JPH05174702A - Heater for long cathode - Google Patents

Abstract

PURPOSE:To obtain a long electron beam uniform in output density by narrowing the intervals between both ends of a cathode and a filament as compared with that at the center of the cathode, and making the length of the filament longer than that of the cathode. CONSTITUTION:Since the length I2 of a filament is longer than that I1 of a cathode, the center of the filament where the temperature distribution is uniform heats the cathode by electron shock, but both ends of the filament at low temperature does not contribute to the heating by electron shock. In short, it functions as a filament only in the area where the temperature distribution is uniform. Furthermore, on both ends of the cathode, the intervals to the filaments are narrower 2 than that of the center, so the quantity of heating by electron shock increases. Therefore, even if heat is conducted to a supporting plate 11, both ends of the cathode never falls to low temperature as compared with the center. Namely, the temperature can be equalized over the whole length the cathode 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for a long cathode of an electron gun used as a heat source for generating metal vapor in a vacuum.

[0002]

2. Description of the Related Art FIGS. 4A and 4B show a conventional linear electron gun. As shown in both figures, a long filament 2 is arranged in parallel behind a long cathode 1, and the distance between the cathode 1 and the filament 2 is a constant distance x ₂ over the entire length. A direct current is applied to the filament 2 from the filament power source 7, and the filament 2 emits thermoelectrons.
The emitted thermoelectrons are emitted from the bombard power source 8 to the cathode 1.
Is accelerated by an acceleration voltage applied to the cathode 1 to form an electron beam 6, which heats the cathode 1 by an electron impact. As a result, the electrons emitted from the cathode 1 are accelerated by the acceleration voltage applied to the anode 3 to become a long linear electron beam 5, which is used as a high power density heating source.
The anode 3 is installed on both front sides of the cathode 1, and an acceleration voltage is applied by an acceleration power supply 9. In the figure, 4 is a grid, 10 is a grid power supply, and these are used for controlling the beam current and the light focusing property.

Both ends of the cathode 1 are supported by support plates 11, and the support plates 11
Represents the thermal expansion of the cathode 1.

[0004]

As described above, in the conventional linear electron gun, the filament 2 which is arranged in parallel with the cathode 1 and has a length substantially the same as the cathode length is electrically heated, and the filament 2 and the cathode 1 are further heated. By applying an accelerating voltage between the two, the cathode 1 is electron-impact heated.

However, in spite of the demand to make the cathode temperature uniform in order to secure the output uniformity in the linear electron gun, the conventional linear electron gun cannot satisfy such demand. It was

The reason for this is that both ends of the filament conduct heat to a support member (not shown) and the temperature drops, resulting in insufficient electron impact heating, and further, both ends of the cathode also have support members (support plate 11). ) To heat conduction, resulting in a large temperature drop.

The present invention has been made in view of the above-mentioned prior art, and provides a heating device for a long cathode capable of making the cathode temperature uniform in order to secure the output uniformity in the linear electron gun. The purpose is that.

[0008]

The structure of the present invention that achieves the above object emits thermoelectrons from a long filament arranged at the rear of a long cathode whose both ends are supported by supporting members. Then, in the apparatus for heating the cathode by electron impact, convex portions are formed on the rear surfaces of both ends of the cathode, and the interval between the convex portion and the filament is set to the central portion of the cathode other than the convex portion and the filament. It is characterized in that it is set to be narrower than the interval of and the filament is made longer than that of the cathode.

[0009]

[Function] Since the filament length is made longer than the cathode length, without using the low temperature portions at both ends of the filament,
A uniform temperature filament center can be used to electron impact heat the cathode. Also, both ends of the cathode are
Since the distance to the filament is narrower than that in the central portion of the cathode, the electron impact heating amount is increased, so that the temperature drop due to heat conduction to the support member is avoided.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. The same members as those in the conventional example shown in FIGS. 4A and 4B are designated by the same reference numerals and the description thereof will be omitted.

1A and 1B show a first embodiment of the present invention. As shown in both figures, convex portions are formed on the rear surfaces of both ends of the cathode 1. Therefore, the distance x ₃ between the cathode both ends (projections) and the filament 2 is narrower than the distance x ₂ between the cathode center and the filament 2. Further, the filament length l ₂ is the cathode length l
It is set longer than ₁ . The other structure is the same as that of the conventional example shown in FIG.

In the present embodiment having the above structure, since the filament length l ₂ is longer than the cathode length l ₁ , the central part of the filament having a uniform temperature distribution heats the cathode 1 by electron bombardment, but Does not contribute to electron impact heating. That is, only the range where the temperature distribution is uniform is made to function as a filament.

Further, since both ends of the cathode are closer to the filament 2 than the center thereof, the electron impact heating amount is increased. Therefore, the support plate 11
Even if heat is conducted to the both ends, the temperature at both ends of the cathode does not become lower than that at the central part. That is, the cathode 1 has a uniform temperature over its entire length.

For example, as a result of measuring the cathode temperature and its power density distribution in this example, as shown in FIG. 5, the cathode temperature distribution and the current density were uniform along the entire length of the cathode. Here, the cathode temperature distribution was measured with a radiation thermometer, and the power density distribution was measured with a Faraday cup. In addition, although the measurement result of the conventional example is also shown in FIG. 5 for comparison, a temperature drop occurs at both ends of the cathode,
The current density is also decreasing.

Next, a second embodiment of the present invention will be described with reference to FIG.
A description will be given with reference to (a) and (b). The feature of this embodiment is that two rod-shaped filaments 2a and 2b are used. By supplying currents to these filaments 2a and 2b in mutually opposite directions, the respective filaments 2a and 2b
The magnetic field created by b will be canceled. Other configurations, such as the shape of the cathode ₁ and the relationship between the cathode length l ₁ and the filament length l ₂ , are the same as in the above embodiment.

FIG. 3 shows a third embodiment of the present invention. This embodiment is applied when a long cathode is required, and two cathodes 1 shown in FIG. 1 are connected. That is, the two cathodes 1 are joined at one end with an intermediate support plate 13 sandwiched therebetween and supported by the intermediate support plate 13 and the support plates 11 at both ends of the cathode. Further, the filament 2 is also supported by the intermediate support member 14 at the center thereof. In this embodiment, the intermediate support plate 13 is additionally provided, but since the convex portion is also formed in the intermediate portion to which the cathode 1 is connected, it is possible to avoid a temperature decrease due to heat conduction through the intermediate support plate 13. Further, in this embodiment, two cathodes 1 are connected, but even if three or more cathodes 1 are connected, they can be similarly applied by sequentially connecting them.

[0017]

As described above in detail with reference to the embodiments, the heating apparatus for a long cathode of the present invention prevents the temperature drop due to heat conduction or the like at both ends of the cathode, and makes it uniform over the entire length of the cathode. Since it is possible to perform various heating, a long electron beam having a uniform power density distribution can be obtained. Therefore, in the linear electron gun using the present invention, it is possible to produce a long and uniform vapor, and various vapor depositions and the like can be performed widely and continuously.

[Brief description of drawings]

FIG. 1 (a) is a front view of a long cathode heating apparatus according to a first embodiment of the present invention. FIG. 3B is a side view of the heating device for the long cathode according to the first embodiment of the present invention.

FIG. 2A is a front view of a heating device for a long cathode according to a second embodiment of the present invention. (B) is a side view of a heating apparatus for a long cathode according to a second embodiment of the present invention.

FIG. 3 is a front view of a heating device for a long cathode according to a third embodiment of the present invention.

FIG. 4A is a front view of a conventional linear electron gun.
(B) is a side view of the conventional linear electron gun.

FIG. 5 is an explanatory diagram showing the principle and effect of the present invention and a conventional example in comparison.

[Explanation of symbols]

 1 cathode 2 filament 3 anode 4 grid 5,6 electron beam 7 filament power supply 8 bombard power supply 9 acceleration power supply 10 grid power supply 11 support plate 13 intermediate support plate 14 intermediate support member

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 Shigeo Konno 3-1-2 Musashino, Akishima-shi, Tokyo In Japan Electronics Co., Ltd. (72) Inventor Tadayoshi Otani 3-12 Musashino, Akishima-shi, Tokyo

Claims (1)

[Claims] 1. An apparatus for emitting thermoelectrons from a long filament arranged at the rear of a long cathode whose both ends are supported by support members to heat the cathode by electron impact. A convex portion is formed on the rear surface of both ends, and the distance between the convex portion and the filament is set narrower than the distance between the central portion of the cathode other than the convex portion and the filament, and further compared with the cathode. A heating device for a long cathode, characterized in that the filament is elongated.