JP2019025415A - Multiple reflection cell and isotope concentrator - Google Patents

Abstract

To provide a multiple reflection cell and an isotope concentrator for preventing a generation gas generated by a photoreaction from being diluted by pyrolysis of a sample gas at a reflection surface of a concave surface mirror.SOLUTION: The multiple reflection cell has a container 3 receiving supply of a sample gas which is a target for an optical reaction, and concave surface mirrors 5 and 7 housed in the container 3 and facing, in which an optical reaction is conducted by injecting a laser light into the container 3 and reflecting the injected laser light between the concave surface mirrors 5 and 7 a plurality of times, and the multiple reflection cell has a gas suction nozzle 9 and an exhaust piping 11 for sucking gas around reflection surfaces 5a and 7a of the concave surface mirrors 5 and 7 and discharging the same outside from the container 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multi-reflection cell that performs a photoreaction by reflecting a laser beam a plurality of times between a plurality of concave mirrors arranged facing each other, and an isotope enrichment device that enriches an oxygen isotope by the photoreaction.

In recent years, a technique for causing a photoreaction by irradiating a gas in a container with laser light having a specific wavelength and inducing an optical transition between specific energy levels has been widely used. For example, Patent Document 1 discloses a technique for concentrating ¹⁸ O by irradiating ozone molecules ( ¹⁶ O ¹⁶ O ¹⁸ O) containing ¹⁸ O, which is an isotope of an oxygen atom, with laser light having a specific frequency (wavelength). It is disclosed.

In the technology that causes such a photoreaction, by increasing the “light utilization” indicating how much laser light is used in the photoreaction, the “energy yield” indicating the result with respect to the input energy is improved. As a typical method for increasing the “light utilization rate”, there is an increase in the length of the path where the laser beam and the gas to be reacted are in contact with each other.
As a method of lengthening the optical path, it is possible to simply extend the length of the container in which the reaction is performed along a straight line along the irradiation direction of the laser beam. In this case, the size of the container, the installation space, etc. There is a limit from the viewpoint. Therefore, a method is generally used in which a plurality of concave mirrors are installed facing each other and laser light is reflected a plurality of times between the concave mirrors to achieve a long optical path. The laser light reflected between the concave mirrors a predetermined number of times is guided out of the container through the laser transmission window and detected by the detector.

Such a structure in which the concave mirror is arranged to reflect the laser light a plurality of times is generally called a multiple reflection cell (or multiple reflection container). Patent Document 2 discloses a sample cell in which a plurality of concave mirrors are arranged in a casing and a light beam is multiply reflected between the concave mirrors.
Usually, since a part of the incident laser light diffuses on the concave mirror surface (reflection surface), the reflection point of the laser light on the reflection surface of the concave mirror becomes a light spot and can be observed with a camera or the like. Therefore, in the multiple reflection cell, a plurality of light spots are observed on the reflection surface of the concave mirror, and these light spot groups are called spot patterns. By confirming such a spot pattern, the position and orientation of the concave mirror can be adjusted so that the laser beam is reflected a predetermined number of times between the concave mirrors.

Japanese Patent No. 4364529 JP-A-8-35926

In general, when laser light is reflected by a concave mirror, it is known that part of the energy of the laser light incident on the reflecting surface of the concave mirror is lost and not reflected. Part of this energy loss is absorbed by the concave mirror and converted into heat.
Add ozone gas as a photoreaction object to the multiple reflection cell (Note: It is common to add additive gases such as rare gases to ease the lower limit of ozone explosion, but for the sake of explanation, describe it as “ozone gas”) When concentrating oxygen isotopes ¹⁸ O by decomposing ozone molecules (eg, ¹⁶ O ¹⁶ O ¹⁸ O) by photoreaction using laser light supplied and multiple reflected between concave mirrors, the reflecting surface of the concave mirror When the laser beam incident on the laser beam is converted into heat, the ozone contacting the reflecting surface of the concave mirror is thermally decomposed by this heat.

However, the thermal decomposition of ozone is a non-isotope-selective reaction that occurs not only with ozone molecules containing ¹⁸ O, but also with other ozone molecules that do not contain ¹⁸ O. For this reason, the ¹⁸ O oxygen isotope does not concentrate by pyrolysis, and ¹⁶ O ¹⁶ O ¹⁶ O, which occupies about 99.8% of the ozone gas supplied into the container, is thermally decomposed to generate oxygen molecules ¹⁶ O ¹⁶ O. It generates a lot.
When a large amount of ¹⁶ O ¹⁶ O is generated by the thermal decomposition of ozone, oxygen molecules containing ¹⁸ O generated by the photoreaction (for example, ¹⁶ O ¹⁸ O) are diluted, preventing the enrichment of the oxygen isotope ¹⁸ O. It was a big cause.

  The present invention has been made to solve the above-described problems, and can prevent the gas generated by the photoreaction from being diluted by the thermal decomposition of the sample gas on the reflecting surface of the concave mirror. An object is to provide a multiple reflection cell and an isotope concentrator.

(1) A multiple reflection cell according to the present invention includes a container that receives a supply of a sample gas that is a target of a photoreaction, and a plurality of concave mirrors that are housed in the container and arranged to face each other. A laser beam is incident on the container, and the incident laser beam is reflected a plurality of times between the concave mirrors to perform a photoreaction, and a gas in the vicinity of the reflective surface of the concave mirror is sucked to absorb the outside of the container. It is characterized by having suction / exhaust means for exhausting the air.

(2) In the above (1), the suction / exhaust means has a gas suction nozzle, and the gas suction nozzle is provided such that its direction can be changed. .

(3) In the above-described (1) or (2), the sample gas is separated and recovered from the gas exhausted by the suction / exhaust means, and the recovered sample gas is The container is supplied again to the container.

(4) An isotope enrichment apparatus according to the present invention is supplied with a multiple reflection cell according to the above (1) or (2) and a source gas mainly composed of ozone, and oxygen contained in the source gas An ozone purification means for purifying ozone gas by removing gas, supplying the purified ozone gas to the container as a sample gas and concentrating oxygen isotopes by a photoreaction, and exhausting by the suction exhaust means The gas is returned to the ozone purification means.

  In the present invention, the apparatus has a container that receives supply of a sample gas to be subjected to photoreaction, and a plurality of concave mirrors that are housed in the container and arranged to face each other, and laser light is incident on the container. A suction exhaust unit for performing a photoreaction by reflecting the incident laser beam a plurality of times between the concave mirrors and sucking a gas in the vicinity of the reflective surface of the concave mirror and exhausting the gas outside the container The product produced by the photoreaction can be suppressed from being diluted by the diluent generated by the thermal decomposition of the sample gas on the reflecting surface of the concave mirror.

It is a figure explaining the multiple reflection cell which concerns on this Embodiment 1. FIG. In the multiple reflection cell which concerns on this Embodiment 1, it is a figure explaining the installation position of a gas suction nozzle. It is a figure explaining the isotope enrichment apparatus which concerns on this Embodiment 2. FIG. It is a figure which shows an example of the specific structure of the isotope concentration apparatus which concerns on this Embodiment 2. FIG.

[Embodiment 1]
As shown in FIG. 1, a multiple reflection cell 1 according to Embodiment 1 of the present invention includes a container 3 that receives supply of a sample gas that is a target of a photoreaction, and a container 3 that is accommodated inside and opposed to the container 3. Two concave mirrors 5 and 7 are provided, a laser beam is incident into the container 3, and the incident laser beam is reflected between the concave mirrors 5 and 7 a plurality of times to cause a photoreaction. In addition, a gas suction nozzle 9 and an exhaust pipe 11 are provided as suction / exhaust means for sucking gas in the vicinity of the reflective surface 5a of the concave mirror 5 and the reflective surface 7a of the concave mirror 7 and exhausting the gas out of the container 3. .

  Hereinafter, each configuration of the multiple reflection cell 1 will be described in detail. In addition, in the drawings used in the following description, in order to make the characteristics easy to understand, there are cases where the characteristic portions are enlarged for convenience, but the dimensional ratios of the respective components are the same as the actual ones. Is not limited.

<Container>
The container 3 is cylindrical and accommodates concave mirrors 5 and 7 inside. The container 3 is provided with a laser transmission window 15 through which laser light emitted from the laser light source 13 passes and a guide mirror 17 that reflects the laser light irradiated through the laser transmission window 15 toward the concave mirror 7.

  The laser beam reflected a predetermined number of times in the container 3 is incident on the guide mirror 17 again and reflected, and then exits the container 3 through the laser transmission window 15. In the multiple reflection cell 1 shown in FIG. 1, a detector 19 for detecting the laser light emitted from the container 3 is installed.

  Furthermore, the gas introduction pipe 21 and the gas outlet pipe 23 are connected to the container 3, respectively, and the sample gas used for the photoreaction is introduced into the container 3 through the gas introduction pipe 21, and the sample gas after the photoreaction is performed. Is led out of the container 3 through the gas lead-out pipe 23.

In Embodiment 1, a SUS304 steel pipe having an outer diameter of 300 mm, a thickness of 4 mm, and a length of 1000 mm is used for the container 3, but the size and material of the container 3 are not limited to this, Can be arbitrarily selected.
The laser transmission window 15 is made of Kovar having a diameter of 34 mm and a thickness of 2 mm, and the guide mirror 17 is made of synthetic quartz having a diameter of 5 mm and a reflection angle of 45 degrees. The size and material are not limited to these, and can be arbitrarily selected.

<Concave mirror>
The concave mirrors 5 and 7 have concave reflecting surfaces 5a and 7a, respectively, and reflect the incident laser light a plurality of times at the reflecting surfaces 5a and 7a, so that the concave mirror 5 and the concave mirror 7 face each other. Is provided.

  In Embodiment 1, the concave mirrors 5 and 7 are made of synthetic quartz having a diameter of 200 mm and a thickness of 23 mm, and the distance between the concave mirrors between the concave mirror 5 and the concave mirror 7 is 760 mm. The reflectivity of the concave mirrors 5 and 7 is 99%.

  The concave mirrors 5 and 7 are not limited to spherical mirrors, but are not limited in shape as long as they constitute multiple reflections, and may be cylindrical mirrors, flat mirrors, or the like. Further, the diameter and thickness of the concave mirrors 5 and 7 and the distance between the concave mirrors are not limited to the above, and an arbitrary shape (diameter, thickness, etc.) and distance can be selected.

<Mirror fixing member>
The mirror fixing member 25 holds the back surfaces of the concave mirrors 5 and 7 and fixes them to the container 3. The concave mirrors 5 and 7 are installed inside the container 3 with the position (distance between the concave mirrors) and the direction (tilting direction, swinging direction) fixed by the mirror fixing member 25.
As shown in FIG. 1, the mirror fixing member 25 is preferably connected to a mirror adjusting mechanism 27 that strictly adjusts the positions and orientations of the concave mirrors 5 and 7. In this case, the position (direction between mirrors, vertical direction) and direction (tilting direction and swinging direction) of the concave mirrors 5 and 7 are adjusted by the mirror adjusting mechanism 27.

<Gas suction nozzle>
The gas suction nozzle 9 sucks the gas in the vicinity of the reflection surfaces 5a and 7a of the concave mirrors 5 and 7, and is installed on the reflection surfaces 5a and 7a side of the concave mirrors 5 and 7, as shown in FIG. An exhaust pipe 11 is connected.
Here, the gas in the vicinity of the reflective surfaces 5a and 7a refers to the sample gas supplied to the container 3, the generated gas generated by the photoreaction of the sample gas, and the sample gas contacting the reflective surfaces 5a and 7a. It mainly contains pyrolysis gas pyrolyzed by pyrolysis reaction.

  It is desirable to install the gas suction nozzle 9 so that the direction of the gas suction nozzle 9 can be changed appropriately so that the gas in the vicinity of the reflecting surfaces 5a and 7a can be efficiently sucked.

FIG. 2 shows an example in which the gas suction nozzle 9 is installed in the vicinity of the reflecting surface 5a. In FIG. 2, the gas suction nozzle 9 is arranged in four directions, up, down, left and right of the reflecting surface 5 a, and the suction port of the gas suction nozzle 9 is directed in the central axis direction of the concave mirror 5.
As illustrated in FIG. 2, when a plurality of gas suction nozzles 9 are installed, the gas suction amount in the vicinity of the reflection surface 5a is point-symmetric with respect to the center of the reflection surface 5a so as not to be shifted. It is desirable that a gas suction nozzle 9 be installed in the front. However, this is not the case when the gas suction amount can be individually adjusted for each gas suction nozzle 9.

<Exhaust piping>
The exhaust pipe 11 exhausts the gas near the reflecting surfaces 5 a and 7 a sucked by the gas suction nozzle 9 to the outside of the container 3.
In Embodiment 1, a stainless steel pipe made of SUS304 is used as the exhaust pipe 11, but the material is not limited to this, and any material that does not react with the sample gas or the product gas generated by the photoreaction is used. Any material can be selected. Further, an adjustment valve (not shown) for controlling the flow rate of the exhaust gas may be provided in the middle of the exhaust pipe 11.

Next, with respect to the laser light reaction method using the multiple reflection cell according to the present invention, as an example, the multiple reflection cell 1 shown in FIG. 1 is used, and oxygen isotope ¹⁸ O is concentrated by photoreaction using ozone as a source gas. This will be described below.

First, the laser light source 13 is installed outside the container 3. In the first embodiment, a semiconductor laser is used as the laser light source 13. Here, the intensity of the laser beam was set to 0.3 W, and the wavelength of the laser beam was set to 992 nm which decomposes only ¹⁶ O ¹⁶ O ¹⁸ O which is an isotope component in ozone.

Next, the mirror fixing member 25 to which the mirror adjusting mechanism 27 is connected is fixed in the container 3 so that the reflecting surface 5a of the concave mirror 5 and the reflecting surface 7a of the concave mirror 7 face each other.
Then, the position and orientation of the concave mirrors 5 and 7 are strictly adjusted by the mirror adjusting mechanism 27. Here, the distance between the concave mirrors is set to 760 mm, and the number of reflections of the laser light between the concave mirrors 5 and 7 at this time is about 160 times.

  Then, laser light is emitted from the laser light source 13 and introduced into the container 3 through the laser transmission window 15. The laser light introduced into the container 3 is reflected by the guide mirror 17 to the concave mirror 7 side. The laser light reflected between the concave mirrors 5 and 7 a predetermined number of times (= about 160 times) is incident on the guide mirror 17 again and reflected toward the laser transmission window 15, and passes through the laser transmission window 15 and outside the container 3. Exit to.

  The number of reflections of the laser light between the concave mirrors 5 and 7 can be measured by photographing the spot pattern of the laser light irradiated on the reflection surface 7a of the concave mirror 7 with a camera or the like (not shown).

  After confirming that the positions and orientations of the concave mirrors 5 and 7 are adjusted by the photographed spot pattern, the emission of the laser light from the laser light source 13 is stopped. Then, after the inside of the container 3 is evacuated by a vacuum pump (not shown) through the gas outlet pipe 23, ozone, which is a raw material gas for photoreaction, is introduced into the container 3 from the gas introduction pipe 21.

  At the same time, the gas in the vicinity of the reflecting surfaces 5 a and 7 a is sucked from the gas suction nozzle 9 and exhausted through the exhaust pipe 11. Here, gas suction nozzles 9 having a suction port shape of □ 3 × 200 mm were installed above and below the concave mirrors 5 and 7, respectively, so that the gas in the vicinity of the reflection surfaces 5a and 7a could be exhausted uniformly.

  Finally, laser light is emitted from the laser light source 13, and the laser light is introduced into the container 3 through the laser transmission window 15, whereby ozone photoreaction is performed.

At this time, the gas in the vicinity of the reflective surface 5a of the concave mirror 5 and the reflective surface 7a of the concave mirror 7 is exhausted out of the container 3 by the gas suction nozzle 9 and the exhaust pipe 11, so that the ozone on the surfaces of the reflective surfaces 5a and 7a. It is possible to prevent oxygen molecules that are pyrolysis gas generated by thermal decomposition of oxygen from diluting the oxygen isotope ¹⁸ O that is the product gas generated by the photoreaction, and to increase the enrichment of the oxygen isotope ¹⁸ O.

Here, the enrichment of the oxygen isotope ¹⁸ O can be estimated as follows.
It is known that the enrichment of ¹⁸ O follows the following reaction mechanism when laser molecules of a specific frequency are irradiated to ozone molecules containing ¹⁸ O, which is an isotope of oxygen atom ( ¹⁶ O ¹⁶ O ¹⁸ O). (See Patent Document 2).

First, when ozone light O ₃ containing ¹⁸ O (for example, ¹⁶ O ¹⁶ O ¹⁸ O) is irradiated with laser light, it is dissociated into one oxygen molecule and one oxygen atom as shown in Equation (1). .
O ₃ + “Laser irradiation” → O ₂ + O (1)
Since the oxygen atom O generated by the reaction of the formula (1) has gained energy, as shown in the formula (2), some of the ozone molecules O ₃ existing around are decomposed.
O + nO ₃ → 0.5 (1 + 3n) O ₂ (2)

In equation (2), n is called the entrainment factor. If n = 5, if one ozone molecule is decomposed by laser light irradiation, five ozone molecules are decomposed according to equation (2), so that equations (1) and (2) The reaction decomposes a total of 6 ozone molecules (almost all of ¹⁶ O ¹⁶ O ¹⁶ O because the natural abundance of ¹⁸ O is about 0.2%), producing 9 oxygen molecules O ₂ .
At this time, the concentration of ¹⁸ O contained in the generated nine oxygen molecules is about 5.6%, which corresponds to a concentration effect of about 28 times compared with the natural abundance ratio of ¹⁸ O (= about 0.2%).

Next, the amount of ozone molecules decomposed by the laser beam is estimated.
In the concentration of oxygen isotope ¹⁸ O using the multiple reflection cell 1 according to the embodiment of the present invention, the ozone pressure in the container 3 is −60 kPaG, the temperature is −60 ° C., the laser beam energy is 0.3 W, the wavelength When the natural abundance ratio of 992 nm and ¹⁸ O is 0.2%, and the amount of ozone molecules decomposed by laser light is calculated from these conditions, it is 8.48 × 10 ⁻⁹ [mol / sec]. Here, the distance between the concave mirrors is 760 mm.

When the entrainment coefficient in the formula (2) is n = 5, the production amount of the oxygen molecule O ₂ is
8.48 × 10 ^-9 × 9 ＝ 7.63 × 10 ^-8 [mol / sec] (3)
It becomes.

On the other hand, as a comparison object, the enrichment effect of oxygen isotope ¹⁸ O by a conventional multiple reflection cell that does not exhaust the gas near the reflection surface of the concave mirror was calculated.
When the reflectivity of the concave mirror is 99%, the laser light of 0.3 W in the first reflection,
0.3 × 0.99 = 0.297 [W] (4)
Is reflected,
0.3−0.297 = 0.003 [W] (5)
However, it is a loss at the concave mirror.
Therefore, the total loss when 160 reflections occur between the concave mirrors is
0.3 × (1-0.99 ¹⁶⁰ ) = 0.24 [W] (6)
It becomes. About 25% of the total loss is converted into heat at the reflecting surface of the concave mirror.
Since the energy required to decompose ozone molecules by heat is 101 kJ / mol, the amount of ozone thermally decomposed on the reflecting surface of the concave mirror is
0.24 x 0.25 / (101 x 10 ³ ) = 5.94 x 10 ^-7 [mol / sec] (7)
It becomes.

Furthermore, when the amount of oxygen molecule O ₂ produced by thermal decomposition of ozone is determined, in the thermal decomposition reaction, 1.5 oxygen molecules are produced from one ozone molecule,
5.97 × 10 ⁻⁷ × 1.5 = 8.96 × 10 ⁻⁷ [mol / sec] (8)
It becomes.

Therefore, the ¹⁸ O concentration in the case of using the conventional multiple reflection cell is
(0.002 × 8.96 × 10 ⁻⁷ + 0.056 × 7.63 × 10 ⁻⁸ ) / (8.96 × 10 ⁻⁷ + 7.63 × 10 ⁻⁸ ) = 0.0062 = 0.62% (9)
It becomes.

This is a concentration effect that is about three times that of the natural abundance of ¹⁸ O, which is about 0.2%.
That is, when ozone is photoreacted using the multiple reflection cell 1 according to the first embodiment to concentrate the oxygen isotope ¹⁸ O, the gas in the vicinity of the reflection surfaces 5a and 7a of the concave mirrors 5 and 7 is exhausted and heated. By preventing dilution by oxygen molecules generated by the decomposition reaction, it is suggested that 5.6% / 0.62% = about 9 times the concentration of ¹⁸ O can be obtained compared to the case of using a conventional multiple reflection container. The

  Note that the multiple reflection cell according to the present invention uses a gas in the vicinity of the reflection surface to prevent the isotope-enriched oxygen gas generated by the photoreaction from being diluted by the oxygen gas generated by thermal decomposition on the reflection surface. Inhaled and exhausted, but in order to exhaust 90% or more of the isotope-diluted oxygen gas generated by thermal decomposition on the reflecting surface, the exhaust flow rate is 1/20 or more of the flow rate of ozone flowing into the container. If it is smaller than this, mixing of the isotope-diluted oxygen gas and the isotope-enriched oxygen gas proceeds.

Furthermore, the multiple reflection cell according to the present invention supplies the gas exhausted by the suction exhaust means to the separately provided separation and recovery means, and separates and collects the sample gas from the exhausted gas by the separation and recovery means. The recovered sample gas may be supplied again to the container.
Note that a distillation column can be used as the separation and recovery means.

  In the above description, the suction / exhaust means includes the gas suction nozzle 9 and the exhaust pipe 11. However, the suction / exhaust means may not include the gas suction nozzle 9, and in this case, The exhaust pipe 11 may be installed so that the end of the exhaust pipe 11 is positioned in the vicinity of the reflecting surfaces 5a and 7a of the concave mirrors 5 and 7, and gas may be sucked from the end of the exhaust pipe 11 to be exhausted.

[Embodiment 2]
Next, an isotope concentrator according to Embodiment 2 of the present invention will be described.
As shown in FIG. 3, the isotope concentrator 31 according to the second embodiment includes a multiple reflection cell 1 according to the first embodiment, and a source gas supply means 33 that supplies a source gas mainly composed of ozone. And an ozone purifying means 35 that receives the supply of the source gas from the source gas supply means 33 and removes impurities (oxygen gas, etc.) contained in the source gas to purify ozone, and uses the purified ozone as a sample gas in a container 3, the oxygen isotope ¹⁸ O is concentrated by photoreaction, and the gas in the vicinity of the reflecting surfaces 5 a and 7 a exhausted by the exhaust pipe 11 is returned to the ozone purification means 35 using the suction means 37. It is what I did. Furthermore, the isotope concentrator 31 includes a separation means 39 for separating the oxygen isotope ¹⁸ O concentrated in the multiple reflection cell 1.

As a specific overall configuration of the isotope enrichment device 31, an isotope enrichment device 41 shown in FIG. 4 can be exemplified.
The isotope concentrator 41 includes an ozonizer 43 as the source gas supply means 33 (FIG. 3), a first distillation column 45 as the ozone purification means 35 (FIG. 3), a heat exchanger 47 as the suction means 37 (FIG. 3), and A pump 49 and a second distillation column 51 are provided as separation means 39 (FIG. 3). Hereinafter, each component of the isotope enrichment apparatus 41 and the oxygen gas in which the oxygen isotope ¹⁸ O is enriched using ozone as a source gas (hereinafter referred to as “isotope enriched oxygen gas”) are manufactured using the isotope enrichment apparatus 41. The case will be described. However, since the multiple reflection cell 1 is the same as that of the first embodiment, the description thereof is omitted here.

  The ozonizer 43 is supplied with the raw material oxygen gas GO and generates ozone. The raw material oxygen gas GO supplied to the ozonizer 43 is converted into ozone and sent to the first distillation column 45.

  The first distillation column 45 separates the ozone generated in the ozonizer 43 and the oxygen gas remaining without being converted into ozone. The first distillation column 45 condenses the rising gas of the first distillation column 45 to obtain a reflux liquid. The raw material gas is distilled by the 1 condenser 53 and the first reboiler 55 for heating the liquid accumulated in the tower bottom to obtain the rising gas.

  By this distillation operation, oxygen gas, which is a low-boiling component, is concentrated on the top side of the first distillation column 45, and ozone, which is a high-boiling component, is concentrated on the bottom side of the first distillation column 45, and ozone is separated from the raw material gas and purified.

  The purified ozone is introduced as a sample gas into the multiple reflection cell 1 that performs a photoreaction. The oxygen gas separated to the tower top side is supplied to the ozonizer 43 by the compressor 57, and is converted into ozone again together with the raw material oxygen gas GO.

Ozone introduced into the multiple reflection cell 1 generates isotope-enriched oxygen gas by the reaction of the above-described formula (1) in the laser multiple reflection optical path formed between the concave mirrors 5 and 7.
On the other hand, on the surfaces of the reflecting surfaces 5a and 7a of the concave mirrors 5 and 7, oxygen gas is generated non-isotopically (hereinafter referred to as “isotope-diluted oxygen gas”) by the thermal decomposition of ozone, before and after the thermal decomposition reaction. There is no change in oxygen isotope concentration. Therefore, when the isotope-diluted oxygen gas is mixed with the isotope-enriched oxygen gas generated by the photoreaction, the isotope-enriched oxygen gas is diluted and the ¹⁸ O concentration is lowered.

  In order to prevent this, the gas suction nozzle 9 sucks the gas in the vicinity of the reflecting surfaces 5 a and 7 a and exhausts it through the exhaust pipe 11. The exhaust flow rate is adjusted by the valve 61 while checking the indicated value of the flow meter 59. In order to exhaust 90% or more of the isotope-diluted oxygen gas, the exhaust flow rate is desirably 1/20 or more of the flow rate of the sample gas (ozone) flowing into the container 3. When the exhaust flow rate is smaller than this, mixing of the isotope-diluted oxygen gas and the isotope-enriched oxygen gas proceeds.

  The gas in the vicinity of the reflective surfaces 5a and 7a sucked and exhausted by the gas suction nozzle 9 and the exhaust pipe 11 is drawn into the heat exchanger 47 using a low-temperature fluid such as liquid nitrogen as a refrigerant and condensed, and the condensate is The liquid is sent to the first distillation column 45 by the pump 49. Then, in the first distillation tower 45, ozone contained in the exhausted gas is separated on the tower bottom side, and oxygen gas contained in the gas is separated on the tower top side. The ozone separated to the tower bottom side is introduced into the multiple reflection cell 1 together with ozone purified from the raw material gas. On the other hand, the oxygen gas separated to the tower top side is sent to the ozonizer by the compressor 57 and is used again as the raw material oxygen gas GO.

Further, the isotope-enriched oxygen gas obtained by the photoreaction in the multiple reflection cell 1 is sent to the second distillation column 51.
In the second distillation column 51, residual ozone Oz is separated to the bottom of the column by a distillation operation by the second condenser 63 for obtaining the reflux liquid and the second reboiler 65 for obtaining the rising gas, and isotope enrichment is performed. Oxygen gas is separated to the tower top side to obtain product oxygen gas.

  As described above, according to the isotope enrichment apparatus 41 according to the second embodiment, the isotope-enriched oxygen gas is diluted in the multiple reflection cell 1 by exhausting the isotope-diluted oxygen gas. Can be taken out as a product. Furthermore, ozone contained in the exhausted gas can be recovered and reused.

  In the above description, the exhausted gas is condensed and sent by a heat exchanger and a pump. However, the exhausted gas may be pressurized and sent by a compressor or the like. . However, it is necessary to note that ozone contained in the exhausted gas may be heated by being compressed and partially decomposed to form a chain reaction.

The first distillation column 45 and the second distillation column 51 are preferably packed columns using regular packing, but the ozone purification means and separation means of the isotope concentrator according to the present invention are not suitable. A packed tower or a plate tower using an ordered packing may be used.
Further, the first distillation column 45 and the second distillation column 51 are maintained under a low temperature condition capable of liquefying a gas containing ozone. However, the multiple reflection cell 1, the first distillation column 45, the multiple reflection cell 1, The piping connecting the two distillation columns 51 and the piping for extracting ozone gas from the bottom side of the first distillation column 45 are preferably cooled at a low temperature in order to suppress the self-decomposition of ozone. It is desirable to cool down.

DESCRIPTION OF SYMBOLS 1 Multiple reflection cell 3 Container 5, 7 Concave mirror 5a, 7a Reflection surface 9 Gas suction nozzle 11 Exhaust piping 13 Laser light source 15 Laser transmission window 17 Guide mirror 19 Detector 21 Gas introduction tube 23 Gas extraction tube 25 Mirror fixing member 27 Mirror Control mechanism 31 Isotope concentrator 33 Source gas supply means 35 Ozone purification means 37 Suction means 39 Separation means 41 Isotope concentrator 43 Ozonizer 45 First distillation column 47 Heat exchanger 49 Pump 51 Second distillation column 53 First condenser 55 First reboiler 57 Compressor 59 Flow meter 61 Valve 63 Second condenser 65 Second reboiler

Claims (4)

A container that receives supply of a sample gas to be subjected to a photoreaction, and a plurality of concave mirrors that are accommodated inside the container and arranged to face each other; a laser beam is incident on the container; A multi-reflection cell that performs photoreaction by reflecting laser light a plurality of times between the concave mirrors,
A multi-reflection cell comprising suction / exhaust means for sucking a gas in the vicinity of a reflection surface of the concave mirror and exhausting the gas out of the container.   2. The multiple reflection cell according to claim 1, wherein the suction / exhaust means has a gas suction nozzle, and the gas suction nozzle is provided so that its direction can be changed. Separating and collecting means for separating and collecting the sample gas from the gas exhausted by the suction exhaust means;
3. The multiple reflection cell according to claim 1, wherein the collected sample gas is supplied again to the container. A multi-reflection cell according to claim 1 or 2, and an ozone purification means for purifying ozone gas by receiving supply of source gas mainly composed of ozone and removing oxygen gas contained in the source gas, An isotope concentrator for concentrating oxygen isotopes by photoreaction by supplying purified ozone gas to the vessel as a sample gas,
The isotope concentrating apparatus, wherein the gas exhausted by the suction exhaust means is returned to the ozone purification means.

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