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EP-4479486-B1 - ORGANIC SCINTILLATOR

EP4479486B1EP 4479486 B1EP4479486 B1EP 4479486B1EP-4479486-B1

Inventors

  • MATTIELLO, LEONARDO
  • PATERA, Vincenzo
  • BELARDINI, ALESSANDRO
  • ROCCO, Daniele
  • MARAFINI, Michela

Dates

Publication Date
20260506
Application Date
20230217

Claims (9)

  1. A scintillator characterized by a transparent polymeric matrix and comprising one or more primary dopants selected from among fluorenic compounds having the following general formula (M1): Wherein: X = 2-naphthyl, 1-naphthyl, 2-biphenyl, 4-tolyl; R = C 8 H 17 and wherein said one or more primary dopants are present in an amount of 5-30% by weight with respect to the polymeric matrix, the fluorenic compounds including, in particular, the compounds having formulas (1N), (2B), (2N), and (2T).
  2. The scintillator according to claims 1 wherein the polymeric matrix is selected from polystyrene, cross-linked polystyrene, poly(vinyl-toluene) and polyvinylpyrrolidone.
  3. The scintillator according to any one of claims 1-2 further comprising a secondary dopant, preferably 7-diethylamino-4-methylcoumarin.
  4. The scintillator according to any one of claims 1-3 characterized by a rise time lower than 350 ps, a pulse width lower than 20 ns, against a Light yield (LO) of about 55% or higher as compared to anthracene, the parameters being measured as described in the description.
  5. The scintillator according to claim 4 characterized by a time resolution lower than 120 ps, preferably lower than 100 ps determined as described in the description.
  6. A fluorenic compound selected from the compounds having the formulas:
  7. A particle detection device which uses the scintillator of the preceding claims.
  8. The detection device according to claim 7 wherein the particles are selected from: electrons, photons, protons, leptons and hadrons.
  9. Use of the fluorenic compound of claim 6 as primary dopants in plastic organic scintillators.

Description

Technical field The present invention relates to organic scintillators, more particularly to solid and liquid organic scintillators. The invention also relates to chemical compounds which can be used in organic scintillators. Background Scintillators are mainly used in physics as particle detectors, mainly to detect charged and neutral particles. They are used for the simple counting of particles or, for instance, for measuring the time of flight, from which it is possible to obtain the speed of the particle and its mass. Scintillators can also be used in neutron physics, X-ray protection, nuclear monitoring, and gas detection. Other applications of scintillators include CT (Computed Tomography) scanners and gamma ray cameras used in medical imaging. The use of a scintillator in combination with a photomultiplier tube is widely used in handheld remote measurement devices used for the detection and measurement of radioactivity and for monitoring nuclear material. Scintillation detectors are used in the petroleum industry as detectors for gamma rays. A particle passing through the scintillator loses energy by transferring it to the latter with physical mechanisms which is then followed by the emission of photons. In amorphous (plastic, liquid) scintillators, the energy transferred is used to excite the molecules it is made of, which, when de-excited, emit photons with an exponential time pattern. In the most common scintillators, the emission occurs mainly in the violet, with times ranging from nanoseconds to microseconds. These photons are then transmitted, through a suitable light guide, to the photocathode of the photomultiplier. Here the photons release, by photoelectric effect, electrons, which are then accelerated and focused on the first dynode. The ratio between the number of photoelectrons produced and the number of photons incident on the photocathode is called "quantum efficiency of the photocathode". For every primary photoelectron that collides with a dynode, 2 to 5 secondary photoelectrons can be emitted. By introducing, for instance, 14 multiplication stages, multiplication factors of about one billion are reached. The collected charge (pulse integral) and the pulse amplitude are proportional to the energy deposited in the scintillator. Scintillators can be organic or inorganic. A scintillator is a material which exhibits the phenomenon of scintillation (the property of luminescence) when excited by ionizing radiation. Luminescent materials, when struck by a particle, absorb its energy and sparkle (that is, they release the absorbed energy in the form of light). A scintillation detector or scintillation counter is obtained when a scintillator is coupled to an electronic light sensor such as a photomultiplier tube (PMT), photodiode or silicon photomultiplier (SiPM). PMTs absorb the light emitted by the scintillator and emit it in the form of electrons through the photoelectric effect. Subsequent multiplication of those electrons (sometimes called photoelectrons) produces an electrical impulse that can then be analyzed and provide meaningful information about the particle that originally hit the scintillator. A plastic scintillator is formed by a solution of organic scintillating material dissolved in a solvent which is subsequently polymerised, thus becoming a solid solution. Very often a secondary solute is also added due to its "shifting" properties of the wavelength of the light produced. Plastic scintillators offer a very fast signal with a decay constant of about 2-3 ns and a light output proportional to the energy release. One of the major advantages of plastic scintillators is their flexibility, which makes them easy to manipulate; their not excessive cost makes them particularly useful if large volumes of scintillators are required. Plastic scintillators used in high energy physics are solutions of fluorophores in a plastic matrix based on aromatic compounds. Virtually all plastic scintillators contain polyvinyltoluene, polystyrene, or acrylic polymers as a base. Acrylic is non-aromatic and therefore has a very low scintillation efficiency. It becomes acceptable when naphthalene is dissolved in percentages of the order of 5-20%. The plastic matrix represents the component sensitive to ionization (i.e. the "scintillator"). In the absence of a shifter, the base would emit UV light with a low attenuation length (a few mm). To obtain longer attenuation lengths a fluorophore in high concentrations (1 wt% or more) is dissolved in the plastic matrix. https://physicsopenlab.org/2017/08/10/cristalli-scintillatori/. The operation principle of plastic scintillators consists in the absorption of the energy of the incident radiation by an inexpensive polymer matrix [for instance, poly(vinyltoluene) (PVT)] followed by a subsequent rapid transfer of this energy to a fluorescent primary dopant. Sometimes, to minimize self-absorption phenomena of the primary dopant, a secondary dopant (wavelength shifter