JP2822516B2 - Electron beam generator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a cathode in an electron beam generator used for performing electron beam melting, electron beam evaporation, and the like.

[Conventional technology]

FIG. 3 shows the structure of a conventional electron beam generator. In FIG. 1, reference numeral 1 denotes a vacuum container which is an apparatus container, and 2 denotes an ion stopper. 3 is filament, 4
Is a disk-shaped block cathode (hereinafter, simply referred to as a cathode) having a through hole 4a at the center, and both constitute a hot cathode unit (thermal electron source) 5. Reference numeral 6 denotes a Wehnelt electrode for preventing diffusion of thermoelectrons, and reference numeral 7 denotes an anode for accelerating thermoelectrons. At the center, a passage hole 7a through which the electron beam B passes is formed. 8 filament heating power source (voltage V _f), E _K is an acceleration voltage, E _A is the acceleration voltage.

The filament 3 is supplied with power from the filament heating power supply 8 and rises in temperature to generate thermoelectrons e. This thermoelectron e is
In an electric field of accelerating voltage E _K makes with an electric field accelerates the cathode 4
And the cathode 4 is heated. Cathode 4 is heated to emit thermal electrons e, the thermal electrons e is converged is preventing the diffusion in Wehnelt electrode 6, thermionic (electron beam) B is the electric field created by the acceleration voltage E _A that this focused With anode 7
Is accelerated toward the side, passing through the passage hole 7a of the anode 7,
Although not shown, the workpiece is further subjected to a focusing action by one or a plurality of focusing electrodes, and then passes through a deflection coil to irradiate the workpiece.

Conventionally, as shown in FIGS. 4 (a) and 4 (b), the cathode 4 is generally a cathode holder set on each of a plurality of columns 10 extending from a fixed portion A in the vacuum vessel 1. 11 and supported by a cathode holding mechanism including a cathode support arm 12 and a set screw 13 and disposed in the vacuum vessel 1. Each cathode holder 11
Has a hole 11a of a predetermined depth, and is set on the column 10 with the open end of the hole 11a facing the operational center O in the vacuum vessel 1. The cathode support arm 12 has one end inserted into the hole 11a, fixed with a set screw 13 and supported by the cathode holder 11 in a cantilever manner, and the other end opened in the peripheral surface of the cathode 4 (a radial hole). ) 4b to support the cathode 4. Numeral 14 is a nut for fixing the column.

[Problems to be solved by the invention]

Conventionally, a cathode support arm 12 for supporting the cathode 4
Is inserted into the mounting hole 4b of the cathode 4 to support the cathode 4, the cathode 4 and the support arm 12 may be seized. When the seizure occurs, the support arm 12 is separated from the block cathode 4. If it is difficult to pull out and the support arm 12 bends or breaks, the block cathode 4 must be discarded together with the support arm 12, and the block cathode 4 cannot be reused, which is uneconomical. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an electron beam generator capable of replacing a support arm and reusing a cathode even when the support arm becomes defective. Aim.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a cathode,
It has at least one set of spare support holes.

[Action]

According to the present invention, even if the support arm is bent or broken because the connecting end of the support arm is welded to the mounting hole of the block cathode and the support arm is bent, the mounting hole cannot be used. Since the cathode has a spare mounting hole, if the support arm is replaced and the spare mounting hole is used, the block cathode does not need to be replaced.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIGS. 1 (a) and 1 (b), 20 is molybdenum.
A ring body made of Mo, having an inner diameter larger than the outer diameter of the cathode 4, and having radial holes (screw holes) 20a penetrating from the outer peripheral surface to the inner peripheral surface at regular intervals in the circumferential direction. Have been. The ring body 20 further includes
A hole 20b for screwing 10 is formed. Reference numeral 21 denotes a holder made of tantalum Ta or molybdenum Mo, which constitutes the cathode holder 11 together with the ring body 20, and a screw screwed into the hole 20a is engraved on the outer peripheral surface thereof. The inner end 21A is screwed so as to project.
Inner end of holder 21 projecting from the inner peripheral surface of ring body 20
A hole 21a is formed in 21A, which is open at the end face of the inner end 21A. This hole 21a has a depth not greater than the length of the inner end 21A. Reference numeral 22 denotes a support arm made of tungsten W. One end of the support arm is fitted into the hole 21a of the connecting end holder 21 and the other connecting end 22A is fitted into a radial hole 4b opening on the outer peripheral surface of the cathode 4. Have been. The cathode block 4 has three spare mounting holes 4c in addition to the three mounting holes 4b.

In this embodiment, with the connecting end 22A of the support arm 22 welded to the mounting hole 4b of the block cathode 4, the mounting hole 4b is used because the support arm 22 is bent or broken due to, for example, adjustment work. When it is no longer possible, the portion protruding from the mounting hole 4b of the support arm 22 is cut off, the support arm 22 is replaced with a new one, and the connection end 22A is blocked as shown in FIG. By inserting the block cathode 4 into the spare mounting hole 4c of the cathode 4, it is not necessary to replace the block cathode 4 with a new one.

In the above-described conventional cathode support mechanism, a plurality of cathode support arms 12 are individually provided in the cathode holder 11.
Since the cathode holders 11 are cantilevered and the respective cathode holders 11 are individually set (screw-connected) on the columns 10, the direction of the cathode holders 11 is not adjusted for the positioning of the cathodes 4 for each cathode holder. In addition, adjustment of the projection length of the cathode support arm 12 from the cathode holder 11 must be performed while loosening or tightening the set screw 13, and since each column 10 tends to have a positional error,
There is a problem that it takes time and effort to adjust the center of the cathode 4 so as to be located at the operation center O. However, the cathode holding mechanism of the above embodiment has a plurality of holders that cantileverly support the support arm 22. In this structure, the ring 21 is supported by a plurality of columns 10, so that the ring 21 can be supported without adjusting the direction of the holder 21. There is an advantage that the position of the cathode 4 can be adjusted only by turning the holder 21 so that the 21 can be directed to the operation center O. Further, in the above embodiment, since the one connection end of the support arm 22 does not extend to the inner peripheral surface of the ring body 20, the holder arm
Rotate the inner end 21 of the ring body 20 in the radial hole 20.
When the support arm 22 is almost pulled in, the one connection end of the support arm 22 is detached from both the holder 21 and the ring body 20. Therefore, when the other connection end of the support arm 22 is seized on the cathode 4, Even without removing the ring body 20 from the support 10,
The replacement of the cathode 4 can be performed.

In the above embodiment, only one set of the spare mounting holes 4c is provided, but it goes without saying that a plurality of sets may be provided.

〔The invention's effect〕

As described above, since the block cathode has a spare mounting hole as described above, even if the support arm is seized and the support arm becomes defective at the time of adjustment work or the like, the spare hole is used. Since it is possible to support the battery, it is not necessary to replace the block cathode, and the cost can be improved as compared with the related art.

[Brief description of the drawings]

1 (a) and 1 (b) are a plan view and a side view, respectively, of an embodiment of the present invention. FIG. 2 is a view showing a state in which a spare mounting hole for a block cathode in the above embodiment is used. 3 is a schematic configuration diagram of a conventional electron beam generator, and FIGS. 4A and 4B are a plan view and a side view showing a conventional cathode support mechanism, respectively. 4 ... Block cathode, 4b ... Mounting hole, 4c ... Spare mounting hole, 20 ... Ring body to be fixed part, 21 ... Holder element, 22 ... Support arm. 22A …… Connection end,

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01J 37/06-37/07 H01J 37/075

Claims (1)

(57) [Claims] An electron which emits an electron beam generated by irradiating a workpiece with an electron beam generated by providing an accelerating anode to which an accelerating voltage is applied between the hot cathode and an electron emitted from the hot cathode unit. The hot cathode unit of the beam generating device has a block cathode having a plurality of mounting holes on a side peripheral surface, and the block cathode extends from a fixed portion in the apparatus container into the corresponding mounting hole of the block cathode. An electron beam generator supported by a plurality of support arms, wherein the block cathode has at least one set of spare mounting holes as a set of the plurality of sets.