JP2002022898A - Electron beam irradiator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron beam irradiator of an all-round irradiation type which can be used to harden a resin that covers a core such as an optical fiber. SOLUTION: An intermediate cylindrical electrode 7 with an electron beam passage hole 11 is coaxially placed inside a cylindrical magnet 8 located in a vacuum container 1, and an anode 6 is placed in a central axis. A potential difference is given between the cylindrical magnet 8 and the intermediate cylindrical electrode 7 by a magnetron discharge power source 9 to generate magnetron discharge plasma F. A voltage that is negative to an anode 8 is applied to the intermediate cylindrical electrode 7 by an acceleration power source 10 to jet out electrons in the plasma F from the electron beam passage hole 11 and accelerate them toward the anode 6. A magnetic material is used as a material for the intermediate cylindrical electrode 7 to block a magnetic field leaking into an acceleration space. An optical fiber 4 is irradiated in the atmosphere A by making an electron beam irradiation section of the anode 6 of a titanium thin-wall pipe and running the optical fiber 4 in the center of the pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam irradiation apparatus capable of curing a resin by electron beam irradiation in the production of an optical fiber or an electric wire. The present invention relates to an apparatus capable of costly resin crosslinking. Also, the present invention relates to an improvement in an electron beam irradiation apparatus capable of producing a positive or negative ion of an appropriate element by magnetron plasma, accelerating the element, uniformly injecting the element into the surface of a linear substance, and performing a high-speed surface modification treatment. .

[0002]

2. Description of the Related Art Heretofore, a curing treatment of a coating resin for optical fibers and electric wires has been performed by an ultraviolet irradiation method. Since the energy of ultraviolet irradiation is as small as 3 to 6 eV, a photopolymerization initiator is added as a reaction accelerator to the coating resin of the optical fiber. Since the photopolymerization initiator is expensive, the price of the resin is also expensive. In the ultraviolet curing method, an ultraviolet lamp is used as an ultraviolet light source. This kind of UV lamp is expensive and
It needs to be replaced regularly in about 1000 hours.
Furthermore, since it is necessary to cool the lamp by using a blower to cool it down, there is a problem that a large amount of maintenance is required.

[0003] Until now, the ultraviolet curing method has been used because the technology of the curing method by electron beam irradiation instead of ultraviolet rays has not been established. Conventionally, an electron beam accelerator accelerates substantially linearly. In order to irradiate a linear target with a large amount of electron beam from the azimuth direction, there has been no other method than rotating the sample or rotating the source at a high speed like a CT scanner. For example, in the case of electron beam coating and curing of an electric wire, the electric wire coated with an insulating resin is passed through a predrying oven, then passed through an electron beam irradiation section several times, and the reflected electron beam is also self-irradiated and cured. ing. Utilizing this system for curing optical fibers is not practical due to the size and utility as well as the properties of the optical fibers.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a full-circular irradiation type electron beam irradiation apparatus which can be used for curing a resin for coating a core such as an optical fiber. A discharge plasma having a uniform intensity is produced at a distance of the same radius from the target axis in the azimuthal direction, and this is used as an electron beam source. Next, a high voltage is applied between the electron beam source and a target electrode at a ground potential corresponding to the anode to irradiate the target with an electron beam. The electron beam source has a discharge plasma of uniform intensity in the azimuthal direction by a cylindrical magnetron discharge, and the beam extraction and its transport system are completely coaxial geometrically and axially symmetric, so that the electron In line irradiation, the beam energy and current intensity distribution are necessarily axially symmetric and uniform in the azimuthal direction.

[0005] One of the applications that can make the most of this characteristic is effective for electron beam curing of the resin coating the core of the optical fiber. When a thin and long target to be irradiated is irradiated with an electron beam, the problem is solved by uniformly irradiating an electron beam from the circumferential direction of the sample to the center of the circle and arranging the target at the center of the circle. It can be expected that the maximum processing speed will be obtained among the currently conceivable curing methods.

[0006]

A plasma is created by running a long distance while drifting electrons in orthogonal electric and magnetic fields to ionize residual gas. The plasma generated in this way is called magnetron-type discharge plasma. In the present invention, a magnetron-type discharge plasma is formed into a cylindrical shape and this plasma is used as an electron beam source. An axially parallel magnetic field is generated using a cylindrical magnet, and a cylindrical intermediate electrode is arranged coaxially with the magnetic field inside the magnet. When a high voltage is applied between the cylindrical magnet and the cylindrical electrode disposed coaxially inside the magnet, a circular magnetron discharge is ignited in the gap between the cylindrical magnet and the cylindrical electrode. The cylindrical electrode has many holes so that electrons can accelerate to the center of the cylindrical electrode. A conductive rod is arranged at the center on the concentric axis of the cylindrical electrode, and when an accelerating voltage is applied so that this rod becomes an anode for the cylindrical electrode, the electron beam is accelerated toward the central anode rod . For the purpose of curing the resin of the optical fiber, it is possible to irradiate the optical fiber with an electron beam with extremely uniform distribution by making the anode rod into a pipe and making it work so that the optical fiber can pass therethrough.

A magnetron discharge as a charged particle source is
Electrons drift in the ionization space narrowed by the magnet and the cylindrical electrode while trochoidally moving in the circumferential direction. By the time one electron ionizes the atmospheric gas, the electron must circulate in this ionization space in the circumferential direction almost infinitely. In this way, a plasma having uniform intensity is formed in the circumferential direction. This is an important discharge mechanism for extracting a beam of uniform intensity from the complete circumference in the azimuthal direction.

[0008] A large number of holes are formed in a circumferential direction in a portion of the intermediate cylindrical electrode which is in contact with the magnetron discharge plasma.
The shape of the hole is a circle or a corner or an oval, through which electrons are sent into the acceleration space. Instead of the holes, a pair of cylindrical electrodes may be arranged coaxially while keeping a distance. In the case of electron acceleration, it is necessary to bridge the gap between the two cylindrical electrodes so that no magnetic field is generated.

A major feature of the magnetron plasma electron gun is that electrons are directly extracted from the plasma by the residual gas, so that a troublesome filament is not used. There is no failure in cutting the filament, making maintenance easier. It operates at a low vacuum of about two orders of magnitude (about 0.1 Pa) compared to the filament type. This enables differential pumping, and works effectively for machines that need to operate stably for a long time, such as optical fibers.

[0010]

FIG. 1 shows the principle of irradiating a linear target with an electron beam from a cylindrical magnetron discharge plasma. The electron gun and the electron beam generator C are arranged in the vacuum vessel 1 and electrons are generated and accelerated in a vacuum B atmosphere evacuated by the vacuum pump 2. An intermediate cylindrical electrode 7 having an electron passage 11 is provided coaxially inside a cylindrical magnet 8. The anode 6 is coaxially arranged on the center axis of the intermediate cylindrical electrode. When a potential difference is applied between the cylindrical magnet 8 and the intermediate cylindrical electrode 7 by the magnetron discharge power supply 9, a magnetron discharge plasma F is generated. The anode 6 is electrically connected to the vacuum vessel 1 in a pipe shape and is grounded. When a negative voltage is applied to the anode of the intermediate cylindrical electrode by the acceleration power source 10, electrons in the magnetron discharge plasma are ejected from the electron beam passage opening of the intermediate cylindrical electrode and accelerated toward the anode. The cylindrical electrode is made of a magnetic material and has a thickness sufficient to block a magnetic field from a charged particle source leaking into the acceleration space. This is crucial for the invention to work. This is because even if a slight leakage magnetic field exists in the acceleration space, the magnetron discharge is caused there even if it is several gauss.

Anode 6 (target electrode 12) in this configuration
Is a pipe shape assuming electron beam curing of the optical fiber coating resin. When the electron beam irradiating section is made of a metal mesh, the electron beam penetrates the metal mesh and directly irradiates the optical fiber 4, so that efficient electron beam irradiation can be performed. However, in this case, it is necessary to make the pipe of the anode 6 thinner and to make the vacuum pump 2 stronger so that the electron beam generator C is differentially evacuated. The electron beam irradiating part of the anode 6 is made of a thin titanium pipe, and the center of the pipe adopts the optical fiber tunnel 3 system in which the optical fiber 4 runs so that the optical fiber of the object to be irradiated can be irradiated in the atmosphere A. In this case, since the electron beam is largely scattered by the thin pipe, the thickness of the pipe needs to be several μm.

FIG. 2 shows a model when the resin of an optical fiber is cured by electron beam in an inverse plasma discharge electron beam irradiation apparatus. The optical fiber 4 is irradiated with the electron beam from the atmosphere A through the fiber tunnel 3 at the electron beam irradiation section C, and exits the atmosphere A again through the exit fiber tunnel 3. In this case, the electron beam irradiating section C is housed in a vacuum vessel 1 and differentially evacuated by a powerful vacuum pump 2.

The electron beam irradiating section C is provided with an intermediate cylindrical electrode 7 having an electron beam passing port 11 coaxially inside a cylindrical magnet 8 and applying a voltage of a magnetron discharge power supply 9 during this interval to apply magnetron discharge plasma. F occurs. By applying the voltage of the acceleration power supply 10 between the intermediate cylindrical electrode 7 and the anode 6, the electron beam is accelerated from the circumferential direction in the acceleration space E and is intensively irradiated toward the anode 6. By pulsing the acceleration voltage and applying the pulse voltage, beam interruption due to abnormal discharge can be largely avoided.

A PIG ion source 14 is arranged at the center of the pair of anodes 6 through which the optical fiber passes, and ions are ejected from the optical fiber passage hole to the electron beam irradiation section, thereby preventing charge-up of the optical fiber and preventing the optical fiber from being charged up. Facilitates electron beam irradiation on PIG ion source 1
When providing 4, the metal mesh 13 is unnecessary. On the other hand, it has the role of releasing and exhausting dust that causes sublimation from the optical fiber due to the effect of the ejected plasma and causes abnormal acceleration voltage in the acceleration space. The PIG ion source 14 installed at opposing positions in the two anodes is composed of a PIG element ion source electrode, a power supply for applying a high voltage to these electrodes, and a magnet.

FIG. 3 is a bench test of electron beam irradiation to prove the present invention. In the experiment, the electron beam irradiation section C and the electron beam irradiation area D were placed in the vacuum vessel 1, and after evacuation, air and hydrogen were used as atmosphere gases at a gas pressure of 0.2 Pa and the discharge voltage was fixed at 2 KV. A 1 mmφ tungsten rod was provided on the anode 6 on the center axis of the intermediate cylindrical electrode 7. When the magnetron discharge voltage is applied, the magnetron discharge plasma F stands in the gap between the permanent magnet (cylindrical magnet 8) and the magnetic intermediate electrode 7, and when an acceleration voltage is applied between the anode 6 and the intermediate cylindrical electrode 7, the electrons become anode. Is irradiated.

FIG. 4 is a plot of the relationship between the acceleration voltage and the target current yield (acceleration current) in FIG. In the figure, V _A is an acceleration voltage, I _A is an acceleration current, I _C is a magnetron discharge current, and V _C is a magnetron discharge voltage.
KV and the atmospheric gas pressure was fixed at 0.2 Pa. Figure AIR if discharge gas is air, H ₂ is the case of hydrogen. The intermediate cylindrical electrode 7 is made of iron and has an inner diameter of 58 mm.
About 22 holes of mφ are bored on the same diameter surface at equal intervals in the circumferential direction. As shown in FIG. 4, it can be seen that despite the fact that the target diameter is much smaller than the inner diameter of the cylindrical electrode, the electron beam collection efficiency of the target reaches about 10%. This proves that a high-intensity beam current can be efficiently irradiated to a small area, and the application of the present invention to material irradiation, nuclear fusion, a high-intensity neutron generator, etc. besides electron beam irradiation is promising. Suggest that.

[0017]

As described above, an all-round irradiation type electron beam irradiation apparatus capable of irradiating an electron beam with extremely uniform distribution to an optical fiber, an electric wire or the like is obtained, and is relatively inexpensive and has excellent work efficiency. An irradiation device is obtained.

[Brief description of the drawings]

FIG. 1 is a view showing the principle of electron beam irradiation on a linear target by a cylindrical magnetron discharge plasma according to the present invention.

FIG. 2 is a view showing a model when the resin of an optical fiber is cured with an electron beam in an inverse plasma discharge electron beam irradiation apparatus.

FIG. 3 is a model diagram of a bench test.

FIG. 4 is a diagram showing a relationship between an acceleration voltage and an acceleration beam current when a discharge gas pressure and a discharge voltage are kept constant.

[Explanation of symbols]

 A Atmosphere B Vacuum C Electron beam irradiation section D Electron beam irradiation area E Acceleration space F Magnetron discharge plasma 1 Vacuum container 2 Vacuum pump 3 Optical fiber tunnel 4 Optical fiber 6 Anode 7 Intermediate cylindrical electrode (magnetic material) 8 Cylindrical magnet 9 Magnetron discharge power supply Reference Signs List 10 Acceleration power supply 11 Electron beam passage opening 12 Target electrode (irradiation target) 13 Metal mesh 14 PIG ion source

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G21K 5/10 G21K 5/10 L H01B 13/14 H01B 13/14 Z (72) Inventor Kiichi Eto Tokyo 1-18-15 Omorinishi, Ota-ku, Tokyo F-term in Taiyo Materials Co., Ltd. (Reference) 2H050 BA12 BA17 BA21 5G325 JB12 JB17

Claims (5)

[Claims] An intermediate cylindrical electrode having a charged particle passage opening inside a cylindrical magnet in a vacuum is coaxially arranged, and a potential difference is provided between the cylindrical magnet and the intermediate cylindrical electrode to form the cylindrical magnet and the cylindrical magnet. A magnetron discharge plasma is generated in the gap between the intermediate cylindrical electrodes, and a cylindrical or rod-shaped target electrode is disposed coaxially with the center axis of the intermediate cylindrical electrode, and a high voltage is applied between the target electrode and the intermediate cylindrical electrode. An electron beam irradiation apparatus characterized in that by applying the voltage, electrons or ions existing in the magnetron discharge plasma are accelerated toward a target electrode provided on a central axis. 2. The method according to claim 1, wherein when the object to be irradiated is an insulator such as an optical fiber, the object is placed on a central axis of a cylindrical metal mesh or graphite mesh, and the mesh is used as an anode. Electron beam irradiation equipment for optical fiber production. 3. The method according to claim 2, wherein the tubular mesh is made of a metal thin film and the tubular thin film is used as an air / vacuum partition, and the outer surface of the tube is exposed to a vacuum environment and the inner surface of the tube is placed in an atmosphere of atmospheric pressure or reduced pressure. Characteristic electron beam irradiation equipment for optical fiber production. 4. An electron beam irradiation apparatus for an optical fiber which is an object to be irradiated, by discharging ions generated by discharging a residual gas to an irradiation unit to prevent charge-up of the object to be irradiated and to prevent the object from being charged. The electron beam irradiation apparatus for manufacturing an optical fiber according to claim 1, wherein a PIG ion source is incorporated in the anode for the purpose of capturing dust contained therein. 5. The electron beam according to claim 1, wherein a magnetic material is used as an intermediate cylindrical electrode material in contact with an acceleration space of the magnetron discharge electrode to eliminate a magnetic field near the target electrode. Irradiation device.