: Claims 1. A method for influencing the effect of X-ray or gamma radiation on a target sensitive to the radiation, preferably for selective modification of an image of an object formed on a target by X-ray or gamma radiation, in the course of which a modifying body having laminar structure is arranged in front of the target in the path of the radiation beam, characteriz ed by disposing at least two layer groups /31, 32, ...3n/ in front of the target /7/, each of said layer groups /e. g.32/ comprising a plurality of superposed layers /81, 82, .. ,8k/ emitting a secondary radiation under the influenc of the X-ray or gamma radiation, or the secondary radiation of the previous layer group /e. g.31/, respectively, the energy of which is lying above the absorption energy level defined by the electron shell K of an element being present in the following layer group /e. g.33/ or in the target /7/ arranged behind the last layer group /3n/, respectively. 2. The method as claimed in claim 1, charact erized " by disposing in front of the target /7/ also a layer group /62, 64/ emitting a secondary radiation, the energy of which is lying between the absorption energy level and the emission energy level defined by the electron shell 1 of an element being present in the following layer group or in the target /7/, respectively. 3. The method as claimed in claim 1 or 2, char act eriz¬ ed in that in direction of the target /7/ each successive layer group /e. g.32/ contains an element with lower atomic number than that of the previous layer group /e. g.31/. 4. The method as claimed in any of claims 1 to 3, ch ar a c -' terized by generating at the layer groups /3l, 32, ...3n/ an electric field with a direction corresponding or opposite to the radiation beam. 5. The method as claimed in any of claims lto3, char a c - terized by disposing Pb layers /18/ superposed on one another between the object /10/ to be examined and the first layer group /6l/ facing the object /10/. 6. The method as claimed in claim 5, char acte ri z ¬ ed by disposing superposed Pb layers /19/ behind the target, / /, 7. A modifying body for influencing the effect of X-ray or gamma radiation on a target sensitive to the radiation, comprising a plurality of superposed layers, ch ar acte ri ze d by comprising at least two superposed layer groups /31, 32, ...3n/ , each of said layer groups /e. g. 32/ comprising a plurality of superposed layers /8l, 82.. ,8k/ containing an element which emits a secondary radiation under the influence of the X-ray or gamma radiation or the secondary radiation of the previous layer group /e. g. 31/, respectively, the energy of which is lying above the absorption energy level defined by the electron shell K of an element being present in the following layer group /e. g. 33/ or in the target /7/, respectively. 8. The modifying body as claimed in claim 7, cha r ac - t e r i z e d by comprising a layer group /62, 64/ which contains an element emitting a secondary radiation, the energy of which is lying between the absorption energy level and the emission energy level defined by the electron shell K of an element being present in the following layer group or in the target /7/, respectively. 9. The modifying body as claimed in claim 7 or 8, char ac te rized in that the thickness of the layers /81, ...8k/ is less than 100 yum, preferably less than 30 /um. 10. The modifying body as claimed in claim 9, c h ar ac - te rized in that the thickness of the layers /81, ...8k/ lies in the range between 0,1 and 10 yum. 11. The modifying body as claimed in claim 7 or 8, char a cteri ze d by comprising one or more layers or coatings /15, 16/ consisting of graphite or carbon or carbon compound, producing Compton-electrons . 12. The modifying body as claimed in claim 7 or 8, char cteriz ed in that the surfaces of the layers /8l, ... 8k/ are provided with su stantially mono atomic coatings consisting of alkali metal or alkali-earth metal or the oxids thereof or any other compound thereof, facilitating electron departure. 13. The modifying body as claimed in claim 7 or 8, char acterized by comprising at least one layer /ll, 12/ made of a conductive material - preferably Al - being insulated from the other layers and provided with an electric contact and a terminal /13, 14/ connected thereto. 14. The modifying body as claimed in claim 9 or 10, characterized in that the layers /8l, ...8k/ are applied onto a carrier sheet being substantially transparent for X-ray or gamm radiation, and that between the layers /8l, ...8k/ separating layers are inserted. 15. The modifying body as claimed in claim 14, char ac t erized in that all the layers of all layer groups /3l, ...3n/ are applied onto one single carrier sheet. 16. The modifying body as claimed in claim 14, char a c t erized in that the carrier sheet is made of paper or plastic or aluminium foil. 17. The modifyin-g body as claimed in claim 14, charac t erized in that the layers /81, ...8k/ and the separating layers are applied onto the carrier sheet by vacuum deposition. 18. The modifying body as claimed in claim 7 or 8, characterized in that in case of AgBr- film as a target /7/ the energy of the secondary radiation emitted by the element of the last layer group /42/ is Higher by 100 % the most, preferably by 50 % the most, than the absorption energy level of the element of the target /7/. 19. The modifying body as claimed in claim 7 or 8, . cha r acterized by comprising a layer group /5l, 52/ which contains an element emitting a secondary radiation, the energy of which substantially equals to an integer multiple of the energy level corresponding to the transition between the electron shells K-L of the element being present in the target /7/. 20. The modifying body as claimed in claim 19, charac¬ terized in that for an AgBr film target /7/ there is a layer group /52/ containing at least one of the elements In, Nd, Er, Re and Pb or of their compounds . 21. The modifying body as claimed in claim 19, char a c - teriz ed in that for an AgBr film target /7/ there is a layer group /5l/ containing at least one of the elements Dy and Au or of their compounds. 22. The modifying body as claimed in claim 7 or 8, characterized in that for.an AgBr film target /7/ there is a layer group /41 , 42 ; 61 , 63 / containing at least one of the elements Sb and Sr or of their compounds . 23. The modifying body as claimed in claim 8, char a c - t eriz ed in that for an AgBr film target /7/ there is a layer group /62/ containing at least one of the elements Ag, Cd, In and Sn or of their compounds . 24. The modifying body as claimed in claim 8 or 23, cha ra t eriz ed in that for an AgB t r film target /7 / there is a layer group /64/ containing at least one of the elements Br and Rb or of their compounds . LIST OF REFERENCE SIGN S OF THE DRAWING 1 radiation source 2 aperture 31, 32, . . .3n layer group 41, 42 layer group 51, 52 layer group 61, 62, 63, 64 layer group 7 target 81 , 82 , . . .8k layer 9 radiation beam 10 object 11 layer 12 layer 13 terminal 14 terminal 15 coating 16 coating 17 arrow 18 layers 19 layers 20 layer

Inventors: TELEKI PETER, TELEKI, PETER
Applicants: INNOFINANCE ALTALANOS INNOVACI, INNOFINANCE ALTALANOS INNOVACIOS PENZINTEZET
Application year: 1985
Main classification: G03B42
IPC codes: G01N23, G01T1, G03B42, G21K1, G21K4