JPS62247280A - Scintillator and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a scintillator with a very excellent sensitivity, by dispersing a component comprising finely powdered barium fluoride evenly in a transparent synthetic resin component containing a fluorescent material that could turn fluorescence from first and second fluorescent materials to a wavelength in a sensitivity range of a photoelectric conversion element. CONSTITUTION:(A) A first fluorescent material having an absorption band in a wavelength range of 150-200nm, a second fluorescent material having an absorption band in a wavelength range of 250-400nm and a fluorescent material that could turn fluorescence from the first and second fluorescent materials to a wavelength in a sensitivity range of a photoelectric conversion element and (B) finely powdered barium fluoride are arranged in a monomer allowed to form a transparent synthetic resin and polymerized. In the output wavelength from the scintillator thus formed, the refractive index of the A component and that of B component shall be equal in substance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a scintillator and a method for manufacturing the same. More specifically, the present invention relates to an improved barium fluoride scintillator and a method for manufacturing the same.

(Prior art) Barium fluoride single crystals are used as scintillators, which are radiation detection elements, and emit light when irradiated with radiation, but the emission wavelength is in the ultraviolet region and its components are of two types. One of them has a peak at 1 to 22011111, and the others have a peak at 330 nm. Therefore, this decay time differs greatly between the two types of components.

In other words, the component having a peak at 220 nm is 0.6 ns
, and the component having a 300n peak is 60Qns
It is. Such luminescence is usually converted into an electrical signal and detected using a photomultiplier tube.

However, when using a photomultiplier tube, which is a photoelectron conversion element, from such a scintillator, the sensitivity of a normal photomultiplier tube has a peak around 4QQnm, so the sensitivity is insufficient in the wavelength range of 220nm or 300nm. A sufficient and satisfactory detection could not be achieved.

In particular, the measurement sensitivity of the 220 nm component, which has a short decay time, was insufficient, so it was not suitable at all for fast measurements. Moreover, since the constituent elements of barium fluoride single crystal are fluorine and barium, it had only a weak sensitivity in the order of 1 to yi to neutrons. Organic scintillators such as plastic scintillators are known as scintillators for neutrons, but when neutrons and gamma rays are incident at the same time, it is difficult to measure them separately. One of the drawbacks of scintillators made of single crystal barium fluoride is that it is difficult to manufacture large and homogeneous scintillators.

(Problems to be Solved by the Invention) In order to overcome the first drawback of the barium fluoride single crystal scintillator as described in #, the present inventors attempted to use a wavelength converting agent in combination. It has been found that since the barium fluoride is a single crystal, it is extremely difficult to incorporate the wavelength converting agent into the barium fluoride.

Therefore, an object of the present invention is to provide a barium fluoride scintillator and a method for manufacturing the same, which have improved the various drawbacks of the prior art described in #.

To describe it in more detail, the first object of the present invention is to provide an improved fluorescent filter that has an output wavelength that is superior to that of a charge conversion element such as an ordinary photomultiplier tube and has characteristics suitable for rapid measurement. A second object of the present invention is to provide a barium chloride-based scintillator and a method for manufacturing the same, and a second object of the present invention is to have practical sensitivity to neutrons, and is preferably capable of discriminating measurement of γ-rays, β-rays, etc. The purpose of the present invention is to provide a barium fluoride scintillator for neutron measurement that is capable of measuring neutrons, and a method for manufacturing the same.A third objective is to provide a large-sized barium fluoride scintillator of any shape and a method for manufacturing the same. It is in.

(Means for solving the problem) The first and third objectives are (A) (a) 150-2
000 m wavelength range (first phosphor having an absorption band;
b) a second phosphor having an absorption band in the wavelength range of 250 to 400 nm; and (c) at least one phosphor for photoelectrically changing the fluorescence from the M1 and the second phosphor to a wavelength in the sensitivity range of the element. In a component made of a transparent synthetic resin containing a seed phosphor, a component made of powdered barium fluoride (rB)'1jIl is uniformly made into molecules, and the output wavelength from the scintillator thus formed is This is achieved by a scintillator characterized in that the refractive index of the AIi component and the refractive index of the B component are substantially equal.

The first and third objectives are also (■) (Δ) (a)
a first phosphor having an absorption band in the wavelength range of 150 to 200 nm; (b) a second phosphor having an absorption band in the wavelength range of 250 to 400 nm; (c) the first and second phosphors; At least one type of phosphor that changes the fluorescence from the phosphor to a wavelength in the sensitivity vI range of the charging conversion element, and (8) at least one type of phosphor capable of forming a transparent synthetic resin with finely powdered barium fluoride.
This can also be achieved by a method for producing a scintillator, which is characterized in that it is blended with a seed monomer, and then (11) the monomer is polymerized.

Previous: 2 The second object is achieved by making the scintillator contain hydrogen residues in a weight fraction of 0.001 or more. The present inventors conducted various studies to make a barium fluoride scintillator sensitive to neutrons, and found that it is sufficient to simultaneously contain hydrogen residues and barium fluoride powder in the scintillator. Surprisingly, it was found that the temporal characteristics of the light emission of the scintillator differ depending on whether the scintillator is exposed to γ-rays, β-rays, etc. We have achieved this goal. In other words, when γ-rays and β-rays are incident on the scintillator, most of the light emitted from the scintillator attenuates within 50 nsec, whereas when neutrons are incident, there is a slow component that attenuates within about 4.12 μsec. exist.

Once, the ratio of 50nsecT to the total luminescence amount: the amount of attenuated acid was 211! If I is determined, it becomes possible to discriminate whether the incident radiation is a neutron, a γ-ray, or a β-ray.

(Function) The present invention solves the disadvantages of barium fluoride crystal scintillators, which have emission peaks in two wavelength ranges that are completely different from the sensitivity peaks of ordinary photoelectron conversion elements, as described above, and the fact that they are sensitive to neutrons. The disadvantage of the scintillator, which does not have sensitivity, can be overcome by using an Ml phosphor having an absorption band in one wavelength range, and a second phosphor having an absorption band in the other wavelength range.
A phosphor that converts the fluorescence from the two-prize light body into a wavelength within the sensitivity range of the photoelectric conversion element is mixed with Ka0, Fup, Halium, and 1 powder, and this is transparently synthesized! M))'ij is modified by uniformly dispersing it in ij.

Therefore, the wavelength range of the absorption band of the first phosphor is 150 to 2
50nJ11, preferably 180-250nm,
Especially around 220 nm. Furthermore, the wavelength range of the M2 phosphor is 250 to 4000 m, preferably 300 to 350 nm.
It gained momentum at 1ll, and suddenly reached around 300r)m.

Examples of the first phosphor (a>) include naphthalene, polystyrene, polymethylstyrenes, polyvinylnaphthalene, etc.
It is blended in an amount of 10% by weight, preferably 0.01 to 5% by weight. When an organic polymer compound such as polystyrene is used as a fluorescent agent, it is preferably used as a copolymer component of the synthetic resin constituting the scintillator.

In addition, examples of the second phosphor (b) include p-terphenyl, 2,5-diphenyloxazole, 2-(4
-tert-butylphenyl)-5-(4-bisnoenyl)-1,3,4-oxadiazole, etc., and is 0.001 to 5% by weight, preferably 0.01 to 2% by weight based on the entire scintillator. It is blended. Furthermore, 2.5-bis-2-(5-tert
-butylbenzozolyl)-thiophene, 1.4-
Bis-2-(5-phenyloxacylyl) ~ benzene,
p-bis-(0-methylstyryl)-benzene, 4,4
There are ゛-bis-(2,5-dimethylstyryl)-diphenyl, etc., and it is 0.0005 to 5 for the entire scintillator nail.
It should be blended in an amount of 0.001 to 2% by weight, preferably 0.001 to 2% by weight.

The light emitted from the first phosphor can be converted to a longer wavelength side using a second phosphor, and then further converted to a longer wavelength side using a third phosphor.

Barium fluoride (BaF2) is used in fine powder form, and its average particle size is 100 μm or less, preferably 10 μm or less.
It is not more than μm, more preferably not more than 5 μm. The blending amount is 10 to 900 M per 100 parts by weight of transparent synthetic resin.
parts by weight, preferably 20 to 900 parts by weight. In other words, if the amount is less than 10 parts by weight, the rate at which the incident radiation loses 10 parts of energy in the resin component that makes up the scintillator increases, which not only causes a decrease in luminous efficiency but also reduces the amount of energy lost per average distance. Since the number of particles decreases, the scintillator has to be large in size and has the disadvantage of being one shot smaller. Further, the hydrogen residue contained in the synthetic resin component is preferably 0.1 to 8% by weight, more preferably 0.5 to 7% by weight, based on the entire scintillator. This is because if the hydrogen residue content is less than 0.1% by weight, the detection efficiency for neutrons will be insufficient.

As the synthetic resin used, the above-mentioned No. 1. It is desirable that the refractive index after blending the second and third phosphors is equal to the precipitation rate of barium fluoride at the final output wavelength as a scintillator.

-11. Since the refractive index of the phosphor is higher than that of barium fluoride, it is preferable that the synthetic resin used has a lower refractive index than barium fluoride; A resin having an appropriate refractive index is selected depending on the type and arrangement of the second and third phosphors.

Such resins include, for example, the following formulas I to JJI.
There are homopolymers and copolymers of monomers represented by

CH2=C-C0OR' (I) where R is H or CI-(, and R1 is CnHm
F, (n is an integer from 3 to 7, and m10=2n-1
It is. ) COCH12=C-COOR2(El) (However, R is H or CH3, and 1 and 2 are carbon 1 Toshi number co~
8, preferably 1 to 3 alkyl groups. ) (Also CH2=C-0COR3(III) (However, R is day or (or C1-(3, preferably G;
and R3 has a carbon atom number of 1 to 4, preferably 1
~3 alkyl groups. ) Examples of the monomer of formula (1) include 2,2,3.3-tetrafluoropropyl acrylate, 2.2.3.3-tetrafluoropropyl methacrylate, and 2.2.3-1-
Lifluoropropyl acrylate, 2,2.3-1 to Lifluoropropyl methacrylate, 2.2.3.3.4
．． 4,5,5,6,6,7.7-dozocafluorohebutylacryle-1-,2,2.3.3.4.4.5.5.
6.6.7.7-dozocafluoroheptyl methacryate and the like.

For example, methyl acrylate,
Methyl methacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate-1~, isopropyl methacrylate, D-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, 5ec-butyl acrylate, s
Examples include ec-butyl methacrylate, -butyl acrylate, and r-butyl methacrylate.

Monomers of formula III include, for example, vinyl acetate, vinyl propionate, vinyl acetate, and the like.

If necessary, a monomer (crosslinking agent) having at least two radically polymerizable carbon-carbon double bonds in the molecule may be added to these monomers. There is essentially no limit to the type and amount of the crosslinking agent, and V! does not impair the transparency of the resulting plastic scintillator. A monomer having two radically polymerizable carbon-carbon double bonds in the molecule is preferred. Particularly preferred crosslinking agents include, for example, the general formula 1v (wherein R is a hydrogen atom or a methyl group,
Further, n is an integer of 3 to 8, preferably an integer of 3 to 6. ), general formula V (wherein R is a hydrogen atomic number or a methyl group, and n is an integer of 3 to 8, preferably a !! number of 3 to 6), general formula Vt ( However, in the formula, R is a hydrogen atom or a methyl group.

) There is a compound represented by

Typically, crosslinking agents include, for example, 1,3-propanediol diacrylate, 1,4-butanediol diacrylate, 1,6-heimosandiol diacrylate, 1
, 3-propanediol dimethacrylate, ], 4-butanediol dimethacrylate, 1,6-hexanethiol dimethacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, propylene glycol diacrylate 1-, di Propylene glycol diacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol methacrylate, triethylene glycol dimethacrylate, propylene glycol dimethacrylate, dibropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, neopentyl glycol diacrylate 1. Neopentyl glycol dimethacrylate, pentaerythritol tetraacrylate,
Examples include pentaerythritol tetramethacrylate, glycerin 1-reacrylate, glycerin trimethacrylate, diallyl phthalate, and divinylbenzene. Among these compounds, the above formulas JV, V, and V
Compounds represented by l are preferred.

When using a compound represented by these formulas as a crosslinking agent, the amount of addition depends on the type of crosslinking agent used, but in general, the loading fraction relative to the monomer mixture is 0.001 to 0.001.
A range of 0.1 is preferred, and a range of 0.005 to 0.05 is particularly preferred. In other words, if the weight fraction is less than 0.001, the effect of improving physical properties is small, and the improvement effect generally reaches saturation at a weight fraction of 0.1, so adding more than this value is This is disadvantageous because it not only fails to achieve the desired effect, but also may impair the transparency of the resulting base resin.

Buy a scintillator using $1 as described above! In order to create a phosphor, it contains the above-mentioned phosphor! After blending 11 to the II polymer (however, chestnut (the C agent has a weight of less than % relative to the monomer) to initiate polymerization, Radius 7]/17 and 11 are added in advance under a predetermined condition A'1, This is done by adding powdered barium fluoride to the obtained partial polymer, kneading it under heating, and then molding it. After uniformly dispersing the barium chloride, polymerization is carried out under a predetermined groove '1 using a T-shaped polymer [[Type 1]. If barium fluoride is blended and then polymerized, the barium fluoride will not be dispersed uniformly, but it has the advantage that the amount of crosslinking agent added can also be increased. ~150'C
1 Preferably at 30-140°C for 0.5-100 hours,
Preferably it is carried out for 1 to 50 hours. The radical polymerization initiator is generally used in an amount of 0.0001 to 1% by weight, preferably 0.0005 to 1% by weight, based on the monomer mixture. Typical polymerization initiators include lauroyl peroxide, tert-butyl peroxide-based diisopropyl carbonate, penzoyl peroxide, dicumyl peroxide, tert-butyl peroxyacetate, and tert-butyl peroxyacetate.
-butylperoxybenzoate-1., di-tert-butyl peroxide, azobisisobutyronitrile, and the like.

Plastic scintillators manufactured by methods other than those described above are also included in the present invention as long as they do not depart from the scope of the present invention.

(actual airA> Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 t-butyl 7-methacrylate-8969, 4-fold constant (t, 10.0 parts by weight of neopentyl glycol dimethacrylate, 10.6 parts by weight of styrene, 10 parts by weight of p-terphenyl and p-bis-(O 1000 parts by weight of barium fluoride fine powder of 200 mesh or less and 2.0 parts of benzoyl peroxide as a polymerization initiator were added to a monomer mixture consisting of 0.2 parts by weight of benzene. The mixture was stirred and mixed.Then, the mixture was poured into a hard glass ampoule with a diameter of 4Qmm, and after vacuum degassing, it was sealed and vertically immersed in a water bath at a temperature of 80°C.Standed at 80'C for 15 hours. After polymerization, remove the ampoule from the water bath,
Polymerization was further carried out for 5 hours in an air bath at 120°C. The polymer was removed from the ampoule and cut and polished to a diameter of 20 nm1.
111. A transparent cylindrical scintillator with a height of 10 mm was obtained. The barium fluoride content of this scintillator is 55
The weight was 1, and the refractive index nd of the resin portion was 1.473 at 23°C. The amount of light emitted from the scintillator was measured using the apparatus shown in FIG. 1, and the results shown in Table 1 were obtained.

Example 2 Methyl methacrylate-5693, 5 parts d, 2,213.
3-tetrafluoropropyl methacrylate-1-356,
5ffiffi parts, neopendelgly]-ludimethacrylate 20.0 weight? 3) 3, 20.0 parts by weight of styrene, 2-(4-t-butylnoenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole 20.0
Part by weight and 2.0 parts by weight of 4,4-bis-(2,5-dimethylstyryl)-diphenyl were mixed with finely powdered barium fluoride 6000 having an average particle size of 0.8 μm.
Parts by weight and 0.5 parts by weight of tert-butylpero-based isopropyl carbonate as a polymerization initiator were added and mixed with stirring. Then, the mixture was made into a 60mm diameter
The mixture was poured into a hard glass ampoule, vacuum degassed, and then sealed. The ampoule was vertically immersed in a water bath at a temperature of 60'C for 36 hours of polymerization, and then in an air bath at 120'C for 5 hours. The cooling bond and polymer were taken out from the ampoule and cut and polished to obtain transparent cylindrical scintillators with a diameter of 50 m and a height of 50+ nm. The refractive index nd inside the scintillator was 1.475 at 23° C., and the barium fluoride content was 86%. Figure 3 shows the output waveforms measured with an oscilloscope when neutrons and β-rays are incident on the scintillator, and the distinction between neutrons from Δm-Be and β-rays using the 2111 constant system shown in Figure 4 is shown in Figure 4. The constant results are shown in Figure 5.

Example 3 Methyl methacrylate 723.9 parts by weight, 2,2.3,
3,4. /l, 5,5,6,6,7.7-dozocafluorohebutyl methacrylate 226.1 parts, 1,6-
Hexanethiol dimethacrylate 20. 1 part of O heavy ff, 1 part of styrene 20'4ff, 10. Potential barium fluoride was pulverized into a monomer mixture consisting of 14 parts of C and 1.0 parts of 2,5-his-2-(ri-1-butylbenzoosazolyl)-diophyl. Obtained 2500ff of fine powder of 400 mesh or less
The procedure was repeated in the same manner as in Example 1, except that 4 parts of i and 0.5 parts of lauroyl peroxide as a polymerization initiator were added (a cylindrical, transparent resin part with a height of 101IllIll, opened for 20 yen, and a refraction of the resin part) The rate nd is '1.47 at 23°C.
A scintillator with a barium fluoride content of 75% was obtained. The amount of light emitted from the scintillator was measured in the same manner as in Example 1, and the results shown in Table 1 were 1q.

East 1 person relative Luminescent scintillator Dimensions Luminescence amount Wavelength Example 1
20mmφX 1011111))1 156 4
15nllll Example 3 20+nmφx 10mm
1l 170 440nmBaF2 single crystal 20mm
φx 10mmH100220,300nm (Effect of the invention) As described above, the present invention provides (A) (a) 150-2
An Ml phosphor having an absorption band in the QQnm wavelength range,
b) A second material having an absorption band in the wavelength range of 250 to 400 nm.
(c) at least one type of phosphor that changes the fluorescence from the first and second phosphors to a wavelength in the sensitivity range of the photoelectric conversion element;
B) Since the scintillator is made by uniformly dispersing a component consisting of fine powdered barium fluoride, the emission wavelength unique to barium fluoride is absorbed by the first and second phosphors, and the convertible phosphor absorbs the emission wavelength unique to barium fluoride. Since the fluorescence from the first and second phosphors can be converted into the optimum growth region of the photoelectric conversion element, a scintillator with extremely high sensitivity can be obtained.

Furthermore, since barium fluoride is in the form of a 1j/i powder, it is impossible to incorporate the phosphor inside it as it is, but it is possible to incorporate it inside by uniformly dispersing it in a transparent resin component. A similar effect can be obtained. Furthermore, since the refractive indices of the Δ component and the B component are substantially equal at the output wavelength from the scintillator, the transparent synthetic tree I
There are no defects in optical properties due to the combination of JFj components.

In addition, in the scintillator manufacturing method according to the present invention, polymerization is performed after uniformly dispersing the phosphor component and powdered barium fluoride in the 151 body having a predetermined composition, so that the barium fluoride is only uniformly dispersed. However, there is an advantage that the layer containing the crosslinking agent can be added arbitrarily. Another great advantage of the present invention is that it is possible to easily manufacture a large scintillator of any shape that is easy to process and made of barium fluoride single crystal.

In general, the most important effect of the present invention is that the scintillator contains hydrogen residues, so barium fluoride single bonds a L,
: It is possible to detect neutrons that did not exist, and it is also possible to differentiate between gamma rays, beta rays, and neutrons. This means that in a field where gamma rays, beta rays, neutron beams, etc. are emitted simultaneously, only neutrons can be a
A solid scintillator with such performance has not been possible with the prior art.

As described above, the effects of the present invention are that it corrects the drawbacks of conventional barium fluoride single crystals, and also provides performance that barium fluoride single crystals did not originally have.
The present invention provides a completely VfT scintillator with an expanded or expanded range of applications.

[Brief explanation of drawings]

Figure 1 is a block diagram of Example 1, Example 2, and a barium fluoride single crystal luminescence measuring device, and Figure 2 is the luminescence quantity δ1.
Photoelectron intensifier (8 tubes (Hamamatsu Photonics R3) used for
29) Spectral sensitivity curve, Figure 3 (a> is a waveform diagram measured with an oscilloscope of the output from the scintillator when neutrons are incident on the scintillator of Example 2, Figure 311b>
is an output waveform diagram when β rays are input I'J, and Figure 4 is an output waveform diagram when β rays are input.
5 is a block diagram of a measuring device that discriminates neutrons from Am-F3e, and FIG. Person Kyowa Gas Chemical Industry Co., Ltd. 137
cs Figure 1: 1L table (nm) Figure 3 (a) (b)

Claims (4)

[Claims] (1) (A) (a) A first phosphor having an absorption band in a wavelength range of 150 to 200 nm, and (b) a wavelength range of 250 to 400 nm.
(c) at least one type of phosphor that changes the fluorescence from the first and second phosphors to a wavelength in the sensitivity range of the photoelectric conversion element; A component consisting of (B) fine powdered barium fluoride is uniformly dispersed in a component consisting of a transparent synthetic resin, and the refractive index of the component A at the output wavelength from the scintillator thus formed. and the refractive index of the B component are substantially equal. (2) A scintillator according to claim 1, which contains hydrogen residues in a weight fraction of 0.001 or more and barium fluoride in a weight fraction of 0.1 or more. . (3) (I) (A) (a) a first phosphor having an absorption band in the wavelength range of 150 to 200 nm, and (b) 250 to 4 nm;
a second phosphor having an absorption band in a wavelength range of 00 nm;
c) At least one type of phosphor that changes the fluorescence from the first and second phosphors to a wavelength in the sensitivity range of the photoelectric conversion element and (B) finely powdered barium fluoride can be used to form a transparent synthetic resin. blended with at least one monomer, then (
II) A method for producing a scintillator, which comprises polymerizing the monomer. (4) The method according to claim 3, wherein the refractive index of the A component and the refractive index of the B component of the synthetic resin are substantially equal at the output wavelength from the scintillator.