JPH07302567A - Electron beam irradiating device - Google Patents

Abstract

PURPOSE:To take out the electron beam of a large electric current from an irradiating window without losing the electron beam, and enhance a window foil cooling effect even when the electron beam of a large electric current is taken out. CONSTITUTION:An irradiating window 4 whose width is not more than 200mm and which is opened in a sawtooth shape is formed in a lower part of a scanning tube 1. This irradiating window is blocked up by window foil 5 composed of titanium or titanium alloy. An electron beam is scanned in a sawtooth shape along this irradiating window. Thereby, the distance to pass the electron beam can be lengthened, and the loss of the electron beam is reduced. Since the width of the irradiating window is narrow, the window foil can be efficiently cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam irradiation device.

[0002]

2. Description of the Related Art As is well known, an electron beam irradiation apparatus is constructed so that an electron beam accelerated by an accelerating tube is taken out from an irradiation window provided under the accelerating tube to irradiate an irradiation object. There is. The scanning of the electron beam is performed by a triangular coil current as a scanning current in a scanning coil installed above the scanning tube.

FIG. 12 shows the structure, 1 is a scanning tube, and 2 is a scanning tube.
Is a scan coil, 3 is a scan controller for supplying a scan current to the scan coil 2, and 4 is an irradiation window. FIG. 4 shows the structure of the conventional irradiation window 4. The irradiation window 4 has a thickness of 10 to 100
It is closed by a window foil 5 made of titanium or titanium alloy having a thickness of μm, and the periphery thereof is sandwiched by a lower flange 6 of the scanning tube 1 and a window holding flange 7. A metal seal 8 seals between the lower flange 6 and the window foil 5.

Since the window foil 5 generates heat by passing an electron beam,
In order to cool this, a cooling air duct 9 is installed on one side surface of the irradiation window 4, and cooling gas or compressed air (hereinafter simply referred to as cooling gas) sent from the blower 10 is supplied from the cooling air duct 9. The window foil 5 is blown onto the atmosphere side as indicated by the arrow. Reference numeral 11 denotes a nozzle (or slit; the same applies hereinafter) for blowing a cooling gas.

Scanning of the irradiation window 4 with the electron beam by the scanning coil 2 is performed by passing a triangular wave current through the scanning coil 2, whereby the electron beam is moved in the lengthwise direction of the irradiation window 4 as shown in FIG. Along the line, a linearly reciprocating locus is drawn, or a triangular wave-shaped locus is drawn as shown in FIG. E shows the locus.

By the way, the window foil 5 installed on the irradiation window 4
Is the pressure difference between the high vacuum inside the scan tube 1 and the atmosphere (1
It is necessary to withstand about 1 kg per square cm). Therefore, in the configuration shown in FIG. 4, the width (length in the direction orthogonal to the scanning direction) W of the irradiation window 4 is limited to about 180 mm at the maximum. On the other hand, when a large current of the electron beam is required, it is necessary to increase the area of the irradiation window 4. However, when the width W of the irradiation window 4 is limited, the length L of the irradiation window 4 (the length along the scanning direction) may be increased, but this is economically limited to 4000 to 5000 mm.

When the width of the irradiation window 4 is limited as described above and an irradiation window having a large area is required for increasing the current, the irradiation window as shown in FIGS. May be used. In each of these, the irradiation window is divided into two along the width direction, and a reinforcing bar 12 extending in the scanning direction is provided at the center of the irradiation window.
The window foil 5 provided at the center is supported.

With such a structure, the reinforcing bars 12 mechanically support the center of the window foil 5, so that the irradiation windows become the two irradiation windows 4A and 4B divided by the reinforcing bars 12. The width of each irradiation window 4A, 4B is 90
Even with ~ 200 mm, the window foil 5 will be able to withstand the pressure difference between the high vacuum inside the scanning tube 1 and the atmosphere. The width of the irradiation window can be doubled as compared with the configuration shown in FIG. 4, and the area can be enlarged.

When two irradiation windows are provided in this manner, as shown in FIG.
0 or as shown in FIG. 11, the electron beam is scanned in one irradiation window along the length direction thereof, then moves to the other irradiation window, and is subsequently scanned in the length direction.
It should be noted that, so as not to scan the same portion on the window foil, a square wave current is applied to the scanning coil so as to change it in a plurality of channels as shown in FIG. 10, or as shown in FIG. As depicted, the electron beam density in the width direction of the irradiation window is flattened.

When the electron beam moves between the irradiation windows 4A and 4B as described above, the reinforcing crosspiece 12 between the irradiation windows is irradiated with the electron beam and generates heat, so that it is necessary to attach the water cooling pipe 13. is there. Further, from the atmosphere side, a water cooling bar 14 may be provided to prevent heat generation in the central portion of the window foil due to backscattering of the electron beam from the object to be irradiated.

In order to cool the window foil 5, cooling air ducts 9 are provided on both sides of the irradiation window 4 in FIG. 7, so that cooling gas is blown from both sides toward the center. However, in this case, turbulence of the air flow occurs in the central portion, and when the irradiation target is a web, it may vibrate.
In order to avoid this, as shown in FIG.
Is provided in the central portion, or as shown in FIG.
The cooling air duct 9 is provided only on one side of the.

However, in the structure in which the irradiation windows are doubled as described above, when the electron beam is transferred from one irradiation window to the other irradiation window, electrons are captured by the reinforcing bar 12 provided in the central portion. , The electron beam is lost by that amount. Specifically, the capture of electrons by the reinforcing bar 12 causes the electron beam to
Lost about 3%.

When the window foil 5 is cooled by blowing a cooling gas, the cooling effect is reduced as the window foil portion is located farther from the nozzle. To be more specific, 100m
In the case of electron beam A, 1 on the window foil of the irradiation window with a width of 200 mm
Compressed air, which is a cooling gas of 0.2 kg per square cm,
When sprayed along the width direction, several c from the nozzle
The temperature of the window foil was 250 ° C at a distance of m, but the temperature of the window foil was 350 ° C at a distance of 15 cm from the nozzle.
Became.

Window foils usually made of titanium or titanium alloys withstand use up to 350 ° C. Therefore, even if it can be used for an electron beam of about 100 mA, it will exceed the allowable temperature of the window foil at a position far away from the nozzle for an electron beam larger than this. Therefore, as shown in FIG. 9, the configuration in which the cooling gas is blown from only one side of the irradiation window cannot be used for a large current. In order to avoid this, it is necessary to strengthen the cooling of the far place.

[0015]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce electron beam loss by realizing extraction of a large current electron beam without forming a double irradiation window. Another object of the present invention is to enhance the cooling effect of the window foil even when a high-current electron beam is taken out.

[0016]

According to the present invention, an irradiation window having a sawtooth shape with a width of 200 mm or less is formed in a lower portion of a scanning tube, and the irradiation window is closed by a window foil made of titanium or titanium alloy. It is characterized in that the electron beam is scanned in a sawtooth shape along the irradiation window.

Further, the present invention is characterized in that a nozzle for blowing a cooling gas is provided in the vicinity of a side edge along the length direction of the irradiation window opening in a sawtooth shape.

[0018]

Since the width of the irradiation window is 200 mm or less, it is possible to sufficiently withstand the pressure difference between the inside of the scanning tube and the atmosphere. Since the reinforcing bar does not exist in the width direction of the irradiation window, even if the electron beam scans the irradiation window in a sawtooth shape, the reinforcing bar does not cause the loss of the electron beam. Then, since the electron beam is scanned in a sawtooth shape, the scanning locus becomes equivalently long, for example, 500
Irradiation with a large current of about mA to 1 A can be realized.

Even when irradiating a high-current electron beam in this way, since the nozzle for blowing the cooling gas is provided in the vicinity of the side edge of the irradiation window, the window foil far away from the nozzle is also sufficient. Can be cooled to.

When the electron beam is scanned in a sawtooth shape, the scanning current supplied to the scanning coil is scanned in the width direction at a frequency which is at least several times to several tens of times faster than the scanning frequency in the length direction of the irradiation window. It can be realized by

[0021]

Embodiments of the present invention will be described with reference to FIGS. Note that the portions denoted by the same reference numerals as those in each of the drawings after FIG. 4 indicate the same or corresponding portions. According to the present invention, the irradiation window 4 provided in the lower portion of the scanning tube 1 is formed in a sawtooth shape. As a specific configuration therefor, a crosspiece 21 having a serrated tip is provided on one side surface of the scanning tube 1, and a crosspiece 22 having a serrated tip is also provided on the other side surface of the scanning tube 1. Install facing each other.

Then, the troughs and peaks of the crosspiece 21 are made to face each other with respect to the peaks and troughs of the crosspiece 22.
The sawtooth-shaped irradiation window 4 is formed between the tips of the crosspieces 21 and 22. The width W1 of the sawtooth irradiation window 4 thus formed is 200 mm or less, preferably 1
20 to 180 mm. The window foil 5 is installed along the lower surface of each crosspiece 21, 22. Since the width of the irradiation window 4 is 180 cm or less, it is possible to use the reinforcing bar 12 unlike the conventional one.
The window foil 5 can be installed.

A duct 9 is provided on one outer side of the scanning tube 1,
The cooling gas supplied from here is sprayed onto the window foil 5 from the vicinity of the side edge of the irradiation window 4 by a nozzle. Specifically, Fig. 2
As shown in FIG. 1, one side edge A of the irradiation window 4 having a serrated shape is formed.
The nozzle may be arranged along the line.

In this way, at the location where the side edge A and one side surface of the scanning tube 1 coincide with each other, as shown in FIG.
A cooling gas is blown onto the window foil 5 from the nozzle 11 on the lower surface of the flange 7 along the width direction thereof. Further, as shown in FIG. 3, when the crosspiece 22 is provided on the same one side surface of the scanning tube 1 and the side edge A projects to the center of the scanning tube 1, the nozzle extended to the lower surface of the crosspiece 22. A cooling gas is blown from 11A onto the window foil 5 along the widthwise direction as well.

The electron beam is scanned by the scanning coil 2 in a sawtooth shape as shown by the locus E in FIG. In this case, scanning is performed so that the side edges of the irradiation window 4 having a saw-tooth shape are not traversed outside. Since there is no conventional reinforcing bar 12 inside the irradiation window 4, there is no loss of the electron beam due to collision with the reinforcing bar during the scanning of the electron beam.

Since the electron beam is scanned in a sawtooth shape,
The path through which the electron beam passes can be made almost as long as in the case of FIGS.
An electron beam with a large current of about 0 mA to 1 A can be taken out to the outside.

On the other hand, a cooling gas is blown onto the window foil 5 from the nozzles 11 and 11A. However, since the width W1 of the irradiation window 4 is 200 mm or less, it can be sufficiently cooled to 350 ° C. or less by this cooling gas even at a place far from the nozzle. Therefore, even when a high-current electron beam is transmitted, the window foil 5 can be cooled within the temperature allowable range.

[0028]

As described above, according to the present invention, it is possible to lengthen the path through which an electron beam passes without widening the width of the irradiation window, and thus without providing a reinforcing bar, which results in a large current. The electron beam can be taken out and the window foil of the irradiation window can be sufficiently cooled.

[Brief description of drawings]

FIG. 1 is a plan view of an irradiation window showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line aa in FIG. 1, showing an embodiment of the present invention.

FIG. 3 is a sectional view taken along line bb of FIG.

FIG. 4 is a sectional view of a conventional example.

FIG. 5 is a plan view showing a scanning locus of an electron beam in an irradiation window of a conventional example.

FIG. 6 is a plan view showing a scanning locus of an electron beam in an irradiation window of another conventional example.

FIG. 7 is a cross-sectional view of another conventional example.

FIG. 8 is a cross-sectional view of still another conventional example.

FIG. 9 is a sectional view of still another conventional example.

FIG. 10 is a plan view showing a scanning locus of an electron beam in an irradiation window of still another conventional example.

FIG. 11 is a plan view showing a scanning locus of an electron beam in an irradiation window of still another conventional example.

FIG. 12 is a front view showing the entire electron beam irradiation apparatus.

[Explanation of symbols]

 1 Scan Tube 2 Scan Coil 4 Irradiation Window 5 Window Foil 11 Nozzle (or Slit) 11A Nozzle (or Slit) 21 Crosspiece 22 Crosspiece A Side Edge

Claims (2)

[Claims] 1. An irradiation window having a sawtooth shape with a width of 200 mm or less is formed in the lower part of the scanning tube, and the irradiation window is closed with a window foil made of titanium or titanium alloy, and along the irradiation window. An electron beam irradiation device that scans an electron beam in a sawtooth shape. 2. The nozzle or slit for blowing a cooling gas for cooling the window foil is provided in the vicinity of a side edge along the length direction of the irradiation window which is opened in a saw-tooth shape. Electron beam irradiation device.