JPH05212251A - Isotope separator - Google Patents

Abstract

PURPOSE:To provide the isotope separator which has a simple construction and can efficiently separate and refine specific isotope elements. CONSTITUTION:This separator has a light source 4 internally sealing only the specific isotope to be separated as a means for exciting a photoinduction chemical reaction and has further a reaction cell 7 and a hollow elliptic cylinder reflector 10. The light source 4 and the reaction cell 7 are respectively disposed in the positions corresponding to two pieces of focal lines of the hollow elliptic cylinder reflector 10. The reaction cell 7 has a heating means 8 for reactional products.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an isotope separation device for separating and purifying isotopes enclosed in an exposure light source of an exposure device.

[0002]

2. Description of the Related Art Conventionally, as a general technique for separating and purifying a specific isotope, there is a technique utilizing a gas diffusion method, a centrifugal separation method, a laser method or the like. It is used in a very special field like.

On the other hand, recently, it has been proposed to manufacture a semiconductor integrated circuit by using a mercury lamp filled with only a specific isotope element as an exposure device. However, such a mercury lamp filled with only a specific isotope is very expensive because the specific isotope itself is expensive, and it is difficult to mass-produce this type of mercury lamp. Met. Conventionally, as a device for concentrating only specific isotopes from mercury in a natural state containing multiple isotopes,
[Christopher R. Webster and Richard N. Zare, J. Phys. C
hem., 1981, 85, 1302-1305]. This device is a lamp light source in which a sample containing a plurality of isotopes is filled with an element containing a specific isotope at a concentration higher than the abundance ratio in the natural state, and a wavelength of a wavelength caused by the specific isotope. It has a configuration in combination with an optical filter that transmits only light. According to this configuration, only the light having the wavelength that has passed through the optical filter is applied to the sample as the excitation light, and the photoinduced chemical reaction can be caused to the sample, thereby concentrating the specific isotope element. it can.

[0004] More specifically, by using this device, for example, in the case of concentrating isotopic ¹⁹⁶ Hg of mercury contained in a higher concentration than the abundance ratio of the natural state of the isotope ¹⁹⁶ Hg mercury A low pressure lamp containing mercury as a light emitting element and an optical filter made of mercury in a natural state are used in combination. Then, a mixed gas of mercury metal vapor and hydrogen halide is introduced into the reaction cell in advance, and the mixed gas is irradiated with the ultraviolet rays emitted from the low-pressure lamp described above through the optical filter. That is, among the ultraviolet rays emitted from the above-mentioned low-pressure lamp, ultraviolet rays having a wavelength derived from all the mercury isotopes other than ¹⁹⁶ Hg are absorbed by the optical filter to obtain the mercury isotope ¹⁹⁶ Hg.
That is, only the ultraviolet rays having a wavelength due to the above are irradiated to the above-mentioned mixed gas.

The photoinduced chemical reaction occurring in the above-mentioned reaction cell when the mixed gas is irradiated with the ultraviolet rays as described above is described by a chemical formula as follows. The symbol ¹ So represents the ground state of the mercury atom, and the symbol ³ P
₁ represents an excited state of a mercury atom that emits a photon having a wavelength of 253.7 nm.

¹⁹⁶ Hg ( ¹ So) + Photon (λ = 253.7 nm) → ¹⁹⁶ Hg ( ³ P ₁ ) (1) ¹⁹⁶ Hg ( ³ P ₁ ) + HCl → ¹⁹⁶ HgCl + H (2) ¹⁹⁶ HgCl + ¹⁹⁶ HgCl → ¹⁹⁶ Hg ₂ Cl ₂ (3) Of these, 253.7 represented by the above chemical formula (1)
A photon (Photon) having a wavelength (λ) of nm is an isotope in the hyperfine structure of the 253.7 nm emission line of mercury.
It is a photon contained in light of a wavelength emitted only from the ¹⁹⁶ Hg element. The hydrogen atom [H] represented by the chemical formula (2) does not cause an unnecessary chemical reaction because it reacts with butadiene to form a polymer.

As a result of the photoinduced chemical reactions represented by the above chemical formulas (1), (2) and (3), a chloride of a mercury isotope [ ¹⁹⁶ Hg ₂ Cl ₂ ] [see the above chemical formula (3)] Since the generated mercury isotope chloride adheres or deposits on the tube wall of the reaction cell as a white fine powder, the adhered or deposited product is subsequently taken out to collect isotope elements.

As a method of taking out the attached or deposited product, the irradiation of the excitation light is stopped, the reaction cell is removed, and the removed reaction cell is heated by using a separate system. The product is sublimated and collected, or the irradiation of the excitation light is stopped, the reaction cell is still attached, and the product is heated by using some other means.
It was sublimated and collected.

[0009]

The apparatus utilizing the gas diffusion method or the like used in the uranium enrichment described above requires large-scale equipment and expensive equipment. Since a device utilizing a chemical reaction is simple and economical, it is very useful for the isotope separation of elements such as mercury.

However, in the conventional apparatus utilizing this photoinduced chemical reaction, as described above, a light emitting element containing an element containing a specific isotope to be enriched at a concentration higher than the abundance ratio in the natural state. The lamp light source enclosed as is used. Therefore, an optical filter that transmits only light having a wavelength caused by the specific isotope is required, and therefore light having a wavelength caused by a useful isotope is also considerably absorbed. Usage efficiency was poor.
In addition, the configuration of the entire device is inevitably complicated.

Further, since no means for heating the reaction product is provided in the apparatus, in order to collect the product attached or deposited in the reaction cell by the photochemical reaction, as described above, A method of stopping the irradiation of the excitation light and then removing the reaction cell and heating it using a separate system, or a method of heating the reaction cell with the reaction cell attached using some other means is adopted. Whichever method is used, there is a problem in that the efficiency of generation and collection of the photochemical reaction product is low, and therefore it is difficult to inexpensively separate and purify a specific isotope element.

Therefore, an object of the present invention is to provide an isotope separation device having a simple structure and which can be manufactured economically at low cost.

Another object of the present invention is to provide an isotope separation device which can separate and purify a specific isotope at a relatively low cost.

[0014]

According to one embodiment of the present invention, as an excitation means for inducing a photoinduced chemical reaction, an isotope having a light source in which only a specific isotope element to be separated is enclosed as a light emitting element. An element separation device is obtained.

According to another aspect of the present invention, as the excitation means for inducing a photoinduced chemical reaction, a specific isotope element to be separated from a plurality of isotope elements contained in a sample irradiated with excitation light is used. An isotope separation device having a light source in which all isotopes other than isotopes are enclosed as luminescent elements can be obtained.

Further, in the isotope separation device of the present invention, in addition to the above-mentioned light source, a hollow elliptic cylindrical reflection having a reaction cell for causing the photoinduced chemical reaction and an inner surface for reflecting the excitation light from the excitation means. A body may be provided, and the excitation means and the reaction cell may be arranged at positions corresponding to two focal lines of the hollow elliptic cylinder reflector.
In addition, the reaction cell may have a structure in which a heating unit for heating a product generated in the cell by the photoinduced chemical reaction is integrated.

[0017]

[Function] As a light source in which only the specific isotope to be separated is encapsulated as a light emitting element is used as a means for exciting the photoinduced chemical reaction, light having a wavelength caused by another isotope is blocked or attenuated. Therefore, the optical filter described above is unnecessary.

Further, as means for exciting the photoinduced chemical reaction,
When using a light source in which all isotopes other than the specific isotope to be separated among the plurality of isotopes are enclosed as luminescent elements, the photoinduced chemistry of the plurality of isotopes contained in the sample is used. By recovering only the product that has not reacted, only the specific isotope can be separated. Therefore, also in this case, the optical filter becomes unnecessary.

Further, since the excitation means and the reaction cell are respectively arranged at positions corresponding to two focal lines of the hollow elliptic cylinder reflector having an inner surface for reflecting the excitation light from the excitation means, Excitation light from the means is efficiently collected in the reaction cell. Therefore, the utilization efficiency of the excitation light is improved, and the production efficiency of the photoinduced chemical reaction product is also improved.

Further, since the heating means for heating the product generated in the reaction cell by the photoinduced chemical reaction is provided, it is possible to simultaneously heat the reaction product while irradiating the reaction cell with the excitation light. it can. Therefore, since it becomes possible to proceed the photoinduced chemical reaction and the sublimation of the product at the same time,
The product collection efficiency is improved, and the isotope separation efficiency is also improved.

[0021]

EXAMPLE An isotope separation apparatus according to a first example of the present invention will be described with reference to FIG. This embodiment will be described as being used for separating a specific single isotope of mercury used as a light emitting element of a light source that emits deep ultraviolet rays in an exposure apparatus for manufacturing a semiconductor circuit.

Table 1 shows each isotope of mercury together with its natural abundance.

[0023]

[Table 1]

The isotope separated by using the isotope separation device of this embodiment will be described as ²⁰⁰ Hg.
The depicted apparatus can also be used to individually separate all other mercury isotopes.

The illustrated apparatus comprises an excitation part 1, a reaction part 2,
A storage container 3 for storing them is provided, and other components are shown by blocks.

First, the excitation unit 1 includes a low pressure mercury lamp 4 and
It has a flow tube 5 covering the low pressure mercury lamp 4. The low-pressure mercury lamp 4 is made of quartz glass in a tubular shape with an outer diameter of 6 mm and a length of 20 cm.
Inside, about 5 mg of mercury isotope ²⁰⁰ Hg (very expensive but available in France or USA) is enclosed with 3 torr of argon gas.
The low-pressure mercury lamp 4 is excited by applying a voltage from the power supply 6. The flow tube 5 has a wavelength of 253,7.
It is made of glass that is transparent to the light of 185 nm but absorbs the light of 185 nm. Inside, there is a cooling nitrogen gas for keeping the low-pressure mercury lamp 4 at a constant temperature of 40 ° C. Flowing.

Next, the reaction section 2 comprises a reaction cell 7 and a coil-shaped heating wire 8. The reaction cell 7 is made of transparent quartz glass and has an outer diameter of 30 mm, an inner diameter of 20 mm and an effective length of 20 cm.
It is manufactured in a tubular shape. The heating wire 8 is the reaction cell 7 described above.
It is wound along the outer peripheral surface of the reaction cell 7, and the inside of the reaction cell 7 can be heated by supplying a current from the power source 9 to the heating wire 8 as necessary.

Next, the container 3 is a hollow elliptic cylinder reflector 1.
0. The hollow elliptic cylindrical reflector 10 accommodates an exciting part 1 and a reacting part 2.
The reaction section 2 and the reaction section 2 are arranged at two focal line positions. The inner surface of the hollow elliptic cylinder reflector 10 has a wavelength of 253,7.
Aluminum is vacuum-deposited in a mirror shape so as to efficiently reflect ultraviolet rays of nm. Although not shown, the storage container 3 is sealed or closed by using a normal sealing (closing) structure.

In the isotope separation device of this embodiment having the above structure, the above-mentioned reaction cell 7 further comprises
It forms part of an evacuation system. That is, two supply systems are prepared upstream of the reaction cell 7 via the mixing cell 11, and one supply system uses hydrogen chloride [HC
l] A gas supply source 12 is provided, and the other supply system is provided with a mercury metal vapor supply source 13. The mercury metal vapor supply source 13 includes a mercury reservoir 14 with a heater and a 1,3-butadiene [C ₄ H ₆ ] gas supply source 15. On the other hand, on the downstream side of the reaction cell 7, there is prepared a trap 16 for collecting chlorides generated as a result of the photo-induced chemical reaction, and on the further downstream side of this trap 16, a trap 17 for collecting unreacted mercury. Is prepared. The traps 16 and 17 are exhausted by a vacuum exhaust pump 18.

The photoinduced chemical reaction occurring inside the above-mentioned reaction cell 7 when the isotope separation apparatus of this embodiment is used is described by the chemical formula as follows.

²⁰⁰ Hg ( ¹ S ₀ ) + Photon (λ ′ = 253.7 nm) → ²⁰⁰ Hg ( ³ P ₁ ) (4) ²⁰⁰ Hg ( ³ P ₁ ) + HCl → ²⁰⁰ HgCl + H (5) ²⁰⁰ HgCl + ²⁰⁰ HgCl → ²⁰⁰ Hg ₂ Cl ₂ (6) Of these, 253.7 represented by the above chemical formula (4)
A photon (Photon) having a wavelength (λ ′) of nm is
It is a photon contained in light of a wavelength emitted from only the isotope ^20O Hg element in the hyperfine structure of the 253.7 nm emission line of mercury shown in FIG. 3, and the photon wavelength (λ) shown in the chemical formula (1) above And are slightly different in the 253.7 nm wavelength band. The hydrogen atom [H] represented by the above chemical formula (5) does not cause an unnecessary chemical reaction because it reacts with butadiene to form a polymer.

As a result of the photoinduced chemical reactions represented by the above chemical formulas (4), (5) and (6), a chloride of a mercury isotope [ ^20O Hg ₂ Cl ₂ ] [see the above chemical formula (6)] is obtained. The mercury isotope chloride produced [ ^20O Hg ₂ C
l ₂ ] adheres to or deposits on the tube wall of the reaction cell 7 as white fine powder.

As described above, the mercury isotope chloride [ ^20O Hg ₂ Cl ₂ ] thus produced in the reaction cell 7 is ^supplied to the heating wire 8 by applying a current from the power source 9 to
When heat of about 50 ° C. is applied, it is easily sublimated into a gas, flows out from the reaction cell 7 to the downstream side, is collected in the trap 16 described above, and is collected here as a solid. The recovered chloride [ ^20O Hg ₂ Cl ₂ ] is subsequently separated into chlorine and mercury by conventional chemical methods.
The mercury isotope ^20O Hg is contained in a high concentration in this mercury, and thus the mercury isotope ^20O Hg is thus ^obtained.
g can be separated from other isotopes.

The excited atom ^20O Hg (of the mercury isotope ^20O Hg generated in the process represented by the above chemical formula (4) is
A part of ³ P ₁ ) loses its excitation energy by collision with another isotope atom before the reaction represented by the above chemical formula (5) occurs, and excites the other isotope atom on the other side of the collision. As a result, chlorides derived from isotope atoms other than the isotope to be separated are produced.

This reaction is described by a chemical formula as follows. In addition, n represents a mercury isotope other than ^{20 O} Hg, and ^n'represents all the mercury isotopes.

²⁰⁰ Hg ( ³ P ₁ ) + nHg ( ¹ S ₀ ) → nHg ( ³ P ₁ ) (7) nHg ( ³ P ₁ ) + HCl → nHgCl + H (8) nHgCl + n′HgCl → nHgn′HgCl ₂ (9) or more As shown by the chemical formulas (7), (8) and (9) in the above, the mercury separated by the isotope separation device of this embodiment contains a slight amount of isotopes other than ²⁰⁰ Hg of isotopes of mercury. May be included. In this case, the recovered mercury may be further applied to the isotope separation device of this embodiment in order to purify it to a desired purity.

In this embodiment, the low-pressure mercury lamp 4 in which ²⁰⁰ Hg of a single isotope of mercury is enclosed as a light emitting element is used as the light source of the excitation part 1. However, a plurality of mercury contained in mercury in the sample is used. It is also possible to use a low-pressure mercury lamp in which all the isotope elements other than ²⁰⁰ Hg among the isotope elements are sealed. In this case, only the product that did not cause the photo-induced chemical reaction is collected in the trap 16, whereby only ²⁰⁰ Hg of the isotope of mercury can be separated and purified.

In this embodiment, the coil-shaped heating wire 8 is wound along the outer peripheral surface of the reaction cell 7,
A coil-shaped heating wire may be provided along the inner peripheral surface of the reaction cell 7. Further, it goes without saying that a coil-shaped heating wire having a smaller diameter may be provided inside the reaction cell 7.

Further, in this embodiment, the reaction section 2 is provided with the heating wire 8 as means for heating the product produced in the reaction cell 7, but the excitation section 1 is heated with the above-mentioned product. A heat ray light source for doing so may be provided integrally with the low-pressure mercury lamp 4.

With reference to FIG. 2, an isotope separation device according to a second embodiment of the present invention will be described.

In the isotope separation device of this embodiment, the storage container 3 has a single common focal line position and two individual focus line positions instead of the hollow elliptic cylinder reflector 10 in the first embodiment. Bi-elliptic cylinder reflector with focal line position 19
It is composed by. A reaction cell 7 similar to that in the first embodiment is arranged at a position corresponding to the common focal line of the bi-elliptic cylinder reflector 19, and a first embodiment is provided at a position corresponding to one focal line. A low pressure mercury lamp 4 similar to that in the example has an effective length of 20 at a position corresponding to the other focal line.
The cylindrical heat wire lamps 20 having a size of 10 cm are arranged. The heat ray lamp 20 is excited by applying a voltage from a power source 21. The bi-elliptical cylinder reflector 19 has a mirror shape in which aluminum is vacuum-deposited so that the inner surface of the ellipse cylinder on the side where the low-pressure mercury lamp 4 is arranged efficiently reflects ultraviolet rays having a wavelength of 253.7 nm. On the other hand, the inner surface of the elliptic cylinder on the side on which the heat ray lamp 20 is arranged has a mirror shape in which gold is vacuum-deposited so as to mainly reflect infrared rays efficiently. As described above, in the present embodiment, the low-pressure mercury lamp 4 is formed by using the bi-elliptical cylindrical reflection structure.
Since the ultraviolet rays emitted from and the infrared rays emitted from the heat ray lamp 20 can be simultaneously focused on the reaction cell 7, the reaction products can be produced and collected extremely efficiently.

As is clear from the above, in this embodiment, the low-pressure mercury lamp 4, the flow tube 5, and the heat ray lamp 20 constitute the excitation part.

The present embodiment is suitable for continuous operation while controlling the entire isotope separation system by a computer so as to keep it in an optimum state.

In the above-mentioned embodiments, chlorine is used as the element that bonds with mercury by the photoinduced chemical reaction.
Oxygen may be used instead of chlorine. In this case, the same isotope separation as in the above-mentioned examples can be realized through the reaction process represented by the following chemical formula.

2 ²⁰⁰ Hg ( ³ P ₁ ) + O ₂ → 2 ²⁰⁰ HgO (10)

[0046]

According to the present invention, since a light source encapsulating a luminescent element related to a specific isotope to be separated is used as a means for exciting a photo-induced chemical reaction, another optical filter is used. It is not necessary to block or transmit light due to isotopes.

Therefore, it is possible to obtain an isotope separation device which has a simple structure and can be manufactured at a lower cost.

Further, according to the present invention, since the exciting means for the photoinduced chemical reaction and the reaction cell are respectively arranged at the positions corresponding to the two focal lines of the hollow elliptic cylinder reflector, the exciting means emits light. As a result of improving the efficiency of collecting the excited light into the reaction cell, the efficiency of generating the photoinduced chemical reaction product is improved.
Therefore, the specific isotope can be separated and purified at a relatively low cost.

Further, according to the present invention, since the means for heating the product generated in the reaction cell by the photoinduced chemical reaction is provided, it is possible to simultaneously advance the photoinduced chemical reaction and the sublimation of the product. Therefore, the products can be efficiently collected and the isotope elements can be separated.

[Brief description of drawings]

FIG. 1 is a view showing an isotope separation device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an isotope separation device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an ultrafine structure of a 253.7 nm emission line of mercury.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Excitation part 2 Reaction part 4 Low-pressure mercury lamp 7 Reaction cell 8 Heating wire 10 Hollow elliptic cylinder reflector 19 Bi-elliptic cylinder reflector 20 Heat ray lamp

Claims (5)

[Claims] 1. An isotope element separation device comprising an excitation means for irradiating a sample containing a plurality of isotopes with excitation light, and separating a specific isotope element by a photoinduced chemical reaction induced by the excitation light. 2. The isotope separation device according to claim 1, wherein the excitation means has a light source in which only the specific isotope element is enclosed as a light emitting element. 2. An isotope element separation device comprising an excitation means for irradiating a sample containing a plurality of isotopes with excitation light, and separating a specific isotope element by a photoinduced chemical reaction induced by the excitation light. In the isotope separation device, the excitation means includes a light source in which all isotopes other than the specific isotope element among the plurality of isotope elements are enclosed as light emitting elements. .. 3. The isotope separation device according to claim 1 or 2, further comprising a reaction cell that causes the photoinduced chemical reaction, an inner surface that reflects the excitation light from the excitation means, and an inner surface of the inner surface. A hollow elliptic cylinder reflector having two focal lines, wherein the excitation means and the reaction cell are respectively arranged at positions corresponding to the two focal lines. apparatus. 4. The isotope separation device according to claim 3, wherein the reaction cell has a heating means for heating a product generated in the cell by the photoinduced chemical reaction. Characteristic isotope separation device. 5. The isotope separation apparatus according to claim 1 or 2, further comprising: an inner surface that reflects the excitation light from the excitation means, and a single common focal point position and two individual inside focal points. And a reaction cell placed at a position corresponding to the common focus line, and the excitation means is arranged at a position corresponding to one focus line. An isotope separation device, comprising: the light source; and a heat ray light source arranged at a position corresponding to the other focal line.