JPWO2011102320A1 - Electron beam irradiation apparatus and electron beam irradiation method - Google Patents

Abstract

An electron beam irradiation apparatus and an electron beam irradiation method capable of monitoring an electron beam irradiation position and stopping an electron beam output when the electron beam deviates from an irradiation object. When the wavelength of the characteristic X-ray emitted from the element that is the main component of the irradiation object 60 by the electron beam irradiation is called a first wavelength, the area other than the surface area of the irradiation object 60 among the areas that can be irradiated with the electron beam. An outer member that emits characteristic X-rays having a second wavelength different from the first wavelength is disposed in at least a part of the region. During the irradiation of the electron beam, the intensity of the X-ray having a specific wavelength among the X-rays emitted from the irradiation object 60 and the outer member is detected, and when an abnormality is found from the detection result, the electron beam is stopped.

Description

  The present invention relates to an electron beam irradiation apparatus and an electron beam irradiation method.

Currently, high-power electron beam application equipment that can irradiate an object with relatively high energy of about 10 kW to 300 kW to dissolve, evaporate, sublimate, etc. is mainly used for vacuum deposition and vacuum dissolution purification. It is used.
These apparatuses have a relatively large vacuum chamber having a volume of 1 m ³ or more, an evacuation system, an electron gun, and a container (water-cooled hearth) for holding a metal to be dissolved. The container is usually made of copper with good thermal conductivity. The target metal in vacuum melting and refining is an active metal such as titanium, a vacuum material such as stainless steel, and a high melting point metal such as molybdenum and tantalum, and the target metal in vacuum deposition is aluminum, titanium, copper or the like. Recently, vacuum melting purification of silicon has also been performed for solar cells. In a vacuum evacuated vacuum chamber, these materials are irradiated with an electron beam to perform refining and vapor deposition.
In the process of irradiating an irradiation object with an electron beam, if the electron beam deviates from the normal trajectory, deviates from the irradiation object, and hits a device component other than the irradiation object, the part may be melted and damaged. there were. For example, when an electron beam hits the container, a hole is formed, causing water leakage, which may cause not only stop of the previous process and damage of the hearth but also a serious disaster such as a steam explosion in the worst case. When an electron beam hits the tank wall of the vacuum chamber, a hole is opened instantly and a large leak occurs. When the atmosphere leaks into the vacuum, electron gun parts such as filaments and cathodes in a high temperature state are damaged.

In order to prevent these accidents from occurring, it is always monitored on-time that the electron beam is being applied to the irradiation object, and if the electron beam deviates from the irradiation object, the electron beam irradiation is immediately stopped. However, it is necessary to prevent melting and breakage of apparatus constituent members such as containers and vacuum chambers.
The monitoring method usually considered uses visible light, but when the irradiation electron beam becomes high power of 40 kW or more, it emits intensely in a wide range of the position where the electron beam hits, so the irradiation position cannot be confirmed with visible light. There was a problem.

At present, since there is no specific method for monitoring the irradiation position of the electron beam on time, the following two indirect methods are the main methods for detecting the abnormality of the electron beam.
(1) Detect an abnormality in the control system (for example, current abnormality).
(2) Detecting an abnormal pressure in the vacuum vessel (rapid increase in pressure).
However, in the method of detecting an abnormality in the control system of (1), for example, even if it is displayed that the current of the lens or the line deflection coil becomes zero, if there is a problem in the display part of the control system, the electron beam There is a problem that the electron beam output is stopped although the irradiation position is normal. Further, there has been a problem that the deviation of the irradiation position due to the deviation of the position of the cathode inside the casing of the electron gun or the inclination of the casing itself cannot be detected even if the control system is monitored.
In addition, in the method of detecting the pressure abnormality in (2), the cause of the pressure increase is that a breakage has already occurred such as a hole in the container or a hole in the vacuum chamber. There was a problem that damage could not be prevented in advance even though the spread of

JP-A-11-310871 JP-A-5-306456

  The present invention was created to solve the disadvantages of the prior art described above, and its purpose is to monitor the irradiation position of the electron beam and to stop the electron beam output when the electron beam deviates from the irradiation object. An object of the present invention is to provide an electron beam irradiation apparatus and an electron beam irradiation method.

  The present inventors pay attention to the fact that a substance irradiated with an electron beam emits characteristic X-rays unique to the element contained in the substance. X-rays can be detected separately from visible light, and the wavelength of X-rays can be determined. It was found that by analyzing and identifying the element, the position of the member containing the element can be specified, and the irradiation position of the electron beam can be determined. Furthermore, by selecting a specific material, it is possible to make an X-ray cutoff filter that attenuates X-rays of a specific wavelength more than X-rays of other wavelengths. By using it in combination with a line detector, it was discovered that elements could be identified at low cost and at high speed, and the present invention was completed.

In order to solve the above problems, the present invention has a vacuum chamber, a vacuum exhaust device that evacuates the vacuum chamber, and an electron gun configured to emit an electron beam into the vacuum chamber, The irradiation object arranged in the vacuum chamber is configured to irradiate the irradiation object by irradiating the electron beam from the electron gun, and the irradiation object is more than 90 mol% by irradiation with the electron beam. When the wavelength of the characteristic X-rays emitted from the first element contained in a large amount is the first wavelength, at least a part of the region other than the surface region of the irradiation object among the regions that can be irradiated with the electron beam. Is an electron beam irradiation apparatus in which an outer member that emits characteristic X-rays having a second wavelength different from the first wavelength by irradiation of the electron beam is disposed, and the irradiation object and the outer member are The emitted X-ray enters and the incident X-ray It detects the intensity of X-rays Chi specific wavelength discovers an abnormality detection result, an electron beam irradiation device having, an abnormality detection device for stopping the electron beam.
This invention is an electron beam irradiation apparatus, Comprising: The said outer member contains the 2nd element which discharge | releases the characteristic X-ray of said 2nd wavelength by irradiation of the said electron beam more than said 1st element. It is a line irradiation device.
This invention is an electron beam irradiation apparatus, Comprising: The said outer member is an electron beam irradiation apparatus which is any one or both of the tank wall of the said vacuum chamber, and the container holding the said irradiation target object.
The present invention is an electron beam irradiation apparatus, wherein the abnormality detection apparatus has a greater attenuation rate of the X-ray intensity of the first wavelength than the attenuation rate of the X-ray intensity of the second wavelength. A blocking filter; an X-ray detection device that detects the intensity of X-rays that have passed through the blocking filter; and the X-ray intensity detected by the X-ray detection device is increased above a predetermined threshold value. An electron beam irradiation device having a control device to be stopped.
The present invention is the electron beam irradiation apparatus in which the first element is silicon, and the blocking filter is an electron beam irradiation apparatus containing one or both of aluminum and magnesium.
The present invention is an electron beam irradiation apparatus, wherein the abnormality detection device has an X-ray intensity attenuation rate of the first wavelength smaller than an X-ray intensity attenuation rate of the second wavelength. A blocking filter; an X-ray detection device that detects the intensity of X-rays that have passed through the blocking filter; and the X-ray intensity detected by the X-ray detection device decreases below a predetermined threshold value. An electron beam irradiation device having a control device to be stopped.
This invention is an electron beam irradiation apparatus, Comprising: The said abnormality detection apparatus detects the intensity | strength of the X-ray of a specific wavelength among the incident X-rays, and the specific wavelength which the said X-ray detection apparatus detected A control device for stopping the electron beam when the intensity of the X-ray is different from the intensity of the X-ray having a specific wavelength when the irradiation object is irradiated with the electron beam. Device.
The present invention is an electron beam irradiation apparatus, comprising: a magnetic field forming means for forming a magnetic field in the trajectory of the electron beam; and an inside of a surface region of the irradiation object where the irradiation position of the electron beam is exposed in the vacuum chamber. It is an electron beam irradiation apparatus which has a magnetic field control apparatus which controls the direction and magnitude | size of the said magnetic field by the said magnetic field formation means so that it may move.
In the present invention, when the wavelength of the characteristic X-ray emitted from the first element contained in the irradiation object by more than 90 mol% by the irradiation of the electron beam is a first wavelength, the region that can be irradiated with the electron beam. An outer member that is disposed in at least a part of a region other than the surface region of the irradiation object and emits characteristic X-rays having a second wavelength different from the first wavelength by irradiation with the electron beam. An electron beam irradiation method of irradiating the irradiation object disposed in the vacuum chamber with an electron beam while heating the irradiation object while evacuating the vacuum chamber, the irradiation of the electron beam In the X-ray emitted from the irradiation object and the outer member, the X-ray intensity of a specific wavelength is detected, and when an abnormality is detected from the detection result, the electron beam irradiation method stops the electron beam. is there.
This invention is an electron beam irradiation method, Comprising: The said outer member contains the 2nd element which discharge | releases the characteristic X-ray of said 2nd wavelength by irradiation of the said electron beam more than said 1st element. It is a line irradiation method.
This invention is an electron beam irradiation method, Comprising: The said outer side member is an electron beam irradiation method which is either the tank wall of the said vacuum chamber, and the container holding the said irradiation target object, or both.
The present invention is an electron beam irradiation method using a cutoff filter having a greater attenuation rate of the X-ray intensity of the first wavelength than the attenuation rate of the X-ray intensity of the second wavelength, An X-ray intensity threshold value is determined in advance, and during irradiation of the electron beam, the intensity of X-rays emitted from the irradiation object and the outer member and transmitted through the blocking filter is detected and detected. This is an electron beam irradiation method for stopping the electron beam when the intensity of the X-rays increased above a predetermined threshold value.
The present invention is an electron beam irradiation method in which the first element is silicon, and the blocking filter is an electron beam irradiation method containing one or both of aluminum and magnesium.
The present invention is an electron beam irradiation method using a cutoff filter in which the attenuation rate of the X-ray intensity of the first wavelength is smaller than the attenuation rate of the X-ray intensity of the second wavelength, An X-ray intensity threshold value is determined in advance, and during irradiation of the electron beam, the intensity of X-rays emitted from the irradiation object and the outer member and transmitted through the blocking filter is detected and detected. This is an electron beam irradiation method for stopping the electron beam when the intensity of the X-ray is reduced below a predetermined threshold value.
This invention is an electron beam irradiation method, Comprising: The intensity | strength of the X-ray of a specific wavelength is detected among the X-rays emitted from the said irradiation object and the said outer member during the said electron beam irradiation, and the detected specific In the electron beam irradiation method, the electron beam is stopped when the intensity of the X-ray with the wavelength is different from the intensity of the X-ray with the specific wavelength when the irradiation target is irradiated with the electron beam.
The present invention is an electron beam irradiation method, wherein the irradiation target is moved while moving the irradiation position of the electron beam inside a surface region of the irradiation object exposed in the vacuum chamber during the electron beam irradiation. This is an electron beam irradiation method for heating an object.

An X-ray emission phenomenon from a material irradiated with an electron beam will be described.
When a material is irradiated with an electron beam, braking X-rays (also called white X-rays) having continuous energy in substantially the same range as the energy of the irradiated electron beam and characteristic X-rays specific to the elements contained in the material are generated.
Characteristic X-rays are orders of magnitude stronger than white X-rays. In general, X-ray detection targets these characteristic X-rays. In the present invention, an X-ray detector is selected for characteristic X-rays. ing.

Characteristic X-rays mainly have two types of energy.
They are called Kα ray and Kβ ray from the lower energy. Further, the Kα line and the Kβ line have larger energy as the atomic number is larger. Therefore, the original element can be identified with high sensitivity by knowing the energy (or wavelength) of the Kα ray and Kβ ray. This principle is used in elemental analyzers. Kα rays and Kβ rays indicate X-rays generated when the K-shell electrons in the atomic orbitals of the elements are excited and knocked out.
With heavy elements, the energy required to excite K-shell electrons increases, and when the energy of the irradiated electron beam is exceeded, K-shell electrons cannot be knocked out. In that case, electrons in the L shell, which is an electron orbit outside the K shell, are excited and knocked out. The characteristic X-rays generated in this case are called Lα rays and Lβ rays.

  When X-rays are absorbed by a material, they are strongly absorbed at a specific energy determined by the element of the material. This energy position is called the absorption edge. The energy at the absorption edge of a certain element is higher than the characteristic X-ray energy generated from the same element, and is therefore difficult to be absorbed by the element itself. However, it is strongly absorbed by elements with atomic numbers 1 to 2 smaller.

During irradiation of a high-power electron beam of 10 kW or more, it becomes possible to detect on-time the electron beam irradiation to a place other than the irradiation target and perform an emergency stop of the electron beam.
As a result, even if a trouble occurs when a high-power electron beam hits a structural member other than the object to be irradiated, the electron beam dissolves and destroys the structural member, and in some cases prevents a personal injury from occurring. Costs and significant loss of production resources due to human disasters can be eliminated, and extremely safe operation can be performed.
If an X-ray detector having no spectroscopic function is used, the present invention can be attached to all devices using a high-power electron beam at a low cost. For example, it can be used for a high-speed continuous winding vapor deposition apparatus, a refractory metal dissolution and purification apparatus, an active metal dissolution and purification apparatus, and a silicon dissolution and purification apparatus for producing high-purity silicon for solar cells.

The internal block diagram of the electron beam irradiation apparatus of the 1st example which is this invention The internal block diagram of the X-ray detection apparatus of the electron beam irradiation apparatus of the first example Plan view of slit plate Internal structure of electron gun The internal block diagram of the electron beam irradiation apparatus of the 2nd example which is this invention The internal block diagram of the electron beam irradiation apparatus of the 3rd example which is this invention The internal block diagram of the X-ray detection apparatus of the electron beam irradiation apparatus of a 2nd example

<Structure of the electron beam irradiation apparatus of the first example>
The structure of the electron beam irradiation apparatus of the first example according to the present invention will be described by taking an apparatus for dissolving and purifying an irradiation object mainly composed of silicon (Si) as an example. In the present invention, the “main component” refers to an element contained in the substance in an amount of more than 90 mol%.
FIG. 1 shows an internal configuration diagram of an electron beam irradiation apparatus 10 of the first example.
The electron beam irradiation apparatus 10 of the first example includes a vacuum chamber 11, a vacuum exhaust device 13 that evacuates the inside of the vacuum chamber 11, and an electron gun 30 configured to be able to emit an electron beam into the vacuum chamber 11. doing.
The material of the vacuum chamber 11 is stainless steel or iron, and contains more iron elements than silicon elements.
The vacuum evacuation device 13 is connected to the vacuum chamber 11 so that the inside of the vacuum chamber 11 can be evacuated.
A container 50 for holding the irradiation object 60 is disposed in the vacuum chamber 11. The container 50 includes an outer container 51 and an inner container 52 disposed inside the outer container 51.

A flow path 53 is provided inside the outer container 51, and a temperature-controlled liquid can flow in the flow path 53. The inner container 52 is configured to hold the irradiation object 60 inside.
Here, the material of the outer container 51 is copper, and contains more copper element than silicon element. The material of the inner container 52 is graphite.
In addition, the container 50 of this invention is not limited to the said structure, The inner container 52 may be abbreviate | omitted and you may comprise so that the irradiation target object 60 may be mounted directly inside the outer container 52. FIG.

The electron gun 30 is formed in a cylindrical shape as described later, and has a muzzle 114 at one end. The electron gun 30 is hermetically inserted on the side wall of the vacuum chamber 11 so that the muzzle 114 is positioned inside the vacuum chamber 11.
An electron gun power source 40 is electrically connected to the electron gun 30, and when power is supplied from the electron gun power source 40, the electron gun 30 can irradiate an irradiation object 60 in the container 50 with an electron beam and heat it. It is configured.
If the wavelength of the characteristic X-ray emitted from the first element (here, silicon) that is the main component of the irradiation object 60 by the irradiation of the electron beam is the first wavelength, An outer member that emits characteristic X-rays having a second wavelength different from the first wavelength when irradiated with an electron beam is disposed in at least a part of the region other than the surface region of the irradiation object 60.
In this embodiment, the outer member is one or both of the tank wall of the vacuum chamber 11 and the container 50 that holds the irradiation target, and emits characteristic X-rays of the second wavelength by irradiation with an electron beam. Two elements (here, iron or copper) are contained more than the first element.
The electron beam irradiation apparatus 10 of the first example receives X-rays emitted from the irradiation object 60 and the outer member, detects the intensity of X-rays having a specific wavelength among the incident X-rays, and detects an abnormality from the detection result. If found, it has an abnormality detection device 80 for stopping the irradiation of the electron beam.
In the present embodiment, the abnormality detection device 80 is disposed at a position where X-rays emitted from the irradiation object 60 and X-rays emitted from the outer member are incident, and the intensity of X-rays having the second wavelength is attenuated. A cutoff filter 22 having a greater attenuation rate of the intensity of the X-rays of the first wavelength than the rate, an X-ray detection device 20 for detecting the intensity of the X-rays transmitted through the cutoff filter 22, and an X-ray detection device 20 And a control device 70 that stops the electron beam when the intensity of the detected X-ray increases beyond a predetermined threshold value.
FIG. 2 shows an internal configuration diagram of the cutoff filter 22 and the X-ray detection apparatus 20.
The X-ray detection apparatus 20 has a bottomed cylindrical case 21 having an opening at one end. The case 21 is formed of a material that blocks X-rays.
Inside the case 21, an X-ray detector 24 and a detection window 23 are arranged in this order from the bottom of the case 21 toward the opening. An X-ray detector power supply 25 is electrically connected to the X-ray detector 24.

Since the energy of the electron beam in the present embodiment is about several keV to 40 keV as will be described later, the energy of the X-ray emitted from the object irradiated with the electron beam is in the same range. As the X-ray detector 24, a detector having sensitivity to X-rays having energy (wavelength) in this range is used.
As long as the X-ray detector 24 satisfies the above requirements, various types can be used by selecting features from commercially available detectors.
For example, GM counters (Geiger-Muller counters) and proportional counters are typical examples of detectors that use gas ionization. However, since these gas detectors increase in size in principle, it is preferable to use a solid state detector typified by a semiconductor diode detector rather than a gas detector.
A scintillation counter using scintillation caused by X-rays can also be used as a detector. In this method, flash light generated by X-rays is detected by a photomultiplier tube. There are many materials (scintillators) that generate light regardless of whether they are gases, liquids, or solids, but sodium iodide (NaI (Tl)) crystals to which a small amount of thallium iodide is added are often used.

A thing attached to the above-mentioned commercially available detector can be used for the detection window 23 as it is. In general, it is necessary to select a material that can transmit X-rays having a wide energy range for the detection window 23. However, since the power to transmit X-rays with higher energy is larger, if a material that can transmit X-rays with lower energy is selected. Therefore, a material made of an element having a low atomic number is generally selected as the material of the detection window 23. For example, Be material is used for metal, and glass or plastic material is used for non-metal.
Here, the cutoff filter 22 contains one or both of aluminum (Al) and magnesium (Mg), which are elements having atomic numbers 1 to 2 smaller than silicon, which is the main component of the irradiation object 60. doing. Therefore, the cutoff filter 22 is configured to attenuate X-rays having a characteristic X-ray wavelength (first wavelength) emitted from silicon more greatly than X-rays having other wavelengths.
The cutoff filter 22 is formed in a flat plate shape larger than the opening of the case 21 and is disposed so as to cover the opening of the case 21 in an airtight manner.

The cutoff filter 22 has a sufficient strength as a vacuum wall to keep the inside of the case 21 airtight, and when the X-ray detection device 20 is disposed in the vacuum chamber 11 evacuated, X-ray detection inside the case 21 is detected. The unit 24 and the detection window 23 are configured to be isolated from the vacuum atmosphere in the vacuum chamber 11.
A disc-shaped slit plate 26 is arranged in parallel to the cutoff filter 22 on the cutoff filter 22, that is, on the side opposite to the detection window 23 when viewed from the cutoff filter 22. A rotation shaft 27 is fixed vertically at the center of the slit plate 26, and a motor 28 is attached to the rotation shaft 27.
An external motor power source 73 is electrically connected to the motor 28, and the motor 28 is configured to rotate the slit plate 26 around the central axis of the rotation shaft 27 when receiving a control signal from the rotation control device 74. Yes.

FIG. 3 shows a plan view of the slit plate 26. The slit plate 26 is provided with a strip-shaped slit hole 75.
With reference to FIG. 1, the X-ray detection device 20 is disposed in the vacuum chamber 11 at a position directly above the container 50, and the cutoff filter 22 is directed downward.
Therefore, the X-rays emitted from the irradiation object 60, the X-rays emitted from the tank wall of the vacuum chamber 11, and the X-rays emitted from the container 50 enter the cutoff filter 22.
Here, the cutoff filter 22 contains an element that absorbs X-rays of the first wavelength as described above, and the characteristic X-rays emitted from the irradiation object 60 are attenuated more than X-rays of other wavelengths. The
The X-rays that have passed through the blocking filter 22 are incident on the X-ray detection unit 24 of the X-ray detection device 20 and the intensity is detected.

  The control device 70 is connected to the X-ray detection device 20. The control device 70 monitors the intensity of the X-ray detected by the X-ray detection device 20, and here, the detected X-ray intensity increases above a predetermined threshold value, that is, the electron beam is applied to the irradiation object 60. When the intensity is higher than the intensity in the irradiation state, a stop signal is transmitted to the electron gun power source 40 to stop the emission of the electron beam from the electron gun 30.

<Structure of electron gun>
Next, the structure of the above-described electron gun 30 will be described. FIG. 4 shows an internal configuration diagram of the electron gun 30.
The electron gun 30 has a bottomed cylindrical casing 31 provided with a muzzle 114 which is an opening at one end.
Inside the casing 31, a gun chamber 110, a connection path 111, an intermediate chamber 112, and a discharge path 113 are provided in this order from the bottom of the casing 31 toward the muzzle 114 on the central axis.
The gun chamber 110 and the intermediate chamber 112 are connected to electron gun evacuation units 117a and 117b, respectively. The electron gun evacuation units 117a and 117b are configured to be able to evacuate the chambers 110 and 112, respectively. The connection path 111 is formed so that the inner periphery is smaller than the gun chamber 110 and the intermediate chamber 112, and is configured to connect the inside of the gun chamber 110 and the inside of the intermediate chamber 112. Therefore, the connection path 111 between the gun chamber 110 and the intermediate chamber 112 is connected. And has a differential exhaust structure. A partition valve 39 is disposed inside the connection path 111.
The interior of the intermediate chamber 112 is connected to the muzzle 114 via the discharge path 113.
Hereinafter, the bottom side of the muzzle 114 of the casing 31 is referred to as upstream, and the opposite side is referred to as downstream.

In the gun chamber 110, the filament 32, the cathode 33, the Wehnelt 34, and the anode 35 are arranged in this order from the upstream side to the downstream side of the housing 31 on the central axis of the housing 31.
A filament power supply 41 is electrically connected to the filament 32. The filament power source 41 is configured to heat the filament 32 by passing a current through the filament 32.
A cathode heating power source 42 is electrically connected to the filament 32 and the cathode 33. The cathode heating power source 42 is configured to be able to apply a voltage between the filament 32 and the cathode 33 so that the potential of the cathode 33 becomes positive with respect to the filament 32.

The Wehnelt 34 is formed in a bottomless cylindrical shape having a larger inner circumference than the cathode 33, and is directed so that its own central axis coincides with the central axis of the casing 31. The Wehnelt 34 is electrically connected to the cathode 33.
The anode 35 is formed in a bottomless cylindrical shape, and is directed so that its center axis coincides with the center axis of the housing 31. The anode 35 is electrically connected to the housing 31.

A high voltage power supply 43 is electrically connected to the casing 31 and the cathode 33. The high voltage power supply 43 is configured to be able to apply a voltage between the casing 31 and the cathode 33 so that the potential of the cathode 33 is negative with respect to the potential of the casing 31, that is, the potential of the anode 35.
Downstream of the anode 35, a first lens 36, a second lens 37, and an oscillating coil (magnetic field forming means) 38 are arranged in this order along the central axis of the housing 31.
Here, the first lens 36 is disposed outside the connection path 111 so as to surround the connection path 111, and the second lens 37 is disposed outside the discharge path 113 so as to surround the discharge path 113.
A lens power supply 44 is electrically connected to each of the first and second lenses 36 and 37. The lens power supply 44 is configured to allow current to flow through the first and second lenses 36 and 37 to form magnetic fields in the connection path 111 and the emission path 113, respectively.

The oscillating coil (magnetic field forming means) 38 is disposed so as to surround the muzzle 114 outside the discharge path 113. A coil power supply 45 is electrically connected to the swing coil 38. The coil power supply 45 is configured to allow a current to flow through the oscillating coil 38 to form a magnetic field inside the muzzle 114 (electron beam trajectory).
A magnetic field control device 49 is connected to the coil power supply 45. The magnetic field control device 49 is configured to change the current supplied from the coil power supply 45 to the oscillating coil 38 to control the direction and magnitude of the magnetic field formed in the orbit of the electron beam.
When the power supply device of the electron gun 30 is referred to as an electron gun power supply 40, the electron gun power supply 40 includes a filament power supply 41, a cathode heating power supply 42, a high voltage power supply 43, a lens power supply 44, and a coil power supply 45.

<Electron beam irradiation method>
Next, an electron beam irradiation method using the above-described electron beam irradiation apparatus 10 will be described.
The threshold value of the X-ray intensity used for the determination of abnormality detection is determined in advance so that the intensity when the electron beam is irradiated on the irradiation object 60 is equal to or less than the threshold value.
With reference to FIG. 1, the inside of the vacuum chamber 11 is evacuated by the evacuation device 13. Thereafter, evacuation is continued and the vacuum atmosphere in the vacuum chamber 11 is maintained.
The slit plate 26 of the X-ray detection apparatus 20 is rotated on the cutoff filter 22 (that is, the position facing the exposed surface of the cutoff filter 22).
On the side wall of the vacuum chamber 11, a melting material adding device 12 is inserted in an airtight manner. The melting material adding device 12 can carry the irradiation object 60 from the outside to the inside of the vacuum chamber 11 while maintaining the vacuum atmosphere in the vacuum chamber 11, and can place the irradiation object 60 inside the inner container 52. It is configured.
The melting material adding apparatus 12 is operated to carry the irradiation object 60 into the vacuum tank 11 while maintaining the vacuum atmosphere in the vacuum tank 11, and place the irradiation object 60 inside the inner container 52.
A temperature-controlled liquid is circulated in a flow path 53 provided inside the outer container 51. Thereafter, the circulation of the temperature-controlled liquid is continued.

Referring to FIG. 4, when the inside of the vacuum chamber 11 is evacuated, the inside of the casing 31 of the electron gun 30 that is airtightly inserted into the side wall of the vacuum chamber 11 is also evacuated.
When the pressure in the vacuum chamber 11 is in the range of 10 ⁻² Pa, the inside of the gun chamber 110 and the intermediate chamber 112 of the electron gun 30 is evacuated by the electron gun evacuation units 117 a and 117 b, and the partition valve 39 is opened.
Since the intermediate chamber 112 is provided and the working exhaust structure is provided, the pressure in the vacuum chamber 11 is increased by electron beam irradiation and the like, and the pressure in the gun chamber 110 is reduced to about 1 × 10 ⁻¹ Pa. It can be kept at ^10-3 Pa or less. Thereby, abnormal discharge in the gun chamber 110 can be prevented, and burning of the filament 32 and the cathode 33 can be prevented.
The casing 31, the anode 35, the vacuum chamber 11, and the container 50 of the electron gun 30 are all electrically grounded.

A voltage is applied between the filament 32 and the cathode 33 so that the potential of the cathode 33 becomes positive with respect to the potential of the filament 32. Further, a voltage is applied between the cathode 33 and the anode 35 so that the potential of the cathode 33 is negative (in this case, −40 kV) with respect to the ground potential (0 V) of the anode 35. Further, a current is supplied to the first and second lenses 36 and 37 to form magnetic fields in the connection path 111 and the discharge path 113, respectively, and a current is supplied to the swing coil 38 to form a magnetic field in the muzzle 114. Keep it.
When the intermediate chamber 112 enters the 10 ⁻³ Pa level and the gun chamber 110 enters the 10 ⁻⁴ Pa level, current is supplied from the filament power supply 41 to the filament 32 to heat the filament 32. When the filament 32 reaches a high temperature (here, 2800 K), thermoelectrons are generated from the filament 32.
The thermoelectrons are accelerated toward the cathode 33, collide with the cathode 33, and heat the cathode 33.

Thermoelectrons are generated from the heated cathode 33. The amount of generated thermoelectrons increases as the temperature of the cathode 33 increases. The temperature of the cathode 33 is controlled by the cathode heating power source 42, and accordingly, the amount of thermoelectrons generated is controlled by the cathode heating power source 42.
The Wehnelt 34 has the same potential as that of the cathode 33 and serves to suppress the divergence of electrons from the cathode 33 and lead it to the anode 35.
Electrons that have passed through the inside of the cylindrical shape of the anode 35 are converged by the magnetic field of the first lens 36, pass through the opening of the partition valve 39, pass through the intermediate chamber 112, and then converged again by the magnetic field of the second lens 37. The Further, the electrons are subjected to trajectory correction by the magnetic field of the oscillating coil 38 and are emitted into the vacuum chamber 11.
The electrons generated from the cathode 33 in this manner are linearly shaped and transported inside the casing 31 of the electron gun 30 and are therefore usually called electron beams.

As described above, the casing 31, the anode 35, the vacuum chamber 11, and the container 50 of the electron gun 30 are all electrically grounded, and the irradiation object 60 is also electrically grounded via the container 50.
The electron beam is first accelerated by the difference (40 kV) between the potential of the cathode 33 (here, 40 kV) and the ground potential (0 V) of the anode 35, and acquires 40 keV energy. After that, it passes through the ground potential space (that is, the electric field free space), and is irradiated to the irradiation object 60 at the ground potential with the energy of 40 keV, and the irradiation object 60 is heated (see FIG. 1).

Characteristic X-rays having energy (first wavelength) of 1.739 keV (Kα ray) or 1.840 keV (Kβ ray) are emitted from silicon, which is the main component of the irradiation object 60, by the electron beam irradiation.
X-rays emitted from the irradiation object 60 enter the cutoff filter 22. Since the cutoff filter 22 contains an element that absorbs X-rays of the first wavelength, the incident X-rays are attenuated more greatly than X-rays of other wavelengths by the cutoff filter 22.
The X-rays that have passed through the blocking filter 22 enter the X-ray detection device 20, and the intensity is detected. The control device 70 monitors the value of the X-ray intensity detected by the X-ray detection device 20.
While the electron beam is irradiated to the surface region (called irradiation surface) of the irradiation object 60 exposed in the vacuum chamber 11, the intensity of X-rays detected by the X-ray detection device 20 is substantially constant (noise range). And within a predetermined threshold value.
At this time, the magnetic field of the oscillating coil 38 may be controlled to oscillate the electron beam trajectory so that the irradiation position of the electron beam moves within the irradiation surface of the irradiation object 60. Since the irradiation surface of the irradiation object 60 is uniformly heated, it is possible to prevent the irradiation surface from being uneven due to local heating.

For example, when an abnormal current is supplied to the oscillating coil 38 during irradiation of the electron beam, and the irradiation position of the electron beam deviates from the irradiation surface of the irradiation object 60, the electron beam is outside the irradiation surface and the inner container 52. It hits the container 51 in order.
Here, the material of the outer container 51 is copper (Cu), and contains more copper element than silicon element. Therefore, the outer container 51 irradiated with the electron beam has energy of characteristic X-rays of copper ( The X-ray of 8.040 keV (Kα ray) or 8.979 keV (Kβ ray), which is the second wavelength), is emitted with greater intensity than the X-ray of the first wavelength.
X-rays emitted from the container 50 enter the cutoff filter 22. The X-ray of the second wavelength passes through the cutoff filter 22 without being attenuated as compared with the X-ray of the first wavelength, and enters the X-ray detection device 20.
Therefore, the intensity of X-rays detected by the X-ray detection device 20 increases from the intensity when the electron beam is irradiated on the irradiation object 60 and increases from a predetermined threshold value. The control device 70 transmits a stop signal to the electron gun power supply 40 to stop the emission of the electron beam from the electron gun 30.
Accordingly, the emission of the electron beam can be stopped before the outer container 51 is melted or broken, and it is possible to prevent the outer container 51 from being perforated and causing water leakage in the vacuum.

For example, when an abnormal current is supplied to the oscillating coil 38 during irradiation of the electron beam and the irradiation position of the electron beam deviates from the irradiation surface of the irradiation object 60 more than the above case, the electron beam is outside the irradiation surface. It hits the tank wall of the vacuum chamber 11.
Here, the material of the vacuum chamber 11 is stainless steel or iron, and contains more elements of iron (Fe) than silicon elements. Therefore, the characteristics of the iron from the tank wall of the vacuum chamber 11 irradiated with the electron beam. 6.398 keV (Kα ray) or 7.110 keV (Kβ ray) X-ray energy (second wavelength) is emitted with a greater intensity than the X-ray of the first wavelength.
X-rays emitted from the tank wall of the vacuum chamber 11 enter the cutoff filter 22. The X-ray of the second wavelength passes through the cutoff filter 22 without being attenuated as compared with the X-ray of the first wavelength, and enters the X-ray detection device 20.
Therefore, the intensity of X-rays detected by the X-ray detection device 20 increases from the intensity when the electron beam is irradiated on the irradiation object 60 and increases from a predetermined threshold value. The control device 70 transmits a stop signal to the electron gun power supply 40 to stop the emission of the electron beam from the electron gun 30.
As a result, the emission of the electron beam can be stopped before the tank wall of the vacuum tank 11 is melted or broken, and a hole is formed in the tank wall of the vacuum tank 11 so that the atmosphere enters the vacuum tank 11, and the cathode 33 in a high temperature state It is possible to prevent the filament 32 from being damaged.

During irradiation of the electron beam, for example, if the oscillation coil 38 is short-circuited and the irradiation surface of the irradiation object 60 is continuously heated, a hole is formed in the irradiation object 60, and the electron beam is not emitted from the inner container 52. Hit the inner surface. Since the inner container 52 is thin, a hole is instantly opened, and the electron beam strikes the inner surface of the outer container 51.
Since the material of the outer container 51 is copper and contains more copper element than silicon element, the characteristic X-ray energy (second wavelength) of copper is emitted from the outer container 51 irradiated with the electron beam. 8.040 keV (Kα ray) or 8.979 keV (Kβ ray) is emitted with a greater intensity than the first wavelength X-ray.

X-rays emitted from the outer container 51 enter the cutoff filter 22. The X-ray of the second wavelength passes through the cutoff filter 22 without being attenuated as compared with the X-ray of the first wavelength, and enters the X-ray detection device 20.
Therefore, the intensity of X-rays detected by the X-ray detection device 20 increases from the intensity when the electron beam is irradiated on the irradiation object 60 and increases from a predetermined threshold value. The control device 70 transmits a stop signal to the electron gun power supply 40 to stop the emission of the electron beam from the electron gun 30.
Thereby, it is possible to stop the emission of the electron beam before the outer container 51 is melted and broken, and it is possible to prevent the melted irradiation object 60 from leaking to the outside of the outer container 51 by opening a hole in the outer container 51.
That is, in the electron beam irradiation apparatus 10 of the present invention, when the wavelength of the characteristic X-ray emitted from the first element (silicon) that is the main component of the irradiation object 60 by the electron beam irradiation is the first wavelength, At least a part of the region other than the surface region of the irradiation object 60 among the regions that can be irradiated with the electron beam emits characteristic X-rays having a second wavelength different from the first wavelength by the electron beam irradiation. A member is disposed, and the cutoff filter 22 has an X-ray attenuation rate of the first wavelength larger than the attenuation rate of the X-ray intensity of the second wavelength.

In the present embodiment, the power of the irradiation electron beam is determined by the electron beam current. When the current is 1 A, 40 kV × 1 A = 40 kW.
The irradiation object 60 irradiated with the electron beam and heated is dissolved, and impurities contained in the irradiation object 60 are evaporated.
If vapor adheres to and accumulates on the cutoff filter 22 of the X-ray detection device 20, the amount of X-ray transmission through the cutoff filter 22 decreases, leading to a decrease in detection sensitivity of the X-ray detection device 20, but here on the cutoff filter 22 ( That is, since the slit plate 26 is rotated at a position facing the exposed surface of the cutoff filter 22), the vapor is suppressed from reaching the cutoff filter 22.
By changing the width of the slit hole 75 of the slit plate 26, the amount of vapor reaching the blocking filter 22 can be adjusted. When the width of the slit hole 75 is narrowed to reduce the amount of vapor that reaches, the amount of X-rays incident on the blocking filter 22 also decreases. However, in this embodiment, X emitted from the irradiation object 60 is reduced. The intensity of the line is sufficiently larger than the detection performance of the X-ray detector 24, and there is no problem in measuring the intensity of the X-ray.
Since the vacuum chamber 11 is evacuated, the impurity vapor is removed and the irradiation object 60 is purified.

An inclination mechanism 56 is connected to the container 50. The tilt mechanism 56 is configured to tilt the container 50 from the horizontal position by a predetermined angle (here, 90 degrees).
After the dissolution and purification are completed, the tilting mechanism 56 is operated, and the melted irradiation object 60 is emptied in the mold container 57 installed in the vacuum chamber 11.
Next, the tilting mechanism 56 is operated to return the container 50 to the horizontal position, the dissolved material adding device 12 is operated to place the irradiation object 60 in the inner container 52, and the electron gun 30 is irradiated again with the electron beam. The object 60 is irradiated and dissolved and purified.
This cycle is repeated, and when the mold container 57 becomes full, the vacuum chamber 11 is released to the atmosphere, and after the purified irradiation object is taken out from the mold container 57, the mold container 57 is returned to the original position in the vacuum chamber 11. The vacuum evacuation in the vacuum chamber 11 is resumed, and the next dissolution purification cycle starts.

In the above description, the present invention has been described by taking the vacuum dissolution purification of silicon as an example. However, the present invention is not limited to this as long as it has a step of irradiating and heating an irradiation object 60 with a high-power electron beam of 10 kW or more. It can also be used for dissolving and purifying active metals such as titanium, vacuum materials such as stainless steel, and refractory metals such as molybdenum and tantalum. It can also be used for vacuum deposition of aluminum, titanium, copper and the like.
The power of the electron beam is adjusted according to the type of the irradiation object 60. Compared to silicon, titanium, and stainless steel, higher power is required to dissolve tantalum and tungsten, which are high melting point metals.
When the irradiation object 60 is titanium (Ti), a material containing any one element or two or more elements of scandium (Sc), calcium (Ca), and potassium (K) is used as the cutoff filter 22. Use it. Since calcium and potassium are highly reactive with oxygen, these compounds may be used.

  In the case where the irradiation object 60 is an element having a large atomic number, for example, in the case of tantalum (Ta) or tungsten (W), the electron energy necessary for excitation of Kα rays and Kβ rays exceeds 40 keV. Since Kα rays and Kβ rays are not generated by the energy of the electron beam, the shielding of Lα rays and Lβ rays generated by this energy is considered. In this case, as the material of the cutoff filter 22, a material containing either one element or both elements of iron or copper can be used. When iron or copper is used as a filter, since the absorption edge thereof is larger than its own characteristic X-ray, the characteristic X-ray of iron or copper generated from the tank wall of the vacuum chamber 11 or the container 50 can be transmitted without being absorbed. it can.

The cut-off filter 22 used in the present invention is as described above as long as it has a high-pass filter or band-pass filter function that attenuates one of the intensities of the X-rays of the first and second wavelengths to a greater extent than the other. However, the present invention is not limited to the case where the attenuation factor of the X-ray of the second wavelength is larger than the attenuation factor of the X-ray of the second wavelength. The X-ray attenuation factor of the first wavelength may be formed smaller than the attenuation factor.
For example, in the case of vacuum melting purification of silicon, the cutoff filter 22 contains an element having an atomic number 1 to 2 smaller than copper and an element having an atomic number 1 to 2 smaller than iron, and the intensity of X-rays at the first wavelength. The control device 70 is configured so that the intensity of the X-ray having the second wavelength is greatly attenuated, and the control device 70 has an intensity when the detected X-ray intensity is in a state where the irradiation target 60 is irradiated with the electron beam. When the value is further reduced and the value is lower than a predetermined threshold value, a stop signal is transmitted to the electron gun power source 40 to stop the emission of the electron beam from the electron gun 30.
The high-pass filter has a function of attenuating X-rays below the target energy more than X-rays having higher energy, and the band-pass filter converts X-rays with energy outside the target range to energy within the range. This is a function that attenuates more than X-rays.
The electron beam irradiation apparatus 10 of the first example is inexpensive because the X-ray detector 20 having no spectroscopic function is used, and the present invention can be attached to all apparatuses using a high-power electron beam at a low cost. it can. In addition, compared to an X-ray detector having a spectroscopic function, the detection speed of the intensity of X-rays having a specific wavelength is high, and damage caused when an electron beam deviates from an irradiation target can be reduced.

<Structure of electron beam irradiation apparatus of second example>
The structure of the electron beam irradiation apparatus of the second example of the present invention will be described.
FIG. 5 is a view for explaining an embodiment of the second example of the electron beam irradiation apparatus using the present invention, and is an internal configuration diagram of the electron beam irradiation apparatus 10 ′ of the second example. Of the electron beam irradiation apparatus 10 ′ of the second example, the same parts as those of the structure of the electron beam irradiation apparatus 10 of the first example are denoted by the same reference numerals and description thereof is omitted.
In the electron beam irradiation apparatus 10 ′ of the second example, unlike the electron beam irradiation apparatus 10 of the first example, the cutoff filter 22 and the X-ray detection apparatus 20 of the abnormality detection device 80 c are located next to the container 50 in the vacuum chamber 11. It is arranged in the direction (horizontal direction) as far as possible from the container 50.
In general, the amount of vapor reached is inversely proportional to the square of the distance from the evaporation source (irradiation target 60 in the present invention). Further, the vapor angular distribution is proportional to cos ⁿ Φ, where 0 degree is the direction directly above the evaporation source and Φ is the angle from there (n takes a value of 4 to 8). Therefore, the amount of steam released in the lateral direction is cos ⁿ 90 ° = 0. Moreover, since the vapor | steam which reaches | attains a wall adheres to a wall and accumulates, it hardly reflects on a wall. Accordingly, the vapor hardly reaches the X-ray detection device 20 in the electron beam irradiation device 10 ′ of the second example.

On the other hand, X-rays are emitted from the irradiation object 60 because the ratio of reflection by the inner wall of the vacuum chamber 11 and other structural members (that is, the casing 31 of the electron gun 30, the dissolved material adding device 12, and the container 50) is large. Characteristic X-rays enter the X-ray detector 20 and the intensity is detected.
Therefore, in the electron beam irradiation apparatus 10 ′ of the second example, the deposition of vapor on the cutoff filter 22 of the X-ray detection apparatus 20 is reduced, and the replacement frequency of the cutoff filter 22 can be reduced. Furthermore, the slit plate 26, the rotating shaft 27, and the motor 28 can be removed from the X-ray detection apparatus 20.
The electron beam irradiation method using the electron beam irradiation apparatus 10 ′ of the second example is the same as the electron beam irradiation method using the electron beam irradiation apparatus 10 of the first example, and description thereof is omitted.
<Structure of electron beam irradiation apparatus of third example>
The structure of the electron beam irradiation apparatus of the third example of the present invention will be described.
FIG. 6 is an internal configuration diagram of the electron beam irradiation apparatus 110 of the third example. Of the electron beam irradiation apparatus 110 of the third example, the same parts as those of the structure of the electron beam irradiation apparatus 10 of the first example are denoted by the same reference numerals and description thereof is omitted.
The electron beam irradiation device 110 of the third example has an abnormality detection device 180 having a configuration different from that of the abnormality detection device 80 of the electron beam irradiation device 10 of the first example. That is, the abnormality detection device 180 of the electron beam irradiation apparatus 110 of the third example is disposed at a position where X-rays emitted from the irradiation object 60 and X-rays emitted from the outer member are incident, and the incident X-rays are incident. X-ray detection device 120 for detecting the intensity of X-rays having a specific wavelength, and the intensity of X-rays having a specific wavelength detected by X-ray detection device 120 when the electron beam is applied to irradiation object 60. When the intensity is different from the X-ray intensity of the specific wavelength, the controller 170 is provided to stop the electron beam.
FIG. 7 shows an internal configuration diagram of the X-ray detection apparatus 120. Parts having the same structure as those of the X-ray detection apparatus 20 of the electron beam irradiation apparatus 10 of the first example are denoted by the same reference numerals and description thereof is omitted.
An X-ray detector 124 is disposed inside the case 21 of the X-ray detector 120. An X-ray detection device power supply 25 is electrically connected to the X-ray detection unit 124.
Since the electron beam energy in this embodiment is about several keV to 40 keV, the energy of X-rays emitted from the object irradiated with the electron beam is in the same range. The X-ray detector 124 has a sensitivity to X-rays with energy (wavelength) in this range, and is a detector for elemental analysis commercially available for X-rays (a type using a diffraction grating or a lithium drift type semiconductor type). ) Is used.
A detection window 123 is disposed at the opening of the case 21 so as to cover the inside of the case 21 in an airtight manner. The detection window 123 is thin (10 μm to 50 μm) for transmitting X-rays and has a vacuum wall having sufficient strength to keep the inside of the case 21 airtight. In this embodiment, a low atomic number Be metal is used. A foil or plastic film combined with a metal mesh as a reinforcing agent is used.
The control device 170 is connected to the X-ray detection device 120 and monitors the X-ray intensity (intensity distribution and spectroscopic spectrum for each specific wavelength) detected by the X-ray detection device 120, and the electron beam is irradiated. The difference for every wavelength with the intensity | strength of the X-ray of a specific wavelength at the time of the state which is irradiated to the object 60 is calculated | required, and the electron beam is irradiated to the irradiation object 60 for the detected intensity | strength of the X-ray of a specific wavelength. When the X-ray intensity of the specific wavelength is different from that in the current state, a stop signal is transmitted to the electron gun power supply 40 to stop the emission of the electron beam from the electron gun 30.
The electron beam irradiation method using the electron beam irradiation apparatus 110 of the third example is the same as the electron beam irradiation method using the electron beam irradiation apparatus 10 of the first example, except for the abnormality detection method. Descriptions other than are omitted.
An abnormality detection method for the electron beam irradiation method using the electron beam irradiation apparatus 110 of the third example will be described.
In the same manner as the electron beam irradiation method using the electron beam irradiation apparatus 10 of the first example, when an electron beam 30 is irradiated from the electron gun 30 to the irradiation object 60, the silicon is used as the main component of the irradiation object 60. Characteristic X-rays having a wavelength of 1 are emitted and enter the X-ray detector 120. The control device 170 monitors the intensity of X-rays having a specific wavelength detected by the X-ray detection device 120.
For example, when an abnormal current is supplied to the oscillating coil 38 during irradiation of the electron beam and the irradiation position of the electron beam deviates from the irradiation surface of the irradiation target 60, the electron beam is exposed to the container 50 or vacuum chamber outside the irradiation surface. 11 hits the wall.
Since the material of the outer container 51 is copper (Cu) and contains more copper element than silicon element, the outer container 51 irradiated with the electron beam has a second wavelength different from the first wavelength. Wavelength characteristic X-rays are emitted.
Further, the material of the vacuum chamber 11 is stainless steel or iron, and contains more iron element than silicon element, so that it differs from the first wavelength from the chamber wall of the vacuum chamber 11 irradiated with the electron beam. A characteristic X-ray of the second wavelength is emitted.
The characteristic X-ray of the second wavelength emitted from the vessel 50 or the vessel wall of the vacuum vessel 11 is incident on the X-ray detection device 120, and the X-ray detection device 120 is irradiated with the electron beam 60. The intensity of the X-ray having a specific wavelength different from the intensity of the X-ray having the specific wavelength in the state is detected. The control device 170 transmits a stop signal to the electron gun power supply 40 to stop the emission of the electron beam from the electron gun 30.
As a result, the emission of the electron beam can be stopped before the vessel 50 or the vessel wall of the vacuum vessel 11 is dissolved or broken.
In the electron beam irradiation apparatus 10 of the first example, the cutoff filter 22 containing a predetermined element is necessary according to the type of the irradiation object 60, but in the electron beam irradiation apparatus 110 of the third example, the cutoff filter 22 is unnecessary. There is an advantage of becoming.
The arrangement of the X-ray detection device 120 of the electron beam irradiation apparatus 110 of the third example is not limited to the above configuration, and the container is arranged in the lateral direction (horizontal direction) of the container 50 as in the electron beam irradiation apparatus 10 ′ of the second example. A configuration arranged as far as possible from 50 is also included in the present invention. In this case, vapor adhesion to the X-ray detection device 120 is reduced, and the replacement frequency of the X-ray detection device 120 can be reduced.

10, 10 ', 110 ... Electron beam irradiation device 11 ... Vacuum chamber 13 ... Vacuum exhaust device 20, 120 ... X-ray detection device 22 ... Blocking filter 30 ... Electron gun 38 ... Magnetic field forming means Moving coil)
49... Magnetic field control device 52... Crucible part 60 .. Irradiation object 70 and 170... Control device 80 and 180.

The interior of the outer container 51 the flow channel 53 is provided, thereby making it possible to flow a liquid whose temperature is managed in the flow path 53. The inner container 52 is configured to hold the irradiation object 60 inside.
Here, the material of the outer container 51 is copper, and contains more copper element than silicon element. The material of the inner container 52 is graphite.
Incidentally, the container 50 of the present invention is not limited to the above construction, by omitting the inner container 52, it may be configured to place the direct irradiation target object 60 inside the outer container 5 1.

<Structure of electron gun>
Next, the structure of the above-described electron gun 30 will be described. FIG. 4 shows an internal configuration diagram of the electron gun 30.
The electron gun 30 has a bottomed cylindrical casing 31 muzzle 114 is found provided an opening at one end.
Inside the casing 31, a gun chamber 110, a connection path 111, an intermediate chamber 112, and a discharge path 113 are provided in this order from the bottom of the casing 31 toward the muzzle 114 on the central axis.
The gun chamber 110 and the intermediate chamber 112 are connected to electron gun evacuation units 117a and 117b, respectively. The electron gun evacuation units 117a and 117b are configured to be able to evacuate the chambers 110 and 112, respectively. The connection path 111 is formed so that the inner periphery is smaller than the gun chamber 110 and the intermediate chamber 112, and is configured to connect the inside of the gun chamber 110 and the inside of the intermediate chamber 112. Therefore, the connection path 111 between the gun chamber 110 and the intermediate chamber 112 is connected. And has a differential exhaust structure. A partition valve 39 is disposed inside the connection path 111.
The interior of the intermediate chamber 112 is connected to the muzzle 114 via the discharge path 113.
Hereinafter, the bottom side of the muzzle 114 of the casing 31 is referred to as upstream, and the opposite side is referred to as downstream.

Referring to FIG. 4, when the inside of the vacuum chamber 11 is evacuated, the inside of the casing 31 of the electron gun 30 that is airtightly inserted into the side wall of the vacuum chamber 11 is also evacuated.
When the pressure in the vacuum chamber 11 is in the range of 10 ⁻² Pa, the inside of the gun chamber 110 and the intermediate chamber 112 of the electron gun 30 is evacuated by the electron gun evacuation units 117 a and 117 b, and the partition valve 39 is opened.
Due to the intermediate chamber 112 to a differential exhaust structure is provided, thereafter, the pressure in the vacuum chamber 11 is raised by the irradiation of an electron beam or the like, the pressure of 1 × 10 ^-1 cancer chamber 110 even when the order of Pa It can be kept at 5 × 10 ⁻³ Pa or less. Thereby, abnormal discharge in the gun chamber 110 can be prevented, and burning of the filament 32 and the cathode 33 can be prevented.
The casing 31, the anode 35, the vacuum chamber 11, and the container 50 of the electron gun 30 are all electrically grounded.

For example, when an abnormal current is supplied to the oscillating coil 38 during irradiation of the electron beam, and the irradiation position of the electron beam deviates from the irradiation surface of the irradiation object 60, the electron beam is outside the irradiation surface and the inner container 52. It hits the container 51 in order.
Here, the material of the outer container 51 is copper (Cu), and contains more copper element than silicon element. Therefore, the outer container 51 irradiated with the electron beam has energy of characteristic X-rays of copper ( The X-ray of 8.040 keV (Kα ray) or 8.979 keV (Kβ ray), which is the second wavelength), is emitted with greater intensity than the X-ray of the first wavelength.
X-rays emitted from the container 50 enter the cutoff filter 22. The X-ray of the second wavelength passes through the cutoff filter 22 without being attenuated as compared with the X-ray of the first wavelength, and enters the X-ray detection device 20.
Therefore, the intensity of X-rays detected by the X-ray detection device 20 increases from the intensity when the electron beam is irradiated on the irradiation object 60 and increases from a predetermined threshold value. The control device 70 transmits a stop signal to the electron gun power supply 40 to stop the emission of the electron beam from the electron gun 30.
Accordingly, the emission of the electron beam can be stopped before the outer container 51 is melted or broken, and it is possible to prevent the outer container 51 from being perforated and causing a water leakage phenomenon in the vacuum.

Claims (16)

A vacuum chamber;
An evacuation device for evacuating the vacuum chamber;
An electron gun configured to emit an electron beam into the vacuum chamber;
Have
The irradiation object arranged in the vacuum chamber is configured to heat the irradiation object by irradiating the electron beam from the electron gun,
When the wavelength of characteristic X-rays emitted from the first element contained in the irradiation object by more than 90 mol% by irradiation with the electron beam is the first wavelength,
At least a part of the region other than the surface region of the irradiation object among the regions that can be irradiated with the electron beam has a characteristic X-ray having a second wavelength different from the first wavelength by the irradiation of the electron beam. An electron beam irradiation apparatus in which an outer member to be emitted is arranged,
An abnormality that stops the electron beam when X-rays emitted from the irradiation object and the outer member are incident, the intensity of X-rays having a specific wavelength among the incident X-rays is detected, and an abnormality is detected from the detection result A detection device;
An electron beam irradiation apparatus.   2. The electron beam irradiation apparatus according to claim 1, wherein the outer member contains a second element that emits characteristic X-rays of the second wavelength when irradiated with the electron beam more than the first element.   The electron beam irradiation apparatus according to claim 1, wherein the outer member is one or both of a tank wall of the vacuum chamber and a container holding the irradiation object. The abnormality detection device is:
A cutoff filter in which the attenuation factor of the X-ray intensity of the first wavelength is larger than the attenuation factor of the X-ray intensity of the second wavelength;
An X-ray detector for detecting the intensity of X-rays transmitted through the blocking filter;
A control device that stops the electron beam when the intensity of the X-ray detected by the X-ray detection device increases above a predetermined threshold;
The electron beam irradiation apparatus according to claim 1, comprising: The electron beam irradiation apparatus according to claim 4, wherein the first element is silicon.
The said cutoff filter is an electron beam irradiation apparatus containing any one element or both elements among aluminum and magnesium. The abnormality detection device is:
A cutoff filter in which the attenuation rate of the X-ray intensity of the first wavelength is smaller than the attenuation rate of the X-ray intensity of the second wavelength;
An X-ray detector for detecting the intensity of X-rays transmitted through the blocking filter;
A control device for stopping the electron beam when the intensity of the X-ray detected by the X-ray detection device decreases below a predetermined threshold;
The electron beam irradiation apparatus according to claim 1, comprising: The abnormality detection device is:
An X-ray detector for detecting the intensity of X-rays having a specific wavelength among the incident X-rays;
When the X-ray intensity of the specific wavelength detected by the X-ray detection device is different from the X-ray intensity of the specific wavelength when the electron beam is irradiated on the irradiation object, the electron beam is A control device to stop;
The electron beam irradiation apparatus according to claim 1, comprising: Magnetic field forming means for forming a magnetic field in the trajectory of the electron beam;
And a magnetic field control device for controlling the direction and magnitude of the magnetic field by the magnetic field forming means so that the irradiation position of the electron beam moves inside the surface area of the irradiation object exposed in the vacuum chamber. Item 2. An electron beam irradiation apparatus according to Item 1. When the wavelength of the characteristic X-rays emitted from the first element contained in the irradiation object by more than 90 mol% by irradiation with the electron beam is the first wavelength,
A characteristic X-ray having a second wavelength different from the first wavelength by being irradiated with the electron beam, which is disposed in at least a part of a region other than the surface region of the irradiation object among the regions that can be irradiated with the electron beam. Using an outer member that releases
While evacuating the inside of the vacuum chamber, it is an electron beam irradiation method for irradiating the irradiation object placed in the vacuum chamber with an electron beam and heating the irradiation object,
During irradiation of the electron beam, the X-ray intensity of a specific wavelength is detected from the X-rays emitted from the irradiation object and the outer member, and when an abnormality is detected from the detection result, the electron beam is stopped. Electron beam irradiation method.   The electron beam irradiation method according to claim 9, wherein the outer member contains a second element that emits characteristic X-rays of the second wavelength when irradiated with the electron beam more than the first element.   11. The electron beam irradiation method according to claim 9, wherein the outer member is one or both of a tank wall of the vacuum chamber and a container holding the irradiation object. Using a cutoff filter having a greater attenuation rate of the X-ray intensity of the first wavelength than the attenuation rate of the X-ray intensity of the second wavelength,
Predetermining the threshold of X-ray intensity,
During irradiation of the electron beam, the intensity of X-rays emitted from the irradiation object and the outer member and transmitted through the blocking filter is detected, and the detected X-ray intensity increases above a predetermined threshold value. Then, the electron beam irradiation method according to claim 9, wherein the electron beam is stopped. The electron beam irradiation method according to claim 12, wherein the first element is silicon.
The blocking filter is an electron beam irradiation method containing one or both of aluminum and magnesium. Using a cutoff filter having a smaller attenuation factor of the X-ray intensity of the first wavelength than the attenuation factor of the X-ray intensity of the second wavelength,
Predetermining the threshold of X-ray intensity,
During irradiation with the electron beam, the intensity of X-rays emitted from the irradiation object and the outer member and transmitted through the blocking filter is detected, and the detected X-ray intensity decreases below a predetermined threshold value. Then, the electron beam irradiation method according to claim 9, wherein the electron beam is stopped.   During the irradiation of the electron beam, the X-ray intensity of a specific wavelength among the X-rays emitted from the irradiation object and the outer member is detected, and the detected X-ray intensity of the specific wavelength is The electron beam irradiation method according to claim 9, wherein the electron beam is stopped when different from the intensity of X-rays having a specific wavelength when the irradiation object is being irradiated.   The electron beam according to claim 9, wherein the irradiation object is heated while moving the irradiation position of the electron beam inside the surface area of the irradiation object exposed in the vacuum chamber during the irradiation of the electron beam. Irradiation method.

Images