JP2012052909A - Electric discharge tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric discharge tube capable of reducing loss due to a voltage applied to an electrode, or direct-current discharge of energy, and capable of more efficiently accelerating an electron.SOLUTION: An electric discharge tube 1 has a tube body 11, an electron supply port 12, an equipment connection port 13 and an electrode for electron acceleration 41. The tube body 11 is formed in tubular shape and has an electric wire 8 for radiating an electron running inside the tube body. The electron supply port 12 generates plasma inside it and supplies an electron to the tube body 11. The equipment connection port 13 has an exhaust system installed, and evacuates air from, and depressurizes, the tube body 11. The electrode for electron acceleration 41 is disposed in the tube body 11 and accelerates the electron supplied in the tube body 11. The inner surface 11a of the tube body 11 in the proximity of the electrode for electron acceleration 41 is flatly formed with a smooth surface.

Description

  The present invention relates to a discharge tube used in, for example, an electron beam irradiation apparatus.

  An electric wire including a core wire and a covering portion that covers the core wire may be irradiated with electrons for surface modification of the covering portion. By irradiating the electric wire with electrons, the cross-linking reaction of the synthetic resin constituting the covering portion is promoted on the outer surface (outer surface layer) of the covering portion, and the heat resistance and mechanical properties of the covering portion are improved.

  As described above, for example, an electron beam irradiation apparatus described in Patent Document 1 is known as an apparatus for irradiating an electric wire with electrons. This electron beam irradiation apparatus includes a microwave generation unit, a plasma generation unit, and a discharge tube. The microwave generation unit includes a solid state oscillator or the like, and generates a microwave. The plasma generation unit includes a surftron or the like, and propagates the microwave from the microwave generation unit to the discharge tube to generate plasma in the discharge tube.

  As shown in FIG. 5, the discharge tube 101 includes a hollow columnar tube body 111 extending in the vertical direction in FIG. 5, a cylindrical electron supply port 112 extending from the bottom wall of the tube body 111, and a tube body. A cylindrical wire support port 116 extending from the peripheral wall 111 and a device connection port (not shown) are provided. The internal spaces of the electron supply port 112, the wire support port 116, and the device connection port communicate with the internal space of the tube main body 111.

  A gas such as argon gas is supplied into the electron supply port 112. The electron supply port 112 is positioned in a surftron not shown, and generates argon plasma therein. A pair of electric wire support ports 116 are provided to extend outward from the tube body 111 from portions facing each other across the axis of the tube body 111 on the peripheral wall. The electric wire 108 moves over one electric wire support port 116, the tube main body 111, and the other electric wire support port 116.

  The device connection port is orthogonal to the wire support port 116. A pair of device connection ports are provided to extend outward from the pipe body 111 from portions facing each other across the axis of the pipe body 111 on the peripheral wall. One device connection port is connected to an exhaust device as a decompression device via a gauge port, and exhausts the inside of the device connection port, that is, the inside of the pipe body 111 to reduce the pressure.

  Further, in the tube body 111 described above, an electron acceleration electrode 141 disposed near the upper wall of the tube body 111 and applied with a high voltage, and a negative voltage applied so as to cover the electron supply port 112. The first mesh electrode 142 and the second mesh electrode 143 arranged between the electron acceleration electrode 141 and the first mesh electrode 142 and in the vicinity of the first mesh electrode 142 and grounded are attached.

  In the discharge tube 101 having the above-described configuration, the inside of the tube main body 111 is decompressed by the exhaust device, so that the plasma generated in the electron supply port 112 is drawn from the electron supply port 112 into the tube main body 111. Then, argon ions in the plasma are captured by the first mesh electrode 142. The electrons in the plasma pass through the first mesh electrode 142 and are extracted from the plasma by the second mesh electrode 143, and are accelerated along the arrow E toward the electron acceleration electrode 141 by the electron acceleration electrode 141. Is done. Then, the accelerated electrons are irradiated to the moving electric wire 108 as described above.

JP 2009-53188 A

  In the above-described tube main body 111 of the discharge tube, the electrode for electron acceleration 141 is disposed in the vicinity of the upper wall, and the wire support port 116 and the device connection port extend from the peripheral wall. Therefore, a step is formed on the upper wall of the tube main body 111 and the wire support port 116 in FIG. 5, and a recess 117 is formed in the vicinity of the electron acceleration electrode 141. Then, when the inside of the tube body 111 is exhausted, the argon gas tends to stay in the recess 117.

  When a high voltage is applied to the electron acceleration electrode 141 while the argon gas remains in the recess 117, a direct current discharge occurs due to the argon gas in the recess 117, and a part of the voltage, that is, energy applied to the electron acceleration electrode 141 is reduced. There is a problem that the electrons are consumed by direct current discharge and the electrons cannot be accelerated sufficiently.

  The present invention aims to solve such problems. That is, an object of the present invention is to provide a discharge tube that can accelerate electrons more efficiently by reducing a loss caused by direct current discharge of a voltage, that is, energy applied to an electrode.

  In order to solve the above-described problems and achieve the object, the invention described in claim 1 is formed in a cylindrical shape, and a tube main body through which an object to be irradiated for irradiating electrons passes, An exhaust port for depressurization, an electron supply port for supplying the electrons into the tube main body, and an electrode arranged in the tube main body for accelerating the electrons supplied into the tube main body. The discharge tube is characterized in that the inner surface of the tube main body in the vicinity of the electrode is formed flat by a smooth surface.

  According to a second aspect of the present invention, in the discharge tube according to the first aspect, an insulating coating layer is provided which covers the surface of the electrode support that is connected to the electrode and applies a voltage to the electrode. This is a discharge tube characterized by

  According to the first aspect of the present invention, since the inner surface of the tube body is formed flat by a smooth surface, the gas in the tube body stays in the vicinity of the electrode when the tube body is exhausted. There is nothing. For this reason, when a high voltage is applied to the electrodes, direct current discharge due to the retained gas is less likely to occur. The voltage applied to the electrode, that is, energy, is not easily consumed by the direct current discharge, and is consumed for accelerating the electrons. Therefore, energy loss can be reduced and electrons can be accelerated more efficiently.

  According to the invention described in claim 2, since the surface of the electrode support is covered with the coating layer, direct current discharge on the surface of the electrode support can be prevented. For this reason, when a high voltage is applied to the electrodes, direct current discharge is less likely to occur. The voltage applied to the electrode, that is, energy, is not easily consumed by the direct current discharge, and is consumed for accelerating the electrons. Therefore, energy loss can be reduced and electrons can be accelerated more efficiently.

It is explanatory drawing explaining the structure of the electron beam irradiation apparatus provided with the discharge tube concerning one Embodiment of this invention. It is a perspective view which shows the discharge tube shown by FIG. It is a graph which shows the presence or absence of generation | occurrence | production of DC discharge at the time of changing an acceleration voltage. It is a graph which shows the progress of the bridge | crosslinking reaction of the electric wire at the time of changing an acceleration voltage. It is sectional drawing which shows the conventional discharge tube.

  Hereinafter, a discharge tube according to an embodiment of the present invention will be described with reference to FIGS. The discharge tube 1 shown in FIG. 2 etc. concerning one Embodiment of this invention is used for the electron beam irradiation apparatus 10 shown in FIG.

  The electron beam irradiation apparatus 10 is an apparatus that irradiates electrons to an electric wire 8 as an object to be irradiated, for example. The electron beam irradiation apparatus 10 of this embodiment generates plasma and accelerates electrons in the plasma to irradiate the electric wire 8. By irradiating the electric wire 8 with electrons, the cross-linking reaction of the synthetic resin constituting the covering portion is promoted on the outer surface (outer surface layer) of the covering portion, and the heat resistance and mechanical properties of the covering portion are improved.

  The electric wire 8 is a so-called covered electric wire and has a circular cross section. The electric wire 8 includes a conductive core wire and an insulating covering portion that covers the core wire. The core wire is made of a metal material such as copper or a copper alloy. The covering portion is made of a synthetic resin such as a polyethylene resin, a polypropylene resin, or a polyvinyl chloride resin. If necessary, additives such as a crosslinking aid, an antioxidant, a copper damage inhibitor and a flame retardant are added to the synthetic resin.

  As shown in FIG. 1, the electron beam irradiation apparatus 10 includes a microwave generator 2, a plasma generator 3, and a discharge tube 1. The microwave generation unit 2 includes a solid state oscillator 21 and a double slag tuner 22 connected to the solid state oscillator 21 by a coaxial cable 23. The solid state oscillator 21 includes an oscillator body, an amplifier, and an isolator. The solid state oscillator 21 generates a microwave (1 to 100 GHz) and propagates the microwave to the double slag tuner 22 via the coaxial cable 23.

  The double slag tuner 22 matches the impedance of the microwave from the solid state oscillator 21. That is, the double slag tuner 22 optimizes the power supplied to the plasma generating unit 3 by adjusting the reflected power from the plasma generating unit 3 to the minimum value, and efficiently propagates the microwave to the plasma generating unit 3. .

  The plasma generating unit 3 includes a surftron 31 connected to the double slag tuner 22 described above via a coaxial cable 32. Surfertron 31 is made of a metal material. The surfertron 31 includes a flat donut-shaped bottom wall 31a, a cylindrical outer cylinder portion 31b erected from the outer edge of the bottom wall 31a, a cylindrical inner cylinder portion 31c erected from the inner edge of the bottom wall 31a, The upper wall 31d is connected to the tip of the outer cylinder part 31b, has the same shape as the bottom wall 31a and is arranged in parallel with the bottom wall 31a, and the movable part 31e accommodated in the outer cylinder part 31b.

  A coaxial cable 32 connected to the double slag tuner 22 is attached to the outer cylinder portion 31b. The coaxial cable 32 penetrates the outer wall of the outer cylinder part 31b, and the end part protrudes into the outer cylinder part 31b. The coaxial cable 32 propagates the microwave into the outer cylinder portion 31b.

  The inner cylinder part 31c is arranged in the outer cylinder part 31b, and is arranged coaxially with the outer cylinder part 31b. The inner cylinder part 31c is formed slightly shorter than the outer cylinder part 31b, and the tip of the inner cylinder part 31c forms a gap 31f with the upper wall 31d. Moreover, the inner side of the inner cylinder part 31c is connected with external space. The inner cylinder portion 31c positions an electron supply port 12 described later of the discharge tube 1 on the inner side. As described above, the microwave propagated in the outer cylinder portion 31b propagates to the outer surface of the electron supply port 12 disposed in the inner cylinder portion 31c through the gap 31f described above.

  The movable part 31e is formed in a flat plate donut shape, and is arranged in a space between the outer cylinder part 31b and the inner cylinder part 31c. Leaf spring-like shield fingers (not shown) made of copper are attached to the outer peripheral surface and inner peripheral surface of the movable portion 31e. The shield finger attached to the outer peripheral surface of the movable portion 31e is in contact with the inner surface of the outer cylindrical portion 31b, and the shield finger attached to the inner peripheral surface of the movable portion 31e is in contact with the outer surface of the inner cylindrical portion 31c. Prevent leakage.

  The movable portion 31e is provided so as to be movable along the axial direction of the outer cylindrical portion 31b and the inner cylindrical portion 31c (that is, the axial direction of the surftron 31). The movable portion 31e moves in the axial direction to achieve microwave impedance matching. That is, the movable portion 31e optimizes the power supplied to the electron supply port 12 in the inner cylinder portion 31c by finely adjusting the reflected power to the microwave generation unit 2, and applies the microwave to the electron supply port 12. Propagate efficiently.

  The discharge tube 1 is made of quartz, glass, ceramics or the like. As shown in FIG. 2, the discharge tube 1 integrally includes a tube body 11, an electron supply port 12, a device connection port 13, an electron acceleration electrode support portion 14, and a mesh electrode support portion 15. .

  The tube body 11 is formed in a cylindrical shape (tubular shape). The inner surface 11a of the tube body 11 is formed flat with a smooth surface throughout. Of course, the inner surface 11a is also formed flat by a smooth surface even in the vicinity of an electron acceleration electrode 41 described later. In this specification, the “smooth surface” means a surface having no ridgeline. In this specification, “flat” includes both a flat surface and a curved surface. In the present embodiment, the inner surface 11a is of course a curved surface. Thus, when the inner surface 11a is formed to be smooth and flat, no gas stays when the inside of the tube body 11 is evacuated and decompressed. That is, retention of argon gas or the like, which will be described later, in the tube body 11 can be prevented, and direct current discharge due to the retained argon gas can be prevented.

  The tube body 11 is arranged in a direction orthogonal to the axial direction of the surftron 31. The tube body 11 accommodates an electron acceleration electrode 41, a first mesh electrode 42, and a second mesh electrode 43, which will be described later, inside. Further, the tube body 11 passes the electric wire 8 inward along the longitudinal direction of the tube body 11. The longitudinal direction of the tube body 11 and the longitudinal direction of the electric wire 8 are parallel. At both end portions 11 b and 11 c of the tube main body 11, an electric wire moving portion 7 (FIG. 1) described later that moves the electric wire 8 in the tube main body 11 along the longitudinal direction of the electric wire 8 is provided.

  The electron supply port 12 is provided at the center in the longitudinal direction of the tube main body 11. The electron supply port 12 includes a hole that penetrates the outer wall of the tube body 11 and a cylindrical portion that extends from the outer edge of the hole toward the inside and outside of the tube body 11. The cylindrical portion extends in a direction orthogonal to the longitudinal direction of the tube body 11. One end portion arranged outside the tube main body 11 of the cylindrical portion is longer than the other end portion arranged inside the tube main body 11 of the cylindrical portion. One end of the cylindrical portion is accommodated in the inner cylindrical portion 31c with a slight gap (about 0.5 mm) from the inner surface of the inner cylindrical portion 31c of the surftron 31.

  A stainless steel tube 16 for supplying argon gas is connected to the tip of the cylindrical portion on the one end side through a gauge port 12a (FIG. 1). A small amount of argon gas (about 2.7 to 6.7 Pa) is supplied into the electron supply port 12 through the stainless steel tube 16.

  The inside of the cylindrical portion described above is exhausted and depressurized by an exhaust device described later connected to the device connection port 13. Then, a microwave propagates from the surftron 31 to the outer surface of the cylindrical portion, and this microwave is applied to the argon gas in the cylindrical portion, and the argon gas is ionized to generate plasma. Plasma generated in the cylindrical portion (that is, electrons in the plasma) is supplied into the tube body 11 through the hole of the electron supply port 12.

  A plasma focusing magnet (not shown) is attached to the outer periphery of the electron supply port 12. The plasma focusing magnet converges the plasma and prevents the plasma from colliding with the outer wall of the tube body 11 and being lost. Then, the electrons in the plasma supplied into the tube main body 11 are accelerated along a direction indicated by an arrow E parallel to the longitudinal direction of the cylindrical portion. An arrow E forms a direction E in which electrons are accelerated.

  The plasma is composed of Ar + (hereinafter referred to as argon ions), electrons, argon atoms, argon radicals, and the like. In this embodiment, argon gas is ionized to generate plasma, but helium, oxygen, nitrogen, or the like can also be used.

  A pair of device connection ports 13 are provided closer to both ends 11b and 11c of the tube body 11 than the electron supply port 12, respectively. The pair of device connection ports 13 are provided side by side along the longitudinal direction of the tube main body 11. The device connection port 13 includes a hole penetrating the outer wall of the tube main body 11 and a cylindrical portion erected from the outer edge of the hole toward the outside of the tube main body 11. The cylindrical portions of the pair of device connection ports 13 protrude from the pipe body 11 in the same direction. These cylindrical portions extend along a direction orthogonal to the longitudinal direction of the tube main body 11 and a direction orthogonal to the direction E for accelerating electrons.

  A grounded gauge port 13a is attached to the tip of these cylindrical portions. One device connection port 13 is connected to an exhaust device (not shown) via a gauge port 13a. One device connection port 13 is an exhaust port described in the claims. The other device connection port 13 is connected to a vacuum gauge sensor (not shown) via a gauge port 13a.

  The electron acceleration electrode support 14 is formed in a cylindrical shape and protrudes from the outer surface of the tube body 11. The electrode 41 for electron acceleration is provided in the center of the tube main body 11 in the longitudinal direction, and is provided on the opposite side of the electron supply port 12 with the axis of the tube main body 11 interposed therebetween. The electron acceleration electrode support portion 14 protrudes from the tube body 11 in a direction parallel to the longitudinal direction of the electron supply port 12 (direction E for accelerating electrons). The electron acceleration electrode support section 14 supports the electron acceleration electrode 41 by passing the support 41 a of the electron acceleration electrode 41 inside. Note that the tip of the electron acceleration electrode support 14 is kept airtight.

  The mesh electrode support portion 15 is formed in a cylindrical shape and protrudes from the outer surface of the tube body 11. The mesh electrode support portion 15 is provided at the center in the longitudinal direction of the tube body 11, and is provided between the electron supply port 12 and the electron acceleration electrode support portion 14 in the circumferential direction of the tube body 11. A pair of mesh electrode support portions 15 are provided so as to position the axis of the tube main body 11 therebetween, and protrude from the tube main body 11 in opposite directions. The pair of mesh electrode support portions 15 protrudes in a direction orthogonal to the direction E in which electrons are accelerated.

  One mesh electrode support 15 supports the first mesh electrode 42 by passing the support 42 a of the first mesh electrode 42 inward. The other mesh electrode support portion 15 is provided closer to the electron acceleration electrode support portion 14 than the one mesh electrode support portion 15. The other mesh electrode support 15 supports the second mesh electrode 43 by passing the support 43 a of the second mesh electrode 43 inward. Note that the tips of these mesh electrode support portions 15 are kept airtight.

  The tube main body 11 of the discharge tube 1 described above accommodates an electron acceleration electrode 41 (corresponding to an electrode described in claims), a first mesh electrode 42, and a second mesh electrode 43. That is, the discharge tube 1 includes an electron acceleration electrode 41, a first mesh electrode 42, and a second mesh electrode 43.

  The electron acceleration electrode 41 is formed in a disk shape and is arranged in a direction orthogonal to the direction E for accelerating electrons. The electron acceleration electrode 41 is provided on the opposite side of the electron supply port 12 with the axis of the tube main body 11 interposed therebetween. At the center of one outer surface of the electron acceleration electrode 41, a support column 41a as an electrode support is erected. The support column 41a is made of tungsten and is formed in a thin cylindrical shape. The support 41a passes through the electron acceleration electrode support 14 and has a tip protruding into the external space. The electron acceleration electrode 41 is connected to a DC voltage power source 51 through a support column 41a (FIG. 1). Electron accelerating electrode 41 is applied with a high voltage (about 30 kV) by DC voltage power supply 51, and accelerates electrons that have entered tube body 11 along arrow E.

  Further, the surface of the portion of the support column 41 a disposed in the tube body 11 is covered with the coating layer 44. The coating layer 44 is made of an insulating material, and is made of glass in this embodiment. The coating layer 44 covers the support column 41a, thereby preventing a direct current discharge from being generated on the surface of the support column 41a when a high voltage is applied to the electron acceleration electrode 41.

  The first mesh electrode 42 is formed in a disc shape with a net body, and is provided so that electrons or the like can pass through the gaps of the net body. The first mesh electrode 42 is made of stainless steel, tungsten, or the like. Tungsten is preferred because it can more reliably prevent sputtering of the electrode surface by argon ions. In the present embodiment, the first mesh electrode 42 is composed of a mesh body having a wire diameter of 0.03 mm, a spacing of 5 mm, and 400 mesh, and is composed of SUS304 (stainless steel containing Cr 18% and Ni 8%). The first mesh electrode 42 is formed with an outer diameter larger than the inner diameter of the cylindrical portion of the electron supply port 12. The first mesh electrode 42 is disposed in parallel with the electron acceleration electrode 41 and is disposed so as to cover the opening of the cylindrical portion disposed in the tube main body 11 of the electron supply port 12.

  Further, struts 42 a extending outward from the first mesh electrode 42 are connected to the outer edge of the first mesh electrode 42. The support column 42a is made of tungsten and is formed in a thin cylindrical shape. The support 42a passes through the mesh electrode support 15 described above, and the tip protrudes into the external space. The first mesh electrode 42 is connected to the direct-current variable voltage power source 52 through the support 42a (FIG. 1). A negative voltage (about −10 V to −100 V) is applied to the first mesh electrode 42 by the DC variable voltage power source 52. The voltage applied to the first mesh electrode 42 is set to a value that captures positively charged argon ions and passes negatively charged electrons, as will be described later.

  Since the second mesh electrode 43 is made of the same material as that of the first mesh electrode 42, the description regarding the material is omitted. The second mesh electrode 43 is formed to have an outer diameter larger than the outer diameter of the first mesh electrode 42, and has an outer diameter substantially equal to the outer diameter of the electron acceleration electrode 41. The second mesh electrode 43 is disposed between the electron acceleration electrode 41 and the first mesh electrode 42, and is disposed in the vicinity of the first mesh electrode 42. The second mesh electrode 43 is arranged in parallel with the electron acceleration electrode 41 and the first mesh electrode 42.

  In addition, the outer edge of the second mesh electrode 43 is connected to a column 43 a extending outward from the second mesh electrode 43. The support 43a is made of tungsten and is formed in a thin cylindrical shape. The support 43a passes through the mesh electrode support 15 described above, and the tip protrudes into the external space. The tip of this support 43a is grounded. For this reason, the second mesh electrode 43 is grounded. The second mesh electrode 43 provides a reference potential for accelerating electrons. The second mesh electrode 43 extracts only electrons from the plasma attracted to the tube body 11 and allows only the electrons to pass therethrough.

  In the discharge tube 1 described above, at both ends 11b and 11c of the tube main body 11, as shown in FIG. 1, an electric wire moving portion 7 for moving the electric wire 8 passed through the tube main body 11 is provided. The wire moving unit 7 includes a wire supply unit 71, a wire winding unit 72, a first roller unit 73 disposed on one end side 11 b of the tube body 11, and a first portion disposed on the other end 11 c side of the tube body 11. 2 roller portions 74.

  The electric wire supply unit 71 is arranged in the external space. The electric wire supply unit 71 includes a drum that is rotatably supported by winding the electric wire 8 before being irradiated with electrons. The wire winding unit 72 is disposed in the external space. The electric wire winding unit 72 includes a drum that is rotatably supported and winds the electric wire 8 that has been irradiated with electrons, and a drive unit that rotationally drives the drum.

  The first roller portion 73 is provided between the one end portion 11 b of the tube main body 11 and the wire supply portion 71 and the wire winding portion 72. The first roller portion 73 is attached to the tube main body 11 through a gauge port 73a and a differential exhaust device (not shown) is attached to the case 73b. And a plurality of rollers 73c.

  The second roller portion 74 is provided at the other end portion 11 c of the tube main body 11. The second roller portion 74 includes a case 74b attached to the pipe body 11 via a gauge port 74a, and a plurality of rollers 74c that are rotatably supported in the case 74b and over which the electric wire 8 is stretched. The rollers 73 c and 74 c are provided at positions where the spanned electric wire 8 can be positioned between the electron acceleration electrode 41 and the second mesh electrode 43.

  The electric wire 8 before being irradiated with electrons by the electric wire moving unit 7 is drawn from the electric wire supply unit 71 and then enters the tube main body 11 through the first roller unit 73 and the second roller unit 74. It passes through the inside of the pipe body 11 along the arrow A (FIG. 1) (path A). Thereafter, the electric wire 8 is folded back by the second roller portion 74 and passes through the pipe body 11 along the arrow B (FIG. 1) toward the first roller portion 73 (path B). Then, the electric wire 8 is folded back by the first roller portion 73 and is wound around the first roller portion 73 and the second roller portion 74 for a predetermined turn, and then drawn out to the external space through the first roller portion 73. The wire is wound around the wire winding portion 72 that is driven to rotate. In this way, the electric wire 8 reciprocates in the tube main body 11, and when moving along the path A, one outer surface in the radial direction of the covering portion is irradiated with electrons, and when moving along the path B, the other Electrons are irradiated on the outer surface, and electrons are irradiated on the entire outer surface of the covering portion.

  Hereinafter, the movement of electrons in the discharge tube 1 having the above-described configuration will be described. The inside of the pipe body 11 is depressurized by an exhaust device. For this reason, the plasma generated in the electron supply port 12 is drawn from the electron supply port 12 into the tube body 11 as a whole. The pressure of the argon plasma in the electron supply port 12 described above is about 2.7 to 6.7 Pa, and the pressure of the argon plasma in the tube body 11 is about 0.05 to 1.5 Pa.

  The argon ions in the plasma are attracted to the first mesh electrode 42 and captured on the outer surface of the first mesh electrode 42. Electrons in the plasma pass through the first mesh electrode 42 and are extracted from the plasma by the second mesh electrode 43 and accelerated along the arrow E by the electron acceleration electrode 41.

  Even if the electrons are accelerated in this way, the electrons cannot reach the electron acceleration electrode 41 when they collide with other particles or the like, so that argon gas, argon atoms and argon radicals present in a minute amount in the plasma are excluded. Further, the inside of the tube main body 11 and the inside of the electron supply port 12 are exhausted by an exhaust device to reduce the pressure.

  As described above, argon ions are eliminated by the first mesh electrode 42, and argon gas, argon atoms and argon radicals in the plasma are eliminated by the exhaust device, so that electrons do not collide with these particles. Is efficiently accelerated toward the electron accelerating electrode 41 and irradiated onto the electric wire 8. The first mesh electrode 42 not only prevents the argon ions from colliding with the electrons by eliminating the argon ions, but also the argon ions collide with the coating part of the electric wire 8 to thermally deform the coating part. It also prevents it.

  When irradiating the wire 8 with electrons using the electron beam irradiation apparatus 10 having the above-described configuration, first, microwaves are generated by the microwave generation unit 2, and the microwaves are transmitted to the surftron 31 via the slag tuner 22. The microwave is propagated to the electron supply port 12 of the discharge tube 1. Then, a microwave is applied to the argon gas supplied into the electron supply port 12, and the argon gas is ionized to generate plasma.

  This plasma is drawn into the tube body 11 by the exhaust device. Then, argon ions in the plasma are eliminated by the first mesh electrode 42, electrons in the plasma are extracted by the second mesh electrode 43, and directed toward the electron acceleration electrode 41 along the arrow E by the electron acceleration electrode 41. Accelerated. At this time, the electric wire moving portion 7 causes the electric wire 8 to reciprocate between the second mesh electrode 43 and the electron accelerating electrode 41 to irradiate the outer surface of the covering portion with electrons. In this way, the electric wire 8 is irradiated with electrons to promote the cross-linking reaction of the synthetic resin constituting the covering portion, and the heat resistance and mechanical properties of the covering portion are improved.

  According to this embodiment, since the inner surface 11a of the tube main body 11 is formed flat by a smooth surface, the argon gas stays in the vicinity of the electron acceleration electrode 41 when the inside of the tube main body 11 is exhausted. There is no. For this reason, when a high voltage is applied to the electron acceleration electrode 41, direct current discharge due to the retained argon gas is less likely to occur. The voltage, that is, energy applied to the electron acceleration electrode 41 is not easily consumed by the direct current discharge, and is consumed for accelerating the electrons. Therefore, energy loss can be reduced and electrons can be accelerated more efficiently.

  Moreover, since the surface of the support | pillar 41a of the electrode 41 for electron acceleration is covered with the coating layer 44, the DC discharge in the surface of an electrode support body can be prevented. For this reason, when a high voltage is applied to the electron acceleration electrode 41, direct current discharge is less likely to occur. The voltage, that is, energy applied to the electron acceleration electrode 41 is not easily consumed by the direct current discharge, and is consumed for accelerating the electrons. Therefore, energy loss can be reduced and electrons can be accelerated more efficiently.

  In the embodiment described above, the surface of the support column 41a of the electron acceleration electrode 41 is covered with the coating layer 44, but the coating layer 44 is not necessarily provided. Moreover, in embodiment mentioned above, although the electric wire 8 was demonstrated as an example to be irradiated, things other than the electric wire 8 may be used. In the above-described embodiment, the discharge tube 1 used in the electron beam irradiation apparatus 10 that accelerates electrons in plasma has been described. However, the discharge tube 1 accelerates electrons emitted from, for example, a filament. You may use for the electron beam irradiation apparatus 10 of a format, and you may use for the electron beam irradiation apparatus 10 of another type.

Example 1
The inventors operate the above-described electron beam irradiation apparatus 10 without passing the electric wire 8 and appropriately change the voltage (acceleration voltage) applied to the electron acceleration electrode 41 to change the electrons in the tube main body 11. Whether or not DC discharge occurs in the vicinity of the acceleration electrode 41 was visually confirmed, and the value of the current flowing through the electron acceleration electrode 41 at this time was measured. The gas serving as the plasma source is argon gas, the incident power from the microwave generator 2 is 60 W, the voltage applied to the first mesh electrode 42 is −100 V, and the pressure in the tube body 11 is 0.07 Pa. did. The acceleration voltage was changed to 10 kV, 20 kV, 30 kV, 40 kV, and 50 kV.

  As a comparative example, using an electron beam irradiation apparatus including the conventional discharge tube 101 shown in FIG. 5, it was confirmed whether or not a direct current discharge occurred in the discharge tube 101 under the same conditions as in Example 1. In the comparative example, the acceleration voltage was changed to 10 kV, 20 kV, and 30 kV. The results are shown in FIG.

  In FIG. 3, the range where the DC discharge occurs (discharge generation range) is indicated by dots. In the conventional discharge tube 101 (discharge tube I in FIG. 3), no DC discharge was observed when the acceleration voltage was 10 kV, and DC discharge was generated when the acceleration voltage was 20 kV or more. In the discharge tube 1 (discharge tube II in FIG. 3) of the present invention, no DC discharge was observed when the acceleration voltage was 10 kV to 30 kV, and DC discharge was generated when the acceleration voltage was 40 kV or more. Thus, in the discharge tube 1 of the present invention, it was confirmed that no DC discharge was generated even when an acceleration voltage higher than that of the conventional discharge tube 101 was applied.

(Example 2)
Next, the present inventors used the electron beam irradiation apparatus 10 described above to appropriately change the acceleration voltage and irradiate the electric wire 8 with electrons, and confirmed whether the electric wire 8 was undergoing a crosslinking reaction. The gas serving as the plasma source is argon gas, the incident power from the microwave generator 2 is 60 W, the voltage applied to the first mesh electrode 42 is −100 V, and the pressure in the tube body 11 is 0.07 Pa. did. The acceleration voltage was changed to 0 kV, 20 kV, 30 kV, and 40 kV. Further, the electric wire 8 was made of polyethylene resin as the covering portion, moved within the tube main body 11 at 5 m / min, and spanned 5 turns (5 reciprocations) between the first roller portion 73 and the second roller portion 74.

  For confirmation of the crosslinking reaction, the electron-irradiated (or unirradiated) electric wire 8 is cut to a predetermined length, and immersed in xylene at 120 ° C. for 24 hours to melt the uncrosslinked polyethylene resin (melting treatment) This was performed by measuring the weight of the coating part before and after the melting treatment. (Weight of coating part after melting treatment) / (weight of coating part before melting treatment) was defined as a gel fraction (%) (n = 4).

  Further, as a comparative example, using the electron beam irradiation apparatus provided with the conventional discharge tube 101 shown in FIG. 5, under the same conditions as in Example 2, the acceleration voltage is appropriately changed to irradiate the electric wire 8 with electrons. It was confirmed whether the cross-linking reaction was progressing with the electric wire 8. In the comparative example, the acceleration voltage was changed to 20 kV and 30 kV. The results are shown in FIG.

  As shown in FIG. 4, when the accelerating voltages are equal, the discharge tube 1 (discharge tube II) of the present invention has a higher gel fraction than the conventional discharge tube 101 (discharge tube I), and the crosslinking reaction proceeds more. It was confirmed that In the discharge tube 1 of the present invention, when the acceleration voltage was 40 kV, the crosslinking reaction did not proceed as compared with the case where the acceleration voltage was 30 kV. This is because when the accelerating voltage is 40 kV, a DC discharge occurs and a part of the voltage applied to the electron acceleration electrode 41, that is, a part of the energy is consumed by the DC discharge, and the electrons are sufficiently supplied despite the higher acceleration voltage. This is because the acceleration could not be achieved (as compared with the case where the acceleration voltage was 30 kV).

  The above-described embodiments are merely representative examples of the present invention, and the present invention is not limited to the above-described embodiments. That is, various modifications can be made without departing from the scope of the present invention.

1 Discharge tube 8 Electric wire (object to be irradiated)
11 Pipe body 11a Inner surface 12 Electron supply port 13 Equipment connection port (exhaust port)
41 Electron acceleration electrode
41a support (electrode support)
44 Coating layer

Claims (2)

A tube body that is formed in a cylindrical shape and passes an object to be irradiated with electrons inside,
An exhaust port for exhausting and depressurizing the inside of the tube body;
An electron supply port for supplying the electrons into the tube body;
An electrode arranged in the tube main body and accelerating the electrons supplied into the tube main body,
The discharge tube according to claim 1, wherein an inner surface of the tube body in the vicinity of the electrode is formed flat by a smooth surface.   The discharge tube according to claim 1, further comprising an insulating coating layer that is connected to the electrode and covers a surface of an electrode support that applies a voltage to the electrode.

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