DE3234402A1 - DEVICE AND METHOD FOR THE ELECTROCHEMICAL DEVELOPMENT OF DEFECT TRACKS CAUSED BY NUCLEAR PARTICLES - Google Patents

Description

Comitato Nazionale per la Ricerca e per Io Sviluppo dell ' Energia Nucleare e delle Energie Alternative -ENEA, ROM / Italy

Device and method for the electrochemical development of traces of defects caused by nuclear Particles are caused.

The invention relates to an apparatus for the electrochemical development of traces produced by nuclear particles are caused, according to the preamble of claim 1 and a method for electrochemical development such traces,

From the various systems for recording loaded

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heavier particles is the inventive method advantageous for the detection or acquisition and dosimetry of fast neutrons, for critical dosimetry in the detection of (thermally) fissile impurities of low concentrations and of alpha emitters in biological samples and samples from the environment, when measuring radon radiation during the analysis of seismic defects or faults in uranium prospections, in the prospection of geothermal deposits high energy, in industrial neutron radiography, in alpha autoradiography, in the production of biological ones and industrial filter media, when calculating the resistance of insulating layers of electrical partial discharge channel formations, which is the cause of the destruction of electrical cables.

Most uses of detectors for nuclear traces - nuclear emulsions or insulating transparent ones Materials that are chemically developed are complicated by the fact that a microscope with high magnification is required.

When counting the traces caused by highly ionized charged particles, for example by fission fragments, have overcome the aforementioned difficulties through the use of an automatic reader overcome by "holes" called "spark counters". However, such a device can only be used in conjunction can be used with through holes, i.e. holes that have been subjected to normal chemical action go through the entire thickness of the detector.

In such a technique, an area of any size can be counted as a fraction of a second, while some Tens of thousands of microscope fields have to be scanned to cover the same area. Although the Spark counter technology is already on the market in several countries

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Market is, for example, in the USA, Canada, Great Britain, Federal Republic of Germany and Switzerland their use is limited to counting extremely high energy charged particles, for example Fissure fragments. In fact, the traces of defects caused by alpha particles and by the rebound of caused by fast neutrons in plastic layers were only a few microns (microns) long after a chemical evolution that is not long enough to cause through holes in a plastic layer with a practical thickness of ^ t 10 μια.

As a result of the electrochemical development of the present invention, various uses are made of the Detectors for traces caused by energy particles of low energy, for example fissure fragments have been made practically accessible.

The electrochemical development according to the invention enables to develop nuclear traces in solid insulating materials to such an extent that they are affected by the visible to the naked eye. In practice, the electrochemical evolution of nuclear traces in a layer of an irradiated detector-i.e. in a layer of irradiated, insulating material - thereby obtained that the layer is exposed to an alternating electric field, while the same layer is exposed to a chemical Is exposed to action that is likely to develop the nuclear traces already in their exist latent state in the layer material. The nuclear traces behave like needle-like defects, which penetrate the insulating material and in their tips the electric field can be a hundredfold or Thousands of times greater than the average electric field, which is such that different species electrical phenomena thereby within the tracks, such as dielectric loss, electrical

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Breakthroughs, etc., are initiated. The nuclear traces - initially a few tens of scary romans - can get through the combined effect of the electrical phenomena and the chemical action up to macroscopic orders of magnitude can be enlarged so that they can be seen by the naked eye. Counting the tracks can do this by reading or by reading with the eye.

Although there are a number of problems with the detection and dosimetry of alpha particles and neutrons have been eliminated by electrochemical engineering, making them successful in many laboratories became applicable throughout the world, the following restrictions apply:

1. It must be used insulating layers that are much thicker than the trace lengths, as a result very high voltages (^ 800 volts rms) must be used.

2. The development process is drastically interrupted if a short circuit due to a perforation of a Detector layer occurs.

3. Such traces, which run through the entire layer thickness, cannot be developed.

4. Automatic and rather expensive counting systems are required.

5. The track overlap is very large if the track

2 density is more than about 5000 tracks per cm.

6. The developing device is complex.

The invention is therefore based on the object of providing a device and a method of the type mentioned at the beginning to create, with which a trace development is possible in such a way that the detector layer of any Thickness can be, as a result, the entire thickness of the layer can be traversed by the track and stresses of only a few tens of volts rms are required or

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even only constant voltages are necessary when the tracks go through completely.

According to the invention, this object is achieved by the subject matter of claim 1 solved. Further refinements emerge from claims 2 to 8. A method of the type mentioned at the beginning results from the features of claims 9 and 10, respectively.

According to the present invention, a short circuit that occurs with every perforation of the insulating layer is avoided, and the transfer of all nuclear traces - even if they are much shorter than the layer thickness - in perforations or perforations in the layer so that they can be counted automatically by a spark counter.

According to the invention, the rate of track overlap is reduced with the decrease in the thickness of the detector layer, which allows high-density traces to be developed.

Furthermore, an impression of the trace distribution in the insulating layer can be made can be achieved with high contrast and high resolution.

The invention provides an apparatus and a method for the electrochemical development of nuclear traces in Plastic layers in such a way that holes or perforations are generated through these layers, wherein no short circuit occurs.

The invention relates to an apparatus and a Process for the electrochemical development of nuclear traces in insulating materials / with these traces additionally to cause other defects perforations in the plastic layers that are much thicker than that Length of the tracks can be.

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A layer of plastic that functions as a detector has, has a surface covered or coated with a thin layer of metal; .as Metal, for example, aluminum can be used. This surface is in contact with an insulating liquid, while the non-metallized area is in contact with an electrolytic reagent, whereby only the latter area is developed.

The one to induce electrochemical evolution applied voltage can be either constant or variable; the voltage is variable when the tracks are not go through the layer.

According to the invention, in the layer by chemical reagents that are used for the development, conductive tracks generated. Applying a reasonable voltage becomes either constant or variable electrical Energy deposited along the tracks, which tracks may or may not pass, and / or electrical Track phenomena are induced at the needle-shaped tips of the tracks, these phenomena in combination with the chemical action of the electrolytic reagent take effect to make macroscopic, through holes or create openings in the plastic layers, even if these are not completely penetrated by these holes at the beginning.

If, according to the invention, a perforation occurs through the layer, it becomes circular Area of metal that is much larger than the perforation hole from the layer by chemical, electrical and electrochemical effects are removed and replaced with insulating fluid, which increases loss of resistance the continuous track when it is filled with electrolyte and to eliminate the short circuit which is generated by the electrolyte, which

passes through the entire thickness of the layer.

If, according to the invention, the voltage is applied across the layer in such a way that the thin metal layer has a positive polarity - if a constant voltage is used for trace development - or if the voltage is applied in the form of a variable voltage in such a way that the metal layer has a constant If the polarity is positive, the metal at each perforation will correspond to a nuclear track on the tracks or discharge channels oxidized, whereby the loss resistance increases and the current flow is limited. These electrical effect is automatically reduced in the perforated lane, which is then mainly chemical Effect is exposed. In this way the development of the special track is slowed down considerably, while the remaining traces remain under the combined action of electrical and chemical phenomena, until they penetrate the entire layer thickness.

The traces are then developed electrochemically to the extent of their passage through the entire layer thickness, whereby the cross-sections of the tracks are proportional to the layer thickness, the layer thickness then being the determining factor Element of the track overlay.

When the developing bias is applied to the layer in such a way that the thin metal layer becomes a has negative polarity - if a constant voltage is used for electrochemical development - or when a variable voltage is applied to the metal layer so that the latter has a constant negative polarity possesses, the cathodic dissolution of the metal is very high, the current flow through the perforation is likewise very large and the electrical instability often follows the consequent destruction of the layer. From these The metal layer should always have a positive polarity

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According to the invention, the areas of the metallized insulating material which can be traced back to the metal layer is or has been removed from the metal layer, represents a visible image of the nuclear traces.

According to the invention, the detector comprises a layer of insulating material of any thickness, one of which Surface is metallized; this layer is placed between two cells of insulating material after irradiation, one of which contains an electrolyte which is also a reagent useful for developing the traces while the other cell contains an insulating liquid.

According to a first embodiment, the device has two prismatic cells, each with an opening, while the sheet is sandwiched between the apertured sides of the cells. One cell is with filled with an electrolytic reagent and the other with insulating liquid. The metallized surface the detector layer is connected to one connection of a voltage standard, while its other connection is connected to an electrode immersed in the electrolytic reagent.

In a second embodiment of the detector, the use of the insulating liquid is not necessary. at In this embodiment, which is referred to as the "detector package", a metallized plastic layer is provided, which is attached to a plastic substrate, which is thicker than the layer, so that it can be used as a base or underlayer is used.

Several detectors of this type can be immersed in a container in which a chemical reagent '

medium is located.

The electrochemical development can then be carried out simultaneously for all detectors by the required Voltage is applied to the thin metal layer of each detector and the electrode, which are common to all Container is submerged.

In a third embodiment of the invention, the irradiated insulating material is partially over a central one Area of a surface metallized and fluid-tightly coupled with the same layer, while a U-shaped frame is temporarily stored from insulating material; a box-shaped cell is obtained in this way, which for Development is then filled with electrolytic reagent.

In a fourth embodiment of the invention, there are two plastic layers along with a metallized surface three of four edges of the corresponding, non-metallized surfaces connected, so that a plastic bag is formed.

The detectors according to the third and fourth embodiments can be developed in that the containers or bags are filled with electrolytic reagent and the voltage applied to the electrolyte and the metal layer of the outer surfaces is created.

The following are preferred embodiments of the Device and a method for the electrochemical development of nuclear traces in metallized plastic layers described with reference to the drawing to explain further features. Show it:

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1 shows a schematic vertical sectional view of an apparatus for electrochemical development,

Figure 2a is an exploded view of a detector unit referred to as a "detector package" and in a second embodiment of the apparatus for simultaneous development a multitude of detector layers is included,

FIG. 2b shows a perspective view of the elements shown in FIG. 2a in a coupled manner,

FIG. 2b ^{1 is} an enlarged perspective view of part of FIG. 2b,

2c is a vertical sectional view of two detector packages corresponding to FIGS. 2a and 2b, which are shown in FIG a container are immersed containing an electrolytic reagent for electrochemical Development is filled,

3a shows an exploded view of a detector unit, which is referred to as a detector container and in a third embodiment of the device is used for the simultaneous development of a large number of detector layers,

Figure 3b is a perspective view of that shown in Figure 3a Small te in coupling relation to each other,

3c is a vertical sectional view of three detector containers corresponding to Figs. 3a and 3b,

3d shows an enlarged vertical sectional view of a detector container corresponding to FIGS. 3a and 3b, and

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Figures 4a, 4b, 5a, 5b, 6a, 6b and 7 show results obtained by the The device according to the invention and the device according to the invention Procedures are obtained.

Reference is made to FIG. 1; one irradiated Plastic layer or plastic layer in which only one its surfaces is metallized with a metal layer 2 is made of insulating material between two cells 3 and 4 used, in which a chemical reagent 5 or an insulating liquid 6 is contained. The insulating liquid in the case shown is FREON (Frigen).

The cells 3 and 4 are each provided with an opening 3 ″, which is normally circular, in the center of the cell wall, namely that cell wall which is directed against the insulating material layer, the two openings being aligned with one another but having different sizes. so that the area of an opening 4 ^{1 of} the cell 4, which contains the insulating liquid 6, is larger than the opening 3 ^{1 of} the cell 3, in which an electrolytic liquid 5 is contained prevents tight adhesion between the irradiated insulating material 1 and the two cells 3, 4 A constant or variable voltage is applied to the plastic layer by means of an electrode 8 which is immersed in the electrolytic reagent 5 and a thin metal layer 2 which is applied to the detector layer 1 and acts as a second electrode The opening of the cell 4 filled with FREON is larger than that of the cell 3 with reagent in order to ensure the action of FREON over the entire surface which is wetted with the reagent.

Seals 7 and T made of insulating material are in good mechanical engagement or in good mechanical connection

between the cells 3, 4 and the irradiated insulating layer used to act as a leak-tight coupling between the two cells 3.4 when these two cells 3.4 in are appropriately pressed together.

The voltage required for the electrochemical action is applied to the irradiated layer 1 via the thin metal electrode 2 and the electrode 8 immersed in the electrolytic reagent is applied.

In Fig. 2 is a modified embodiment of the invention Device shown. According to Fig. 2a, this device has an irradiated plastic layer 1, which with a thin metal layer 2 is provided, which is in the form of a thin plate with an extension for connection to a Conductor 2 'and can be provided with a substrate 13, which, when glued to the plate, has the appearance shown in Fig. 2b and is hereinafter referred to as the "detector package" referred to as.

A container 14 filled with the electrolytic reagent is used for electromechanical development; the detector packs 15 are immersed in the container. In the embodiment shown in FIG. 2c, only two such detectors or detector packs 15 are provided, but it can be seen that any number of such detector packs 15 can be provided; the voltage required for the electrochemical development is applied to the electrode 8, which is immersed in the liquid in the container 14, as well as to electrodes 2 ^{1 of} the detector packages 15. The constant and / or variable current is carried in such a way that it over each Detector 1 acts, which were previously irradiated and from which the defect traces are to be developed.

With reference to FIG. 3, another embodiment for electrochemical development is described at

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which two detector layers 1 (above, detector layers also generally include detector plates or the like to understand) with the associated metal layers 2 on each side of a support unit or aging unit 16 are attached; by "attached" is to be understood any connection, e.g. gluing, welding or the like. The fastening device 16 is in the form of a rectangular frame, which the upper member or the upper Rod is missing, so that when the two layers or plates are attached to the frame, a small box-shaped container is formed which holds the electrolyte liquid therein 5, which is suitable for the development of nuclear traces. In a special, not shown Embodiment, the frame by a fluid-tight connection of the plates to each other along the corresponding edges must be eliminated, except for the upper edge. Thus, a bag or sack is formed which has the function of the aforementioned container.

Devices of this type are shown in the development arrangement in FIG. 3c; while only three such units are shown, more or fewer of these units can be provided. The required tension becomes Applied over the thin metal layers 2 of each pair of detectors - these layers are located on the Outer surfaces of the container and via an electrode immersed in the liquid reagent 5 in the container, all such units being connected in parallel, as can be seen from FIG. 3c.

In the following, the operation of the inventive gi Device explained in more detail:

If the device has two cells according to FIG. 1, the irradiated insulating material 1 is inserted between the cells 3, 4 in such a way that the non-metallized Surface is in contact with the electrolytic reagent 5, which is suitable for the electrochemical

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Development that furthermore the metallized surface is in contact with the insulating liquid 6; the cells 3 and 4 are then each filled with reagent or insulating liquid, for example FREON or a other means and then the output of a generator for constant or variable voltage to the thin Metal layer and the electrode 8, which is in the electro-Iytische Reagent 5 is immersed for the length of time necessary for the traces to develop in such Circumference designed so that holes are created through the metalized layers or plates in such a way that that they can be counted in a simple manner, for example by means of a spark counter.

In the device according to FIG. 2, the plastic layers are or to attach plastic plates to the substrate 3 in such a way that the metal 2 these plastic plates opposite; those trained in this way or The arranged device is then immersed in the container 14 (FIG. 2c) together with the electrode 8. That Substrate 13 is used to electrically isolate the metal electrode 2 opposite the electrolytic reagent 5 in the container 14.

A source of constant or variable voltage is then applied to electrode 8 and to the group of electrodes connected, made up of thin metal layers in such a way are that the latter have a constant positive potential with respect to the electrode 8. Such connections are maintained for a period of time necessary to obtain a perforation on each track. Similar the embodiment is like the previous embodiment according to Fig. 3, in which the device in the form of a box or a box or even in the form of a Plastic boutels is formed. In this embodiment the device is obtained in that two Detector layers or detector plates on a frame

attached or attached to each other and that then the container obtained in this way with an electrolytic Reagent 5 is filled and finally a constant or variable voltage is applied to the thin electrodes 2 is applied over the outer surfaces of the sheet and to the electrodes 8, which are inserted into the device are immersed, three or any other number of such units being provided according to FIG. 3c could be. The voltage of the thin metal electrodes either in the case of a variable voltage or in the case of a constant voltage must be positive with respect to the electrode 8 in each case. The connection to the voltage generator is for the period of time required to obtain a perforation on each track.

It should be noted that the detector package according to Fig.2 and the detector of Figure 3 - the latter detector is evidently free of an electrolytic reagent suitable for use as physical detectors for charged particles. After exposure to radiation they are developed in accordance with the explanations of the various embodiments of the device according to the invention.

Some examples of the results obtained by developing traces by means of the device according to the invention are shown in FIGS. 4a ff.

The thickness of the insulating material to be used is not a limiting factor. In fact, any thickness can be used be used. However, the handling of the sheet or plate is practically facilitated by using Layer or plate thicknesses with more than 0.5 μΐη.

FIGS. 4a, 4b show two images obtained by irradiation can be obtained from two polycarbonate sheets or layers with a thickness of 10 μΐη, one of which has a surface

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was covered with a thin layer of aluminum, the irradiation with the same fluence of fission fragments was carried out and subsequently the electrochemical development at ambient temperature in a 6N-KOH solution takes place in water with FREON as an isolating agent and with a constant electric field of about 25 KV / cm, which in this case corresponds to an applied voltage of only 15 volts.

If the aluminum layer has a negative polarity, the electrochemical development will take place after one hour and 30 minutes interrupted because of the excessive power loss in the perforated tracks (Fig. 4a). As the If the aluminum layer had positive polarity (Fig.4b), the electrochemical development was due to up to eight hours the excellent erasing effect on the short circuit of each track due to the anodic oxidation of Aluminum expanded.

5a, 5b show a comparison of two images, by irradiating a polycarbonate sheet with cleavage fractions was obtained, the polycarbonate plate in this example being 40 μm thick and the electrochemical Variable voltage development was performed; the aluminum layer was alternately opposite the Electrode immersed in the electrolyte on negative and positive polarity.

In the first case (Fig. 5a) a spark occurred with propagating Art sometimes after a single perforation of the plate, whereby the spark had a tendency to open catastrophic way to destroy the disk regardless of the presence of FREON.

In the second case (Fig. 5b) the short circuit was deleted so marked at each perforation that all splitting fraymontspuron were developed and each one

Generated perforation.

Figures 6a and 6b show images of specimens, respectively, which are identical to those of Figures 5a, 5b, i.e. a Had a thickness of 40 μm and which were developed in each case while the aluminum layer was on positive polarity; in one case (Fig.6a) FREON was used, while in the other example (Fig. 6b) no FREON was used.

From Fig.6a and 6b, however, it can be clearly seen what the effect of the insulating liquid, in the present case FREON, is, namely that circular surfaces or areas following aluminum removal that are relatively smaller than those obtained without FREuN.

In accordance with the present invention, FIG. 7 shows an image obtained with cellulose triacetate a thickness of 20 µm, one surface being coated with aluminum. After irradiation in The detector plate was electrochemically in contact with a layer or layer of natural uranium for three hours long at ambient temperature and with an ON-KOH solution developed in distilled water, whereby the aluminum layer was brought to positive polarity and that electric field was 25 KV / cm at 2 KHz.

Fig. 7 shows a photomicrograph, with the aluminum surfaces when alpha traces were removed.

The term "insulating means" used above generally refers to non-conductive materials.

According to the method, the non-metallized surface is the irradiated layer or plate of an effect exposed to a liquid electrolytic reagent while the other surface is in contact with an insulating

liquid is brought. A constant or variable electric field is applied to the layer or plate applied so that the metal layer is brought to a positive polarity by means of a voltage generator. The electric field is applied to the layer or plate by having an electrode that is immersed in the electrolyte is immersed, and the metal layer is connected to the poles of the generator. After further Embodiments is the metallized area of the Do not bring the layer or plate into contact with an insulating liquid, but with air.

Claims (10)

Claims (T ^ device for the electrochemical development of traces, which are caused by nuclear particles in a layer or plate of insulating material or non-conductive material over a surface with a thin metal layer, the development by electrochemical application of the layer or plate with a electrochemical reagent and by applying an electric field to the plate, characterized in that during development the metal layer is connected to one terminal of a voltage generator which optionally generates a constant or variable voltage, while the other terminal of the same generator is connected to an electrode which is immersed in the electrochemical reagent. • a- 2. Apparatus according to claim 1, characterized in that two prismatic cells each with one Opening are provided that the opening through a of the walls and that the irradiated insulating material or non-conductive material on a its surfaces is metallized / fluid-tight between the two cells in alignment with the respective one openings of the cells is directed to the metallized surface of the plate that the one cell with a Insulating liquid or non-conductive liquid is filled, while the other cell with an electrolytic Reagent is filled, in which an electrode is immersed, which is connected to a connection of the generator is in communication, while the other terminal is connected to the metal layer with which the Surface of the insulating material is coated. 3. Device according to claim 2, characterized in that that the openings are circular and coaxial and that the one opening which is used for the electrolytic Cell belongs, smaller than the opening selected for the insulating liquid. 4. Apparatus according to claim 3, characterized in that that the insulating liquid is FREON. 5. Apparatus according to claim 1, characterized in that the metal layer with which the insulating material layer or insulating material plate is coated, only over a limited, central area of a their faces and over a narrow strip that runs from the central area to the top edge of the plate ranges from which the metal layer is connected to a terminal of the voltage generator via a wire is that an insulating material plate is connected to the insulating material layer in such a way that the metal layer lies between the sheet and the plate, thereby forming a detector package, that an insulating material container is provided in which any number of packages are immersed is that one of the generator connections is connected in parallel to all metal layers of the packs and that the other terminal is connected to that electrode which is in an electrolytic reagent is immersed, which is contained in the container. 6. Device according to at least one of the preceding claims, characterized in that the insulating material layer is provided with a metal layer only over a central area of a surface and that the metal layer runs through a narrow metal strip to the top edge of the layer, which with another similar layer with interposition of an insulating material frame in the form of an open U is in coupling relationship, wherein the frame is open at the top and a box-shaped container is formed that the non-metallized The surfaces of the two layers are opposite to one another and are attached to the frame in a fluid-tight manner, that the metallized areas of the layers within a projection of the frame on a vertical plane include that the space between the two layers is filled with electrolytic reagent, that an electrode is immersed in the reagent, that all electrodes are connected in parallel and with one Terminal of the voltage generator are connected, while the other terminal with all metal layers of the box-shaped container is connected in parallel. 7. Apparatus according to claim 1, characterized in that that one surface of the insulating material layer with a Metal layer is only provided over a central area and that the metal layer in a narrow Strip extends so that it reaches the top edge of the layer and that the layer with a other identical layer is provided in the form of a paired unit which is fluid-tight with the first layer communicates along its peripheral edge and with the exception of the upper edge, whereby a pouch is formed that the joint edge does not interfere with the metal layer that does not metallized surfaces of the two layers face each other that the bag during development is filled with electrolytic reagent / that an electrode is immersed in the reagent, that for development, any number of bags are arranged in such a way that all of the metal layers are parallel are connected to one another to one of the connections of the voltage generator and the electrodes, which are immersed in the electrolyte of all bags, connected in parallel with each other and with the other Connection of the voltage generator are connected. 8. Device according to at least one of the preceding claims, characterized in that the metal layer, with which one of the surfaces of the insulating material is provided or coated, made of aluminum consists. 9. Process for the electrochemical development of traces created by nuclear particles in a layer of insulating material are caused, the development being carried out to such an extent that each trace the penetrates the entire thickness of the layer, characterized in that an insulating material layer which at least partially is provided or coated on a surface with a thin metal layer / one to be detected Exposure to radiation that the irradiated layer is used in a device in which the not with the metal layer provided area of the layer is in contact with an electrolytic reagent in which one electrode is immersed while the other surface is in contact with an insulating liquid stands, that the immersed in the electrolyte electrode to the negative terminal of a voltage generator is connected, that the metal layer is connected to the other terminal of the generator / and that the generator generates a constant voltage and maintains the voltage for a period of time, which is sufficient to develop the traces present in the irradiated layer. 10. Process for the electrochemical development of traces created by nuclear particles in a layer of insulating material,
characterized / that a layer of insulating material covered at least partially on one surface with a thin layer of metal is exposed to radiation to be detected or detected, that the irradiated layer is inserted into a device in such a way that the one not provided with a metal layer Surface is in contact with an electrolytic reagent in which an electrode is immersed while the other surface of the layer is in contact with an insulating liquid, that the immersed in the electrolyte electrode to a terminal of a generator for generating a variable voltage is connected that the metal layer to the other terminal of the Generator is connected, and that the voltage generator has a variable voltage generated so that the metal layer is always positive to that electrode in the electrolyte is immersed, and that the voltage is maintained for a time sufficient to develop the tracks in the irradiated layer is generated or created.