JP6869846B2 - Multiple reflection cell and isotope concentrator - Google Patents

Description

The present invention relates to a multiple reflection cell that reflects a laser beam a plurality of times between a plurality of concave mirrors arranged facing each other to perform a photoreaction, and an isotope concentrator that concentrates an oxygen isotope by a photoreaction.

In recent years, a technique of irradiating a gas in a container with a laser beam of a specific wavelength to induce an optical transition between specific energy levels to induce a photoreaction has been widely used. For example, Patent Document 1 describes a technique for irradiating an ozone molecule ( ¹⁶ O ¹⁶ O ^{18 O) containing 18} O, which is an isotope of an oxygen atom, with a laser beam of a specific frequency (wavelength) ^{to concentrate 18 O.} It is disclosed.

In the technique of causing such a photoreaction, by increasing the "light utilization rate" indicating how much the laser beam is used in the photoreaction, the "energy yield" indicating the result with respect to the input energy is improved. A typical method for increasing the "light utilization rate" is to lengthen the path in which the laser beam and the gas to be reacted are in contact with each other.
As a method of lengthening the optical path, the length of the container in which the reaction is carried out is simply extended in 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 in which a plurality of concave mirrors are installed facing each other and the laser beam is reflected a plurality of times between the concave mirrors to achieve a long optical path is generally used. Then, the laser beam reflected between the concave mirrors a predetermined number of times is guided to the outside 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 beam a plurality of times is generally called a multiple reflection cell (or multiple reflection container) or the like. Patent Document 2 discloses a sample cell in which a plurality of concave mirrors are arranged in a housing and multiple reflections of a light beam are performed between the concave mirrors.
Normally, a part of the incident laser light is diffused on the concave mirror surface (reflection surface), so that the reflection point of the laser light on the reflection surface of the concave mirror becomes a light point and can be observed by 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. Then, by confirming such a spot pattern, the position and orientation of the concave mirror can be adjusted so that the laser beam is reflected between the concave mirrors a predetermined number of times.

Japanese Patent No. 4364529 Japanese Unexamined Patent Publication No. 8-35926

Generally, when the laser beam is reflected by the concave mirror, it is known that a part of the energy of the laser beam incident on the reflecting surface of the concave mirror is not reflected as a loss. Part of this energy loss is absorbed by the concave mirror and converted into heat.
Ozone gas (Note: It is common to add an additive gas such as a rare gas to alleviate the lower limit of ozone explosion, but it is described as "ozone gas" for explanation) as a photoreactive object in the multi-reflection cell. ^{When supplying and decomposing ozone molecules (eg 16} O ¹⁶ O ¹⁸ O) by photoreaction using laser light multiple reflected between concave mirrors ^{to concentrate oxygen isotope 18} O, the reflective surface of the concave mirror When the laser light incident on the surface is converted into heat, the ozone in contact with the reflecting surface of the concave mirror is thermally decomposed by this heat.

However, thermal decomposition of ozone is a non-isotope-selective reaction that occurs not only for ozone molecules containing ^{18 O, but also for other ozone molecules that do not contain 18 O. Therefore, the concentration of 18} O oxygen isotopes does not occur due to thermal decomposition, ^{and 16} O ¹⁶ O ¹⁶ O, which accounts for about 99.8% of the ozone gas supplied into the container, is thermally decomposed to produce oxygen molecules ¹⁶ O ¹⁶ O. It will be generated in large quantities.
^{When a large amount of 16} O ¹⁶ O is generated by thermal decomposition of ozone, ^{oxygen molecules containing 18} O generated by the photoreaction (for example, ¹⁶ O ¹⁸ O) are diluted, which hinders the concentration of ^{oxygen isotope 18 O.} It was a major cause.

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

(1) The multiple reflection cell according to the present invention has a container for receiving a sample gas to be subjected to a light reaction, and a plurality of concave mirrors housed inside the container and arranged to face each other. A laser beam is incident inside the container, and the incident laser beam is reflected between the concave mirrors a plurality of times to perform a photoreaction. The gas near the reflecting surface of the concave mirror is sucked in and the outside of the container. It is characterized by being provided with a suction / exhaust means for exhausting light.

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

(3) In the above-mentioned (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 used. It is characterized in that it is supplied to the container again.

(4) The isotope concentrator according to the present invention receives the supply of the multiple reflection cell according to (1) or (2) above and a raw material gas containing ozone as a main component, and oxygen contained in the raw material gas. An ozone purification means for removing gas to purify ozone gas is provided, and the purified ozone gas is supplied to the container as a sample gas to concentrate oxygen isotopes by a photoreaction, and is exhausted by the suction / exhaust means. The gas is returned to the ozone refining means.

In the present invention, a container that receives a sample gas to be subjected to a light reaction and a plurality of concave mirrors that are housed inside the container and arranged to face each other are provided, and laser light is incident into the container. Then, the incident laser light is reflected between the concave mirrors a plurality of times to perform a light reaction, and the gas in the vicinity of the reflecting surface of the concave mirror is sucked in and exhausted to the outside of the container. It is possible to prevent the product produced by the photoreaction 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 embodiment 1. It is a figure explaining the installation position of the gas suction nozzle in the multiple reflection cell which concerns on Embodiment 1. It is a figure explaining the isotope enrichment apparatus which concerns on this Embodiment 2. It is a figure which shows an example of the specific structure of the isotope concentrator which concerns on embodiment 2.

[Embodiment 1]
As shown in FIG. 1, the multiple reflection cell 1 according to the first embodiment of the present invention is housed inside the container 3 and is arranged so as to face each other with a container 3 that receives a sample gas to be subjected to a light reaction. It has two concave mirrors 5 and 7 provided, and a laser beam is incident in the container 3, and the incident laser beam is reflected a plurality of times between the concave mirrors 5 and 7 to perform a photoreaction. 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 to the outside of the container 3. ..

Hereinafter, each configuration of the multiple reflection cell 1 will be described in detail. In the drawings used in the following description, in order to make the features easier to understand, the featured parts may be enlarged for convenience, but the dimensional ratio of each component is the same as the actual one. Is not always.

<Container>
The container 3 has a tubular shape and houses the concave mirrors 5 and 7 inside. The container 3 is provided with a laser transmission window 15 through which the laser light emitted from the laser light source 13 is transmitted, and a guide mirror 17 for reflecting the laser light emitted 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, reflected, and then emitted to the outside of 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 beam emitted from the container 3 is installed.

Further, a gas introduction pipe 21 and a gas outlet pipe 23 are connected to the container 3, respectively, and the sample gas to be subjected to the photoreaction is introduced into the container 3 via the gas introduction pipe 21 and the sample gas after the photoreaction is performed. Is led out of the container 3 via the gas outlet pipe 23.

In the first embodiment, a steel pipe made of SUS304 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. It can be selected arbitrarily.
The laser transmission window 15 is made of Koval with a diameter of 34 mm and a thickness of 2 mm, and the guide mirror 17 is made of synthetic quartz with 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 in order to reflect the incident laser light on the reflecting surfaces 5a and 7a a plurality of times, the concave mirror 5 and the concave mirror 7 face each other. Is provided.

In the first embodiment, 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 5 and the concave mirror 7 is 760 mm. The reflectance of the concave mirrors 5 and 7 is 99%.

The concave mirrors 5 and 7 are not limited to spherical mirrors, and are not limited in shape as long as they are mirrors that form multiple reflections, and may be cylindrical mirrors, flat plate mirrors, or the like. Further, the diameters and thicknesses of the concave mirrors 5 and 7 and the distance between the concave mirrors are not limited to the above, and any shape (diameter, thickness, etc.) and distance can be selected.

<Mirror fixing member>
The mirror fixing member 25 holds the back side 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 in a state where the position (distance between the concave mirrors) and the direction (tilt direction, swing direction) are 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, respectively. In this case, the positions (inter-mirror direction, vertical direction) and orientation (tilt direction and swing 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 gas in the vicinity of the reflective surfaces 5a and 7a of the concave mirrors 5 and 7, and is installed on the reflective surfaces 5a and 7a of the concave mirrors 5 and 7 as shown in FIG. The exhaust pipe 11 is connected.
Here, the gases near the reflecting surfaces 5a and 7a are the sample gas supplied to the container 3, the generated gas generated by the photoreaction of the sample gas, and the sample gas in contact with the reflecting surfaces 5a and 7a. It mainly contains a pyrolyzed gas that has been thermally decomposed by a pyrolysis reaction.

It is desirable that the gas suction nozzle 9 is installed so that its orientation can be appropriately adjusted and changed 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 near the reflection surface 5a. In FIG. 2, the gas suction nozzles 9 are arranged in four directions of up, down, left, and right of the reflection surface 5a, and the suction ports of the gas suction nozzles 9 are directed in the direction of the central axis of the concave mirror 5.
As illustrated in FIG. 2, when a plurality of gas suction nozzles 9 are installed, they are point-symmetrical with respect to the center of the reflection surface 5a so that the amount of gas sucked in the vicinity of the reflection surface 5a is not biased. It is desirable that the gas suction nozzle 9 is installed in the. However, this does not apply if the gas suction amount can be adjusted individually for each gas suction nozzle 9.

<Exhaust piping>
The exhaust pipe 11 exhausts the gas in the vicinity of the reflective surfaces 5a and 7a sucked by the gas suction nozzle 9 to the outside of the container 3.
In the first embodiment, a stainless steel pipe made of SUS304 is used for 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 generated gas generated by the photoreaction may be used. For example, any material can be selected. Further, an adjusting valve (not shown) for controlling the flow rate of the exhaust gas may be provided in the middle of the exhaust pipe 11.

Next, regarding the laser light reaction method using the multiple reflection cell according to the present invention, as an example, the case where the ^{oxygen isotope 18} O is concentrated by a photoreaction using ozone as a raw material gas using the multiple reflection cell 1 shown in FIG. 1 is taken as an example. , 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 ^{the isotope component 16} O ¹⁶ O ^{18 O in ozone.}

Next, the mirror fixing member 25 to which the mirror adjusting mechanism 27 is connected fixes the reflective surface 5a of the concave mirror 5 and the reflective surface 7a of the concave mirror 7 in the container 3 so as to face each other.
Then, the positions and orientations 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 times the laser beam is reflected between the concave mirrors 5 and 7 at this time is about 160 times.

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

The number of times the laser beam is reflected between the concave mirrors 5 and 7 can be measured by photographing the spot pattern of the laser beam irradiated on the reflective 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 through the gas outlet pipe 23 by a vacuum pump (not shown), 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 5a and 7a 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 each of the concave mirrors 5 and 7, so that the gas in the vicinity of the reflective surfaces 5a and 7a could be uniformly exhausted.

Finally, the 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 to carry out a photoreaction of ozone.

At this time, the gas near the reflective surface 5a of the concave mirror 5 and the reflective surface 7a of the concave mirror 7 is exhausted to the outside of the container 3 by the gas suction nozzle 9 and the exhaust pipe 11, so that ozone on the surfaces of the reflective surfaces 5a and 7a It is possible to prevent the oxygen molecule, which is a thermally decomposed gas produced by the thermal decomposition of, ^{from diluting the oxygen isotope 18} O, which is a produced gas produced 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 concentration ^{of 18} O when an ozone molecule ( ¹⁶ O ¹⁶ O ^{18 O) containing 18} O, which is an isotope of an oxygen atom, is irradiated with a laser beam of a specific frequency follows the following reaction mechanism. (See Patent Document 2).

First, when an ozone molecule O ₃ ^{containing 18} O (for example, ¹⁶ O ¹⁶ O ¹⁸ O) is irradiated with laser light, it dissociates into one oxygen molecule and one oxygen atom as shown in equation (1). ..
O ₃ + "Laser light irradiation" → O ₂ + O ・ ・ ・ ・ ・ (1)
Since the oxygen atom O generated by the reaction of the formula (1) obtains energy, it decomposes some _{ozone molecules O 3 existing around it as shown in the formula (2).}
O + nO ₃ → 0.5 (1 + 3n) O ₂・ ・ ・ ・ ・ (2)

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

Next, the amount of ozone molecules decomposed by the laser beam is calculated.
^{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 light energy is 0.3 W, and the wavelength. Is 992 nm and ^{the natural abundance ratio of 18} O is 0.2%, and the amount of ozone molecule decomposition by laser light is calculated from these conditions to be 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 amount of _{oxygen molecule O 2 produced is}
8.48 × 10 ^-9 × 9 ＝ 7.63 × 10 ^-8 [mol / sec] ・ ・ ・ ・ ・ (3)
Will be.

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

_{Furthermore, when the amount of oxygen molecule O 2} produced by the thermal decomposition of ozone is determined, 1.5 oxygen molecules are produced from one ozone molecule in the thermal decomposition reaction.
5.97 × 10 ^-7 × 1.5 ＝ 8.96 × 10 ^-7 [mol / sec] ・ ・ ・ ・ ・ (8)
Will be.

^{Therefore, the 18} O concentration when using a conventional multiple reflection cell is
(0.002 x 8.96 x 10 ^-7 + 0.056 x 7.63 x 10 ^-8 ) / (8.96 x 10 ^-7 + 7.63 x 10 ^-8 ) = 0.0062 = 0.62% ・ ・ ・ (9)
Will be.

This is about three times the concentration effect compared to the natural abundance ratio of ^{18 O, which is about 0.2%.
That is, when the oxygen isotope 18} O is concentrated by photoreacting ozone with the multiple reflection cell 1 according to the first embodiment, the gas near the reflection surfaces 5a and 7a of the concave mirrors 5 and 7 is exhausted and heat is generated. It is suggested that by preventing dilution by oxygen molecules generated by the decomposition reaction, ^{a concentration effect of 18} O of 5.6% / 0.62% = about 9 times can be obtained as compared with the case of using a conventional multiple reflection vessel. To.

In the multiple reflection cell according to the present invention, in order to prevent the isotope concentrated oxygen gas generated by the photoreaction from being diluted by the oxygen gas generated by the thermal decomposition on the reflection surface, the gas near the reflection surface is used. Although it is sucked in and exhausted, in order to exhaust 90% or more of the isotope-diluted oxygen gas generated by thermal decomposition on the reflective 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, the mixture of the isotope-diluted oxygen gas and the isotope-concentrated oxygen gas will proceed.

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

Further, in the above description, the suction / exhaust means includes the gas suction nozzle 9 and the exhaust pipe 11, but the suction / exhaust means does not have to include the gas suction nozzle 9, and in this case, the gas suction nozzle 9 may not be provided. The end of the exhaust pipe 11 may be installed so as to be located near the reflective surfaces 5a and 7a of the concave mirrors 5 and 7, and gas may be sucked in and exhausted from the end of the exhaust pipe 11.

[Embodiment 2]
Next, the isotope concentrator according to the second embodiment of the present invention will be described.
As shown in FIG. 3, the isotope concentrator 31 according to the second embodiment includes the multiple reflection cell 1 according to the first embodiment and the raw material gas supply means 33 for supplying the raw material gas containing ozone as a main component. The ozone purification means 35 is provided for purifying ozone by receiving the supply of the raw material gas from the raw material gas supply means 33 and removing impurities (oxygen gas, etc.) contained in the raw material gas, and the purified ozone is used as a sample gas in a container. The gas is supplied to No. 3 ^{to concentrate the oxygen isotope 18} O by a photoreaction, and the gas in the vicinity of the reflecting surfaces 5a and 7a exhausted by the exhaust pipe 11 is returned to the ozone purification means 35 by using the suction means 37. It is something like that. Further, 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 concentrator 31, the isotope concentrator 41 shown in FIG. 4 can be exemplified.
The isotope concentrator 41 includes an ozonizer 43 as a raw material gas supply means 33 (FIG. 3), a first distillation column 45 as an ozone purification means 35 (FIG. 3), and a heat exchanger 47 as a suction means 37 (FIG. 3). It is provided with a pump 49 and a second distillation column 51 as a separation means 39 (FIG. 3). Hereinafter, each configuration of the isotope concentrator 41 and ^{an oxygen gas enriched with oxygen isotope 18} O using ozone as a raw material gas (hereinafter, referred to as “isotope enriched oxygen gas”) will be produced using the isotope concentrator 41. The case will be described. However, since the multiple reflection cell 1 is the same as that of the first embodiment described above, the description thereof will be omitted here.

The ozonizer 43 generates ozone by receiving the supply of the raw material oxygen gas GO, and 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 ozone generated by the ozonizer 43 from oxygen gas remaining without being converted to ozone, and is used to condense the rising gas of the first distillation column 45 to obtain a reflux liquid. The distillation operation of the raw material gas is performed by the 1 condenser 53 and the first reboiler 55 for heating the liquid accumulated at the bottom of the column to obtain an ascending gas.

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

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

The ozone introduced into the multiple reflection cell 1 produces isotope-concentrated oxygen gas by the reaction of the above 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 reflective surfaces 5a and 7a of the concave mirrors 5 and 7, oxygen gas (hereinafter referred to as "isotope-diluted oxygen gas") is non-isotopically selectively generated by the thermal decomposition of ozone, and before and after the thermal decomposition reaction. There is no change in the oxygen isotope concentration in. Therefore, when the isotope-diluted oxygen gas is mixed with the isotope-concentrated oxygen gas generated by the photoreaction, the isotope-concentrated oxygen gas is diluted and the ¹⁸ O concentration is lowered.

In order to prevent this, the gas suction nozzle 9 sucks in the gas in the vicinity of the reflecting surfaces 5a and 7a and exhausts the gas 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, it is desirable that the exhaust flow rate is 1/20 or more of the flow rate of the sample gas (ozone) flowing into the container 3. If the exhaust flow rate is smaller than this, the isotope-diluted oxygen gas and the isotope-concentrated oxygen gas are mixed.

The gas near 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 condensed liquid is condensed. The liquid is sent to the first distillation column 45 by the pump 49. Then, in the first distillation column 45, ozone contained in the exhausted gas is separated on the bottom side of the column, and oxygen gas contained in the gas is separated on the top side of the column. Then, the ozone separated on the bottom side of the tower is introduced into the multiple reflection cell 1 together with the ozone purified from the raw material gas. On the other hand, the oxygen gas separated on the top side of the tower is sent to the ozonizer by the compressor 57 and used again as the raw material oxygen gas GO.

Further, the isotope-concentrated 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 side of the column by a distillation operation by a second condenser 63 for obtaining a reflux liquid and a second reboiler 65 for obtaining an ascending gas, and isotope concentration. The oxygen gas is separated on the top side of the column to obtain the product oxygen gas.

As described above, according to the isotope concentrator 41 according to the second embodiment, the isotope-diluted oxygen gas is diluted by exhausting the isotope-diluted oxygen gas selectively generated in the multiple reflection cell 1. Can be taken out as a product by preventing. Further, ozone contained in the exhaust gas can be recovered and reused.

In the above description, the exhausted gas is condensed by a heat exchanger and a pump and sent, but the exhausted gas may be pressurized by a compressor or the like and sent. .. However, it should be noted that the ozone contained in the exhaust gas may be compressed, causing the temperature to rise and partially decomposing to form a chain reaction.

Further, although it is preferable to use a packed column using a packed bed for the first distillation column 45 and the second distillation column 51, it is not suitable as an ozone purification means and a separation means of the isotope concentrator according to the present invention. A packed column or a shelf column using a packed bed may be used.
Further, the first distillation column 45 and the second distillation column 51 are held under low temperature conditions in which a gas containing ozone can be liquefied, but the multiple reflection cell 1 and the first distillation column 45, and the multiple reflection cell 1 and the first. The piping connecting each of 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 self-decomposition of ozone, particularly at -50 ° C or lower. It is desirable to cool to.

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 pipe 23 Gas outlet pipe 25 Mirror fixing member 27 Mirror Regulation mechanism 31 Isotope concentrator 33 Raw material gas supply means 35 Ozone purification means 37 Suction means 39 Separation means 41 Isotope concentrator 43 Ozonizer 45 1st distillation tower 47 Heat exchanger 49 Pump 51 2nd distillation tower 53 1st condenser 55 1st reboiler 57 Compressor 59 Flowmeter 61 Valve 63 2nd condenser 65 2nd reboiler

Claims (4)

It has a container that receives the supply of the sample gas to be the target of the light reaction, and a plurality of concave mirrors that are housed inside the container and arranged so as to face each other. A multi-reflection cell that performs a light reaction by reflecting laser light between the concave mirrors a plurality of times.
A multi-reflection cell comprising a suction / exhaust means for sucking gas near the reflection surface of the concave mirror and exhausting the gas to the outside of the container. 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. It has a separation / recovery means for separating and recovering the sample gas from the gas exhausted by the suction / exhaust means.
The multiple reflection cell according to claim 1 or 2, wherein the recovered sample gas is supplied to the container again. The multi-reflection cell according to claim 1 or 2, and an ozone refining means for purifying ozone gas by removing the oxygen gas contained in the raw material gas by receiving the supply of the raw material gas containing ozone as a main component. An isotope concentrator that supplies purified ozone gas as a sample gas to the container and concentrates oxygen isotopes by a photoreaction.
An isotope concentrator, characterized in that the gas exhausted by the suction / exhaust means is returned to the ozone purification means.

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