JPH05174757A - Electron gun device - Google Patents

Abstract

PURPOSE:To generate an electron beam of uniform beam current by providing bombarding power supplies between a plurality of line-form filament and cathodes. CONSTITUTION:Filaments 1a, 1b are connected with filament heating power supplies 20a, 20b, respectively. A bombarding power supply 21a/21b is connected between the filament 1a/1b and a cathode 3a/3b. Thereby ununiformity in the cathode temp. distribution due to different power input between the left and right of cathode is corrected by adjusting the power supplies 20a, 20b to generate uniform heating of cathode, and the electron beam emitted by an electron gun is measured by a Faraday cup etc. to serve for controlling the power supplies 21a, 21b, and thereby the current density of the electron beam can be made uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun device, and more particularly to an electron gun device which outputs a linear electron beam.

[0002]

2. Description of the Related Art One type of electron gun device is configured to output a linear electron beam.

FIG. 2 is a conceptual block diagram of such an electron gun device. In the figure, 1a and 1b are filaments formed in a line shape, each having a length of about 100 mm, and emit first thermoelectrons 2 in response to energization. Three
Each of a and 3b is a linear cathode having a length of about 100 mm, and is arranged so as to face the filaments 1a and 1b at a constant interval. The cathodes 3a and 3b are supported by a cathode support 4, but a support 5 is provided at a connecting portion between the cathodes 3a and 3b so that the cathode does not hang downward due to gravity at the connecting portion. There is. Cathode 3a,
3b has a predetermined potential difference with respect to the filaments 1a and 1b. The first thermoelectrons 2 emitted from the filaments 1a and 1b are accelerated by the potential difference, and the cathode 3
It collides with a and 3b and heats the cathodes 3a and 3b. The cathodes 3a and 3b emit second thermoelectrons 6 in response to heating.

Reference numeral 7 is a grid, which is composed of filaments 1a,
It is fixed to the end surface of the first cover 8 including 1b. The grid 7 controls the focusing state of the second thermoelectrons 6 output from the cathodes 3a and 3b. Reference numeral 9 denotes an anode, which is fixed to the inner circumference of the opening of the second cover 10. The anode 9 accelerates the second thermoelectrons 6 whose focusing is controlled by the grid 7 and extracts them as an electron beam 11.

Incidentally, for example, when no accelerating voltage is applied to the cathodes 3a and 3b, the filaments 1a and 1b are
2KV is applied, the cathodes 3a, 3b are kept at 0V, and -6KV is applied to the grid 7. As a result, the potential difference between the filaments 1a and 1b and the cathodes 3a and 3b becomes 2 KV, and the cathodes 3a and 3b and the grid 7 are separated.
Has a potential difference of 6 KV, and the filaments 1a, 1b and the grid 7 have a potential difference of 4 KV. And cathode 3
The a and 3b are heated to a high temperature of 2000 ° K or higher by the impact of the first thermoelectrons output from the filaments 1a and 1b.

FIG. 3 is a simplified diagram of the power supply connection of the electron gun device. The filaments 1a and 1b are electrically connected,
Each is electrically heated by the filament heating power source 12. Also, the filaments 1a and 1b and the cathodes 3a and 3
A bombardment voltage for causing the thermoelectrons generated from the filaments 1a and 1b to collide with the cathodes 3a and 3b is applied from the bombarding power source 13 between the two. 14 is a grid power supply, and 15 is an acceleration power supply.

[0007]

Experiments have revealed that the following problems occur in the above-described power source connection state.

First, when a voltage of 30 V is applied from the filament heating power source 12 between both terminals of the filaments 1a and 1b, the average voltage values applied to the filaments 1a and 1b are Va and Vb, respectively. Is as follows:

Va <Vb Next, assuming that a bombarding voltage of 2 kV is uniformly applied to both the cathodes 3a and 3b in the longitudinal direction, the potential difference between the cathode 3a and the filament 1a is Ea, and the potential difference between the cathode 3b and the filament 1b is Eb, E
The relationship between a and Eb is as follows.

Ea> Eb Here, assuming that the potential difference between the cathode and the filament and the emission current flowing from the filament to the cathode are E and I, the emission current I considering the space charge effect is given by the following equation. It should be noted that Ia is the potential difference and emission current on the filament 1a side, and Ib is the potential difference and emission current on the filament 1b side.

[0011]

[Equation 1]

[0012]

[Equation 2]

[0013] In the above equation, epsilon ₀ is the vacuum dielectric constant, m is the electron mass, the distance between _{d a} cathode 3a- filament 1a (m), _{d b} is the cathode 3b- filament 1b
The distance (m), A, is the effective emission area (m ² ) of the filament.

When the electric powers applied to the cathodes 3a and 3b are Pa and Pb, respectively, Pa = Ia.Ea and Pb = Ib.Eb. For _{d a} = d _b, the Ea> Eb Ia> Ib
Therefore, Pa> Pb.

As described above, the electric powers supplied to the cathodes 3a and 3b are different from each other.
As shown in FIG. 4A, the temperatures of 3 and 3b are locally different. That is, the cathode 3a portion is
Since the input power is large, the temperature becomes higher than that at the cathode 3b portion. As a result, the current density of thermoelectrons radiated from the cathode differs depending on the temperature of the cathode, as shown in FIG.

Further, the conventional device of FIG. 2 has the following problems. When assembling the electron gun, the cathode and filament are attached individually to the left and right, but there is a limit to their attachment accuracy, and the cathode and filament are equipped with a non-fixed type support mechanism to absorb thermal expansion. The backlash due to this is 0.2 mm in the direction of thermionic emission.
The left and right cathodes may differ due to factors such as
In setting the distance between filaments, it is difficult at present to keep the difference between the left and right distances within 0.1 mm.

The inventors of the present invention forcibly change the distance d _a between the filament 1a and the cathode 3a and the distance d _b between the filament 1b and the cathode 3b in the device shown in FIG. An experiment was conducted to find out how the difference between the average temperatures of the left and right cathodes causes a step difference. FIG. 5 shows the results of this experiment, where the horizontal axis is the difference in distance between the left and right filaments and the cathode, and the vertical axis is the difference in average temperature between the left and right cathodes. As is clear from this figure, the distance difference is 0.
Since a temperature difference of about 80 ° K occurs at 2 mm, it is necessary to make this distance difference half of 0.2 mm or less, and at least 0.1 mm or less. However, it is currently difficult to set the distance difference to 0.1 mm or less as described above.

Further, in the above equations (1) and (2), if Ea = Eb,

[0019]

[Equation 3]

[0020] As is clear from this equation, the difference in distance between the left and right filaments-cathode affects the cathode input power, causing a step difference in the left and right cathode average temperatures. This causes more steps in the current density distribution of the electron beam from the cathode shown in FIG.

The present invention has been made in view of the above problems, and an object thereof is to realize an electron gun apparatus capable of obtaining an electron beam having a uniform beam current in the longitudinal direction.

[0022]

According to another aspect of the present invention, there is provided an electron gun apparatus in which first thermoelectrons emitted from a plurality of linear filaments are made to collide with a linear cathode, and a second cathode is emitted from the cathode. The electron gun device configured to generate thermionic electrons is characterized in that a power source for bombardment is provided between each filament and the cathode.

In the electron gun apparatus according to the second aspect of the invention, the first thermoelectrons emitted from the plurality of linear filaments collide with the linear cathode, and the second thermoelectrons are generated from the cathode. In the electron gun device configured as described above, a power source for filament heating is connected to each of the plurality of filaments, and a power source for bombardment is provided to each filament.

[0024]

Operation: A power source for bombardment is connected between each of the plurality of filaments and the cathode so that the bombardment voltage between the plurality of filaments and the cathode can be adjusted separately to uniformly heat the cathode.

Further, a heating power source is connected to each of the plurality of filaments, a bombardment voltage is independently supplied to each of the plurality of filaments, the heating power source of each of the plurality of filaments is adjusted, and the bombardment voltage is independently controlled. Uniform heating of the cathode is performed by adjusting.

[0026]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a main part of an electron gun device according to the present invention, and the same parts as those in FIG. 3 are denoted by the same reference numerals.
Filament heating power sources 20a and 20b are connected to the filaments 1a and 1b, respectively. In addition, a bombard power source 21 is provided between the filament 1a and the cathode 3a.
a is connected, and a bombard power source 21b is connected between the filament 1b and the cathode 3b.

In the above structure, each filament 1
a and 1b are independently heated by the heating power sources 20a and 20b, and the potential difference between the filament and the cathode is
Each can be independently adjusted by the bombard power sources 21a and 21b. Therefore, it is possible to uniformly heat the cathode by adjusting the nonuniformity (step) of the cathode temperature distribution due to the difference in the input power to the left and right of the cathode described above so that the input power to the left and right of the cathode have the same value. In addition, the electron beam output from the electron gun is measured by a Faraday cup or the like, and if the current density of the beam from the cathode 3a is higher than the current density of the beam from the cathode 3b, the bombard power supply 21a is controlled. To lower the voltage between the filament 1a and the cathode 3a or control the bombard power source 21b to
The voltage between b and the cathode 3b is increased. As a result,
The current density of the beam emitted from the cathodes 3a and 3b can be uniformly controlled in the longitudinal direction. Further, it is effective to control not only the bombard power supply but also the filament heating power supplies 20a and 20b.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the filament and the cathode are divided into two, but may be divided into three or more.

[0029]

As described above, according to the present invention, a bombard power source is provided between each of the plurality of filaments and the cathode so that the bombard voltage can be independently applied between each filament and the cathode. I configured it, so
By adjusting the bombarding power, the cathode can be heated uniformly in the longitudinal direction, and thus an electron beam having a uniform beam current in the longitudinal direction can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an electron gun apparatus according to an embodiment of the present invention.

FIG. 2 is a conceptual configuration diagram of a conventional electron gun device.

FIG. 3 is a diagram showing a power supply connection state of a conventional device.

FIG. 4 is a diagram showing the relationship between the position of the cathode, the temperature of the cathode, and the current density of the electron beam.

FIG. 5 is a diagram showing a relationship between a left-right cathode-filament distance difference and a left-right cathode average temperature difference.

[Explanation of symbols]

 1 Filament 3 Cathode 7 Grid 9 Anode 12 Heating Power Supply 13 Bombarding Power Supply 20a, 20b Heating Power Supply 21a, 21b Bombarding Power Supply 22a, 22b Bombarding Power Supply

Front page continued (72) Inventor Ikuo Wakamoto 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries Ltd. Hiroshima Research Institute (72) Inventor Toru Takashima 3-12 Musashino, Akishima-shi, Tokyo Inside JEOL Ltd.

Claims (2)

[Claims] 1. An electron gun apparatus configured to cause a line-shaped cathode to collide with first thermoelectrons emitted from a plurality of line-shaped filaments to generate second thermoelectrons from the cathode. An electron gun device characterized in that a power source for bombardment is provided between each filament and the cathode. 2. An electron gun device configured to cause a first thermoelectron emitted from a plurality of linear filaments to collide with a line cathode to generate a second thermoelectron from the cathode, An electron gun device characterized in that a power source for heating a filament is connected to each of a plurality of filaments, and a power source for a bombard is provided to each filament.