JP2526303B2 - Linear filament type electron gun - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a linear filament type electron gun, and in particular, it is used as a heating source for generating a strip-shaped metal vapor stream, for increasing the efficiency of vapor stream generation. The present invention relates to a linear filament electron gun that can be used.

[Conventional technology]

As a conventional linear filament type electron gun, a linear filament (or cathode) having a length of about ten and several centimeters has been developed. However, a single device longer than that has not been developed at present, and in order to obtain a longer electron beam, at present, a plurality of linear filament type electron guns are arranged adjacent to each other to form a straight line in the longitudinal direction. It is necessary to arrange them side by side.

The structure of a conventional typical linear filament type electron gun will be described with reference to FIGS. 6 and 7. This linear filament type electron gun has substantially the same structure as the three-electrode type electron gun disclosed in, for example, Japanese Patent Publication No. 204340/1989, and the grid has a symmetrical positional relationship with respect to the linear filament and the like as described later. It is formed and installed in such a shape. FIG. 6 is an overall front view, and FIG. 7 is a partial plan view thereof. The details will be described below with reference to the drawings.

In FIG. 6, 601 is an anode, 602 is a grid, 60
3 is a filament. The anode 601 is a metal plate having a rectangular electron beam extraction hole 601a, and a metal support 604.
Is supported on the flange 605 and is generally held at ground potential. The grid 602 has a shape similar to that of the anode 601, and is formed of a metal plate. Reference numeral 602a is a rectangular electron beam extraction hole. Grid 602 is a supporting insulator 6
06 mounted on the flange 605 and supporting insulator 606
It is held in an insulated state by a negative potential. The potential of the grid 602 is applied through the grid current introduction terminal 607 and the grid lead wire 608. The filament 603 is formed of a material having a high electron emissivity such as tungsten, is supported by a filament support insulator 609, and has a flange 605.
Insulated from. A voltage is applied to the filament 603 from the filament current introduction terminal 610 through the filament lead wire 611. The linear filament type electron gun shown in FIG. 6 is called a direct heating type, and the filament 603 has the functions of a cathode as an electron emission source and a heater for heating the cathode. Filament 603 is 2000-25
It is held at a high temperature of about 00 ° C and at the same time, held at a negative potential of several tens of KV. The thermoelectrons emitted from the filament 603 are accelerated to generate electron beam extraction holes 6 in the grid 602.
It passes through 02a and the electron beam extraction hole 601a of the anode 601, and is emitted from the anode 601 as an electron beam. The grid 602 is held at a negative potential more than the filament 603 by a few KV, and has a function of suppressing and converging the divergence of the electron beam.

Further, as an example of arranging a plurality of electron guns in series, for example,
The one described in JP-A-62-219442 is known.

[Problems to be Solved by the Invention]

The conventional linear filament type electron gun having the above configuration has the following characteristics regarding the operating characteristics determined depending on its shape.

In FIGS. 6 and 7, the alternate long and short dash line A is a line indicating the center position of the linear filament type electron gun.
With respect to the center position line A, the opening length G _l and the length F _{l in} the major axis directions of the grid 602 and the filament 603, respectively.
Are defined to the left and right of it. In the configuration of the linear filament type electron gun shown in FIGS. 6 and 7, the grid 602 is used.
And the filament 603 are arranged symmetrically with respect to the center position line A. The current intensity distribution in the long axis direction of the electron beam generated by the linear filament type electron gun is determined depending on the relative relationship between the length F _l and the aperture length G _l . This will be described with reference to FIGS. 8 and 9.

In FIG. 9, the horizontal axis represents the ratio G _l / F _l , and the vertical axis represents the intensity distribution (peak / average) of the electron beam current in the long axis direction. In FIG. 9, when the ratio is about 1.5 or more, a divergent region is formed at the end of the electron beam in the long axis direction. This state is shown in FIG. In FIG. 8, the horizontal axis represents the position of the electron beam in the long axis direction, and the vertical axis represents the electron beam current intensity. When the ratio takes a value between about 1.1 and 1.5 in FIG. 9, the electron beam current intensity forms a flat region in which the top is flat and both ends rise as shown in FIG. 8 (b). When the ratio takes a value of about 1.1 or less, peaking regions where sharp rising peaks occur at both ends are formed as shown in FIG. 8 (c).

Data obtained by actually measuring the distribution characteristic of the divergent area, the distribution characteristic of the flat area, and the distribution characteristic of the peaking area shown in FIG. 9 are shown in (a), (b), and (c) of FIG. 10, respectively.
In this measurement, the acceleration voltage was 50 KV and the electron beam output was several hundred K.
It is about W.

Therefore, when a plurality of linear filament type electron guns are arranged adjacent to each other in the long axis direction and arranged in series to make a long linear filament type electron gun, when using a conventional linear filament type electron gun, The following problems occur due to the shape.

When the linear filament type electron guns having the electron beam current intensity characteristics shown in FIG. 8 (a) are connected in series, the electron beams are diverged at the outermost ends of all the aligned linear filament type electron guns, There is a problem that the utilization efficiency of the electron beam is reduced. There is also a risk of damaging the crucible and other containers. When the linear filament type electron gun having the electron beam current characteristic shown in FIG. 8B or 8C is connected in series, the problem that the electron beam diverges at both ends is eliminated, but This causes a problem that the electron beam current intensity between the two is greatly reduced.

Further, as described in JP-A-62-219442,
If a method of making the central filament length longer than the left and right filament lengths is applied to a long filament, there is a problem that the electron beam current density extracted from the central filament is reduced.

An object of the present invention is to obtain a sufficient electron beam current intensity between electron guns when a plurality of linear filament electron guns are connected in a longitudinal direction to form a long linear filament electron gun. It is to provide a long linear filament type electron gun capable of suppressing the divergence of the electron beam at the outermost end and satisfying the contradictory technical requirements.

[Means for solving the problem]

The linear filament type electron gun according to the present invention is a linear filament type electron gun in which a plurality of three-electrode type electron guns each including an anode, a grid and a filament are consecutively arranged in a long axis direction so as to be elongated. The filaments of the plurality of electron guns having the same length have the same length, and the shape in the long axis direction of the grid of the electron guns located at both ends is an asymmetrical shape.
Filament length F with respect to the center position of the filament
The ratio (Gι / Fι) of ι to the grid aperture length Gι is (Gι / Fι) ≧ 1.5 inside the grid and 1.1 <(Gι / Fι) <1.5 outside the grid. .

[Action]

In the linear filament electron gun according to the present invention, in consideration of the electron beam current density distribution characteristic determined by the dimensional relationship between the grid and the filament in the long axis direction, while keeping the filament length the same, The symmetrical shape in the long axis direction is stopped and this shape is made asymmetrical, and the ratio of the filament length Fι to the grid aperture length Gι with respect to the center position of the filament (Gι / F
i) is set to (Gι / Fι) ≧ 1.5 inside the grid and 1.1 <(Gι / Fι) <1.5 outside the grid, so that the optimal electron beam for a long linear filament electron gun is obtained. A current distribution characteristic can be generated.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a front view showing a first embodiment of a linear filament type electron gun according to the present invention. In this embodiment, two sets of filaments and grids are connected in a longitudinal direction.
One linear filament electron gun, which is a basic unit, is composed of one set of filament and grid. Reference numeral 1 is an anode, 2a and 2b are grids, and 3a and 3b are filaments. Grid 2a and filament 3a, grid 2b and filament
3b each constitutes a linear filament type electron gun, and the anode 1 is arranged in common for these electron guns. The anode 1 is supported by an anode column 4 standing on a flange 5, and has an electron beam extraction hole 1a. The grids 2a and 2b are respectively supported by support insulators 6a and 6b which are erected on the flange 5,
It has electron beam extraction holes 21a and 21b. The filaments 3a and 3b are supported by filament supporting insulators 7a and 7b which are erected on the flange 5, respectively. Reference numerals 8a and 8b are grid current introduction terminals for applying a required voltage to the grids 2a and 2b, respectively, and 9a and 9b are filament current introduction terminals. 10a and 10b are filament lead wires, respectively.

As described above, a voltage is applied from a separately installed filament power supply to a filament linear current introducing terminal to a long linear filament type electron gun in which two linear filament type electron guns are connected in series as described above. , 3b are independently heated to about 2300 ° C. and kept at about −30 KV with respect to the flange 5, which is the ground potential. Further, to the grids 2a and 2b, a negative potential lower than that of the filaments 3a and 3b by about 1 KV is independently applied from a separately installed grid power source through the grid current introduction terminals 8a and 8b. Since the anode 1 is electrically connected to the flange 5 via the anode support 4, it has a positive potential of about 30 KV with respect to the filaments 3a and 3b.

When the filaments 3a and 3b are heated to a high temperature, thermoelectrons are emitted from each filament. The emitted thermoelectrons are accelerated by the electric field formed between the anode 1 and the filaments 3a, 3b, pass through the electron beam extraction holes 21a, 21b and 1a as an electron beam having an energy of 30 KeV, and are emitted from the anode 1 It is released into the upper space. Each electron forming the electron beam repels each other due to its own negative charge, and the electron beam tends to diverge along its range. Therefore, the grid 2 located in the middle of the accelerating electric field
A predetermined negative potential is applied to a and 2b to focus the electron beam.

Next, the geometrical features of the grids 2a and 2b will be described. As shown in FIG. 1, with respect to the dimensional form of the electron beam extraction hole 21a in the long axis direction, the filaments 2a and 2b have G _{1 on} the outer side and G _{12 on} the inner side with respect to the center position line A, which are _asymmetrical . Has been formed. In this case G ₁ <
G _l2 , and in terms of the relationship between the lengths G ₁ and G _l2 and the length of the filament in the long axis direction, the grid generates the flat region in the region of the length G ₁ outside the center position line A. While the length G _l2 inside the center line A is
In the area of, the grid is formed so as to generate a divergent area. As a result, the electron beam emitted from the filament 3a diverges inward in FIG. 1, but hardly diverges outside. Similarly, filament 3b
The electron beam emitted from the laser also diverges inward, but hardly diverges outside. As a result, as shown in FIG. 2 (b), the electron beam intensity in the gap between the two filaments 3a and 3b is increased due to the mutual divergence action as a whole. The distribution is flat as compared with the electron beam intensity characteristic of the linear filament type electron gun having the configuration. The broken line in FIG. 2 (b) shows the intensity characteristic of the electron beam emitted from each of the filaments 3a and 3b. Then the third
A second embodiment of the present invention will be described with reference to FIGS. In this embodiment, three basic linear filament type electron guns are connected in series to form a longer linear filament type electron gun. In FIG. 3, elements that are substantially the same as the elements described in FIG. 1 are given the same reference numerals.

Reference numeral 1 is an anode, 1a is an electron beam extraction hole, 4 is an anode support, and 5 is a flange. As the number of linear filament type electron guns increases, the length in the major axis direction of each increases. Of the three grids 2a, 2b, 2c and the three filaments 3a, 3b, 3c, the grids 2a, 2b and the filaments 3a, 3b located on the left and right sides are the same as those described in the first embodiment. Therefore, the configuration around them, for example, the configuration of the grid current introduction terminal 8a and the filament current introduction terminal 9a, the electron beam extraction holes 21a, 21b of the grid
The characteristics such as the asymmetry regarding the shape in the long axis direction are the same as those in the first embodiment. On the other hand, the grid 2c located at the center is such that the dimension of the electron beam extraction hole 21c in the major axis direction is formed symmetrically with respect to the above-mentioned center position line and the length thereof forms a divergence region for the filament. It is formed with dimensions. Therefore, the electron beam emitted from the filament 3c has a characteristic of diverging to both sides. Further, the configuration of the filament 3c, the grid current introduction terminal 8a, the filament current introduction terminal 9a, etc. is the same as the other ones, and the electrical conditions are the same as those of the first embodiment.
This is the same as in the embodiment.

According to the long linear filament electron gun having the above structure, the electron beam diverges inside the linear filament electron guns on both sides, and the electron beams diverge on both sides at the central linear filament electron gun. Since it diverges at the part, it is possible to obtain the electron beam current intensity distribution as shown by the solid line in FIG. According to this embodiment, a relatively high electron beam current intensity can be obtained even in the gaps of the linear filament type electron guns 3a, 3b, 3c. Further, in the distribution of the electron beam current intensities at the outer ends of the linear filament type electron guns on both sides, there is almost no dispersion, and this point is the same as in the case of the first embodiment. In FIG. 4, broken lines indicate the electron beam current intensity distribution by each linear filament type electron gun.

In the second embodiment, three linear filament type electron guns are arranged in series, but the linear filament type electron guns on both sides are left as they are, and if the number of linear filament type electron guns in the central position is further increased, the linear filament type electron guns are further increased. It is possible to increase the number of guns connected in series, which makes it possible to further lengthen the linear filament type electron gun.

Although the filament is used as the electron generating means in the above-mentioned embodiment, even if a cathode that emits an electron and a heater that heats this cathode are used, a long dimensional relationship similar to the above is maintained while maintaining the same dimensional relationship in the long axis direction. A linear filament type electron gun can be manufactured. Further, the voltage is applied to each grid independently, but in principle it is also possible to collectively supply current from a single power source. However, even in such a case, it is desirable that the applied voltage can be adjusted for each grid.

Further, in a plurality of linear filament type electron guns connected in series, if at least one of the electron guns at both ends is configured as described above, the object of the present invention can be achieved.

FIG. 5 is a configuration diagram showing an example of use of the linear filament type electron gun according to each of the above-mentioned embodiments. In this embodiment, the metal 31 housed in the crucible 32 is irradiated with an electron beam 34 emitted from the linear filament electron gun 33 formed in a long length according to each of the above embodiments, and the metal
It is to evaporate 31. 35 is metal vapor, and the metal vapor 35 rises in the space surrounded by the vapor sealing plate 36,
Supplied to 37. The crucible 32 is arranged in a main vacuum container 38, and the main vacuum container 38 is made to have a predetermined vacuum state by a main vacuum pump 39. On the other hand, the linear filament type electron gun 33 is disposed in the sub vacuum container 40, and the sub vacuum container 40 is brought into a predetermined vacuum state by the sub vacuum pump 41. The electron beam 34 is radiated into the main vacuum vessel 38 through a window formed in a wall 42 at the boundary between the main vacuum vessel 38 and the sub vacuum vessel 40. A shutter device 43 that can be opened and closed is provided in this window.

〔The invention's effect〕

As is clear from the above description, according to the present invention, a plurality of existing linear filament type electron guns are used, and the linear filament type electron guns are arranged in series to effectively produce a long linear filament type electron gun. Further, by using a grid having an asymmetric shape, various electron beam current distributions can be generated according to the purpose.

[Brief description of drawings]

FIG. 1 is a front view showing a first embodiment of a linear filament type electron gun according to the present invention, and FIG. 2 is a graph comparing electron beam distribution characteristics of a linear filament type electron gun according to the present invention with conventional distribution characteristics, FIG. 3 is a front view showing a second embodiment according to the present invention, FIG. 4 is a graph showing an electron beam current distribution characteristic of the linear filament electron gun of the second embodiment, and FIG. 5 is a linear filament electron gun. 6 is a front view showing an example of a conventional linear filament type electron gun, FIG. 7 is a partial plan view of a conventional electron gun, and FIG. 8 is an electron beam current distribution characteristic. 9 is a characteristic diagram for explaining the relationship between the ratio of the grid aperture length to the filament length and the electron beam current distribution, and FIG. 10 is a graph for actually measuring various distribution characteristics. [Explanation of symbols] 1 ... Anode 1a ... Electron beam extraction hole 2a, 2b, 2c ... Grid 3a, 3b, 3c ... Filament 5 ... Flange 33 ... Linear filament electron gun

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Sano 3-1-1, Saiwaicho, Hitachi, Ibaraki Prefecture Hitachi Nuclear Engineering Co., Ltd. (72) Satoru Shibata 3-1-1, Saiwaicho, Hitachi, Ibaraki No. 1 Hitachi Ltd., Hitachi Plant (72) Inventor Nichio Kadota 3-1-1, Saiwaicho, Hitachi City, Ibaraki Hitachi Ltd., Hitachi Plant (56) References JP-A-62-219442 (JP) , A) JP 61-114449 (JP, A) JP 63-141246 (JP, A)

Claims (1)

(57) [Claims] 1. A linear filament electron gun in which a plurality of three-electrode type electron guns each comprising an anode, a grid and a filament are connected in a longitudinal direction in a continuous manner to obtain a linear filament type electron gun. The filament of the electron gun is
In addition to having the same length, the shape of the electron guns located at both ends in the long axis direction of the grid is asymmetrical, and this asymmetrical shape is the ratio of the filament length Fι to the grid opening length Gι with respect to the center position of the filament. (Gι
/ Fι) is (Gι / Fι) ≧ 1.5 inside the grid and 1.1 <(Gι / Fι) <1.5 outside the grid. A linear filament electron gun.