JPH03194836A - Electron beam generator - Google Patents

Abstract

PURPOSE:To prevent temperature ununiformity of a block cathode by tapering the linking end portion inserted into the cathode fixing hole of a supporting arm or the cathode fixing hole and bringing both into liner contact. CONSTITUTION:A ring body 20 has an inside diameter larger than the outside diameter of a block cathode 4, while radially directional tapped holes 20a, passing from the external circumferential surface to the internal circumferential surface, are made in the circumferential direction at fixed intervals. A holder 21 and a ring body 20 constitute a cathode holder, and an internal end portion 21A is threadably attached to the external circumferential surface of the holder 21 such that the internal end portion 21A projects to the hole 20a. One linking end portion of the supporting arm 22 is fitted into the hole 21a of the holder 21, and the other linking portion 22A is fitted into the fixing hole 4b on the external circumferential surface of the block cathode 4. The supporting arm 22 has a diameter larger than that of the fixing hole 4b and a continuous end portion 22A is tapered and the arm 22 is engaged to the opening edge of the fixing hole 4b on the surface tapered as above to support the block cathode 4. It is thereby possible to uniform the temperature distribution of the block cathode and get an electron beam without unevenness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an improvement of a cathode support mechanism in an electron beam generator used for performing electron beam melting, electron beam evaporation, and the like.

[Conventional technology]

FIG. 3 shows the configuration of a conventional electron beam generator. In the same figure, ■ is a vacuum container which is an equipment container;
2 is an ion stopper. 3 is a filament, 4 is a disc-shaped block cathode (hereinafter simply referred to as cathode) having a through hole 4a in the center, and both constitute a hot cathode unit (thermionic generation source) 5. 6 is a Wehnelt electrode for preventing diffusion of thermoelectrons, 7 is an anode for accelerating thermoelectrons, and a passage hole 7a through which the electron beam B passes is formed in the center. 8 is a filament heating power source (voltage v), EK is an acceleration voltage, and EA is an acceleration voltage.

The filament 3 is supplied with power from the filament heating power source 8 and is heated to generate thermoelectrons e. These thermoelectrons e are accelerated in the electric field created by the accelerating voltage EK and are applied to the cathode 4.
collides with the cathode 4 and heats the cathode 4. The heated cathode 4 emits thermionic electrons e, which are prevented from diffusing and focused by the Wehnelt electrode 6, and the focused thermionic electrons (
Electron beam) B is the anode 7 in the electric field created by the acceleration voltage EA.
It is accelerated toward the side, passes through the passage hole 7a of the anode 7, is further focused by one or more focusing electrodes (not shown), and then passes through a deflection coil to irradiate the workpiece. be done.

By the way, the cathode 4 has conventionally been generally shown in FIG.
As shown in a) and (b), a cathode holder 11 and a cathode support arm 12 are set on each of a plurality of pillars 10 extending from a fixed part A in the vacuum container 1.
It is supported by a cathode holding mechanism consisting of a set screw 13 and a set screw 13, and is disposed within the vacuum vessel 1. Each cathode holder II has a hole 11a with a predetermined depth, and the open end of the hole 11a is directed toward the operational center 0 in the vacuum vessel 1 so that the column 10
set on top. The cathode support arm 12 has one end inserted into the hole 11a, fixed with a set screw 13, and cantilevered by the cathode holder 11, and the other end opened on the circumferential surface of the cathode 4. The cathode 4 is supported by being inserted into the hole 4b as shown in FIG. Numeral 14 is a nut for fixing the pillar.

[Problem to be solved by the invention]

As shown in FIG. 5, conventionally, the cathode support arm 12 supporting the cathode 4 is connected to the radial hole 4b of the cathode 4.
Since the cathode 4 is supported by inserting the end face into strong pressure contact with the bottom of the mounting hole 4b, heat dissipation from the cathode 4 through the cathode support arm 12 increases, and the cathode 4 The temperature distribution becomes non-uniform and the beam current becomes small in the area around the radial hole 4b where the temperature has decreased, causing unevenness in the beam B. Since the beam current exhibits a steep rise characteristic with respect to the cathode temperature, when the cathode temperature is low, the unevenness of the beam becomes significant.

Further, in terms of machining accuracy, the attachment portion between the hole 4b and the support arm 12 is prone to play, and adjustment work when setting or replacing the cathode 4 is troublesome.

This invention was made to solve the above problem.
It is possible to prevent uneven temperature distribution of the block cathode caused by the cathode support structure, and to obtain an electron beam that is more even than before, and also to make it easier to adjust the block cathode when centering or replacing it. The purpose is to provide a beam generator.

[Means to solve the problem]

In order to achieve the above object, the present invention has a configuration in which the cathode of the support arm is attached to the connecting end inserted into the hole, or the hole is tapered so that the two are in linear contact.

[Effect]

In this invention, the connecting end of the support arm and the block cathode are not in surface contact but in linear contact, so the mounting of the block cathode prevents the temperature drop in the hole portion and maintains the temperature distribution of the block cathode in a conventional manner. can be compared and made uniform.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1(a) and 1(bl), 2o is a ring body made of molybdenum Mo, which has an inner diameter larger than the outer diameter of the block cathode 4, and has a radial hole penetrating from the outer circumferential surface to the inner circumferential surface. (Screw holes) 20a are formed at regular intervals in the circumferential direction.The ring body 20 is further formed with holes 20b for screwing the pillars 10 described above.21 is made of tantalum Ta. Or molybdenum Mo
The cathode holder 11 is configured together with the ring body 20, and the hole 20a is formed on the outer peripheral surface of the cathode holder.
A screw is cut into the hole 20a, and the inner end 21A is screwed into the hole 20a so as to protrude.

An inner end 21A of the holder element 21 that protrudes from the inner circumferential surface of the ring body 20 has a hole 21 that opens in the end surface of the inner end 21A.
a is formed. 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 connecting end of which is fitted into the hole 21a of the holder element 21 up to its bottom, and the other connecting end 22A opening into the outer peripheral surface of the block cathode 4. has been incorporated into. The support arm 22 has a diameter larger than the diameter of the mounting hole 4b, and its connecting end 22A is a tapered portion as shown in FIGS. The mounting is engaged with the opening edge of the hole 4b to support the block quad 4.

In this embodiment, as described above, the support arm 22 is attached to the cathode block 4 by simply engaging the opening edge of the hole 4b with the tapered surface of the connecting end 22A, so that the support arm 22 does not come into contact with the cathode block 4. Small area and radial hole 4
Since the amount of insertion into the block cathode 4 is small and the depth of the hole 4b for installation is small, the amount of heat transferred from the block cathode 4 to the support arm 22 is small. Since the mounting reduces the temperature drop around the hole 4b, the temperature distribution of the block quad 4 can be made uniform, and unevenness in the electron beam can be prevented.

Furthermore, since the connecting portion 22A of the support arm 22 is installed by engaging the hole 4b with a tapered bar, the above-mentioned backlash problem is eliminated, making the adjustment work at the time of setting and replacement easier than before, and the installation is easy. There is an advantage that the permissible range of machining accuracy of the hole 4b and the connecting end 22A is increased, and machining costs are reduced.

Further, in the above embodiment, the connecting end 22 of the support arm 22
Although A has a Taber structure, the radial hole 4b may have a Chi-6 structure.

Note that in the conventional cathode support mechanism, the plurality of cathode support arms 12 are individually attached to the cathode holder 1.
1, and each cathode holder 11 is individually set (threaded connection) on the support 10. Therefore, when positioning the cathode 4, it is not necessary to adjust the direction of the cathode holder 11 for each cathode holder. In addition, the protrusion length of the cathode support arm 12 from the cathode holder 11 must be adjusted by loosening or tightening the setscrew 13, and each column 10 is likely to have positional errors. There is a problem in that it takes time and effort to adjust the center of the cathode 4 so that it is aligned with the operation center 0, and the connection part a between the cathode 4 and the cathode support arm 12 becomes high temperature during the operation of the device. Therefore, when replacing the cathode, the cathode holder 11 must be removed from the column 10 by loosening the nut 14 that fixes the column 10 and pulling the upper end outward. Although there was a problem in that a large amount of adjustment time was required before operation could be restarted, the cathode holding mechanism of the above embodiment has a plurality of holder elements 21 that cantilever support the support arms 22, respectively. ring body 20
Since this single ring body 20 is supported by a plurality of supports 10, the holder element 21 can be directed toward the operation center O without adjusting the direction of the holder element 21. Furthermore, there is an advantage that the position of the cathode 4 can be adjusted simply by rotating the holder element 21. Furthermore, in the embodiment described above, since the one connecting end of the support arm 22 does not extend to the inner circumferential surface of the ring body 20, the holder element 21 is rotated to connect the inner end in the radial direction of the ring body 20. When the support arm 22 is almost retracted into the hole 2Oa, the one connecting end of the support arm 22 comes off from both the holder element 21 and the ring body 20, so if the other connecting end 22A of the support arm 22 is stuck to the cathode 4, The cathode 4 can be replaced without removing the ring body 20 from the support IO.

〔Effect of the invention〕

As explained above, this invention has a structure in which the connecting end of the support arm and the block cathode are in linear contact rather than surface contact, so that the connecting end can be inserted into the hole periphery. Since temperature drop can be prevented and the temperature distribution of the block cathode can be made more uniform than before, an even electron beam can be obtained even when the temperature of the block cathode is low. Further, since the support arm and the block cathode are engaged with each other by tabular engagement, there is no problem of engagement backlash, and there is an advantage that setting and replacing the block cathode becomes easier.

[Brief explanation of drawings]

FIGS. 1(a) and (b) show a plan view and a side view of an embodiment of the present invention, respectively, and FIGS. 2+a) and (b) show a plan view and a vertical cross-sectional view of a block cathode of the above embodiment, respectively. 3 is a schematic configuration diagram of a conventional electron beam ordering device, FIG. 4 (a) and (bl) are a plan view and a side view showing a conventional cathode support mechanism, respectively, and FIG. 5 is a diagram showing the conventional example as shown in FIG. It is a longitudinal cross-sectional view showing the engagement state of the block cathode and the support arm in FIG.

Claims (1)

[Claims] The electron beam generator described above accelerates electrons emitted by a hot cathode unit with an electric field by providing an accelerating anode to which an accelerating voltage is applied between the hot cathode unit and irradiates a workpiece with the generated electron beam. The hot cathode unit has a block cathode having a plurality of attachment holes on a side peripheral surface, and the block cathode is supported by a plurality of support arms extending from a fixed part in the device container into the attachment holes of the block cathode. In the electron beam generator, the connecting end portion of the support arm inserted into the mounting hole or the mounting hole has a tapered shape, and the two are in linear contact with each other. Generator.