JPH0418408B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron gun processing method using a high-intensity electron beam from a specific crystal plane in an electron gun equipped with a single crystal lanthanum boride cathode.

It is known that single-crystal lanthanum bolide has a work function that differs depending on the crystal orientation, and it has been proposed that thermionic radiation from crystal planes with a low work function can be effectively utilized. However, it is said that the axial orientation of the single crystal lanthanum boride cathode chip, which has a pointed tip, has a low work function.
When we measure the brightness in the 210><110> direction, we get a slightly lower value than the brightness in the <100> direction.

In the present invention, each time an electron gun is used, a single-crystal lanthanum boride cathode is subjected to vacuum heat treatment under certain conditions, thereby increasing the radiation current from a specific crystal plane according to the treatment conditions. This is based on the knowledge that

That is, by heating the single crystal lanthanum boride cathode installed in the electron gun at 1500°C for 60 seconds or more in a vacuum of 1×10 ^-7 Torr or less before use, electron emission from the 210 plane is eliminated. Similarly, using electron emission from the 310 plane by heat treatment at 1500°C for 60 seconds or more at a degree of vacuum in the range of 2 × 10 ^-7 Torr to 5 × 10 ^-6 Torr, The present invention also relates to an electron gun that utilizes electron radiation from the 110 plane by heating to a working temperature of 1000° C. or higher at 5×10 ⁻⁶ Torr or higher.

A detailed explanation will be given below based on examples.

The longitudinal direction of a single crystal lanthanum boride with a diameter of 2 mm and a length of 10 mm is set in the <110> direction, the tip is mechanically polished into a hemispherical shape, and the hemispherical part is placed as a cathode tip. Heated. The first cover 3 and the second cover 4 prevent light and thermoelectrons from leaking from the tantalum coil, making it easier to observe the emission pattern. The inside of the hemispherical dome 5 made of glass is coated with conductive fluorescent paint 6 so that the pattern of the emitted electron beam can be observed. By comparing the central angle of the spot projected onto the glass spherical surface by this device with the corresponding angle in the stereo projection view, it is possible to determine which electron gun the spot corresponds to. As a result of conducting experiments using this apparatus while varying the degree of vacuum and heat treatment conditions, the relationship between the vacuum heat treatment conditions and the subsequent radiation surface of the high-intensity beam was as follows.

Example 1 When impurities on the surface of single crystal lanthanum boride are removed by heating at 1500°C for 60 seconds in a vacuum below 1×10 ^-7 Torr, and after 90 minutes, the temperature is kept at 1050°C, the stereo as shown in Figure 2 is produced. As shown in the projection diagram, a point with high brightness appeared at a location corresponding to the 210th plane. Since the same emission pattern can be obtained no matter how many times this is repeated, it is possible to obtain the same emission pattern no matter how ^{many times} it is repeated.
It turns out that it is advantageous to utilize the electron emission from the 210 plane by heating for more than a second.

Under conditions other than the above, for example, when the degree of vacuum is around 10 ^-6 Torr, or when the degree of vacuum is 1 x 10 ^-7 Torr but the cathode temperature is 1400°C, and if the processing time is less than 60 seconds, It was confirmed that no high brightness points appeared in the area corresponding to the surface.

Example 2 Heating at 1500°C for 60 seconds at a vacuum level of 2×10 ^-7 Torr or more and 5×10 ^-6 Torr or less, then 2×
When the vacuum level is 10 ^-5 Torr and the temperature is kept at 1050℃, the third
As shown in the stereo projection diagram in the figure, the points with high brightness could be fixed at 310 planes.

If the degree of vacuum is 1×10 ^-7 Torr or 1×10 ^-5 Torr, or if only the cathode temperature is 1400℃, then 310
I couldn't get a strong emission from the front.

Example 3 After heating at 1050℃ for 10 hours under a vacuum condition of 5×10 ^-6 Torr or more, the emission pattern changes and the luminance becomes high when the temperature is kept at 1050℃ under a vacuum of 1×10 ^-7 Torr or less. The point was identified as plane 110, as shown in the stereo projection diagram of FIG.

Under processing conditions other than the above, a high-intensity beam of 110 planes could not be obtained.

In each of the above experiments, the cathode temperature was set at 1050°C when observing the emission pattern because the brightness of the fluorescent surface was most appropriate and it was easy to observe. Even when the temperature was increased, electron emission from the crystal planes corresponding to each vacuum heat treatment condition was observed.

Those subjected to vacuum heat treatment as shown in Examples 1, 2, and 3 have a lower total radiation current than those without treatment.
It has increased more than 10 times. This increase in radiation current is thought to be due to gas molecules adsorbed on the cathode surface.

In the case of Example 1, there are 210 faces, and in Example 2, there are 3 faces.
Adsorption of hydrogen, helium, and oxygen was observed on the 10th surface, and on the 110th surface of Example 3, respectively. That is, it is clear that these adsorbed gas molecules contribute to an increase in the radiation current.

As is clear from the above, it is possible to specify the crystal plane that emits a high-intensity beam through pre-processing operations, and this allows the crystal plane to be used to be part of the part that emits electrons onto the substantial surface of the cathode chip. Therefore, it is possible to provide an electron gun configured to exist.

For example, in the case of a chip with an axial orientation of <210> and a conically pointed tip, or a chip with a 210 facet on a part of the pyramidal surface, a vacuum of 1×10 ^-7 Torr or less is required.
By pre-treatment heating at 1500°C for 60 seconds, it is possible to generate and utilize a high-intensity electron beam that cannot be obtained using conventional methods.

In addition, for example, a device with a 310 crystal plane formed at the tip can lower the cathode temperature and produce high current even in equipment with poor vacuum, such as an electron beam welder, by manipulating the processing conditions as in Example 2. Since a high-density beam can be obtained, the cathode can be used for a long time.

Note that the effect of the preheating treatment in the present invention is not an effect that is maintained forever.

When the adsorption of gas molecules such as hydrogen, helium, and oxygen that contribute to the increase in radiation current is lost for some reason, that is, when the output of the electron beam becomes weak, it is necessary to repeat the process under the same conditions. be.

[Brief explanation of drawings]

FIG. 1 is an apparatus for observing emission patterns based on changes in specific crystal planes according to the present invention. FIGS. 2 to 4 are stereo projection diagrams of high-intensity spots, respectively. 1 is a single crystal lanthanum boride cathode, and 5 is a glass dome coated with fluorescent paint.

Claims (1)

[Claims] 1. When using an electron gun equipped with a single-crystal lanthanum boride cathode, the cathode must be
A high-brightness electron gun equipped with a single-crystal lanthanum boride cathode characterized by being vacuum heat-treated at 10 ^-7 Torr or less at 1500°C for 60 seconds or more to utilize only electron emission from 210 crystal planes. Processing method. 2. When using an electron gun equipped with a single-crystal lanthanum bolide cathode, the cathode must be
1500℃, 60 at 10 ^-7 Torr or more and 5 × 10 ^-6 Torr or less
A method for processing a high-intensity electron gun equipped with a single-crystal lanthanum boride cathode, characterized in that vacuum heat treatment is performed for more than a second, and only electron emission from 310 crystal planes is used. 3. When using an electron gun equipped with a single-crystal lanthanum bolide cathode, the cathode must be
High brightness electrons equipped with a single-crystal lanthanum boride cathode characterized by being subjected to vacuum heat treatment at a temperature of 10 ^-6 Torr or higher and 1000°C or higher for 10 hours or more to utilize only electron emission from 110 crystal planes. How to dispose of guns.