A low permeability and long life alkali metal atom gas chamber and preparation method thereof

Abstract

The present application relates to the field of atomic gas chambers, and specifically discloses a low-permeability, long-life alkali metal atomic gas chamber and a preparation method thereof. The alkali metal atomic gas chamber comprises: a transparent outer shell, surrounding a main chamber forming the alkali metal atomic gas chamber; a barrier film layer, coated on the inner wall of the transparent outer shell, and the barrier film layer comprises an Al2O3 film or an AlN film. The solution provided in the present application can effectively reduce the loss of alkali metal atoms and the penetration of small molecule gases without affecting the light transmission performance of the atomic gas chamber itself, thereby extending the service life of the atomic gas chamber. At the same time, the solution can effectively isolate inert gases or alkali metal atoms from paramagnetic impurities in the glass surface area, and reduce the relaxation caused by paramagnetic impurities. It also reduces the adverse effects caused by chemical reactions between impurity ions in the glass substrate and gaseous working substances, thereby improving the reliability of the atomic gas chamber. In addition, the solution can increase the thermal conductivity of the atomic gas chamber shell and improve its internal temperature uniformity.

Description

Technical Field

[0001] The present application relates to the technical field of atomic gas chamber preparation, and in particular to a low-permeability and long-life alkali metal atomic gas chamber and a preparation method thereof. Background Art

[0002] The atomic gas chamber is a device for preparing the polarized state of alkali metal atoms. It stores atomic vapor in a confined space and uses pump lasers to effectively control the quantum state of alkali metal atoms. The atomic gas chamber is the core physical device of instruments such as atomic gyroscopes, atomic clocks, and atomic magnetometers. Its performance directly determines the upper limit of the performance of atomic instruments.

[0003] The main factors affecting the life of the atomic gas chamber are the loss of alkali metal atoms and the penetration of small molecule gases. The loss of alkali metal atoms in the atomic gas chamber is mainly due to two reasons: one is the chemical reaction of alkali metal atoms with impurities in the gas chamber, and the other is the physical diffusion of alkali metal atoms to the inner wall of the glass. The consumption caused by chemical reaction can be completed in a short period of time, and this part of the loss can be reduced by improving the cleanliness of the inner wall of the atomic gas chamber. The physical diffusion of alkali metal atoms to the inner wall of the glass exists for a long time during the entire life of the atomic gas chamber, and is also the main cause of alkali metal loss. The melting point of alkali metal atoms is low, the melting point of cesium atoms is about 28.5℃, and the melting point of rubidium atoms is about 38.9℃. They are liquid in the working state of the atomic gas chamber. There is a risk of alkali metal droplets covering the light-transmitting window when excessively filling alkali metals to maintain the life of the atomic gas chamber. In addition, the change of gas composition in the atomic gas chamber is a key factor affecting the long-term performance indicators of the instrument, among which the penetration of small molecule gases such as helium and hydrogen into and out of the atomic gas chamber is the main cause of the change in gas composition. Therefore, a coating material for the inner wall of the atomic gas chamber is needed to block the migration of alkali metal atoms to the glass shell and the penetration of gas molecules into and out of the atomic gas chamber, thereby reducing the loss of alkali metal atoms and the change of gas composition.

[0004] When the atomic gas chamber is working, the gaseous atoms have violent thermal motion, which leads to the loss of atomic macroscopic spin. Among them, the spin loss caused by wall relaxation has become increasingly prominent under the development trend of miniaturization. In order to overcome wall relaxation, the buffer gas method and the inner wall coating method are often used. In comparison, the inner wall coating method does not have the pressure broadening caused by the buffer gas, and the light width of the atomic transition will also become narrower. A larger signal can be obtained using a lower power laser. At present, the more mature inner wall coating material is paraffin, and its melting point is generally 60-80°C. In applications that require higher atomic density, such as atomic gyroscopes, paraffin coating is no longer applicable. Another common type is silicon-based organic matter, represented by octadecyltrichlorosilane (OTS), which can withstand an operating temperature of about 170°C, but its coating effect is unstable. Summary of the invention

[0005] The present application provides a low-permeability, long-life alkali metal atomic gas chamber and a preparation method thereof. Through the inner wall coating technology of the atomic gas chamber, the service life of the atomic gas chamber is extended and the anti-relaxation, temperature uniformity and other properties are improved without affecting the light transmission performance of the atomic gas chamber itself.

[0006] In a first aspect, an alkali metal atom gas chamber is provided, comprising:

[0007] A transparent shell surrounding a main chamber forming the alkali metal atom gas chamber;

[0008] The barrier film layer is coated on the inner wall of the transparent shell, and the barrier film layer includes an Al2O3 film or an AlN film.

[0009] Compared with the prior art, the solution provided by this application includes at least the following beneficial technical effects:

[0010] (1) The barrier film layer described in this solution can effectively block the migration of alkali metal atoms to the inner wall of the atomic gas chamber, reduce the loss of alkali metal atoms, and thus extend the service life of the atomic gas chamber;

[0011] (2) The barrier film layer described in this solution can effectively reduce the penetration of small molecule gases, such as helium and hydrogen, thereby improving the long-term performance stability of the atomic gas chamber;

[0012] (3) The barrier film layer described in this solution can effectively isolate the inert gas or alkali metal atoms from the paramagnetic impurities in the glass surface area, reduce the relaxation caused by the paramagnetic impurities, and improve the performance of the atomic gas chamber;

[0013] (4) The barrier film layer described in this solution has excellent thermal conductivity, which can improve the temperature uniformity inside the atomic gas chamber, thereby improving the performance of the atomic gas chamber.

[0014] In some embodiments, the process for preparing Al2O3 film is relatively more flexible compared to AlN film.

[0015] In some embodiments, compared with the Al2O3 film, the thermal conductivity of the AlN film is relatively superior, which can further improve the temperature uniformity inside the atomic gas chamber, thereby improving the performance of the atomic gas chamber.

[0016] In combination with the first aspect, in some implementations of the first aspect, the barrier film layer includes a surface film layer and a transition film layer, and the transition film layer is located between the surface film layer and the transparent outer shell.

[0017] The barrier film layer described in this solution can optimize the matching degree with the substrate by adjusting the parameters of the transition film layer, so that it has the ability to work at high temperatures.

[0018] In combination with the first aspect, in certain implementations of the first aspect, the total thickness of the transition film layer accounts for 30%-60% of the thickness of the barrier film layer.

[0019] The appropriate thickness of the transition film layer is conducive to flexible adjustment of the performance of the barrier film layer described in this scheme, so that the barrier film layer described in this scheme is stably combined with the inner wall of the atomic gas chamber, and the loss of alkali metal atoms is effectively reduced, thereby effectively extending the service life of the atomic gas chamber.

[0020] In combination with the first aspect, in certain implementations of the first aspect, the surface film layer is an Al2O3 film, and the transition film layer is an xSiO2﹒yAl2O3 film.

[0021] The shell material is glass material, and the matching degree between the Al2O3 film and the substrate can be optimized through the xSiO2﹒yAl2O3 film.

[0022] In combination with the first aspect, in some implementations of the first aspect, x=0.2-0.8, y=1-x.

[0023] In combination with the first aspect, in certain implementations of the first aspect, the surface film layer is an AlN film, and the transition film layer is a Si3N4 film.

[0024] The shell material is glass material, and the matching degree between the AlN film and the substrate can be optimized through the Si3N4 film.

[0025] In combination with the first aspect, in certain implementations of the first aspect, the thickness of the barrier film layer is 6 nm to 2 μm.

[0026] This ensures low permeability and high optical transmittance of the barrier film layer.

[0027] In a second aspect, a method for preparing an alkali metal atom gas chamber is provided, comprising:

[0028] preparing a transparent shell of the atomic gas cell to form a main chamber and a gas-filled branch pipe of the alkali metal atomic gas cell;

[0029] Coating a barrier film layer on the inner wall of the transparent shell, wherein the barrier film layer comprises an Al2O3 film or an AlN film;

[0030] heating the transparent shell and extracting the air in the transparent shell;

[0031] One or more alkali metals are introduced into the transparent outer shell, and the alkali metal atoms are diffused into the main chamber by distillation, and the transparent outer shell is cooled so that the alkali metal atoms condense in the main chamber;

[0032] The transparent shell is melted at the gas-filled branch pipe, and is placed in a vacuum oven for low-temperature baking to mature the shell, thereby preparing an alkali metal atom gas chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic structural diagram of an alkali metal atom gas chamber provided in an embodiment of the present application.

[0034] Figure 2 A schematic flow chart of a method for preparing an alkali metal atom gas chamber provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 It is a schematic structural diagram of an alkali metal atom gas chamber provided in an embodiment of the present application. Figure 1 The alkali metal atom gas cell shown may have the characteristics of low permeability and long life.

[0037] The alkali metal atom gas chamber may have a main chamber 1, and the main chamber 1 may be formed by surrounding a transparent shell 3 of the alkali metal atom gas chamber. A through hole is left on the top surface of the main chamber 1 for connecting with the inflation branch pipe 2. The transparent shell 3 is made of a material with high light transmittance, such as quartz glass, borosilicate glass (such as borosilicate 3.3 glass), etc. The inner wall of the transparent shell 3 is coated with a barrier film layer 8. The barrier film layer 8 is a barrier film layer. The barrier film layer 8 has light transmittance, density, non-magneticity, and high temperature resistance. The barrier film layer 8 is coated on the inner wall of the transparent shell 3 of the alkali metal atom gas chamber, for example, by atomic layer deposition technology, sol-gel technology, and the like.

[0038] In some embodiments, to ensure low permeability, the thickness of the barrier film layer 8 is generally not less than 6 nm.

[0039] In some embodiments, in order to ensure the optical transmittance of the transparent shell 3 of the atomic gas chamber, the thickness of the barrier film layer 8 is generally not greater than 2 μm.

[0040] In some embodiments, the barrier film layer 8 may be an Al 2 O 3 film or an AlN film.

[0041] In other embodiments, the barrier film layer 8 may include multiple film layers, the film layer of the barrier film layer 8 that is farthest from the transparent housing 3 is the surface film layer 5, and one or more transition film layers 4 may be provided between the surface film layer 5 and the transparent housing 3. The total thickness of the transition film layer 4 accounts for 30%-60% of the thickness of the barrier film layer 8.

[0042] In one embodiment, the surface film layer 5 of the barrier film layer 8 may be an Al2O3 film, and the transition film layer 4 of the barrier film layer 8 may be an xSiO2﹒yAl2O3 film, where x=0.2-0.8 and y=1-x. In one possible case, the thickness of the xSiO2﹒yAl2O3 film and the Al2O3 film are both 20 nm.

[0043] In another embodiment, the surface film layer 5 of the barrier film layer 8 may be an AlN film, and the transition film layer 4 of the barrier film layer 8 may be a Si3N4 film. In a possible case, the thickness of the Si3N4 film is 100 nm, and the thickness of the AlN film is 150 nm.

[0044] Figure 2 It is a schematic flow chart of a method for preparing an alkali metal atom gas chamber provided in an embodiment of the present application.

[0045] (1) A transparent shell 3 of the atomic gas cell is prepared to form the main chamber 1 and the inflation branch pipe 2 of the alkali metal atomic gas cell.

[0046] The atomic gas chamber transparent shell 3 can be prepared by flame welding, laser welding, optical bonding or glass bonding.

[0047] (2) Pretreatment of the atomic gas chamber transparent shell 3 before coating.

[0048] Pretreatment before coating mainly includes annealing, cleaning and baking. In one embodiment, the atomic gas chamber transparent shell 3 is placed in a vacuum annealing furnace for annealing to eliminate the stress introduced by the thermal processing process; then, the atomic gas chamber transparent shell 3 is ultrasonically cleaned with organic reagents (such as acetone, ethanol, etc.), acidic reagents, and deionized water in turn to remove impurities attached to the inner wall; finally, the cleaned atomic gas chamber transparent shell 3 is placed in a vacuum oven, the baking temperature is 200°C, and the baking time is 20 hours.

[0049] (3) A barrier film layer 8 is coated on the inner wall of the transparent shell 3 of the atomic gas chamber.

[0050] In one embodiment, the inner surface of the atomic gas chamber transparent shell 3 is uniformly covered with a dense 0.4SiO2﹒0.6Al2O3 transition film 4 with a deposition thickness of 20nm by using atomic layer deposition technology. A layer of Al2O3 film is further deposited on the transition film 4 with a deposition thickness of 20nm.

[0051] In another embodiment, a barrier film layer 8 is coated on the inner wall of the atomic gas chamber, and the main processes include solution preparation, film coating, low temperature curing, and high temperature curing. First, Si3N4 sol and AlN sol are prepared; then, a Si3N4 transition film layer with a thickness of 100nm is uniformly coated on the inner surface of the transparent shell 3 of the atomic gas chamber by the sol-gel method, and after low temperature curing, a layer of AlN film with a thickness of 150nm is continuously coated on the transition film layer 4, and low temperature curing is performed; after the barrier film layer 8 is coated, high temperature curing is performed to form a dense transparent film on the inner wall of the transparent shell 3 of the atomic gas chamber.

[0052] (4) Connecting the atomic gas chamber transparent shell 3 coated with the inner wall barrier film layer 8 to the vacuum system, heating the atomic gas chamber transparent shell 3 at high temperature, and extracting the air in the atomic gas chamber transparent shell 3 by using the vacuum system.

[0053] Preferably, the heating temperature is 250-400° C. and the heating time is 20 hours.

[0054] (5) introducing one or more alkali metals into the atomic gas chamber transparent shell 3, and using a distillation method to diffuse the atoms in the alkali metal source into the main chamber 1 of the atomic gas chamber transparent shell 3, and at the same time cooling the main chamber 1 of the atomic gas chamber transparent shell 3, so that the alkali metal atoms condense in the main chamber 1 of the atomic gas chamber transparent shell 3.

[0055] Preferably, the hot end temperature is 200° C., and the cold end temperature is 5° C. The alkali metal filling amount inside the atomic gas chamber can be controlled by controlling the alkali metal content in the alkali metal source and the distillation time.

[0056] (6) If the atomic gas chamber is not required to contain working gas, proceed to step (7); if the atomic gas chamber is required to contain working gas with a pressure reaching a set pressure value P, one or more inert gases are introduced into the main chamber 1 of the transparent shell 3 of the atomic gas chamber so that the pressure in the transparent shell 3 of the atomic gas chamber reaches the set pressure value P.

[0057] (7) The transparent shell 3 of the atomic gas chamber is removed from the vacuum system, and placed in a vacuum oven for low-temperature baking to mature it, thereby preparing a long-life alkali metal atomic gas chamber with an inner wall coated with a barrier film layer 8.

[0058] Specifically, the atomic gas chamber filled with the working substance is sealed and fused at the gas filling branch pipe 2, and then placed in a vacuum oven for low-temperature baking to mature it, and finally a long-life alkali metal atomic gas chamber with a barrier film layer 8 coated on the inner wall is prepared.

[0059] Through the above-mentioned scheme, the preparation of the atomic gas chamber coated with the inner wall barrier film layer 8 can be realized.

[0060] Although the present application is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present application. Any technical personnel in this field may make possible changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

Claims

1. A method for preparing an alkali metal atom gas cell, characterized in that: include: A transparent shell of the atomic gas chamber is prepared to form a main chamber and a gas-filled branch pipe of the alkali metal atomic gas chamber. The shell of the atomic gas chamber is made of a material with high light transmittance, including quartz glass and borosilicate glass. Perform pre-coating pretreatment on the transparent shell of the atomic gas cell, including annealing, cleaning and vacuum baking; Coating a barrier film layer on the inner wall of the transparent shell, wherein the barrier film layer comprises an Al2O3 film or an AlN film; The transparent outer shell is heated and the air in the transparent outer shell is extracted, the heating temperature is 250-400° C.; one or more alkali metals are filled into the transparent outer shell, and the alkali metal atoms are diffused into the main chamber by distillation, and the transparent outer shell is cooled at the same time, so that the alkali metal atoms condense in the main chamber; The transparent shell is melted at the gas-filled branch pipe, and is placed in a vacuum oven for low-temperature baking to mature the shell, thereby preparing an alkali metal atom gas chamber.

2. The preparation method according to claim 1, characterized in that: The barrier film layer comprises a surface film layer and a transition film layer, and the transition film layer is located between the surface film layer and the transparent shell.

3. The preparation method according to claim 2, characterized in that: The total thickness of the transition film layer accounts for 30%-60% of the thickness of the barrier film layer.

4. The preparation method according to claim 2 or 3, characterized in that: The surface film layer is an Al2O3 film, and the transition film layer is an xSiO2﹒yAl2O3 film.

5. The preparation method according to claim 4, characterized in that: x=0.2-0.8, y=1-x.

6. The preparation method according to claim 2 or 3, characterized in that: The surface film layer is an AlN film, and the transition film layer is a Si3N4 film.

7. The preparation method according to claim 1, characterized in that: The thickness of the barrier film layer is 6 nm to 2 μm.

8. The preparation method according to claim 1, characterized in that: The coating methods used include: atomic layer deposition scheme and sol-gel scheme.

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