JPS6089049A - Device for attaching and detaching high voltage member - Google Patents

Abstract

PURPOSE:To increase the dielectric withstand voltage of a charged particle ray device such as an electron microscope by interposing EP rubber between a bushing formed using an epoxy resin and a replacement bar formed using the same resin when attaching an electron gun or similar equipment, to which high voltage is applied, to the device. CONSTITUTION:When holding an electron gun 3 to which high voltage is applied within the mirror tube 1 of a charged particle ray device such as an electron microscope, a funnel-like bushing 19 formed by integrating end members 20 and 21 having field-alleviating rings 15 and 16 with an epoxy resin is fixed between the mirror tube 1 and the electron gun 3. At the same time, a funnel-like insulating replacement bar 22 formed by unifying an epoxy resin, a lid 12 and the electron gun 3 is attached to the bushing 19 with an insulating spacer 23 made of EP rubber interposed, thereby completing assembly. As a result, it is possible to achieve a high degree of close contact between the replacement bar 22 and the bushing 19 even when the accuracy of the bar 22 and the taper of the bushing 19 is somewhat low. Accordingly, it is possible to easily perform the replacement of the electron gun 3 or similar equipment by producing a high dielectric withstand voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a device for attaching and detaching a high voltage member in a device to which a high voltage is applied, such as a charged particle beam device.

In charged particle beam devices such as electron microscopes, the electron gun or ion source to which high voltage is applied and its power source are spatially separated for convenience of maintenance and transportation, and the distance between the electron gun and the power source is separated. It is connected with a detachable flexible insulated cable.

FIG. 1 is a cross-sectional view showing the vicinity of an electron gun in a conventional electron microscope, and 1 in the figure indicates an electron gun chamber formed at the upper end of the lens barrel. At the center of the lower part of the electron gun chamber, an acceleration tube 2 having multistage acceleration electrodes for accelerating the electron beam is arranged, and an electron beam consisting of a cathode, a grid, etc., to which a high voltage of about 200 KV is applied to the upper opening of the tube 2 is arranged. The gun electrode section 3 is inserted in an airtight manner, and the inside of the acceleration tube 2 is kept in a vacuum. The space between the acceleration tube 2 and the side wall of the lens barrel is filled with Freon gas at a pressure of about 1.5 atmospheres to maintain insulation between the acceleration tube 2 and the electron gun electrode section 3 and the side wall of the lens barrel, which is kept at ground potential. That's what I do. A cylindrical holder 4 for holding an electron gun electrode part 3 is attached to the top of the acceleration tube 2, and a high voltage member at the tip of an insulating exchange rod 5 that penetrates the side wall of the lens barrel is attached to the side wall of the cylindrical holder 4. That is, a socket (not shown) is formed to connect with the terminal 6 of the insulated cable 7. A 114-shaped bushing 8 is provided as a holder for the insulation exchange rod 5 between the holder 6 and the lens barrel side wall, and an insulating material such as epoxy resin, which is relatively rigid, is used as the bushing material. An electric field relaxation ring 9 formed on the side wall and an electric field relaxation ring 10 attached to the side surface of the socket 4 are connected to the low potential side and the high potential side of the bushing 8. The upper part of the electron gun electrode part 3 is made of a reinforcing material 11 made of Duracon, which has relatively high rigidity.
The insulating member 1 is attached to the lid body 12 by the insulating member 1 made of relatively elastic silicone rubber around the reinforcing member 11.
3 fits into a funnel-shaped bushing 14 as an insulation exchange rod. The bushing 14 is made of an insulating material such as epoxy resin, and its low potential side and high potential side end faces are in contact with the electric field relaxing ring 15 of the lid 12 and the electric field relaxing ring 16 of the receiver 4, respectively. Note that the protrusions 17 and 18 formed on the lower surface of the lid 12 and the upper part of the electron gun electrode section 3 are for relaxing the electric field.

In an electron gun having such a configuration, the electron gun and its power source can be connected very easily by releasing the holding device (not shown) of the insulation replacement rod 5 and pulling out the insulation replacement rod 5 from the side wall of the lens barrel. It is possible to separate the bond, and in order to replace the filament cathode in the electron gun section 3, after leaking the vacuum inside the acceleration tube 3, the electron gun section 3 is removed by pulling the lid 12 upward. It can be easily taken out to the atmosphere. However, when attempting to increase the voltage applied to the electron gun section from about 1,200 KV to about 1,400 KV, the following problems arise.

(1) In order to improve the close contact between the fitting portion of the bushing and the insulation replacement rod, it is necessary to improve the finishing accuracy of the taper part, which makes manufacturing thereof much more difficult.

(2) If a gap is formed between the contact surface between the bushing 8 or 14 and the electric field relaxation ring, the dielectric strength will drop significantly, so conductive paint or the like is applied to the contact surface, but it is still difficult to achieve complete contact.

(3) When using EP rubber as the insulation replacement rod,
Because EP rubber deteriorates quickly over time, it becomes necessary to replace it within a short period of time. This replacement must include the insulated cable, which is a rather cumbersome and expensive operation.

(4) If silicone rubber is used as the insulation replacement rod, the silicone grease applied to the fitting surface with the bushing has an affinity with the silicone rubber, so the insulation replacement rod will need to be replaced due to aging.

SUMMARY OF THE INVENTION The present invention aims to solve these drawbacks and provide a device for attaching and detaching high-voltage members with a simple structure and high insulation properties. In a device in which a high voltage member is attached to the tip of an insulating insertion rod that fits into a shaped insulating bushing, an insulating spacer formed in an i-shape and having relatively high elasticity is inserted between the insulating insertion rod and the bushing. The insulating insertion rod and the bushing are fitted together, and a conductive member having an electric field relaxation ring that contacts the low-potential side and high-potential side end surfaces of the bushing is connected to a relatively rigid insulating material constituting the bushing. It is characterized by being integrally molded.

4- In FIG. 2, the present invention is applied to the attachment/detachment part of the electron gun electrode section, and the same reference numerals as in the box 1 diagram in the drawing indicate the same components. A major feature of the device shown in FIG. 2 is that the bushing 19 is integrally formed with the epoxy resin and the conductive members 20 and 21 having electric field relaxation rings 15 and 16 at both ends thereof.

By forming the device in this manner, a gap is not formed between the epoxy resin and the electric field relaxation ring, so that the dielectric strength can be increased compared to the device shown in FIG. In addition, since the lid body 12 and the electron gun electrode part 3 are also integrally molded by the insulation replacement rod 22 made of epoxy resin, the dielectric strength voltage between the insulation replacement rod 22, the lid body 12, and the electron gun electrode part 3 can also be increased. can. However, since the insulation exchange rod 22 and the bushing 19 are made of a relatively rigid epoxy resin, it is not possible to increase the degree of adhesion when the two are fitted together as is. Therefore, in the device shown in FIG. 2, a funnel-shaped insulating spacer 23 made of EP rubber is placed between the bushing 19 and the insulation exchange rod 22.
The two are fitted together through. With this configuration, by pressing the insulation exchange rod 22 from above the lid 12, it is possible to easily prevent a gap from forming between the insulation exchange rod 22 and the bushing 19, and to obtain a high dielectric strength voltage. becomes.

FIG. 3 shows an embodiment in which the present invention is applied to the attachment/detachment part between an electron gun and an insulated cable terminal. As in the case of FIG. 2, the same reference numerals as in FIG. 1 have the same structure. represents an element. In the apparatus shown in FIG. 3, an insulation replacement rod 25 made of epoxy resin is attached to the end of the cable 7 via a metal fitting 24, and a conductive pipe 26 is embedded in the center thereof. Conductive wires connected to the core wire of the cable 7 run inside the conductive pipe 26, and are connected to the respective electrodes of the electron gun electrode section through the respective terminals of the terminal terminal 26 attached to the tip of the exchange rod.

All of the members that come into contact with the epoxy resin are integrally molded from the epoxy resin, and their deterioration over time is extremely small compared to when EP rubber is used as in the past. The bushing 27 on the side receiving the insulation exchange rod 25 is made of epoxy resin, and the member 2 has an electric field relaxation ring 9 provided on its low voltage side by the epoxy resin.
8 and an electric field relaxation ring 10 provided on the high voltage side, the cable receiver is integrally molded with the metal fitting 29. Furthermore, a funnel-shaped insulating spacer 30 made of EP rubber is inserted between the insulation exchange rod 25 and the bushing 27 to prevent a gap from occurring at the fitting portion of the insulation exchange rod 25 and the bushing 27. There is.

As described above, in the device of the present invention, it is possible to fit the insulation exchange rod and the bushing with a high degree of adhesion even if the machining pattern of the tapered part of the bushing is somewhat low, thereby increasing the dielectric strength in the high voltage member exchange mechanism. Disadvantages mentioned above (1)
can be solved. Further, since the insulating material that contacts the electric field relaxation ring and the electric field relaxation ring are integrally molded, no minute gaps are generated, and the above-mentioned drawback (2) is solved. By the way, in the above-mentioned embodiment device, a highly elastic EP rubber is used which is inserted between the insulation exchange rod and the bushing, and this EP rubber deteriorates over time, but the In such a case, only the FP rubber spacer needs to be replaced, so the time and cost required for replacement will hardly be a problem.

As described above, the present invention makes it possible to increase the dielectric strength of the high-voltage member exchange mechanism with a simple configuration, and therefore has a great effect on improving the performance of particle beam devices such as electron microscopes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an electron gun in a conventional electron microscope, and FIGS. 2 and 3 are schematic diagrams showing an embodiment of the apparatus according to the present invention. 1: Electron gun chamber, 2: Accelerator tube, 3: Electron gun electrode section, 4: Receiving section, 5, 13.22.26: Insulation exchange rod, 6: Terminal,
7: Insulated cable, 8.14.19° 27: Bushing, 9.10.15, 16: Electric field relaxation ring, 23, 30
: Insulating space 9゜8- Figure 1

Claims (1)

[Claims] In a device in which a high voltage member is attached to the tip of an insulating insertion rod that fits into a funnel-shaped insulating bushing attached to a base at a low potential, a funnel-shaped member is formed between the insulating insertion rod and the bushing and a relatively Fitting the insulating insertion rod and the bushing via a highly elastic insulating spacer,
A high-voltage member characterized in that a conductive member having an electric field relaxation ring that contacts the low-potential side and high-potential side end faces of the bushing is integrally molded with a relatively rigid insulating material that constitutes the bushing. Attachment and detachment device.