FR3075977A1 - PLASTIC SCINTILLATOR DEVICE WITH PIECE COMPRISING SCINTILLATING HYBRID MATERIAL, ASSOCIATED MANUFACTURING AND MEASUREMENT METHOD, AND APPARATUS. - Google Patents

Abstract

Device for detection by plastic scintillation comprising a part composed wholly or partly of a hybrid material comprising: - a polymer matrix; and, - a fluorescent mixture incorporated into the polymer matrix and comprising i) 80% to 99.6% molar of a main primary fluorophore consisting of naphthalene and ii) 0.4% to 20% molar of an additional primary fluorophore of which the centroid of the light absorption spectrum and of the fluorescence emission spectrum, the fluorescence decay constant and the fluorescence quantum yield are carefully chosen; the part being coupled to an electronic acquisition module capable of collecting the radioluminescent radiation emitted by the part when it is in contact with ionizing radiation or an ionizing particle. The fluorescence decay constant of the hybrid material making up the part of the device is intermediate between that of a fast plastic scintillator material and of a slow plastic scintillator material. Also, it can be chosen from a wide range. The invention also relates to the associated manufacturing and measuring method and to an apparatus comprising the device.

Description

PLASTIC SCINTILLATOR DEVICE WITH PART COMPRISING HYBRID SCINTILLING MATERIAL, METHOD FOR MANUFACTURING AND MEASURING THEREOF, AND APPARATUS.

DESCRIPTION

TECHNICAL AREA

The present invention belongs to the field of radioactivity measurement by the plastic scintillation technique. The invention relates more particularly to a material for measurement by plastic scintillation, a part comprising the material and its associated measuring device or apparatus, a polymerization composition, the kits for manufacturing the material, the associated manufacturing methods, as well as the plastic scintillation measurement method using the device.

TECHNICAL BACKGROUND

Measurement by plastic scintillation consists in determining the presence and / or the quantity of one or more radioactive materials, in particular in physics, geology, biology, medicine, for dating, environmental monitoring or control of non- proliferation of nuclear weapons.

In practice, the radioactive material emitting ionizing radiation or an ionizing particle (alpha particle, electron, positron, photon, neutron, ...) is exposed to a scintillating material called "plastic scintillator" which converts the energy deposit from the radiation / matter interaction into a light radiation (called radioluminescent) measurable by a gain photon-electron converter, such as a photomultiplier.

The plastic scintillator has been known since the middle of the 20th century. It is described for example in the document “Moser, S. W.; Harder, W. F .; Hurlbut, C. R .; Kusner, M. R.; "Principles and practice of plastic scintillator design", Radiat. Phys. Chem., 1993, Vol. 41, No. 1/2, 31-36 "[reference 1] and" Bertrand, G. H. V.; Hamel, M.; Sguerra, F.; "Current status on plastic scintillators modifications", Chem. Eur. J., 2014, 20, 15660-15685 ”[reference 2]. It is generally in the form of a polymer matrix into which a primary fluorophore or even a secondary fluorophore is inserted. A fluorophore is a chemical compound capable of emitting visible fluorescent light after excitation by photons or other incident particles. The primary fluorophore and the secondary fluorophore consist of an aromatic molecule with fluorescent properties (molecule called fluorophore) allowing detection by scintillation.

The main function of the polymer matrix is to be a support capable of receiving the energy of the ionizing radiation or of the ionizing particle. After recombination of the excited and / or ionized species which then form, this energy is converted into radioluminescent radiation and then transferred to the primary fluorophore and possibly to the secondary fluorophore, which can increase the wavelength of the radiation emitted by the primary fluorophore in order to d '' improve detection.

A particular plastic scintillator of phoswich type (Anglo-Saxon neologism resulting from the combination of the terms phosphorus and sandwich generally translated by meaning "scintillator in sandwich") was proposed from the beginning of the development of plastic scintillators in the document "Wilkinson DH," The Phoswich - A Multiple Phosphor ", Rev. Sci. Instruir. 1952, 23, 414-417. »[Reference 3].

In order to obtain new scintillation properties, a phoswich scintillator combines at least two compartments: a compartment comprising a slow scintillator on the one hand (constant of high fluorescence decay, generally between 200 ns and 1000 ns) and another compartment comprising a rapid scintillator (much lower fluorescence decay constant, generally between 2 ns and 7 ns on the other hand).

Such a scintillator nevertheless poses at least one of the following problems: the difference between the fluorescence decay constant of the fast compartment and that of the slow compartment is too small: the separation of the scintillation pulses between these stages is then not possible electronically; the difference between the fluorescence decay constant of the fast compartment and that of the slow compartment is too large: the scintillation pulse of the slow scintillator may be partially or completely masked in the electronic background noise of the acquisition device. flickering impulse, which leads to erroneous values. the acquisition of the luminescent signal is carried out over a period which is typically about 6 to 10 times the fluorescence decay constant of the slow compartment. In the event of a high counting rate due to the multiplicity of ionizing particles or the high intensity of ionizing radiation in interaction with the phoswich scintillator, the probability of stacking (i.e. two pulses present in the same time window d 'acquisition) of scintillation pulses becomes more and more important. As a result, it is possible that several pulses appear in the same acquisition time window, which causes rejection of the stacks by phenomenon of saturation of the acquisition electronics, and therefore an underestimation of the counting rate;

STATEMENT OF THE INVENTION

One of the aims of the invention is therefore to avoid or alleviate one or more of the drawbacks described above, by proposing a new type of material constituting a plastic scintillator called “hybrid material”.

The present invention relates to a hybrid material for measurement by plastic scintillation comprising (or even consisting of): - a polymer matrix; and, a fluorescent mixture incorporated into the polymer matrix and comprising in molar concentration relative to the total number of moles of primary fluorophore in the incorporated fluorescent mixture i) 80% to 99.6 mol% of a main primary fluorophore consisting of naphthalene and ii) 0.4% to 20 mol% of an additional primary fluorophore, the centroid of the light absorption spectrum and the fluorescence emission spectrum of which have respectively a wavelength between 250 nm and 340 nm and between 330 nm and 380 nm, the fluorescence decay constant is between 1 ns and 10 ns, and the quantum yield of fluorescence in an apolar solvent is greater than 0.2, typically between 0.2 and 1; preferably greater than 0.5, typically between 0.5 and 1.

A nonpolar solvent suitable for measuring the quantum fluorescence yield is, for example, cyclohexane, toluene, dichloromethane, xylene or any xylene isomer.

The material for plastic scintillation measurement according to the invention can also be designated in the present description by the expression "plastic scintillator". It is said to be “hybrid” because its fluorescence decay constant is intermediate between that of a fast plastic scintillator and a slow plastic scintillator. Advantageously, the value of this constant can also be chosen optimally during the manufacture of the hybrid material in an intermediate range between 10 ns and 90 ns (preferably between 15 ns and 80 ns), from values between these two extremes which, to the knowledge of the inventor, are not obtained with the plastic scintillators currently marketed.

This temporal tunability of the fluorescence decay constant of the hybrid material is made possible by the use of a specific fluorescent mixture. This mixture is characterized in particular by the combined choice of naphthalene as the main primary fluorophore and an additional primary fluorophore with specific photophysical properties, as well as by the choice of a defined concentration ratio between these two primary fluorophores.

Unexpectedly, as shown by the exemplary embodiments, the primary primary fluorophore and the additional primary fluorophore act in synergy to vary very significantly, while using a reduced concentration range for the additional primary fluorophore, the fluorescence decay constant . In addition, the relative simplicity of this system which essentially requires this combination between these two primary fluorophores avoids the addition of an additional molecule possibly disruptive or expensive. These advantageous properties make the hybrid material of the invention a particularly effective material for measurement in plastic scintillation and which can be easily produced on an industrial scale at a moderate cost. Contrary to the improvement paths followed by the state of the art, the invention does not consist in the use of a new polymer matrix, the addition of additive to the plastic scintillator or the development as primary fluorophore of new families of molecules (“quantum dots”, organometallic complexes, nanoparticles, etc.) in order to overcome at least one of the aforementioned drawbacks, but identifies the fluorescent mixture of the invention which allows access to a material hybrid. All the characteristics necessary for the material for plastic scintillation measurement according to the invention can thus be essentially limited to a polymer matrix and to the incorporated fluorescent mixture. The composition of the plastic scintillator is thus simplified by overcoming the difficulty of very precisely determining the adequate proportion between a primary fluorophore and a secondary fluorophore with a view to obtaining radioluminescence radiation and a fluorescence decay constant which are optimized. At the molecular level, the plastic scintillator of the invention can be considered as a pseudo liquid, since the chains of the polymers constituting all or part of the polymer matrix are labile and allow a certain freedom of movement to the various constituents of the plastic scintillator. At the macroscopic scale, the plastic scintillator nevertheless retains sufficient mechanical strength in order to manufacture a part for scintillation detection. The invention is completed by the following objects and / or characteristics, taken alone or according to any of their technically possible combinations.

In the present description of the invention, a verb such as "understand", "incorporate", "include", "contain" and its conjugate forms are open terms and therefore do not exclude the presence of element (s) and / or additional step (s) in addition to the initial element (s) and / or step (s) stated after these terms. However, these open terms also refer to a particular embodiment in which only the element (s) and / or initial step (s), to the exclusion of any other, are targeted; in which case the term open also refers to the closed term "consist in", "constitute", "compose of" and its conjugate forms. The use of the indefinite article "a" or "an" for an element or a stage does not exclude, unless otherwise stated, the presence of a plurality of elements or stages.

Any reference sign in parentheses in the claims should not be interpreted as limiting the scope of the invention. The expression “according to one or more of the variants described in the present description” for a material / element, refers in particular to the variants which relate to the chemical composition and / or the proportion of the constituents of this material and of any additional chemical species which 'It may possibly contain and in particular to the variants which relate to the chemical composition, the structure, the geometry, the arrangement in space and / or the chemical composition of this element or of a constituent sub-element of the element. These variants are, for example, those indicated in the claims.

In addition, unless otherwise indicated: the terminal values are included in the ranges of parameters indicated; the temperatures indicated are considered for application at atmospheric pressure; any mass percentage of a component of the plastic scintillator refers to the total mass of the plastic scintillator, the rest being constituted by the polymer matrix.

The polymer matrix of the hybrid material of the invention consists entirely or in part of at least one polymer comprising repeating units resulting from the polymerization of monomers or oligomers (which can themselves come from the polymerization of monomers). The chemical structure of the repeating units is therefore close to the chemical structure of the monomers, the latter having only been modified by the polymerization reaction. In the present description, a polymer is a general term which can respectively designate a homopolymer or a copolymer, namely a polymer which can comprise repeating units of identical or different chemical structure.

The monomer or oligomer comprises for example at least one aromatic group (in particular for exploiting its photophysical properties), (meth) acrylic (namely acrylic or methacrylic) or vinyl. A polymerizable group can be a group comprising an unsaturated ethylene carbon-carbon double bond, such as for example the (meth) acrylic or vinyl group. In addition, this polymerizable group must be capable of being polymerized according to a radical polymerization.

More specifically, at least one monomer can be chosen from styrene, vinyltoluene, vinylxylene, 1-vinylbiphenyl, 2-vinylbiphenyl, 1-vinylnaphthalene, 2-vinylnaphthalene, 1-methylnaphthalene, N-vinylcarbazole, methyl (meth) acrylate, (meth) acrylic acid or 2-hydroxyethyl (meth) acrylate, or even more generally an alkyl methacrylate in which the linear or branched alkyl group contains between 1 and 20 carbon atoms.

Preferably, the monomer is styrene or vinyltoluene in order to form the corresponding homopolymer.

Advantageously, the monomer can be chosen more particularly from a molecule with particular fluorescence properties, for example 1-vinylbiphenyl, 2-vinylbiphenyl, 1-vinylnaphthalene, 2-vinylnaphthalene, 1-methylnaphthalene, 2V- vinylcarbazole or mixtures thereof.

The polymer matrix may consist wholly or in part (preferably more than 10% by weight of polymer in the polymer matrix) of at least one crosslinked polymer (for example by means of a crosslinking agent) in which chains polymers are linked together by crosslinking bridges, in particular to improve the mechanical and / or scintillation properties. The crosslinking agent can be a monomer comprising at least two polymerizable functions capable, after polymerization, of forming a bridge between two polymer chains. It can be chosen from divinylbenzene, an alkyl diacrylate or dimethacrylate, the hydrogen carbon chain of the latter two containing between 2 and 20 carbon atoms.

Preferably, the crosslinking agent is 1,4-butanediyl dimethacrylate or divinylbenzene.

After polymerization of the crosslinked polymer, in addition to the aforementioned repeating units, the copolymer obtained can comprise repeating units resulting from the polymerization of the crosslinking agent.

Concerning one of the other main constituents of the hybrid material of the invention that is the fluorescent mixture incorporated in the polymer matrix, the hybrid material can comprise 1% by mass to 25% by mass of the fluorescent mixture incorporated, or even 1% by mass at 5% by mass of the fluorescent mixture incorporated relative to the total mass of hybrid material. Above a mass concentration of 25%, exudation can occur, namely a seepage of the fluorescent mixture out of the plastic scintillator.

The mass concentration of the fluorescent mixture incorporated in the hybrid material can be easily calculated by determining the mass of the polymer matrix.

One of the methods of a person skilled in the art is as follows: the molar concentration of the monomers and of the oligomers in the polymerization medium is known in advance or can be determined by a quantitative measurement method such as UV spectrophotometry. The corresponding mass concentration is then calculated from the molecular weights. However, the monomers, the oligomers or their mixtures form the polymer matrix according to a polymerization yield which can be measured before, but which is generally greater than 95%, even 98%, or even most often equal to 100%. Consequently, the mass proportion of the monomers and of the oligomers present in the polymer matrix is equivalent to this reaction yield multiplied by the mass concentration previously determined. Those skilled in the art can therefore easily, using their general knowledge, convert a mass concentration into a molar concentration for all the constituents of the hybrid material.

The mass or molar percentages of the incorporated fluorescent mixture, of the primary primary fluorophore, of the additional primary fluorophore, of the secondary fluorophore or of an additional compound can be determined a posteriori in the hybrid material by an analysis technique such as for example Resonance Nuclear Magnetic (NMR) of the solid. Another technique consists in dissolving the plastic scintillator in dichloromethane, precipitating in methanol the polymer constituting the polymer matrix, filtering the mixture obtained to recover the molecule whose concentration is to be measured, then quantifying it by elemental analysis with detection of a specific atom constituting this molecule. The incorporation of the fluorescent mixture into the polymer matrix can be carried out according to several embodiments. In particular, at least one fluorescent molecule chosen from the main primary fluorophore, the additional primary fluorophore or their mixtures can be incorporated into the polymer matrix by dispersion or by grafting of this molecule in the polymer matrix. In the case of grafting, the fluorescent molecule (generally the additional primary fluorophore) is covalently linked to the polymer matrix. This covalent bond is formed for example during the manufacture by polymerization of the polymer matrix, the fluorescent molecule comprising at least one polymerizable function.

Optionally, the hybrid material of the invention may contain one or more materials which have no significant impact on the measurement by plastic scintillation with the hybrid material of the invention or which improve some of its properties. Like the incorporated fluorescent mixture, these materials are generally dispersed homogeneously or not in the hybrid material.

The decay constant of the hybrid material of the invention is imparted by that of the incorporated fluorescent mixture. Thus, the incorporated fluorescent mixture, and therefore the hybrid material, can have a fluorescence decay constant of between 10 ns and 90 ns, or even between 15 ns and 80 ns, advantageously between 30 ns and 80 ns.

Preferably, the incorporated fluorescent mixture comprises 90% to 99.1% molar of the main primary fluorophore, even more preferably 96% to 99.1% molar of the main primary fluorophore: this judiciously chosen concentration of main primary fluorophore and the additional concentration of fluorophore additional primer gives the incorporated fluorescent mixture, and therefore the hybrid material, a fluorescence decay constant which can be respectively at these concentration ranges between 16 ns and 74 ns, even more preferably between 30 ns and 70 ns. These preferential ranges of concentration of primary fluorophores can therefore give the hybrid material an increasingly high fluorescence decrease constant: such a hybrid material can then advantageously enter into the composition of a hybrid plastic scintillator compartment, possibly combined with a compartment fast plastic scintillator in a phoswich type plastic scintillation detection device to improve the discrimination between beta particle and gamma radiation.

For example, the variable molar concentrations of the main primary fluorophore in the incorporated fluorescent mixture (the rest of the mixture being constituted by the additional primary fluorophore) can possibly confer on the hybrid material the following fluorescence decay constants: - molar concentration of 86%: 15 ns; - molar concentration of 96%: 35 ns; - 99% molar concentration: 80 ns; - 100% molar concentration: 90 ns.

Preferably, the additional primary fluorophore has a fluorescence decay constant (generally designated "tau") between 1 ns and 10 ns, has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 250 nm and 340 nm and between 330 nm and 380 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1.

In the present description, the centroid designates the wavelength for the middle of the width at half height of the band of greatest amplitude of the radiation considered. A light absorption spectrum can be measured with a UV / visible spectrophotometer, and a fluorescence emission spectrum with a spectrofluorimeter.

The fluorescence decay constant corresponds to the variation over time of the photoluminescence intensity. It is measured by counting a single photon resolved in time; as described for example in the document "M. Wahl," Time-Correlated Single Photon Counting ", M. Wahl, technical note from the company PicoQuant, 2014" [reference 4], available online at the following Internet address: "Https: //www.picoquant.com/images/uploads/page/fîles/72 53/1 echnote_tcspc.pdf", as well as the book "DV 0 'Connor, D. Phillips," Time Correlated Single Photon Counting ", Academie Press, New York, 1984, pages 25 to 34 ”[reference 5].

The quantum fluorescence yield corresponds to the proportion of luminescence photons emitted by the quantity of photons absorbed by the hybrid material. It is for example measured with an integration sphere as a module of a spectrofluorimeter. Without an integration sphere, the quantum fluorescence yield can be determined by relative measurement of the sample (see for example the document "Rohwer, LS, Martin, JE;" Measuring the absolute guantum efficiency of luminescent materials ", J. Lumin . 2005, 115, pages 77-90 "[reference 6]) vis-à-vis a reference solution of quinine sulfate (see for example the document" Velapoli, RA; Mielenz, KD, "A Fluorescence Standard Reference Material: Quinine Sulfate Dihydrate ", Appl. Opt., 1981, 20, 1718." [reference 7] available online at the following Internet address: https: //www.nist.gov/sites/default/files/documents / srm / SP260 -64.PDF).

Advantageously, the additional primary fluorophore can have a fluorescence emission spectrum, the centroid of which is at a wavelength between 355 nm and 365 nm, typically centered around 360 nm, so that the interaction effect is optimal with secondary fluorophore.

Time resolved single photon counting is a spectroscopy technique for measuring the fluorescence decay constant of photoluminescent compounds or their mixtures. It consists in exciting by means of a rapidly decreasing light beam (compared to the luminescent radiation emitted in return to observe) a fluorophore or a fluorescent mixture, then in observing by means of a monochromator coupled to a photomultiplier the resultant of photoluminescence . The hybrid material of the invention is more particularly excited with a low frequency (typically up to 1 MHz) to avoid any stack of scintillation pulses.

Preferably, the additional primary fluorophore is chosen from 2,5-diphenyloxazole (PPO), [para] -terphenyl (pTP), [meta] -terphenyl (mTP), biphenyl, 2-phenyl-5- ( 4-biphenyl) -1,3,4-oxadiazole (PBD), 2- (4'-t-butylphenyl) -5- (4 "-biphenylyl) -1,3,4-oxadiazole (Butyl-PBD), Anthracene, [para] -quaterphenyl, tetraphenylbutadiene, 2V-ethylcarbazole, N- (2-ethylhexyl) carbazole, 4-isopropylbiphenyl, [para] -sexiphenyl, 1-vinylbiphenyl, 2-vinylbiphenyl , 1-vinylnaphthalene, 2-vinylnaphthalene, 1-methylnaphthalene, 2V-vinylcarbazole, 9-anthracenyl methacrylate or mixtures thereof.

More particularly, the additional primary fluorophore is 2,5-diphenyloxazole (PPO), [para] -terphenyl (pTP) or a mixture thereof.

As indicated previously, the additional primary fluorophore can be covalently linked to the polymer matrix, for example via the polymerization of a vinyl, allylic, acrylic or methacrylic function carried by the additional primary fluorophore. For example, 1-vinylbiphenyl, 2-vinylbiphenyl, 1-vinylnaphthalene, 2-vinylnaphthalene, 1-methylnaphthalene, 2V-vinylcarbazole can be used in order to be linked by covalent bond in order to form a copolymer with the polymer matrix.

The incorporated fluorescent mixture may further comprise a secondary fluorophore. The secondary fluorophore further improves the detection of radioluminescent radiation.

The mass concentration of the secondary fluorophore relative to the mass of the hybrid material can be between 0.002% and 0.5% by mass, preferably between 0.01% and 0.2% by mass, even more preferably between 0.01% and 0 , 1% by mass. By way of example, the secondary fluorophore can be chosen from 1,4-di [2 (5-phenyloxazolyl)] benzene, 1,4-bis- (2-methylstyryl) -benzene, 1,4-bis (4-methyl-5-phenyl-2-oxazolyl) benzene, 9,10-diphenylanthracene or their mixtures. The polymer matrix then comprises, relative to the mass of the hybrid material, 0.002% by mass to 0.2% by mass of the secondary fluorophore.

According to a first embodiment, the secondary fluorophore can be chosen such that it has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 405 nm and 460 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1. The secondary fluorophore can thus be chosen from 1,4-bis (5-phenyl- 2-oxazolyl) benzene (POPOP), 1,4-bis (4-methyl-5-phenyl-2-oxazolyl) benzene (dimethylPOPOP), bis-methylstyrylbenzene (bis-MSB), 9,10-diphenylanthracene ( 9.10-DPA) or mixtures thereof. The molecular structures of these secondary fluorophores are illustrated below.

According to a second embodiment, the secondary fluorophore can be chosen so that it has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 4 60 nm and 550 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1. The secondary fluorophore can then be chosen from coumarin 6, coumarin 7, coumarin 30, coumarin 102, coumarin 151, coumarin 314, coumarin 334, 3-hydroxyflavone or mixtures thereof. The

molecular structures of these secondary fluorophores are illustrated below.

According to a third embodiment, the secondary fluorophore can be chosen such that it has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 550 nm and 630 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1. The secondary fluorophore can then be chosen from Nile red ("Nile red"), rhodamine B or a salt thereof, 4- (dicyanomethylene) -2-methyl-6- (4-dimethylaminostyryl) -4H-pyrane (DCM), pyrromethene 580, any molecule of the N-alkyl or N-alkyl type or 27-aryl-perylenediimide (such as, for example, 2V, 2V'-bis (2,5-di-tert-butylphenyl) -3,4,9,10-perylenedicarboximide). The molecular structures of these secondary fluorophores are illustrated below.

The invention also relates to a process for the manufacture by polymerization, via a polymerization medium, of the hybrid material of the invention which may be as defined in the present description, in particular according to one or more of the variants described for this material.

The process for manufacturing a hybrid material by polymerization comprises the following successive stages: a) providing a polymerization medium comprising: monomers, oligomers or their mixtures intended to form at least one polymer constituting the polymer matrix which can be as defined in the present description, in particular according to one or more of the variants described for this polymer matrix;

a liquid fluorescent mixture comprising in molar concentration relative to the total number of moles of primary fluorophore in the liquid fluorescent mixture i) 80% to 99.6% by mol of a main primary fluorophore consisting of naphthalene and ii) 0.4% to 20 mol% of an additional primary fluorophore, the centroid of the light absorption spectrum and of the fluorescence emission spectrum having respectively a wavelength between 250 nm and 340 nm and between 330 nm and 380 nm, the fluorescence decay constant is between 1 ns and 10 ns, and the quantum fluorescence yield in an apolar solvent is between 0.2 and 1, preferably between 0.5 and 1; b) polymerizing the polymerization medium in order to obtain the hybrid material.

During step b) of polymerization of a precursor of the polymer (namely a precursor such as the aforementioned monomers and / or oligomers), the main and additional primary fluorophores, as well as any other compound present in the medium of polymerization, are generally trapped and distributed homogeneously in the polymer matrix in formation. Therefore, in the present description, the “liquid fluorescent mixture” is the fluorescent mixture comprising the primary primary fluorophore and the additional primary fluorophore and which is contained in the polymerization medium before performing step b).

The “incorporated fluorescent mixture” designates the fluorescent mixture comprising the main primary fluorophore and the additional primary fluorophore and which is incorporated into the hybrid material after step b) of polymerization, for example by grafting or dispersion.

The “fluorescent mixture for extrusion” designates the fluorescent mixture comprising the main primary fluorophore and the additional primary fluorophore which is contained in the extrusion mixture further containing polymerized ingredients intended to form a polymer matrix.

The polymerization medium generally does not include a solvent. The manufacturing process is then a so-called "mass polymerization" process. However, as an option, the polymerization medium can also comprise a polymerization solvent. The manufacturing process is then generally carried out at reflux of the solvent. The solvent for the polymerization medium can be chosen from xylene, chloroform, dichloromethane, chlorobenzene, benzene, tetrachloromethane or their mixtures.

The monomers or oligomers can comprise at least one aromatic, (meth) acrylic or vinyl group. At least one monomer can be chosen from styrene, vinyltoluene, vinylxylene, 1-vinylbiphenyl, 2-vinylbiphenyl, 1-vinylnaphthalene, 2-vinylnaphthalene, 1-methylnaphthalene, 27-vinylcarbazole, (meth ) methyl acrylate, (meth) acrylic acid or 2-hydroxyethyl (meth) acrylate.

The polymerization medium can in turn comprise 1% by mass to 25% by mass (or even 1% by mass at 5% by mass) of the liquid fluorescent mixture.

The liquid fluorescent mixture can comprise 90% to 99.1% molar (or even 96% to 99.1% molar) of the main primary fluorophore.

The polymerization medium can also comprise at least one chemical species intended to be incorporated into the hybrid material to give it or improve particular properties (for example a secondary fluorophore), and / or at least one species intended to be consumed or modified at during step b) of polymerization (for example a crosslinking agent, a polymerization initiator).

The polymerization medium can comprise: a secondary fluorophore, typically according to a mass concentration of between 0.002% and 0.5% by mass, or even 0.002% by mass at 0.2% by mass; and / or a crosslinking agent, typically according to a mass concentration of between 0.1% and 20% by mass, or even 0.001% by mass to 1% by mass; and / or - a polymerization initiator, typically according to a concentration of 0.001% by mass to 1% by mass.

The additional primary fluorophore, the secondary fluorophore and / or the crosslinking agent can also be as defined according to one or more of the variants described in the present description.

The polymerization reaction according to step b) can be carried out according to the conditions usually employed by a person skilled in the art.

For example, as indicated in patent application ÜO 2013076281 [reference 8], the polymerization initiator can be chosen from a peroxide compound (for example benzoyl peroxide), a nitrile compound (for example azo (bis) isobutyronitrile (AIBN)) or mixtures thereof. When the polymerization reaction is carried out in particular with methacrylate monomers, it can be induced by heating the polymerization medium to a suitable temperature (generally between 40 ° C and 140 ° C), or by doping the polymerization medium with 2 , 2-dimethoxy-2-phenylacetophenone as a polymerization initiator then by performing irradiation under UV (for example, at a wavelength of 355 nm). The polymerization reaction in the presence of styrenic monomers can be thermally induced, typically by heating between 40 ° C and 140 ° C.

The process for manufacturing the hybrid material by polymerization of the invention can be such that, during step b) of polymerization, the polymerization medium is heated to a polymerization temperature of between 100 ° C. and 140 ° C. ( for a sufficient time for the polymerization to be complete, generally for 24 hours), then cooled at a rate of 10 ° C to 20 ° C per day (generally to reach room temperature, typically 20 ° C) to obtaining the hybrid material.

For example, the polymerization medium can be heated for 24 hours at 140 ° C., then cooled at a rate of 20 ° C. per day until it returns to 20 ° C.

Steps a) and b) of the manufacturing process by polymerization via a polymerization medium of the invention can be carried out in a mold in order to obtain a part as defined in the present description, or a blank of this part.

The manufacturing process of the invention by polymerization via a polymerization medium may further comprise a step c) during which the hybrid material or the blank of the part is machined in order to obtain the part as defined in the present description. This machining step consists, for example, of rectifying the faces (for example by lathe), then of polishing them. The invention also relates to a hybrid material obtained or capable of being obtained by the process for the manufacture by polymerization of a hybrid material via a polymerization medium, in particular according to one or more of the variants described for this process. The invention also relates to a part for detection by plastic scintillation comprising a hybrid material which may be as defined according to one or more of the variants described in this description for this material.

In general, the part for detection by plastic scintillation is thus composed in whole or in part of a hybrid material comprising: - a polymer matrix; and, - a fluorescent mixture incorporated into the polymer matrix and comprising in molar concentration relative to the total number of moles of primary fluorophore in the incorporated fluorescent mixture i) 80% to 99.6 mol% of a main primary fluorophore consisting of naphthalene and ii) 0.4% to 20 mol% of an additional primary fluorophore, the centroid of the light absorption spectrum and the fluorescence emission spectrum of which have respectively a wavelength between 250 nm and 340 nm and comprised between 330 nm and 380 nm (or even between 355 nm and 365 nm), the fluorescence decay constant is between 1 ns and 10 ns, and the quantum fluorescence yield in an apolar solvent is between 0.2 and 1 ( even between 0.5 and 1).

This part can be a unit (such as for example an optical fiber) or a sub-unit of a device for detection by plastic scintillation (for example the hybrid compartment of a phoswich type detector).

The polymer matrix of the hybrid material making up all or part of the part can be composed wholly or in part of at least one polymer comprising repeating units resulting from the polymerization of monomers comprising at least one aromatic, (meth) acrylic or vinyl group. and / or it can consist entirely or in part of at least one crosslinked polymer.

At least one monomer intended to form the polymer matrix is chosen from styrene, vinyltoluene, vinylxylene, 1-vinylbiphenyl, 2-vinylbiphenyl, 1-vinylnaphthalene, 2-vinylnaphthalene, 1-methylnaphthalene, 2V- vinylcarbazole, methyl (meth) acrylate, (meth) acrylic acid or 2-hydroxyethyl (meth) acrylate. Preferably, the monomer is styrene or vinyltoluene.

The part for the detection by plastic scintillation of the invention can be presented according to the following variants, possibly combined: the hybrid material comprises 1% by mass at 25% by mass (or even 1% by mass at 5% by mass) of the incorporated fluorescent mixture, and or ; the incorporated fluorescent mixture comprises 90% to 99.1% molar (or even 96% to 99.1% molar) of the main primary fluorophore, and / or; - the additional primary fluorophore is covalently linked to the polymer matrix, and / or; - the additional primary fluorophore is chosen from 2,5-diphenyloxazole (PPO), [para] -terphenyl (pTP), [meta] -terphenyl (mTP), biphenyl, 2-phenyl-5- (4 -biphenyl) -1,3,4-oxadiazole (PBD), 2- (4'-t-butylphenyl) -5- (4 "-biphenylyl) -1,3,4-oxiadiazole (Butyl-PBD), l anthracene, [para] -quaterphenyl, tetraphenylbutadiene, 2V-ethylcarbazole, N- (2-ethylhexyl) carbazole, 4-isopropylbiphenyl, [para] -sexiphenyl, 1-vinylbiphenyl, 2-vinylbiphenyl, 1-vinylnaphthalene, 2-vinylnaphthalene, 1-methylnaphthalene, 2V-vinylcarbazole, 9-anthracenyl methacrylate or mixtures thereof; the additional primary fluorophore preferably being 2,5-diphenyloxazole (PPO), ] -terphenyl (pTP) or a mixture thereof.

The incorporated fluorescent mixture of the hybrid material of the part may also comprise a secondary fluorophore, for example at a mass concentration relative to the mass of the hybrid material which is between 0.002% and 0.5% by mass, or even 0.01% 0.2 mass% by mass of the secondary fluorophore.

The primary fluorophore can be chosen from 1,4-di [2 (5-phenyloxazolyl)] benzene, 1,4-bis- (2-methylstyryl) -benzene, 1,4-bis (4-methyl-5 -phenyl-2-oxazolyl) benzene, 9,10-diphenylanthracene or their mixtures.

According to a first embodiment, the secondary fluorophore has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 405 nm and 460 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1.

In this case, the secondary fluorophore can be chosen from 1,4-bis (5-phenyl-2-oxazolyl) benzene (POPOP), 1,4-bis (4-methyl-5-phenyl-2-oxazolyl) benzene (dimethylPOPOP), bis-methylstyrylbenzene (bis-MSB), 9,10-diphenylanthracene (9,10-DPA) or their mixtures.

According to a second embodiment, the secondary fluorophore has a light absorption spectrum and a fluorescence emission spectrum, the centroid of which is respectively at a wavelength between 330 nm and 380 nm and between 460 nm and 550 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1.

In this case, the secondary fluorophore can be chosen from coumarin 6, coumarin 7, coumarin 30, coumarin 102, coumarin 151 coumarin 314, coumarin 334, 3-hydroxyflavone or their mixtures.

According to a third embodiment, the secondary fluorophore has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 550 nm and 630 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1.

In this case, the secondary fluorophore can be chosen from Nile red, rhodamine B or one of its salts, 4- (Dicyanomethylene) -2-methyl-6- (4-dimethylaminostyryl) -4H-pyrane, pyrromethene 580, or a U-alkyl or D-aryl-perylenediimide.

Due to the possibility of varying the relative proportion between the primary primary fluorophore and the additional primary fluorophore, the hybrid material (and therefore the part for detection by plastic scintillation) can have a fluorescence decay constant of between 10 ns and 90 ns (even between 15 ns and 80 ns).

The part can have a wide variety of shapes, for example a parallelepiped or cylindrical shape.

The rectangular-shaped part is for example a plastic scintillator compartment capable of being incorporated into a device for detection by plastic scintillation.

When the part has a cylindrical shape, and enters for example the composition of a plastic scintillator pillar, it can have a square or rectangular section.

When the part of cylindrical shape is for example a scintillating optical fiber (in which case the hybrid material comprises a polymer matrix made up wholly or in part of at least one polymer which is not crosslinked), it may have a circular section, elliptical or hexagonal.

An optical fiber is a waveguide which exploits the refractive properties of light. It usually consists of a heart surrounded by a sheath. The core of the fiber has a slightly higher refractive index (difference of a few thousandths) than the sheath. The light is therefore fully reflected multiple times at the interface between the material of the internal fiber constituting the core is the sheathing material by total internal reflection.

The scintillating optical fiber as a part of the invention 10 may comprise a polymer fiber 11 composed in whole or in part of the hybrid material and whether or not provided with a sheath 12 covering the polymer fiber and composed in whole or in part of a material cladding for optical fiber whose refractive index is lower than that of the hybrid material, the hybrid material comprising a polymer matrix consisting wholly or in part of at least one polymer which is not crosslinked.

Several scintillating optical fibers can be combined in a fiber bundle.

The presence of a sheath is not compulsory. For example, when the object is to detect an alpha particle, the scintillating optical fiber is composed only of an internal polymer fiber without a sheath to avoid that the energy of the incident radiation is mainly absorbed by the sheath. However, most often, the scintillating optical fiber comprises a sheath whose sheathing material is a material usually used for an optical fiber, in particular scintillating. For example, the sheathing material is chosen from poly (methyl methacrylate), poly (benzyl methacrylate), poly (trifluoromethyl methacrylate), poly (trifluoroethyl methacrylate) or mixtures thereof. The invention also relates to a method of manufacturing by extrusion of a part for detection by plastic scintillation and composed in whole or in part of a hybrid material, the part can be as defined according to one or more of the variants described in the present description, the process comprising the following successive stages: a ') having an extrusion mixture comprising: - polymerized ingredients intended to form a polymer matrix as defined in the present description, in particular according to one or more of the variants described, with the exception of the case where the polymer matrix consists wholly or in part (preferably more than 10% by weight of polymer in the polymer matrix) of at least one crosslinked polymer; - a fluorescent mixture for extrusion comprising in molar concentration relative to the total number of moles of primary fluorophore in the fluorescent mixture for extrusion i) 80% to 99.6% molar (or even 90% to 99.1% molar, even 96% 99.1 mol%) of a primary primary fluorophore consisting of naphthalene and ii) 0.4% to 20 mol% of an additional primary fluorophore including the centroid of the light absorption spectrum and the fluorescence emission spectrum have respectively a wavelength between 250 nm and 340 nm and between 330 nm and 380 nm, the fluorescence decay constant is between 1 ns and 10 ns, and the quantum yield of fluorescence in an apolar solvent is understood between 0.2 and 1; b ') under an extrusion atmosphere at an extrusion temperature between 170 ° C and 200 ° C, extrude the extrusion mixture through a die in order to obtain the part composed in whole or in part of a hybrid material.

An extrusion manufacturing process is essentially a process for the transformation of polymerized ingredients, which, once softened or in a molten state by heat, are continuously pushed through a die which gives its geometry to the polymer-based profile obtained. at the end of the process. The extrusion process is well known to those skilled in the art: it is described for example in the document "Engineering techniques, Single-screw extrusion-extrusion (part 1), Reference AM3650, publication of 2002" [reference 9] .

The polymerizable ingredients which can be used are formed from one or more polymers which have a thermal stability such that the polymer is not degraded at the temperature required for extrusion, which depends on the glass transition temperature. Their chemical composition is identical to that of the polymer matrix.

The polymerized ingredients are generally in solid form, in particular in the form of granules. Extrusion step b ′) can be carried out by means of an extruder (for example a single screw, twin screw, or multi screw type extruder) or a co-mixer. Typically, the die is positioned at the outlet of the extruder. The extrusion atmosphere can be chemically inert to the extrusion mixture. Such an atmosphere limits or avoids the oxidation of the polymer matrix obtained. It includes for example nitrogen or a rare gas, such as for example argon.

Typically, the extrusion process of the invention is carried out at an extrusion temperature below 218 ° C which is the evaporation temperature of naphthalene at atmospheric pressure, but at a temperature high enough to soften or melt the polymerized ingredients, for example at an extrusion temperature between 170 ° C and 200 ° C. Extrusion step b ′) can be carried out using an extruder (for example of the single-screw, twin-screw or multi-screw type) or of a co-mixer. The invention also relates to a method of manufacturing by polymerization of a part for detection by plastic scintillation and composed in whole or in part of a hybrid material, the part can be as defined according to one or more of the variants described in the present description, the process comprising at least one polymerization via a polymerization medium according to the following successive stages: a) in a first mold, having a first polymerization medium comprising: monomers, oligomers or their mixtures intended to form at least a polymer constituting a polymer matrix as defined according to one or more of the variants described in the present description (in particular the case where the polymer matrix consists entirely or in part of at least one crosslinked polymer; a liquid fluorescent mixture comprising in molar concentration relative to the total number of moles of fluoroph primary ore in the liquid fluorescent mixture i) 80% to 99.6% molar of a primary primary fluorophore consisting of naphthalene and ii) 0.4% to 20% molar of an additional primary fluorophore including the centroid of the spectrum light absorption and fluorescence emission spectrum have respectively a wavelength between 250 nm and 340 nm and between 330 nm and 380 nm, the fluorescence decay constant is between 1 ns and 10 ns, and the quantum fluorescence yield in an apolar solvent is between 0.2 and 1; b) polymerizing the first polymerization medium in order to directly obtain the part or a blank of the part which is then modified (for example machined, in particular by drawing the blank) to obtain the part.

In the method of manufacturing a part by polymerization, the fluorescent mixture is liquid, since it is mixed in the first polymerization medium with monomers and / or oligomers.

The internal volume of the mold can have a parallelepipedal or cylindrical shape. The cylindrical shape can be circular, elliptical, hexagonal, square or rectangular.

When the internal volume of the mold has a parallelepiped shape, the manufacturing process by polymerization can such that the piece of parallelepiped shape obtained at the end of step b) is a plastic scintillator compartment as defined in the present description and able to be incorporated into a device for detection by plastic scintillation.

In this case, the plastic scintillator compartment of parallelepiped shape can be obtained directly at the end of the manufacturing process by polymerization, after if necessary an optional rectification step.

When the internal volume of the mold has a cylindrical shape, the manufacturing process by polymerization can be such that the part is a scintillating optical fiber 10 without sheath which can be as defined in the present description according to one or more of its variants , so that a cylindrical bar as a blank for the part is obtained at the end of step b), the method comprising the following additional step carried out after step b) of polymerization: c) in a fiberizing tower, soften by heating then stretch the blank of the part in order to obtain a polymer fiber 11 composed in whole or in part of the hybrid material as scintillating optical fiber 10 without sheath.

Alternatively, when the internal volume of the mold has a cylindrical shape, the manufacturing process by polymerization can be such that the part is a scintillating optical fiber 10 provided with a sheath 12 which can be as defined in the present description according to a or more of its variants, so that a cylindrical bar as the first draft of the part is obtained at the end of step b), the method comprising the following additional step carried out after step b) : - bl) place the first blank of the part in a second cylindrical mold, then fill the free volume defined by the internal face of the second cylindrical mold and the external face of the first blank of the part with a second polymerization medium comprising a precursor of a cladding material for optical fiber for which the refractive index of the cladding material is lower than that of the hybrid material; b2) polymerizing the second polymerization medium in order to form the sheathing material which covers the first blank of the part, in order to obtain a second blank of the part (constituting a preform); c) in a fiberizing tower, soften by heating and then stretch the second blank of the part in order to obtain, as scintillating optical fiber 10 provided with a sheath 12, a polymer fiber 11 composed in whole or in part of the hybrid material and provided with the sheath 12 covering the polymer fiber 11.

In these two alternatives, the internal volume of the cylindrical mold has for example a circular section. The mold can then have an internal diameter between 2 cm to 10 cm (typically 5 cm) and / or a longitudinal length between 10 cm and 100 cm (typically 50 cm). These dimensions generally correspond to those of the cylindrical bar as a preform or blank of the part.

The precursor of the cladding material is for example chosen from methyl methacrylate, benzyl methacrylate, trifluoromethyl methacrylate, trifluoroethyl methacrylate or their mixtures. The blank of the part or preform is generally placed vertically on the fiberizing tower. At the end of step c), the scintillating optical fiber with or without a sheath is most often recovered by gravimetric turning.

During the polymerization step b) and / or bl), the first polymerization medium can be heated to a first polymerization temperature of between 100 ° C. and 140 ° C. (for example for a period of 12 hours to 24 h, in particular one day at 140 ° C.), then cooled according to a drop in the polymerization temperature from 10 ° C. to 20 ° C. per day until the part or the blank of the part is obtained. Cooling is generally continued until the ambient temperature of 20 ° C is reached.

During step b2) of polymerization, the second polymerization medium can be heated to a second polymerization temperature of between 50 ° C. and 70 ° C. (for example for a period of 8 to 10 days, in particular 10 days to 60 ° C), then cooled according to a drop in the polymerization temperature from 10 ° C to 20 ° C per day until the part or the blank of the part is obtained. Cooling is generally continued until the ambient temperature of 25 ° C is reached. The heating operation to soften can be carried out during step c) at a temperature between 150 ° C and 190 ° C. The blank of the part can be corrected just before performing step c) of drawing. For example, the cylindrical bar is rectified by cutting its upper and lower part over a short length. The upper face of a part in parallelepiped form, namely the face which finds itself in slight contact with the ambient air, can also be rectified by cutting the upper part over a short length then polishing. At the end of the polymerization manufacturing process, the scintillating optical fiber can be such that: the diameter of the polymer fiber 11 is between 50 μm and 1 mm, and / or; the thickness of the sheath 12 is between 1 μm and 20 μm, and / or; - the length of the scintillating optical fiber is between 0.1 and 2 km.

The first polymerization medium and / or the second polymerization medium can comprise a polymerization solvent chosen for example from xylene, chloroform, dichloromethane, chlorobenzene, benzene, tetrachloromethane or their mixtures.

Regarding respectively the method of manufacturing a part by extrusion or the method of manufacturing a part by polymerization, the fluorescent mixture for extrusion or the liquid fluorescent mixture can be such that: it comprises 90% to 99.1 mol% ( or even 96% to 99.1 mol%) of the main primary fluorophore, and / or; the additional primary fluorophore has a quantum fluorescence yield in an apolar solvent of between 0.5 and 1, and / or; - It comprises a secondary fluorophore as defined in the present description, in particular according to one or more of the variants described. The invention also relates to a device for detection by plastic scintillation comprising a part for detection by plastic scintillation (which can be as defined according to one or more of the variants described in this description) as a hybrid plastic scintillator element, the part being generally composed in whole or in part of a hybrid material comprising: - a polymer matrix; and, - a fluorescent mixture incorporated into the polymer matrix and comprising in molar concentration relative to the total number of moles of primary fluorophore in the incorporated fluorescent mixture i) 80% to 99.6 mol% of a main primary fluorophore consisting of naphthalene and ii) 0.4% to 20 mol% of an additional primary fluorophore, the centroid of the light absorption spectrum and the fluorescence emission spectrum of which have respectively a wavelength between 250 nm and 340 nm and comprised between 330 nm and 380 nm, the fluorescence decrease constant is between 1 ns and 10 ns, and the quantum fluorescence yield in an apolar solvent is between 0.2 and 1 (or even between 0.5 and 1); the part being coupled to an electronic acquisition module so that the module is able to collect the radioluminescent radiation emitted by the part when the latter is brought into contact with ionizing radiation or an ionizing particle.

The polymer matrix of the hybrid material making up all or part of the part can be composed wholly or in part of at least one polymer comprising repeating units resulting from the polymerization of monomers comprising at least one aromatic, (meth) acrylic or vinyl group. and / or it can consist entirely or in part of at least one crosslinked polymer.

At least one monomer intended to form the polymer matrix can be chosen from styrene, vinyltoluene, vinylxylene, 1-vinylbiphenyl, 2-vinylbiphenyl, 1-vinylnaphthalene, 2-vinylnaphthalene, 1-methylnaphthalene, 2V -vinylcarbazole, methyl (meth) acrylate, (meth) acrylic acid or 2-hydroxyethyl (meth) acrylate. Preferably, the monomer is styrene or vinyltoluene.

The hybrid material making up all or part of the part integrated into the device for detection by plastic scintillation of the invention can be presented according to the following variants, possibly combined: - the hybrid material comprises 1% by mass to 25% by mass (or even 1 % by mass to 5% by mass) of the incorporated fluorescent mixture, and / or; the incorporated fluorescent mixture comprises 90% to 99.1% molar (or even 96% to 99.1% molar) of the main primary fluorophore, and / or; - the additional primary fluorophore is covalently linked to the polymer matrix, and / or; - the additional primary fluorophore is chosen from 2,5-diphenyloxazole (PPO), [para] -terphenyl (pTP), [meta] -terphenyl (mTP), biphenyl, 2-phenyl-5- (4 -biphenyl) -1,3,4-oxadiazole (PBD), 2- (4'-t-butylphenyl) -5- (4 "-biphenylyl) -1,3,4-oxiadiazole (Butyl-PBD), l anthracene, [para] -quaterphenyl, tetraphenylbutadiene, 2V-ethylcarbazole, N- (2-ethylhexyl) carbazole, 4-isopropylbiphenyl, [para] -sexiphenyl, 1-vinylbiphenyl, 2-vinylbiphenyl, 1-vinylnaphthalene, 2-vinylnaphthalene, 1-methylnaphthalene, 2V-vinylcarbazole, 9-anthracenyl methacrylate or mixtures thereof; the additional primary fluorophore preferably being 2,5-diphenyloxazole (PPO), ] -terphenyl (pTP) or a mixture thereof.

The incorporated fluorescent mixture of the hybrid material of the part may also comprise a secondary fluorophore, for example at a mass concentration relative to the mass of the hybrid material which is between 0.002% and 0.5% by mass, or even 0.01% 0.2 mass% by mass of the secondary fluorophore.

The primary fluorophore can be chosen from 1,4-di [2 (5-phenyloxazolyl)] benzene, 1,4-bis- (2-methylstyryl) -benzene, 1,4-bis (4-methyl-5 -phenyl-2-oxazolyl) benzene, 9,10-diphenylanthracene or their mixtures.

According to a first embodiment, the secondary fluorophore has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 405 nm and 460 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1.

In this case, the secondary fluorophore can be chosen from 1,4-bis (5-phenyl-2-oxazolyl) benzene (POPOP), 1,4-bis (4-methyl-5-phenyl-2-oxazolyl) benzene (dimethylPOPOP), bis-methylstyrylbenzene (bis-MSB), 9,10-diphenylanthracene (9,10-DPA) or their mixtures.

According to a second embodiment, the secondary fluorophore has a light absorption spectrum and a fluorescence emission spectrum, the centroid of which is respectively at a wavelength between 330 nm and 380 nm and between 460 nm and 550 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1.

In this case, the secondary fluorophore can be chosen from coumarin 6, coumarin 7, coumarin 30, coumarin 102, coumarin 151 coumarin 314, coumarin 334, 3-hydroxyflavone or their mixtures.

According to a third embodiment, the secondary fluorophore has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 550 nm and 630 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1.

In this case, the secondary fluorophore can be chosen from Nile red, rhodamine B or one of its salts, 4- (Dicyanomethylene) -2-methyl-6- (4-dimethylaminostyryl) -4H-pyrane, pyrromethene 580, or a 27-alkyl or 27-aryl-perylenediimide.

Due to the possibility of varying the relative proportion between the main primary fluorophore and the additional primary fluorophore, the hybrid material (and therefore the part for detection by plastic scintillation and the device which incorporates it) can have a fluorescence decay constant between 10 ns and 90 ns (or even between 15 ns and 80 ns).

The part of the device can have a wide variety of shapes, for example a parallelepipedal or cylindrical shape.

The rectangular-shaped part is for example a plastic scintillator compartment capable of being incorporated into a device for detection by plastic scintillation.

When the part has a cylindrical shape, and enters for example the composition of a plastic scintillator pillar, it can have a square or rectangular section.

When the part of cylindrical shape is for example a scintillating optical fiber (in which case the hybrid material comprises a polymer matrix made up wholly or in part of at least one polymer which is not crosslinked), it may have a circular section, elliptical or hexagonal.

The scintillating optical fiber as a part of the invention 10 may comprise a polymer fiber 11 composed in whole or in part of the hybrid material and whether or not provided with a sheath 12 covering the polymer fiber and composed in whole or in part of a material cladding for optical fiber whose refractive index is lower than that of the hybrid material, the hybrid material comprising a polymer matrix consisting wholly or in part of at least one polymer which is not crosslinked.

Several scintillating optical fibers can be combined in a fiber bundle.

The presence of a sheath is not compulsory. For example, when the object is to detect an alpha particle, the scintillating optical fiber is composed only of an internal polymer fiber without a sheath to avoid that the energy of the incident radiation is mainly absorbed by the sheath. However, most often, the scintillating optical fiber comprises a sheath whose sheathing material is a material usually used for an optical fiber, in particular scintillating. For example, the sheathing material is chosen from poly (methyl methacrylate), poly (benzyl methacrylate), poly (trifluoromethyl methacrylate), poly (trifluoroethyl methacrylate) or mixtures thereof.

The coupling between the part as a plastic scintillator element and the acquisition module is generally carried out by bringing the acquisition module into contact with a portion of the part from which the radioluminescent radiation emerges from the part.

According to a first embodiment, the device for detection by plastic scintillation is such that the hybrid plastic scintillator element is a first hybrid plastic scintillator element 1, the device further comprising a second fast plastic scintillator element 2 whose constant of fluorescence decrease is less than that of the first hybrid plastic scintillator element 1, these plastic scintillator elements 1 and 2 forming a plastic scintillator assembly. The first hybrid plastic scintillator element 1 is preferably composed in whole or in part of a hybrid material whose fluorescence decay constant is between 70 ns and 80 ns. The device is preferably a phoswich type device, in which, for example, each plastic scintillator element is a plastic scintillator compartment. The invention described is not however limited to the incorporation of the hybrid material into a plastic scintillation detector of the phoswich type. It finds an interest when the person skilled in the art needs a plastic scintillator with a constant of fluorescence decay determined and optimized.

The first hybrid plastic scintillator element 1 can be in direct contact with the second rapid plastic scintillator element 2.

According to another alternative, the first hybrid plastic scintillator element 1 is in contact with the second rapid plastic scintillator element 2 via a bonding layer 5. The plastic scintillator assembly therefore further comprises a bonding layer.

In the case where the plastic scintillator elements are of rectangular shape, the first hybrid plastic scintillator element and the second rapid plastic scintillator element are typically in contact with each other via one of their faces, preferably their larger face. identical surface or surface.

In the case where the plastic scintillator elements are of cylindrical shape, the first hybrid plastic scintillator element and the second rapid plastic scintillator element are typically in contact with each other via their circular faces, which are generally of surfaces identical to the place of their contact.

By taking as reference the direction of propagation of the ionizing radiation or of the ionizing particle with respect to the device for detection by plastic scintillation, the first hybrid plastic scintillator element can be either the upstream plastic scintillator element or the element downstream plastic scintillator, in which case the second fast plastic scintillator element is respectively the downstream or upstream plastic scintillator element.

With reference to the direction of propagation of the ionizing radiation or of the ionizing particle with respect to the device, the first hybrid plastic scintillator element 1 is preferably the upstream plastic scintillator element and the second rapid plastic scintillator element 2 is the element plastic scintillator downstream.

The plastic scintillator elements 1 and 2 can have different thicknesses, so that the device comprises a thin plastic scintillator element and a thick rapid scintillator element. The two configurations are therefore possible: the first hybrid plastic scintillator element can be the thin plastic scintillator element or the thick plastic scintillator element.

Preferably, the thickness of the first hybrid plastic scintillator element is less than that of the second fast plastic scintillator element. Thus, according to a preferred embodiment of the invention with a view to promoting beta / gamma discrimination, the device can comprise a first hybrid plastic scintillator element 1 fine and a second fast plastic scintillator element 2 thick. Preferably, the device then comprises the first hybrid plastic scintillator element 1 fine upstream and the second rapid plastic scintillator element 2 thick downstream, with reference to the direction R of propagation of the ionizing radiation or of the ionizing particle with respect to the device. The thin plastic scintillator element may have a thickness of 10 μm to 1 mm, for example from 50 μm to 1 mm, preferably from 100 μm to 500 μm; and the thick plastic scintillator element can have a thickness ranging from 1 mm to several centimeters, for example from 1 mm to 10 cm, preferably from 3 mm to 5 cm.

The second fast plastic scintillator element 2 can have a fluorescence decay constant between 1 ns and 7 ns.

The second rapid plastic scintillator element 2 may comprise a polymer matrix which may be as defined in the present description, in particular according to one or more of the variants described for this polymer matrix, and / or a rapid primary fluorophore chosen from 2,5-diphenyloxazole (PPO), [para] -terphenyl (pTP), [meta] -terphenyl (mTP), biphenyl, 2-phenyl-5- (4-biphenyl) -1,3,4-oxadiazole (PBD) , 2- (4'-t-butylphenyl) -5- (4 "-biphenylyl) -1,3,4-oxadiazole (butyl-PBD), anthracene or mixtures thereof. Preferably, the rapid primary fluorophore is 2,5-diphenyloxazole (PPO), [para] -terphenyl (pTP) or a mixture thereof.

The second rapid plastic scintillator element 2 may comprise a secondary fluorophore which may be as defined in the present description, in particular according to one or more of the variants described.

According to a second embodiment, the device for detection by plastic scintillation according to the invention may comprise a single hybrid plastic scintillator element (plastic scintillation device called “with a single compartment”). Such a single compartment device is advantageous when it is coupled to an electronic acquisition module whose sampling frequency is less than 250 MHz: according to the Niquist-Shannon theorem, a long pulse as obtained with a single hybrid plastic scintillator is best described with such an acquisition module for which the electronics are limited in number of points per nanoseconds.

In general, whatever the embodiment, the part can be coupled to the electronic acquisition module by an optical interface layer 6, namely by optical coupling.

The optical interface layer has in particular the properties of allowing the radiation exiting from the plastic scintillator element to pass, in particular in the downstream position. This layer may be composed in whole or in part of a material known to those skilled in the art, for example chosen from fats, glues, gels, cements, elastomeric compounds, silicone compounds or their mixtures.

The coupling between the part and the electronic acquisition module can be carried out directly or indirectly via the hybrid plastic scintillator element.

For example, this coupling is generally for the single hybrid plastic scintillator element.

The coupling with the hybrid plastic scintillator element is on the other hand indirect in the case of the phoswich scintillator: the downstream fast plastic scintillator element comes between these two parts, and it is the only one to be in direct contact with the module d electronic acquisition.

Concerning the electronic acquisition module, it can comprise a photodetector 3, chosen for example from a photomultiplier, a photodiode, a CCD charge transfer camera or a CMOS sensor.

The electronic acquisition module can be placed downstream, by reference to the direction of propagation of the ionizing radiation or of the ionizing particle with respect to the device, of the part as a hybrid plastic scintillator element, of the unique hybrid plastic scintillator element, the first hybrid plastic scintillator element 1 or the second rapid plastic scintillator element 2.

It can be calibrated for energy using standard scintillating materials. The invention also relates to an apparatus for detection by plastic scintillation comprising a device as defined in the present description according to one or more of its variants, consisting of a portable device for the detection of ionizing radiation, a detection gantry or a detector CCD (English acronym for "Charge Coupled Device"). The invention also relates to a method for manufacturing a device for detection by plastic scintillation as defined in the present description according to one or more of its variants, in which the part as a hybrid plastic scintillator element is coupled (directly or indirectly) to the electronic acquisition module, so that the module is able to collect the radioluminescent radiation emitted by the part when the latter is brought into contact with ionizing radiation or an ionizing particle.

The manufacturing method can be such that the device comprises a plastic scintillator assembly, the method comprising the following successive steps: a '') having a first hybrid plastic scintillator element 1 as a part and a second plastic scintillator element fast 2 whose fluorescence decay constant is lower than that of the first hybrid plastic scintillator element 1; each of these plastic scintillator elements further having a polished surface of the same dimension as that of the other plastic scintillator element; b '') coupling, via their polished surface, the first hybrid plastic scintillator element 1 and the second rapid plastic scintillator element 2 in order to obtain the plastic scintillator assembly; c '') coupling the plastic scintillator assembly comprising the part to the electronic acquisition module, so that the module is able to collect the radioluminescent radiation emitted by the plastic scintillator assembly when the latter is brought into contact with radiation ionizing or an ionizing particle.

According to a first embodiment, the method of manufacturing the device is an autogenic coupling method by heat bonding: step b '') of coupling bonding can be carried out by heating the polished surface of the first hybrid plastic scintillator element 1 and of the second rapid plastic scintillator element 2 in order to soften these surfaces which are then pressed against one another in order to couple them.

According to a second embodiment, the method of manufacturing the device comprising a plastic scintillator assembly is a method of autogenous molecular coupling (namely autogenous in situ), the method comprising the following successive steps: a '' ') a plastic scintillator element , consisting of a first hybrid plastic scintillator element 1 as a part or by a second rapid plastic scintillator element 2 whose fluorescence decay constant is less than that of the first hybrid plastic scintillator element 1, is produced in situ by polymerization on the other plastic scintillator element which constitutes a polymerization support, in order to obtain a plastic scintillator assembly at the end of step a '"); b' '') the plastic scintillator assembly comprising the part is coupled to the module electronic acquisition, so that the module is able to collect radio radiation luminescent emitted by the plastic scintillator assembly when the latter is brought into contact with ionizing radiation or an ionizing particle.

The coupling between the plastic scintillator elements 1 and 2 according to step b ''), and / or the coupling according to which the electronic acquisition module is coupled with the plastic scintillator assembly according to step c '') or l 'step b' '') or with the single hybrid plastic scintillator element as defined in the present description according to one or more of its variants, can be produced by means of an optical interface layer 6.

The optical interface layer 6 can be an optical cement (for example of the EJ-500 type), a so-called “coupling” solvent for coupling (generally an alcohol, such as for example isopropanol or 1-butanol) or preferably an optical grease (for example of the RTV141A type).

This interface layer generally has a thickness of 1 µm to 10 µm. The invention also relates to a method of measurement by plastic scintillation, the method comprising the following successive steps: i) a device for detection by plastic scintillation as defined in this description, in particular according to one or more of its variants, is set in contact with ionizing radiation or an ionizing particle so that the part (thanks to the hybrid material it contains) included in the device emits radioluminescent radiation; and ii) the radioluminescent radiation is measured with the electronic acquisition module of the device.

Preferably, the duration of the decrease in the radioluminescent radiation measured is between 10 ns and 90 ns, even more preferably between 15 ns and 80 ns, even more preferably between 30 ns and 8 0 ns.

The ionizing radiation or the ionizing particle can come from a radioactive material emitting gamma rays, X-rays, beta particles, alpha particles or neutron. Where appropriate, radioactive material can emit several types of ionizing radiation or ionizing particles. Thus, advantageously, a discrimination by virtue of the shape of the different pulses between the gamma rays and the beta particles can be carried out during step b) of measurement with the scintillation measurement method of the invention.

The radioluminescent radiation which results from this exposure can be measured according to step ii) with a photodetector, such as for example a photodetector chosen from a photomultiplier, a photodiode, a charge transfer camera (called CCD for "Charge-Coupled Device" camera ”in English), a CMOS sensor (for“ Complementary Metal-Oxide Semiconductor ”in English), or any other photon detector whose capture is converted into an electrical signal.

According to a preferred embodiment of the invention, the measurement method can comprise a step iii) in which the presence and / or the quantity of the radioactive material is determined from the measurement of the radioluminescent radiation according to step ii) , as is usually done in plastic scintillation. As an example, step iii) of qualitative and / or quantitative measurement is described by making the analogy with plastic scintillation from the document "Engineering techniques, Radioactivity measurements by liquid scintillation, Reference p2552, publication of 03/10/2004 ”[reference 10].

Quantitative determination can in particular measure the activity of the radioactive source. It can be performed from a calibration curve.

This curve is for example such that the number of photons coming from the radioluminescent radiation emitted for a known radioactive material is correlated with the energy of the incident radiation for this radioactive material. From the solid angle, the distance between the radioactive source and the plastic scintillator, and from the activity detected by the measurement method using the plastic scintillator of the invention, it is then possible to quantify the activity of the radioactive source. The invention also relates to a polymerization composition for manufacturing a hybrid material (as defined in the present description, according to one or more of its variants) for detection by plastic scintillation comprising: monomers, oligomers or their mixtures intended to form at least one polymer constituting a polymer matrix as defined in the present description according to one or more of the variants; a liquid fluorescent mixture comprising in molar concentration relative to the total number of moles of primary fluorophore in the liquid fluorescent mixture i) 80% to 99.6% molar (or even 90% to 99.1% molar, even 96% to 99, 1 mol%) of a main primary fluorophore consisting of naphthalene and ii) 0.4% to 20 mol% of an additional primary fluorophore, the centroid of the light absorption spectrum and the fluorescence emission spectrum of which have a wavelength between 250 nm and 340 nm and between 330 nm and 380 nm, the fluorescence decay constant is between 1 ns and 10 ns, and the quantum yield of fluorescence in an apolar solvent is between 0, 2 and 1 (or even between 0.5 and 1).

The monomers, the oligomers or their mixtures can comprise at least one aromatic, (meth) acrylic or vinyl group.

The liquid fluorescent mixture can comprise a secondary fluorophore, as defined in the present description, according to one or more of its variants.

Thus, according to some of these variants, the secondary fluorophore can have: a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 405 nm and 460 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1, or; a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 460 nm and 550 nm, and whose quantum fluorescence yield in a apolar solvent is between 0.5 and 1, or; a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 550 nm and 630 nm, and whose quantum fluorescence yield in a apolar solvent is between 0.5 and 1.

The secondary fluorophore can be at a mass concentration relative to the mass of the polymerization composition which is between 0.002% and 0.5% by mass.

The polymerization composition can comprise 1% by mass to 25% by mass of the liquid fluorescent mixture.

It can also further comprise a polymerization solvent.

The polymerization composition can be used in the processes for manufacturing the hybrid material or the part as described above. The invention also relates to a ready-to-use kit with mixed fluorophores for the manufacture of a polymerization composition (as defined in this description, according to one or more of its variants), comprising separately for their assembly the components of the following kit: i) monomers, oligomers or mixtures thereof intended to form at least one polymer constituting a polymer matrix and; ii) a fluorescent mixture for polymerization kit comprising in molar concentration relative to the total number of moles of primary fluorophore in the fluorescent mixture for polymerization kit i) 80% to 99.6 mol% of a main primary fluorophore consisting of naphthalene and ii) 0.4% to 20 mol% of an additional primary fluorophore, the centroid of the light absorption spectrum and the fluorescence emission spectrum of which have respectively a wavelength between 250 nm and 340 nm and comprised between 330 nm and 380 nm, the fluorescence decay constant is between 1 ns and 10 ns, and the quantum fluorescence yield in an apolar solvent is between 0.2 and 1 (or even between 0.5 and 1).

Regarding the composition and the proportion of its components, the fluorescent mixture for polymerization kit is identical to the liquid fluorescent mixture described above. However, when it does not include a solvent, it differs from the liquid fluorescent mixture only by the fact that it is then in solid form and not liquid.

The ready-to-use kit with mixed fluorophores can comprise: a first compartment I) containing the monomers, the oligomers or their mixtures; - a second compartment II) containing the fluorescent mixture for polymerization kit.

The fluorescent mixture for polymerization kit can contain 90% to 99.1% molar (or even 96% to 99.1% molar) of the main primary fluorophore. It can represent 1% by mass to 25% by mass of the kit components.

The ready-to-use kit with mixed fluorophores can be such as a secondary fluorophore as defined in this description according to one or more of its variants, a polymerization solvent or their mixture is mixed with i) monomers, oligomers or mixtures thereof and / or ii) the fluorescent mixture for the polymerization kit.

Typically, the secondary fluorophore can be mixed at the same molar concentration with i) monomers, oligomers or their mixtures and with ii) the fluorescent mixture for polymerization kit, to prevent any dilution phenomenon if necessary.

Typically, the polymerization solvent can be mixed with the monomers and oligomers. The invention also relates to a ready-to-use kit with separate fluorophores for the manufacture of a polymerization composition (as defined in this description, according to one or more of its variants), comprising separately for their assembly the components of the following kit: i ') a first polymerization mixture comprising monomers, oligomers or mixtures thereof intended to form at least one polymer constituting a polymer matrix as defined in the present description according to one or more of its variants; and, in molar concentration relative to the total number of moles of primary fluorophore in the kit, 80% to 99, 6% molar (or even 90% to 99, 1% molar, even 96% to 99, 1% molar) of a primary primary fluorophore consisting of naphthalene; ii ') a second polymerization mixture comprising monomers, oligomers or mixtures thereof intended to form at least one polymer constituting a polymer matrix as defined in the present description according to one or more of its variants; and, in molar concentration relative to the total number of moles of primary fluorophore in the kit, 0.4% to 20 mol% of an additional primary fluorophore including the centroid of the light absorption spectrum and the fluorescence emission spectrum have respectively a wavelength between 250 nm and 340 nm and between 330 nm and 380 nm, the fluorescence decay constant is between 1 ns and 10 ns, and the quantum yield of fluorescence in an apolar solvent is understood between 0.2 and 1 (or even between 0.5 and 1).

The ready-to-use kit with separate fluorophores may include: - a first compartment I ') containing the first polymerization mixture; - a second compartment II ') containing the second polymerization mixture.

The first polymerization mixture and / or the second polymerization mixture may comprise a secondary fluorophore as defined in the present description according to one or more of its variants, a polymerization solvent or their mixture.

Concerning the ready-to-use kit with mixed fluorophores or the ready-to-use kit with separate fluorophores: - the monomers, oligomers or their mixtures can represent 75% to 99% by mass of the components of the kit, and / or; - the main primary fluorophore can represent 1% by mass to 25% by mass of the components of the kit, and / or; - may also comprise at least one annex compartment each containing III) a crosslinking agent or a polymerization initiator.

The ready-to-use kit with mixed fluorophores or the ready-to-use kit with separate fluorophores can be such that the additional primary fluorophore can represent 0.006% by mass to 5% by mass of the components of the kit. Indeed, the concentration of the main primary fluorophore in the first polymerization mixture can be between 1% and 25% by mass relative to the monomers or oligomers, and this in order to avoid a posteriori phenomenon of exudation in the polymer matrix as indicated previously. The concentration of the additional primary fluorophore in the second polymerization mixture can also be 25% by mass relative to the monomers or oligomers, i.e. a maximum concentration of 25% χ 20% = 5% in the case of a mixture with the maximum of main primary fluorophore ([c] max = 25%) with the maximum proportion of additional primary fluorophore ([c] max = 20%). The same calculation for the minimum concentration is 1% χ 0.6% = 0.006%. The invention also relates to a ready-to-use kit with polymers for the manufacture of an extrusion mixture (as defined in this description, according to one or more of its variants), comprising separately for assembly purposes the components of the following kit: i '') polymerized ingredients (possibly in the form of granules) intended to form a polymer matrix as defined in the present description according to one or more of its variants; ii ') a fluorescent mixture for extrusion kit comprising in molar concentration relative to the total number of moles of primary fluorophore in the fluorescent mixture for extrusion kit i) 80% to 99.6% molar (or even 90% to 99 , 1 mol%, or even 96% to 99, 1 mol%) of a main primary fluorophore consisting of naphthalene and ii) 0.4% to 20 molar of an additional primary fluorophore including the centroid of the light absorption spectrum and the fluorescence emission spectrum have respectively a wavelength between 250 nm and 340 nm and between 330 nm and 380 nm, the fluorescence decay constant is between 1 ns and 10 ns, and the quantum yield fluorescence in an apolar solvent is between 0.2 and 1 (or even between 0.5 and 1).

The polymerized ingredients have the same chemical composition as the polymer matrix. They differ essentially from the fact that they are not in massive form like the polymer matrix, but in dispersed form for example in the form of granules.

The ready-to-use kit with polymers can comprise: a first compartment I '') containing the polymerized ingredients; - a second compartment II '') containing the liquid fluorescent mixture for the extrusion kit.

The ready-to-use kit with polymers can be such as a secondary fluorophore as defined in the present description according to one or more of its variants, a polymerization solvent or their mixture is mixed with i) the polymerized ingredients and / or ii) the fluorescent mixture for extrusion kit.

The ready-to-use kit with polymers can also further comprise: - a secondary compartment containing the secondary fluorophore and / or a polymerization solvent.

Each kit can include a leaflet giving the abacus of the mixture to be produced between the main primary fluorophore and the additional primary fluorophore to obtain the desired fluorescence decay constant.

The components of each kit can be assembled, for the subsequent manufacture of the polymerization composition of the invention, in particular for simultaneous use, separate or spread over time. Other objects, characteristics and advantages of the invention will now be specified in the following description of particular embodiments of the invention, given by way of illustration and not limitation, with reference to Figures 1 to 8 attached.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 represents a table in which the fluorescence decay constant is measured for hybrid materials which are differentiated by the proportion between the primary primary fluorophore and the additional primary fluorophore and by the possible addition of a secondary fluorophore, as well as 'for comparison for a material containing no additional primary fluorophore.

Figure 2 represents the evolution of the median monoexponential tau fluorescence decrease constant as a function of the molar proportion between the primary primary fluorophore and the additional primary fluorophore according to the data in Figure 1. It may represent an abacus appearing in a notice delivered with a ready-to-use kit.

Figure 3 represents the pulse profile for different plastic scintillators, namely the evolution of their responses in number of strokes / seconds as a function of time expressed in nanoseconds. A pulse recording profile is superimposed on these profiles.

Figure 4 shows the energy spectra of a plastic scintillator of the invention and of a commercial slow plastic scintillator.

Figures 5 and 6 show a cross-sectional view of a “phoswich” type device for detection by plastic scintillation according to the invention, respectively without and with a bonding layer.

Figure 7 shows a variant of the device in Figure 6.

Figure 8 shows the schematic view of a scintillating optical fiber provided with a sheath.

EXPLANATION OF PARTICULAR EMBODIMENTS

Unless otherwise indicated, the examples are carried out at atmospheric pressure and ambient temperature. 1. Manufacture of a hybrid material for measurement by plastic scintillation according to the invention. 1.1. Example 1 of manufacturing a plastic scintillator with secondary fluorophore.

A liquid mixture comprising fluorescent molecules (5% by mass (3,624 g) of naphthalene as main primary fluorophore + 0.2% by mass (183 mg) of 2,5-diphenyloxazole (PPO) as additional primary fluorophore and 0.02% by mass (15.2 mg) of 9.10-diphenylanthracene (DPA) as a secondary fluorophore) to which is then added styrene (80 mL or 94.78% by mass) is introduced into a single-colored balloon beforehand dried under an inert argon atmosphere.

After five cold degassing under vacuum (known as the “freeze-pump-thaw” method in English), the polymerization medium obtained, returned to room temperature, is poured into a mold capable of giving the final shape to the plastic scintillator.

After five days of heating to 140 ° C of the sealed mold under an inert argon atmosphere, the plastic scintillator is removed from the mold, rectified and then polished. 1.2. Example 2 of manufacturing a plastic scintillator with secondary fluorophore.

A liquid mixture comprising fluorescent molecules (5% by mass of naphthalene (3.624 g) + 0.2% by mass of 2,5-diphenyloxazole (PPO, 183 mg) as primary fluorophores and 0.02% by mass of 1.4 -bis (4-methyl-5-phenyl-2-oxazolyl) benzene (dimethylPOPOP, 15.2 mg) as secondary fluorophore) to which are then added styrene (80 mL, 94.78% by mass) is introduced into a single-color balloon previously dried under an inert argon atmosphere.

After five degassing in cold vacuum, the polymerization medium obtained returned to room temperature is poured into a mold.

After five days of heating to 140 ° C of the sealed mold under an inert argon atmosphere, the plastic scintillator is removed from the mold, rectified and then polished. 1.3. Example 3 of manufacturing a plastic scintillator with crosslinked polymer matrix and secondary fluorophore.

A liquid mixture comprising fluorescent molecules (5% by mass of naphthalene (3.624 g) + 0.2% by mass of 2,5-diphenyloxazole (PPO, 183 mg) as primary fluorophores and 0.02% by mass of 9.10 - diphenylanthracene (DPA, 15.2 mg) as secondary fluorophore) to which are then added 80% by mass of styrene (64 ml) then 14.78% by mass of 1,4-butanediyl dimethacrylate (10.3 ml) in as a crosslinking agent is introduced into a single-color flask previously dried under an inert argon atmosphere.

After five degassing in cold vacuum, the polymerization medium obtained returned to room temperature is poured into a mold.

After ten days of heating the sealed mold to 65 ° C. under an inert argon atmosphere, the plastic scintillator is removed from the mold, rectified and then polished. 2. Manufacture of a range of plastic scintillators with variable proportion between the primary fluorophores.

Plastic scintillators are manufactured according to the characteristics specified in the table in Figure 1 according to a manufacturing process similar to that disclosed in the previous examples.

They differ by the chemical composition of the polymer matrix (St = polystyrene; St / 1,4 = mixture of styrene and 1,4-butanediyl dimethacrylate polymerized in a mass proportion between the two monomers respectively of 5 to 1) and by the molar ratio between the main primary fluorophore (naphthalene) and the additional primary fluorophore (2,5-diphenyloxazole = PPO). The mass concentration of each primary fluorophore is indicated as a percentage relative to the total mass of the plastic scintillator, the remainder therefore being constituted by the percentage by mass of the polymer matrix, of the other primary fluorophore, as well as by a constant concentration of 0.02% by mass of 9.10-diphenylanthracene (9.10-DPA) added as a secondary fluorophore not indicated in the table in Figure 1.

The fluorescence decay constant tau is measured by counting a single photon resolved in time as previously described. It is generally obtained here by biexponential type adjustment of the values obtained, weighting factors for each exponential component being indicated as a percentage in parentheses. In order to facilitate the comparison between the different plastic scintillators, the biexponential tau is converted into a median monoexponential tau in accordance with the equation below for which the quality of the adjustment of the measurement relative to the light pulse is evaluated by the Chi-square which should ideally be the closest to 1. Alternatively, commercial time-resolved single photon counting devices automatically calculate the median monoexponential rate or even the biexponential rate from the recorded data.

The monoexponential constant tau of median decrease in fluorescence can be calculated from the following formula: ^ median = ^ fast ^ fast + ^ slow

The percentages “fast%” and “slow%” represent the respective weights of fast and slow decay. They are adjusted to best describe the median decay. Their sum is equal to 100%.

Thus, Figure 2 represents the evolution of the fluorescence decrease constant tau median monoexponential (tau median monoexponential) as a function of the naphthalene / PPO molar ratio. It clearly shows the continuous evolution of the fluorescence decay constant as a function of the molar ratio between the primary primary fluorophore and the additional primary fluorophore. This evolution takes the form of a decreasing exponential which is the signature of a synergy between the primary primary fluorophore and the additional primary fluorophore. In the absence of such a synergy, the evolution of the time constant as a function of the molar ratio would be in the form of a linear straight line which would directly connect the value to 100% and to 0% reflecting the simple progressive replacement of one primary fluorophore by another.

Another advantage of using a hybrid material for measurement by plastic scintillation is shown in Figure 3 which illustrates the type of response pulse obtained for a plastic scintillator referenced by an index in the figure: fast (index a ): “Eljen EJ-200” reference scintillator sold by the company Eljen Technology; - slow (index b): “Eljen EJ-240” reference scintillator marketed by the company Eljen Technology; - hybrid (index c): comprising the hybrid material according to the invention.

The recording profile used (500 ns with a noise of 10 strokes / seconds) is superimposed on the pulses of these three plastic scintillators.

Figure 3 demonstrates the advantages of a phoswich plastic scintillator comprising a fast compartment and a hybrid compartment according to the invention compared to a phoswich plastic scintillator comprising a fast compartment and a slow compartment: for an electronic noise for example estimated at 10 shots per second, the hybrid pulse of the hybrid compartment has a better signal-to-noise ratio than the slow pulse of the slow compartment, thanks to the higher amplitude of the hybrid pulse. The acquisition is carried out by opening a time gate for recording these pulses. As indicated previously, the duration of this recording is generally chosen to be 6 to 10 times greater than the highest fluorescence decay constant, this decay constant corresponding for each pulse to the abscissa width of the pulse expressed in nanoseconds . In the event of high counting rates, such as for example when a radioactive source of high activity is placed in the presence of the phoswich device, the use of a slow compartment therefore implies using a much longer recording window: several pulses can then coexist in the same time window (stacking phenomenon), which then results in acquisition errors in the absence of discrimination of these pulses.

These properties of a hybrid compartment are therefore particularly advantageous for the discrimination of beta particles in a gamma radiation environment with a “phoswich” device comprising a hybrid compartment (in particular when it is the thinnest compartment) and a rapid compartment, each of these two compartments detecting the beta particle and the gamma radiation respectively. 3. Example of a qualitative or quantitative measurement of a radioactive material in plastic scintillation according to the measurement method of the invention. 3.1. Measurement protocol.

A plastic scintillator comprising the hybrid material of the invention in which a secondary fluorophore is incorporated is connected by means of optical grease to a photomultiplier tube which fulfills the function of photodetector of an electronic acquisition module.

Following its exposure to radioactive material, the plastic scintillator emits scintillation photons which are converted into an electrical signal by the photomultiplier tube supplied with high voltage.

The electrical signal is then acquired and analyzed with an oscilloscope, spectrometry software or an electronic acquisition card. The data thus collected is then processed by computer.

This analysis results in an energy spectrum histogram representing the channels on the abscissa (derived from an output energy) and on the ordinate the number of strokes / seconds. After calibration with a known gamma emitting source of energy, the energy of the radioactive material to be measured is determined. 3.2. Quantitative measurement with the scintillator.

On the basis of this measurement protocol, a quantitative measurement is carried out with a radioactive beta-chlorine-36 source of activity over 4 n equal to 6 kBq. This source is placed on the upper part of the plastic scintillator.

A cylindrical plastic scintillator of circular section, diameter 49 mm and height 35 mm (reference F30B in the table of Figure 1) is coupled with Rhodorsil RTV141A optical grease to the photocathode of a photomultiplier (model Hamamatsu H1949-51) powered by a high voltage (Ortec 556 model). The outgoing signal from the photomultiplier is recovered and then digitized by an electronic card specific to the inventor. This card can be replaced by another equivalent electronic card (for example CAEN DT5730B model) or an oscilloscope (for example Lecroy Waverunner 640Zi model).

Firstly, an energy calibration of the system (scintillator + photomultiplier) is carried out using 2 radioactive sources: one emitting gamma rays in the area [0 - 200 keV] and the other in the area [500 - 1.3 MeV]. This energy calibration is carried out by locating the channel corresponding to 80% of the amplitude of the Compton front. For example, if the ordinate of the Compton front corresponds to 100 strokes per second, the abscissa on the falling of the Compton front at 80 strokes per second associates the energy of the Compton front (in keV) with the channel.

In a second step, this calibration carried out, the beta source of chlorine-36 is attached to the upper face of the plastic scintillator. Analysis of the energy spectrum gives a read activity of 2.1 kBq (and therefore an intrinsic efficiency according to which 70% of the incident radiation is measured) and a photoelectric peak centered around 250 keV.

The energy spectrum of the hybrid plastic scintillator obtained is shown in Figure 4 (index (c ')). For comparison, it is superimposed on that of a slow plastic scintillator ("Eljen EJ-240 slow" marketed by the company Eljen Technology - index (b ') in Figure 4) whose intrinsic efficiency measured is 54% . 4. Geometries of a device for detection by plastic scintillation according to the invention.

Such a device is described with reference to FIGS. 5 and 6 which represent, along a longitudinal axis with reference to the radiation R, sections of a plastic scintillator of parallelepiped shape of the "phoswich" type. Thus, unless otherwise indicated, each part of the device shown here is of parallelepiped shape. The same reference numerals designate the same elements in these two figures. 4.1. Device with bonding layer.

According to a first embodiment illustrated in FIG. 5, the plastic scintillation detection device D of the invention comprises a part according to the invention which is a first hybrid plastic scintillator element 1 consisting of all or part of the hybrid material of the invention, and a second fast plastic scintillator element 2. These elements are respectively located upstream and downstream with respect to the direction R of propagation of the incident radiation (or of the incident particle) on the phoswich scintillator. By convention, they are therefore designated in the following description by "upstream hybrid scintillator 1" and "fast downstream scintillator 2". In the configuration illustrated in FIG. 5, the upstream hybrid scintillator 1 is said to be “thin”, since it is of shorter longitudinal thickness than the downstream fast scintillator 2 said to be “thick”. The device for detection by plastic scintillation of the invention having all these characteristics shows a discrimination between gamma rays and beta particles which is improved.

The upstream hybrid scintillator 1 and the downstream fast scintillator 2 are possibly contained in an envelope 8 which can constitute the housing or the frame of the device. They are fixed to each other with an optical interface layer forming a bonding layer 5.

The bonding layer 5 is generally a separate layer from the upstream hybrid scintillator 1 and from the downstream fast scintillator 2, for example an addition layer. However, it can be a layer composed of an intermediate material resulting from the fusion of the material of the upstream hybrid scintillator 1 and the downstream fast scintillator 2, as for plastic scintillation detectors comprising two scintillators linked to each other by pressing thermomechanical.

The bonding layer 5 can be an optical layer which is transparent to luminescent radiation. It can be composed of a binding material chosen from greases, glues, gels, optical cements, elastomeric compounds, silicone compounds usually used in the optical field. Such a material lets in the light radiation coming out of the downstream scintillator.

A photodetector 3 (such as for example a photomultiplier) is fixed to the downstream fast scintillator 2 with an optical interface layer 6. It is able to collect the radioluminescent radiation resulting from the contact of an ionizing particle or of ionizing radiation with scintillators 1 and 2.

The face of the upstream hybrid scintillator 1 which first receives the incident radiation in the direction of propagation R to be detected is covered with a metallic layer 4 which is here fine. This metallic layer 4 constitutes an entry window with which the incident radiation (or the incident particle) comes into contact, while preventing ambient light also from coming into contact with the upstream scintillator by isolating it from light. The side faces of the upstream and downstream scintillators are covered with a reflector or light diffuser 7 composed of a reflective material comprising for example aluminum (aluminized mylar, aluminum foil, etc.) or composed of a diffusing material including, for example, teflon, a paint based on titanium oxide TiCh, a paint based on magnesium oxide MgO, Millipore filter paper. 4.2. Device without bonding layer.

According to a second embodiment illustrated in Figure 6, the plastic scintillation detection device D of the invention has a structure as described in document NO 2013076279 [reference 11]. It therefore does not include a bonding layer such as the optical interface layer 5 described in FIG. 5. The device for detection by plastic scintillation without a bonding layer of the invention nevertheless differs from that described in reference [8 ] by the fact that it comprises a first hybrid plastic scintillator element consisting of all or part of the hybrid material of the invention.

The plastic scintillation detection device D of the invention without the bonding layer illustrated in FIG. 6 comprises a first hybrid plastic scintillator element 1 made wholly or partly of the hybrid material of the invention, and a second rapid plastic scintillator element 2 These elements are respectively located upstream and downstream with respect to the direction R of propagation of the incident radiation (or of the incident particle) on the phoswich scintillator. In the configuration illustrated in FIG. 5, the upstream hybrid scintillator 1 is said to be “thin”, since it is of shorter longitudinal thickness than the downstream fast scintillator 2 said to be “thick”. The device for detection by plastic scintillation of the invention having all these characteristics shows a discrimination between gamma rays and beta particles which is improved.

The upstream hybrid scintillator 1 and the downstream fast scintillator 2 are in direct contact and fixed to each other by an autogenous coupling process. In this coupling process, a first crosslinked plastic scintillator is prepared and then polymerized. After this first solid formulation, the monomer solution containing the fluorescent mixture to make the second scintillator is poured onto the first scintillator, the assembly is then put to heat.

The scintillators 1 and 2 are possibly contained in an envelope 8 which can constitute the housing or the frame of the device.

A photodetector 3 (such as for example a photomultiplier) is fixed to the downstream fast scintillator 2 with an optical interface layer 6. It is able to collect the radioluminescent radiation resulting from the contact of an ionizing particle or of ionizing radiation with scintillators 1 and 2.

The face of the upstream hybrid scintillator 1 which first receives the incident radiation (or the incident particle) according to the direction of propagation R to be detected is covered with a layer opaque to light 9. This opaque layer 9 constitutes an entry window with which the incident radiation comes into contact, while limiting the contact of ambient light with the upstream scintillator.

The lateral faces of the upstream and downstream scintillators are covered with a light reflector or diffuser 7. The light opaque layer 9 is permeable to the passage of beta and gamma rays. It is composed of an opaque material such as for example Mylar.

As indicated above, the upstream hybrid scintillator 1 can have a thickness that is thinner than the downstream fast scintillator 2. Such a configuration and shown in Figure 7. 4.3. Sparkling optical fiber.

Figure 8 shows a scintillating optical fiber 10 of cylindrical section. It comprises a polymer fiber 11 composed in whole or in part of the hybrid material of the invention. The polymer fiber 11 constituting the internal core of the fiber is covered with a sheath 12 covering the polymer fiber and composed in whole or in part of a sheathing material.

The present invention is not limited to the embodiments described and shown, and a person skilled in the art will know how to combine them and bring to it, with his general knowledge, many variants and modifications. The invention is applicable to the fields where scintillators are used, in particular: in the industrial field, for example for the measurement of physical parameters of parts during manufacture, for the non-destructive inspection of materials, for the control of the radioactivity at points of entry and exit from sites and for the control of radioactive waste. in the geophysical field, for example for the evaluation of natural radioactivity in soils. - in the field of fundamental physics and, in particular, nuclear physics. - in the field of the security of goods and people, for example for the security of critical infrastructures, the control of goods in circulation (luggage, containers, vehicles ...) as well as for the radiation protection of workers in the industrial sectors, nuclear and medical. - in the field of medical imaging.

REFERENCES CITED

[1] Moser, S. W .; Harder, W. F .; Hurlbut, C. R .; Kusner, M. R. "Principles and practice of plastic scintillator design", Radiat. Phys. Chem., 1993, Vol. 41, No. 1/2, 31-36.

[2] Bertrand, G. H. V .; Hamel, M.; Sguerra, F. "Current status on plastic scintillators modifications", Chem. Eur. J., 2014, 20, 15660-15685.

[3] Wilkinson, D. H. "The Phoswich - A Multiple Phosphor", Rev. Self. Instrum. 1952, 23, 414-417.

[4] M. Wahl, "Time-Correlated Single Photon Counting", technical note from PicoQuant, 2014.

[5] D. V. O'Connor, D. Phillips, Time Correlated Single Photon Counting, Academie Press, New York, 1984, pages 25 to 34.

[6] Rohwer, L. S., Martin, J. E .; "Measuring the absolute quantum efficiency of luminescent materials", J. Lumin. 2005, 115, pages 77-90.

[7] Velapoli, R. A .; Mielenz, K. D. "A Fluorescence Standard Reference Material: Quinine Sulfate Dihydrate", Appl. Opt., 1981, 20, 1718.

[8] WO 2013076281.

[9] Engineering techniques, Extrusion - single screw extrusion (part 1), Reference AM3650, publication of 2002.

[10] Engineering techniques, Radioactivity measurements by liquid scintillation, Reference p2552, publication of 03/10/2004.

[11] WO 2013076279.

Claims (49)

CLAIMS 1) Device for detection by plastic scintillation comprising a part for detection by plastic scintillation as a hybrid plastic scintillator element, the part being composed in whole or in part of a hybrid material comprising: - a polymer matrix; and, a fluorescent mixture incorporated into the polymer matrix and comprising in molar concentration relative to the total number of moles of primary fluorophore in the incorporated fluorescent mixture i) 80% to 99.6 mol% of a main primary fluorophore consisting of naphthalene and ii) 0.4% to 20 mol% of an additional primary fluorophore, the centroid of the light absorption spectrum and the fluorescence emission spectrum of which have respectively a wavelength between 250 nm and 340 nm and between 330 nm and 380 nm, the fluorescence decrease constant is between 1 ns and 10 ns, and the quantum yield of fluorescence in an apolar solvent is between 0.2 and 1; the part being coupled to an electronic acquisition module so that the module is able to collect the radioluminescent radiation emitted by the part when the latter is brought into contact with ionizing radiation or an ionizing particle. 2) Device for detection by plastic scintillation according to claim 1, in which the polymer matrix is composed wholly or in part of at least one polymer comprising repeating units resulting from the polymerization of monomers comprising at least one aromatic group, ( meth) acrylic or vinyl. 3) Device for detection by plastic scintillation according to claim 1 or 2, wherein the polymer matrix consists entirely or in part of at least one crosslinked polymer. 4) Device for detection by plastic scintillation according to any one of the preceding claims, in which the hybrid material comprises 1% by mass to 25% by mass of the incorporated fluorescent mixture. 5) Device for detection by plastic scintillation according to any one of the preceding claims, in which the incorporated fluorescent mixture comprises 90% to 99.1 mol% of the main primary fluorophore. 6) Device for detection by plastic scintillation according to any one of the preceding claims, in which the additional primary fluorophore has a quantum yield of fluorescence in an apolar solvent of between 0.5 and 1. 7) Device for detection by plastic scintillation according to any one of the preceding claims, in which the additional primary fluorophore is covalently linked to the polymer matrix. 8) Device for detection by plastic scintillation according to any one of the preceding claims, in which the incorporated fluorescent mixture further comprises a secondary fluorophore. 9) Device for detection by plastic scintillation according to claim 8, in which the secondary fluorophore has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 405 nm and 460 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1. 10) Device for plastic scintillation detection according to claim 8, in which the secondary fluorophore has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 460 nm and 550 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1. 11) Device for detection by plastic scintillation according to claim 8, in which the secondary fluorophore has a light absorption spectrum and a fluorescence emission spectrum whose centroid is respectively at a wavelength between 330 nm and 380 nm and between 550 nm and 630 nm, and whose quantum fluorescence yield in an apolar solvent is between 0.5 and 1. 12) Device for detection by plastic scintillation according to any one of claims 8 to 11, in which the secondary fluorophore is at a mass concentration relative to the mass of the hybrid material which is between 0.002% and 0.5% by mass . 13) Device for detection by plastic scintillation according to any one of the preceding claims, in which the hybrid material has a fluorescence decrease constant between 10 ns and 90 ns. 14) Device for detection by plastic scintillation according to any one of the preceding claims, in which the part has a parallelepiped or cylindrical shape. 15) Device for detection by plastic scintillation according to claim 14, in which the part of parallelepiped shape is a plastic scintillator compartment able to be incorporated in a device for detection by plastic scintillation. 16) Device for detection by plastic scintillation according to claim 14, in which the part of cylindrical shape is a scintillating optical fiber (10) comprising a polymer fiber (11) composed in whole or in part of the hybrid material and provided or not with a sheath (12) covering the polymer fiber and composed in whole or in part of a cladding material for optical fiber whose refractive index is lower than that of the hybrid material, the hybrid material comprising a polymer matrix constituted wholly or in part of at least one polymer which is not crosslinked. 17) Device for detection by plastic scintillation according to claim 16, in which the sheathing material is chosen from poly (methyl methacrylate), poly (benzyl methacrylate), poly (trifluoromethyl methacrylate), poly ( trifluoroethyl methacrylate) or mixtures thereof. 18) Device for detection by plastic scintillation according to any one of the preceding claims, in which the hybrid plastic scintillator element is a first hybrid plastic scintillator element (1), the device further comprising a second fast plastic scintillator element (2 ) whose fluorescence decay constant is lower than that of the first hybrid plastic scintillator element (1), these plastic scintillator elements (1) and (2) forming a plastic scintillator assembly. 19) Device for plastic scintillation detection according to claim 18, in which the device is of the phoswich type. 20) Device for detection by plastic scintillation according to claim 18 or 19, wherein the first hybrid plastic scintillator element (1) is composed in whole or in part of a hybrid material whose fluorescence decay constant is between 70 ns and 80 ns. 21) Device for detection by plastic scintillation according to any one of claims 18 to 20, wherein the first hybrid plastic scintillator element (1) is in direct contact with the second fast plastic scintillator element (2). 22) Device for detection by plastic scintillation according to any one of claims 18 to 20, in which the first hybrid plastic scintillator element (1) is in contact with the second rapid plastic scintillator element (2) by means of a bonding layer (5). 23) Device for detection by plastic scintillation according to any one of claims 18 to 22, in which, with reference to the direction R of propagation of the ionizing radiation or of the ionizing particle with respect to the device, the first scintillator element hybrid plastic (1) is the upstream plastic scintillator and the second fast plastic scintillator (2) is the downstream plastic scintillator. 24) Device for detection by plastic scintillation according to any one of claims 18 to 23, in which the plastic scintillator elements (1) and (2) have different thicknesses, so that the device comprises a thin plastic scintillator element and a thick fast scintillator element. 25) Device for detection by plastic scintillation according to claim 24, comprising a first hybrid plastic scintillator element (1) thin and a second fast plastic scintillator element (2) thick. 26) Device for detection by plastic scintillation according to claim 25, comprising the first hybrid plastic scintillator element (1) fine upstream and the second fast plastic scintillator element (2) thick downstream, by reference to the direction R of propagation of the radiation ionizing or ionizing particle vis-à-vis the device. 27) Device for detection by plastic scintillation according to any one of claims 24 to 26, in which the thin plastic scintillator element has a thickness of 10 μm to 1 mm and the thick plastic scintillator element has a thickness of 1 mm at 10 cm. 28) Device for detection by plastic scintillation according to any one of claims 18 to 27, in which the second fast plastic scintillator element (2) has a fluorescence decay constant between 1 ns and 7 ns. 29) Device for detection by plastic scintillation according to any one of claims 18 to 28, in which the second rapid plastic scintillator element (2) comprises a polymer matrix as defined according to any one of claims 1 to 3 and a rapid primary fluorophore chosen from 2,5-diphenyloxazole (PPO), [para] -terphenyl (pTP), [meta] -terphenyl (mTP), biphenyl, 2-phenyl-5- (4-biphenyl) -1,3,4-oxadiazole (PBD), 2- (4'-t-butylphenyl) -5- (4 "-biphenylyl) -1,3,4-oxadiazole (butyl-PBD), anthracene or their mixtures. 30) Device for detection by plastic scintillation according to claim 29, wherein the rapid primary fluorophore is 2,5-diphenyloxazole (PPO), [para] -terphenyl (pTP) or a mixture thereof. 31) Device for detection by plastic scintillation according to any one of claims 18 to 30, in which the second rapid plastic scintillator element (2) comprises a secondary fluorophore as defined by any one of claims 8 to 12. 32) Device for detection by plastic scintillation according to any one of the preceding claims 1 to 17, in which the part comprises a single hybrid plastic scintillator element. 33) Device according to any one of the preceding claims, in which the part is coupled to the electronic acquisition module by an optical interface layer (6). 34) Device according to any one of the preceding claims, in which the electronic acquisition module comprises a photodetector (3). 35) Device according to claim 34, wherein the photodetector (3) is a photomultiplier, a photodiode, a CCD charge transfer camera or a CMOS sensor. 36) Device according to any one of the preceding claims, in which the electronic acquisition module is placed downstream, by reference to the direction R of propagation of the ionizing radiation or of the ionizing particle with respect to the device, of the piece, of the single hybrid plastic scintillator element, of the first hybrid plastic scintillator element (1) or of the second rapid plastic scintillator element (2). 37) Apparatus for detection by plastic scintillation comprising a device as defined in any one of claims 1 to 36, consisting of a portable device for the detection of ionizing radiation, a detection portal or a CCD detector. 38) Method for manufacturing a device for detection by plastic scintillation as defined by any one of claims 1 to 36, in which the part as a hybrid plastic scintillator element is coupled to the electronic acquisition module, so that the module is able to collect the radioluminescent radiation emitted by the part when the latter is brought into contact with ionizing radiation or an ionizing particle. 39) Method for manufacturing a device according to claim 38, in order to manufacture a device as defined according to any one of claims 18 to 36, except for claim 32, comprising a plastic scintillator assembly, the method comprising the following successive steps: a '') having a first hybrid plastic scintillator element (1) as a part and a second fast plastic scintillator element (2) whose fluorescence decay constant is less than that of the first hybrid plastic scintillator element (1); each of these plastic scintillator elements further having a polished surface of the same dimension as that of the other plastic scintillator element; b '') coupling, via their polished surface, the first hybrid plastic scintillator element (1) and the second rapid plastic scintillator element (2) in order to obtain the plastic scintillator assembly; c '') coupling the plastic scintillator assembly comprising the part to the electronic acquisition module, so that the module is able to collect the radioluminescent radiation emitted by the plastic scintillator assembly when the latter is brought into contact with radiation ionizing or an ionizing particle. 40) A method of manufacturing a device according to claim 39, wherein the step b '') of coupling coupling is performed by heating the polished surface of the first hybrid plastic scintillator element (1) and the second plastic scintillator element fast (2) in order to soften these surfaces which are then pressed against each other in order to couple them. 41) Method for manufacturing a device according to claim 38, in order to manufacture a device as defined according to any one of claims 18 to 36, except for claim 32, comprising a plastic scintillator assembly, the method comprising the following successive steps: a '' ') a plastic scintillator element, constituted by a first hybrid plastic scintillator element (1) as a part or by a second fast plastic scintillator element (2) whose fluorescence decay constant is lower than that of the first hybrid plastic scintillator element (1), is produced in situ by polymerization on the other plastic scintillator element which constitutes a polymerization support, in order to obtain a plastic scintillator assembly at the end of step a '' '); b '' ') the plastic scintillator assembly comprising the part is coupled to the electronic acquisition module, so that the module is able to collect the radioluminescent radiation emitted by the plastic scintillator assembly when the latter is brought into contact with ionizing radiation or an ionizing particle. 42) A method of manufacturing a device according to any one of claims 39 to 41, in which the coupling between the plastic scintillator elements (1) and (2) according to step b ''), and / or the coupling according to which the electronic acquisition module is coupled with the plastic scintillator assembly according to step c '') or step b '' ') or with the single hybrid plastic scintillator element as defined in claim 32, is produced by means of an optical interface layer (6). 43) A method of manufacturing a device according to claim 42, wherein the optical interface layer (6) is an optical grease, an optical cement or a coupling solvent. 44) Method of measurement by plastic scintillation, the method comprising the following successive steps: i) a device as defined according to any one of claims 1 to 36 or an apparatus as defined according to claim 37 is brought into contact with a ionizing radiation or an ionizing particle so that the part included in the device emits radioluminescent radiation; and ii) the radioluminescent radiation is measured with the electronic acquisition module of the device. 45) A method of scintillation measurement according to claim 44, wherein the duration of decrease of the radioluminescent radiation measured is between 10 ns and 90 ns. 46) A method of scintillation measurement according to claim 45, wherein the duration of decay of the radioluminescent radiation measured is between 15 ns and 80 ns. 47) A method of scintillation measurement according to any one of claims 44 to 46, in which the ionizing radiation or the ionizing particle comes from a radioactive material emitting gamma rays, X-rays, beta particles, alpha particles or neutron. 48) A method of scintillation measurement according to claim 47, in which a discrimination between gamma rays and beta particles is carried out during step b) of measurement. 49) Method for scintillation measurement according to any one of claims 44 to 48, in which the measurement method comprises a step iii) in which the presence and / or the quantity of the radioactive material is determined from the measurement of the radioluminescent radiation according to step ii).