FR2883383A1 - Optical and electronic device for locating and mapping e.g. transuranic element, has optical capillary fiber bundle comprising shape of cylinder or frustum of pyramid with square base or frustum of cone - Google Patents

Abstract

The device has an optical capillary fiber bundle (1) comprising the shape of a cylinder or a frustum of pyramid with square base or a frustum of cone. The bundle has a large front base directed towards a source to be located and a large rear base in contact with a photon detector. The bundle presents an outer diameter in the range of 1 to 20 centimeters and a length in the range of 2 to 50 centimeters.

Description

The present invention relates to remote localization and to the

  mapping of electromagnetic sources emitting in the extreme ultraviolet, X and gamma or in the field of beta radiation.

  This type of radiation is encountered in Scientific Research, in the Nuclear Industry and in the Medical field.

  Extreme UltraViolet radiation has become commonplace in the etching of silicon wafers in the electronics industry.

  X-rays are an essential tool for diagnosis in the manufacturing industry, in the medical field but also in research including biological.

  Beta, X or gamma radiation is emitted by radionuclides such as transuranics, and nuclear fission products encountered in the nuclear industry; while they pose a serious challenge for the protection of workers and the public, they are difficult to locate by conventional methods imprecise, insensitive and often requiring the close intervention of a worker subject to ionizing radiation.

  These electromagnetic radiations are characterized by their wavelength (in nm) or by the energy of their photons (in eV or KeV or MeV). We go from one to the other by the formula: E = h * c / X, h, being the Planck constant, c, the speed of light,?, The wavelength.

  To create images from X-rays, or gamma lenses are not available to focus these rays and then to make a camera or a camera in the usual sense or camcorder.

  The current means can be summed up: + to a sensitive plate to stick against the object to be imaged, as one sees it in radiography of the human body; this plate is bulky and can be contaminated if the radioactive sources are flush.

  + 1 use of a pinhole, which allows to create a homothetic image on a CCD. The pinhole is always a small hole that captures in a very small amount the radiation of the source X. So its sensitivity is really very bad.

  + to the complex implementation of coded masks, whose legibility is precarious, because of the artifacts peculiar to this kind of technique.

  + remote scanning with a collimated sensor sensitive to radiation to be perceived.

  These last three achievements give a very slow cartography and bad resolution and sensitivity.

  Furthermore, the distance traveled by the beta radiation is low and can not be detected remotely by the above means.

  The optical and electronic device according to the invention makes it possible to remedy these drawbacks, by making it possible, in an unexpected manner, to remotely locate the electromagnetic sources emitting in the field of the extreme UltraViolet and X and gamma, with more sensitivity than the already known means. This is a new kind of X and gamma camera that can take images from a distance and through protections, even weak sources of these invisible radiations.

  In addition, beta emitters, in contact with absorbing materials such as metals or concretes, produce an emission X by bremstrahlung effect. These X-rays travel far enough to be detected by the invention.

  In order to image the aforesaid radiations, the claimed invention uses a bundle or bundle of long hollow or capillary fibers, called the optical beam, associated with a photon detection means.

  A long capillary X, or gamma is a hollow tube, small diameter that guides the X-rays or gamma, following multiple reflections. Diameter: 10 gm to 2 mm and preferably 50 to 500 m; shorter is the wavelength to be observed, the finer must be the capillary.

  Length 2 cm to 50 cm and preferably 5 to 40 cm. The length is in relation to the wavelength of the photons, the material of the fibers, and the definition of the desired image.

  Its claimed photon detection range here is from 10 eV to 200 keV, which corresponds to wavelengths of 115 to 0.006 nm.

  In the presence of a multi-energy source, the most energetic rays, called hard, will be concentrated in the axis of direct view of the capillaries, while the soft rays will spread in halo, around. In a way, this will further highlight the soft rays, which is a plus, of this apparatus.

  The invention uses a package of thousands of these capillaries to form a polycapillary, with an outer diameter of several cm, preferably from 1 to 20 cm. We call this packet an optical beam.

  The material constituting the capillaries and therefore its reflectivity is adapted to the wavelength of the sources to be imaged. Typically it may be borosilicate glass doped or not in barium or lead; it can also be any ductile material that can be easily worked, such as gold, silver, nickel, copper or alloys of these materials. It is also possible to envisage more difficult materials such as tungsten, silicon carbide, boron carbide if it is known to perforate them in the manner of the optical beam described in the invention. The higher the energy of the photons to be captured, the greater the density of the material.

  The transmission of light is affected by the roughness of the walls of the capillary, roughness which causes diffraction phenomena; it is also affected by its length. The inner wall of the capillaries should be as smooth as possible.

  Because this beam is the optics of the imager it must be carefully drawn according to the application.

  It has essentially the shape of a cylinder or truncated pyramid with a square base or preferably a truncated cone. Its broadest base called before is directed towards the source to locate. Its lesser base called back is in contact with the photon detector.

  When the beam is made of glass, the capillaries will be assembled and compressed and stretched in an electric oven once the softening temperature has been reached. Each fiber then takes a tapered shape with a larger diameter front side and a thinner diameter back side. This tapered shape is one of the preferred forms of the embodiment of the invention, including with other materials. The diameter ratio of the capillary at the front to diameter of the capillary at the back will be between 1 and 10 and preferably between 2 and 4 The assembly of several hundred fibers then leads naturally to the overall shape of the cone frustum, the The axis of the capillaries virtually converging at an outer point F. The conical angle of the beam perforations defines the field of view of the optical apparatus.

  Preferably, the large base of the truncated cone, so the front, will be hemispherical; the radius of curvature of this spherical cap will be close to the distance separating the front of the beam from the point of virtual convergence of the capillaries.

  The taper, the nature of the glass or the reflective material will advantageously be adapted to the wavelength and the field width that one wants to capture; likewise, the number of capillaries as well as their diameter, length and thickness are related to the definition or the precision of the image obtained.

  The ratio of the total area perforated on the front surface of the beam is directly related to the sensitivity of the device.

  As we see all these geometric parameters are to optimize for a given application.

  A lid is placed behind or preferentially in front of the optical beam. It is made of low thickness material, from 0.1 to 2 mm, and of low density and preferably made of aluminum or better Beryllium.

  At the rear of the optical beam is applied the photon detector, whose first element is the photoscapillator. It is a thin plate whose thickness is all the stronger as the energy of the photons is high, which converts the incident ultraviolet, X or gamma photons into visible photons; it is called the phosphor screen. Its material is cesium iodide, or sodium iodide. Alternatively, and preferably it consists of a deposit of grains or crystals on a substrate: glass or aluminum ... of Gd2O2S: Tb or CsI: TI.

  Behind the photoscintillator is an electronic photo booster. The light signal created in the scintillator is electronically amplified in this intensifier tube.

  Behind the amplifier is placed an optical fiber bun or tap, intended to reduce the size of the image to match the size of the CCD sensor.

  Behind this image reducer is placed the CCD or CMOS sensor which converts the final image into an electronic signal sent to the image acquisition electronic board of the computer.

  The optical coupling of all these elements can be done by means of a transparent adhesive or an ad hoc gel.

  The image configured on the CCD or CMOS, is conveyed in real time to a computer, and analyzed in a slight delay, by an appropriate imaging software, allowing among other things, to assemble all the light spots coming from each fiber in an image, taking into account the illumination of neighboring fibers. In this way we improve the illumination and the definition of the final image.

  If a single image acquired in the computer is not enough, several tens of images can be accumulated in the memory of the computer or the sensor, to finally be assembled into a synthetic statistical image.

  The whole assembly, except computer, is enclosed and fixed in a support case which, sealed to the luminous radiations, protects by its thickness the photoscintillator and the CCD or CMOS of the parasites X or gamma radiations. Only the front of the case is open on the front of the optical beam and its operculum.

  The attached drawings illustrate the invention: FIG. 1 represents an optical or polycapillary beam of frustoconical shape, the axes of the tapered capillaries converging at point F. FIG. 2 shows an embodiment of the pyramidal optical beam with a square base.

  Figure 3 shows an embodiment of the frustoconical optical beam 30 based on glass capillaries.

  FIG. 4 represents according to a first embodiment of the complete device without its cover and without its protective casing. FIG. 5 schematizes this first embodiment suitably assembling a cap (2), a capillary-based optical beam (1), a photoscintillator (3), a photoamplifier (4), a bun or typing optical fibers. (5), a CCD (6) or a CMOS or an electronic light sensor and a computer (7.

  FIG. 6 shows, according to a second embodiment, the appropriate mounting of a shutter, an optical beam based on capillaries (1) impregnated with a photoscapillator (3), a photoamplifier (4), an optical fiber tap (5), a CCD (6) or a CMOS or an electronic light sensor and a computer (7), preferably the front of the beam, is hemispherical.

  In this particular embodiment, the rear end of the fibers is impregnated with grains or crystals of CsI, or NaI, or Gd2O2S: Tb or CsI: TI, over one or more millimeters. The photoamplifier is then plated directly on the back of the tap. The rest of the device is not different from what is stated above.

  To facilitate the identification and to create a map, this UV, X or Gamma image is converted into false colors reflecting the intensity of the radiation received or the different wavelengths captured and superimposed on a visible image taken at the same time by a camera operating in visible light and axis collinear with that of the device of the invention.

  Two appropriately staggered shots of the same scene will advantageously appear in relief and allow 3D imaging; this eliminates doubt about the exact location at depth of the UV, X or gamma source.

  This invention can be applied industrially and advantageously wherever the need for remote imaging is felt, this covering a wide band of wavelengths, from ultraviolet to hard gamma radiation (from 10 eV to 0.2 MeV) issued directly or from beta sources. It will be sufficient each time to adapt the material, the shape and the perforations of the optical beam, as well as the photoscintillante material. Each time the gain compared to other known systems, will be in terms of sensitivity, compactness, lightness, cost of implementation, easy overlays of images or robustness.

  For example, the Nuclear Decommissioning experiment has shown that the radioactivity responsible for ionizing radiation is rarely evenly distributed. It is often located in specific locations depending on the configuration of the Nuclear Installation, or incidents produced during its operation. By remotely locating these radioactive sources, they can be cleverly processed by appropriate means, such as removals by teleoperated or robotic means, decontamination or setting up screens.

  In the Decontamination procedures, as a second example, the location of radioactive spots is crucial for the time savings, the radioactive exposure of personnel, or simply the cleaning products used and the waste to be stored over long periods of time. that they represent.

  In the operation of a Nuclear Installation, as a third example, the different radioactive sources move and require cartographic monitoring. In a Nuclear Reactor, contaminants move in the Primary Circuit, or diffuse into storage pools before being trapped on ion exchange resin beds. In the reprocessing plants, the enormous radioactivity contained in the fuel rods is released and then treated and separated, before making a new fuel. All these processes can be monitored remotely and through the containment walls, by X or gamma mapping, pertaining to this invention.

  Safety aspects are also required in Wafer etching or in the biomedical field or in industrial control, in order to ensure that no dangerous beam escapes from the UV or X and gamma emitting devices. The invention makes it easy to identify radiation leaks, it will be easy to remedy.

  All of the above description and the drawings below are intended to understand the invention without limiting its scope and potential applications.

Claims (10)

-6-CLAIMS   1+ Optical and electronic device for locating electromagnetic sources of extreme ultraviolet, X or gamma, from 10 eV to 200 KeV or beta sources, characterized in that it comprises for imaging said radiation, an optical beam or beam long hollow or capillary fibers, this beam having the shape of a cylinder or truncated pyramid with a square base or a truncated cone, whose broadest base said front is directed towards the source to locate and whose lesser said rear base is in contact with a photon detector, this beam having an outer diameter of several cm, and preferably 1 to 20 cm and having a length of 2 to 50 cm.   Optical and electronic device for locating electromagnetic sources of extreme ultraviolet, X or gamma, from 10 eV to 200 KeV or beta sources, according to claim 1, characterized in that the capillaries of the optical beam are hollow tubes , of small diameter, from 10 gm to 2 mm and preferably 50 to 500 m, length 2 cm to 50 cm and preferably 5 to 40 cm, their length being related to the wavelength of the photons to be captured, the material of fibers, and the definition of the desired image.   3+ Optical and electronic device for locating electromagnetic sources of extreme ultraviolet, X or gamma, from 10 eV to 200 KeV or beta sources, according to claims 1 and 2, characterized in that the hair fibers have a tapered shape with a larger diameter on the front side and a thinner diameter on the back side, the diameter ratio of the capillary at the front to diameter of the capillary at the back being between 1 and 10 and preferably between 2 and 4.   4+ Optical and electronic device for locating electromagnetic sources of extreme ultraviolet, X or gamma, from 10 eV to 200 KeV or beta sources, according to claims 1 and 2, characterized in that the optical beam capillaries are in borosilicate glass, whether or not doped with barium or lead, or ductile material that can be easily worked, such as gold, silver, nickel, copper or alloys of these materials or more difficult materials such as that tungsten, silicon carbide, boron carbide if it is known to perforate them in the manner of the optical beam described in the invention, said material being selected according to the energy of the photons to be captured.   5+ Optical and electronic device for locating electromagnetic sources of extreme ultraviolet, X or gamma, from 10 eV to 200 KeV or beta sources, characterized in that it comprises, according to a first embodiment, the addition appropriately , a sealing operculum to visible light, a capillary-based optical beam according to Claims 1,2, and 4, a photon detector consisting of a photo-scintillator, a photoamplifier, a a bun or tap of optical fibers, a CCD (coupled coupled device) or a CMOS (Compementary Metal Oxide Semiconductor) and a computer, the entire assembly, excluding computer, being enclosed and fixed in a a support case which, sealed to the luminous radiations, protects the photoscinterillator and the CCD or CMOS from parasitic X or gamma radiation by its thickness, the front only of the case being open on the front of the optical beam and its operculum.   6+ Optical and electronic device for locating electromagnetic sources of extreme ultraviolet, X or gamma, from 10 eV to 200 KeV or beta sources, characterized in that it comprises in the appropriate addition, a lid visible light-tight, of a capillary-based optical beam according to Claims 1,2,3,4 whose rear end is impregnated with a photoscintillante material and preferably grains or crystals of CsI, or NaI, or Gd2O2S: Tb or CsI: TI, over one or more millimeters, the said optical beam being further added to a photoamplifier, an optical fiber tap, a CCD (coupled coupled device) or a CMOS (Complementary Metal Oxide Semi-Conductor) and a computer, the whole assembly, except computer, being enclosed and fixed in a support case which, sealed to the luminous radiations, protects by its thickness the photoscintillator and the CCD or CMOS of the radiatio X or gamma parasites, the front only of the housing being open on the front of the optical beam and its operculum.   7+ An optical and electronic device for locating electromagnetic sources of extreme ultraviolet, X or gamma, from 10 eV to 200 KeV or beta sources, according to claims 5 or 6 characterized in that the image configured on the CCD or CMOS, is routed in real time to a computer, analyzed in light deferred, by appropriate imaging software, allowing among other things, to assemble all the light spots from each fiber into an image, while taking into account the illumination of adjacent fibers, several tens of images that can be accumulated in the memory of the computer or the sensor, to finally be assembled into a synthetic statistical image.   8+ Optical and electronic device for locating electromagnetic sources of extreme ultraviolet, X or gamma, from 10 eV to 200 KeV or beta sources, according to claims 5 or 6 or 7, characterized in that to facilitate the locations, the UV, X or Gamma image is translated into false colors representing the intensity of the radiation received or the different wavelengths captured, and in that the said image is superimposed on a visible image taken at the same time by a device photo operating in visible light and axis collinear with that of the device of the invention.   9+ An optical and electronic device for locating electromagnetic sources of extreme ultraviolet, X or gamma, from 10 eV to 200 KeV or beta sources, according to claims 5 or 6 or 7 or 8, characterized in that two lenses of the same scene with an appropriate offset, will advantageously appear in relief and allow so-called 3D imaging to remove the doubt about the exact location in depth, the UV source, X or gamma, or beta.   Optical device according to the preceding claims used to locate electromagnetic sources of extreme ultraviolet, X or gamma, from 10 eV to 200 KeV or beta sources, in the Nuclear Industry Decontamination, Operation or Security, in the biomedical field, in industrial control, or in the engraving of Wafers, the invention making it possible to ensure that no dangerous beam escapes from the UV or X and gamma emitting devices, and thus facilitating the corrective actions.