TWI459434B - Electron gun filament and manufacturing method thereof - Google Patents

Description

Filament for electron gun and manufacturing method thereof

The present invention relates to an electron gun provided as a heating source in, for example, a melting furnace or a vapor deposition apparatus, a filament for an electron gun for heating a cathode electrode as an electron beam generating source, and a method of manufacturing the same.

An electron gun for emitting an electron beam is known, and a Pierce type gun (Pierce gun) described in Japanese Laid-Open Patent Publication No. Hei 7-201297. In general, a Pierce-type electron gun releases hot electrons from a filament that generates heat according to Joule heat of an alternating current, and the cathode electrode applies a positive voltage to the filament, which can be heated by hot electrons and heat radiation from the filament. Thereby, hot electrons can be released from the cathode electrode. Then, the hot electrons released from the cathode electrode can be focused by an electric field and released as an electron beam, which is based on a Wehnelt electrode having the same potential as the cathode electrode, and These cathode electrodes are formed by applying an anode electrode having a positive voltage to the Verneut electrode.

In the method of manufacturing the above-described filament constituting the electron gun, as shown in Fig. 1(a), a linear metal wire W composed of, for example, an alloy of tungsten or tungsten is used as a material. Then, by bending the center portion of the metal wire W in the longitudinal direction, the curved portion 100a for releasing the hot electrons can be formed into a concavo-convex shape (see FIG. 1(b)). Further, by bending the both sides of the clad bending portion 100a, the leg portion 100b fixed to the member for supporting the filament 100 can be formed.

Here, when such a filament 100 is used as the heating source of the above-described cathode electrode, an alternating current is constantly supplied to the bent portion 100a during the release of the electron beam to sufficiently discharge the cathode electrode to the degree of thermal electrons. The heat is supplied to the cathode electrode by the bent portion 100a. Therefore, the curved portion 100a is continuously maintained at a high temperature of approximately 2000K to 3000K. As described above, when the curved portion 100a subjected to the bending process is continuously heated, the retracting force is generated during the processing distortion remaining in the curved portion 100a by heating, so that the filament 100 is easily deformed. Not only that, the filament 100 is brought into contact with the cathode electrode with such deformation, or the center of the filament 100 is offset from the center of the cathode electrode, so that the output of the electron beam released from the electron gun becomes unstable.

Therefore, in order to solve various problems caused by the above thermal deformation, the following countermeasures are considered: (a) the filament is spaced apart from the cathode electrode in advance so that the filament does not come into contact with the cathode electrode even if the filament is deformed; and (b) In order to suppress the deformation caused by the above heating, after the wire W is bent to form a filament having the shape shown in the first FIG. 1(b), the annealing treatment is further performed.

However, although the method of the above (a) can avoid contact between the filament and the cathode electrode, if the distance between these becomes large, the hot electrons from the filament naturally hardly reach the cathode electrode. Under such circumstances, when the cathode voltage for introducing hot electrons into the cathode electrode is increased in order to secure a quantitative beam output, the control of the electron beam is unstable, and a new problem that abnormal discharge is likely to occur is induced. Further, when the temperature of the filament is further increased in order to ensure a quantitative beam output, the remaining thermal energy that is not applied to the heating of the cathode electrode is released to an electron gun including a filament, a cathode electrode, a Vernet electrode, and an anode electrode. In the electron beam generating portion including the constituent members, the amount of gas released from the constituent members of the electron gun is increased, and a new problem of abnormal discharge is also induced.

Further, the method of the above (b) can reduce the distortion of the filament and suppress the bending and folding by the annealing treatment, but on the other hand, since the filaments constituting the filament are coarsened and the filament is embrittled, the filament is installed. When the support member for supporting the filament is broken, the filament is broken. Further, as means for suppressing breakage of the embrittled filament, it is also conceivable that the filament subjected to the annealing treatment as described above is previously attached to the insulator capable of maintaining the filament shape, and the filament is together with the insulator. It is attached to the above-mentioned support member as a filament unit. However, since this method requires additional insulation, it will result in an increase in the cost of maintaining the filament. Therefore, there is still room for improvement in the countermeasures for solving the deformation itself caused by the heating of the filament or the various problems caused by the deformation.

Accordingly, the present invention provides a filament for an electron gun and a method of manufacturing the same to effectively solve the above-mentioned problems encountered in the prior art.

An object of the present invention is to provide a filament for an electron gun which can suppress deformation of a filament mounted on an electron gun by heating when an electron gun is used, and a method of manufacturing the same.

A first embodiment according to the present invention is a method of manufacturing a filament for an electron gun. The method comprises the steps of: preparing a sheet of metal material; and cutting from the sheet a wire having at least one curved filament.

According to this method, a wire having at least one curved filament can be cut out from a plate composed of a metal material. Therefore, the processing distortion remaining in the curved portion of the filament can be suppressed as compared with the conventional filament formed by bending the wire for bending. Therefore, it is possible to suppress the occurrence of folding back at the bent portion of the bend even when the filament is sometimes heated when the electron gun is used. That is, the shape of the bend changes due to heating, whereby the deformation of the filament can be suppressed.

In the above method, the step of preparing the sheet material may further comprise the step of preparing a metal laminate sheet composed of a plurality of metal sheets which have been laminated in the thickness direction of the sheet material.

The metal material used for the sheet of the filament is a collection of crystal grains, and each crystal grain grows by heating. When the heating conditions are increased in temperature or long-term, the crystal grains are coarsened, and the sheet is brittle. As a method of suppressing the embrittlement, it is conceivable to use a laminate of a plurality of metal sheets as a sheet of a filament as described above. This method can reduce the thickness of each metal plate compared to the case of using a single metal plate. Thereby, it is possible to naturally suppress the coarsening of crystal grains in the thickness direction of the metal plate, and it is possible to improve the strength and life of the filament for the electron gun.

In the above method, the plurality of metal plates may be separately rolled, and the plurality of metal plates are laminated such that the rolling directions of the respective metal plates cross each other.

In the thin metal sheet formed by rolling, generally, the higher the rolling rate, the more the mechanical strength of the rolling direction and the other directions are different. For example, the properties such as the modulus of elasticity, the strength of the fall, and the tensile strength tend to be the largest in the direction perpendicular to the rolling direction and the smallest in the direction parallel to the rolling direction. On the other hand, the elongation characteristics have the smallest tendency in the direction perpendicular to the rolling direction and the largest in the direction parallel to the rolling direction. In consideration of this, in the case of using a plurality of metal plates formed by rolling, a plurality of metal plates may be laminated so that the rolling directions of the respective metal plates cross each other. In this method, the mechanical properties of the metal sheets are complementary and the mechanical strength of the laminate is increased. Further, the mechanical strength of the filament constituted by the wire cut out from the laminated board can be improved.

In the above method, the plurality of metal plates may also be formed by different metal materials.

In this method, compared with the case where a plurality of metal plates are formed of the same metal material, it is possible to suppress the coarsening of the crystal grains of the respective metal plates beyond the interface between the metal plates. In other words, it is possible to suppress the coarsening of the crystal grains of the respective metal sheets beyond the thickness of the respective metal sheets. As a result, the coarsening of the crystal grains in the thickness direction of the laminated plate can be limited to the thickness of the metal plate to which the crystal grains belong.

In the above method, the filament can be manufactured under the following premise: when the filament is mounted on the electron gun, the curvature of the filament is opposite to the cathode electrode disposed on the electron gun, and is heated by the current supplied from the power source to be released. A hot electron used to heat the cathode electrode. In this case, the step of preparing the metal laminated plate may further include the step of forming a metal plate opposed to the cathode electrode by a metal plate having a minimum work function among the plurality of metal plates.

The so-called work function refers to the minimum energy required to take an electron from the surface of a substance. In other words, when a hot electron is to be released from the surface of a substance, it is necessary to heat the substance and supply the energy above the work function to the electrons in the substance. Therefore, the material with a large work function needs to be heated to a higher temperature in order to release the hot electrons, in other words, a larger current needs to flow. In consideration of this, when a metal laminated plate is used for the sheet of the filament, among the plurality of metal plates, the work function of the metal plate opposed to the cathode electrode of the electron gun may be smaller than that of the other metal plates. Thereby, in the metal plate close to the cathode electrode, the release of the hot electrons occurs at a temperature lower than that of the other metal plates. Therefore, the filament formed by bending a wire composed of a single material as compared with the conventional method can lower the temperature of the metal plate opposed to the cathode electrode, and can even lower the temperature of other metal plates. It is possible to suppress deformation of the filament toward the cathode electrode side.

In the above method, the step of preparing the plate material may further include the step of preparing a plate material formed of a metal plate of at least one of tungsten and an alloy containing tungsten.

Since tungsten is the metal material having the highest melting point, it is easy to maintain stability even when its shape is used at a high temperature. Further, since tungsten has a large electric resistance, the amount of heat generated when current flows to tungsten also increases. That is to say, tungsten is suitable as a material for forming a member which is required to have heat stability and a large amount of heat generation. When considering this point, the filament sheet is preferably formed of at least one of tungsten and a tungsten-containing alloy.

In the above method, the step of preparing the plate may further include the step of preparing a metal laminated plate composed of a base metal plate and a tungsten metal plate.

The lanthanide releases hot electrons at a lower temperature than tungsten. Therefore, the temperature rise of the filament itself can be suppressed as compared with a conventional filament formed by bending a wire of a single material or a filament formed by cutting a wire from a single tungsten plate. Therefore, deformation of the filament due to heating can be suppressed, and the average life of the filament can be extended.

In the above method, the step of cutting the wire of the filament for the electron gun from the plate comprises the step of cutting the wire from the plate by wire electrical discharge machining.

The wire electric discharge machining generally refers to a method of processing a workpiece into a desired shape by using a discharge between a metal wire as a tool electrode and a workpiece to remove a part of the workpiece. Therefore, if the object to be processed is a conductor, it can be processed without being affected by the hardness. Further, the workpiece can be processed into a desired shape by position control of the metal wire. Therefore, if wire discharge machining is used for the cutting operation of the wire material from the sheet material, the selected width of the filament forming material can be enlarged, and the precision of the filament shape can be improved.

According to a second embodiment of the present invention, a filament for an electron gun is used. The filament is formed of a metal material and has a wire having at least one bend, and the wire has a rectangular cross section.

According to this configuration, it is possible to suppress the processing distortion remaining in the curved portion of the filament, compared with the conventional filament formed by bending the metal wire and the conventional filament having a circular cross section. Therefore, even when the filament is heated when the electron gun is used, it is possible to suppress the occurrence of folding back in the curved portion of the bend. That is, the shape of the bend changes due to heating, whereby the deformation of the filament can be suppressed.

In the above filament, the wire may be formed using a metal laminated plate including a plurality of metal plates. This configuration can reduce the thickness of each metal plate as compared with the case of using a single metal plate. Thereby, the coarsening of the crystal grains in the thickness direction of the metal plate can be naturally suppressed, and the strength and life of the filament for the electron gun can be improved.

In the above filament, the plurality of metal plates may also be formed by different metal materials. In this configuration, crystal grains of the respective metal sheets can be suppressed from being coarsened beyond the thickness of each of the metal sheets. As a result, the crystal grains in the thickness direction of the laminated plate can be coarsened and limited to the thickness of the metal plate to which the crystal grains belong.

In the above filament, the metal laminated plate may also be a laminated plate of a base metal plate and a tungsten metal plate. In this configuration, the temperature of the filament itself can be suppressed from being lowered by a filament formed by bending a wire of a single material or by a filament formed by cutting a wire from a single tungsten plate. Therefore, deformation of the filament due to heating can be suppressed, and the average life of the filament can also be extended.

In the above filament, the filament may be formed such that a metal plate having a minimum work function among a plurality of metal plates is disposed to face the cathode electrode of the electron gun. In this configuration, among the metal plates close to the cathode electrode among the plurality of metal plates, the release of the hot electrons is performed at a temperature lower than that of the other metal plates. Therefore, the temperature of the metal plate opposed to the cathode electrode can be lowered as compared with the conventional filament formed by bending a wire composed of a single material. Further, since the temperature of the other metal plates can be lowered, the deformation of the filament toward the cathode electrode side can be suppressed.

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

Hereinafter, an embodiment in which the manufacturing method of the filament 1 for an electron gun according to the present invention is embodied will be described with reference to FIGS. 2 and 3.

Fig. 2 is a view showing the three-dimensional structure of the filament 1 for an electron gun manufactured by the manufacturing method of the present embodiment. As shown in FIG. 2, the filament 1 for an electron gun is a linear member having a rectangular cross section formed of a high melting point metal such as tungsten which is formed by four surfaces on its outer peripheral surface. The filament 1 for an electron gun has a concave-convex curved portion 1a composed of a curved portion 1c obtained by three consecutive portions on a virtual plane Pi, and the virtual plane Pi includes one surface (cathode) constituting the outer peripheral surface. Opposite face 1s). Both end portions of the curved portion 1a in the direction of the curved portion 1c of the three portions are bent and formed with a pair of linear leg portions 1b extending in the normal direction of the cathode opposing surface 1s. In other words, the filament 1 for an electron gun as a wire having a rectangular cross section is curved so as to be along any one of the four faces constituting the outer peripheral surface, thereby constituting the circumferential direction of the filament 1 without distortion.

Fig. 3 shows the manufacturing steps of the filament 1 for the electron gun. As shown in Fig. 3(a), when the filament 1 for an electron gun is manufactured, first, a metal plate P made of, for example, tungsten is used as a constituent material of the wire. Further, in the metal plate P of the present embodiment, a tungsten plate having the above-described cathode opposing surface 1s (virtual plane Pi) as the processed surface Ps and having a thickness of, for example, 0.5 mm is used.

Next, as shown in Fig. 3(b), the processing of the metal plate P can be performed by a well-known wire electrical discharge machining device WE. More specifically, the tool wire electrode WE1 made of tungsten or the like and the metal plate P as the workpiece to be disposed orthogonally to the processed surface Ps of the metal plate P are applied with, for example, 60 V from the machining power source WE2. A voltage of up to about 300V. Then, the position of the metal plate P is controlled by the well-known NC (Numerical Control) device WE3, and the shape of the curved portion 1c of the three opposing portions on the cathode opposing surface 1s, that is, the filament for the electron gun is used. The shape of the concavity and convexity of the second element of the curved portion 1a in 1 causes the metal plate P to move up and down or left and right. Incidentally, the moving speed of the metal sheet P at this time (that is, the so-called processing feed speed) is generally about 5 mm per minute. Thereby, when the distance between the tool wire electrode WE1 and the metal plate P becomes about several tens of μm, spark discharge occurs during these periods. At this time, the temperature of the tool wire electrode WE1 and the metal plate P is heated to several thousand degrees, and one part of the metal plate P is melted, and the molten metal is cooled by the metal plate P and the processed powder is removed. The volume of the machining fluid supplied for the purpose is expanded to scatter from the metal plate P. Further, as the working fluid, an insulating liquid such as water or kerosine can be used. Further, the tool wire electrode WE1 is supplied and wound by a wire supply mechanism and a wire winding mechanism (not shown) in order to avoid melting or breaking due to heating. Thus, by melting the metal, a processing groove can be formed in the metal plate P. Further, while the position control of the metal plate P is performed by the NC device WE3, the step of forming the processing groove is repeated, whereby the wire P1 for forming the filament 1 for the electron gun can be cut out including the curved portion 1a. .

When the wire electric discharge machining is performed by the above-described wire electrical discharge machining apparatus WE, the conductor can be processed as the electron gun filament 1 without being limited to its hardness, so that it can be enlarged. The selected width of the material forming the filament 1 for the electron gun. Further, since the NC device WE3 included in the wire electric discharge machining device WE can precisely control the position of the metal plate P in accordance with the shape of the secondary element of the filament 1 for the electron gun, the shape of the filament 1 for the electron gun can be improved. Precision.

The wire P1 obtained by the wire electric discharge machining apparatus WE is cut as shown in Fig. 3(c), and has a curved portion 1a at the center portion in the longitudinal direction and is formed perpendicular to the processing surface Ps (cathode opposite surface 1s). The section of the curve becomes a rectangular form. Then, as shown in Fig. 3(d), both ends of the wire P1 in the longitudinal direction can be bent by the normal direction of the processed surface Ps (the cathode opposing surface 1s), whereby the filament for the electron gun can be manufactured. .

The manufacturing method of the filament 1 for an electron gun is not a method of manufacturing the conventional filament 100 as shown in the first drawing of the prior art, and bending is performed by applying an external force to the wire W as a wire to form the bent portion 100a. Instead of the wire electric discharge machining device WE, the wire P1 is cut out from the metal plate P in a form including the curved portion 1a. Therefore, the method for manufacturing the filament 1 for an electron gun can suppress the distortion caused by the processing of the curved portion 1a of the filament 1 for the electron gun manufactured, and can suppress the heating caused by the filament 1 of the electron gun being mounted on the electron gun. The electron gun is deformed by the filament 1 (especially its curved portion 1a).

Further, in the filament 1 thus obtained by the wire electric discharge machining, as described above, the shape of the cross section perpendicular to the cathode opposing surface 1s including the curved portion 1a is a rectangle. Further, a pair of opposing faces constituting the outer peripheral surface of the filament 1 for the electron gun, specifically, a pair of faces perpendicular to the cathode opposing surface 1s including the curved portion 1a are formed by wire electric discharge machining. Processing marks. The processing marks are formed with strip-like marks (so-called streaks) perpendicular to the traveling direction of the tool wire electrode WE1 at the time of wire electrical discharge machining, that is, the longitudinal direction of the wire P1 of the filament 1 of the electron gun, at predetermined intervals. . Therefore, the filament 1 for an electron gun can recognize the filament 100 formed by bending a metal wire W (Fig. 1) by a conventional matter, that is, the cross-sectional shape of the filament 1 is rectangular; and A streak is formed at a predetermined interval.

Next, an electron gun in which the filament 1 for an electron gun is mounted, and a so-called Pierce-type electron gun 10 will be described with reference to Fig. 4 . Fig. 4 shows a schematic configuration of a Pierce-type electron gun 10 which is applied to, for example, a vapor deposition device. As shown in Fig. 4, the Pierce-type electron gun 10 is provided with a filament 1 for an electron gun that generates heat by exchanging Joule heat of an alternating current to release hot electrons. In the normal direction (irradiation direction D) of the filament 1 of the electron gun with respect to the cathode opposing surface 1s, the cathode electrode 2, the Vernett electrode 3, the anode electrode 4, and the flow register are sequentially disposed. 5. Further, an ion collector 8 is disposed adjacent to the filament 1 of the electron gun in the opposite direction to the irradiation direction D.

The curved portion 1a of the filament 1 for the electron gun and the cathode electrode 2 are arranged to face each other in the irradiation direction D. As shown by a dot chain line in Fig. 4, the center of each of the filament 1 and the cathode electrode 2 of the electron gun is disposed on the optical axis A extending in the irradiation direction D. The Vernet electrode 3 surrounds the periphery of the cathode electrode 2 around the optical axis A. In the irradiation direction D, the anode electrode 4 of the dome-shaped electrode is disposed in the vicinity of the Venetate electrode 3, and the anode electrode 4 has a surface opposite to the surface of the cathode electrode 2 (the surface perpendicular to the irradiation direction D). Through hole. The anode electrode 4 is connected to the flow rate adjuster 5, and the flow rate adjuster 5 has a through hole continuous with the through hole of the anode electrode 4 in the irradiation direction D. On the outer circumference of the flow regulator 5, a focus coil 6 and a swing coil 7 are sequentially disposed from a position close to the anode electrode 4. Each of the focus coil 6 and the swing coil 7 has a function of generating a magnetic field so that the electron beam EB passing through the anode electrode 4 is focused on the object to be irradiated (in this example, the vapor deposition material 31) or is subjected to evaporation. The material 31 swings.

Further, the electron gun filament 1, the various electrodes 2 to 4, the various coils 6, 7 and the ion collector 8 are mounted in a casing 9 having an opening. The opening of the casing 9 is provided as an irradiation port of the electron beam EB, and is connected to each of the through holes of the anode electrode 4 and the flow rate regulator 5. Further, a flange 9a is provided around the opening of the casing 9, and the flange 9a is fixed to the vapor deposition chamber 30 in which the vapor deposition material 31 as the irradiation target of the electron beam EB is disposed. The vapor deposition chamber 30 communicates with the opening of the casing 9 constituting the electron gun 10 through the flange 9a.

The filament 1 for an electron gun is connected to a filament power supply 21 for supplying an alternating current to the filament 1 of the electron gun, and the cathode electrode 2 and the Venetate electrode 3 are connected to a cathode power supply 22 to which a DC voltage is applied. The anode electrode 4 is connected to an acceleration power source 23 to which a DC voltage is applied. The cathode electrode 2, the Verneite electrode 3, and the anode electrode 4 are applied with an input voltage from the cathode power source 22 and the acceleration power source 23 such that the potential of the filament 1 for the electron gun is the lowest and the potential of the anode electrode 4 is the highest.

In this Pierce type electron gun 10, the alternating current from the filament 21 is first supplied to the filament 1 for the electron gun, and the filament 1 of the electron gun is heated to 2000 K to 3000 K to release hot electrons. Then, the cathode electrode 2 having a positive potential applied to the filament 1 for the electron gun by the cathode power source 22 can be heated by the hot electrons and the heat radiation from the filament 1 of the electron gun, whereby the hot electrons are also released. The hot electrons released by the cathode electrode 2 are the Vernett electrode 3 having the same potential as the cathode electrode 2, and the anode having a positive potential applied to the cathode electrode 2 and the Vernett electrode 3 The potential difference between the electrodes 4 is accelerated to fly along the optical axis A. Then, the through-holes of the anode electrode 4 and the thermoelectrons of the flow rate adjuster 5 connected to the through-holes are emitted as electron beams EB from the opening of the casing 9 toward the vapor deposition chamber 30.

At this time, when a part of the hot electrons released from the cathode electrode 2 collides with the residual gas in the casing 9 and the vapor deposition chamber 30, the residual gas is cationized. This cation is accelerated by the voltage between the cathode electrode 2 and the anode electrode 4. When the accelerated cation hits the cathode electrode 2, a hole is formed in the cathode electrode 2 due to this. Therefore, if such a cation is released for a long period of time, the pores become large and a through hole may be formed in the cathode electrode 2. In consideration of such a situation, the cathode electrode 2 is adjacent to the cathode electrode 2 and disposed in the opposite direction to the irradiation direction D. Even when the through hole is formed in the cathode electrode 2, the constituting the through hole of the cathode electrode 2 releases the cation to the filament 1 of the electron gun, that is, the ion beam can be absorbed by the ion collector 8. Therefore, damage to the electron gun 10 due to the ion beam can be suppressed.

Here, the filament 1 for an electron gun according to the present embodiment is also capable of suppressing thermal deformation of the conventional filament 100 as compared with the conventional filament 100 (see Fig. 1) because the processing distortion is small. In other words, when the alternating current is supplied to the filament 1 for the electron gun, the filament 1 for the electron gun is displaced toward the cathode electrode 2 side and can be suppressed more than the conventional filament 100. Therefore, the distance between the filament 1 for the electron gun and the cathode electrode 2 (hereinafter referred to as F-C distance) can be shortened. Therefore, in terms of obtaining the output of the electron beam EB similar to the conventional one, the heating condition of the filament 1 for the electron gun can be made slower as long as the F-C distance is shortened. Therefore, not only the processing distortion is small, but also the temperature can be slowly heated, so that the thermal deformation of the filament 1 for the electron gun can be more reliably suppressed. Further, the F-C distance between the filament 1 and the cathode electrode 2 of the electron gun can be maintained at a constant value, and the center of the filament 1 for the electron gun and the center of the cathode electrode 2 can be appropriately maintained at the initial position. As a result, the stability of the output of the electron beam EB released from the electron gun 10 can be improved.

Hereinafter, the first embodiment and the production example of the filament 1 for an electron gun according to the present invention will be described.

A tungsten plate having a thickness of 0.5 mm is prepared as the metal plate P, and wire cutting processing using the wire electric discharge machining apparatus WE is performed, whereby the wire P1 including the curved portion 1a is cut out from the tungsten plate. Then, both ends in the longitudinal direction of the wire P1 cut out from the tungsten plate were subjected to bending processing to form the leg portion 1b, whereby the filament 1 for an electron gun of Example 1 was obtained. Further, a tungsten wire having a diameter of 0.5 mm, that is, a metal wire having a circular cross section is subjected to bending processing, thereby obtaining a comparison of the curved portion 100a corresponding to the curved portion 1a and the leg portion 100b corresponding to the above-mentioned leg portion 1b. For example, the filament 100.

Then, the electron gun 10 on which the filament 1 for the electron gun of the first embodiment is mounted and the electron gun 10 on which the filament 100 of the comparative example is mounted are driven by the following irradiation conditions, and the amount of deformation of the filament 1 of the electron gun of the first embodiment toward the cathode electrode 2 is measured. And the amount of deformation of the filament 100 of the comparative example toward the cathode electrode 2 side. Further, the electron gun 10 used for measurement has the same configuration except that the filament is different.

‧Electronic beam output: 17kW

‧ Accelerating voltage: 20kV

‧Cathode voltage: 1.2kV

‧F-C distance: 4.2mm

Further, as a method of controlling the output of the electron beam EB from the electron gun 10, it is known as filament control and cathode control. In the above control methods, the term "filament control" means that the voltage applied between the filament 1 and the cathode electrode 2, that is, the cathode voltage, is constant, and the output of the electron beam EB is controlled by adjusting the power input to the filament 1. method. On the other hand, the cathode control refers to a method of adjusting the cathode voltage by setting the power input to the filament 1 constant. Hereinafter, the results obtained by driving the respective electron guns 10 mainly by filament control among the two control methods are shown.

As a result of measuring the amount of deformation described above, it was confirmed that the amount of deformation of the filament 1 for the electron gun of Example 1 toward the cathode electrode 2 side was smaller than the amount of deformation of the filament 100 of the comparative example toward the cathode electrode 2 by 1.6 mm. In other words, it can be confirmed that when the filament 100 of the comparative example is used, the minimum value of the FC distance needs to be 4.2 mm. In contrast, by using the filament 1 for the electron gun of the first embodiment, the minimum value of the FC distance can be shortened to 2.6mm.

Next, the irradiation condition dependency of the electron beam output from the electron gun 10 on which the filament 1 for the electron gun of Example 1 is mounted is measured. Fig. 5 is a view showing the relationship between the electron beam output irradiated under the following irradiation conditions and the input power to the filament 1 for the electron gun for the two types of F-C distances. Further, Fig. 6 is a view showing the relationship between the electron beam output irradiated under the following irradiation conditions and the input power to the cathode electrode 2 in the same manner for the F-C distances of the two types. Next, Fig. 7 is a view showing the relationship between the electron beam output and the input power to the filament 1 for the electron gun when the F-C distance is 2.6 mm for three types of cathode voltages. Further, the input power to the cathode electrode 2 means the product of the cathode voltage and the current flowing between the filament 1 and the cathode electrode 2.

Here, in the fifth and sixth figures, the results obtained by setting the F-C distance to 2.6 mm are shown by black circles, and the results obtained by setting the F-C distance to 4.2 mm are shown by the black squares. Further, Fig. 7 shows the result of setting the cathode voltage to 1.0 kV in a black diamond shape, and then displaying the cathode voltage as 1.2 kV in a black circle, and further setting the cathode voltage to 1.4 in a black triangle. The result of kV.

‧Maximum output of electron beam: 30kW

‧ Accelerating voltage: 20kV

‧Cathode voltage: 1.2kV

‧F-C distance: 2.6mm, 4.2mm

By the way, it is set to be 4.2 mm out of 2.6 mm and 4.2 mm which are FC distances, and it is settable when the filament 100 of the comparative example manufactured by the conventional manufacturing method shown by the above-mentioned 1st figure is used. As the minimum value of the FC distance. On the other hand, in the case of using the filament 1 for an electron gun of the embodiment manufactured by the manufacturing method of the present embodiment shown in the third embodiment shown above, 2.6 mm is set as the minimum value of the F-C distance. Here, the reason why the distance between the filament 1 manufactured by the manufacturing method of the present embodiment and the cathode electrode 2 can be set shorter is as described above.

As shown in Fig. 5, if the output of the electron beam EB is 17 kV, when the FC distance is 2.6 mm, the input power to the filament 1 is about 83.6 W. In contrast, when the FC distance is 4.2 mm, The input power of the filament 1 is approximately 93.1W. Therefore, it can be seen that the input power to the filament 1 can be reduced by about 10% by shortening the above F-C distance. Moreover, the case where the output of the electron beam EB is not limited to 17 kV is not limited, and as shown in Fig. 5, substantially the same tendency can be obtained even when it is set to 0.84 kW, 2.8 kW, 5.6 kW, or 11.2 kW. This can be seen as long as the FC distance is shortened, which is caused by the fact that the hot electrons released from the filament 1 are easily pulled into the cathode electrode 2; and the form factor of the heat radiation, that is, the heat radiated from the filament 1 The proportion of the cathode electrode 2 becomes large.

As shown in Fig. 6, the input power to the cathode electrode 2 when the output of the electron beam EB is 17 kV is 932.4 W when the FC distance is 4.2 mm, whereas the FC distance is set. When it is 2.6mm, it is 560W. Therefore, it can be seen that the input power to the cathode electrode 2 can be reduced by about 40% by shortening the above F-C distance. Further, as shown in Fig. 6, even if the output of the electron beam EB is set to any of 0.84 kW, 2.8 kW, 5.6 kW, and 11.2 kW, the cathode electrode 2 can be reduced even if it is not set to the above-described 17 kW. input power. As described above, it can be considered that as long as the FC distance is shortened, it is generated by the fact that the hot electrons released from the filament 1 of the electron gun are easily pulled into the cathode electrode; and the form factor of the heat radiation, that is, from The proportion of heat radiated from the filament 1 reaching the cathode electrode 2 becomes large. Moreover, since the amount of space charge is limited, the larger the F-C distance is, the higher the cathode voltage is required, which can be regarded as one of the reasons why a large cathode electrode input power is required.

As can be understood from the results of the fifth and sixth figures, by shortening the FC distance, the desired electron beam EB can be obtained while reducing the input power to the filament 1 of the electron gun or the input power to the cathode electrode 2. The output.

As shown in Fig. 7, even if the output of the electron beam EB is set to any of 0.84 kW, 2.8 kW, 5.6 kW, 11.2 kW, and 17 kW, the higher the cathode voltage, the smaller the input power to the filament 1 is. . This can be considered because the hot electrons released from the filament 1 are easily pulled into the cathode electrode 2 as long as the cathode voltage is high. However, the controllability of the output of the electron beam EB is also understood from the inclination of the respective graphs shown in Fig. 7, and the lower the cathode voltage, the higher the cathode voltage. The reason is that the lower the cathode voltage is, the more the input power to the filament 1 is increased by a predetermined value, or the degree of change in the output of the electron beam EB is reduced. Therefore, the precision of the output control of the electron beam EB can be improved.

As is clear from the results of Fig. 7, when the electron gun 10 is driven by the above-described filament control, the precision of the output control of the electron beam EB can be improved by setting the cathode voltage to a lower value, but in order to obtain the desired The output of the electron beam EB has a need to increase the input power to the filament 1 of the electron gun. As described above, in the case of the filament 1 for an electron gun of the first embodiment, in order to shorten the F-C distance, the input power to the filament 1 for the electron gun can be reduced in order to obtain the desired output of the electron beam EB. Therefore, it is also possible to offset the increase in the input power to the filament of the electron gun required for improving the precision of the output control of the electron beam EB by reducing the portion obtained by shortening the F-C distance. In other words, in the case of the filament 1 for the electron gun in which the processing distortion in the curved portion 1a is suppressed, the precision of the output control of the electron beam EB can be improved without increasing the input power to the filament for the electron gun.

Then, the duration performance of the beam current when the electron gun 10 in which the filament 1 for the electron gun of the first embodiment is mounted and the electron gun 10 in which the filament 100 of the comparative example is mounted is driven under the following irradiation conditions is measured. Further, the electron gun 10 used for measurement has the same configuration except that the filament is different. Fig. 8(a) shows the degree of fluctuation of the beam current of the filament 1 for the electron gun of the first embodiment, and Fig. 8(b) shows the degree of fluctuation of the beam current of the filament 100 for the electron gun of the comparative example. In Figs. 8(a) and 8(b), the maximum value of the beam current per hour is indicated by the solid line Lmax, and the minimum value is indicated by the solid line Lmin, and each line is indicated by a broken line Lav. The average of the beam currents for 1 hour, and the bar graph shows the difference between these maximum and minimum values as the amplitude of the beam current per hour.

‧Electronic beam output: 17kW

‧ Accelerating voltage: 20kV

‧beam current: 850mA

‧ Cathode voltage: 1.2 kV (Example 1), 1.4 kV (Comparative Example)

‧F-C distance: 2.6 mm (Example 1), 4.2 mm (Comparative example)

‧ Irradiation time: 90 hours

In the first embodiment shown in Fig. 8(a), since the F-C distance can be set to 2.6 mm as described above, 1.2 kV can be set as the cathode voltage satisfying the above irradiation conditions. Under such irradiation conditions, when the value of the beam current is measured in about 90 hours, the difference between the average value and the maximum value of the beam current per hour is at most 5 mA, and the difference between the average value and the minimum value is the smallest. It is 3mA. On the other hand, in the comparative example shown in FIG. 8(b), since the distance between the filament and the cathode electrode was set to 4.6 mm, 1.4 kV was set as the cathode voltage satisfying the above irradiation conditions. Under such irradiation conditions, when the value of the beam current is measured in about 90 hours, the difference between the average value and the maximum value of the beam current per hour is at most 10 mA, and the difference between the average value and the minimum value is the smallest. It is 4mA.

As described above, the fluctuation range when the filament 1 for an electron gun of the first embodiment is used can be reduced to 1/1.75 as compared with the fluctuation range when the filament 100 of the comparative example is used. Compared with the filament 100 of the comparative example, the reason why the fluctuation range is reduced in the filament 1 for the electron gun of the first embodiment is that the thermal deformation due to heating can be suppressed, so that the variation of the FC distance caused by the energization can be reduced and The FC distance can be shortened, and as a result, it can be considered that the output controllability of the electron beam EB can be improved by setting the cathode voltage to be low.

Next, the electron gun 10 on which the filament 1 for the electron gun of the first embodiment is mounted and the electron gun 10 on which the filament 100 of the comparative example is mounted are driven to be driven under the same irradiation conditions as in the above-described eighth drawings (a) and (b). As the filament life of durable time. In addition, the term "duty time" as used herein refers to the time until the filament is disconnected after the filament is energized. Further, the durability time of each of the 25 individual filaments 1 of the electron gun of Example 1 and the filament 100 of the comparative example was measured.

As shown in Fig. 9, the average durability time of the filament 100 of the comparative example was 371 hours, whereas the average durability time of the filament 1 for an electron gun of Example 1 was 700 hours. In other words, it can be understood that the average durability time of the filament 1 for an electron gun of Embodiment 1 is 1.9 times the average durability time of the filament 100 of the comparative example. In the filament 1 for an electron gun of the first embodiment, the deformation due to heating can be suppressed, so that mechanical deterioration in the filament 1 for the electron gun can be suppressed, and since the FC distance can be shortened, The input power to the filament 1 of the electron gun can be reduced. That is, it can be considered that the cause is that the temperature of the filament 1 for the electron gun can be lowered. Further, in the filament 100 of the comparative example, the difference between the longest durability time and the shortest durability time is about 300 hours. In contrast, in the filament 1 for the electron gun of the first embodiment, the longest durability time and the shortest durability time are obtained. Since the difference is about 200 hours, it is understood that the variation in the durability time between the individual filaments of the electron gun can be suppressed.

As described above, according to the method of manufacturing the filament 1 for an electron gun of the present embodiment, the effects listed below can be obtained.

(1) The wire P1 constituting the curved portion 1a formed in the filament 1 for an electron gun can be cut out from the metal plate P. Thereby, the filament 1 for the electron gun can suppress the processing distortion remaining inside the curved portion 1a as compared with the conventional filament 100 having the curved portion 100a formed by bending the wire of the metal wire W, for example. . As a result, when the electron gun 10 is used, even if the filament 1 for the electron gun is heated, the processing distortion remaining inside the curved portion 1a is extremely small, so that the folding of the curved portion 1a can be suppressed from occurring. Therefore, it is possible to suppress a change in the shape of the curved portion 1a, that is, the filament 1 is deformed by heating.

(2) Since the thermal deformation of the filament 1 for the electron gun can be suppressed, the distance (F-C distance) between the filament 1 of the electron gun and the cathode electrode 2 can be shortened. As a result, the desired output of the electron beam EB can be obtained while reducing the input power to the electron gun 10, for example, the input power to the filament 1 or the input power to the cathode electrode 2.

(3) Since the thermal deformation of the electron gun 1 can be suppressed, the fluctuation of the F-C distance due to energization can be reduced, and the F-C distance can be shortened. As a result, the cathode voltage can be set low to improve the output controllability of the electron beam EB. By increasing the output controllability, the output fluctuation range of the electron beam EB when using the filament 1 for the electron gun of the present embodiment can be reduced to 1 as compared with the fluctuation range of the output of the electron beam EB when the conventional filament 100 is used. /1.75.

(4) Since the thermal deformation of the filament 1 for the electron gun can be suppressed, the mechanical deterioration in the filament 1 for the electron gun can be suppressed, and the F-C distance can be shortened. As a result, the power input to the filament 1 for the electron gun can be reduced, and the temperature rise of the filament 1 for the electron gun can be suppressed. Thereby, the average durability time of the filament 1 for the electron gun can be extended by about 1.9 times as compared with the conventional filament 100.

(5) In the conventional filament 100, the difference between the longest durability time and the shortest durability time is about 300 hours. In contrast, the filament 1 of the electron gun of the present embodiment has the longest durability time and the shortest durability time. The difference is about 200 hours. Therefore, variations in the durability time between the individual filaments of the electron gun 1 can also be suppressed.

Further, the above embodiment can be implemented by appropriately changing as follows.

‧ The electron gun 10 is not limited to the above configuration. For example, the electron gun 10 may further include a focus coil and a flow regulator.

The number of the bends 1c constituting the curved portion 1a of the filament 1 for the electron gun or the shape of the curved portion 1a is not limited to the above-described number and shape. For example, the number of the bends constituting the curved portion 1a can be arbitrarily set, and the shape of the curved portion 1a can be a concave-convex curve extending in a direction crossing the longitudinal direction of the wire P1. Further, the shape of the curved portion 1a may be a so-called spiral type.

‧ Although the thickness of the metal plate is set to 0.5 mm, the present invention is not limited thereto, and may be arbitrarily changed, for example, according to the output obtained by the electron gun 10.

‧ The conditions of the wire discharge machining, for example, the magnitude of the voltage applied between the tool wire electrode WE1 and the metal plate P, or the machining feed speed as the moving speed of the metal plate P, etc., can be processed according to the shape of the filament or the wire discharge machining The performance of the device WE is arbitrarily set.

‧ The cutting of the filament 1 for the electron gun from the metal sheet P is performed by wire electric discharge machining, and is not limited thereto. For example, other processing methods such as a water jet method can also be used. The water jet method refers to a method of cutting the metal sheet P or the like by using water that has been passed through a hole of about 0.1 mm to 1.0 mm and pressurized to, for example, about 300 MPa. For example, the water flow is set to 500 m/s to 800 m. /s.

‧ In addition, an abrasive jet method in which a polishing material is mixed in a pressurized water stream to perform processing may be employed.

‧ The material forming the metal plate P, in other words, the material forming the filament 1, is made of tungsten. It is not limited thereto, and an alloy containing tungsten may be used as a material for forming a filament. Alternatively, tungsten is used as a filament material instead of other metal materials such as tantalum. Since the work function of tantalum (Ta) is smaller than the work function of tungsten (W), helium emits the same amount of hot electrons at a temperature lower than that of tungsten. For example, as shown in Fig. 10, a temperature of 1.2 A/cm ² of hot electrons is obtained, which is about 2500 K for lanthanum and about 2640 K for tungsten. Thus, by replacing the tungsten with ruthenium, the temperature of the filament 1 can be lowered by about 140K.

‧ The metal material which is a constituent material of the filament 1 for an electron gun is generally an aggregate of crystal grains, and such crystal grains are expanded in size by heating. When the heating conditions are increased in temperature or long-term, the crystal grains are coarsened in the filament 1 for the electron gun, and the filament 1 may be embrittled due to this. Therefore, the metal plate P is formed of a single plate material, but it may be modified to form a filament by using a metal laminated plate composed of a plurality of metal plates. According to this configuration, the following effects can be obtained. that is:

(6) Compared with the case of using a sheet material composed of a single metal plate, the thickness of each metal plate can be reduced, and the coarsening of crystal grains in the thickness direction of the metal plate can be naturally suppressed or even improved. The strength and life of the filament for the electron gun.

‧ A material such as a thin metal plate is formed by a rolling method. Generally, the higher the rolling rate, the more the mechanical strength of the rolling direction and the mechanical properties in other directions are different. For example, there is a tendency that the modulus of elasticity, the strength of the fall, the tensile strength, and the like are the largest in the direction perpendicular to the rolling direction, and the smallest in the direction parallel to the rolling direction, and the tendency to stretch is on the other hand. The rolling direction is the smallest in the vertical direction and the largest in the direction parallel to the rolling direction. Therefore, if the filament 1 for an electron gun is formed by a metal composed of a single plate material, the mechanical strength cannot be maintained to a desired level in a specific direction. Therefore, when the above laminated plate is used, it is preferable to laminate a plurality of metal plates so that the rolling directions of the respective metal plates cross each other. According to this configuration, in addition to the above (6), the following effect (7) can be obtained.

(7) The mechanical characteristics of the metal plates constituting the laminated board can be complementary, and the mechanical strength of the laminated board can be improved, and even the machine for the filament of the electron gun formed by the wire cut out from the laminated board can be improved. strength.

Incidentally, the effect of (7) is most remarkable when the metal plates adjacent to each other are laminated with each other in such a manner that the rolling direction thereof is perpendicular.

‧ In addition, when the laminated plate is used, a plurality of metal materials different from each other may be formed. Thereby, the following effect (8) can be obtained.

(8) In the laminated plate, since the adjacent metal plates are made of mutually different metal materials, the laminated plate obtained by laminating a plurality of metal plates composed of the same metal material is used. It is also possible to suppress the crystal grains constituting one metal plate from being coarsened beyond the thickness of the metal plate composed of the crystal grains. Further, the coarsening of the crystal grains in the thickness direction of the laminated plate can be restricted to the thickness of the metal plate to which the respective crystal grains belong.

‧ In addition, when a laminated plate is formed by using a different metal plate, the metal plate of the filament 1 for the electron gun disposed on the side opposite to the cathode electrode 2 may be made of a material having a smaller work function than other metal plates. . For example, a filament laminated wire made of a tungsten (W) metal and a tantalum (Ta) metal may be used to form a filament. Fig. 11 is a view schematically showing the configuration of the filament 41 of the second embodiment which is formed by using a W-Ta laminated plate of a base metal plate 42 and a tungsten metal plate 43. In the electron gun 10 using the filament 41, the base metal plate 42 is disposed to face the cathode electrode 2, and the tungsten metal plate 43 is disposed on the opposite side of the cathode electrode 2. That is, the base metal plate 42 includes a cathode opposing surface 1s. The filament 41 is formed by joining the base metal plate 42 to the tungsten metal plate 43 to obtain a W-Ta laminated plate, and then cutting the wire from the W-Ta laminated plate. Further, instead of joining the metal plates 42, 43, by spraying the base metal to the tungsten metal plate 43, or by vapor-depositing the tungsten metal to the base metal plate 42, a W-Ta laminated plate can be formed. In other words, the tungsten wire can also be cut out from the tungsten metal plate 43, and the filament 41 can be formed by spraying the base metal into the tungsten wire. Alternatively, the tantalum wire is cut out from the base metal plate 42, and the filament 41 is formed by evaporating tungsten metal into the tantalum wire. As described above, the lanthanide system can release the same amount of hot electrons as the temperature at a lower temperature than tungsten (refer to Fig. 10). Therefore, compared with the filament 1 of the first embodiment, the second embodiment can suppress the temperature rise of the filament 41 and prolong the average durability time (average life). Fig. 12 is a graph showing the filament life of Example 1 and the filament life of Example 2. As shown in Fig. 12, the average life of the filament 1 of Example 1 was 700 hours, whereas the average life of the filament 41 of Example 2 was 838 hours. Thus, Example 2 can also extend the average life expectancy by about 1.2 times compared to Example 1. Here, the lanthanide can efficiently emit hot electrons at a lower temperature, and on the other hand, it is inferior in tensile strength at a high temperature compared to tungsten. Therefore, when the W-Ta laminated board is used, the temperature rise of the filament 41 can be suppressed while ensuring sufficient strength of the filament 41. In other words, the filament 41 of Embodiment 2 has the following advantages.

(9) The filament 41 is formed using a W-Ta laminated plate of a base metal plate 42 and a tungsten metal plate 43. When the filament 41 is placed on the electron gun 10, the base metal plate 42 is disposed opposite to the cathode electrode 2. The lanthanide releases hot electrons at a lower temperature than tungsten. Therefore, the filament 1 of the first embodiment formed by bending a single material or the filament 1 of the first embodiment formed by cutting a wire from a single metal sheet can also suppress the opposing of the cathode electrode 2. The temperature of the metal plate (i.e., the base metal plate 42) rises. Further, the temperature rise of the tungsten metal plate 43 can be suppressed, and the temperature rise of the filament 41 itself can be suppressed. Therefore, deformation of the filament 41 toward the cathode electrode 2 side can be suppressed as compared with the first embodiment.

‧ A filament can also be formed using three or more metals (or metal plates) having different work functions. In this case, it is preferable that the filament is formed such that the metal having the lowest work function is disposed opposite to the cathode electrode of the electron gun.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed.

1. . . Electron gun filament

1a. . . Bending

1b. . . Foot

1c. . . bending

1s. . . Cathode opposite

P. . . Metal plate

P1. . . Wire

Ps. . . Machined surface

Pi. . . Imaginary plane

WE. . . Wire electric discharge machining device

WE1. . . Tool wire electrode

WE2. . . Processing power

WE3. . . NC device

W. . . metal wires

100. . . filament

100a. . . Bending

100b. . . Foot

D. . . Irradiation direction

2. . . Cathode electrode

3. . . Vernett electrode

4. . . Anode electrode

5. . . Flow regulator

6. . . Focus coil

7. . . Swing coil

8. . . Ion collector

9. . . framework

9a. . . Flange

10. . . Electron gun

EB. . . Electron beam

A. . . Optical axis

30. . . Evaporation chamber

31. . . Evaporating material

twenty one. . . Filament power supply

twenty two. . . Cathode power supply

twenty three. . . Acceleration power supply

41. . . filament

42. . . Base metal plate

43. . . Tungsten metal plate

Fig. 1(a) is a perspective view showing a metal wire used for a conventional filament for an electron gun; and Fig. 1(b) is a perspective view showing a manufacturing step of a filament for a conventional electron gun.

Fig. 2 is a perspective view showing a schematic configuration of a filament for an electron gun according to an embodiment of the present invention.

Fig. 3 (a) to (d) are schematic views showing the steps of manufacturing the filament for an electron gun of Fig. 2;

Fig. 4 is a schematic view showing the configuration of an electron gun to which the filament for an electron gun of Fig. 2 is applied.

Fig. 5 is a graph showing the relationship between the input power of the filament for the electron gun of Fig. 2 and the output of the electron beam.

Figure 6 is a graph showing the relationship between the input power to the cathode electrode and the output of the electron beam.

Fig. 7 is a graph showing the relationship between the input power of the filament for the electron gun and the output of the electron beam when the cathode electrode is changed.

Fig. 8 (a) and (b) are graphs showing the results of evaluation of the stability of the electron beam.

Fig. 9 is a graph showing the durability time of the filament for the electron gun of Fig. 2.

Fig. 10 is a graph showing a comparison of the thermal electron radiation densities of tungsten and tantalum which can be applied to the material of the electron gun filament of Fig. 2.

Fig. 11 is a view showing a schematic configuration of a filament for an electron gun of Example 2 in which a W-Ta laminated plate of a tungsten metal plate and a base metal plate is used for the filament for an electron gun of Fig. 2.

Fig. 12 is a graph showing the life of the filament of Example 1 using only a tungsten metal plate and the life of the filament of Example 2 using a W-Ta laminated plate.

1. . . Electron gun filament

1a. . . Bending

1c. . . bending

1s. . . Cathode opposite

P. . . Metal plate

P1. . . Wire

Ps. . . Machined surface

Pi. . . Imaginary plane

WE. . . Wire electric discharge machining device

WE1. . . Tool wire electrode

WE2. . . Processing power

WE3. . . NC device

Claims (5)

A method for manufacturing a filament for an electron gun, comprising the steps of: preparing a sheet material composed of a metal material; and cutting out one of the filaments having at least one bend from the sheet material; wherein the step of preparing the sheet material comprises: a step of preparing a metal laminated plate composed of a plurality of metal plates laminated in a thickness direction of the plate, the plurality of metal plates being separately rolled, and the plurality of metal plates being rolled by each of the metal plates The rolling directions are laminated in such a manner that the rolling directions cross each other. A method for manufacturing a filament for an electron gun, comprising the steps of: preparing a sheet material composed of a metal material; and cutting out one of the filaments having at least one bend from the sheet material; wherein the step of preparing the sheet material comprises: a step of preparing a metal laminated plate composed of a plurality of metal plates laminated in a thickness direction of the plate, and when the filament is mounted on the electron gun, the bending of the filament is set to a cathode electrode of the electron gun Opposite, and heated by a current supplied from a power source to release hot electrons for heating the cathode electrode, the step of preparing the metal laminate comprises: having a minimum among the plurality of metal plates A metal plate of a work function, and a step of forming a metal plate opposite to the cathode electrode. A method for manufacturing a filament for an electron gun, comprising the steps of: preparing a sheet material composed of a metal material; and cutting out one of the filaments having at least one bend from the sheet material; wherein the step of preparing the sheet material comprises: A step of preparing a metal laminated plate composed of a tantalum metal plate and a tungsten metal plate. A method for manufacturing a filament for an electron gun, comprising the steps of: preparing a sheet material composed of a metal material; and cutting out one of the filaments having at least one bend from the sheet material; wherein the electron gun is cut out from the sheet material The step of the wire of the filament comprises the step of cutting the wire from the sheet by wire electrical discharge machining. A filament for a gun for an electron gun, characterized in that it is formed by a metal material and comprises a wire having at least one bend, and the wire has a rectangular cross section; wherein the wire is used to comprise a plurality of metal plates Formed by a metal laminated plate, the electron gun includes a cathode electrode disposed opposite to the filament, wherein the filament is disposed opposite to the cathode electrode by a metal plate having a minimum work function among the plurality of metal plates The way is formed.