JPH0511307U - Vacuum device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a vacuum device in which leakage does not occur even if baking processing is performed. [Structure] The electron gun chamber located above the focusing lens 1 is
For example, when baking is performed at 200 ° C., the yoke 2 made of iron cobalt 2 and the flange 3 made of pure iron are heated to about 200 ° C. Therefore, the yoke 2 and the flange 3 are thermally expanded. Since the coefficient of thermal expansion of pure iron is larger than that of iron cobalt, the vertical thermal expansion of the flange 3 is larger than that of the yoke 2. Therefore, a gap of Δl is generated between the metal O-ring 6 and the flange 3. By the way, bush 7
Is selected as a member that thermally expands by Δl at 200 ° C. as compared with that at room temperature, so that the bush 7 thermally expands and lifts the yoke 2 by Δl during the baking process. Therefore, no gap is generated between the metal O-ring 6 and the flange 3, and the electron gun chamber is vacuum-sealed from the coil portion of the focusing lens 1.

Description

[Detailed description of the device]

[0001]

TECHNICAL FIELD The present invention relates to a vacuum device such as an electron microscope.

[0002]

2. Description of the Related Art In a vacuum apparatus such as an electron microscope, a baking process is carried out at a high temperature, so that a metal O-ring suitable for heat resistance is used in a vacuum seal portion. For example, in the electron lens located in the lower stage of the electron gun chamber, a magnetic path formed by connecting iron cobalt and pure iron is formed around the coil. O-rings are used.

[0003]

When the electron lens is baked at a high temperature, the iron cobalt and pure iron expand. Since the thermal expansion coefficients of these members are different, a gap is created between the metal O-ring and the member, causing a leak. This leak causes a large amount of gas to enter the vacuum and contaminate the vacuum.

The present invention provides a novel vacuum device that solves such a problem.

[0005]

Means for Solving the Problems The vacuum device of the present invention comprises a thermal expansion member that expands by the amount of the gap at the time of the treatment in order to prevent a gap from occurring between the metal and the heat-resistant vacuum seal member during the baking treatment. Due to the expansion, the structure is embedded in a position where the gap is eliminated.

[0006]

Embodiment FIG. 1 is a cross-sectional view showing an embodiment of the present invention, in which reference numeral 1 is a focusing lens of an electron microscope located in the lower stage of the electron gun chamber. This focusing lens 1 comprises a yoke made of iron cobalt, a flange 3 made of pure iron, and an exciting coil 4. Reference numeral 5 is a liner tube, 6 is a metal O ring for vacuum-sealing the electron gun chamber and the focusing lens 1, and 7 is a bush described later.

In such a structure, when the focusing lens 1 is baked at 200 ° C., for example, the yoke 2 and the flange 3 are heated to about 200 ° C. Therefore, the yoke 2 and the flange 3 are thermally expanded. By the way, since the coefficient of thermal expansion of pure iron is larger than that of iron cobalt, the vertical thermal expansion of the flange 3 is larger than that of the yoke 2. Therefore, as shown in FIG. 2, a gap of Δl is generated between the metal O-ring 6 and the flange 3.

By the way, as the bush 7, a member is selected that thermally expands by Δl at 200 ° C. as compared with that at room temperature. Since the bush 7 is embedded in the flange 3 at the position shown in FIG. 1, the bush 7 thermally expands and lifts the yoke 2 upward by Δl. Therefore, no gap is generated between the metal O-ring 6 and the flange 3, and the electron gun chamber is vacuum-sealed from the coil portion of the focusing lens 1.

Further, even if the bush 7 is embedded in the upper end or the lower end of the yoke 2, it is possible to prevent the generation of the gap due to the baking process. Also, the same effect can be obtained by embedding the bush 7 at a position where it contacts the metal O-ring 6 of the flange 3.

[0010]

According to the present invention, in order to prevent a gap from being formed between the metal and the heat-resistant vacuum seal member by the baking process, the thermal expansion member that expands by the amount of the gap during the process is expanded by the expansion. Since it is embedded at the position where the bake is eliminated, no gap is created by the baking process. Therefore, no leak occurs and the vacuum chamber is kept in vacuum.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is provided to explain the present invention.

[Explanation of symbols]

1 ... Focusing lens, 2 ... Yoke, 3 ... Flange, 4 ... Excitation coil, 5 ... Liner tube, 6 ... Metal O-ring,
7 ... Bush

Claims (1)

[Scope of utility model registration request] 1. A vacuum device for maintaining a vacuum state of a vacuum chamber by disposing a heat-resistant vacuum seal member in a vacuum seal portion of a metal joining portion, wherein a gap is formed between the metal and the heat-resistant vacuum seal member by baking treatment. In order to prevent this from occurring, a vacuum device characterized in that a thermal expansion member that expands by the amount of the gap during the treatment is embedded in a position where the gap is eliminated by the expansion.