JP2018028550A - Manufacturing method for gas cell, manufacturing method for magnetic measuring device, gas cell, and magnetic measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance uniformity of characteristics of gas cells.SOLUTION: A manufacturing method for a gas cell includes: a coating step of forming a coating layer on a surface of a plate material; an assembling step of assembling a plurality of the plate material having the coating layer formed thereon so as to form a cell surrounded by the surfaces having the coating layer formed thereon; and a filling step of filling the formed cell with alkali metal gas.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a gas cell manufacturing method and a gas cell.

  2. Description of the Related Art An optical pumping type magnetic sensor is used as a biomagnetism measuring device that detects a magnetic field emitted from a living heart or the like. Patent Document 1 discloses a magnetic sensor using a gas cell, pump light, and probe light. In this magnetic sensor, atoms encapsulated in the gas cell are excited by pump light to cause spin polarization. Since the polarization plane of the probe light transmitted through the gas cell rotates according to the magnetic field, the magnetic field is measured using the rotation angle of the polarization plane of the probe light.

  Patent Document 2, Patent Document 3, and Non-Patent Document 1 disclose techniques for filling a cell with gas.

JP 2009-236599 A JP-A-11-238469 US Pat. No. 7,666,485

Grbax Singh, Philip Diavore, and Carrol O. Alley, "A Technique for preparing Wall Coated Cesium Vapor Cells", The Review of Scientific Instruments, Vol. 43, No. 9, pp. 1388-1389 (1972)

When manufacturing a plurality of gas cells, if there are variations in the characteristics of the gas cells, this is reflected as variations in the sensitivity of the magnetic sensor.
The present invention provides a technique for improving the uniformity of gas cell characteristics.

The present invention provides a coating step of forming a coating layer on a first surface of a plate material, and a plurality of the plate materials on which the coating layer is formed to form a cell surrounded by the surface on which the coating layer is formed. Provided is a gas cell manufacturing method including an assembling step of assembling and a filling step of filling the formed cell with alkali metal atoms.
According to this manufacturing method, the uniformity of the thickness of the coating layer on the inner wall of the gas cell can be improved as compared with the case where the coating layer is formed after assembly.

In a preferred aspect, the plate has a second surface behind the first surface, and the coating layer is formed on the first surface and the second surface of the plate in the coating step, and the assembly step. In the method, a plurality of cells including a first cell surrounded by a plurality of surfaces including the first surface and a second cell surrounded by a plurality of surfaces including the second surface may be formed.
According to this manufacturing method, the uniformity of the thickness of the coating layer on the inner wall of the gas cell can be improved in a cell array having a plurality of cells.

In another preferred embodiment, the plurality of cells include a third cell in which an alkali metal solid is placed, and the plate material between the first cell and the second cell and the third cell is provided on the plate. A through hole is provided, and the filling step includes a vaporization step of vaporizing the alkali metal solid in the third cell to generate the alkali metal gas, and the generated alkali metal gas through the through hole. A diffusion step of diffusing from the third cell to the first cell and the second cell.
According to this manufacturing method, compared with the case where an alkali metal gas is individually sealed in each cell in a cell array having a plurality of cells, the concentration uniformity of the alkali metal gas can be improved.

In still another preferred embodiment, the plurality of cells include a fourth cell and a fifth cell, and a cell group including the first cell, the second cell, the fourth cell, and the fifth cell is: Two-dimensionally arranged on a plane, the third cell may be located on the plane.
According to this manufacturing method, it is possible to manufacture a gas cell in which the third cell is two-dimensionally arranged with respect to the cell group.

In still another preferred embodiment, the plurality of cells include a fourth cell and a fifth cell, and a cell group including the first cell, the second cell, the fourth cell, and the fifth cell is: The third cells may be arranged two-dimensionally on a plane, and the third cells may be stacked in a direction perpendicular to the plane with respect to the cell group.
According to this manufacturing method, it is possible to manufacture a gas cell in which the third cell is three-dimensionally arranged with respect to the cell group.

In still another preferred aspect, the manufacturing method includes a cutting step of cutting the plate material on which the coating layer is formed into a plurality of pieces, and the plurality of plate materials obtained by the cutting step are assembled in the assembly step. May be.
According to this manufacturing method, the number of plate materials to be handled in the coating process can be reduced, so that the handling of the plate material is simplified compared to the case where the coating step is performed after cutting.

The present invention also provides an outer wall that forms a closed space, an inner wall that partitions the closed space into a plurality of cells, a through-hole that is formed in the inner wall and connects at least one of the adjacent cells, and the cell A gas cell having an alkali metal atom enclosed therein is provided.
According to this gas cell, the uniformity of the characteristics of the gas cell can be improved in a cell array having a plurality of cells.

Furthermore, the present invention provides a gas cell having a wall surface that forms a closed space, and a first ampoule that is accommodated in the closed space and contains an alkali metal.
According to this gas cell manufacturing method, the gas cell can be manufactured stably regardless of the skill of the operator.

In a preferred embodiment, the gas cell may have a coating layer formed on the wall surface of the closed space, which suppresses relaxation of the spin-polarized state of the alkali metal atoms.
According to this gas cell, it can be stably manufactured regardless of the skill of the operator.

In another preferred embodiment, the closed space connects the first main chamber filled with the alkali metal atoms, the storage chamber for storing the first ampoule, and the first main chamber and the storage chamber. You may have a 1st hole.
According to this gas cell, even when the first ampoule is accommodated in the accommodation chamber, it can be stably manufactured regardless of the skill of the operator.

In still another preferred embodiment, the first ampoule may contain a buffer gas for suppressing the movement speed of the alkali metal atoms.
According to this gas cell, even when buffer gas is contained in the first ampule, it can be stably manufactured regardless of the skill of the operator.

In yet another preferred embodiment, the buffer gas may be a rare gas.
According to this gas cell, even when a rare gas is included in the first ampule, it can be stably manufactured regardless of the skill of the operator.

In still another preferred embodiment, the first ampoule may have a through hole for diffusing the buffer gas to the outside of the first ampoule.
According to this gas cell, the buffer gas can be diffused into the closed space.

In still another preferred embodiment, the closed space is filled with the alkali metal atoms, and a second main chamber different from the first main chamber is connected to the first main chamber and the second main chamber. You may have 2 holes.
According to this gas cell, a cell having a plurality of main rooms can be stably manufactured regardless of the skill of the operator.

In still another preferred embodiment, the first ampoule may have an absorber that absorbs light for forming the through hole.
According to this gas cell, even when the first ampoule is irradiated with light, it can be stably manufactured regardless of the skill of the operator.

In still another preferred embodiment, the gas cell may have a second ampoule containing a coating material for forming the coating layer.
According to this gas cell, even when the second ampoule is accommodated in the accommodation chamber, it can be stably manufactured regardless of the skill of the operator.

In still another preferred embodiment, the alkali metal may be solid or liquid.
According to this gas cell, even if the alkali metal accommodated in the first ampule is solid or liquid, it can be stably manufactured regardless of the skill of the operator.

Furthermore, the present invention provides a step of destroying the first ampule in a cell having a wall surface forming a closed space and a first ampule housed in the closed space and containing an alkali metal; and And a step of diffusing the alkali metal into the closed space after the destruction.
According to this gas cell manufacturing method, the gas cell can be manufactured stably regardless of the skill of the operator.

In a preferred aspect, the destruction of the first ampule may include a step of forming a through hole by irradiating the first ampule with light.
According to this method for producing a gas cell, the gas cell can be produced stably using light irradiation.

In another preferred embodiment, the light irradiation may be performed using a pulse laser that performs light irradiation with a pulse width of 1 microsecond or less.
According to this gas cell manufacturing method, a gas cell can be stably manufactured using a pulse laser.

In still another preferred embodiment, the destruction of the first ampule may include a step of cleaving the first ampule by irradiating the first ampule with light.
According to this method of manufacturing a gas cell, degassing is reduced as compared with the case of destruction by formation of a through hole using light irradiation.

In still another preferred embodiment, the light irradiation may be performed using a pulse laser that performs light irradiation with a pulse width of 1 nanosecond or less.
According to this gas cell manufacturing method, a gas cell can be stably manufactured using a pulse laser.

In still another preferred embodiment, the gas cell manufacturing method may include a step of forming a stress concentration portion in the first ampoule.
According to this gas cell manufacturing method, the gas cell can be manufactured more stably than in the case where no stress concentration portion is provided.

In still another preferred embodiment, the destruction of the first ampule may include a step of applying acceleration to the cell.
According to this gas cell manufacturing method, the gas cell can be stably manufactured by using the step of dynamically giving acceleration.

In still another preferred embodiment, the breaking of the first ampoule may include a step of applying heat that generates thermal stress to the first ampoule.
According to this method for producing a gas cell, the gas cell can be produced stably using the step of applying heat.

1 is a block diagram illustrating a configuration of a magnetic measurement device 1. FIG. 1 is an external view of a gas cell array 10. FIG. FIG. 3 is a sectional view of the gas cell array 10 taken along the line III-III. FIG. 4 is a cross-sectional view of the gas cell array 10 taken along the line IV-IV. 5 is a flowchart showing manufacturing steps of the gas cell array 10. The figure which shows the cut | disconnected board | plate material. The schematic diagram which shows the gas cell array 10 in which the ampule was accommodated. The schematic diagram which shows the gas cell array 10 by which alkali metal gas was diffused. The figure which shows the structure of a comparative example. The external view of the gas cell array 15 which concerns on the modification 1. FIG. XI-XI sectional drawing of the gas cell array 15. FIG. The schematic diagram which shows arrangement | positioning of the through-hole which concerns on the modification 2. FIG. The schematic diagram which shows arrangement | positioning of the through-hole which concerns on the modification 3. FIG. 10 is a flowchart showing a manufacturing process of a gas cell array according to Modification 8. 10 is a flowchart showing a manufacturing process of a gas cell array according to Modification 9; 10 is a flowchart showing a method for manufacturing a gas cell according to Modification 10; Sectional drawing of a package. Sectional drawing of a package and a lid. The figure which illustrates the state after the ampoule 200 is destroyed. FIG. 14 is a cross-sectional view of a gas cell array 70 according to Modification 11; Sectional drawing of the gas cell which concerns on the modification 12. FIG. Sectional drawing of the gas cell in the modification 13. FIG. Sectional drawing of the gas cell which concerns on the modification 15. FIG. 18 is a flowchart showing a method for manufacturing a gas cell according to Modification 15.

1. Configuration FIG. 1 is a block diagram illustrating a configuration of a magnetic measurement apparatus 1 according to an embodiment. The magnetic measurement device 1 is a biological state measurement device that measures a magnetic field generated from a living body, such as a magnetic field generated from the heart (magnetomagnetic field) or a magnetic field generated from the brain (cerebral magnetic field), as an indicator of the state of the living body. The magnetic measurement apparatus 1 includes a gas cell array 10, a pump light irradiation unit 20, a probe light irradiation unit 30, and a detection unit 40. The gas cell array 10 has a plurality of gas cells. An alkali metal gas (for example, cesium (Cs)) is enclosed in the gas cell. The pump light irradiation unit 20 outputs pump light that interacts with alkali metal atoms (for example, light having a wavelength of 894 nm corresponding to the cesium D1 line). The pump light has a circularly polarized component. When pump light is irradiated, the outermost electrons of the alkali metal atoms are excited and spin polarization occurs. The spin-polarized alkali metal atom precesses due to the magnetic field B generated by the object to be measured. The spin polarization of one alkali metal atom relaxes with time, but since the pump light is CW (Continuous Wave) light, the formation and relaxation of spin polarization are repeated simultaneously and continuously. . As a result, a steady spin polarization is formed as a whole group of atoms.

  The probe light irradiation unit 30 outputs probe light having a linearly polarized light component. Before and after transmission through the gas cell, the polarization plane of the probe light rotates due to the Faraday effect. The rotation angle of the polarization plane is a function of the magnetic field B. The detection unit 40 detects the rotation angle of the probe light. The detection unit 40 includes a photodetector that outputs a signal corresponding to the amount of incident light, a processor that processes the signal, and a memory that stores data. The processor calculates the magnitude of the magnetic field B using the signal output from the photodetector. The processor writes data indicating the calculated result in the memory. Thus, the user can obtain information on the magnetic field B generated from the object to be measured.

  FIG. 2 is an external view of the gas cell array 10. In this example, the gas cell array 10 includes a plurality (2 × 2) of gas cells that are two-dimensionally arranged on the xy plane. The gas cell is a cell (box) in which an alkali metal gas is sealed. The gas cell is formed using a light-transmitting material such as quartz glass or borosilicate glass. The gas cell array 10 includes dummy cells provided so as to surround 2 × 2 gas cells on the xy plane. The 2 × 2 gas cells in the center are cells that contribute to the measurement of the magnetic field, but the dummy cells are cells that do not contribute to the measurement of the magnetic field.

  FIG. 3 is a cross-sectional view of the gas cell array 10 taken along the line III-III. This cross section is parallel to the xz plane. In this section, a gas cell 110, a gas cell 120, and a dummy cell 130 are shown. A through hole 111 is provided between the gas cell 110 and the dummy cell 130. A through hole 121 is provided between the gas cell 120 and the dummy cell 130.

  FIG. 4 is a sectional view of the gas cell array 10 taken along the line IV-IV. This cross section is parallel to the xy plane. In this section, a gas cell 110, a gas cell 120, a gas cell 140, a gas cell 150, and a dummy cell 130 are shown. A through hole 141 is provided between the gas cell 140 and the dummy cell 130. A through hole 151 is provided between the gas cell 150 and the dummy cell 130. The functions of the through hole 111, the through hole 121, the through hole 141, and the through hole 151 will be described later.

2. Manufacturing Method FIG. 5 is a flowchart showing manufacturing steps of the gas cell array 10. In step S100 (coating process), a coating layer is formed on a plate material for forming a gas cell. For example, paraffin is used for the coating layer. The coating layer is applied by a dry process or a wet process. The coating layer is applied to both the front and back surfaces of the plate material.
In step S110 (cutting step), the plate material on which the coating layer is formed is cut.

  FIG. 6 is a diagram showing the cut plate material. The plate material 11 and the plate material 12 are members that form the upper surface and the lower surface of the gas cell array 10. Here, “upper” refers to the positive z-axis direction of FIG. 1, and “lower” refers to the negative z-axis direction. The plate material 21, the plate material 22, the plate material 23, and the plate material 24 are members that form the outer side surface of the gas cell array 10. The “external side surface” refers to a surface that is perpendicular to the xy plane and is exposed to the outside. The plate material 31, the plate material 32, the plate material 33, the plate material 34, the plate material 35, the plate material 41, and the plate material 42 are members that form gas cells. The plate material 34 and the plate material 35 are provided with grooves (concave portions) that become through holes (the through hole 111, the through hole 121, the through hole 141, and the through hole 151). In this example, the plate material 31, the plate material 32, and the plate material 33 form a wall surface parallel to the xz plane. The plate material 31, the plate material 32, and the plate material 33 are arranged in this order in the direction in which the y-axis coordinate increases. The plate material 34, the plate material 35, the plate material 41, and the plate material 42 form a wall surface parallel to the yz plane.

Refer to FIG. 5 again. In step S120 (assembly process), the cut plate material is assembled. At this time, in order to store the ampule next, it is assembled until at least one surface is opened. For example, all members other than the plate 11 that forms the upper surface of the gas cell array 10 are assembled. In the assembly, the plate members are joined together by, for example, welding or bonding with an adhesive.
In step S <b> 130 (ampoule storage step), the ampule is stored in the dummy cell 130 in the gas cell array 10. The ampoule is stored from the open surface.

  FIG. 7 is a schematic diagram showing the gas cell array 10 in which ampoules are stored. FIG. 7 shows a cross section similar to FIG. An alkali metal solid 300 is enclosed inside the ampoule 200.

  Refer to FIG. 5 again. In step S140 (sealing step), the gas cell array 10 is sealed. In this example, an inert gas (buffer gas) such as a rare gas is enclosed in the gas cell in addition to the alkali metal gas. Therefore, the gas cell array 10 is sealed in an inert gas atmosphere. Specifically, the open surface member (for example, the plate member 11 constituting the upper surface) is joined in an inert gas atmosphere.

In step S150 (ampoule breaking step), the ampoule 200 is broken. Specifically, the ampoule 200 is irradiated with laser light focused on the ampoule 200, and a hole is made in the ampoule.
In step S160 (vaporization step), the alkali metal solid in the ampoule 200 is vaporized. Specifically, the alkali metal solid is heated and vaporized by heating the gas cell array 10.
In step S170 (diffusion process), the alkali metal gas is diffused. Specifically, the alkali metal gas is diffused by holding at a certain temperature (desirably higher than room temperature) for a certain period of time.

  FIG. 8 is a schematic diagram showing the gas cell array 10 in which the alkali metal gas is diffused. FIG. 8 shows a cross section similar to FIG. In FIG. 8, white circles schematically show the atoms of alkali metal gas. In the diffusion step, the alkali metal gas is diffused from the dummy cell 130 to the gas cell 110, the gas cell 120, the gas cell 140, and the gas cell 150 through the through hole 111, the through hole 121, the through hole 141, and the through hole 151. If the time for the diffusion process is sufficiently long, the alkali metal gas diffuses almost uniformly in all the gas cells.

  In summary, the manufacturing process of the gas cell array 10 includes a coating process for forming a coating layer on the surface of the plate material (step S100), a cutting process for cutting the plate material on which the coating layer is formed (step S110), An assembling process (step S120) for assembling a plurality of plate members on which the coating layer is formed so as to form a cell surrounded by the surface on which the coating layer is formed, and filling in which the formed cell is filled with an alkali metal gas Process. The plate member has a first surface and a second surface behind the first surface. In the coating process, a coating layer is formed on the first surface and the second surface of the plate material. In the assembly process, a plurality of cells including a first cell (gas cell 110) surrounded by a plurality of surfaces including the first surface and a second cell (gas cell 120) surrounded by a plurality of surfaces including the second surface are formed. Is done. The gas cell array 10 includes a third cell (dummy cell 130) in which an alkali metal solid is placed. The plate material between the first cell and the second cell and the third cell is provided with a through hole. The filling process includes an ampoule destruction process (step S150), a vaporization process (step S160), and a diffusion process (step S170). The alkali metal solid is placed in the third cell while being enclosed in an ampoule. The destruction process is a process of destroying the ampoule before the diffusion process. The vaporization step is a step of generating an alkali metal gas by vaporizing the alkali metal solid in the third cell. The diffusion step is a step of diffusing the generated alkali metal gas from the third cell to the first cell and the second cell through the through hole.

  Further, the gas cell array 10 includes an outer wall that forms a closed space, an inner wall that partitions the closed space into a plurality of cells, a through hole that is formed on the inner wall and connects at least one cell among adjacent cells, And an enclosed alkali metal gas. The “cell” here is not a completely closed space, but may be a space connected to another cell by a through hole.

  FIG. 9 is a diagram illustrating a configuration of a comparative example. FIG. 9 shows an example in which a coating process is performed after the assembly process. In this case, a thick coating layer may be formed at a specific place such as a corner portion of the cell or a boundary portion between the surfaces. Thus, when the coating layer thickness is non-uniform, when the alkali metal atom moving inside the gas cell collides with the wall surface, the movement of the atom after the collision may partially change from the others. is there. This may cause measurement errors.

  On the other hand, according to the present embodiment, since the coating layer is formed before the assembly process, a more uniform coating layer is formed as compared with the case where the coating layer is formed after the assembly process. That is, according to this embodiment, compared with the case where a coating layer is formed after an assembly process, the uniformity of the characteristic between gas cells improves (a variation is suppressed).

3. Other Embodiments The present invention is not limited to the above-described embodiments, and various modifications can be made. Hereinafter, some modifications will be described. Two or more of the following modifications may be used in combination.

3-1. Modification 1
FIG. 10 is an external view of a gas cell array 15 according to the first modification. The shape of the gas cell array is not limited to that described in the embodiment. The gas cell array 15 includes a dummy cell 160 instead of the dummy cell 130. The dummy cell 160 is different from the dummy cell 130 of the gas cell array 10 in the positional relationship with the gas cell group. The dummy cell is a cell that does not contribute to the measurement of the magnetic field and that stores an ampoule. The gas cell array 10 includes a gas cell 110 (an example of the first cell), a gas cell 120 (an example of the second cell), a gas cell 140 (an example of the fourth cell), a gas cell 150 (an example of the fifth cell), and a dummy cell 130 (the first cell). An example of 3 cells). The cell group including the gas cell 110, the gas cell 120, the gas cell 140, and the gas cell 150 is two-dimensionally arranged (arranged in a matrix) on the xy plane. With respect to this cell group, the dummy cell 130 is located on the same xy plane as the cell group. On the other hand, in the gas cell array 15, the dummy cells 160 (another example of the third cells) are stacked above the cell group (in the positive z-axis direction, that is, the direction perpendicular to the plane to which the cell group belongs). . According to the gas cell array 15, the size on the xy plane can be reduced as compared with the gas cell array 10. Further, when light having a component parallel to the xy plane is incident, the attenuation amount of the component parallel to the xy plane is less than that of the gas cell array 10 so as not to pass through the dummy cell.

  FIG. 11 is a cross-sectional view of the gas cell array 15 taken along the line XI-XI. In this example, the gas cell 110 and the gas cell 120 have a through hole 112 and a through hole 122 connected to the dummy cell 160. Although not shown in this cross-sectional view, the gas cell 140 and the gas cell 150 also have a through hole connected to the dummy cell 160.

3-2. Modification 2
FIG. 12 is a schematic diagram illustrating an arrangement of through holes according to the second modification. FIG. 12 shows a cross section similar to FIG. In the embodiment, the example in which the gas cell array 10 has gas cells arranged in 2 rows and 2 columns has been described, but the number of gas cells is not limited to this. FIG. 12 shows a gas cell array having gas cells arranged in 3 rows and 3 columns. In the configuration in which dummy cells are arranged around the gas cell group on the same surface as the gas cell group 10 as in the gas cell array 10, when the number of gas cells is 3 rows and 3 columns or more, there are gas cells that are not adjacent to the dummy cells. In the example of FIG. 12, the gas cell at the center of the gas cells in 3 rows and 3 columns is not adjacent to the dummy cell. In this case, the central gas cell has a through hole connected to another adjacent gas cell. In the diffusion step, the alkali metal gas diffuses through the through hole and another adjacent gas cell.

3-3. Modification 3
FIG. 13 is a schematic diagram illustrating an arrangement of through holes according to the third modification. FIG. 13 shows an example in which dummy cells are stacked in the z direction in a gas cell array having 3 × 3 gas cells, as in the first modification. FIG. 13 shows a cross section similar to FIG. In this example, gas cells other than the central gas cell among the 3 × 3 gas cells are not adjacent to the dummy cell. In this case, gas cells other than the central gas cell have a through-hole connected to the central gas cell. In the diffusion step, the alkali metal gas diffuses through the through hole and the central gas cell.

3-4. Modification 4
The specific contents of the ampoule breaking process are not limited to those described in the embodiment. Ampoule 200 may have a portion where two materials having different coefficients of thermal expansion are bonded together. In this case, in the ampoule destruction process, the ampoule 200 (the entire gas cell array in which the ampule 200 is stored) is heated instead of the laser beam irradiation. At the time of heating, heat is applied to such an extent that the ampule 200 is destroyed due to the difference in thermal expansion coefficient.

3-5. Modification 5
The manufacturing method of the gas cell array is not limited to that illustrated in FIG. Another process may be added to the process shown in FIG. Alternatively, the order of the steps may be changed, and some of the steps may be omitted. For example, the order of the coating process and the cutting process may be switched. In this case, the plate material is first cut and a coating layer is formed after cutting. In another example, a step of peeling a part of the coating layer may be introduced after the coating layer is formed. In this case, the coating layer of the joint portion with the other plate material is peeled off. Alternatively, the coating layer on the surface exposed to the outside of the plate material may be peeled off.

  In another example, the sealing process may be performed under vacuum. In this case, the gas cell does not have an inert gas inside, but has only an alkali metal gas.

3-6. Modification 6
The shape of the dummy cell is not limited to that described in the embodiment. The dummy cell may have a recess for holding ampule fragments. The concave portion is provided at, for example, a corner portion in order to minimize the influence on the measurement of the magnetic field. The concave portion may be formed in the plate material before assembly, or may be formed by joining a portion that becomes the concave portion to a plate material having a hole. In addition, an adhesive substance may be stored in the recess so that the ampule fragments do not move during movement (carrying).

3-7. Modification 7
The shape of the gas cell is not limited to that described in the embodiment. In the embodiment, an example in which the shape of the gas cell is a cube has been described. However, the shape of the gas cell may be a polyhedron other than a cube or a part of a curved surface such as a cylinder. For example, the gas cell may have a reservoir (metal reservoir) for accumulating alkali metal solids when the temperature drops below the temperature at which alkali metal atoms solidify. In addition, the alkali metal should just be gasified at the time of a measurement, and does not need to be always a gas state.

3-8. Modification 8
FIG. 14 is a flowchart showing a manufacturing process of the gas cell array according to the modification 8. In this example, the inner wall of the gas cell does not have a coating layer. Accordingly, the flow of FIG. 14 is obtained by omitting the coating process from the flow of FIG. Even in this case, the concentration of the alkali metal gas in the cell can be made more uniform as compared with an example in which the alkali metal solid is stored in a closed cell (a cell not connected to other cells) one by one. . That is, the uniformity of the characteristics of the plurality of gas cells can be further improved. The gas cell array has a structure in which a plurality of partition walls are sandwiched between two flat plates (upper surface and lower surface). By using two flat plates, it is possible to improve the uniformity of the shape as compared to manufacturing a single gas cell that is not an array using individual plate materials.

3-9. Modification 9
FIG. 15 is a flowchart showing the manufacturing process of the gas cell array according to the modification 9. In this example, the gas cell array does not have dummy cells. A part of the gas cell array is connected to the reservoir through a glass tube. The reservoir contains a solid of an alkali metal compound. In step S210 (vaporization step), the reservoir is heated. The alkali metal compound is decomposed by heating the reservoir, and an alkali metal gas is generated. In step S220 (diffusion process), the alkali metal gas diffuses into the gas cell via the glass tube. The alkali metal gas that has reached the gas cell diffuses into each cell through the through hole. After sufficient time has passed, the glass tube is heated and cut to seal the gas cell. Even in this case, the concentration of the alkali metal gas in the cell can be made more uniform as compared with an example in which the alkali metal gas is sealed in cells that are closed one by one (cells not connected to other cells). . That is, the uniformity of the characteristics of the plurality of gas cells can be further improved. The gas cell array has a structure in which a plurality of partition walls are sandwiched between two flat plates (upper surface and lower surface). By using two flat plates, it is possible to improve the uniformity of the shape as compared to manufacturing a single gas cell that is not an array using individual plate materials. In the flow of FIG. 15, the coating process may be omitted. The gas cell array may have dummy cells.

  In yet another example, the present manufacturing method may be used for manufacturing a single gas cell instead of a gas cell array. In this case, the dummy cell is not formed, and the alkali metal solid may be stored directly in the gas cell (without using an ampoule).

3-10. Modification 10
FIG. 16 is a flowchart showing a method for manufacturing a gas cell according to Modification 10. In step S300 (joining step), the package and the lid are joined. The package and lid are formed of a material having resistance to alkali metals, such as borosilicate glass and quartz glass.

  FIG. 17 is a cross-sectional view of the package. FIG. 17 shows a cross section in the xy plane. The package 50 includes a main chamber 51, a constricted hole 52, and an ampoule housing chamber 53. The main chamber 51 is a space filled with gas. The ampoule storage chamber 53 is a space for storing the ampoule 200. The narrowed hole 52 is a hole that connects (communications) the main chamber 51 and the ampoule housing chamber 53. The coating layer described in the embodiment has an effect of suppressing relaxation of the spin-polarized state, but when the diameter of the constricted hole 52 is increased, the non-relaxation effect by the coating layer is impaired. On the contrary, when the diameter of the constriction hole 52 becomes small, it takes time to flow in the coating agent described later. Therefore, the diameter of the narrow hole 52 is designed in consideration of the balance between the two. That is, this cell has a wall surface that forms a closed space inside. Here, the alkali metal solid in the ampoule is not shown.

  FIG. 18 is a cross-sectional view of the package and the lid. 18 shows a cross section in the xz plane (FIG. 17 shows a cross section XVII-XVII in FIG. 18). The lid 60 is a lid that seals the main chamber 51, the narrow hole 52, and the ampoule housing chamber 53 of the package 50. The ampoule storage chamber 53 only needs to have a size and shape that can accommodate the ampoule 200. In this example, the ampule housing chamber 53 has a V-shaped cross section (wedge shape). The package 50 and the lid 60 are bonded by bonding using low-melting glass or optical bonding. The package 50 and the lid 60 are joined in a state where the entire system is evacuated (depressurized atmosphere) using a vacuum pump or the like.

  Refer to FIG. 16 again. In step S310 (coating process), coating is performed. That is, a coating layer is formed on the inner wall of the main chamber 51. The coating layer is formed of a hydrocarbon such as paraffin or an organosilicon compound such as OTS (octadecyltrichlorosilane). These coating materials are poured into the main chamber 51 through a flow path (not shown) in a liquid or gas state. A plurality of flow paths may be provided depending on the configuration of the manufacturing apparatus.

  In step S320 (ampoule breaking step), the ampoule 200 is broken. The ampoule 200 is destroyed in a vacuum environment. Ampoule destruction is performed using, for example, laser light. In this case, the laser beam is irradiated through the lid so as to focus on the ampoule 200. In the ampoule 200, a hole is opened at a position irradiated with the laser beam. In order to improve the absorption rate of laser light, a film of a light absorbing material may be formed on the ampoule 200. In another example, an ultrashort pulse laser (a laser that emits light having a pulse width of 1 nanosecond or less, such as a picosecond laser or a femtosecond laser) may be used. The ampoule 200 may contain a buffer gas (for example, a rare gas) for suppressing the movement speed of alkali metal atoms in addition to the alkali metal.

  FIG. 19 is a diagram illustrating a state after the ampoule 200 is destroyed. A through-hole 201 is opened in the ampoule 200 by laser light irradiation. When the ampule 200 contains the buffer gas, the buffer gas diffuses to the outside of the ampoule 200 through the through hole 201.

  Refer to FIG. 16 again. In step S330 (diffusion process), the alkali metal is diffused. The alkali metal gas is diffused by holding the cell at a certain temperature (preferably higher than room temperature) for a certain period of time.

  In step S340 (airtight sealing step), the cell is airtightly sealed. The hermetic sealing is performed in a vacuum environment. Airtight sealing refers to sealing of the flow path of the coating material. The hermetic sealing is performed using a sealing material such as solder or low-melting glass. Alternatively, the glass itself constituting the cell (package 50 and lid 60) may be melted and hermetically sealed. A laser may be used for heating the sealing material or the cell.

  In step S350 (saturation step), the alkali metal gas is absorbed into the coating layer until the saturated state is reached. This is because when the number of alkali metal atoms in the cell decreases (that is, when the alkali metal atom density in the cell decreases), the measurement result may be affected. At this time, the cell may be heated. For example, the cell is stored at 85 ° C. for 10 hours.

  For example, in the technique of Non-Patent Document 1, there is a problem that it is necessary for an operator to have a skillful glassworking technique and is not suitable for industrial stable production. However, according to the manufacturing method of the modification 10, a gas cell can be stably manufactured irrespective of an operator's skill. Furthermore, in the technique of Non-Patent Document 1, it is necessary to join a pipe for introducing an alkali metal to the cell, and there is a case where it is difficult to manufacture a small cell in consideration of the size of the pipe. According to the manufacturing method of Modification Example 10, a small cell can also be manufactured.

3-11. Modification 11
FIG. 20 is a cross-sectional view of a gas cell array 70 according to the eleventh modification. FIG. 20 shows a cross section in the xz plane. In the modification 10, an example in which a single cell is manufactured has been described. However, a cell array having a plurality of cells may be formed by the method of the modification 10. The gas cell array 70 includes a package 71 and a lid 72. The package 71 has a plurality of main chambers 711, narrow holes 712, and ampoule housing chambers 713. Two adjacent main chambers 711 are connected by a constriction hole 712. The ampoule housing chamber 713 and the adjacent main chamber 711 are connected by a narrowed hole 712. Although FIG. 20 shows an example in which only one ampoule storage chamber 713 is provided, a plurality of ampoule storage chambers 713 may be provided. The manufacturing method is the same as that of Modification 10 except that the shape of the package and the lid is different.

3-12. Modification 12
FIG. 21 is a cross-sectional view of a gas cell according to Modification 12. FIG. 21 shows a cross section in the xy plane. Unlike the gas cell of the modification 10, the gas cell of the modification 12 does not have an ampoule storage chamber. This gas cell has a main chamber 51. The ampoule 200 is accommodated in the main room 51. The manufacturing method is the same as that of Modification 10 except that the shape of the package and the lid is different.

3-13. Modification 13
FIG. 22 is a cross-sectional view of a gas cell in Modification 13. This gas cell has a main chamber 51, a constricted hole 52, and an ampoule housing chamber 53. In the ampoule storage chamber 53, an ampoule 200 and an ampoule 250 are stored. The ampoule 250 is an ampoule in which a coating material is enclosed. In this example, the ampule 250 is broken in the coating process. The ampoule 250 is destroyed in the same manner as the ampoule 200. The other points are the same as in Modification 10.

3-14. Modification 14
Ampoule destruction is not limited to laser irradiation. The ampoule 200 may collide with the inner wall of the ampoule housing chamber 53 by applying a mechanical shock or vibration to destroy the ampoule. In another example, the ampoule 200 may be given heat that generates thermal stress, and the ampoule 200 may be broken by the thermal stress.

3-15. Modification 15
FIG. 23 is a cross-sectional view of a gas cell according to Modification 15. FIG. 23 shows a cross section in the xz plane. This gas cell has a main chamber 51 and an alkali metal storage chamber 54. In the modified example 15, the ampule 200 is not used. The alkali metal storage chamber 54 is a space (chamber) provided in the package 50. This space is closed when the gas cell is manufactured. An alkali metal solid is placed in the alkali metal storage chamber 54.

  FIG. 24 is a flowchart showing a gas cell manufacturing method according to Modification 15. In step S300 (joining step), the package and the lid are joined. In step S310 (coating process), coating is performed. In step S420 (storage chamber destruction step), the alkali metal storage chamber 54, more specifically, the wall surface between the main chamber 51 and the alkali metal storage chamber 54 is destroyed. The destruction of the alkali metal storage chamber 54 is performed by, for example, laser light irradiation, similarly to the destruction of the ampoule 200. In step S330 (diffusion process), the alkali metal is diffused. In step S340 (airtight sealing step), the cell is airtightly sealed. In step S350 (saturation step), the alkali metal gas is absorbed into the coating layer until the saturated state is reached. In this example, a coating material storage chamber for storing the coating material may be provided in the package. In this case, the coating material accommodation chamber is destroyed in the coating process.

3-16. Modification 16 Instead of forming a through hole by laser light irradiation, a process of generating thermal stress by light irradiation and cleaving the ampoule 200 by this thermal stress may be used. According to this method, degassing (gas released from glass or the like during the process) may be reduced and the sensor characteristics may be improved as compared with the case of forming a through hole by light irradiation. In this case, a laser having a pulse width of nanoseconds or less may be used. Further, in order to facilitate the cleaving of the ampule 200, a stress concentration portion (for example, a scratch) may be formed in the ampule 200.

  In the above-described embodiment and modification, an example in which an alkali metal atom is introduced into a gas cell mainly in a gas (gas) state has been described. However, the state when introducing alkali metal atoms into the gas cell is not limited to gas. The alkali metal atom may be introduced into the gas cell in any state of solid, liquid, or gas. Also, capsules may be used instead of ampoules.

DESCRIPTION OF SYMBOLS 10 ... Gas cell array, 11 ... Plate material, 12 ... Plate material, 15 ... Gas cell array, 20 ... Pump light irradiation unit, 21 ... Plate material, 22 ... Plate material, 23 ... Plate material, 24 ... Plate material, 30 ... Probe light irradiation unit, 31 ... Plate material, 32 ... Plate material, 33 ... Plate material, 34 ... Plate material, 35 ... Plate material, 40 ... Detection unit, 41 ... Plate material, 42 ... Plate material, 50 ... Package, 51 ... Main chamber, 52 ... Stenosis hole, 53 ... Ampoule housing chamber 54 ... Alkali metal storage chamber, 60 ... Lid, 70 ... Gas cell array, 71 ... Package, 72 ... Lid, 110 ... Gas cell, 111 ... Through hole, 112 ... Through hole, 120 ... Gas cell, 121 ... Through hole, 122 ... Through hole, 130 ... dummy cell, 140 ... gas cell, 141 ... through hole, 150 ... gas cell, 151 ... through hole, 160 ... dummy cell, 200 ... ampoule, 2 0 ... ampoule, 300 ... alkali metal solids, 711 ... main chamber, 712 ... constriction hole 713 ... ampoule accommodating chamber

Claims (5)

A bonding step of bonding a package and a lid to form a main chamber;
A coating step of forming a coating layer on the inner wall of the main chamber;
And a filling step of filling the main chamber with an alkali metal gas. A bonding step of bonding a package and a lid to form a main chamber;
A coating step of forming a coating layer on the inner wall of the main chamber;
And a filling step of filling the main chamber with an alkali metal gas. The main room,
Stenosis hole,
An ampoule housing chamber communicating with the main chamber through the narrowed hole;
A gas cell comprising: an alkali metal gas hermetically sealed in the main chamber.   The gas cell according to claim 3, wherein the ampoule housing chamber has a V-shaped cross section.   A magnetic measuring device comprising the gas cell according to claim 3.

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