JP2805852B2 - Electron beam generator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electron beam generator used for melting metals and the like.

[Conventional technology]

FIG. 3 shows a conventional electron beam generator of this type. In FIG. 1, reference numeral 1 denotes a vacuum vessel, which is a first vessel section 20 for partitioning a first chamber A for accommodating a cathode unit 4 composed of a filament 2, a Wehnelt electrode 3 and the like, and an anode 5 serving as an acceleration electrode. A first passage section 21 that is downstream of the first chamber A and that divides the first beam path R1 and a second section (intermediate chamber) B that is continuous with the first chamber A via the first beam path R1. A second container portion 22, a second passage portion 23 downstream of the second chamber B and defining a second beam passage R2;
A third chamber (processing chamber) C which is continuous with the second chamber B via the second beam path R2; and has a third container section 24. The first container section 20, the second container section 22, The third container part 24 has exhaust ports 20A, 22A and 24A, respectively, and the valves 20B, 22B, 24B
Are connected to exhaust vacuum pumps P1, P2 and P3 through lines 20C, 22C and 24C having Reference numerals 6 and 7 denote convergent lenses (magnetic lenses), which are disposed around the first passage 21 and the second passage 23. 8 is a deflection lens, 9
Is a crucible and 10 is a metal to be treated. Reference numeral 11 denotes a viewing window, in which a window frame 13 also serving as a seal is attached to a window hole 12 formed in the side wall of the second container 22, and a glass 14 having a large thickness is attached to the window frame 13.
Is formed.

In this configuration, when a current is caused to flow through the filament 2 of the cathode unit 4 to generate thermoelectrons, the generated thermoelectrons are accelerated toward the anode 5 by an electric field between the filament and the anode, and are converged by the converging lens 6. , From the beam path R1 to the second chamber B, and further passes through the beam path R2 and enters the third chamber C while being converged by the converging lens 7 to be processed (in this example, a molten metal).
Irradiated at 10.

[Problems to be solved by the invention]

In the vacuum vessel 1 of the electron beam generator, a viewing window 11 for visually confirming the state of the generated electron beam is formed. Therefore, an external magnetic field such as terrestrial magnetism cannot be completely shielded, and the electron beam passing through the second chamber B is deviated from the axis of the second chamber B due to the influence of the external magnetic field. A situation occurs in which the bottom of the second container 22 is irradiated without going straight into R2.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and has as its object to provide an electron beam generator that can eliminate the influence of an external magnetic field that enters through a viewing window.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a net-like magnetic material for shielding an external magnetic field inside or outside a viewing window. In claim 2, this magnetic material is disposed concentrically with a room, The inside is a cylinder through which the electron beam passes.

[Action]

In the present invention, since a magnetic material is provided outside the viewing window or between the window and the electron beam to perform magnetic shielding, the effect of an external magnetic field on the electron beam is removed, and the magnetic material is reticulated. The state of the electron beam can be seen through the magnetic material and the viewing window.

〔Example〕

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

In FIG. 1, reference numeral 15 denotes a cylindrical body made of a wire mesh, which is disposed in the second container 22 concentrically with the axis of the second container 22, and is attached to an upper wall 18U of the second container 22 by an upper mounting portion 16. The lower container 17 is fixed to the lower wall 18D of the second container 22 by the lower mounting portion 17. The cylindrical body 15 has a diameter that is not smaller than the diameters of the beam paths R1 and R2.

In this configuration, since the external magnetic field that has entered the second chamber B through the viewing window 11 is magnetically shielded by the cylindrical body 15, the cylindrical body 15
It does not affect the electron beam passing through it. Further, since the cylindrical body 15 is a wire mesh, the cylindrical body is
Through 15 it is possible to see the state of the electron beam.

In this embodiment, a cylindrical wire mesh, which is a magnetic material, is provided in the second chamber B. However, as shown in FIG.
The same effect can be obtained by covering the outside or inside of the glass 14 with the wire mesh 19.

〔The invention's effect〕

As described above, according to the present invention, by arranging the net-like magnetic material outside or inside the viewing window, the external magnetism can be shielded by this magnetic material. Can be reliably prevented from being performed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view showing a second embodiment of the present invention, and FIG. 3 is a sectional view showing a conventional electron beam generator. 4 ... cathode unit, 5 ... anode, 11 ... viewing window, 14 ... glass, 15 ... cylindrical magnetic material, 19 ... wire mesh,
20 first container portion, 21 first passage portion, 22 second container portion, 23 second passage portion, 24 third container portion,

──────────────────────────────────────────────────続 き Continued on the front page (56) References Japanese Utility Model 1-86053 (JP, U) Japanese Utility Model 57-80062 (JP, U) Japanese Utility Model Utility Model 61-59825 (JP, U) (58) Survey Field (Int.Cl. ⁶ , DB name) H01J 37/305 H01J 37/16 H01J 37/06-37/07

Claims (2)

(57) [Claims] 1. A vacuum vessel comprising a first container section defining a first chamber, a second container section defining a downstream chamber, and a beam passage section interposed between the two container sections and surrounded by a converging lens storage chamber. An electron beam generator that houses a cathode unit for generating thermoelectrons and an anode to which an accelerating voltage is applied in the first chamber, and an object to be processed that receives electron beam irradiation in the downstream chamber. 3. The electron beam generator according to claim 1, wherein the second container has a viewing window on a side wall thereof, and a reticulated magnetic body for shielding an external magnetic field is provided inside or outside the viewing window. 2. The electron beam generator according to claim 1, wherein the inner reticulated magnetic body is a concentrically disposed cylindrical body through which the beam passes.