WO2021246150A1 - Glass for atomic cells, atomic cell, and method for manufacturing atomic cell - Google Patents

Glass for atomic cells, atomic cell, and method for manufacturing atomic cell Download PDF

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Publication number
WO2021246150A1
WO2021246150A1 PCT/JP2021/018704 JP2021018704W WO2021246150A1 WO 2021246150 A1 WO2021246150 A1 WO 2021246150A1 JP 2021018704 W JP2021018704 W JP 2021018704W WO 2021246150 A1 WO2021246150 A1 WO 2021246150A1
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WIPO (PCT)
Prior art keywords
glass
atomic
window portion
cell
atomic cell
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PCT/JP2021/018704
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French (fr)
Japanese (ja)
Inventor
雅之 板谷
紀彰 益田
智 新井
恭平 瀬川
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日本電気硝子株式会社
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Publication of WO2021246150A1 publication Critical patent/WO2021246150A1/en

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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S1/00—Masers, i.e. devices using stimulated emission of electromagnetic radiation in the microwave range
    • H01S1/06—Gaseous, i.e. beam masers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/26—Automatic control of frequency or phase; Synchronisation using energy levels of molecules, atoms, or subatomic particles as a frequency reference

Definitions

  • the present invention relates to an atomic cell glass used for an atomic oscillator or the like, an atomic cell, and a method for manufacturing the atomic cell.
  • Atomic clocks are equipped with an atomic oscillator that oscillates based on energy transitions in alkali metal atoms such as cesium (Cs) and rubidium (Rb), and this atomic clock is an oscillator that can obtain highly accurate oscillation characteristics over the long term.
  • alkali metal atoms such as cesium (Cs) and rubidium (Rb)
  • Cs cesium
  • Rb rubidium
  • the operating principle of an atomic oscillator can be divided into several methods, but an atomic oscillator using the quantum interference effect (CPT: Coherent Population Trapping) has a frequency stability that is about three orders of magnitude higher than that of a crystal oscillator. It has been known.
  • CPT Coherent Population Trapping
  • a vapor-like alkali metal is enclosed in an atomic cell and used.
  • a buffer gas such as neon (Ne) or argon (Ar) is further enclosed in the atomic cell and used.
  • Patent Document 1 discloses an atomic cell sealed with glass by an anodic bonding method.
  • the document discloses that aluminosilicate glass, borosilicate glass, and quartz glass are used as the glass.
  • an object of the present invention is to provide a glass for an atomic cell, which is unlikely to cause a change in oscillation frequency in an atomic oscillator due to transmission of He gas.
  • the present inventors have found that the shielding property of He gas is improved by defining the molar volume of glass, and propose it as the present invention.
  • the glass according to the present invention is characterized by being a glass for an atomic cell having a molar volume of 26.0 cm 3 / mol or less.
  • atom cell glass according to the present invention in mass%, preferably contains a Li 2 O 0.5 ⁇ 10%. This facilitates the fabrication of glass-sealed atomic cells using the anodic bonding method.
  • the glass for an atomic cell according to the present invention has a glass composition of SiO 2 50 to 70%, Al 2 O 3 10 to 30%, MgO + CaO + SrO + BaO 9 to 30%, Li 2 O 0.5 to 10 in mass%. %, Na 2 O 0 to 3%, and B 2 O 30 to 3% are preferably contained.
  • the glass for an atomic cell according to the present invention preferably contains 9 to 30% of MgO + CaO in terms of mass% as a glass composition.
  • the glass for atomic cells according to the present invention preferably has a glass composition of CaO / MgO of 1.0 or less in terms of mass ratio.
  • Atom cell glass according to the present invention preferably contains substantially no B 2 O 3.
  • Atom cell glass of the present invention are preferably substantially free of P 2 O 5.
  • the glass for an atomic cell according to the present invention substantially does not contain Na 2 O.
  • the atomic cell according to the present invention has a first main surface and a second main surface facing each other, and is provided with a through hole penetrating between the first main surface and the second main surface.
  • the glass for the atomic cell constitutes at least one of the light entering surface and the light emitting surface of the atomic cell.
  • the cell body is made of glass.
  • the cell body, the first window portion, and the second window portion have the same glass composition.
  • the method for manufacturing an atomic cell according to the present invention is a method for manufacturing an atomic cell configured according to the present invention, wherein the first window portion is arranged on the first main surface of the cell body, and the cell is manufactured.
  • a step of joining the cell body and the second window portion and sealing the inside of the through hole is provided.
  • the cell body, the first window portion, and the second window portion are joined by an anode joining method, respectively.
  • the present invention it is possible to provide a glass for an atomic cell that is unlikely to cause a change in oscillation frequency in an atomic oscillator due to transmission of He gas.
  • the glass for an atomic cell of the present invention is characterized by having a molar volume of 26.0 cm 3 / mol or less. The reason for limiting the molar volume of glass as described above is shown below.
  • the molar volume of glass is an index showing the structural denseness of glass, and is an element that makes it difficult for He in the atmosphere to pass through the inside from the glass surface and enter the inside of the atomic cell. As a result, it is possible to make it even more difficult for the oscillation frequency of the atomic oscillator to change with time.
  • the molar volume of the glass is 26.0 cm 3 / mol or less, preferably 25.5 cm 3 / mol or less, more preferably 25.0 cm 3 / mol or less, still more preferably 24.5 cm 3 / mol or less, particularly preferably 24. It is 0.0 cm 3 / mol or less.
  • the lower limit of the molar volume of the glass for atomic cells is preferably 19.0 cm 3 / mol or more, and more preferably 20.0 cm 3 / mol or more.
  • Li 2 O is a component that significantly lowers the melting temperature and softening point of glass and enables anode bonding as a moving component in glass.
  • the content of Li 2 O is preferably 0.5 to 10%, more preferably 1 to 8%, still more preferably 1.5 to 7%, and particularly preferably 2 to 6%. If the Li 2 O content is too low, the melting temperature of the glass becomes unreasonably high, and the small amount of Li ions, which are moving components, makes anodic bonding extremely difficult. On the other hand, if the content of Li 2 O is too large, the Li component is precipitated from the glass surface (alkaline blowing), and the weather resistance and acid resistance of the glass are significantly lowered.
  • SiO 2 is a mesh-forming component of glass, it is a component that stabilizes glass and enhances weather resistance and acid resistance.
  • the content of SiO 2 is preferably 50 to 70%, more preferably 52 to 67%, still more preferably 54 to 65%, and particularly preferably 56 to 63%. If the content of SiO 2 is too small, the weather resistance and acid resistance tend to decrease. On the other hand, if the content of SiO 2 is too high, the melting temperature of the glass rises, the manufacturing cost rises, and devitrification (unintended crystals) precipitates from the glass, which hinders anode bonding.
  • Al 2 O 3 is a component that stabilizes glass and improves weather resistance and acid resistance.
  • the content of Al 2 O 3 is preferably 10 to 30%, more preferably 12 to 28%, still more preferably 15 to 25%, and particularly preferably 18 to 23%. If the content of Al 2 O 3 is too small, the weather resistance and acid resistance are lowered, and devitrified substances are deposited from the glass melt at the time of melting, which hinders anode bonding. On the other hand, even if the content of Al 2 O 3 is too large, devitrified substances are deposited from the glass melt at the time of melting, which hinders anode bonding. In addition, melting may become difficult.
  • Na 2 O is a component that lowers the melting temperature and softening point of glass and enables anode bonding as a moving component in glass. However, if the content of Na 2 O is too large, the Na component may precipitate from the glass surface (alkaline blowing), and the weather resistance and acid resistance of the glass may decrease.
  • the content of Na 2 O is preferably 0 to 3%, more preferably 0 to 2%, still more preferably 0 to 1%, and particularly preferably substantially not contained.
  • substantially free means that the content in the glass composition is 1000 ppm or less.
  • the alkaline earth oxides MgO, CaO, SrO, and BaO have the effect of lowering the molar volume of the glass, it makes it difficult for He in the atmosphere to pass through the inside from the glass surface and enter the inside of the atomic cell. It is an ingredient.
  • the alkaline earth oxide is a component that stabilizes the glass while lowering the melting temperature and the softening point of the glass.
  • vitrification may become difficult due to the precipitation of devitrified substances during melting, and it could be tentatively molded.
  • the content of MgO + CaO + SrO + BaO is preferably 9 to 30%, more preferably 10 to 25%, still more preferably 11 to 22%, and particularly preferably 12 to 20%. If the content of MgO + CaO + SrO + BaO is too small, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes remarkably unstable and vitrification becomes difficult.
  • MgO + CaO + SrO + BaO refers to the total amount of MgO, CaO, SrO, and BaO contained in the glass.
  • MgO is a component that stabilizes glass while lowering the melting temperature and softening point of glass. Further, since it has the effect of lowering the molar volume of the glass, it is a component that makes it difficult for He in the atmosphere to enter the inside of the atomic cell from the surface of the glass through the inside.
  • the content of MgO is preferably 5 to 25%, more preferably 7 to 23%, still more preferably 8 to 20%, and particularly preferably 9 to 18%. If the content of MgO is too small, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes remarkably unstable and vitrification becomes difficult. On the other hand, if the content of MgO is too large, the glass becomes unstable and the weather resistance and acid resistance of the glass are lowered.
  • CaO is a component that stabilizes glass while lowering the melting temperature and softening point of glass. Further, since it has the effect of lowering the molar volume of the glass, it is a component that makes it difficult for He in the atmosphere to enter the inside of the atomic cell from the surface of the glass through the inside.
  • the CaO content is preferably 0 to 15%, more preferably 0.5 to 12%, still more preferably 1 to 10%, and particularly preferably 3 to 8%. If the CaO content is too low, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes significantly unstable and vitrification becomes difficult. On the other hand, if the amount of CaO is too large, the glass becomes unstable and the weather resistance and acid resistance of the glass are lowered.
  • SrO is a component that stabilizes the glass while lowering the melting temperature and softening point of the glass. Further, since it has the effect of lowering the molar volume of the glass, it is a component that makes it difficult for He in the atmosphere to enter the inside of the atomic cell from the surface of the glass through the inside.
  • the content of SrO is preferably 0 to 10%, more preferably 0.1 to 8%, still more preferably 0.5 to 5%, and particularly preferably 1 to 3%. If the content of SrO is too small, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes remarkably unstable and vitrification becomes difficult.
  • BaO is a component that stabilizes glass while lowering the melting temperature and softening point of glass. Further, since it has the effect of lowering the molar volume of the glass, it is a component that makes it difficult for He in the atmosphere to enter the inside of the atomic cell from the surface of the glass through the inside.
  • the content of BaO is preferably 0 to 8%, more preferably 0.1 to 5%, still more preferably 0.5 to 3%, and particularly preferably 1 to 2%. If the BaO content is too low, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes significantly unstable and vitrification becomes difficult. On the other hand, if the content of BaO is too large, the glass becomes unstable and the weather resistance and acid resistance of the glass are lowered. In addition, since the movement of Li ions in the glass is hindered, the anodic bonding property is significantly deteriorated.
  • the alkaline earth oxide is MgO as long as it does not interfere with other properties of glass (meltability, stability, weather resistance, acid resistance, etc.).
  • CaO are preferred.
  • the content of MgO + CaO in the glass is preferably 9 to 30%, more preferably 10 to 25%, still more preferably 11 to 22%, and particularly preferably 12 to 20%. If the content of MgO + CaO is too small, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes remarkably unstable and vitrification becomes difficult. On the other hand, if the content of MgO + CaO is too large, the glass becomes unstable and the weather resistance and acid resistance of the glass are lowered.
  • MgO + CaO refers to the total amount of MgO and CaO contained in the glass.
  • the mass ratio "CaO / MgO" obtained by dividing the CaO content in the glass by the MgO content is preferably 1.0 or less. It is more preferably 0.8 or less, still more preferably 0.6 or less, and particularly preferably 0.4 or less.
  • B 2 O 3 is a mesh-forming component of glass, it is a component that stabilizes glass and enhances weather resistance and acid resistance. However, since it is a component that remarkably increases the molar volume of glass, it remarkably lowers the shielding property of He gas.
  • the content of B 2 O 3 is preferably 0 to 3%, more preferably 0 to 2%, still more preferably 0 to 1%, and particularly preferably substantially not contained.
  • substantially free means that the content in the glass is 1000 ppm or less.
  • P 2 O 5 is a mesh-forming component of glass, it is a component that stabilizes glass. However, since it is a component that increases the molar volume of glass, it lowers the shielding property of He gas.
  • the content of P 2 O 5 is preferably 0 to 5%, more preferably 0 to 2%, still more preferably 0 to 1%, and particularly preferably substantially not contained.
  • substantially free means that the content in the glass is 1000 ppm or less.
  • TiO 2 is a component that improves the weather resistance and acid resistance of glass.
  • the content of TiO 2 is preferably 0 to 5%, more preferably 0.1 to 4%, still more preferably 0.5 to 3%, and particularly preferably 1 to 2%. If the content of TiO 2 is too large, the viscosity (softening point, etc.) of the glass becomes high, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting.
  • ZnO is a component that forms the skeleton of glass.
  • the ZnO content is preferably 0 to 5%, more preferably 0.1 to 3%, still more preferably 0.5 to 2%, and particularly preferably 1 to 2%.
  • ZnO content is high, devitrification lumps caused by ZnO are likely to precipitate, which raises the liquidus temperature and raises the melting cost.
  • K 2 O is a component that lowers the melting temperature and softening point of glass.
  • the K 2 O content is 0-3%, and preferably from 0.1 to 2%, more preferably 0.2 to 1%. If the K 2 O content is too low, the melting temperature of the glass will be unreasonably high. On the other hand, if the amount of K 2 O is too large, the alkaline component is precipitated from the glass surface (alkaline blowing), and the weather resistance and acid resistance of the glass are lowered.
  • FIG. 1 is a schematic perspective view showing an atomic cell according to an embodiment of the present invention.
  • FIG. 2 is a schematic cross-sectional view of a portion of FIG. 1 along the line AA.
  • the atomic cell 1 includes a cell body 2, a first window portion 3, and a second window portion 4.
  • the cell body 2 has a first main surface 2a and a second main surface 2b facing each other.
  • the cell body 2 is provided with a through hole 5 penetrating from the first main surface 2a to the second main surface 2b.
  • the shape of the cell body 2 is a rectangular parallelepiped.
  • the shape of the cell body 2 may be, for example, a columnar shape, and is not particularly limited.
  • the shape of the through hole 5 is cylindrical.
  • the shape of the through hole 5 may be, for example, a rectangular parallelepiped shape, and is not particularly limited.
  • the cell body 2 is made of glass. As a result, the transparency of the light emitted from the light source is enhanced, and the alkali metal can be effectively irradiated.
  • the cell body 2 may be made of metal, crystal, silicon, or the like.
  • a first window portion 3 is provided on the first main surface 2a of the cell body 2.
  • the first window portion 3 is provided so as to close one side of the through hole 5 of the cell body 2.
  • a second window portion 4 is provided on the second main surface 2b of the cell main body 2. The second window portion 4 is provided so as to close the other side of the through hole 5 of the cell body 2.
  • the shapes of the first window portion 3 and the second window portion 4 are rectangular plates, respectively.
  • the shapes of the first window portion 3 and the second window portion 4 may be disk-shaped, respectively, as long as they can close the through hole 5, and are not particularly limited.
  • the first window portion 3 and the second window portion 4 are made of the glass for an atomic cell of the present invention.
  • the glass for an atomic cell of the present invention has a molar volume of 26.0 cm 3 / mol or less.
  • the atomic cell 1 is a container in which an alkali metal or a buffer gas is sealed, and the vapor-like alkali metal or the buffer gas is enclosed in the through hole 5 of the atomic cell 1 and used.
  • the light emitted from a light source (not shown) is incident on the light entering surface 1a of the first window portion 3.
  • the light incident from the light incoming surface 1a is irradiated to the alkali metal in the through hole 5, and is emitted from the light emitting surface 1b of the second window portion 4.
  • the light emitted from the light emitting surface 1b is incident on a photodetector (not shown) and a signal is acquired.
  • the alkali metal cesium (Cs) or rubidium (Rb) can be used.
  • the buffer gas neon or argon can be used.
  • the feature of this embodiment is that the molar volume of the glass for an atomic cell constituting the first window portion 3 and the second window portion 4 is 26.0 cm 3 / mol or less.
  • the molar volume constituting the first window portion 3 and the second window portion 4 is 26.0 cm 3 / mol or less.
  • He in the atmosphere invades the inside of the atomic cell through the glass. hard.
  • the buffer gas such as neon or argon enclosed inside the atomic cell 1 will come off. Therefore, in the atomic cell 1, it is possible to make it difficult for the oscillation frequency of the atomic oscillator to change with time.
  • the molar volume of the glass for an atomic cell is preferably 25.5 cm 3 / mol or less, more preferably 25.0 cm 3 / mol or less, still more preferably 24.5 cm 3 / mol or less, and particularly preferably 24. It is 0 cm 3 / mol or less.
  • the lower limit of the molar volume of the glass for atomic cells is preferably 19.0 cm 3 / mol or more, and more preferably 20.0 cm 3 / mol or more.
  • the anode can be easily used at a relatively low temperature of 320 ° C. or lower. Joining is possible. Therefore, in the atomic cell 1, it is possible to obtain an atomic cell having excellent adhesiveness and airtightness.
  • the average coefficient of thermal expansion of the glass for atomic cells at 30 ° C. to 300 ° C. is, for example, 30 ⁇ 10 -7 / ° C. or higher and 120 ⁇ 10 -7 / ° C. or lower.
  • both the first window portion 3 and the second window portion 4 are made of glass for an atomic cell having a molar volume of 26.0 cm 3 / mol or less.
  • at least one of the first window portion 3 and the second window portion 4 may be made of glass for an atomic cell having a molar volume of 26.0 cm 3 / mol or less.
  • At least one of the incoming surface 1a and the outgoing surface 1b may be made of glass for an atomic cell having a molar volume of 26.0 cm 3 / mol or less.
  • the portion of at least one of the first window portion 3 and the second window portion 4 facing the through hole 5 which is the encapsulation portion of the alkali metal may be composed of glass.
  • the cell body 2 has the same glass composition as the first window portion 3 and the second window portion 4. More preferably, the cell body 2 has substantially the same glass composition as the first window portion 3 and the second window portion 4. That is, it is preferable that the cell body 2 is also made of the glass for the atomic cell of the present invention. In this case, He in the atmosphere is more difficult to penetrate inside the atomic cell. Further, it is more difficult for the buffer gas enclosed inside the atomic cell 1 to come off. Therefore, it is possible to make it even more difficult for the oscillation frequency of the atomic oscillator to change with time.
  • the glass having the "glass composition of the same system" means that the top three components having a large content among the components contained in the glass composition match each other.
  • the glass having "substantially the same glass composition” has the same components as each other as the glass composition, and the content of each component of the other glass is equal to the composition of one glass. Includes those with a difference in the range of + 5% to -5%.
  • the through hole 5 of the cell body 2 can be formed by, for example, drilling or ultrasonic processing.
  • the hole diameter of the through hole 5 is not particularly limited.
  • the first main surface 2a of the cell body 2 and the first window portion 3 are anodically bonded.
  • an alkali metal is put into the through hole 5 of the cell body 2, and the second main surface 2b of the cell body 2 and the second window portion 4 are anode-bonded.
  • buffer gas is introduced into the through hole 5 and the anode is joined in this buffer gas atmosphere.
  • an inert gas such as neon or argon can be used.
  • the alkali metal can be gasified and used by heating.
  • the alkali metal in the atomic cell 1 may be in a solid state before gasification or in a gasified state.
  • the alkali metal may be directly sealed inside the atomic cell 1 in the form of a gas.
  • the surface roughness Ra of the adhesive surface is preferably 0.3 nm or less, more preferably 0.2 nm or less, and further preferably 0.1 nm or less.
  • the joining can be further strengthened by further applying pressure.
  • the pressure at the time of pressurization is preferably 1 MPa or less, more preferably 0.8 MPa or less, still more preferably 0.5 MPa or less.
  • the lower limit of the pressure at the time of pressurization is preferably 0.01 MPa.
  • the heating temperature in the anode junction is preferably 320 ° C. or lower, 300 ° C. or lower, particularly 250 ° C. or lower, which is the temperature at which cesium azide, which is a Cs supply source, begins to release Cs gas.
  • the cell body 2 and the first window portion 3 and the second window portion 4 are all made of glass, the atomic cell 1 can be manufactured easily and efficiently. And can be firmly bonded at low temperature. Further, since the cell body 2 and the first window portion 3 and the second window portion 4 have the same coefficient of thermal expansion, the airtightness can be further improved.
  • the glass for an atomic cell and the atomic cell of the present invention can be used, for example, in an atomic oscillator that makes a resonance transition of an alkali metal by utilizing the quantum interference effect of two types of light having different wavelengths.
  • it may be used for an atomic oscillator that makes a resonance transition of an alkali metal by utilizing a double resonance phenomenon caused by light and microwave, and is not particularly limited. In either case, it is possible to make it difficult for the oscillation frequency of the atomic oscillator to change with time.
  • Example 1 to 7 and Comparative Examples 1 to 2 Glasses for atomic cells of Examples 1 to 7 and Comparative Examples 1 and 2 shown in Table 1 below were prepared.
  • a glass batch containing various oxides, carbonates, etc. is prepared so as to have the glass composition shown in Table 1 below, and this is placed in a platinum crucible at 1400 to 1500 ° C. 6 After melting for a time, the molten glass was poured into a stainless steel mold and molded. Then, the obtained glass was held at 650 ° C. for 1 hour for annealing treatment.
  • the density of the obtained glass was measured by the Archimedes method.
  • the average coefficient of thermal expansion in the temperature range of 30 to 300 ° C. was measured using a push rod type coefficient of thermal expansion measuring device.
  • the molar volume was calculated from the formula amount of the glass composition and the density of the glass.
  • the window part made of the obtained glass was placed on the main surface of the cell body made of the obtained glass, and the cell body and the window part were anodically bonded. After that, an alkali metal was placed in the through hole. Further, another window portion made of the obtained glass is placed on the main surface of the cell body on the opposite side to the above, and the inside of the through hole is sealed by anodic joining the cell body and the window portion. Atomic cells were made. The anode bonding was performed at 320 ° C., 300 ° C., and 250 ° C. with an applied voltage of 1000 V.
  • the airtightness of the atomic cell was evaluated as follows. A low-viscosity red ink was dripped along the interface of the anode bonding of the prepared atomic cell, and the bonding interface was set to be perpendicular to the ground surface. Then, after 72 hours, the bonding interface was observed with an optical microscope (200 times). Observing the bonding interface from the vertical direction, the red ink permeating the area of less than 10% of the bonding interface is " ⁇ ", and the area of 10 to less than 90% is " ⁇ ", 90 to 100%. Those that permeated the area were designated as "x".
  • the prepared atomic cell was used to evaluate the shielding property of He gas.
  • 10 5 atoms / cm ⁇ s ⁇ atoms is the detection limit of the transmittance of the He gas, equal to or less than the detection limit, it is ensured a high shielding property of the He gas.
  • the evaluation of the permeability of He gas was measured at 30 ° C. using gas chromatography.
  • the glasses of Examples 1 to 7 is the molar volume of 26.0cm 3 / mol or less, the helium permeability was 10 5 atom / cm ⁇ s ⁇ atoms or less, shielding of the He gas It was excellent.
  • the glasses of Comparative Examples 1-2 the molar volume exceeded 26.0cm 3 / mol, since the helium transmittance exceeds the 10 5 atom / cm ⁇ s ⁇ atoms, shielding of the He gas was poor ..

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Abstract

Provided is a glass for atomic cells, whereby the oscillating frequency in an atomic oscillator is less likely to be changed over time.　The glass for atomic cells has a molar volume of 26.0 cm3/mole or less.

Description

原子セル用ガラス、原子セル、及び原子セルの製造方法Glass for atomic cells, atomic cells, and methods for manufacturing atomic cells
　本発明は、原子発振器などに用いられる原子セル用ガラス、原子セル、及び原子セルの製造方法に関する。 The present invention relates to an atomic cell glass used for an atomic oscillator or the like, an atomic cell, and a method for manufacturing the atomic cell.
　原子時計は、セシウム（Ｃｓ）やルビジウム（Ｒｂ）等のアルカリ金属原子におけるエネルギー遷移に基づいて発振する原子発振器を備えており、この原子発振器は、長期的に高精度な発振特性が得られる発振器として知られている。原子発振器の動作原理は、いくつかの方式に区別されるが、量子干渉効果（ＣＰＴ：Ｃｏｈｅｒｅｎｔ　Ｐｏｐｕｌａｔｉｏｎ　Ｔｒａｐｐｉｎｇ）を利用した原子発振器は、水晶発振器と比較して３桁程度高い周波数安定性を有することが知られている。 Atomic clocks are equipped with an atomic oscillator that oscillates based on energy transitions in alkali metal atoms such as cesium (Cs) and rubidium (Rb), and this atomic clock is an oscillator that can obtain highly accurate oscillation characteristics over the long term. Known as. The operating principle of an atomic oscillator can be divided into several methods, but an atomic oscillator using the quantum interference effect (CPT: Coherent Population Trapping) has a frequency stability that is about three orders of magnitude higher than that of a crystal oscillator. It has been known.
　このような原子発振器では、原子セル内に蒸気状のアルカリ金属が封入されて用いられる。また、原子発振器として必要な性能を確保するため、原子セル内には、さらにネオン（Ｎｅ）やアルゴン（Ａｒ）などのバッファガスが封入されて用いられている。 In such an atomic oscillator, a vapor-like alkali metal is enclosed in an atomic cell and used. Further, in order to secure the performance required as an atomic oscillator, a buffer gas such as neon (Ne) or argon (Ar) is further enclosed in the atomic cell and used.
　特許文献１には、陽極接合法によりガラスで密封された原子セルが開示されている。そして、同文献には、ガラスとして、アルミノケイ酸ガラス、ホウケイ酸ガラス、石英ガラスを用いることが開示されている。 Patent Document 1 discloses an atomic cell sealed with glass by an anodic bonding method. The document discloses that aluminosilicate glass, borosilicate glass, and quartz glass are used as the glass.
特開２０１９－８７８６５号公報Japanese Unexamined Patent Publication No. 2019-87865
　しかしながら、特許文献１が開示する一般的なガラスを用いた原子セルは、大気中のヘリウム（Ｈｅ）がガラスの外表面から内部を透過して原子セルの内部に侵入する、いわゆるＨｅガスの遮蔽性に問題が生じたり、あるいは内部に存在するバッファガスがセル外部に漏洩する、いわゆるセル抜けが生じたりする虞がある。そのため、時間経過による周波数変動が生じ易いという問題がある。 However, in the atomic cell using general glass disclosed in Patent Document 1, helium (He) in the atmosphere permeates the inside from the outer surface of the glass and invades the inside of the atomic cell, so-called He gas shielding. There is a risk that a problem may occur in the properties, or that the buffer gas existing inside may leak to the outside of the cell, that is, so-called cell omission may occur. Therefore, there is a problem that frequency fluctuation is likely to occur with the passage of time.
　そこで、本発明の目的は、Ｈｅガスの透過による原子発振器における発振周波数の経時変化を生じさせ難い原子セル用ガラスを提供することにある。 Therefore, an object of the present invention is to provide a glass for an atomic cell, which is unlikely to cause a change in oscillation frequency in an atomic oscillator due to transmission of He gas.
　本発明者等は、鋭意努力した結果、ガラスのモル体積を規定することにより、Ｈｅガスの遮蔽性が改善することを見出し、本発明として提案するものである。 As a result of diligent efforts, the present inventors have found that the shielding property of He gas is improved by defining the molar volume of glass, and propose it as the present invention.
　詳述すると、本発明に係るガラスは、モル体積が２６．０ｃｍ３／モル以下である原子セル用ガラスであることを特徴としている。 More specifically, the glass according to the present invention is characterized by being a glass for an atomic cell having a molar volume of 26.0 cm 3 / mol or less.
　さらに、本発明に係る原子セル用ガラスは、質量％で、Ｌｉ２Ｏ　０．５～１０％を含有していることが好ましい。これにより、陽極接合法を用いて、ガラスで密封された原子セルの作製が容易になる。 Furthermore, atom cell glass according to the present invention, in mass%, preferably contains a Li 2 O 0.5 ~ 10%. This facilitates the fabrication of glass-sealed atomic cells using the anodic bonding method.
　さらに、本発明に係る原子セル用ガラスは、ガラス組成として、質量％で、ＳｉＯ２　５０～７０％、Ａｌ２Ｏ３　１０～３０％、ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ　９～３０％、Ｌｉ２Ｏ　０．５～１０％、Ｎａ２Ｏ　０～３％、Ｂ２Ｏ３　０～３％を含有していることが好ましい。 Further, the glass for an atomic cell according to the present invention has a glass composition of SiO 2 50 to 70%, Al 2 O 3 10 to 30%, MgO + CaO + SrO + BaO 9 to 30%, Li 2 O 0.5 to 10 in mass%. %, Na 2 O 0 to 3%, and B 2 O 30 to 3% are preferably contained.
　本発明に係る原子セル用ガラスは、ガラス組成として、質量％で、ＭｇＯ＋ＣａＯ　９～３０％を含有していることが好ましい。 The glass for an atomic cell according to the present invention preferably contains 9 to 30% of MgO + CaO in terms of mass% as a glass composition.
　本発明に係る原子セル用ガラスは、ガラス組成として、質量比で、ＣａＯ／ＭｇＯが１．０以下であることが好ましい。 The glass for atomic cells according to the present invention preferably has a glass composition of CaO / MgO of 1.0 or less in terms of mass ratio.
　本発明に係る原子セル用ガラスは、実質的にＢ２Ｏ３を含有しないことが好ましい。 Atom cell glass according to the present invention preferably contains substantially no B 2 O 3.
　本発明に係る原子セル用ガラスは、実質的にＰ２Ｏ５を含有しないことが好ましい。 Atom cell glass of the present invention are preferably substantially free of P 2 O 5.
　本発明に係る原子セル用ガラスは、実質的に、Ｎａ２Ｏを含有しないことが好ましい。 It is preferable that the glass for an atomic cell according to the present invention substantially does not contain Na 2 O.
　本発明に係る原子セルは、対向している第１の主面及び第２の主面を有し、前記第１の主面及び前記第２の主面間を貫通している貫通孔が設けられている、セル本体と、前記セル本体の第１の主面上に設けられており、前記貫通孔の一方側を塞いでいる第１の窓部と、前記セル本体の第２の主面上に設けられており、前記貫通孔の他方側を塞いでいる第２の窓部と、を備え、前記第１の窓部及び前記第２の窓部が、本発明に従って構成される原子セル用ガラスにより構成されている。 The atomic cell according to the present invention has a first main surface and a second main surface facing each other, and is provided with a through hole penetrating between the first main surface and the second main surface. A cell body, a first window portion provided on the first main surface of the cell body and closing one side of the through hole, and a second main surface of the cell body. An atomic cell provided above, comprising a second window portion that closes the other side of the through hole, wherein the first window portion and the second window portion are configured according to the present invention. It is composed of glass for use.
　本発明に係る原子セルは、前記原子セル用ガラスが、前記原子セルの入光面及び出光面のうち少なくとも一方を構成することが好ましい。 In the atomic cell according to the present invention, it is preferable that the glass for the atomic cell constitutes at least one of the light entering surface and the light emitting surface of the atomic cell.
　本発明に係る原子セルは、前記セル本体が、ガラスにより構成されていることが好ましい。 In the atomic cell according to the present invention, it is preferable that the cell body is made of glass.
　本発明に係る原子セルは、前記セル本体、前記第１の窓部、及び前記第２の窓部が、同じガラス組成を有することが好ましい。 In the atomic cell according to the present invention, it is preferable that the cell body, the first window portion, and the second window portion have the same glass composition.
　本発明に係る原子セルの製造方法は、本発明に従って構成される原子セルの製造方法であって、前記第１の窓部を前記セル本体の前記第１の主面上に配置し、前記セル本体と前記第１の窓部とを接合する工程と、前記貫通孔内にアルカリ金属を配置する工程と、前記第２の窓部を前記セル本体の前記第２の主面上に配置し、前記セル本体と前記第２の窓部とを接合し、前記貫通孔内を封止する工程と、を備える。 The method for manufacturing an atomic cell according to the present invention is a method for manufacturing an atomic cell configured according to the present invention, wherein the first window portion is arranged on the first main surface of the cell body, and the cell is manufactured. A step of joining the main body and the first window portion, a step of arranging an alkali metal in the through hole, and the second window portion being arranged on the second main surface of the cell main body. A step of joining the cell body and the second window portion and sealing the inside of the through hole is provided.
　本発明に係る原子セルの製造方法は、前記セル本体と前記第１の窓部及び前記第２の窓部とを、それぞれ、陽極接合法により接合することが好ましい。 In the method for producing an atomic cell according to the present invention, it is preferable that the cell body, the first window portion, and the second window portion are joined by an anode joining method, respectively.
　本発明によれば、Ｈｅガスの透過による原子発振器における発振周波数の経時変化を生じさせ難い原子セル用ガラスを提供することができる。 According to the present invention, it is possible to provide a glass for an atomic cell that is unlikely to cause a change in oscillation frequency in an atomic oscillator due to transmission of He gas.
本発明の一実施形態に係る原子セルを示す模式的斜視図である。It is a schematic perspective view which shows the atomic cell which concerns on one Embodiment of this invention. 図１のＡ－Ａ線に沿う部分の模式的断面図である。It is a schematic cross-sectional view of the part along the line AA of FIG.
　以下、好ましい実施形態について説明する。但し、以下の実施形態は単なる例示であり、本発明は以下の実施形態に限定されるものではない。また、図面において、実質的に同一の機能を有する部材は同一の符号で参照する場合がある。 Hereinafter, preferred embodiments will be described. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. Further, in the drawings, members having substantially the same function may be referred to by the same reference numeral.
　（原子セル用ガラス）
　本発明の原子セル用ガラスは、モル体積が２６．０ｃｍ３／モル以下であることを特徴とする。ガラスのモル体積を上記のように限定した理由を以下に示す。 (Glass for atomic cells)
The glass for an atomic cell of the present invention is characterized by having a molar volume of 26.0 cm 3 / mol or less. The reason for limiting the molar volume of glass as described above is shown below.
　ガラスのモル体積は、ガラスの構造的な緻密さを表す指標であり、大気中のＨｅが、ガラス表面から内部を通って、原子セルの内部に侵入し難くする要素である。これにより、原子発振器における発振周波数の経時変化をより一層生じ難くすることができる。ガラスのモル体積は、２６．０ｃｍ３／モル以下、好ましくは２５．５ｃｍ３／モル以下、より好ましくは２５．０ｃｍ３／モル以下、更に好ましくは２４．５ｃｍ３／モル以下、特に好ましくは２４．０ｃｍ３／モル以下である。なお、原子セル用ガラスのモル体積の下限値は、好ましくは１９．０ｃｍ３／モル以上、より好ましくは２０．０ｃｍ３／モル以上とすることができる。 The molar volume of glass is an index showing the structural denseness of glass, and is an element that makes it difficult for He in the atmosphere to pass through the inside from the glass surface and enter the inside of the atomic cell. As a result, it is possible to make it even more difficult for the oscillation frequency of the atomic oscillator to change with time. The molar volume of the glass is 26.0 cm 3 / mol or less, preferably 25.5 cm 3 / mol or less, more preferably 25.0 cm 3 / mol or less, still more preferably 24.5 cm 3 / mol or less, particularly preferably 24. It is 0.0 cm 3 / mol or less. The lower limit of the molar volume of the glass for atomic cells is preferably 19.0 cm 3 / mol or more, and more preferably 20.0 cm 3 / mol or more.
　ガラス組成を以下のように調整することで、モル体積が２６．０ｃｍ３／モル以下のガラスを得ることができる。なお、各成分の含有量に関する説明において、特に断りのない限り、「％」は「質量％」を意味する。 By adjusting the glass composition as follows, a glass having a molar volume of 26.0 cm 3 / mol or less can be obtained. In the description of the content of each component, "%" means "mass%" unless otherwise specified.
　Ｌｉ２Ｏは、ガラスの溶融温度や軟化点を顕著に下げ、また、ガラス中の可動成分として陽極接合を可能にする成分である。Ｌｉ２Ｏの含有量は、好ましくは０．５～１０％であり、より好ましくは１～８％、更に好ましくは１．５～７％、特に好ましくは２～６％である。Ｌｉ２Ｏの含有量が少な過ぎると、ガラスの溶融温度が不当に高くなり、また可動成分であるＬｉイオンが少ないことにより、陽極接合が顕著に困難になる。一方、Ｌｉ２Ｏの含有量が多過ぎると、Ｌｉ成分がガラス表面から析出したり（アルカリ吹き）、ガラスの耐候性や耐酸性が顕著に低下する。 Li 2 O is a component that significantly lowers the melting temperature and softening point of glass and enables anode bonding as a moving component in glass. The content of Li 2 O is preferably 0.5 to 10%, more preferably 1 to 8%, still more preferably 1.5 to 7%, and particularly preferably 2 to 6%. If the Li 2 O content is too low, the melting temperature of the glass becomes unreasonably high, and the small amount of Li ions, which are moving components, makes anodic bonding extremely difficult. On the other hand, if the content of Li 2 O is too large, the Li component is precipitated from the glass surface (alkaline blowing), and the weather resistance and acid resistance of the glass are significantly lowered.
　ＳｉＯ２は、ガラスの網目形成成分であるため、ガラスを安定化させ、耐候性や耐酸性を高める成分である。ＳｉＯ２の含有量は、好ましくは５０～７０％であり、より好ましくは５２～６７％、更に好ましくは５４～６５％、特に好ましくは５６～６３％である。ＳｉＯ２の含有量が少な過ぎると、耐候性や耐酸性が低下する傾向がある。一方、ＳｉＯ２の含有量が多過ぎると、ガラスの溶融温度が高くなり製造コストが上昇すると共に、失透（意図しない結晶物）がガラス中から析出し、陽極接合に支障をきたす。 Since SiO 2 is a mesh-forming component of glass, it is a component that stabilizes glass and enhances weather resistance and acid resistance. The content of SiO 2 is preferably 50 to 70%, more preferably 52 to 67%, still more preferably 54 to 65%, and particularly preferably 56 to 63%. If the content of SiO 2 is too small, the weather resistance and acid resistance tend to decrease. On the other hand, if the content of SiO 2 is too high, the melting temperature of the glass rises, the manufacturing cost rises, and devitrification (unintended crystals) precipitates from the glass, which hinders anode bonding.
　Ａｌ２Ｏ３は、ガラスを安定化させると共に、耐候性や耐酸性を改善する成分である。Ａｌ２Ｏ３の含有量は、好ましくは１０～３０％であり、より好ましくは１２～２８％、更に好ましくは１５～２５％、特に好ましくは１８～２３％である。Ａｌ２Ｏ３の含有量が少な過ぎると、耐候性や耐酸性が低下し、また溶融時にガラス融液中から失透物が析出し、陽極接合に支障をきたす。一方、Ａｌ２Ｏ３の含有量が多過ぎても、溶融時にガラス融液中から失透物が析出し、陽極接合に支障をきたす。また溶融が困難になる虞がある。 Al 2 O 3 is a component that stabilizes glass and improves weather resistance and acid resistance. The content of Al 2 O 3 is preferably 10 to 30%, more preferably 12 to 28%, still more preferably 15 to 25%, and particularly preferably 18 to 23%. If the content of Al 2 O 3 is too small, the weather resistance and acid resistance are lowered, and devitrified substances are deposited from the glass melt at the time of melting, which hinders anode bonding. On the other hand, even if the content of Al 2 O 3 is too large, devitrified substances are deposited from the glass melt at the time of melting, which hinders anode bonding. In addition, melting may become difficult.
　Ｎａ２Ｏは、ガラスの溶融温度や軟化点を下げ、ガラス中の可動成分として、陽極接合を可能にする成分である。しかし、Ｎａ２Ｏの含有量が多過ぎると、Ｎａ成分がガラス表面から析出したり（アルカリ吹き）、ガラスの耐候性や耐酸性が低下する。Ｎａ２Ｏの含有量は、好ましくは０～３％であり、より好ましくは０～２％、更に好ましくは０～１％、特に実質的に含有しないことが好ましい。ここで、「実質的に含有しない」とは、ガラス組成物中の含有量が１０００ｐｐｍ以下であることを意味する。 Na 2 O is a component that lowers the melting temperature and softening point of glass and enables anode bonding as a moving component in glass. However, if the content of Na 2 O is too large, the Na component may precipitate from the glass surface (alkaline blowing), and the weather resistance and acid resistance of the glass may decrease. The content of Na 2 O is preferably 0 to 3%, more preferably 0 to 2%, still more preferably 0 to 1%, and particularly preferably substantially not contained. Here, "substantially free" means that the content in the glass composition is 1000 ppm or less.
　なお、可動成分としての効果は、Ｌｉ２Ｏ、Ｎａ２Ｏの順に高いため、陽極接合を行う場合、ガラスの他の特性（溶融性、安定性、耐候性、耐酸性等）に支障がない限り、Ｌｉ２Ｏを優先的に選択することが好ましい。 Since the effect as a moving component is higher in the order of Li 2 O and Na 2 O, there is no problem in other properties of glass (meltability, stability, weather resistance, acid resistance, etc.) when anodic bonding is performed. As far as possible, it is preferable to preferentially select Li 2 O.
　アルカリ土類酸化物であるＭｇＯ、ＣａＯ、ＳｒＯ、ＢａＯは、ガラスのモル体積を下げる効果があるため、大気中のＨｅが、ガラス表面から内部を通って、原子セルの内部に侵入し難くする成分である。また、アルカリ土類酸化物は、ガラスの溶融温度や軟化点を下げる成分でありながら、ガラスを安定化させる成分である。特に、ＳｉＯ２、Ａｌ２Ｏ３、Ｌｉ２Ｏを基本成分とするＬＡＳ系ガラスの場合、溶融中に失透物が析出することでガラス化が困難になる虞があり、また仮に成形できたとしても、成型後のガラスに熱を加える際、ガラスから結晶が析出することにより、陽極接合性に多大な悪影響を与える虞がある。従って、本願発明において、アルカリ土類酸化物の効果は重要である。ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯの含有量は、好ましくは９～３０％であり、より好ましくは１０～２５％、更に好ましくは１１～２２％、特に好ましくは１２～２０％である。ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯの含有量が少な過ぎると、ガラスの溶融温度が高くなり溶融が困難になると共に、ガラスが顕著に不安定になり、ガラス化が困難になる。一方、ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯの含有量が多過ぎても、ガラスが不安定になると共に、ガラスの耐候性や耐酸性が低下する。ここで、ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯとは、ガラス中のＭｇＯ、ＣａＯ、ＳｒＯ、ＢａＯの含有量の合量を指す。 Since the alkaline earth oxides MgO, CaO, SrO, and BaO have the effect of lowering the molar volume of the glass, it makes it difficult for He in the atmosphere to pass through the inside from the glass surface and enter the inside of the atomic cell. It is an ingredient. Further, the alkaline earth oxide is a component that stabilizes the glass while lowering the melting temperature and the softening point of the glass. In particular, in the case of LAS-based glass containing SiO 2 , Al 2 O 3 , and Li 2 O as basic components, vitrification may become difficult due to the precipitation of devitrified substances during melting, and it could be tentatively molded. Even so, when heat is applied to the molded glass, crystals may precipitate from the glass, which may have a great adverse effect on the anode bondability. Therefore, in the present invention, the effect of the alkaline earth oxide is important. The content of MgO + CaO + SrO + BaO is preferably 9 to 30%, more preferably 10 to 25%, still more preferably 11 to 22%, and particularly preferably 12 to 20%. If the content of MgO + CaO + SrO + BaO is too small, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes remarkably unstable and vitrification becomes difficult. On the other hand, if the content of MgO + CaO + SrO + BaO is too large, the glass becomes unstable and the weather resistance and acid resistance of the glass are lowered. Here, MgO + CaO + SrO + BaO refers to the total amount of MgO, CaO, SrO, and BaO contained in the glass.
　ＭｇＯは、ガラスの溶融温度や軟化点を下げる成分でありながら、ガラスを安定化させる成分である。また、ガラスのモル体積を下げる効果があるため、大気中のＨｅが、ガラス表面から内部を通って、原子セルの内部に侵入し難くする成分である。ＭｇＯの含有量は、好ましくは５～２５％、より好ましくは７～２３％、更に好ましくは８～２０％、特に好ましくは９～１８％である。ＭｇＯの含有量が少な過ぎると、ガラスの溶融温度が高くなり溶融が困難になると共に、ガラスが顕著に不安定になり、ガラス化が困難になる。一方、ＭｇＯの含有量が多過ぎても、ガラスが不安定になると共に、ガラスの耐候性や耐酸性が低下する。 MgO is a component that stabilizes glass while lowering the melting temperature and softening point of glass. Further, since it has the effect of lowering the molar volume of the glass, it is a component that makes it difficult for He in the atmosphere to enter the inside of the atomic cell from the surface of the glass through the inside. The content of MgO is preferably 5 to 25%, more preferably 7 to 23%, still more preferably 8 to 20%, and particularly preferably 9 to 18%. If the content of MgO is too small, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes remarkably unstable and vitrification becomes difficult. On the other hand, if the content of MgO is too large, the glass becomes unstable and the weather resistance and acid resistance of the glass are lowered.
　ＣａＯは、ガラスの溶融温度や軟化点を下げる成分でありながら、ガラスを安定化させる成分である。また、ガラスのモル体積を下げる効果があるため、大気中のＨｅが、ガラス表面から内部を通って、原子セルの内部に侵入し難くする成分である。ＣａＯの含有量は、好ましくは０～１５％、より好ましくは０．５～１２％、更に好ましくは１～１０％、特に好ましくは３～８％である。ＣａＯの含有量が少な過ぎると、ガラスの溶融温度が高くなり溶融が困難になると共に、ガラスが顕著に不安定になり、ガラス化が困難になる。一方、ＣａＯが多過ぎても、ガラスが不安定になると共に、ガラスの耐候性や耐酸性が低下する。 CaO is a component that stabilizes glass while lowering the melting temperature and softening point of glass. Further, since it has the effect of lowering the molar volume of the glass, it is a component that makes it difficult for He in the atmosphere to enter the inside of the atomic cell from the surface of the glass through the inside. The CaO content is preferably 0 to 15%, more preferably 0.5 to 12%, still more preferably 1 to 10%, and particularly preferably 3 to 8%. If the CaO content is too low, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes significantly unstable and vitrification becomes difficult. On the other hand, if the amount of CaO is too large, the glass becomes unstable and the weather resistance and acid resistance of the glass are lowered.
　ＳｒＯは、ガラスの溶融温度や軟化点を下げる成分でありながら、ガラスを安定化させる成分である。また、ガラスのモル体積を下げる効果があるため、大気中のＨｅが、ガラス表面から内部を通って、原子セルの内部に侵入し難くする成分である。ＳｒＯの含有量は、好ましくは０～１０％、より好ましくは０．１～８％、更に好ましくは０．５～５％、特に好ましくは１～３％である。ＳｒＯの含有量が少な過ぎると、ガラスの溶融温度が高くなり溶融が困難になると共に、ガラスが顕著に不安定になり、ガラス化が困難になる。一方、ＳｒＯが多過ぎても、ガラスが不安定になると共に、ガラスの耐候性や耐酸性が低下する。また、ガラス中のＬｉイオンの可動を阻害するため、陽極接合性が顕著に悪化する。 SrO is a component that stabilizes the glass while lowering the melting temperature and softening point of the glass. Further, since it has the effect of lowering the molar volume of the glass, it is a component that makes it difficult for He in the atmosphere to enter the inside of the atomic cell from the surface of the glass through the inside. The content of SrO is preferably 0 to 10%, more preferably 0.1 to 8%, still more preferably 0.5 to 5%, and particularly preferably 1 to 3%. If the content of SrO is too small, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes remarkably unstable and vitrification becomes difficult. On the other hand, if the amount of SrO is too large, the glass becomes unstable and the weather resistance and acid resistance of the glass are lowered. In addition, since the movement of Li ions in the glass is hindered, the anodic bonding property is significantly deteriorated.
　ＢａＯは、ガラスの溶融温度や軟化点を下げる成分でありながら、ガラスを安定化させる成分である。また、ガラスのモル体積を下げる効果があるため、大気中のＨｅが、ガラス表面から内部を通って、原子セルの内部に侵入し難くする成分である。ＢａＯの含有量は、好ましくは０～８％、より好ましくは０．１～５％、更に好ましくは０．５～３％、特に好ましくは１～２％である。ＢａＯの含有量が少な過ぎると、ガラスの溶融温度が高くなり溶融が困難になると共に、ガラスが顕著に不安定になり、ガラス化が困難になる。一方、ＢａＯの含有量が多過ぎても、ガラスが不安定になると共に、ガラスの耐候性や耐酸性が低下する。また、ガラス中のＬｉイオンの可動を阻害するため、陽極接合性が顕著に悪化する。 BaO is a component that stabilizes glass while lowering the melting temperature and softening point of glass. Further, since it has the effect of lowering the molar volume of the glass, it is a component that makes it difficult for He in the atmosphere to enter the inside of the atomic cell from the surface of the glass through the inside. The content of BaO is preferably 0 to 8%, more preferably 0.1 to 5%, still more preferably 0.5 to 3%, and particularly preferably 1 to 2%. If the BaO content is too low, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes significantly unstable and vitrification becomes difficult. On the other hand, if the content of BaO is too large, the glass becomes unstable and the weather resistance and acid resistance of the glass are lowered. In addition, since the movement of Li ions in the glass is hindered, the anodic bonding property is significantly deteriorated.
　モル体積を低く抑えつつ、陽極接合を効果的に行う観点から、ガラスの他の特性（溶融性、安定性、耐候性、耐酸性等）に支障がない限り、アルカリ土類酸化物は、ＭｇＯとＣａＯを選択することが好ましい。ガラス中のＭｇＯ＋ＣａＯの含有量は、好ましくは９～３０％、より好ましくは１０～２５％、更に好ましくは１１～２２％、特に好ましくは１２～２０％である。ＭｇＯ＋ＣａＯの含有量が少な過ぎると、ガラスの溶融温度が高くなり溶融が困難になると共に、ガラスが顕著に不安定になり、ガラス化が困難になる。一方、ＭｇＯ＋ＣａＯの含有量が多過ぎても、ガラスが不安定になると共に、ガラスの耐候性や耐酸性が低下する。ここで、ＭｇＯ＋ＣａＯとは、ガラス中のＭｇＯとＣａＯの含有量の合量を指す。 From the viewpoint of effective anodic bonding while keeping the molar volume low, the alkaline earth oxide is MgO as long as it does not interfere with other properties of glass (meltability, stability, weather resistance, acid resistance, etc.). And CaO are preferred. The content of MgO + CaO in the glass is preferably 9 to 30%, more preferably 10 to 25%, still more preferably 11 to 22%, and particularly preferably 12 to 20%. If the content of MgO + CaO is too small, the melting temperature of the glass becomes high and melting becomes difficult, and the glass becomes remarkably unstable and vitrification becomes difficult. On the other hand, if the content of MgO + CaO is too large, the glass becomes unstable and the weather resistance and acid resistance of the glass are lowered. Here, MgO + CaO refers to the total amount of MgO and CaO contained in the glass.
　更に、モル体積を低く抑えつつ、効果的に陽極接合を行う観点から、ガラス中のＣａＯの含有量をＭｇＯの含有量で除した質量比「ＣａＯ／ＭｇＯ」は、好ましくは１．０以下、より好ましくは０．８以下、更に好ましくは０．６以下、特に好ましくは０．４以下である。 Further, from the viewpoint of effectively performing anode bonding while keeping the molar volume low, the mass ratio "CaO / MgO" obtained by dividing the CaO content in the glass by the MgO content is preferably 1.0 or less. It is more preferably 0.8 or less, still more preferably 0.6 or less, and particularly preferably 0.4 or less.
　Ｂ２Ｏ３は、ガラスの網目形成成分であるため、ガラスを安定化させ、耐候性や耐酸性を高める成分である。しかし、ガラスのモル体積を顕著に上昇させる成分であるため、顕著にＨｅガスの遮蔽性を低下させる。Ｂ２Ｏ３の含有量は、好ましくは０～３％、より好ましくは０～２％、更に好ましくは０～１％、特に実質的に含有しないことが好ましい。ここで、「実質的に含有しない」とは、ガラス中の含有量が１０００ｐｐｍ以下であることを意味する。 Since B 2 O 3 is a mesh-forming component of glass, it is a component that stabilizes glass and enhances weather resistance and acid resistance. However, since it is a component that remarkably increases the molar volume of glass, it remarkably lowers the shielding property of He gas. The content of B 2 O 3 is preferably 0 to 3%, more preferably 0 to 2%, still more preferably 0 to 1%, and particularly preferably substantially not contained. Here, "substantially free" means that the content in the glass is 1000 ppm or less.
　Ｐ２Ｏ５は、ガラスの網目形成成分であるため、ガラスを安定化させる成分である。しかし、ガラスのモル体積を上げる成分であるため、Ｈｅガスの遮蔽性を低下させる。Ｐ２Ｏ５の含有量は、好ましくは０～５％、より好ましくは０～２％、更に好ましくは０～１％、特に実質的に含有しないことが好ましい。ここで、「実質的に含有しない」とは、ガラス中の含有量が１０００ｐｐｍ以下であることを意味する。 Since P 2 O 5 is a mesh-forming component of glass, it is a component that stabilizes glass. However, since it is a component that increases the molar volume of glass, it lowers the shielding property of He gas. The content of P 2 O 5 is preferably 0 to 5%, more preferably 0 to 2%, still more preferably 0 to 1%, and particularly preferably substantially not contained. Here, "substantially free" means that the content in the glass is 1000 ppm or less.
　ＴｉＯ２は、ガラスの耐候性、耐酸性を向上させる成分である。ＴｉＯ２の含有量は、好ましくは０～５％、より好ましくは０．１～４％、更に好ましくは０．５～３％、特に好ましくは１～２％である。ＴｉＯ２の含有量が多過ぎると、ガラスの粘性（軟化点等）が高くなると共に、ガラスが熱的に不安定になり、溶融時にガラスが失透し易くなる。 TiO 2 is a component that improves the weather resistance and acid resistance of glass. The content of TiO 2 is preferably 0 to 5%, more preferably 0.1 to 4%, still more preferably 0.5 to 3%, and particularly preferably 1 to 2%. If the content of TiO 2 is too large, the viscosity (softening point, etc.) of the glass becomes high, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting.
　ＺｎＯは、ガラスの骨格を形成する成分である。ＺｎＯの含有量は、好ましくは０～５％、より好ましくは０．１～３％、更に好ましくは０．５～２％、特に好ましくは１～２％である。ＺｎＯの含有量が多くなると、ＺｎＯに起因する失透ブツが析出し易くなり、これにより、液相温度が上昇することで溶融コストが上がる。 ZnO is a component that forms the skeleton of glass. The ZnO content is preferably 0 to 5%, more preferably 0.1 to 3%, still more preferably 0.5 to 2%, and particularly preferably 1 to 2%. When the ZnO content is high, devitrification lumps caused by ZnO are likely to precipitate, which raises the liquidus temperature and raises the melting cost.
　Ｋ２Ｏは、ガラスの溶融温度や軟化点を下げる成分である。Ｋ２Ｏの含有量は０～３％であり、好ましくは０．１～２％、より好ましくは０．２～１％である。Ｋ２Ｏの含有量が少な過ぎると、ガラスの溶融温度が不当に高くなる。一方、Ｋ２Ｏが多過ぎると、アルカリ成分がガラス表面から析出したり（アルカリ吹き）、ガラスの耐候性や耐酸性が低下する。 K 2 O is a component that lowers the melting temperature and softening point of glass. The K 2 O content is 0-3%, and preferably from 0.1 to 2%, more preferably 0.2 to 1%. If the K 2 O content is too low, the melting temperature of the glass will be unreasonably high. On the other hand, if the amount of K 2 O is too large, the alkaline component is precipitated from the glass surface (alkaline blowing), and the weather resistance and acid resistance of the glass are lowered.
　（原子セル）
　図１は、本発明の一実施形態に係る原子セルを示す模式的斜視図である。図２は、図１のＡ－Ａ線に沿う部分の模式的断面図である。 (Atomic cell)
FIG. 1 is a schematic perspective view showing an atomic cell according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a portion of FIG. 1 along the line AA.
　図１及び図２に示すように、原子セル１は、セル本体２、第１の窓部３、及び第２の窓部４を備える。 As shown in FIGS. 1 and 2, the atomic cell 1 includes a cell body 2, a first window portion 3, and a second window portion 4.
　セル本体２は、対向している第１の主面２ａ及び第２の主面２ｂを有する。セル本体２では、第１の主面２ａから第２の主面２ｂに貫通する貫通孔５が設けられている。 The cell body 2 has a first main surface 2a and a second main surface 2b facing each other. The cell body 2 is provided with a through hole 5 penetrating from the first main surface 2a to the second main surface 2b.
　本実施形態において、セル本体２の形状は、直方体状である。なおセル本体２の形状は、例えば円柱状であってもよく、特に限定されない。また、本実施形態において、貫通孔５の形状は、円柱状である。貫通孔５の形状も、例えば直方体状であってもよく、特に限定されない。 In the present embodiment, the shape of the cell body 2 is a rectangular parallelepiped. The shape of the cell body 2 may be, for example, a columnar shape, and is not particularly limited. Further, in the present embodiment, the shape of the through hole 5 is cylindrical. The shape of the through hole 5 may be, for example, a rectangular parallelepiped shape, and is not particularly limited.
　本実施形態において、セル本体２は、ガラスにより構成されている。これにより、光源から出射された光の透過性が高まり、効果的にアルカリ金属を照射できる。もっとも、セル本体２は、金属、水晶、シリコン等により構成されていてもよい。 In the present embodiment, the cell body 2 is made of glass. As a result, the transparency of the light emitted from the light source is enhanced, and the alkali metal can be effectively irradiated. However, the cell body 2 may be made of metal, crystal, silicon, or the like.
　セル本体２の第１の主面２ａ上には、第１の窓部３が設けられている。第１の窓部３は、セル本体２の貫通孔５の一方側を塞ぐように設けられている。また、セル本体２の第２の主面２ｂ上には、第２の窓部４が設けられている。第２の窓部４は、セル本体２の貫通孔５の他方側を塞ぐように設けられている。 A first window portion 3 is provided on the first main surface 2a of the cell body 2. The first window portion 3 is provided so as to close one side of the through hole 5 of the cell body 2. Further, a second window portion 4 is provided on the second main surface 2b of the cell main body 2. The second window portion 4 is provided so as to close the other side of the through hole 5 of the cell body 2.
　本実施形態において、第１の窓部３及び第２の窓部４の形状は、それぞれ、矩形板状である。第１の窓部３及び第２の窓部４の形状は、貫通孔５を塞ぐことができれば、それぞれ、円盤状であってもよく、特に限定されない。 In the present embodiment, the shapes of the first window portion 3 and the second window portion 4 are rectangular plates, respectively. The shapes of the first window portion 3 and the second window portion 4 may be disk-shaped, respectively, as long as they can close the through hole 5, and are not particularly limited.
　第１の窓部３及び第２の窓部４は、本発明の原子セル用ガラスにより構成されている。本発明の原子セル用ガラスは、モル体積が２６．０ｃｍ３／モル以下である。 The first window portion 3 and the second window portion 4 are made of the glass for an atomic cell of the present invention. The glass for an atomic cell of the present invention has a molar volume of 26.0 cm 3 / mol or less.
　ところで、原子セル１は、アルカリ金属やバッファガスが封入される容器であり、原子セル１の貫通孔５内に蒸気状のアルカリ金属やバッファガスが封入されて用いられる。アルカリ金属やバッファガスが貫通孔５内に封入された原子セル１では、図示しない光源から出射された光が第１の窓部３の入光面１ａから入射される。入光面１ａから入射された光は、貫通孔５内のアルカリ金属に照射され、第２の窓部４の出光面１ｂから出射される。出光面１ｂから出射された光は、図示しない光検出器に入射され信号が取得される。なお、アルカリ金属としては、セシウム（Ｃｓ）やルビジウム（Ｒｂ）を用いることができる。また、バッファガスとしては、ネオンやアルゴンを用いることができる。 By the way, the atomic cell 1 is a container in which an alkali metal or a buffer gas is sealed, and the vapor-like alkali metal or the buffer gas is enclosed in the through hole 5 of the atomic cell 1 and used. In the atomic cell 1 in which the alkali metal or the buffer gas is enclosed in the through hole 5, the light emitted from a light source (not shown) is incident on the light entering surface 1a of the first window portion 3. The light incident from the light incoming surface 1a is irradiated to the alkali metal in the through hole 5, and is emitted from the light emitting surface 1b of the second window portion 4. The light emitted from the light emitting surface 1b is incident on a photodetector (not shown) and a signal is acquired. As the alkali metal, cesium (Cs) or rubidium (Rb) can be used. Further, as the buffer gas, neon or argon can be used.
　本実施形態の特徴は、第１の窓部３及び第２の窓部４を構成する原子セル用ガラスのモル体積が２６．０ｃｍ３／モル以下であることにある。このように、第１の窓部３及び第２の窓部４を構成するモル体積が２６．０ｃｍ３／モル以下であるため、大気中のＨｅがガラスを通って原子セルの内部に侵入し難い。また、原子セル１の内部に封入されているネオンやアルゴンなどのバッファガスのセル抜けが生じ難い。そのため、原子セル１では、原子発振器における発振周波数の経時変化を生じ難くすることができる。 The feature of this embodiment is that the molar volume of the glass for an atomic cell constituting the first window portion 3 and the second window portion 4 is 26.0 cm 3 / mol or less. As described above, since the molar volume constituting the first window portion 3 and the second window portion 4 is 26.0 cm 3 / mol or less, He in the atmosphere invades the inside of the atomic cell through the glass. hard. In addition, it is unlikely that the buffer gas such as neon or argon enclosed inside the atomic cell 1 will come off. Therefore, in the atomic cell 1, it is possible to make it difficult for the oscillation frequency of the atomic oscillator to change with time.
　本発明において、原子セル用ガラスのモル体積は、好ましくは２５．５ｃｍ３／モル以下、より好ましくは２５．０ｃｍ３／モル以下、更に好ましくは２４．５ｃｍ３／モル以下、特に好ましくは２４．０ｃｍ３／モル以下である。原子セル用ガラスのモル体積が上記数値範囲内である場合、大気中のＨｅが、ガラス表面から内部を通って、原子セルの内部に侵入し難い。これにより、原子発振器における発振周波数の経時変化をより一層生じ難くすることができる。なお、原子セル用ガラスのモル体積の下限値は、好ましくは１９．０ｃｍ３／モル以上、より好ましくは２０．０ｃｍ３／モル以上とすることができる。 In the present invention, the molar volume of the glass for an atomic cell is preferably 25.5 cm 3 / mol or less, more preferably 25.0 cm 3 / mol or less, still more preferably 24.5 cm 3 / mol or less, and particularly preferably 24. It is 0 cm 3 / mol or less. When the molar volume of the atomic cell glass is within the above numerical range, it is difficult for He in the atmosphere to pass through the inside from the glass surface and enter the inside of the atomic cell. As a result, it is possible to make it even more difficult for the oscillation frequency of the atomic oscillator to change with time. The lower limit of the molar volume of the glass for atomic cells is preferably 19.0 cm 3 / mol or more, and more preferably 20.0 cm 3 / mol or more.
　また、第１の窓部３及び第２の窓部４を構成する原子セル用ガラスのＬｉ２Ｏの含有量が０．５％以上であるため、３２０℃以下の比較的低温で容易に陽極接合が可能になる。そのため、原子セル１では、接着性及び気密性に優れる原子セルを得ることができる。 Further, since the content of Li 2 O in the glass for atomic cells constituting the first window portion 3 and the second window portion 4 is 0.5% or more, the anode can be easily used at a relatively low temperature of 320 ° C. or lower. Joining is possible. Therefore, in the atomic cell 1, it is possible to obtain an atomic cell having excellent adhesiveness and airtightness.
　また、原子セル用ガラスの３０℃～３００℃における平均熱膨張係数は、例えば、３０×１０－７／℃以上、１２０×１０－７／℃以下である。 The average coefficient of thermal expansion of the glass for atomic cells at 30 ° C. to 300 ° C. is, for example, 30 × 10 -7 / ° C. or higher and 120 × 10 -7 / ° C. or lower.
　なお、本実施形態では、第１の窓部３及び第２の窓部４の双方が、モル体積が２６．０ｃｍ３／モル以下の原子セル用ガラスにより構成される。もっとも、第１の窓部３及び第２の窓部４のうち少なくとも一方が、モル体積が２６．０ｃｍ３／モル以下の原子セル用ガラスにより構成されていてもよい。入光面１ａ及び出光面１ｂのうち少なくとも一方が、モル体積が２６．０ｃｍ３／モル以下の原子セル用ガラスにより構成されていてもよい。特に、第１の窓部３及び第２の窓部４のうち少なくとも一方におけるアルカリ金属の封入部である貫通孔５に面する部分が、モル体積が２６．０ｃｍ３／モル以下の原子セル用ガラスにより構成されていればよい。 In the present embodiment, both the first window portion 3 and the second window portion 4 are made of glass for an atomic cell having a molar volume of 26.0 cm 3 / mol or less. However, at least one of the first window portion 3 and the second window portion 4 may be made of glass for an atomic cell having a molar volume of 26.0 cm 3 / mol or less. At least one of the incoming surface 1a and the outgoing surface 1b may be made of glass for an atomic cell having a molar volume of 26.0 cm 3 / mol or less. In particular, for an atomic cell having a molar volume of 26.0 cm 3 / mol or less, the portion of at least one of the first window portion 3 and the second window portion 4 facing the through hole 5 which is the encapsulation portion of the alkali metal. It may be composed of glass.
　また、セル本体２は、第１の窓部３及び第２の窓部４と同系統のガラス組成を有することが好ましい。さらに好ましくは、セル本体２は、第１の窓部３及び第２の窓部４と実質的に同じガラス組成を有する。すなわち、セル本体２も、本発明の原子セル用ガラスにより構成されていることが好ましい。この場合、大気中のＨｅが原子セルの内部により一層侵入し難い。また、原子セル１の内部に封入されているバッファガスのセル抜けがより一層生じ難い。そのため、原子発振器における発振周波数の経時変化をより一層生じ難くすることができる。なお、本発明において「同系統のガラス組成」のガラスとは、ガラス組成として含有される成分のうち、含有量の多い上位３成分が互いに一致することを指す。また、本発明において、「実質的に同じガラス組成」のガラスとは、互いにガラス組成として含有される各成分が一致し、一方のガラスの組成に対して他方のガラスの各成分の含有量の差が＋５％～－５％の範囲内であるものを含む。 Further, it is preferable that the cell body 2 has the same glass composition as the first window portion 3 and the second window portion 4. More preferably, the cell body 2 has substantially the same glass composition as the first window portion 3 and the second window portion 4. That is, it is preferable that the cell body 2 is also made of the glass for the atomic cell of the present invention. In this case, He in the atmosphere is more difficult to penetrate inside the atomic cell. Further, it is more difficult for the buffer gas enclosed inside the atomic cell 1 to come off. Therefore, it is possible to make it even more difficult for the oscillation frequency of the atomic oscillator to change with time. In the present invention, the glass having the "glass composition of the same system" means that the top three components having a large content among the components contained in the glass composition match each other. Further, in the present invention, the glass having "substantially the same glass composition" has the same components as each other as the glass composition, and the content of each component of the other glass is equal to the composition of one glass. Includes those with a difference in the range of + 5% to -5%.
　以下、原子セル１の製造方法の一例について説明する。 Hereinafter, an example of the manufacturing method of the atomic cell 1 will be described.
　（原子セルの製造方法）
　原子セル１の製造方法では、まず、セル本体２、第１の窓部３、及び第２の窓部４を用意する。セル本体２の貫通孔５は、例えば、ドリルや超音波加工により形成することができる。貫通孔５の孔径は、特に限定されない。 (Manufacturing method of atomic cell)
In the method for manufacturing the atomic cell 1, first, the cell body 2, the first window portion 3, and the second window portion 4 are prepared. The through hole 5 of the cell body 2 can be formed by, for example, drilling or ultrasonic processing. The hole diameter of the through hole 5 is not particularly limited.
　次に、セル本体２の第１の主面２ａと第１の窓部３とを陽極接合する。次に、セル本体２の貫通孔５にアルカリ金属を入れ、セル本体２の第２の主面２ｂと第２の窓部４とを陽極接合する。なお、セル本体２の第２の主面２ｂと第２の窓部４との陽極接合に際しては、貫通孔５内にバッファガスを導入し、このバッファガス雰囲気において陽極接合を行う。バッファガスとしては、ネオンやアルゴンなどの不活性ガスを用いることができる。また、陽極接合後、加熱によりアルカリ金属をガス化して用いることができる。換言すれば、本発明において原子セル１内におけるアルカリ金属はガス化前の固体等の状態であっても良いし、ガス化された状態であっても良い。なお、アルカリ金属はガス状のまま原子セル１内部に直接封入されても良い。 Next, the first main surface 2a of the cell body 2 and the first window portion 3 are anodically bonded. Next, an alkali metal is put into the through hole 5 of the cell body 2, and the second main surface 2b of the cell body 2 and the second window portion 4 are anode-bonded. When the second main surface 2b of the cell body 2 and the second window portion 4 are joined to the anode, buffer gas is introduced into the through hole 5 and the anode is joined in this buffer gas atmosphere. As the buffer gas, an inert gas such as neon or argon can be used. Further, after the anode bonding, the alkali metal can be gasified and used by heating. In other words, in the present invention, the alkali metal in the atomic cell 1 may be in a solid state before gasification or in a gasified state. The alkali metal may be directly sealed inside the atomic cell 1 in the form of a gas.
　なお、セル本体２と、第１の窓部３及び第２の窓部４とをそれぞれ陽極接合するに際しては、予め接着面を研磨加工しておくことが好ましい。この場合、接着面の表面粗さＲａは、好ましくは０．３ｎｍ以下、より好ましくは０．２ｎｍ以下、さらに好ましくは０．１ｎｍ以下である。 When the cell body 2 and the first window portion 3 and the second window portion 4 are joined to each other by anode, it is preferable to polish the adhesive surface in advance. In this case, the surface roughness Ra of the adhesive surface is preferably 0.3 nm or less, more preferably 0.2 nm or less, and further preferably 0.1 nm or less.
　また、セル本体２と、第１の窓部３及び第２の窓部４とをそれぞれ陽極接合するに際しては、さらに加圧を行うことにより、さらに一層接合を強固にすることができる。加圧の際の圧力は、好ましくは１ＭＰａ以下、より好ましくは０．８ＭＰａ以下、さらに好ましくは０．５ＭＰａ以下である。なお、加圧の際の圧力の下限は、０．０１ＭＰａであることが好ましい。 Further, when the cell body 2 and the first window portion 3 and the second window portion 4 are joined to each other by anode, the joining can be further strengthened by further applying pressure. The pressure at the time of pressurization is preferably 1 MPa or less, more preferably 0.8 MPa or less, still more preferably 0.5 MPa or less. The lower limit of the pressure at the time of pressurization is preferably 0.01 MPa.
　陽極接合における加熱温度は、Ｃｓ供給源であるアジ化セシウムがＣｓガスを放出し始める温度である３２０℃以下、３００℃以下、特に２５０℃以下であることが好ましい。 The heating temperature in the anode junction is preferably 320 ° C. or lower, 300 ° C. or lower, particularly 250 ° C. or lower, which is the temperature at which cesium azide, which is a Cs supply source, begins to release Cs gas.
　このように、本実施形態では、セル本体２と、第１の窓部３及び第２の窓部４が、全てガラスにより構成されているので、簡便かつ効率的に原子セル１を製造することができ、また低温で強固に接合することができる。さらに、セル本体２と、第１の窓部３及び第２の窓部４が同じ熱膨張係数とされているので、気密性をより一層高めることもできる。 As described above, in the present embodiment, since the cell body 2, the first window portion 3 and the second window portion 4 are all made of glass, the atomic cell 1 can be manufactured easily and efficiently. And can be firmly bonded at low temperature. Further, since the cell body 2 and the first window portion 3 and the second window portion 4 have the same coefficient of thermal expansion, the airtightness can be further improved.
　本発明の原子セル用ガラス及び原子セルは、例えば、波長の異なる２種類の光による量子干渉効果を利用してアルカリ金属を共鳴遷移させる原子発振器に用いることができる。もっとも、光及びマイクロ波による二重共鳴現象を利用してアルカリ金属を共鳴遷移させる原子発振器に用いてもよく、特に限定されない。いずれの場合においても、原子発振器における発振周波数の経時変化を生じ難くすることができる。 The glass for an atomic cell and the atomic cell of the present invention can be used, for example, in an atomic oscillator that makes a resonance transition of an alkali metal by utilizing the quantum interference effect of two types of light having different wavelengths. However, it may be used for an atomic oscillator that makes a resonance transition of an alkali metal by utilizing a double resonance phenomenon caused by light and microwave, and is not particularly limited. In either case, it is possible to make it difficult for the oscillation frequency of the atomic oscillator to change with time.
　以下、実施例に基づき本発明を説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples.
　（実施例１～７及び比較例１～２）
　下記の表１に示す実施例１～７及び比較例１～２の原子セル用ガラスを調製した。 (Examples 1 to 7 and Comparative Examples 1 to 2)
Glasses for atomic cells of Examples 1 to 7 and Comparative Examples 1 and 2 shown in Table 1 below were prepared.
　具体的には、まず、下記の表１に示したガラス組成となるように、各種酸化物、炭酸塩等を調合したガラスバッチを用意し、これを白金坩堝に入れ、１４００～１５００℃で６時間溶融した後、溶融ガラスをステンレス製の金型に流し出し成形した。その後、得られたガラスを、６５０℃で1時間保持してアニール処理を行った。 Specifically, first, a glass batch containing various oxides, carbonates, etc. is prepared so as to have the glass composition shown in Table 1 below, and this is placed in a platinum crucible at 1400 to 1500 ° C. 6 After melting for a time, the molten glass was poured into a stainless steel mold and molded. Then, the obtained glass was held at 650 ° C. for 1 hour for annealing treatment.
　その後、アルキメデス法により、得られたガラスの密度を測定した。 After that, the density of the obtained glass was measured by the Archimedes method.
　更に、押し棒式熱膨張係数測定装置を用いて、３０～３００℃の温度範囲の平均熱膨張係数を測定した。 Furthermore, the average coefficient of thermal expansion in the temperature range of 30 to 300 ° C. was measured using a push rod type coefficient of thermal expansion measuring device.
　その後、ガラス組成の式量とガラスの密度から、モル体積を算出した。 After that, the molar volume was calculated from the formula amount of the glass composition and the density of the glass.
　その後、得られたガラスで作製したセル本体の主面上に、得られたガラスで作製した窓部を配置し、セル本体と窓部を陽極接合した。その後、貫通孔内にアルカリ金属を配置した。更に、前述と反対側のセル本体の主面上に、得られたガラスで作製した別の窓部を配置し、セル本体と窓部を陽極接合することで、貫通孔内を封止し、原子セルを作製した。なお、陽極接合は、印加電圧１０００Ｖにより、３２０℃、３００℃、２５０℃で行った。 After that, the window part made of the obtained glass was placed on the main surface of the cell body made of the obtained glass, and the cell body and the window part were anodically bonded. After that, an alkali metal was placed in the through hole. Further, another window portion made of the obtained glass is placed on the main surface of the cell body on the opposite side to the above, and the inside of the through hole is sealed by anodic joining the cell body and the window portion. Atomic cells were made. The anode bonding was performed at 320 ° C., 300 ° C., and 250 ° C. with an applied voltage of 1000 V.
　その後、次のようにして原子セルの気密性を評価した。作製した原子セルの陽極接合の界面に沿って、粘度の低い赤インクを垂らし、接合界面が地表に対し垂直になるように設定した。その後、７２時間経過後に、光学顕微鏡（２００倍）により、接合界面を観察した。接合界面を垂直方向から観察し、赤インクが接合界面の１０％未満の面積に浸透したものを「〇」、１０～９０％未満の面積に浸透したものを「△」、９０～１００％の面積に浸透したものを「×」とした。 After that, the airtightness of the atomic cell was evaluated as follows. A low-viscosity red ink was dripped along the interface of the anode bonding of the prepared atomic cell, and the bonding interface was set to be perpendicular to the ground surface. Then, after 72 hours, the bonding interface was observed with an optical microscope (200 times). Observing the bonding interface from the vertical direction, the red ink permeating the area of less than 10% of the bonding interface is "○", and the area of 10 to less than 90% is "△", 90 to 100%. Those that permeated the area were designated as "x".
　その後、作製した原子セルを用い、Ｈｅガスの遮蔽性を評価した。１０５ａｔｏｍｓ／ｃｍ・ｓ・ａｔｏｍｓがＨｅガスの透過率の検出限界であり、検出限界以下であれば、Ｈｅガスの遮蔽性が高いことが担保される。なお、Ｈｅガスの透過性の評価は、ガスクロマトグラフィーを用いて３０℃で測定した。 Then, the prepared atomic cell was used to evaluate the shielding property of He gas. 10 5 atoms / cm · s · atoms is the detection limit of the transmittance of the He gas, equal to or less than the detection limit, it is ensured a high shielding property of the He gas. The evaluation of the permeability of He gas was measured at 30 ° C. using gas chromatography.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１より、実施例１～７のガラスは、モル体積が２６．０ｃｍ３／モル以下であり、ヘリウム透過率が１０５ａｔｏｍ／ｃｍ・ｓ・ａｔｏｍｓ以下であったため、Ｈｅガスの遮蔽性が優れていた。一方、比較例１～２のガラスは、モル体積が２６．０ｃｍ３／モルを超過し、ヘリウム透過率が１０５ａｔｏｍ／ｃｍ・ｓ・ａｔｏｍｓを超過したため、Ｈｅガスの遮蔽性が不良だった。 From Table 1, the glasses of Examples 1 to 7 is the molar volume of 26.0cm 3 / mol or less, the helium permeability was 10 5 atom / cm · s · atoms or less, shielding of the He gas It was excellent. On the other hand, the glasses of Comparative Examples 1-2, the molar volume exceeded 26.0cm 3 / mol, since the helium transmittance exceeds the 10 5 atom / cm · s · atoms, shielding of the He gas was poor ..
　従って、実施例１～７のガラスを用いた場合、高いＨｅガス遮蔽性により、原子発振器における発振周波数の経時変化を生じ難い原子セルを得ることが確認できた。 Therefore, when the glass of Examples 1 to 7 was used, it was confirmed that an atomic cell in which the oscillation frequency of the atomic oscillator is unlikely to change with time can be obtained due to the high He gas shielding property.
１…原子セル
１ａ…入光面
１ｂ…出光面
２…セル本体
２ａ…第１の主面
２ｂ…第２の主面
３…第１の窓部
４…第２の窓部
５…貫通孔
  1 ... Atomic cell 1a ... Incoming surface 1b ... Emitting surface 2 ... Cell body 2a ... First main surface 2b ... Second main surface 3 ... First window 4 ... Second window 5 ... Through hole

Claims (14)

  1. 　モル体積が２６．０ｃｍ３／モル以下である原子セル用ガラス。 Glass for atomic cells having a molar volume of 26.0 cm 3 / mol or less.
  2. 　ガラス組成として、質量％で、Ｌｉ２Ｏ　０．５％～１０％を含有する、請求項１に記載の原子セル用ガラス。 As a glass composition, in mass%, containing Li 2 O 0.5% ~ 10% , atomic cell glass of claim 1.
  3. 　ガラス組成として、質量％で、ＳｉＯ２　５０％～７０％、Ａｌ２Ｏ３　１０％～３０％、ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ　９～３０％、Ｌｉ２Ｏ　０．５％～１０％、Ｎａ２Ｏ　０～３％、Ｂ２Ｏ３　０～３％を含有する、請求項１又は２に記載の原子セル用ガラス。 As the glass composition, in terms of mass%, SiO 2 50% to 70%, Al 2 O 3 10% to 30%, MgO + CaO + SrO + BaO 9 to 30%, Li 2 O 0.5% to 10%, Na 2 O 0 to 3%. , B 2 O 30 to 3%, the glass for an atomic cell according to claim 1 or 2.
  4. 　ＭｇＯ＋ＣａＯを９～３０質量％を含む、請求項３に記載の原子セル用ガラス。 The glass for an atomic cell according to claim 3, which contains 9 to 30% by mass of MgO + CaO.
  5. 　質量比で、ＣａＯ／ＭｇＯが１．０以下である、請求項３又は４のいずれか１項に記載の原子セル用ガラス。 The glass for an atomic cell according to any one of claims 3 or 4, wherein CaO / MgO is 1.0 or less in terms of mass ratio.
  6. 　実質的にＢ２Ｏ３を含有しない、請求項１～５のいずれか１項に記載の原子セル用ガラス。 The glass for an atomic cell according to any one of claims 1 to 5, which does not substantially contain B 2 O 3.
  7. 　実質的にＰ２Ｏ５を含有しない、請求項１～６のいずれか１項に記載の原子セル用ガラス。 The glass for an atomic cell according to any one of claims 1 to 6, which does not substantially contain P 2 O 5.
  8. 　実質的にＮａ２Ｏを含有しない、請求項１～７のいずれか１項に記載の原子セル用ガラス。 The glass for an atomic cell according to any one of claims 1 to 7, which contains substantially no Na 2 O.
  9. 　対向している第１の主面及び第２の主面を有し、前記第１の主面及び前記第２の主面間を貫通している貫通孔が設けられている、セル本体と、
    　前記セル本体の第１の主面上に設けられており、前記貫通孔の一方側を塞いでいる第１の窓部と、
    　前記セル本体の第２の主面上に設けられており、前記貫通孔の他方側を塞いでいる第２の窓部と、
    を備え、
    　前記第１の窓部及び前記第２の窓部が、請求項１～８のいずれか１項に記載の原子セル用ガラスにより構成されている、原子セル。     A cell body having a first main surface and a second main surface facing each other and provided with a through hole penetrating between the first main surface and the second main surface.
    A first window portion provided on the first main surface of the cell body and closing one side of the through hole, and a first window portion.
    A second window portion provided on the second main surface of the cell body and blocking the other side of the through hole, and a second window portion.
    Equipped with
    An atomic cell in which the first window portion and the second window portion are made of the glass for an atomic cell according to any one of claims 1 to 8.
  10. 　前記原子セル用ガラスが、前記原子セルの入光面及び出光面のうち少なくとも一方を構成している、請求項９に記載の原子セル。 The atomic cell according to claim 9, wherein the glass for an atomic cell constitutes at least one of an incoming light surface and an outgoing light surface of the atomic cell.
  11. 　前記セル本体が、ガラスにより構成されている、請求項９又は１０に記載の原子セル。 The atomic cell according to claim 9 or 10, wherein the cell body is made of glass.
  12. 　前記セル本体、前記第１の窓部及び前記第２の窓部が、実質的に同じガラス組成を有する、請求項９～１１のいずれか１項に記載の原子セル。 The atomic cell according to any one of claims 9 to 11, wherein the cell body, the first window portion, and the second window portion have substantially the same glass composition.
  13. 　請求項９～１２のいずれか１項に記載の原子セルの製造方法であって、
    　前記第１の窓部を前記セル本体の前記第１の主面上に配置し、前記セル本体と前記第１の窓部とを接合する工程と、
    　前記貫通孔内にアルカリ金属を配置する工程と、
    　前記第２の窓部を前記セル本体の前記第２の主面上に配置し、前記セル本体と前記第２の窓部とを接合し、前記貫通孔内を封止する工程と、
    を備える、原子セルの製造方法。     The method for producing an atomic cell according to any one of claims 9 to 12.
    A step of arranging the first window portion on the first main surface of the cell body and joining the cell body and the first window portion.
    The step of arranging the alkali metal in the through hole and
    A step of arranging the second window portion on the second main surface of the cell body, joining the cell body and the second window portion, and sealing the inside of the through hole.
    A method for manufacturing an atomic cell.
  14. 　前記セル本体と前記第１の窓部とを陽極接合法で接合し、且つ前記セル本体と前記第２の窓部とを陽極接合法により接合する、請求項１３に記載の原子セルの製造方法。
          The method for manufacturing an atomic cell according to claim 13, wherein the cell body and the first window portion are joined by an anode joining method, and the cell body and the second window portion are joined by an anode joining method. ..
PCT/JP2021/018704 2020-06-04 2021-05-18 Glass for atomic cells, atomic cell, and method for manufacturing atomic cell WO2021246150A1 (en)

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JPH05193980A (en) * 1991-08-12 1993-08-03 Corning Inc Flat panel display device containing borosilicate glass rich in alumina and alkal earth metal
JPH06204586A (en) * 1992-07-17 1994-07-22 Ball Corp Atomic frequency reference cell and its manufacture
JP2015215502A (en) * 2014-05-12 2015-12-03 日本電気硝子株式会社 Glass cell, liquid crystal device, and manufacturing method of these
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