JP3103800B2 - High voltage insulation material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the shape of a member for insulating a voltage, and more particularly to a charged particle beam accelerating tube, an insulator and the like which are unlikely to generate high-voltage discharge.

[0002]

2. Description of the Related Art As disclosed in Japanese Patent Application Laid-Open No. 4-322015, for example, a conventional high-voltage insulating member is provided with a conductive material around a joint of an insulating member (in this example, a cylindrical insulator) with a conductive member. By providing a groove with a coating, the direction of the electric field is different from the direction of the edge surface, so that the joining material such as silver brazing does not flow out of the groove, making it difficult to generate a minute discharge at this joint, The goal was to prevent provocation.

[0003]

Although the above prior art is effective in preventing discharge in principle, it is difficult to inspect the joint because the joint is hidden by the shoulder of the groove and the metal fitting of the conductive member. Foreign matter such as dust is difficult to remove, it is difficult to completely clean the joints by sandblasting, etc., and it is necessary to newly create a groove in the insulating member at the time of manufacture, insulation of the shoulder of the groove If the electric field concentrates on the portion and the gap between the conductive member and the conductive member is not precisely controlled, there is a problem that the portion is easily discharged.

The present invention provides a high-voltage insulating member which is effective in preventing unnecessary discharge of a bonding material such as silver brazing by a simple processing of the insulating member to prevent discharge, and is easy in maintenance such as cleaning. The purpose is to:

[0005]

Means for Solving the Problems The end face of the insulating member joined to the conductive member (the end face of the cylindrical insulator in the above-mentioned prior art example)
The above problem is solved by chamfering the periphery of at least doubly with different inclinations from the joint end surface toward the outer peripheral surface of the insulating member, and keeping the protruding brazing material on the chamfer surface closest to the joint surface. .

[0006] When the discharge becomes a problem in the high-voltage insulating member having the above structure, the discharge path starts from a minute projection on the protrusion of the brazing material generated at the edge of the metallized layer, and the dielectric strength is lowered. It often passes through a small insulating member surface to the other conductive member.

According to the present invention, the protrusion of the brazing material generated at the edge of the metallized layer of the insulating member due to the surface tension of the molten brazing material is settled on the innermost chamfered surface in contact with the joining surface, and the outer portion thereof It doesn't go far. The innermost chamfered surface has a smaller component in the direction of the electric field along its outer surface than the outer chamfered surface and the side surface of the insulating member. Hateful. The secondary electrons generated by the minute discharge are also hardly accelerated on the innermost chamfered surface, and hardly develop into a large discharge. Therefore, a high voltage can be stably applied.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. This is an application of the present invention to an acceleration tube for an electron microscope.

FIG. 1 is an enlarged view of a longitudinal section of a main part of the acceleration tube (a part excluding upper and lower flanges of the acceleration tube and an acceleration electrode), and cylindrical insulators 1 are stacked in multiple stages with an electrode support ring 3 interposed therebetween. Indicates a state in which The cylindrical insulator 1 as an insulating member is made of alumina ceramics or the like. As shown in FIG. 2, the cylindrical insulator 1 has a flattened joint end face 10 and a conductive film 2 containing a high melting point metal powder such as molybdenum-manganese (metallization). The first chamfered surface 5 has a circumference of the end face toward the end face θ ₁ (for example, 15 degrees).
It is a surface chamfered at an angle. Further, the periphery thereof is chamfered at an angle of θ ₂ (for example, 45 degrees) toward the end face to form a second
Is formed. Here, θ ₁ <θ ₂ .

In this embodiment, the metallizing process is applied to about half of the chamfered surface 5 on the side in contact with the end face 10,
The metallizing process on the chamfered surface 5 may not be required, the metallizing process on the end face 10 may protrude,
It may be on the entire surface. However, the metallization process must not protrude from the chamfered surface 6. This is because the brazing material flows up to the portion where the conductive film is applied by the metallizing process.

A chamfered surface may be further provided outside the chamfered surface 6 in order to form an edge at an intersection between the chamfered surface 6 and the side surface of the cylindrical insulator 1. Alternatively, the chamfered surface 6 need not be a conical surface, but may be a curved surface having curvatures in two directions for edge protection.

A plurality of cylindrical insulators 1 are stacked by a predetermined number of steps via an electrode support ring 3 made of an iron-cobalt-nickel alloy or the like as a conductive member.
After brazing the conductive film 2 and the electrode support ring 3 with a brazing material 4 such as silver brazing, flanges are welded to the upper and lower portions to form a multi-stage accelerating tube.

An accelerating electrode (not shown) for accelerating electrons is attached to each of the electrode support rings 3 inside the accelerating tube (inside the cylinder). Each electrode support ring and the accelerating electrode are given a predetermined potential in an insulating gas atmosphere from outside the accelerating tube via a bleeder resistor (not shown) or the like. The interior of the accelerating tube is evacuated to a vacuum, and the electrons travel in the vacuum, and are sequentially accelerated in the axial direction of the cylinder by the accelerating electrode to finally obtain a predetermined energy.

In general, in an accelerating tube having such a structure, a place where discharge is most likely to occur is where an insulating member, a conductive member, and a vacuum or an insulating gas are in contact with each other. That is, the brazing material 4 is an edge portion protruding toward the cylindrical insulator 1. Since the surface of the brazing material in this portion cools and hardens before the inside of the brazing material, when the inside hardens with a delay, it is pulled from the inside, and fine cracks and projections are formed on the surface. When a voltage is applied thereto, the electric field is concentrated and a minute discharge is likely to occur. The electron flow generated from the minute discharge is accelerated in the direction of a relatively positive potential, and the cylindrical insulator 1
It becomes a large electron flow with secondary electrons generated from inside,
A large discharge is reached upon reaching the opposing positive electrode.

In this embodiment, the gap between the chamfered surface 5 and the electrode support ring 3 is filled with the brazing material 4 by utilizing the surface tension when the brazing material is melted, and the surrounding chamfered surface is formed. 6 can easily be prevented from protruding. Further, if a conductive film is applied to a part of the innermost chamfered surface (first chamfered surface 5), the brazing material is guided, so that the protrusion is more evenly and surely formed.
And the above-mentioned structure in which discharge is difficult is easily achieved.

In this embodiment, the application of the present invention to an acceleration tube is shown, but the present invention is not limited to this.
By selecting the shape of the insulator to be brazed according to the application, such as cylindrical or rod type, it can be applied to various high-voltage insulating members ranging from a structure that can maintain a vacuum like an accelerating tube to a simple insulating rod. Inspection of foreign matter adhering to the joint and cleaning by sandblasting are also easier than in the case of the above-mentioned prior art.

[0017]

According to the present invention, the end of the insulating member is chamfered at least twice, so that the protrusion of the brazing material generated when the insulating member and the metal member are joined by brazing can be accommodated in the innermost chamfered surface. it can. The innermost chamfered surface, compared to the outer chamfered surface and the side of the insulating member,
Since the component in the direction of the electric field on the creeping surface is small, even if the electric field is concentrated on the fine protrusions on the protruding brazing material, it is difficult for the micro discharge to start. The secondary electrons generated by the minute discharge are also hardly accelerated on the innermost chamfered surface, and hardly develop into a large discharge. Therefore, a high voltage can be stably applied.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a longitudinal section of a main part of an acceleration tube according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a longitudinal section of a side surface of the cylindrical insulator according to the embodiment of FIG. 1;

[Explanation of symbols]

1: cylindrical insulator, 2: conductive film, 3: electrode support ring, 4: brazing material, 5: first chamfered surface of cylindrical insulator,
6: second chamfered surface of the cylindrical insulator, 10: end surface of the cylindrical insulator.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadao Kotsu 2520 Akanuma-cho, Hatoyama-cho, Hiki-gun, Saitama Prefecture Inside Hitachi, Ltd.Basic Research Laboratories (72) Takaho Yoshida 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama Hitachi, Ltd. Basic Research Laboratory (72) Inventor Isao Matsui 882 Ma, Hitachinaka-shi, Ibaraki Pref.Hitachi, Ltd.Measurement Equipment Division (72) Inventor Hiroyuki Shuto 10-1 Kawai, Gamo-cho, Gamo-gun, Shiga Prefecture Kyocera Corporation (56) References JP-A-1-130455 (JP, A) JP-A-4-322015 (JP, A) JP-A 10-92363 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01B 17/56 H01B 17/50 H01J 37/04

Claims (2)

(57) [Claims] 1. A high-voltage insulating member whose end is joined to a metal material with a brazing material, wherein the insulating member has a continuous end chamfered at least two different angles from a joint end face of the insulating member. A high-voltage insulating member, which extends to a surface. 2. The high-voltage insulating member according to claim 1, wherein a conductive film is applied to the entire surface or a part of the chamfered surface closest to the joint end surface.