Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V5/00—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
  • G01V5/20—Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects
  • G01V5/22—Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
  • G01V5/226—Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays using tomography
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V5/00—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
  • G01V5/20—Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects
  • G01V5/22—Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays

Definitions

• the present invention has application in the technical field of measuring instruments and it relates to an apparatus for non-invasive inspection of solid bodies by muon imaging usable in civil engineering, archeology, volcanology, tectonics and everywhere a radiographic and/or tomographic non-destructive inspection of geological and/or engineering structures, even of large dimensions, is necessary
• the invention further relates to a method for non-invasive inspection by muon imaging implementable by said apparatus.
• Such techniques are based on displaying the trajectory of the particle that while passing through detection planes, usually scintillating planes, produce an electric pulse that, once suitably analysed, gives the direction of origin of the particle.
• the muon "tracking" techniques for radiography/tomography of massive objects exploit the high penetrability of muons and their contemporaneous energy loss through the electromagnetic interactions in the crossed material, since energy absorption depends on thickness and density of the crossed material and on energy of the incident muon. Therefore the outgoing muon has energy lower than the incident one and moreover it deflects from the original direction due to many small angle deflections occurring when crossing (Coulomb scattering).
• the mean deflection angle is proportional to the inverse of momentum of the particle and to the square root of the real density of the material measured in radiation lengths.
• the known geophysical survey techniques provide to use telescopes with scintillator bars read by light detectors such as photomultipliers or silicon photomultipliers that intercept the muons coming out from the volcano, such as described for example in JP20060096285.
• JP2010101892 describes a measuring techniques applied in the volcanology field based on detecting muon tracks passing through scintillator plane endoscopes.
• the object of the present invention is to overcome the above mentioned drawbacks, by providing an apparatus for non-invasive inspection of solid bodies by muon imaging that is particularly efficient and quite cheap.
• a particular object is to provide an apparatus for non-invasive inspection of solid bodies by muon imaging allowing radiography and/or tomography of structures, even of large dimensions, to be reliably carried out, while minimizing errors and while taking considerably less time than known techniques.
• Still another object is to provide an apparatus for non-invasive inspection of solid bodies by muon imaging having considerably reduced encumbrances and weights such to be possibly transported and such to allow radiography and/or tomography investigations of large bodies, such as volcanos, in a rapid and reliable manner.
• Still another object is to provide an apparatus for non-invasive inspection of solid bodies by muon imaging that is flexible to be used.
• a further object is to provide a method for non-invasive inspection of solid bodies by muon imaging that is particularly reliable and cheap and that allows systemic errors and false positives to be minimized.
• an apparatus for non-invasive inspection of solid bodies by muon imaging that, according to claim 1, comprises a receiver adapted to intercept a muon flux associated with cosmic rays passing through a portion of a body to be inspected, sensor means adapted to detect the amount of photons or Cherenkov radiation associated with the intercepted muon flux, electronic processing means adapted to reconstruct energy and direction of the muon flux incident the portion of the body to be inspected to calculate the local density thereof.
• the receiver comprises an optical device provided with at least one receiving surface having reflecting and/or diffractive properties adapted to convey the Cherenkov radiation associated with muons toward said sensor means.
• Sensor means in turn comprise a multipixel detection chamber adapted to provide an annular image of the muon having radius and position variable as a function of the energy and direction of the muon flux.
• the investigation is based on the analysis and reconstruction of the Cherenkov ring image, that is a well-established and efficient technique.
• the measurement of the muon energy allows also the absorption inside the object to be evaluated and therefore allows the real path of the muon inside the object to be efficaciously determined.
• a further advantage is the fact that no active elements are required for detecting the muon, such as for example plastic scintillators, since atmosphere is the muon- Cherenkov photons conversion medium.
• said detection chamber can be arranged at the focal plane of said receiver optical device.
• the optical device can comprise a primary receiving surface intended to convey the flux of Cherenkov photons toward said focal plane.
• the optical device can be of the type with double reflection and/or diffraction with a secondary receiving surface facing and aligned with said primary receiving surface for transferring the flux of photons received by the latter and for concentrating it toward said detection chamber facing said secondary reflecting or diffractive surface.
• the apparatus can comprise a plurality of said optical devices associated to respective sensor means and to respective electronic processing means to detect muon fluxes coming from different directions, at least one of said optical devices being movable to vary its detection direction.
• FIG. 1 is a schematic view of an apparatus according to the invention
• FIG. 2 is the image of a muon generated by the apparatus in two different impact conditions of the muon
• FIG. 3 is a schematic view of an optical device belonging to the apparatus according to a preferred configuration
• FIG. 4 is a graph about the spot diagram and fraction of photons enclosed in the image for some angles of the focus range as a function of the radius measured with respect to the center of the image.
• FIG.l schematically shows a preferred arrangement of an apparatus of the movable type, generally denoted by 1, namely mounted into a movable structure 2 such to be easily transported and placed in different detection areas.
• the apparatus 1 thus can be used both for 2D radiography and 3D tomography, possibly in a system comprising two or more apparatuses according to the invention, not necessarily similar to each other.
• the apparatus 1 essentially comprises a receiver 3 adapted to intercept a muon flux associated with cosmic rays passing through a portion of a body to be inspected, sensor means 4 adapted to detect the amount of photons or Cherenkov radiation associated with the intercepted muon flux and electronic processing means, not visible since they are embedded into the mechanical structure of the sensor means, adapted to reconstruct energy and direction of the muon flux incident the portion of the body to be inspected to calculate the local density thereof.
• the receiver 3 comprises an optical device 5 provided with at least one receiving surface 6 having reflecting properties adapted to convey the Cherenkov radiation associated with muons toward the sensor means.
• the reflecting surface 6 belongs to a mirror 7 suitably designed for intercepting the muon flux and to direct it towards the sensor means 4.
• These latter comprise a multipixel detection chamber 8 arranged at the focal plane of the receiving optical device 5 and adapted to provide an annular image of the muon having radius and position variable as a function of the energy and direction of muon flux.
• Fig.2 shows the typical annular image of a muon as processed by a multipixel chamber 8. Particularly the image on the left shows the case when a muon impacts the receiving surface, while the image on the right shows the case when the impact point of the muon is outside the receiving surface.
• the optical device 5 is of the double-mirror type, with a primary mirror 7 and a secondary mirror 9 having respective reflecting surfaces.
• the primary reflecting receiving surface 6 is intended to intercept the flux of Cherenkov photons and to convey it on the secondary reflecting surface 10 facing and aligned with the primary receiving surface 6.
• the sensor means 4 are interposed between the two reflecting surfaces 6, 10 with the relevant detection chamber 8 facing the secondary reflecting surface 10 such to obtain the alignment of the focal plane.
• Such alignment can be obtained by a suitable mechanical support structure 11 that allows the mirrors 7, 9 and the chamber 8 to be mutually fastened in addition to allow the apparatus 1 to be fastened to the holding structure 2.
• the secondary receiving surface 10 of the reflecting type thus can transfer the flux of photons received by the primary surface 6 and concentrate it towards the detection chamber 8 facing it.
• Fig. 3 schematically shows a possible configuration of the Schwarzschild-Couder type wherein the two receiving surfaces 6, 10 are defined by two aspheric mirrors 7, 9 designed to correct spherical aberrations and coma.
• Such configuration allows an observational focus range to be provided between 10° and 15° and preferably close to 12°, such to have a greater resolution.
• the primary mirror 7 can be composed of 8 segments forming a primary reflecting surface 6 with a diameter of 2100 mm.
• the secondary mirror 9 is monolithic with a diameter of 800 mm.
• the distance between the primary mirror 7 and the secondary mirror 9 is 1600 mm, with the chamber 8 placed at a distance of 275 mm from the secondary mirror 9.
• Fig.4 shows some graphs about the spot diagram and the fraction of photons enclosed in the image for some angles of the focus range as a function of the linear dimension (radius) measured with respect to the center of the image.
• the Schwarzschild-Couder configuration has the advantage of reducing encumbrances and of obtaining a high collimation but it is not an exclusive configuration.
• Fresnel lenses also made of plastic material, with the advantage of further reducing the weight of the apparatus 1, improving the transportability thereof.
• configurations the receiving surfaces 6,10 can be of the diffractive type.
• mirrors 7, 9 it is possible to use two suitably designed lenses to convey the muon flux towards a focal plane where the chamber 8 will be arranged.
• the sensor means 4 with the relevant detection chamber 8 will be placed at the focus of the secondary lens.
• Hybrid configurations are also possible, wherein a receiving surface is a reflecting mirror while the other one is a refractive lens.
• the apparatus 1 can be composed of a system provided with a plurality of optical devices associated to respective sensor means and respective electronic processing means to detect muon fluxes coming from different directions, such to carry out 3D tomography.
• the optical devices have not to be necessarily of the same type and preferably at least one of them can be inserted in a movable structure, possibly autonomous from an energy perspective, to vary its detection direction.
• the multiplex chamber 8 can comprise photon sensors of the siPm type, photomultipliers or the like intended to generate analog signals as a function of the incident photon and of the direction of the muon flux to be sent to electronic processing means that provide to convert them into digital signals by a suitable processing unit.
• the electronic processing means are intended to detect the signal of Cherenkov radiation and to carry out an analysis intended to measure the differential attenuation and the energy of the muon flux passing through the portion inspected along different directions and thus to determine the local density of the inspected body
• the detection chamber 8 is essentially composed of a mechanical structure, whose main function is to contain all the electronic components, and the real electronic components, among which the voltage distribution module, detectors, image processor and command and data communication module.
• the mechanical structure of the detection chamber 8 has a cylindrical shape with diameter size of 300 mm and height size of 300 mm and it opportunely comprises a transparent window for reflected or diffracted photons to enter and a mechanical interface flange for the connection to the support structure 11 of the optical device 5.
• the electronics of the chamber 8 comprises SiPM sensors, front-end electronics and back-end electronics.
• front-end electronics The main role of front-end electronics is to process analog signals of SiPMs into digital signals, while back-end electronics manages and controls the overall behavior of the system, including the reading and management of data by a FPGA ⁇ Field Programmable Gate Array).
• the back-end electronics further provides all the functions necessary to process and transmit to an external computer the whole stream of data including status information of the system such as for example, temperatures and voltages.
• the focal plane of the chamber 8 is of the modular type, for example composed of 16 modules of dimensions 57mm*57mm*30mm.
• Each module contains the board with SiPMs (8 pixels*8 pixels), the ASIC board reading and processing the signals of SiPMs and the FPGA board controlling and managing all the operating functions of the front-end electronics.
• Boards of each module can be mechanically fastened to a metal casing, for example made of aluminium, and connected with each other by means of connectors.
• the 16 modules are geometrically arranged in a grid containing 4*4 modules and will be mechanically fastened to an aluminium support for a 228mm*228mm dimension.
• the back-end electronics is the system processor and has to be able to receive and process data at a speed higher than that of the triggered events.
• Back-end electronics is based on a FPGA that controls and monitors the stream of data and commands for/to the electronics of the focal plane.
• a voltage distribution board provides necessary voltages to the different modules by using a single input voltage of 24 V.
• the board provides to independently enable/disable each sub-system connected thereto.
• a data acquisition system for example a portable PC connected to the back-end board through a Ethernet cable from which commands are sent and data are received.
• the chamber 8 can be designed also in a different manner, for example with a different number of modules and/or with a different arrangement in the space thereof, without departing from the scope of protection of the present invention.

Landscapes

• Physics & Mathematics (AREA)
• High Energy & Nuclear Physics (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• General Physics & Mathematics (AREA)
• Geophysics (AREA)
• Analysing Materials By The Use Of Radiation (AREA)
• Measurement Of Radiation (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Radiology & Medical Imaging (AREA)
• Geophysics And Detection Of Objects (AREA)
• Transforming Light Signals Into Electric Signals (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (2)

Family

ID=55538366

Family Applications (1)

Country Status (6)

Families Citing this family (5)

Family Cites Families (11)

• 2015
  • 2015-11-23 IT ITUB2015A005808A patent/ITUB20155808A1/it unknown
• 2016
  • 2016-11-17 ES ES16856465T patent/ES2827957T3/es active Active
  • 2016-11-17 US US15/778,580 patent/US10371855B2/en active Active
  • 2016-11-17 EP EP16856465.6A patent/EP3380875B1/en active Active
  • 2016-11-17 JP JP2018524813A patent/JP6994460B2/ja active Active
  • 2016-11-17 WO PCT/IB2016/056937 patent/WO2017089932A2/en not_active Ceased

Also Published As

Similar Documents

Legal Events