JPS606069B2 - Electron gun insulation structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an improvement in an insulator that supports an electron gun of an electron beam generator, and in particular, it makes uniform the potential distribution applied to the side wall of the insulator and reduces heat generated from a hot cathode. This invention relates to an insulated electron gun body having means for cooling the electron gun.

In electron beam generators such as electron beam processing machines and electron beam exposure machines, in order to make handling of the irradiated object safe and easy, the irradiated object and accelerating electrode are generally placed at ground potential, and the filament of the electron gun is It is common to configure the grid to be at a high negative potential. For this purpose, the structure that mechanically supports the filament and the grid needs to be an insulator that can withstand a high negative voltage corresponding to the accelerating voltage. In addition, the electron gun is 10-4 Tor.
Since it is operated in a high vacuum atmosphere of r or more, it must be airtight.

Further, since the filament is used after being heated to 2000 to 3000 qo, a means for cooling the heat emitted from the filament is required. In order to meet these demands, the conventional electron gun insulation structure was as shown in FIG.

That is, 1 is a filament (directly heated cathode), 2 is a grid, and 3 is an anode. An electron beam 12 generated by an electron gun including these elements is focused by an electromagnetic lens 13 and sent into the welding chamber 6. It is injected into the object 5 to be irradiated, is grounded at 15 through the side wall of the electron beam chamber 4, is also connected to the ground 15', passes through the beam ammeter 24, and is connected to the accelerating voltage source 23.
Reflux to. The electron beam chamber 4 is evacuated from the electron gun chamber outlet 41a to the welding chamber 6 to the required degree of vacuum from the electron gun chamber outlet 41b by a vacuum pump (not shown). A gun insulator is fixed to the ceiling of the electron beam chamber 4, and the filament 1
, the grid 2 is insulated and supported from the side wall of the electron beam chamber 4 which is at ground potential.

The electron gun insulator 9 is structured to receive a bias power source 21 and a filament power source 22, as well as a high voltage cable 11 for supplying power from an accelerating voltage source 23 to the grid 2 and filament 1, respectively. . The inside of the electron gun insulator 9, that is, the part into which the high voltage cable 11 is inserted, is filled with high voltage insulating oil 10. In addition to improving the withstand voltage, this insulating oil also removes heat generated from the filament from the high voltage cable 11.
This heat is received through the power supply line and carried to the water jacket 14 which is at ground potential. This heat can be cooled at ground potential by a cooling pipe 8 and a cooler 7 with a pump.Here, Regarding the shape of the grid 2, since only the opposing surfaces of the filament turtle and the accelerating electrode 3 contribute to the formation of the beam 12, it is not necessary to extend the grid to the insulator S as shown.

However, if it is shaped like the one shown in the figure, it will function as a so-called corona ring, and the non-uniformity of the potential distribution concentrated at the edge of the electron gun insulator can be eliminated.
Dotted line 31 shows the equipotential surface perpendicular to the lines of electric force in this case.
It will be as follows. However, such an electron gun insulated body has no problem in an electron beam generator with an output power of several kilowatts to several tens of kilowatts, but in an electron beam generator with an output power of nearly 10 dish watts, "the following There are three problems:
This was a factor that hindered the improvement of operating rates. The first is 100
In an electron beam generator with an output near KW, the shape of the filament is inevitably large, and the output range is from several KW to several tens of KW.
In this device, ``the filament heating power that used to be from several tens of W to several hundred W now requires mKW to several KW. In addition, in a method in which heat is transferred to the water jacket through electrostatic attraction and repulsion of oil particles by applying an accelerating voltage, ``the equilibrium point of heat input and output becomes high, and the electron gun insulation body 9, high voltage cable 1
The result was that the insulating oil 10 was forced to operate at high temperatures.The lifespan of insulators varies dramatically depending on the operating temperature, and it is even said that a rise in temperature of a few degrees can cut the lifespan in half. Therefore, the electron gun insulator 9 "Especially in the area near the filament, the insulation would become defective in a short period of time, and the time required to replace it would be wasted time, reducing the operating rate. The second problem is that The positive ions 32 that have entered the electron gun chamber are accelerated and attracted in a direction perpendicular to the equipotential surface 3, and collide with the electron gun insulator 9 at high speed.
It ionizes substances and adsorbed gases on its surface, causing local surface short circuits. This short circuit disturbs the potential distribution, which had been made uniform by the corona ring, and causes the remaining surface of the electron gun insulator 9 to become short-circuited. Since the short circuit causes the instantaneous accelerating voltage to drop and break the chain reaction, there was no problem because the short circuit caused the instantaneous acceleration voltage to drop. However, when the power source impedance is close to 10 W, the impedance of the power source is low and an instantaneous drop in the accelerating voltage cannot be obtained. The chain reaction continues until the allowable current is exceeded, at which point the protective device is activated.
The device seemed to stop. Once this chain reaction occurs, the area around the electron gun is filled with ions, and the surface of the electron gun insulator 9 becomes rough, so it takes several tens of seconds to several minutes to exhaust the ions and remove the electron gun insulator. It was necessary to age the surface of body 9. Third, due to deterioration of vacuum level, etc.
If a vacuum discharge occurs between the grid 2 and the anode 3 or the side wall of the electron gun chamber mother, a surge voltage will be generated inside the high voltage cable Fuki due to the mismatch between the impedance of the high voltage cable Katogame and the impedance of the electron gun. An unexpected abnormal voltage is generated where the traveling wave and the reflected wave overlap between the accelerating voltage source 23 and the accelerating voltage source 23, destroying the high voltage cable tatami and the accelerating voltage source 23. In a small electron beam generator, the surge wave reflected from the mismatched electron gun side releases power to the internal loss resistance of the accelerating voltage source 23, which is relatively well matched, and rapidly attenuates as it is repeatedly reflected. However, since high-output electron beam generators have low internal loss resistors, there is little attenuation due to repeated reflections, which increases the number of reflections and increases the probability of abnormal voltage generation. Therefore, there was a great risk of damage to the high voltage cable turtle 1 and the accelerating voltage source 23.This invention was designed to improve the three drawbacks of the conventional electron gun insulated body as described above. The heat generated from the hot cathode can be cooled by a cooler with forced circulation, and a voltage divider is installed perpendicular to the direction of the electric field of the insulator to equalize the voltage distribution. Even if a part of the insulator shorts due to impact, it prevents it from developing into a chain reaction.
Furthermore, it is intended to improve the mismatch between the electron gun and the high voltage cable 11 to suppress the occurrence of abnormal voltage.

FIG. 2 is a diagram showing an embodiment of the present invention.

The parts other than the vicinity of the electron gun insulator 9 are the same as those shown in FIG. 1, so the explanation will be omitted. 7 is a cooler with a pump, which supplies high-pressure insulating oil 10 as a cooling medium to an inlet 52, an oil flow passage 54, an electron gun insulator bottom 55, and a high-pressure insulating oil outlet 53.
circulate through the route. This cooling system provides support for the filament 1 in the electron gun insulator bottom 55 and
This means that the voltage distribution uniformity resistor 59, which will be described later, is actively cooled. Referring to FIG. 3, which is a detailed view of the electron gun insulator bottom 55, 58 is an oil passage for the insulating oil 10, which is connected to the oil passage 54 of the electron gun insulator 9, and is connected to the oil passage 54 of the electron gun insulator 9. It has a shape that penetrates the inside of the support body 57.

In such a configuration, the amount of oil that comes into contact with the filament support 57 whose temperature is rising due to the heat from the filament 1 and contributes to heat exchange is "significantly increased compared to the conventional natural convection type. , it was possible to lower the temperature of the support 57 from 100 to 1500 C in the past to 50 to 7000 C. Referring again to FIG. A wire resistor connects the positive terminal of the electron gun to the vicinity of the ground potential, and is arranged in double spirals in a clockwise direction and a counterclockwise direction along the side wall of the electron gun insulator 9.

As described above, the gaps between adjacent filaments of the resistor in the spiral arrangement are used as the oil passages 54 for the cooling insulating oil 10.
A lead wire 61 connects the filament support 57 and the lower end of the resistor.
The beam ammeter 24 and the upper end of the resistor 59 are connected by a lead wire 60. Since this lead wire 60 is connected to the acceleration voltage source 23 side of the beam ammeter 24, the current flowing through the resistor 59 does not pass through the beam ammeter 24. Therefore, there is no error in the beam current meter 24. The resistance value of the resistor 59 is selected so that the heat generated by the current flowing therein can be sufficiently ignored compared to the heat generated by the filament, and the cooling insulating oil 101 is also placed in contact with the resistor 59 so that the heat generated by the resistor 59 is suppressed. Care has been taken to prevent the temperature of the electron gun insulator 9 from rising and adversely affecting its life.
Due to the presence of this resistor 59, the equipotential surface 31 (Fig. 1), which had been in the form of electrostatic division, becomes - in the form of resistance division, and the positive ions 32 collide with the electron gun insulator 9, and the surface Even if a short circuit occurs locally, the potential gradient is determined by resistance division and is extremely stable, so the voltage shared by the resistor corresponding to the short circuit is equally shared by the remaining resistors as an additional voltage. . As a result, a local short circuit no longer causes a chain reaction that develops into a complete short circuit as in the past. Also, the electron gun end of the high voltage cable 11,
Since the cable is terminated with a resistor 59, mismatching between the high voltage cable 11 and the electron gun can be improved. As shown in FIG. 4, the resistor 59 is arranged in a spiral shape with one side clockwise and the other counterclockwise to cancel out the inductance and prevent an increase in surge impedance due to the inductance. There is.

As a result, even if a vacuum discharge occurs between the grid 2 and the anode 3 or the electron gun chamber 4 and a surge voltage occurs, the mismatch between the electron gun and the high voltage cable 11 has been improved, so the electron gun and the acceleration There is little reflection of surge waves between the voltage sources 23, and even if there is reflection, each time the reflection is repeated, power is released to the resistor 59 and rapidly attenuates, generating abnormal voltage in the high voltage cable 11 and accelerating voltage source 23. The probability of doing so is lower. As a result, accidents involving the high voltage cable 11 and accelerating voltage source 23 have been significantly reduced. In summary, by using the present invention, the reliability of the electron gun insulator 9, the high voltage cable 11, and the accelerating voltage source 23 can be improved, and the operating rate can be reduced due to the short circuit phenomenon that occurs on the surface of the electron gun insulator 9. We were able to improve the decline.

In addition, when replacing the filament 1, etc., the electron gun insulator 9
If the electron gun insulator 9 is exposed to the atmosphere, the temperature of the electron gun insulator 9 is increased by stopping the operation of the cooler 56 with circulation means during re-high-pressure aging immediately after that, and the gas adsorbed on the surface is released. could be done easily. Therefore, the present invention greatly contributes to improving the operating rate of high-power electron beam generators and is of high industrial value.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional electron gun insulating foundation body, FIG. 2 is a sectional view showing the structure of an electron gun insulating body of the present invention, and FIG. 3 is a perspective sectional view of the bottom of the electron gun insulator. , FIG. 4 is a diagram illustrating a method of arranging resistors. In the figure, 1 is a filament, 2 is a grid, 3 is an anode, 4 is an electron beam chamber, 5 is an object to be irradiated, 6 is a welding chamber, 7 is a cooler with a pump, 8 is a cooling pipe, and 9 is a cylindrical insulator. , 10 is a high-voltage insulating oil, 11 is a high-voltage cable, 23 is a high-voltage power supply, 31 is an equipotential line, 52 is an insulating oil inlet, 53
54 is an insulating oil discharge port, 54 is an insulating oil circulation passage, 55 is a bottom of a cylindrical insulator, 56 is a grid support, 57 is a filament support, 58 is a bottom oil passage, and 59 is a resistor arranged in a spiral configuration. Tsutomu's figure 2, traditional figure 3, younger brother figure 4

Claims (1)

[Claims] 1 A cylindrical insulator with a bottom has a grid and filament support provided at the bottom, a high-voltage cable connected to this support is introduced into the cylindrical body, and the inside is filled with high-voltage insulating oil. In the electron gun insulating structure which insulates the support body from the side wall of the electron beam chamber at a high voltage, two resistors are provided inside the cylindrical side wall to spirally surround the cylindrical internal wall in opposite directions. , the upper end of this resistor is connected to the ground potential of the side wall of the electron beam chamber, the lower end is connected to the filament support, and a high voltage is applied to the passage formed by the space between adjacent helical resistors. An electron gun insulating structure characterized by comprising means for circulating insulating oil.