JPS628560Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an electron beam irradiation device, and particularly to improvements in its scanning power source.

FIG. 1 schematically shows the main parts of a general electron beam irradiation device, in which 1 is an electron gun made of a filament, 2 is an acceleration tube that accelerates the electron beam generated from the electron gun 1, and 3 is an electron beam irradiation device. 4 is a scanning tube, 4 is an irradiation window that closes the end of the scanning tube 3 with a thin metal foil such as titanium, and 5 is a scanning coil.

In this electron beam irradiation device, the electron gun 1, acceleration tube 2, scanning tube 3, and irradiation window 4 are arranged in a straight line, and when performing electron beam irradiation, the scanning coil 5 is driven. As a result, unless the electron beam is scanned over the irradiation window 4, the electron beam passes through the center of the irradiation window 4 in the form of a spot. However, the amount of electron beam that can be passed through the irradiation window 4 without any problem is normally limited to about 0.2 mA/cm ² , and if this limit is exceeded, the irradiation window 4 will be instantly destroyed due to excessive heat generation. . Therefore, when irradiating an electron beam, the scanning coil 5 is normally driven by the output of the scanning power supply device 10, as shown in FIG. In the figure, 11 is a scanning waveform oscillator with a scanning waveform output of 200Hz, 12 is an amplifier, and 6
is an isolation transformer provided as necessary.

However, as the fields of application of electron beam irradiation devices have expanded in recent years, their output capacity has increased, which inevitably requires an increase in the output of the scanning power supply device 10, promoting larger size. Ru. For this reason, the number of components of the scanning waveform oscillator 11 increases, the circuit configuration becomes complicated, and failures are more likely to occur. Then, the load on the amplifier 12 that supplies a large current to the scanning coil 5, which is mostly due to inductance, becomes heavy, and failures due to heat generation are more likely to occur. Therefore, these result scanning power supplies 10:
As the size of the electron beam irradiation device increases, it becomes more prone to breakdowns, resulting in an abnormality in its output and the inability to drive the scanning coil 5.

Generally, if the scanning power supply 10 fails, the protection device will stop the power supply to the filament, but the emission of electrons will not immediately stop due to the filament's thermal time constant. Therefore, if the scanning power supply device 10 malfunctions and its output becomes abnormal, the unscanned electron beam will locally concentrate and hit the irradiation window 4, leading to the irradiation window 4 being destroyed by overheating. This destruction of the irradiation window 4 induces secondary destruction of the electron irradiation device, such as breakage of the filament and contamination of the acceleration tube 2.

This invention was proposed with the above-mentioned considerations in mind, and when the output of the scanning power supply device 10 becomes zero due to an abnormality from normal operation, for example, an internal failure of the scanning waveform oscillator 11 or the amplifier 12, To provide an electron beam irradiation device that prevents the scanning function of a scanning coil 5 from stopping in a short time until electron emission from a filament stops and allows continuous scanning of an electron beam on an irradiation window. With the goal.

This invention will be explained in detail based on an embodiment shown in FIG. In the figure, the same reference numerals as in FIG. 2 indicate the same parts. Reference numeral 20 denotes an auxiliary scanning power supply device provided separately from the scanning power supply device 10;
40 is a switching device, 40 is an output monitoring device, 50 is a detection resistor, and 7 is an isolation transformer provided as necessary.

A switch 30 is provided on the input side of the scanning coil 5, and a scanning power supply device 10 and an auxiliary scanning power supply device 20 are connected to terminals 31 and 32, respectively. During normal operation, the scanning coil 5 is driven by the output of the scanning power supply device 10. The output monitoring device 40 monitors the output of the scanning power supply device 10 using a detection resistor 50, and when the output falls below a predetermined value,
A switching command is given to the switching device 30. The switch 30 switches the power supply connection in response to a switching command from the output monitoring device 40.

The auxiliary scanning power supply device 20 may be of any type as long as it prevents the scanning function of the scanning coil 5 from stopping when the output of the scanning power supply device 10 is abnormal. Therefore, it is inappropriate for the output to be direct current, and it is appropriate to have an output that changes in alternating current. The scanning coil 5 is driven by the auxiliary scanning power supply 20 for a short time until electrons are no longer emitted from the filament, so the auxiliary scanning power supply 20 may have a small capacity and a small output. Further, since most of the scanning coil 5 is inductance, the lower the frequency, the smaller the impedance, and the load on the auxiliary scanning power supply 20 is reduced.
A lower frequency is preferable. For example, when a commercial frequency AC power source is used, the configuration of the auxiliary scanning power supply device 20 becomes extremely simple and inexpensive.

In this device, an output monitoring device 40 monitors the output of the scanning power supply 10, and when the output reaches a predetermined value, for example, zero, it gives a command to the switch 32 to change the output of the auxiliary scanning power supply 20. scanning coil 5
is configured to be supplied to Therefore, when the scanning power supply 10 loses its output due to an internal failure, the scanning coil 5 is switched to the auxiliary scanning power supply 2 even if the filament continues to emit electrons.
It is driven by an output of 0, and can continuously scan the electron beam on the irradiation window. As a result, it is possible to prevent the electron beam from locally concentrating on the irradiation window 4 and prevent the irradiation window 4 from being thermally destroyed. Therefore, secondary destruction of the electron beam irradiation device due to destruction of the irradiation window 4 can be prevented. In this invention, since the switch 30 is provided on the input side of the scanning coil 5, that is, immediately before the scanning coil 5,
The auxiliary scanning power supply device 20 can be used in response to all failures on the scanning power supply side and even power outages, allowing for more reliable operation.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram showing the main parts of a general electron beam irradiation device, Figure 2 is a block diagram showing the relationship between a conventional scanning coil and a scanning power supply, and Figure 3 is a diagram showing the scanning coil and the scanning power supply device according to this invention. FIG. 2 is a block diagram showing the connection relationship between a scanning power supply device and a scanning auxiliary power supply device. 4...Irradiation window, 5...Scanning coil, 10...Scanning power supply device, 11...Scanning waveform oscillator, 20...
Auxiliary scanning power supply device, 30...switcher.

Claims (1)

[Claims for Utility Model Registration] 1. A scanning power supply device including a scanning waveform oscillator and an auxiliary scanning power supply device whose output changes in an alternating current manner are connected to the input side of the scanning coil via a switch, and the scanning power supply device An output monitoring device for monitoring the output of the device is provided, and when the output monitoring device detects that the output of the scanning power supply device falls below a predetermined value, a switching command is given to the switching device to switch the output of the auxiliary scanning power supply device to the scanning coil. An electron beam irradiation device characterized by supplying. 2. The electron beam irradiation device according to claim 1, wherein the output frequency of the auxiliary scanning power supply device is lower than the frequency of the scanning waveform oscillator. 3. The electron beam irradiation apparatus according to claim 1, wherein the auxiliary scanning power supply device is a commercial frequency AC power supply.