A polarization 3 Preparation method of glass material for He neutron spin filter gas chamber

Abstract

This invention discloses a polarization 3 The preparation method of glass material for the gas chamber of He neutron spin filter includes the following steps: (1) mix barium oxide, aluminum oxide, silicon oxide and titanium oxide, place them in a quartz crucible, and melt them at 1600~1800℃ for 10~24h in a chlorine atmosphere to obtain liquid glass; wherein, barium oxide, aluminum oxide, silicon oxide and titanium oxide are mixed in the following mass percentages: 30~40% barium oxide, 10~15% aluminum oxide, 50~60wt% silicon oxide and 0~2% titanium oxide; (2) blow the liquid glass into a molded gas chamber, and then anneal the molded gas chamber in a chlorine-rich atmosphere; (3) after annealing, use supercritical CO2 fluid to clean the gas chamber cavity, and after cleaning, fill it with N2O gas, and under ultraviolet light irradiation, form a passivated surface on the glass surface to obtain a glass gas chamber. The method of this invention, through specific component and process design, can construct a dense, uniform glass network with extremely low magnetic impurities at the molecular scale, thereby simultaneously improving the airtightness of the glass material and reducing its magnetization relaxation, so that the neutron transmittance of the glass material can reach more than 95%@4.5Å.

Description

Technical Field

[0001] This invention relates to a polarization 3 Preparation method of glass material for He neutron spin filter gas chamber. Background Technology

[0002] polarization 3 The main body of the He neutron spin filter is a structure filled with polarized... 3 In the precision glass chamber for He gas, the properties of the glass material directly affect the efficiency, stability, and service life of the entire system.

[0003] Traditional glass cells utilize materials such as quartz glass and high-alumina silicate glass (e.g., GE180), which possess good mechanical strength, chemical stability, and relatively high neutron transmittance. However, with ever-increasing demands for measurement accuracy and efficiency, the intrinsic limitations of these traditional materials are becoming increasingly apparent. Existing glass materials used to form glass cells are not completely static media; the relaxation behavior of their microstructure during molding and processing has a crucial impact on the performance of the final device. During the hot processing of glass cells, such as blowing and sealing, traditional glass networks are prone to non-uniform relaxation of the microstructure, manifesting as excessively large over-relaxation factors. This structural instability is directly "imprinted" inside the cell, becoming... 3 The primary site of spin depolarization in He atoms is manifested in a shortened relaxation time and a decrease in overall polarization efficiency. Furthermore, necessary processes such as secondary blowing during glass cell formation introduce uncontrollable differences in thermal history, resulting in variations in the glass network microstructure across different parts of the cell, further exacerbating polarization. 3 Fluctuations and degradation in the performance of He neutron spin filters. Existing glass materials for gas chambers include high-alumina silicate glass and commercially available glass materials. When using these glass materials, there are problems such as shortened relaxation time and decreased overall polarization efficiency. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a polarization 3 A method for preparing glass materials for neutron spin filter gas chambers: This method, through specific composition and process design, can construct a dense, uniform glass network with extremely low magnetic impurities at the molecular scale, thereby simultaneously improving the airtightness and reducing the magnetization relaxation of the glass material, extending the relaxation time of the glass material to more than 300 hours, and achieving a neutron transmittance of more than 95%@4.5Å.

[0005] Technical solution: The polarization described in this invention 3 The preparation method of glass material for the gas chamber of a He neutron spin filter includes the following steps:

[0006] (1) Barium oxide, aluminum oxide, silicon oxide and titanium oxide are mixed and placed in a high-purity quartz crucible. The mixture is then melted at 1600~1800℃ for 10~24h in a chlorine-containing atmosphere (a chlorine-containing atmosphere refers to a gas atmosphere in which chlorine gas is added to the air environment and the volume fraction of chlorine gas does not exceed 5%) to obtain liquid glass. The barium oxide, aluminum oxide, silicon oxide and titanium oxide are mixed in the following mass percentages: 30~40% barium oxide, 10~15% aluminum oxide, 50~60% silicon oxide and 0~2% titanium oxide.

[0007] (2) The homogenized liquid glass is injected into a mold with ultra-high precision inner surface polishing, and molding is performed above the glass transition temperature to form a forming air chamber with a smooth inner surface; or the liquid glass is manually blown to obtain a forming air chamber.

[0008] (3) Place the forming chamber in an annealing furnace filled with dry Cl2 / Ar gas and anneal it at 700~900℃ (below the annealing point). This process can passivate the dangling bonds on the surface, reduce the unpaired paramagnetic electron centers, and eliminate stress without damaging the surface finish.

[0009] (4) The chamber is cleaned with supercritical CO2 fluid to thoroughly remove organic pollutants. Then, 80-100 mbar of N2O gas is introduced. Under ultraviolet light irradiation, N2O decomposes on the glass surface to generate active oxygen atoms, which further passivates the surface (active oxygen reacts with Si-OH, dangling bonds, and defects on the glass surface to generate a dense, stable, and chemically inert surface layer), thus obtaining the glass chamber. This invention combines a two-step method of supercritical CO2 cleaning and ultraviolet photocatalytic N2O decomposition. Without damaging the surface finish, it achieves thorough removal of organic pollutants in the chamber and passivation of active oxygen from dangling bonds on the surface, forming a stable, clean, and low-defect final surface state.

[0010] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0011] (1) The present invention can convert magnetic metal impurities such as iron into volatile chlorides (such as FeCl3) by high-temperature melting in a chlorine atmosphere and remove them. Combined with chlorine-rich annealing, the surface defects are further passivated, thereby reducing the magnetic impurities and paramagnetic centers of the glass material from the source and the surface, and improving the intrinsic properties of the glass material.

[0012] (2) By combining BaO, Al2O3, SiO2 and TiO2 in a specific mixing ratio and using specific processing methods, this invention can construct a dense, uniform glass network with extremely low magnetic impurities at the molecular scale, thereby simultaneously improving the airtightness of the glass material and reducing its magnetization relaxation. This allows the relaxation time of the glass material to be extended to more than 300 hours, and the neutron transmittance to be more than 95%@4.5Å (the transmittance of neutrons at a wavelength of 4.5Å is more than 90% at a thickness of 2 mm). Moreover, its high airtightness can meet the experimental requirements of polarized neutrons. Attached Figure Description

[0013] Figure 1 The graph shows the test results of the neutron transmittance of the glass material prepared in Example 1 of the present invention. Detailed Implementation

[0014] Example 1

[0015] The method for preparing glass materials for gas chambers according to the present invention uses 99wt% industrial-grade BaCO3, 99wt% industrial-grade SiO2, 99wt% industrial-grade TiO2, and 99wt% industrial-grade Al2O3 as raw materials, and specifically includes the following steps:

[0016] (1) Add barium oxide, aluminum oxide, silicon oxide and titanium oxide to a mixer in the following mass percentages and mix: 35% barium oxide, 12.5% ​​aluminum oxide, 52% silicon oxide and 0.5% titanium oxide; after mixing evenly, glass raw material is obtained;

[0017] (2) Add the glass raw material obtained in step (1) into a quartz crucible and heat it to 1800°C in a chlorine atmosphere (chlorine volume fraction of 3%). Keep it at the high temperature for 15 hours and stir it with a quartz rod until it becomes clear and homogenized to obtain liquid glass.

[0018] (3) The liquid glass obtained in step (2) is drawn into the mold and blown and drawn to obtain the forming air chamber;

[0019] (4) Place the molding chamber from step (3) in an annealing furnace filled with dry Cl2 / Ar (chlorine volume fraction of 10%) and anneal it at 800°C for 0.5 h.

[0020] (5) After annealing, the cavity of the gas chamber is cleaned with supercritical CO2 fluid (60 mL / min) (pressure 15 MPa) to completely remove organic pollutants. Then, 80 mbar N2O gas is introduced and irradiated with a low-pressure ultraviolet mercury lamp for 10 min. After the surface of the gas chamber is passivated, a glass gas chamber is obtained.

[0021] Example 2

[0022] The preparation method of Example 2 is the same as that of Example 1, except that: in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to the mixer in the following mass percentages: 34.5% barium oxide, 15% aluminum oxide, 50% silicon oxide and 0.5% titanium oxide; after mixing evenly, glass raw material is obtained; in step (2), it is heated to 1600°C in a chlorine atmosphere (chlorine volume fraction is 3%) and kept at high temperature for 24 hours; in step (5), 100mbar N2O gas is introduced and irradiated with a low-pressure ultraviolet mercury lamp for 5 minutes. After the surface of the gas chamber is passivated, the glass gas chamber is finally obtained.

[0023] Example 3

[0024] The preparation method of Example 3 is the same as that of Example 1, except that: in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to the mixer in the following mass percentages: 33% barium oxide, 10% aluminum oxide, 56.5% silicon oxide and 0.5% titanium oxide; after mixing evenly, glass raw material is obtained; in step (2), it is heated to 1800°C in a chlorine atmosphere (chlorine volume fraction is 3%) and kept at high temperature for 10 hours; in step (5), 80 mbar N2O gas is introduced and irradiated with a low-pressure ultraviolet mercury lamp for 8 minutes. After the surface of the gas chamber is passivated, the glass gas chamber is finally obtained.

[0025] Example 4

[0026] The preparation method of Example 4 is the same as that of Example 1, except that: in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to a mixer in the following mass percentages and mixed: 32% barium oxide, 13% aluminum oxide, 54.5% silicon oxide and 0.5% titanium oxide; after mixing evenly, glass raw materials are obtained; in step (2), the mixture is heated to 1750°C in a chlorine atmosphere (chlorine volume fraction is 3%) and kept at the high temperature for 12 hours; finally, a glass gas chamber is obtained.

[0027] Example 5

[0028] The preparation method of Example 5 is the same as that of Example 1, except that: in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to the mixer in the following mass percentages: 30% barium oxide, 10% aluminum oxide, 59.7% silicon oxide and 0.3% titanium oxide; after mixing evenly, glass raw materials are obtained; in step (2), the mixture is heated to 1650°C in a chlorine atmosphere (chlorine volume fraction is 1%) and kept at the high temperature for 18 hours; finally, a glass gas chamber is obtained.

[0029] Example 6

[0030] The preparation method of Example 6 is the same as that of Example 1, except that: in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to the mixer in the following mass percentages: 37% barium oxide, 11.5% aluminum oxide, 51% silicon oxide and 0.5% titanium oxide; after mixing evenly, glass raw material is obtained; in step (2), it is heated to 1800°C in a chlorine atmosphere (chlorine volume fraction is 1.5%) and kept at the high temperature for 10 hours; in step (5), 100 mbar of N2O gas is introduced; finally, a glass gas chamber is obtained.

[0031] Example 7

[0032] The preparation method of Example 7 is the same as that of Example 1, except that: in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to the mixer in the following mass percentages: 38% barium oxide, 10% aluminum oxide, 50% silicon oxide and 2% titanium oxide; after mixing evenly, glass raw material is obtained; in step (2), it is heated to 1650°C in a chlorine atmosphere (chlorine volume fraction is 3%) and kept at the high temperature for 24 hours; in step (5), 100 mbar N2O gas is introduced and irradiated with a low-pressure ultraviolet mercury lamp for 8 minutes. After the surface of the gas chamber is passivated, the glass gas chamber is finally obtained.

[0033] Example 8

[0034] The preparation method of Example 8 is the same as that of Example 1, except that: in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to the mixer in the following mass percentages: 37.5% barium oxide, 12% aluminum oxide, 50% silicon oxide and 0.5% titanium oxide; after mixing evenly, glass raw material is obtained; in step (2), it is heated to 1700°C in a chlorine atmosphere (chlorine volume fraction is 2%) and kept at the high temperature for 20 hours; in step (5), 100 mbar of N2O gas is introduced; finally, a glass gas chamber is obtained.

[0035] Example 9

[0036] The preparation method of Example 9 is the same as that of Example 1, except that: in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to the mixer in the following mass percentages: 32% barium oxide, 10% aluminum oxide, 57% silicon oxide and 1% titanium oxide; after mixing evenly, glass raw material is obtained; in step (2), it is heated to 1600°C in a chlorine atmosphere (chlorine volume fraction is 1.5%) and kept at the high temperature for 24 hours; in step (5), 100 mbar of N2O gas is introduced; finally, a glass gas chamber is obtained.

[0037] Example 10

[0038] The preparation method of Example 10 is the same as that of Example 1, except that: in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to the mixer in the following mass percentages: 40% barium oxide, 10% aluminum oxide, 50% silicon oxide and 0% titanium oxide; after mixing evenly, glass raw material is obtained; in step (2), it is heated to 1800°C in a chlorine atmosphere (chlorine volume fraction is 3%) and kept at the high temperature for 10 hours; in step (5), 100 mbar of N2O gas is introduced; finally, a glass gas chamber is obtained.

[0039] The properties of the glass materials for gas chambers prepared in Examples 1-10 are shown in Table 1.

[0040] Table 1

[0041]

[0042] As shown in Table 1, the glass material prepared by this invention with a neutron transmittance of not less than 95%@4.5Å can meet the polarization requirements. 3 The application requirements of high-airtightness glass gas chambers for He neutron spin filters.

[0043] Comparative Example 1

[0044] The preparation method of Comparative Example 1 is the same as that of Example 1, except that in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to the mixer in the following mass percentages: 32% barium oxide, 18% aluminum oxide, 50% silicon oxide and 0% titanium oxide; finally, a glass gas chamber is obtained.

[0045] Comparative Example 2

[0046] The preparation method of Comparative Example 2 is the same as that of Example 1, except that in step (1), barium oxide, aluminum oxide, silicon oxide and titanium oxide are added to the mixer in the following mass percentages: 35% barium oxide, 10% aluminum oxide, 52% silicon oxide and 3% titanium oxide; finally, a glass gas chamber is obtained.

[0047] Comparative Examples 3 and 4 are commercially available glass materials.

[0048] Comparative Example 5 - High-alumina silicate glass (GE180) mentioned in the background art.

[0049] The properties of the glass materials in Comparative Examples 1 to 5 are shown in Table 2.

[0050] Table 2

[0051]

[0052] Table 2 shows that the glass material prepared in Comparative Example 1 has a softening point greater than 1100℃, and its processability is generally poor. Furthermore, the glass material prepared in Comparative Example 2 is milky white and translucent, exhibiting poor optical properties. Comparative Example 3 is commercially available Pyrex glass; due to the presence of boron in its composition, its neutron transmittance is only 20%@4.5Å. Comparative Example 4 is commercially available Corning 1720 glass; due to the presence of a small amount of boron in its composition, its neutron transmittance is 50%@4.5Å.

[0053] The glass softening temperature of Comparative Example 5 was 1015℃, and the relaxation time was 180h.

[0054] Comparative Example 6

[0055] A method for preparing a glass material for a gas chamber specifically includes the following steps:

[0056] (1) Add barium oxide, aluminum oxide, silicon oxide and titanium oxide to a mixer in the following mass percentages and mix: 35% barium oxide, 12.5% ​​aluminum oxide, 52% silicon oxide and 0.5% titanium oxide; after mixing evenly, glass raw material is obtained;

[0057] (2) Add the glass raw material obtained in step (1) into a quartz crucible, heat it to 1800°C in an air atmosphere, keep it at the high temperature for 15 hours, and stir it with a quartz rod until it becomes clear and homogenized to obtain liquid glass.

[0058] (3) The liquid glass obtained in step (2) is drawn into the mold and blown and drawn to obtain the forming air chamber;

[0059] (4) Place the molding chamber from step (3) in an annealing furnace filled with dry Cl2 / Ar (chlorine volume fraction of 10%) and anneal it at 800°C for 0.5 h.

[0060] (5) After annealing, the cavity of the gas chamber is cleaned with supercritical CO2 fluid (60 mL / min) (pressure 15 MPa) to completely remove organic pollutants. Then, 80 mbar N2O gas is introduced and irradiated with a low-pressure ultraviolet mercury lamp for 10 min. After the surface of the gas chamber is passivated, a glass gas chamber is obtained.

[0061] The relaxation time of glass in Comparative Example 6 was 200 h.

Claims

1. A type of polarization 3 The method for preparing glass material for the gas chamber of a He neutron spin filter is characterized by... Includes the following steps: (1) Barium oxide, aluminum oxide, silicon oxide and titanium oxide are mixed and placed in a quartz crucible. The mixture is then melted at 1600~1800℃ for 10~24h in a chlorine atmosphere to obtain liquid glass. The barium oxide, aluminum oxide, silicon oxide and titanium oxide are mixed in the following mass percentages: 30~40% barium oxide, 10~15% aluminum oxide, 50~60wt% silicon oxide and 0~2% titanium oxide. (2) The liquid glass is blown into a molded gas chamber, and then the molded gas chamber is annealed in a chlorine-rich atmosphere; (3) After annealing, the cavity of the gas chamber is cleaned with supercritical CO2 fluid. After cleaning, N2O gas is filled in and a passivated surface is formed on the glass surface under ultraviolet light irradiation to obtain a glass gas chamber.

2. The preparation method according to claim 1, characterized in that: In step (1), the chlorine-containing atmosphere refers to adding chlorine gas with a volume fraction of no more than 5% to the air.

3. The preparation method according to claim 1, characterized in that: In step (2), the chlorine-rich atmosphere refers to a Cl2 / Ar atmosphere, wherein the volume fraction of chlorine is 10-30%.

4. The preparation method according to claim 1, characterized in that: In step (2), the annealing temperature is 700~900℃ and the annealing time is 0.5~1h.

5. The preparation method according to claim 1, characterized in that: In step (3), the flow rate of supercritical CO2 fluid is 50~60 mL / min during the cleaning process.

6. The preparation method according to claim 1, characterized in that: In step (3), the pressure in the chamber of the gas chamber is not less than 15 MPa.

7. The preparation method according to claim 1, characterized in that: In step (3), N2O gas at 80~100 mbar is introduced.

8. The preparation method according to claim 1, characterized in that: In step (3), a low-pressure ultraviolet mercury lamp is used for irradiation for 5 to 10 minutes; the power of the low-pressure ultraviolet mercury lamp is 30 to 40W.

9. The preparation method according to claim 1, characterized in that: In step (3), the softening point temperature of the glass gas chamber is not higher than 1100℃.

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