JP5176074B2 - Single crystal for scintillator - Google Patents

Description

  The present invention relates to a single crystal for a scintillator. More specifically, radiation such as gamma rays in the fields of radiology, physics, physiology, chemistry, mineralogy, and oil exploration for medical diagnosis positron CT (PET), cosmic ray observation, underground resource search, etc. The present invention relates to a single crystal for a scintillator used for a single crystal scintillation detector (scintillator).

  A scintillator made of an orthosilicate gadolinium compound using cerium as an activator has been put to practical use as a radiation detector such as positron CT because it has a short fluorescence decay time and a large radiation absorption coefficient. However, although such a scintillator has a fluorescence output larger than that of the BGO scintillator, it is only about 20% of the NaI (Tl) scintillator, and its improvement is desired.

A scintillator using a single crystal of cerium-activated lutetium orthosilicate represented by the general formula Lu _{2 (1-x)} Ce _2x SiO ₅ (see, for example, Patent Documents 1 and 2), a general formula Gd _{2− (x + y)} Ln use _x Ce _y SiO ₅ (Ln is that Sc, Tb, Dy, Ho, Er, Tm, Yb and at least one element selected from the group consisting of Lu) and cerium-activated orthosilicate lutetium gadolinium single crystal represented by Scintillators (see, for example, Patent Documents 3 and 4) and cerium represented by the general formula Ce _2x (Lu _1-y Y _y ) SiO ₅ Ce _2x (Lu _1-y Y _y ) _{2 (1-x)} SiO ₅ A scintillator using a single crystal of activated lutetium yttrium silicate (see, for example, Patent Documents 5 and 6) is known. In these scintillators, it is known that not only the crystal density is improved, but also the fluorescence output of the single crystal of the cerium activated orthosilicate compound is improved and the fluorescence decay time can be shortened.

  In recent years, single crystals for scintillators using praseodymium having a short fluorescence decay time as an activator to replace cerium have been studied, and the cerium-activated orthosilicate single crystal described in Patent Documents 1 to 6 above has been studied. It is expected as a faster scintillator. Particularly, as a scintillator for positron CT (PET) for medical diagnosis, a scintillator having high density and excellent time resolution is demanded for a high-performance next-generation apparatus.

  In general, the fluorescence decay time of an inorganic scintillator is affected by the crystal structure of the host single crystal and the concentration of the activator. However, the action of the activator species is large, and the inorganic scintillator uses praseodymium as the activator. Is generally known to exhibit a relatively fast fluorescence decay time of about 5 to 30 ns.

Regarding the characteristics of the praseodymium-activated lutetium orthosilicate single crystal scintillator represented by Lu _2-y Pr _y SiO ₅ (wherein y represents a number from 0.005 to 0.02), Non-Patent Document 1, etc. It is reported in.

  The fluorescence wavelength is broad fluorescence that includes light emitting components near 270 nm, 281 nm, and 314 nm and has a maximum value near 281 nm, and is at a low temperature (around 80 K) at room temperature (around 295 K), which is a practical temperature of a general scintillator. In comparison, the fluorescence output is reduced to about 70%, and it is particularly shown that the long wavelength component at 314 nm is significantly reduced.

  The excitation wavelength for generating the fluorescence when excited in the ultraviolet region has a peak near 247 nm, the fluorescence decay time due to ultraviolet excitation is 6 ns, the fluorescence decay time due to radiation excitation is 26 ns, etc. Has also been reported.

From these documents, the praseodymium-activated orthosilicate lutetium scintillator represented by the general formula Lu _2-y Pr _y SiO ₅ has a fluorescence wavelength of a photomultiplier tube generally used as a photodetector of the scintillator. Since a component of less than 300 nm whose sensitivity is extremely lowered is mainly used, it is considered that the fluorescence output cannot be sufficiently detected.

On the other hand, praseodymium-activated lutetium represented by (Pr _y Lu _1-y ) ₃ Al ₅ O ₁₂ (wherein y represents a number of 0.0025 to 0.01) using praseodymium as an activator. The characteristics of the aluminum garnet single crystal scintillator are reported in Non-Patent Document 2 and the like.

  The fluorescence wavelength is broad fluorescence that includes emission components near 255 nm, 305 nm, 325 nm, and 358 nm and has a maximum value at 305 nm. Except for a decrease in short wavelength components near 255 nm, it is low even at room temperature (near 295 K) ( It is shown that the fluorescence output is almost the same as (around 80K).

The excitation wavelength for generating the fluorescence when excited in the ultraviolet region has peaks near 285 nm and 240 nm, the fluorescence decay time due to ultraviolet excitation is 17 to 21 ns, and the fluorescence decay time due to radiation excitation is 20 ns. It has also been reported that it is ˜25 ns. The density is 6.7 g / cm ³ , and the fluorescence output is Bi ₄ Ge ₃ O ₁₂ (BG
It is shown to be higher than twice O).

A single crystal of praseodymium-activated lutetium orthosilicate represented by Lu _2-y Pr _y SiO ₅ has a large density of 7.4 and a fast fluorescence decay time, but the fluorescence wavelength is a general use of scintillators At room temperature (for example, 10 to 40 ° C.), because of a low wavelength and broad peak of 300 nm or less, when using a photomultiplier tube which is a general photo detector, its detection sensitivity is poor and sufficient There is a problem that it is impossible to detect an output.

_{(Pr y Lu 1-y)} 3 Al 5 single crystal praseodymium-activated lutetium aluminum garnet represented by _{O 12} has a fast fluorescent decay time, the fluorescence wavelength is the maximum value in the vicinity of 305 nm, The density was as small as 6.7 g / cm ³ and the fluorescence output was higher than twice that of BGO, which was insufficient for high-performance scintillator characteristics for the next generation.
Japanese Patent No. 2852944 U.S. Pat. No. 4,958,080 Japanese Examined Patent Publication No. 7-78215 US Pat. No. 5,264,154 US Pat. No. 6,624,420 US Pat. No. 6,921,901 Chemical Physics Letters, 410 (2005) p.218-221 Physical Static Solid (a) 202 (2005) R4-R6, Journal of Crystal Growth, 287 (2006) p. 335-338

  The present invention can obtain a fluorescence characteristic having a high density and a fast fluorescence decay time as a characteristic of a praseodymium-activated single crystal, and can be detected using a photomultiplier tube at room temperature. An object of the present invention is to provide a scintillator single crystal capable of obtaining a high-speed fluorescence output having a maximum value of 300 nm or more.

In order to achieve the above object, the present invention provides a single crystal for a scintillator comprising a single crystal of a praseodymium-activated orthosilicate compound represented by the following general formula (1).
Gd _{2- (x + y)} Lu _x Pr _y SiO ₅ (1)
(In general formula (1), x represents a number of 1 or more and less than 2, y represents a number of more than 0 and 0.1 or less, and x and y satisfy the condition represented by 2- (x + y)> 0. Fulfill.)

  The single crystal may be characterized in that in the excitation fluorescence spectrum measured at a temperature of 10 to 40 ° C., the fluorescence wavelength with respect to the excitation wavelength that gives the maximum value of the fluorescence output is 300 nm or more.

According to the single crystal of the present invention, the high density of Lu ₂ SiO ₅ is high because of the same crystal structure space group C2 / c in which Gd is substituted for the Lu site of the parent structure, and as a characteristic of praseodymium activation It is possible to obtain a fluorescence characteristic having a fast fluorescence decay time.

  According to the single crystal of the present invention, it is possible to obtain a high-speed fluorescence output having a maximum value of 300 nm or more that can be detected using a photomultiplier tube at room temperature.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

The single crystal of the present invention contains a single crystal of a praseodymium-activated silicate compound represented by the general formula (1).
Gd _{2- (x + y)} Lu _x Pr _y SiO ₅ (1)
(In general formula (1), x represents a number of 1 or more and less than 2, y represents a number of more than 0 and 0.1 or less, and x and y satisfy the condition represented by 2- (x + y)> 0. Fulfill.)

  In the single crystal of the present invention, since x and y in the general formula (1) are each in the above range, a high-speed that shows a maximum value near 312 nm that can be detected using a photomultiplier tube at room temperature. A fluorescence output can be obtained. Here, x is required to be 1 or more and less than 2 from the viewpoint of densifying the crystal and obtaining a high fluorescence output at room temperature, preferably more than 1.2 and less than 2, Is more preferably less than 2 and more preferably more than 1.8 and less than 2. Further, y must be greater than 0 and less than or equal to 0.1, preferably greater than 0 and less than 0.1, more preferably greater than 0.0001 and less than 0.05. More preferably, it is more than .0005 and less than 0.03, most preferably more than 0.001 and less than 0.01. If y is 0, sufficient fluorescence output cannot be obtained, and if it is greater than 0.1, the coloration of the crystal becomes remarkable, causing a problem of reduction in fluorescence output and generation of cracks due to crystal distortion.

  The single crystal may be composed of only a single crystal of the praseodymium-activated silicate compound represented by the above general formula (1), but among the elements belonging to Group 2 (IIa group) of the periodic table, Ca Further, one or more additive elements selected from Mg may be further contained. As a result, it is possible to reduce a decrease or variation in fluorescence characteristics that may be caused by oxygen defects, and to reduce the background (afterglow) of fluorescence output caused by crystal defects. The content of the additive element is preferably 0.00005 to 1.0 mass% with respect to the total mass of the single crystal of the praseodymium-activated silicate compound represented by the general formula (1).

  The single crystal may further contain one or more additive elements selected from Al, Ga, and In among elements belonging to Group 13 (Group IIIb) of the periodic table. You may contain with respect to the total mass of the said single crystal. Thereby, the effect of reducing the background (afterglow) of the fluorescence output resulting from crystal defects becomes more remarkable. Further, when the additive element is present at the same time as one or more additive elements selected from Ca and Mg among the elements belonging to Group 2 (Group IIa) of the periodic table, a higher effect may be obtained. . The content of the additive element is preferably 0.00005 to 1.0 mass% with respect to the total mass of the single crystal of the praseodymium-activated silicate compound represented by the general formula (1).

  Further, in the above single crystal, the total concentration of one or more elements selected from elements belonging to Groups 4, 5, 6 and 14, 15, 16 is represented by the general formula (1). The total mass of the praseodymium ortho-activated silicate compound can be 0.002% by weight or less. Thereby, deterioration of fluorescence characteristics can be suppressed.

  Next, an example of the method for producing the single crystal will be described.

  In the method for producing a single crystal according to the present embodiment, first, raw materials of the praseodymium-activated orthosilicate compound represented by the general formula (1) are mixed so as to have a predetermined stoichiometric composition, and are put into a crucible. . The starting material for producing this single crystal is a single oxide and / or composite oxidation of Gd, Lu, Pr and Si, which are constituent elements of the praseodymium-activated orthosilicate compound represented by the general formula (1) A thing is used suitably. As a commercially available product, it is preferable to use a highly pure product such as a product manufactured by Shin-Etsu Chemical Co., Ltd., Stanford Material Co., Ltd.

  In addition, one or more additive elements selected from Ca and Mg among the elements belonging to Group 2 (Group IIa) of the periodic table and Al, Ga, among elements belonging to Group 13 (Group IIIb) of the periodic table When one or more additional elements selected from In are further contained, the timing of adding these additional elements is not particularly limited as long as it is before crystal growth. For example, an additive element may be added and mixed when the raw material is weighed, or a group 2 element may be mixed when the raw material is charged into a crucible. Moreover, the aspect at the time of addition will not be specifically limited if an additive element is contained in the grown single crystal, For example, you may add in a raw material in the state of an oxide or carbonate.

  Next, the crucible filled with the above raw material is heated to melt the raw material (melting step), and then the molten liquid is cooled and solidified (cooling and solidifying step) to obtain a single crystal ingot.

  Here, the melting method in the melting step may be a Czochralski method. In this case, it is preferable to perform operations in the melting step and the cooling and solidifying step using the pulling device 10 having the configuration shown in FIG.

  FIG. 1 is a schematic cross-sectional view showing an example of a basic configuration of a growth apparatus for growing a single crystal in the manufacturing method according to the present embodiment. A pulling apparatus 10 shown in FIG. 1 has a high-frequency induction heating furnace 14. This high frequency induction heating furnace 14 is for continuously performing the operations in the melting step and the cooling and solidification step described above.

  The high-frequency induction heating furnace 14 is a bottomed container having a cylindrical side wall having fire resistance, and the shape of the bottomed container itself is the same as that used for single crystal growth based on the known Czochralski method. A high frequency induction coil 15 is wound around the side surface of the bottom of the high frequency induction heating furnace 14. A crucible 17 (for example, an Ir crucible) is disposed on the bottom surface inside the high-frequency induction heating furnace 14. This crucible 17 also serves as a high-frequency induction heater. When a single crystal raw material is put into the crucible 17 and high frequency induction is applied to the high frequency induction coil 15, the crucible 17 is heated to obtain a melt 18 (melt) made of a single crystal constituent material.

  In addition, an opening (not shown) penetrating from the inside of the high frequency induction heating furnace 14 to the outside is provided at the center of the bottom of the high frequency induction heating furnace 14. A crucible support bar 16 is inserted from the outside of the high-frequency induction heating furnace 14 through this opening, and the tip of the crucible support bar 16 is connected to the bottom of the crucible 17. By rotating the crucible support rod 16, the crucible 17 can be rotated in the high-frequency induction heating furnace 14. A space between the opening and the crucible support rod 16 is sealed with packing or the like.

  Next, a more specific manufacturing method using the pulling device 10 will be described.

  First, in the melting step, a single crystal raw material is put into the crucible 17 and high frequency induction is applied to the high frequency induction coil 15 to obtain a melt 18 (melt) made of a single crystal constituent material.

  Next, the columnar single crystal ingot 1 is obtained by cooling and solidifying the melt in the cooling and solidifying step. More specifically, the work proceeds in two steps, a crystal growth step and a cooling step described later.

  First, in the crystal growth process, the pulling rod 12 having the seed crystal 2 fixed to the lower end is introduced into the melt 18 from the upper part of the high frequency induction heating furnace 14, and then the single crystal ingot 1 is lifted while pulling the pulling rod 12. Form. At this time, in the crystal growth step, the heating output of the heater 13 is adjusted, and the single crystal ingot 1 pulled up from the melt 18 is grown until the cross section has a predetermined diameter.

  Next, in the cooling step, the heating output of the heater is adjusted to cool the grown single crystal ingot (not shown) obtained after the crystal growth step.

  In the manufacturing method according to this embodiment, it is preferable that the atmosphere for crystal growth contains oxygen in the range of 0.01 to 0.6% by volume. When the oxygen concentration is less than 0.01% by volume, oxygen defects are likely to occur in the crystal, and afterglow may increase. On the other hand, when the oxygen concentration exceeds 0.6% by volume, the fluorescence output may decrease due to coloring or the like.

  Further, in the manufacturing method according to the present embodiment, the single crystal can be heat-treated in an atmosphere containing oxygen or an atmosphere not containing oxygen after growth or after growth / processing. It is possible to obtain an effect of increasing the fluorescence output due to a decrease in coloring due to heat treatment. As the heat treatment temperature, a temperature of 700 ° C. to 1300 ° C. at which the above effect can be easily obtained can be applied.

The single crystal obtained as described above has a high density because of the same crystal structure space group C2 / c in which Gd is substituted for the Lu site of the high-density Lu ₂ SiO ₅ in the matrix structure, and praseodymium-activated It is possible to obtain a fluorescence characteristic having a fast fluorescence decay time as a characteristic.

  This single crystal can have excellent fluorescence characteristics that the fluorescence wavelength with respect to the excitation wavelength that gives the maximum value of the fluorescence output in the excitation fluorescence spectrum measured at a temperature of 10 to 40 ° C. is 300 nm or more. Thus, it is possible to obtain a fluorescence output in a wavelength region of 300 nm or more that can be detected using a photomultiplier tube.

  Therefore, this single crystal is used in fields such as radiology, physics, physiology, chemistry, mineralogy, and petroleum exploration for first medical diagnostic positron CT (PET), cosmic ray observation, underground resource search, etc. It is very useful as a single crystal for a scintillator used in a single crystal scintillation detector (scintillator) for radiation such as gamma rays.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Example 1]
The single crystal was produced based on the Czochralski method. _{First, Gd 2- (x + y)} Lu x Pr y SiO 5 (x = 1.8, y = 0.003) as starting materials, gadolinium oxide _(Gd 2 _{O 3,} 99.99 wt% purity), lutetium oxide (Lu ₂ O ₃ , purity 99.99 mass%), silicon dioxide (SiO ₂ , purity 99.9999 mass%), praseodymium oxide (Pr ₆ O ₁₁ , purity 99.99 mass%) are prepared, and these raw materials Were mixed so as to have a predetermined stoichiometric composition.

  Next, 500 g of the obtained raw material mixture was put into an iridium crucible having a diameter of 50 mm, a height of 50 mm and a thickness of 1.5 mm, and heated to a melting point of 2150 ° C. in a high frequency induction heating furnace to obtain a melt. The melting point was measured with an electronic optical pyrometer (manufactured by Chino, Pyrosta MODEL UR-U).

Subsequently, seeding was carried out by putting the tip of the lifting rod with the purpose crystal fixed to the tip into the melt. Thereafter, the shoulder of the single crystal ingot was pulled up at a crystal pulling speed of 1.5 mm / h, and when the diameter became 25 mm (φ), the growth of the parallel part was started at a pulling speed of 1 mm / h. After growing a crystal having a predetermined weight, the single crystal was separated from the melt and cooling was started. When growing the crystal, 4 L / min of N ₂ gas and 15 mL / min of O ₂ gas were kept flowing in the growth furnace. At this time, the oxygen concentration in the growth furnace was 0.4% by volume. Thus, a single crystal ingot having a crystal weight of 280 g, a shoulder portion of 30 mm, and a parallel portion of 90 mm was obtained. About the obtained single crystal ingot, the result of the segregation coefficient 0.7 of Gd and the segregation coefficient 0.35 of Pr was obtained from the result of the elemental analysis. The segregation coefficient is
Cs / Co = k (1-g) ^k-1 (2)
(Co: initial concentration in the melt, Cs: initial concentration in the crystal, k: segregation coefficient, g: solidification rate)
And the above equation (2).

Next, a 4 × 6 × 20 mm ³ sample was cut out from the upper part of the obtained single crystal, and the excitation fluorescence spectrum of the 6 × 20 mm surface of the sample was measured at room temperature. The sample was not heat-treated after single crystal growth or after growth / processing. The excitation fluorescence spectrum was measured in the range of excitation wavelength 200 to 400 nm and fluorescence wavelength 200 to 700 nm using a spectrofluorimeter (trade name F4500, manufactured by Hitachi, Ltd.). As a result, it was found that there was relatively sharp fluorescence near 312 nm. FIG. 2 shows an excitation spectrum (fluorescence wavelength: 312 nm). As shown in FIG. 2, in the case of the single crystal of Example 1, the excitation wavelength at which the fluorescence intensity was maximum was 276 nm. Moreover, the fluorescence spectrum in wavelength 276nm is shown in FIG. As shown in FIG. 3, in the case of the single crystal of Example 1, the fluorescence wavelength with respect to the excitation wavelength (276 nm) that gives the maximum value of the fluorescence output was 312 nm. Similarly, the fluorescence spectrum by X-ray excitation was observed with a fluorescence wavelength of 312 nm.

As described above, the excitation fluorescence characteristics of the single crystal obtained in Example 1 are Lu _{2 -y} Pr _y SiO ₅ (raw material composition y = 0.005 to 0. ₅ ) reported in Non-Patent Document 1 and the like. The characteristics of the praseodymium-activated lutetium orthosilicate single crystal scintillator represented by (02) are clearly different, and the single crystal of Example 1 has a wavelength of 300 nm or more detectable using a photomultiplier tube at room temperature. It was confirmed that a fluorescence output was obtained in the wavelength region.

[Example 2]
In general formula (1) in Example 1, y is 0.02, and 4 L / min of N ₂ gas and 0 mL / min of O ₂ gas are used in the growth furnace, and the oxygen concentration in the growth furnace at this time Produced a single crystal in the same manner as in Example 1 except that it was less than 0.02%.

  Next, with respect to the obtained single crystal, an excitation fluorescence spectrum was measured in the same manner as in Example 1. FIG. 2 shows an excitation spectrum, and FIG. 3 shows a fluorescence spectrum. As a result, the excitation wavelength at which the fluorescence intensity was maximum was 276 nm, and the fluorescence wavelength at a wavelength of 276 nm was 312 nm.

As described above, the excitation fluorescence characteristic of the single crystal obtained in Example 2 is similar to that of the single crystal of Example 1 as Lu _2-y Pr _y SiO ₅ (reported in Non-Patent Document 1 above). The characteristics of the praseodymium-activated lutetium orthosilicate single crystal scintillator represented by the raw material composition y = 0.005 to 0.02) were clearly different. It was confirmed that the single crystal of Example 2 can obtain a fluorescence output in a wavelength region of 300 nm or more that can be detected using a photomultiplier tube at room temperature.

[Comparative Example 1]
In the general formula Lu _2-y Pr _y SiO ₅ (where y is a number greater than 0 and less than or equal to 0.1), y is 0.02, and 4 L / min of N ₂ gas and and O ₂ gas 0 mL / min, the oxygen concentration in the growth furnace at this time, except less than 0.02% in the same manner as in example 1 to produce a single crystal.

[Comparative Example 2]
In the general formula Lu _2-y Pr _y SiO ₅ (where y is a number greater than 0 and less than or equal to 0.1), y is 0.003, 4 L / min of N ₂ gas and and O ₂ gas 0 mL / min, the oxygen concentration in the growth furnace at this time, except less than 0.02% in the same manner as in example 1 to produce a single crystal.

[Comparative Example 3]
Y in the general formula (1) is 0.003, and yttrium oxide (Y ₂ O ₃ , purity 99.99 mass) is used instead of gadolinium oxide (Gd ₂ O ₃ , purity 99.99 mass%) as a starting material. Example 1 except that 4 L / min N ₂ gas and 0 mL / min O ₂ gas were used in the growth furnace, and the oxygen concentration in the growth furnace at this time was less than 0.02%. In the same manner, a single crystal was produced.

Next, the excitation fluorescence spectrum of the single crystals obtained in Comparative Example 1, Comparative Example 2, and Comparative Example 3 was measured in the same manner as in Example 1. FIG. 2 shows an excitation spectrum, and FIG. 3 shows a fluorescence spectrum. Results similar to the characteristics of praseodymium-activated lutetium orthosilicate single crystal scintillator represented by Lu _2-y Pr _y SiO ₅ (raw material composition y = 0.005 to 0.02) reported in Non-Patent Document 1 and the like In the obtained excitation fluorescence spectrum, the excitation wavelength at which the fluorescence intensity becomes maximum is 248 nm, and the fluorescence wavelength at the wavelength of 248 nm is 276 nm, which includes a light emitting component near 312 nm, and has a broad value near 276 nm. It was fluorescent. The results are shown in Table 1. The “maximum fluorescence wavelength” in Table 1 means a wavelength that gives the maximum fluorescence intensity.

From the experimental results, the praseodymium-activated orthosilicate silicate scintillator represented by the general formula Lu _2-y Pr _y SiO ₅ has a fluorescence wavelength that is a sensitivity of a photomultiplier tube generally used as a photodetector of the scintillator. It is considered that the fluorescence output cannot be sufficiently detected because the component of less than 300 nm that is extremely reduced is mainly.

Praseodymium-activated orthosilicate represented by the general formula Gd _{2- (x + y)} Lu _x Pr _y SiO ₅ (x represents a number of 1 or more and less than 2, y represents a number of more than 0 and not more than 0.1) A single crystal for a scintillator containing a single crystal of a compound has a wavelength range of 300 nm or more that can be detected using a photomultiplier tube at room temperature by substituting Gd for the general formula Lu _2-y Pr _y SiO _5. It is considered that a fluorescence output can be obtained.

It is a schematic cross section which shows an example of the basic composition of the growth apparatus used for the growth of a single crystal. It is a graph which shows the excitation spectrum of the single crystal obtained in Example 1 and Example 2 (fluorescence wavelength 312nm), the comparative example 1, the comparative example 2, and the comparative example 3 (fluorescence wavelength 276nm). 3 is a graph showing fluorescence spectra at an excitation wavelength of 276 nm (in the case of Examples 1 and 2) and 248 nm (in the case of Comparative Examples 1, 2, and 3) at which the fluorescence intensity of FIG. 2 is maximum.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Single crystal, 2 ... Seed crystal, 10 ... Lifting device, 12 ... Lifting rod, 14 ... High frequency induction heating furnace, 15 ... High frequency induction coil, 16 ... Crucible support rod, 17 ... Crucible, 18 ... Melt (melt) ).

Claims (2)

1. A scintillator single crystal comprising a single crystal of a praseodymium-activated orthosilicate compound represented by the following general formula (1).
Gd _{2- (x + y)} Lu _x Pr _y SiO ₅ (1)
(In general formula (1), x represents a number of 1 or more and less than 2, y represents a number of more than 0 and 0.1 or less, and x and y satisfy the condition represented by 2- (x + y)> 0. Fulfill.)   2. The scintillator single crystal according to claim 1, wherein in an excitation fluorescence spectrum measured at a temperature of 10 to 40 ° C., a fluorescence wavelength with respect to an excitation wavelength that gives a maximum value of fluorescence output is 300 nm or more.

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