JP2022171067A - Charged particle beam generation device - Google Patents

Abstract

To irradiate a desired position with a charged particle beam.SOLUTION: An X-ray module 100 comprises an electron gun 4 which emits an electron beam EB along an emission axis AE, and solenoids 50A, 50B which generate magnetic fields. The solenoids 50A, 50B are apart from each other along an arrangement direction D crossing the emission axis AE. The electron gun 4 is so arranged that the emission axis AE is located between the solenoids 50A, 50B. A magnetic pole direction SA extending from the N pole to the S pole of the one solenoid 50A is parallel with the other magnetic pole direction extending from the N pole to the S pole of the other solenoid 50B. The magnetic pole directions SA, SB extend in a direction crossing the emission axis AE when viewed from the arrangement direction D. The magnetic pole direction SA is opposite to the magnetic pole direction SB.SELECTED DRAWING: Figure 1

Description

The present invention relates to a charged particle beam generator.

A charged particle is a particle that carries an electrical charge. A charged particle beam generator generates, for example, an electron beam that is a charged particle beam. A charged particle beam generator may be used as an electron beam source. Also, the charged particle beam generator may constitute an X-ray source together with a target made of metal such as tungsten.

US Pat. No. 5,300,009 discloses a radiation shutter that blocks a radiation beam. The radiation shutter alternately switches between blocking and emitting radiation. The radiation shutter has a shielding plate for blocking a radiation beam and a solenoid mechanism for advancing and retracting the shielding plate with respect to the optical path of the radiation beam. A solenoid mechanism can switch back and forth between blocking and emitting radiation. A solenoid mechanism generates a driving force by a magnetic force generated in an iron core due to a magnetic field of a coil.

JP-A-5-264795

A charged particle beam generator may have a driving mechanism using a magnetic field of a coil as in Patent Document 1. A charged particle beam is affected by a magnetic field because it is charged. The charged particle beam is emitted along the emission axis. However, if a magnetic field exists in the region containing the emission axis, the charged particle beam is affected by the magnetic field. As a result, the charged particle beam deviates from the emission axis.

Accordingly, the present invention provides a charged particle beam generator capable of irradiating a desired position with a charged particle beam.

A charged particle beam generator according to one aspect of the present invention includes a charged particle beam source that emits a charged particle beam along an emission axis, a first magnetic field generator that generates a first magnetic field, and a second magnetic field. and a second magnetic field generator. The first magnetic field generator and the second magnetic field generator are separated from each other along a direction intersecting the emission axis. The emission axis is arranged between the first magnetic field generator and the second magnetic field generator. The first magnetic pole direction from the N pole to the S pole of the first magnetic field generator is opposite to the second magnetic pole direction from the N pole to the S pole of the second magnetic field generator.

In the charged particle beam generator, the first magnetic pole direction of the first magnetic field generator is opposite to the second magnetic pole direction of the second magnetic field generator. According to this configuration, a synthetic magnetic field is generated between the first magnetic field generator and the second magnetic field generator. When such a composite magnetic field occurs, regions of relatively low magnetic flux density are formed. As a result, when the emission axis is overlapped in a region where the magnetic flux density is relatively low, the charged particle beam emitted from the charged particle beam source is affected by the magnetic field of the first magnetic field generator and the magnetic field of the second magnetic field generator. Suppressed. Therefore, a desired position can be irradiated with the charged particle beam.

In one form of the charged particle beam generator, the first magnetic pole direction may be parallel to the second magnetic pole direction. When viewed from a direction intersecting the emission axis, the first magnetic pole direction and the second magnetic pole direction may extend in a direction intersecting the direction of the emission axis. According to this configuration, a region having a relatively low magnetic flux density can be preferably formed between the first magnetic field generating section and the second magnetic field generating section.

Between the first magnetic field generator and the second magnetic field generator of one form of charged particle beam generator, a magnetic field indicated by magnetic lines of force passing through both the first magnetic field generator and the second magnetic field generator is formed. , and a magnetic field deflection unit that biases the distribution of the magnetic lines of force in the direction of the first magnetic pole. According to the magnetic deflection section, a synthetic magnetic field is formed indicated by magnetic lines of force passing through both the first magnetic field generating section and the second magnetic field generating section. The magnetic field deflector deflects the lines of magnetic force. Regions of relatively low magnetic flux density respond to a resultant magnetic field as indicated by the distribution of magnetic field lines. As a result, the position where the region with relatively low magnetic flux density is formed changes according to the bias of the magnetic lines of force. Therefore, it becomes possible to form a region with a relatively low magnetic flux density at a desired position.

The magnetic field deflection section of the charged particle beam generator of one form may be a magnetic member formed of a magnetic material and extending from the first magnetic field generation section to the second magnetic field generation section. According to this configuration, the magnetic member forms a region with a higher magnetic permeability than air. As a result, the distribution of the lines of magnetic force existing between the first magnetic field generating section and the second magnetic field generating section positively passes through the magnetic member, and thus is biased. Therefore, it becomes possible to form a region with a relatively low magnetic flux density at a desired position.

The magnetic field deflection unit of the charged particle beam generator of one form is spaced apart from the first magnetic field generation unit and the second magnetic field generation unit in the first magnetic pole direction or the second magnetic pole direction, and the first magnetic field generation unit and the second magnetic field generation unit It may be a third magnetic field generating section arranged between the sections. According to this configuration, the number of magnetic lines of force passing through the third magnetic field generator among the magnetic lines of force existing between the first magnetic field generator and the second magnetic field generator changes according to the action of the third magnetic field generator. . As a result, the lines of magnetic force are biased, making it possible to form a region with a relatively low magnetic flux density at a desired position.

A first magnetic field generation unit of a charged particle beam generator of one form may have a first coil that generates a first magnetic field and a first driving member that moves according to a force caused by the first magnetic field. good. The second magnetic field generator may have a second coil that generates the second magnetic field, and a second drive member that moves according to force caused by the second magnetic field. According to this configuration, the first magnetic field generation section and the second magnetic field generation section generate a synthetic magnetic field between the first magnetic field generation section and the second magnetic field generation section, and apply a force for driving the object. Acts as an actuator to generate

A first magnetic field generation unit of a charged particle beam generator of one form may have a first coil that generates a first magnetic field and a first driving member that moves according to a force caused by the first magnetic field. good. The second magnetic field generator may have a second coil that generates the second magnetic field. According to this configuration, the first magnetic field generation section and the second magnetic field generation section generate a composite magnetic field between the first magnetic field generation section and the second magnetic field generation section, and the first magnetic field generation section It functions as an actuator that generates a force to drive the

A shielding member that can overlap with the emission axis may be attached to the first driving member of the charged particle beam generator of one form. The first magnetic field generating section may switch between a shielding mode in which the shielding member overlaps the emission axis and an emission mode in which the shielding member does not overlap the emission axis by the operation of the first driving member. According to this configuration, while the charged particle beam is emitted from the charged particle beam source, the charged particle beam or another radiation caused by the charged particle beam can be switched between emission and shielding.

ADVANTAGE OF THE INVENTION According to this invention, the charged particle beam generator which can irradiate a charged particle beam to a desired position is provided.

FIG. 1 is a perspective view showing the appearance of an X-ray module provided with an X-ray tube. FIG. 2 is a cross-sectional view showing the inside of the X-ray tube. FIG. 3 is a perspective view showing the X-ray shutter of the first embodiment; FIG. FIG. 4A is a diagram for explaining the effect of a thin magnetic shield. FIG. 4B is a diagram for explaining the effect of a thick magnetic shield. FIG. 5 is a perspective view showing the structure of a solenoid included in the X-ray shutter of the first embodiment. FIG. 6A is a diagram showing magnetic lines of force that form a magnetic field formed by a pair of solenoids. FIG. 6(b) is a diagram showing another magnetic field formed by a pair of solenoids by magnetic lines of force. FIG. 7(a) is a contour diagram showing the distribution of the magnetic flux density in the magnetic field indicated by the magnetic lines of force in FIG. 6(a). FIG. 7(b) is a contour diagram showing the distribution of the magnetic flux density in the magnetic field indicated by the magnetic lines of force in FIG. 6(b). FIG. 8 is a perspective view showing paths of magnetic lines of force and electron beams shown in FIG. 6(a). FIG. 9 is a perspective view showing another path of magnetic lines of force and electron beams shown in FIG. 6(b). FIG. 10 is a diagram visualizing magnetic lines of force formed around the X-ray shutter of the first embodiment. FIG. 11 is a contour diagram showing the distribution of magnetic flux density in the magnetic field indicated by the magnetic field lines of FIG. FIG. 12 is a perspective view showing paths of magnetic lines of force and electron beams shown in FIG. FIG. 13 is a diagram showing the X-ray shutter of the second embodiment and the magnetic field formed around the X-ray shutter by magnetic lines of force. FIG. 14 is a diagram showing the X-ray shutter of the third embodiment and the magnetic field formed around the X-ray shutter by magnetic lines of force. FIG. 15(a) is a diagram showing the X-ray shutter of the first modified example. FIGS. 15(b) and 15(c) are diagrams showing the X-ray shutter of the second modified example. FIG. 16 is a diagram showing an X-ray shutter of a third modified example.

<First embodiment>
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted.

The X-ray module 100 (charged particle beam generator) shown in FIG. 1 is a so-called microfocus X-ray source. The X-ray module 100 is used, for example, for X-ray nondestructive inspection for observing the internal structure of a subject. The X-ray module 100 has an X-ray tube 110, a housing 120, and a power supply (not shown). X-ray tube 110 is housed inside housing 120 . The inside of housing 120 is filled with insulating oil. A power supply is located below the housing 120 . The power supply supplies power to the X-ray tube 110 via the power supply section 141 (see FIG. 2). X-ray tube 110 emits X-rays from exit window 112 .

The X-ray module 100 realizes switching between X-ray emission and stop by a physical shield. The X-ray module 100 switches between a mode in which the exit window 112 is covered to block the emission of X-rays and a mode in which the exit window 112 is opened to emit the X-rays by means of the X-ray shutter 10, which will be described later. As a result, the X-ray module 100 becomes capable of so-called pulse operation. For example, the X-ray module 100 performs an operation of emitting X-rays only when capturing an X-ray image and an operation of not emitting X-rays when not capturing an X-ray image, such as when an object is being transported, for a short period of time. can be switched with With such a configuration, X-ray emission and stoppage from the X-ray tube 110 can be realized without controlling the current supply from the power supply. As a result, sophisticated electrical circuit design for current control is not required.

The X-ray tube 110 shown in FIG. 2 includes a target 111 and an electron gun 4 (charged particle beam source) housed in an internal space (vacuum space SV) of a vacuum housing 1 having an insulating valve 2 and a metal housing 3. ) and The electron gun 4 irradiates the target 111 with an electron beam EB, which is a charged particle beam. The target 111 receiving the electron beam EB generates X-rays. The generated X-rays pass through the exit window 112 and are taken out of the X-ray tube 110 in the direction along the incident direction of the electron beam EB. That is, the X-ray tube 110 is of a transmissive type.

The exit window 112 is attached so as to seal the opening of the metal housing 3 . The exit window 112 is a substrate made of a material having good X-ray transparency, such as beryllium or diamond. The target 111 is arranged on the surface of the emission window 112 on the vacuum space SV side, and intersects the emission axis AE of the electron beam EB. The target 111 is, for example, a tungsten thin film formed on the vacuum side surface of the exit window 112 .

The electron gun 4 receives power from a power source and generates an electron beam EB. The electron gun 4 has a heater 4a, a cathode 4b, and grid electrodes 4c and 4d. The heater 4a generates heat by being supplied with electric power. Cathode 4b is heated by heater 4a. The heated cathode 4b emits electrons. Grid electrodes 4c and 4d adjust the amount and trajectory of emitted electrons. The potential of the target 111 is the ground potential (GND).

The X-ray module 100 further has an X-ray shutter 10 shown in FIG. The X-ray shutter 10 can shield X-rays emitted from the X-ray tube 110 . Also, the X-ray shutter 10 may not shield the X-rays emitted by the X-ray tube 110 . The operation of switching between X-ray emission and shielding is referred to as pulse operation. The x-ray shutter 10 allows pulsed operation of the x-ray module 100 . The X-ray shutter 10 has a shutter frame 20 , actuators 30A and 30B, and a magnetic bypass 40 .

The shutter frame 20 irradiates the subject with X-rays by exposing the exit window 112 toward the subject. Also, the shutter frame 20 is arranged between the exit window 112 and the object to stop irradiation of the object with X-rays. The switching of the position of the shutter frame 20 is performed by actuators 30A and 30B. The shutter frame 20 has a shielding plate 21 (shielding member) and shielding beams 22 . The shield plate 21 shields X-rays. The shield plate 21 is a rectangular or circular flat plate. The shield beam 22 connects the shield plate 21 to the actuators 30A, 30B. The shield beam 22 includes a connecting portion 22a and a connecting portion 22b. One end of the connecting portion 22a is fixed to the actuators 30A and 30B. The other end of the connecting portion 22a is connected to the connecting portion 22b. The connecting portions 22a are connected to both ends of the connecting portion 22b. The connecting portion 22b is slightly separated from the exit window 112 and the upper surface of the housing 120. As shown in FIG. A shielding plate 21 is attached to the central portion of the connecting portion 22b. In addition, when the connecting portion 22 b has a width sufficient to cover the emission window 112 , the connecting portion 22 b can also function as the shielding plate 21 . Therefore, in this case, the shield plate 21 may be omitted.

Actuators 30A and 30B generate driving force for switching the position of shutter frame 20 . The X-ray shutter 10 has two actuators 30A and 30B. The actuators 30A and 30B are arranged along the diameter direction of the housing 120 so as to sandwich the X-ray tube 110 therebetween. The actuators 30A, 30B have magnetic shields 31A, 31B and solenoids 50A, 50B.

The magnetic shields 31A, 31B are housings that accommodate the solenoids 50A, 50B. In FIG. 3, rectangular parallelepiped magnetic shields 31A and 31B are illustrated, but the shape of the magnetic shields 31A and 31B is not particularly limited. For example, one magnetic shield 31A accommodates one or more solenoids 50A. Magnetic shields 31A, 31B physically protect solenoids 50A, 50B. Also, the magnetic shields 31A and 31B suppress leakage of magnetic fields generated by the solenoids 50A and 50B. The effect of suppressing magnetic field leakage is determined by the thickness of the magnetic shields 31A and 31B. For example, as shown in FIG. 4A, when the thickness of the magnetic shield 31A is thin, the effect of suppressing magnetic field leakage is small. As shown in FIG. 4B, when the thickness of the magnetic shield 31A is large, the effect of suppressing magnetic field leakage is great. From the viewpoint of magnetic field leakage, it is desirable that the thickness of the magnetic shields 31A and 31B be thicker. However, other factors may limit the thickness of the magnetic shields 31A and 31B. The actuators 30A and 30B of the present embodiment solve the problem of magnetic field leakage by another technique, which will be described later. Therefore, the magnetic shields 31A, 31B may be treated as further suppressing the strength of the magnetic field reduced by another technique. That is, the thickness of the magnetic shields 31A and 31B may be determined from a viewpoint different from the leakage of the magnetic field of the magnetic shields 31A and 31B. Further, in some cases, the actuators 30A, 30B may omit the magnetic shields 31A, 31B.

A solenoid 50A shown in FIG. 5 generates a driving force. The direction of the drive force (drive axis AD) extends perpendicular to the exit axis AE. According to this direction, it is possible to switch between a position where the shielding plate 21 overlaps the emission axis AE and a position where the shielding plate 21 does not overlap the emission axis AE. The solenoid 50</b>A has a coil 51 , a fixed magnetic pole 52 , a movable magnetic pole 53 (first drive member), a spring 54 and a housing 55 .

The fixed magnetic pole 52 is arranged inside a cylindrical housing 55 . Note that the fixed magnetic pole 52 may be a magnetic member that does not generate a magnetic field. A fixed magnetic pole 52 closes one open end of a housing 55 . The fixed magnetic pole 52 is fixed with respect to the housing 55 . Therefore, the fixed magnetic pole 52 does not move relative to the housing 55 .

The coil 51 is arranged inside the housing 55 . The coil 51 is provided from the fixed magnetic pole 52 to the other open end of the housing 55 . That is, the coil 51 is a solenoid in a narrow sense. The coil 51 is fixed with respect to the housing 55 as is the fixed magnetic pole 52 . Therefore, the coil 51 also does not move relative to the housing 55 .

Coil 51 has a coil axis AC oriented in a predetermined direction. The coil axis AC may be the central axis of the cylindrical coil 51 . The arrangement of the coils 51 can be defined by using the coil axis AC. Coil axis AC extends in a direction perpendicular to output axis AE. The coil axis AC of one (solenoid 50A) is parallel to the coil axis AC of the other (solenoid 50B). Further, assume a virtual plane orthogonal to the exit axis AE. One coil axis AC and the other coil axis AC are included in the imaginary plane. The direction of the coil axis AC also coincides with the drive axis AD along which the movable magnetic pole 53, which will be described later, reciprocates. Therefore, in some of the explanations above, the coil axis AC may be read as the drive axis AD of the movable magnetic pole 53 .

The movable magnetic pole 53 has an insertion portion located inside the coil 51 and an exposed portion located outside the coil 51 . That is, one end of the movable magnetic pole 53 is inserted into the coil 51 . The other end of the movable magnetic pole 53 protrudes from the coil 51 . A flange 56 is fixed to the movable magnetic pole 53 . A spring 54 is arranged between the flange 56 and the housing 55 . Spring 54 is a compression spring. The length from the housing 55 to the flange 56 is shorter than the natural length of the spring 54 when the movable pole 53 protrudes most from the housing 55 . That is, spring 54 is compressed. A connecting portion 22 a is fixed to the end of the exposed portion of the movable magnetic pole 53 .

The movable magnetic pole 53 is not fixed with respect to the coil 51 . Therefore, the movable magnetic pole 53 can move relative to the coil 51 . Similarly, the movable magnetic pole 53 can also move relative to the fixed magnetic pole 52 . When current is supplied to the coil 51, the coil 51 generates a magnetic field. Since the movable magnetic pole 53 is inserted into the coil 51 , it is magnetized by the magnetic field generated by the coil 51 . As a result, a mutually attractive force is generated between the movable magnetic pole 53 and the fixed magnetic pole 52 . This force causes the movable magnetic pole 53 to move. For example, the movable pole 53 can move toward the fixed pole 52 . Conversely, when no current is supplied to the coil 51 , the coil 51 does not generate a magnetic field, and the movable magnetic pole 53 is moved away from the fixed magnetic pole 52 by the spring 54 . That is, the movable magnetic pole 53 linearly reciprocates along the drive axis AD.

When the solenoid 50A is in a state where the coil 51 is not supplied with current, the movable magnetic pole 53 has the longest protrusion length. When the coil 51 is not supplied with current, the movable magnetic pole 53 is biased by the spring 54 . Compressed spring 54 tends to increase the distance between housing 55 and flange 56 . Therefore, the movable magnetic pole 53 is in the most projected state. On the other hand, when a current is supplied to the coil 51, the coil 51 generates a magnetic field. The movable magnetic pole 53 is magnetized according to this magnetic field. As a result, the magnetized movable magnetic pole 53 is pulled by the fixed magnetic pole 52 . Since this pulling force is stronger than the force of the spring 54 , the projecting length of the movable magnetic pole 53 is minimized against the force of the spring 54 .

By the way, from the viewpoint of operating the shielding plate 21, the solenoid 50A should just generate the force to operate the shielding plate 21. FIG. In other words, from the viewpoint of operating the shielding plate 21, it is not necessary to consider the influence of the magnetic field generated when the coil 51 is supplied with current. However, from the viewpoint of the electron beam EB, if there is a magnetic field in the traveling region of the electrons, the traveling electrons may receive Lorentz force. In other words, the trajectory of electrons when the X-ray shutter 10 is operating may differ from the trajectory of electrons when the X-ray shutter 10 is not operating.

As an example of the operation, the X-ray shutter 10 is in the shielding state when the projection length is the longest, and is in the irradiation state when the projection length is the shortest. In this case, when no current is supplied to the coil 51, the shielding state occurs, and when the coil 51 is supplied with current, the irradiation state occurs. Then, in the shielding state, the coil 51 does not generate a magnetic field, but in the irradiation state, the coil 51 generates a magnetic field. Therefore, the electron beam EB may be affected by the magnetic field when in an irradiation state.

As another example of operation, the X-ray shutter 10 is in the irradiation state when the projection length is the longest, and is in the shielding state when the projection length is the shortest. In this case, when no current is supplied to the coil 51, the illumination state is established, and when the coil 51 is supplied with the current, the shield state is established. Then, the coil 51 does not generate a magnetic field in the irradiation state, but the coil 51 generates a magnetic field in the shielding state.

The above operational illustration focuses on one solenoid 50A. The X-ray shutter 10 has two solenoids 50A and 50B. That is, when the X-ray shutter 10 operates, a magnetic field caused by the coil 51 of one solenoid 50A and a magnetic field caused by the coil 51 of the other solenoid 50B are generated. The magnetic field at this time is indicated by the lines of magnetic force shown in FIG. 6(a) or the lines of magnetic force shown in FIG. 6(b). The difference in these magnetic fields is due to the relationship between the direction of the magnetic field generated by the coil 51 (first coil) of one solenoid 50A and the direction of the magnetic field generated by the coil 51 (second coil) of the other solenoid 50B. do. In addition to the coil 51, the solenoids 50A and 50B can generate magnetic fields from the fixed magnetic poles 52 as well. Therefore, the magnetic fields generated by the parts constituting the solenoids 50A and 50B are collectively referred to as the magnetic fields generated by the solenoids 50A and 50B.

The magnetic field indicated by the magnetic field lines in FIG. 6(a) is generated when the direction of the magnetic field of one solenoid 50A is the same as the direction of the magnetic field of the other solenoid 50B. For example, when the solenoid 50A to which the current is applied is viewed as a magnet, one end 50A1 of the solenoid 50A is N pole and the other end 50A2 is S pole. Also, when the other solenoid 50B to which the current is applied is viewed as a magnet, it is assumed that the end 50B1 of the other solenoid 50B is the N pole and the opposite end 50B2 is the S pole. In the solenoid 50A, the magnetic pole direction SA from the N pole to the S pole matches the magnetic pole direction SB from the N pole to the S pole of the other solenoid 50B. When the magnetic field generated by this configuration is represented by magnetic field lines, there are no magnetic field lines that pass through both the one solenoid 50A and the other solenoid 50B.

The magnetic field indicated by the magnetic field lines in FIG. 6(b) is generated when the direction of the magnetic field of one solenoid 50A is opposite to the direction of the magnetic field of the other solenoid 50B. Such a state can be realized by reversing the direction of the current supplied to the solenoid 50A and the direction of the current supplied to the solenoid 50B. Moreover, the directions of the currents are the same, and this can also be realized by reversing the winding direction of the coil 51 of the solenoid 50A and the winding direction of the coil 51 of the solenoid 50B. For example, when the solenoid 50A to which the current is applied is viewed as a magnet, one end 50A1 of the solenoid 50A is N pole and the other end 50A2 is S pole. When the other solenoid 50B to which the current is applied in the opposite direction is viewed as a magnet, the end 50B1 of the other solenoid 50B is S pole and the opposite end 50B2 is N pole. The magnetic pole direction SA (first magnetic pole direction) from the N pole to the S pole in one solenoid 50A does not match the magnetic pole direction SB (second magnetic pole direction) from the N pole to the S pole in the other solenoid 50B. In other words, the magnetic pole direction SA of one solenoid 50A is opposite to the magnetic pole direction SB of the other solenoid 50B. When the magnetic field produced by this configuration is represented by magnetic field lines, there are magnetic field lines that pass through both solenoid 50A on the one hand and solenoid 50B on the other.

The difference in the magnetic fields shown in FIGS. 6(a) and 6(b) also causes a difference in the magnetic flux density distribution. FIG. 7(a) shows the distribution of magnetic flux density in the magnetic field indicated by the field lines of FIG. 6(a). In FIG. 7(a), which is a contour diagram, hatching with wide intervals indicates that the magnetic flux density is relatively high. Closely spaced hatching indicates relatively low magnetic flux density. For example, region S2 is the region with the highest magnetic flux density. Region S3 is the region with the lowest magnetic flux density.

FIG. 7(b) shows the distribution of magnetic flux density in the magnetic field indicated by the field lines of FIG. 6(b). From this contour diagram, it can be seen that a region S3A with a relatively low magnetic flux density is formed in the region S1 sandwiched between the solenoids 50A and 50B. This relatively low magnetic flux density area is called a "low magnetic flux density area SL". The low magnetic flux density area SL is surrounded by relatively high magnetic flux density areas. Also, as can be seen from the region S3 away from the solenoids 50A and 50B, the magnetic flux density decreases as the distance from the solenoids 50A and 50B increases. However, the distance from the solenoids 50A, 50B to the low magnetic flux density region SL is shorter than the distance from the solenoids 50A, 50B to the region S3. In other words, it is considered that the low magnetic flux density region SL is caused by interference between the magnetic field of one solenoid 50A and the magnetic field of the other solenoid 50B.

Therefore, the present inventors paid attention to this low magnetic flux density region SL. That is, when the solenoids 50A and 50B are operated, the polarities of the solenoids 50A and 50B are reversed to generate the low magnetic flux density region SL. Then, the emission axis AE is overlapped with the low magnetic flux density region SL. By doing so, the influence of the magnetic field on the electron beam EB can be suppressed.

The polarities of the solenoids 50A and 50B can be determined by the direction of current applied to the coil 51. FIG. If the winding direction of the coil 51 of the solenoid 50A and the winding direction of the coil 51 of the solenoid 50B are the same, the direction of the current applied to one solenoid 50A is the same as the current applied to the other solenoid 50B. should be reversed to the direction of In this case, the polarities of the fixed magnetic pole 52 of the solenoid 50A and the fixed magnetic pole 52 of the solenoid 50B are also opposite to each other. For example, even when the coil 51, the movable magnetic pole 53, and the fixed magnetic pole 52 are regarded as one virtual magnet, the polarity of one solenoid 50A can be said to be opposite to the polarity of the other solenoid 50B.

Assuming that the solenoids 50A and 50B have the same configuration and generate the same magnetic fields, the low magnetic flux density region SL is formed in the center of the axis connecting the solenoids 50A and 50B. Therefore, the relative relationship between the positions of the solenoids 50A and 50B and the position of the electron gun 4 is determined in order to overlap the emission axis AE with the low magnetic flux density region SL. For example, as shown in FIG. 8, when the direction of the magnetic field of one solenoid 50A and the direction of the magnetic field of the other solenoid 50B are the same, the low magnetic flux density region SL does not occur. Since a relatively high magnetic flux density region is formed around the emission axis AE, the electron beam EB emitted from the electron gun 4 receives a strong Lorentz force. That is, the traveling path of electrons is deflected. Also, as shown in FIG. 9, when the direction of the magnetic field of one solenoid 50A and the direction of the magnetic field of the other solenoid 50B are opposite, both the solenoids 50A and 50B are placed between the solenoids 50A and 50B. A resultant magnetic field FM is formed, indicated by the field lines passing through it. A low magnetic flux density region SL is formed by the synthetic magnetic field FM indicated by the magnetic lines of force. However, even if the low magnetic flux density area SL is formed, the electron beam EB emitted from the electron gun 4 receives a strong Lorentz force if the emission axis AE does not overlap the low magnetic flux density area SL. That is, the traveling path of electrons is deflected.

The low magnetic flux density region SL is determined according to the aspect of the synthetic magnetic field FM. Therefore, the inventors came up with the idea of arranging the position of the low magnetic flux density region SL at an arbitrary position by biasing the synthetic magnetic field FM.

As shown in FIG. 10, the X-ray shutter 10 has a magnetic bypass 40 (magnetic member). A magnetic bypass 40 biases the resultant magnetic field FM. The magnetic bypass 40 is made of a material with high magnetic permeability such as iron. For example, the magnetic bypass 40 is an arcuate plate member. The width of the magnetic bypass 40 is approximately the same as the width of the actuators 30A, 30B. The arc center of the magnetic bypass 40 may overlap the exit axis AE. According to the magnetic bypass 40, it is possible to form a region having a magnetic permeability higher than that of air between one solenoid 50A and the other solenoid 50B. FIG. 10 shows that many of the lines of magnetic force directed from the solenoid 50A to the solenoid 50B pass through the magnetic bypass 40 with high magnetic permeability. Placing the magnetic bypass 40 introduces a bias in the resultant magnetic field FM. As shown in FIG. 11, the position of the low magnetic flux density region SL is also biased according to the bias of the synthetic magnetic field FM. With the magnetic bypass 40, the low magnetic flux density region SL can be formed at a desired position, so the positions of the solenoids 50A and 50B and the position of the electron gun 4 can be determined independently of each other. As a result, as shown in FIG. 12, since the emission axis AE overlaps the low magnetic flux density region SL, the electrons emitted from the electron gun 4 are less susceptible to the magnetic field. In other words, deflection of the traveling path of electrons is suppressed.

In short, the X-ray module 100 includes an electron gun 4 that emits an electron beam EB along an emission axis AE, and solenoids 50A and 50B that generate magnetic fields. The solenoids 50A and 50B are arranged so as to be spaced apart from each other along an arrangement direction D that intersects with the emission axis AE. The electron gun 4 is arranged such that the emission axis AE is positioned between the solenoids 50A and 50B. The magnetic pole direction SA of one solenoid 50A is parallel to the magnetic pole direction SB of the other solenoid 50B. Viewed from the arrangement direction D, the magnetic pole directions SA, SB intersect the emission axis AE. The magnetic pole direction SA is opposite to the magnetic pole direction SB.

In the X-ray module 100, the magnetic pole direction SA is opposite to the magnetic pole direction SB. According to this configuration, a low magnetic flux density region SL having a relatively low magnetic flux density is formed between one solenoid 50A and the other solenoid 50B. As a result, when the emission axis AE overlaps the low magnetic flux density region SL, the influence of the magnetic field of the solenoids 50A and 50B on the electron beam EB emitted from the electron gun 4 is suppressed. Therefore, a desired position can be irradiated with the electron beam EB.

A synthetic magnetic field FM is generated between one solenoid 50A and the other solenoid 50B of the X-ray module 100 . The X-ray module 100 further comprises a magnetic bypass 40 that biases the distribution of the resultant magnetic field FM. According to this magnetic bypass 40, the synthetic magnetic field FM formed by mutual interference between the magnetic field of one solenoid 50A and the magnetic field of the other solenoid 50B is biased. Since the low magnetic flux density region SL depends on the distribution of the synthetic magnetic field FM, the position where the low magnetic flux density region SL is formed changes according to the bias of the synthetic magnetic field FM. Therefore, it becomes possible to form the low magnetic flux density region SL at a desired position.

The magnetic bypass 40 of the X-ray module 100 is a flat plate member formed of a plate-shaped magnetic material from one solenoid 50A to the other solenoid 50B. According to this configuration, since the magnetic bypass 40 forms a region with high magnetic permeability, the distribution of the lines of magnetic force existing between the one solenoid 50A and the other solenoid 50B is biased. Therefore, it becomes possible to form the low magnetic flux density region SL at a desired position.

Solenoids 50A and 50B of X-ray module 100 have coils 51 and movable magnetic poles 53 . According to this configuration, the solenoids 50A and 50B generate a synthetic magnetic field FM between the solenoids 50A and 50B and function as an actuator that generates a force for driving the object.

The movable magnetic pole 53 of the X-ray module 100 is attached with a shielding plate 21 that can overlap with the emission axis AE. One solenoid 50A switches between a shielding mode in which the shielding plate 21 overlaps the emission axis AE and an emission mode in which the shielding plate 21 does not overlap the emission axis AE by operating the movable magnetic pole 53 . According to this configuration, it is possible to alternately switch between emission and shielding of X-rays from the X-ray module 100 while the electron beam EB is emitted from the electron gun 4 .

<Second embodiment>
In the first embodiment, the magnetic bypass 40 deflects the synthetic magnetic field FM generated by the solenoids 50A and 50B. Deflection of the magnetic field can also be achieved by different configurations than the magnetic bypass 40 . As shown in FIG. 13, the X-ray module 100A of the second embodiment has an X-ray shutter 10A. The X-ray shutter 10A of the second embodiment has a shutter frame 20, actuators 30A and 30B, and an electromagnet 60 (third magnetic field generator). Since the shutter frame 20 and the actuators 30A and 30B are the same as those in the first embodiment, detailed description thereof will be omitted.

Electromagnet 60 is arranged between solenoids 50A and 50B. The term "between the solenoids 50A and 50B" as used herein includes not only the region S1 sandwiched between the solenoids 50A and 50B but also the region S4 not sandwiched between the solenoids 50A and 50B. Further, the electromagnet 60 is spaced apart from the solenoids 50A, 50B along the coil axes AC1, AC2. The distance from the solenoids 50A, 50B to the electromagnet 60 along the coil axes AC1, AC2 may be set appropriately. However, the emission axis AE is arranged at least in the area surrounded by the electromagnet 60 and the solenoids 50A and 50B. Electromagnet 60 includes a coil. The coil axis AC3 of the electromagnet 60 intersects the coil axis AC1 of one solenoid 50A. For example, the coil axis AC3 of the electromagnet 60 extends perpendicular to the coil axis AC1 of one solenoid 50A. Of the magnetic lines of force directed from one solenoid 50A to the other solenoid 50B, the number of magnetic lines of force passing through the electromagnet 60 differs depending on whether the coil of the electromagnet 60 is energized or not. Applying current to the coils of electromagnet 60 increases the number of magnetic field lines passing through electromagnet 60 . Since the number of magnetic lines of force is conserved, an increase in the number of magnetic lines of force passing through the electromagnet 60 causes a bias in the magnetic field.

When the current applied to the coils of electromagnet 60 is large, the number of magnetic lines of force passing through electromagnet 60 is large. That is, the deviation of the magnetic field is large. As a result, low magnetic flux density region SL is formed at a position close to electromagnet 60 . When the current applied to the coils of electromagnet 60 is small, the number of magnetic lines of force passing through electromagnet 60 is small. That is, the deviation of the magnetic field is small. As a result, low magnetic flux density region SL is formed at a position far from electromagnet 60 . In short, the position of the low magnetic flux density region SL can be controlled by the magnitude of the current applied to the coil of the electromagnet 60 .

In short, the magnetic field deflection portion of the X-ray module 100A is the electromagnet 60 spaced from the solenoids 50A, 50B in the direction of the coil axes AC1, AC2 and disposed between the solenoids 50A, 50B. According to this configuration, the number of magnetic force lines passing through the electromagnet 60 among the magnetic force lines existing between the solenoids 50A and 50B can be changed according to the action of the electromagnet 60. FIG. As a result, the synthetic magnetic field FM is biased, making it possible to form the low magnetic flux density region SL at a desired position.

In addition, in the X-ray shutter 10A of the second embodiment, the other solenoid 50B may be replaced with a mere electromagnet. That is, in this case, the drive source for driving the shutter frame 20 is only one solenoid 50A. The X-ray shutter 10A may be configured with one solenoid 50A and two electromagnets if a desired operation of the shutter frame 20 can be realized with the driving force of one solenoid 50A.

In short, the X-ray module 100A has a solenoid 50A having a coil 51 and a movable magnetic pole 53 as a first magnetic field generator. Furthermore, the X-ray module 100A has an electromagnet including a coil as a second magnetic field generator. According to this configuration, the first magnetic field generator functions as an actuator that generates force for driving the object.

<Third Embodiment>
In the first embodiment and the second embodiment, a configuration is adopted in which the magnetic field is positively biased. As shown in FIG. 14, the X-ray module 100B of the third embodiment employs a configuration in which the emission axis AE overlaps the low magnetic flux density region SL by arranging the solenoids 50A and 50B and the electron gun 4 . That is, the X-ray shutter 10B of the third embodiment does not include the magnetic bypass 40 and the electromagnet 60.

The X-ray shutter 10B of the third embodiment has a shutter frame 20B and actuators 30A and 30B. Since the actuators 30A and 30B are the same as those in the first embodiment, detailed description thereof will be omitted. The shutter frame 20B of the third embodiment differs from the shutter frame 20 of the first embodiment in the shape of the connecting portion 22b. The low magnetic flux density region SL in the third embodiment is formed in the region S1 sandwiched between the solenoids 50A and 50B. The electron gun 4 is also formed in a region S1 sandwiched between the solenoids 50A and 50B when viewed from the direction of the emission axis AE. Accordingly, the connecting portion 22b also includes a portion arranged in the region S1 sandwiched between the solenoids 50A and 50B.

According to the configuration of the third embodiment, the X-ray shutter 10B does not include the magnetic bypass 40 and the electromagnet 60 as the magnetic field deflector. Therefore, the configuration can be simplified.

The present invention is not limited to the first, second and third embodiments described above.

<First modification>
For example, as shown in FIG. 15(a), an X-ray shutter 10C included in an X-ray module 100C of the first modified example may have four solenoids 50A, 50B, 50C and 50D. The coil axis AC3 of the added one solenoid 50C overlaps with the coil axis AC1 of the one solenoid 50A. In this case, the solenoids 50A, 50C can also be regarded as one virtual magnet. Similarly, the coil axis AC4 of the other added solenoid 50D overlaps the coil axis AC2 of the other solenoid 50B. In this case, the solenoids 50B and 50D can also be regarded as one virtual magnet. The shutter frame 20C is connected to each of four solenoids 50A, 50B, 50C and 50D. According to the X-ray shutter 10C of the first modified example, one shutter frame 20C can be driven by four solenoids 50A, 50B, 50C, and 50D.

<Second modification>
For example, as shown in FIGS. 15(b) and 15(c), the X-ray shutter 10D included in the X-ray module 100D of the second modified example also has four solenoids 50A, 50B, 50C and 50D. In the second modification, the coil axis AC3 of the added one solenoid 50C is parallel to the coil axis AC1 of the one solenoid 50A. In this case, the direction of the magnetic field of one solenoid 50A and the direction of the magnetic field of the additional solenoid 50C may be the same or different. The coil axis AC3 of the other added solenoid 50D is parallel to the coil axis AC2 of the other solenoid 50B. Also in this case, the direction of the magnetic field of the other solenoid 50B and the direction of the magnetic field of the other solenoid 50D to be added may be the same or different.

In FIG. 15B, the magnetic pole direction SA of the solenoid 50A and the magnetic pole direction SC of the solenoid 50C are the same. Similarly, the magnetic pole direction SB of the solenoid 50B and the magnetic pole direction SC of the solenoid 50D are the same. Even if the directions of the magnetic fields of the solenoids 50A and 50C on one side are the same and the directions of the magnetic fields of the solenoids 50B and 50D on the other side are the same, the directions of the magnetic fields of the solenoids 50A and 50C on the one side are the same. , and the directions of the magnetic fields of the solenoids 50B and 50D on the other side are opposite.

Further, as shown in FIG. 15(c), the magnetic pole direction SA of the solenoid 50A and the magnetic pole direction SC of the solenoid 50C are opposite to each other. Similarly, the magnetic pole direction SB of the solenoid 50B and the magnetic pole direction SC of the solenoid 50D are opposite to each other. When the directions of the magnetic fields of the solenoids 50A and 50C on one side are opposite to each other and the directions of the magnetic fields of the solenoids 50B and 50D on the other side are opposite to each other, the magnetic fields of the solenoids 50A and 50B arranged inside The directions are opposite to each other. Similarly, the directions of the magnetic fields of the solenoids 50C and 50D located outside are opposite to each other.

The added solenoids 50C and 50D may be connected to the shutter frame 20 as shown in FIG. 15(b) or may not be connected as shown in FIG. 15(c).

<Third modification>
The X-ray shutter 10 of the first embodiment had one magnetic bypass 40 . The number of magnetic bypasses 40 that the X-ray shutter 10 has is not limited to one. As shown in FIG. 16, the X-ray shutter 10E of the X-ray module 100E of the third modified example has two magnetic bypasses 40A and 40B. An additional magnetic bypass 40B is arranged to couple the fixed magnetic pole 52 of one solenoid 50A to the fixed magnetic pole 52 of the other solenoid 50B. Further, the planar shape of the added magnetic bypass 40B is different from the planar shape of the magnetic bypass 40A. In the illustration of FIG. 16, the width of the added magnetic bypass 40B is narrower than the width of the magnetic bypass 40A. That is, the high-permeability region formed by the added magnetic bypass 40B is different from the high-permeability region formed by the magnetic bypass 40A. The direction in which the added magnetic bypass 40B moves the low magnetic flux density region SL is opposite to the direction in which the magnetic bypass 40A moves the low magnetic flux density region SL. Therefore, the two magnetic bypasses 40A and 40B make it possible to set the position of the low magnetic flux density region SL more precisely.

In the above embodiments and modified examples, the shutter frame 20 is exemplified as the object to be driven. An object to be driven is not limited to the shutter frame 20 . The forces generated by the magnetic field generator may be used to physically drive various components required for desired operation of the x-ray module 100 . Further, although the X-ray module 100 is exemplified in the above-described embodiment and modification, the X-ray tube 110 may be replaced with an electron beam module using an electron beam source that extracts the electron beam EB as it is.

DESCRIPTION OF SYMBOLS 1... Vacuum housing, 2... Insulation valve, 3... Metal housing, 4... Electron gun (charged particle beam source), 10... X-ray shutter, 20... Shutter frame, 21... Shielding plate, 22... Shielding beam, 30A , 30B... actuator, 31A, 31B... magnetic shield, 40... magnetic bypass (magnetic member), 50A, 50B... solenoid, 51... coil, 52... fixed magnetic pole, 53... movable magnetic pole, 60... electromagnet, 100... X-ray module (Charged particle beam generator), AC... Coil axis line, AE... Emission axis line, D... Arrangement direction, EB... Electron beam, FM... Synthetic magnetic field, SL... Low magnetic flux density region.

Claims (8)

a charged particle beam source that emits a charged particle beam along an emission axis;
a first magnetic field generator that generates a first magnetic field;
a second magnetic field generator for generating a second magnetic field,
the first magnetic field generator and the second magnetic field generator are spaced apart from each other along a direction intersecting the emission axis;
the emission axis is arranged between the first magnetic field generator and the second magnetic field generator;
A charged particle beam generator, wherein a first magnetic pole direction from the N pole to the S pole of the first magnetic field generation section is opposite to a second magnetic pole direction from the N pole to the S pole of the second magnetic field generation section. . the first magnetic pole direction is parallel to the second magnetic pole direction;
2. The charged particle beam generator according to claim 1, wherein said first magnetic pole direction and said second magnetic pole direction extend in a direction crossing said emission axis when viewed from a direction intersecting said emission axis. between the first magnetic field generating section and the second magnetic field generating section, a magnetic field indicated by magnetic lines of force passing through both the first magnetic field generating section and the second magnetic field generating section is formed;
The charged particle beam generator according to claim 1 or 2, further comprising a magnetic field deflector that deflects the distribution of the magnetic lines of force in the direction of the first magnetic pole. 4. The charged particle beam generator according to claim 3, wherein said magnetic field deflection section is a magnetic member formed of a magnetic material and extending from said first magnetic field generation section to said second magnetic field generation section. The magnetic deflection section is spaced apart from the first magnetic field generation section and the second magnetic field generation section in the first magnetic pole direction or the second magnetic pole direction, and is spaced apart from the first magnetic field generation section and the second magnetic field generation section. The charged particle beam generator according to claim 3, which is a third magnetic field generator disposed therebetween. The first magnetic field generator has a first coil that generates the first magnetic field, and a first driving member that moves according to a force caused by the first magnetic field,
6. The second magnetic field generator according to claim 1, further comprising: a second coil for generating the second magnetic field; and a second drive member that moves according to a force caused by the second magnetic field. The charged particle beam generator according to item 1. The first magnetic field generator has a first coil that generates the first magnetic field, and a first driving member that moves according to a force caused by the first magnetic field,
The charged particle beam generator according to any one of claims 1 to 5, wherein said second magnetic field generator has a second coil for generating said second magnetic field. A shielding member that can overlap with the output axis is attached to the first driving member,
wherein the first magnetic field generating unit switches between a shielding mode in which the shielding member overlaps the emission axis and an emission mode in which the shielding member does not overlap the emission axis by operation of the first driving member. Item 8. The charged particle beam generator according to item 6 or 7.

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