Measuring device

Abstract

To obtain a measuring device that can improve measurement accuracy while suppressing the amount of charged particle radiation emitted from a charged particle source. [Solution] The measuring device comprises a radiation unit 20 that houses a charged particle source 21, a detection unit 30 that houses a detection device 31 for detecting charged particle beams emitted from the charged particle source and is positioned at a distance from the radiation unit 20, and a magnetic field generating unit 40 that generates a magnetic field between the radiation unit 20 and the detection unit 30, with the magnetic field generating unit 40 directing from one side of the radiation unit 20 to the other. The radiation unit 20 has an outlet 23a that ejects the charged particle beams emitted from the charged particle source 21 outwards, positioned opposite the detection unit 30, and the detection unit 30 has an inlet 33a that allows the charged particle beams to enter the interior, positioned opposite the outlet 23a.

Description

Technical Field

[0001] The present invention relates to a measuring device.

Background Art

[0002] A measuring device that measures the thickness of a sheet-like object to be measured using a charged particle beam emitted from a charged particle beam source is known (see, for example, Patent Document 1). The measuring device includes a radiation unit that houses a charged particle beam source inside, and a detection unit that houses a detection device for detecting a charged particle beam inside. The radiation unit has an emission port for emitting the charged particle beam emitted from the charged particle beam source to the outside. The detection unit has an incident port for allowing the charged particle beam emitted from the radiation unit to enter inside. The radiation unit and the detection unit are arranged with a space provided between them and with the emission port and the incident port facing each other. The thickness of the object to be measured is measured based on the change in the dose of the charged particle beam detected by the detection unit when the object to be measured is passed between the radiation unit and the detection unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The charged particle beam emitted from the emission port spreads radially while heading toward the incident port. Therefore, a part of the charged particle beam emitted from the emission port does not enter the incident port. The detection unit detects the dose of the charged particle beam that has entered through the incident port.

[0005] If the amount of charged particle beam entering through the incident port is too small, the change in the detected dose becomes small, and the measurement accuracy of the thickness of the object to be measured may become insufficient. Therefore, in order to allow a sufficient amount of charged particle beam to enter through the incident port, it is conceivable to increase the emission amount of the charged particle beam from the charged particle beam source.

[0006] However, as the amount of charged particle radiation emitted from a charged particle source increases, the equipment needs to be larger or require a larger installation space in order to secure a wider controlled area.

[0007] The present invention aims to provide a measuring device that can improve measurement accuracy while suppressing the amount of charged particle radiation emitted from a charged particle source. [Means for solving the problem]

[0008] The measuring device according to the present invention comprises a radiation unit that houses a charged particle source, a detection unit that houses a detection device for detecting charged particle beams emitted from the charged particle source and is positioned at a distance from the radiation unit, and a magnetic field generating unit that generates a magnetic field between the radiation unit and the detection unit, with the magnetic field directed from one side of the radiation unit and the detection unit to the other. The radiation unit has an outlet formed at a position opposite to the detection unit for ejecting charged particle beams emitted from the charged particle source to the outside, and the detection unit has an inlet formed at a position opposite to the outlet for injecting charged particle beams into the interior. [Effects of the Invention]

[0009] According to the present invention, it is possible to obtain a measuring device that can improve measurement accuracy while suppressing the amount of charged particle radiation emitted from a charged particle source. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view showing the schematic configuration of the measuring device according to Embodiment 1. [Figure 2] This is a cross-sectional view obtained by cutting the radiation section and the detection section in a plane that includes the direction in which the object being measured is fed. [Figure 3] This is a cross-sectional view of the radial portion cut along the line III-III shown in Figure 2. [Figure 4] This is a cross-sectional view obtained by cutting the radial portion along the IV-IV line shown in Figure 2. [Figure 5]This diagram shows a modified example of the magnetic field generation section. [Figure 6] This is a diagram showing a measuring device equipped with a shielding section. [Modes for carrying out the invention]

[0011] A measuring device according to one embodiment of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described below.

[0012] [Embodiment 1] <Outline configuration of the measuring device> Figure 1 is a perspective view showing the schematic configuration of a measuring device according to Embodiment 1. The measuring device 1 is a device for measuring the thickness of a sheet-like object to be measured 50. Examples of objects to be measured 50 include electrode sheets and separator sheets for secondary batteries, paper, plastic sheets for packaging, building material sheets, functional material sheets, optical films, and metal foils. For example, if the object to be measured 50 is an electrode sheet, a slurry is thinly and uniformly coated onto the surface of the aluminum foil and dried in the next step. After drying, the same coating is applied to the back surface of the aluminum foil and dried. By measuring the thickness of the electrode sheet using the measuring device 1, the basis weight (coated basis weight) of the aluminum foil is measured.

[0013] The measuring device 1 comprises a frame 10, a radiating unit 20, a detection unit 30, and a magnetic field generating unit 40. The frame 10 has a lower frame 10a and an upper frame 10b, and is a frame-shaped member in which the lower frame 10a and the upper frame 10b are connected at each other's ends. The area between the lower frame 10a and the upper frame 10b is a measuring space for measuring the thickness of the object to be measured 50.

[0014] The radiating unit 20 is supported by the lower frame 10a. The radiating unit 20 is scannable along the longitudinal direction of the lower frame 10a (the direction indicated by arrow Y). The detection unit 30 is supported by the upper frame 10b. The detection unit 30 is scannable along the longitudinal direction of the upper frame 10b. Alternatively, the radiating unit 20 may be supported by the upper frame 10b and the detection unit 30 may be supported by the lower frame 10a.

[0015] The radiation unit 20 and the detection unit 30 are arranged to face each other. A gap is provided between the radiation unit 20 and the detection unit 30. The measurement object 50 moving in the direction indicated by the arrow X passes through the gap between the radiation unit 20 and the detection unit 30. While the measurement object 50 is passing through, the radiation unit 20 and the detection unit 30 are scanned in a state of facing each other.

[0016] <Regarding the radiation unit and the detection unit> FIG. 2 is a cross-sectional view obtained by cutting the radiation unit and the detection unit along a plane including the feeding direction of the measurement object.

[0017] The radiation unit 20 includes a charged particle beam source 21, a radiation-side housing portion 22, and a radiation-side base 23.

[0018] A charged particle beam is emitted from the charged particle beam source 21. Examples of the charged particle beam include a β-ray, an α-ray, an electron beam, etc. When the charged particle beam is a β-ray, an example of the charged particle beam source 21 is a sealed container in which a nuclide: 85kr, which is a radioactive gas, is sealed.

[0019] The radiation-side housing portion 22 houses the charged particle beam source 21 inside. One surface of the radiation-side housing portion 22 facing the detection unit 30 side is an opening. The radiation-side base 23 closes the opening of the detection unit 30. The radiation-side base 23 is formed larger than the opening of the radiation-side housing portion 22. A first adjacent device 24 is mounted on the radiation-side base 23 at a position adjacent to the radiation-side housing portion 22.

[0020] An emission port 23a, which is an opening, is formed on the radiation-side base 23 at a position closing the opening of the radiation-side housing portion 22. The inside and the outside of the radiation-side housing portion 22 are communicated by the emission port 23a. The charged particle beam emitted from the charged particle beam source 21 is emitted to the outside of the radiation-side housing portion 22 from the emission port 23a.

[0021] Although not shown in the diagram, the radiation unit 20 is equipped with a shutter mechanism to prevent the emission of charged particle beams from the outlet 23a when the thickness of the object to be measured 50 is not being measured. The first adjacent device 24 is equipped with a power supply system and control circuit for driving the shutter mechanism.

[0022] The detection unit 30 comprises a detection device 31, a detection-side housing 32, and a detection-side base 33.

[0023] The detection device 31 is a device for detecting the dose of charged particle beams. The detection-side housing 32 houses the detection device 31 inside. The detection-side housing 32 has an opening on one side facing the radiation unit 20. The detection-side base 33 closes the opening of the detection-side housing 32. The detection-side base 33 is formed to be larger than the opening of the detection-side housing 32. A second adjacent device 34 is mounted on the detection-side base 33 at a position adjacent to the detection-side housing 32.

[0024] The detection-side base 33 faces the radiation-side base 23 with a gap between them. The gap between the radiation-side base 23 and the detection-side base 33 becomes the gap between the radiation unit 20 and the detection unit 30.

[0025] The detection-side base 33 has an inlet 33a, which is an opening, formed in a position that closes the opening of the detection-side housing 32. The inlet 33a is also formed in a position opposite the outlet 23a of the radiation unit 20. The inlet 33a connects the inside and outside of the detection-side housing 32.

[0026] The charged particle beam emitted from the outlet 23a of the radiation unit 20 enters the inside of the detection-side housing unit 32 through the entrance 33a. The dose of the charged particle beam that enters the inside of the detection-side housing unit 32 is detected by the detection device 31.

[0027] The second adjacent device 34 is equipped with a power supply system, control circuit, and the like for driving the detection device 31.

[0028] <About the magnetic field generating unit> The magnetic field generating unit 40 generates a magnetic field between the radiating unit 20 and the detection unit 30, directing the magnetic field from one side of the radiating unit 20 to the other. In Figure 2, the direction of the magnetic field is indicated by arrow Z when the radiating unit 20 is considered one side and the detection unit 30 is considered the other side.

[0029] The magnetic field generating unit 40 is composed of a first coil 41a and a second coil 41b. The first coil 41a is provided in the radiating unit 20. Figure 3 is a cross-sectional view of the radiating unit taken along the line III-III shown in Figure 2. Note that in Figure 3, the first adjacent device 24 is omitted for ease of understanding.

[0030] The first coil 41a is a coil that surrounds the charged particle source 21 with respect to the axis 60 passing through the outlet 23a and the inlet 33a. More specifically, the first coil 41a is provided on the surface 23b of the radiation-side base 23 that is the side on which the radiation-side housing 22 is provided. Furthermore, the first coil 41a is provided so as to surround the radiation-side housing 22 when viewed along the axis 60. The first coil 41a may also be provided on the surface 23c of the radiation-side base 23 that faces the detection-side base 33. It is also preferable that the axis 60 passes through the center of the outlet 23a and the center of the inlet 33a. The first coil 41a passes between the radiation-side housing 22 and the first adjacent device 24. Therefore, it can also be said that the first adjacent device 24 is arranged adjacent to the first coil 41a.

[0031] The second coil 41b is provided in the detection unit 30. Figure 4 is a cross-sectional view of the radiation section cut along the IV-IV line shown in Figure 2. Note that in Figure 4, the second adjacent device 34 is omitted for ease of understanding.

[0032] The second coil 41b is a coil that surrounds the detection device 31 with respect to the axis 60, when viewed along the axis 60. More specifically, the second coil 41b is provided on the surface 33b of the detection-side base 33 that is the side on which the detection-side housing 32 is provided. Furthermore, the second coil 41b is provided so as to surround the detection-side housing 32 when viewed along the axis 60. The second coil 41b passes between the detection-side housing 32 and the second adjacent device 34. Therefore, it can also be said that the second adjacent device 34 is arranged adjacent to the second coil 41b. Alternatively, the second coil 41b may be provided on the surface 33c of the detection-side base 33 that faces the radiation-side base 23.

[0033] By passing current through the first coil 41a and the second coil 41b, a magnetic field is generated between the radiating unit 20 and the detection unit 30 along the direction indicated by arrow Z in Figure 2. Furthermore, by forming a so-called Helmholtz coil with the first coil 41a and the second coil 41b, a more uniform magnetic field can be formed between the radiating unit 20 and the detection unit 30.

[0034] <Measuring the thickness of an object> Returning to Figure 1, in the measuring device 1, when measuring the thickness of the object to be measured 50, the radiating unit 20 and the detection unit 30 are scanned facing each other, and the object to be measured 50 is passed between the radiating unit 20 and the detection unit 30. While the radiating unit 20 and the detection unit 30 are scanning, a charged particle beam is emitted from the outlet 23a. The charged particle beam emitted from the outlet 23a passes through the object to be measured 50 and reaches the detection device 31 of the detection unit 30. In the measuring device 1, the thickness of the object to be measured 50 is calculated based on the attenuation of the dose of the charged particle beam as it passes through the object to be measured 50.

[0035] <Regarding the spread of charged particle beams> The charged particle beam emitted from the charged particle source 21 and exited from the exit port 23a spreads out radially towards the detection unit 30. As a result, some of the charged particle beam emitted from the exit port 23a passes outside the entrance port 33a and cannot reach the detection device 31.

[0036] In the measuring device 1, the thickness of the object to be measured 50 is calculated based on the attenuation of the dose of charged particle beams that have passed through the object to be measured 50. Here, a higher dose of charged particle beams reaching the detection device 31 is preferable for accurately measuring the thickness of the object to be measured 50. Therefore, it is desirable to direct the charged particle beams emitted from the outlet 23a into the entrance 33a as much as possible.

[0037] In the measuring device 1, as shown in Figure 2, a magnetic field is formed between the radiating unit 20 and the detection unit 30 by the magnetic field generating unit 40, directed from the radiating unit 20 to the detection unit 30. Here, if the direction of motion of the electrons that generate the charged particle beam includes a component that is not parallel to the magnetic field, the electrons are subjected to a Lorentz force. Due to the acceleration motion caused by the Lorentz force and motion in the same direction as the magnetic field, the electrons begin to undergo helical motion. That is, charged particle beams emitted from the outlet 23a and spreading radially, not toward the entrance 33a, are subjected to a Lorentz force, undergo helical motion, and their direction of propagation is deflected toward the entrance 33a.

[0038] As a result, even if the dose of charged particle beams emitted from the outlet 23a is the same, the presence of the magnetic field generator 40 allows more charged particle beams to be injected into the inlet 33a. With more charged particle beams injected into the inlet 33a, more charged particle beams reach the detection device 31. Therefore, it is possible to improve the measurement accuracy of the thickness of the object to be measured 50 without increasing the dose of charged particle beams emitted from the outlet 23a. In other words, the measuring device 1 can improve measurement accuracy while suppressing the amount of charged particle beam radiation from the charged particle source 21. If a Helmholtz coil is formed by the first coil 41a and the second coil 41b, a uniform magnetic field can deflect the direction of propagation of more charged particle beams toward the inlet 33a.

[0039] Furthermore, by suppressing the amount of charged particle radiation, it becomes unnecessary to expand the controlled area, which allows for miniaturization of the measuring device 1 and a reduction in the installation space required for the measuring device 1.

[0040] Furthermore, when the charged particle beam spreads radially, the detection accuracy at the edges of the object 50 being measured may decrease. However, by deflecting the charged particle beam, the decrease in detection accuracy at the object 50 being measured can be suppressed.

[0041] The magnetic field generating unit 40 may consist only of the first coil 41a, without including the second coil 41b. The magnetic field generated from the first coil 41a has a direction that is nearly parallel to the arrow Z shown in Figure 2, etc., in the range close to the first coil 41a. Therefore, by providing the first coil 41a on the side of the detection unit 30, the charged particle beam can be deflected in the direction shown by the arrow Z near the detection unit 30, and more charged particle beams can be injected from the entrance 33a. For this reason, if the magnetic field generating unit 40 is composed only of the first coil 41a, it is desirable to provide the first coil 41a on the side of the detection unit 30.

[0042] <Regarding variations in the magnetic field generation section> Figure 5 shows a modified example of the magnetic field generating unit. In Figure 5, as in Figure 2, a cross-sectional view is shown in which the radiating unit and the detecting unit are cut in a plane that includes the direction in which the object to be measured is fed. The magnetic field generating unit 40 may be configured to include a first magnet 42a and a second magnet 42b.

[0043] The first magnet 42a is provided in the radiating section 20, similar to the first coil 41a. The shape of the first magnet 42a is also similar to the first coil 41a, forming an annular shape centered on the axis 60. In other words, the first magnet 42a is obtained by replacing the first coil 41a shown in Figures 2 and 3 with an annularly formed permanent magnet. The magnetic poles of the first magnet 42a are oriented parallel to the axis 60.

[0044] The second magnet 42b is provided in the detection unit 30, similar to the second coil 41b. The shape of the second magnet 42b is also similar to that of the second coil 41b, forming an annular shape centered on the axis 60. In other words, the second magnet 42b is a permanent magnet formed in an annular shape, replacing the second coil 41b shown in Figures 2 and 4. The magnetic poles of the second magnet 42b are oriented parallel to the axis 60.

[0045] The first magnet 42a may be composed of multiple sections along the circumferential direction centered on the axis 60. The orientation of the magnetic poles of each of the multiple sections of the magnet is parallel to the axis 60.

[0046] Furthermore, the second magnet 42b may be configured to be divided into multiple parts along the circumferential direction centered on the axis 60. The orientation of the magnetic poles of each of the divided magnets is parallel to the axis 60.

[0047] Thus, even when the magnetic field generating unit 40 is configured to include a first magnet 42a and a second magnet 42b, a magnetic field can be generated between the radiating unit 20 and the detection unit 30, moving from one side of the radiating unit 20 to the other. This allows charged particle beams emitted from the outlet 23a and spreading radially, not toward the entrance 33a, to undergo helical motion due to the Lorentz force, thereby deflecting their direction of travel toward the entrance 33a.

[0048] <Example of adding a shielding section> Figure 6 shows a measuring device equipped with a shielding section. As shown in Figure 6, the measuring device 1 may be provided with a shielding section 70 that covers the first adjacent device 24 and the second adjacent device 34. By providing the shielding section 70, the first adjacent device 24 and the second adjacent device 34 can be protected from the magnetic field generated by the magnetic field generating section 40. The shielding section 70 is made of a high-permeability material, such as permalloy.

[0049] <Other> Some examples of the combinations of technical features that will be disclosed are listed below.

[0050] (1) A measuring device comprising: a radiation unit that houses a charged particle source; a detection unit that houses a detection device for detecting charged particle beams emitted from the charged particle source and is positioned at a distance from the radiation unit; and a magnetic field generating unit that generates a magnetic field between the radiation unit and the detection unit, with the radiation unit having an outlet for ejecting charged particle beams emitted from the charged particle source toward the outside, positioned opposite to the detection unit; and the detection unit having an inlet for injecting the charged particle beams into the interior, positioned opposite to the outlet.

[0051] (2) The measuring device according to (1), wherein the magnetic field generating unit is provided in one of the radiating unit and the detection unit, and comprises a first coil that surrounds the periphery of one of the charged particle source and the detection device with respect to the axis passing through the outlet and the inlet.

[0052] (3) The measuring device according to (2), wherein the magnetic field generating unit is provided in the other of the radiating unit and the detection unit, and comprises a second coil that, when viewed along the axis, surrounds the other of the charged particle source and the detection device with the axis as the center.

[0053] (4) The measuring device according to (3) above, wherein the first coil and the second coil constitute a Helmholtz coil.

[0054] (5) The measuring device according to (1), wherein the magnetic field generating unit is provided in one of the radiating unit and the detection unit, and includes a first magnet that surrounds the periphery of one of the charged particle source and the detection device with respect to the axis passing through the outlet and the inlet.

[0055] (6) The measuring device according to (5), wherein the magnetic field generating unit is provided in the other of the radiating unit and the detection unit, and includes a second magnet that, when viewed along the axis, surrounds the other of the charged particle source and the detection device with respect to the axis.

[0056] (7) The measuring device according to (6), wherein the first magnet and the second magnet are formed in an annular shape with respect to the axis.

[0057] (8) The measuring device according to (6), wherein the first magnet and the second magnet are divided into a plurality of parts along the circumferential direction.

[0058] (9) The measuring device according to any one of (1) to (8) above, further comprising an adjacent device arranged adjacent to the magnetic field generating unit, and a shielding unit surrounding the adjacent device to shield the magnetic field generated from the magnetic field generating unit.

[0059] (10) The measuring device according to any one of (1) to (9) above, wherein the charged particle source is a beta-ray source that emits beta rays.

[0060] (11) The measuring device according to any one of (1) to (10), further comprising a frame that scannably supports the radiation unit and the detection unit with the outlet and the inlet facing each other. [Explanation of Symbols]

[0061] 1. Measuring device 10 frames 10a Bottom frame 10b Upper frame 20 Radiation section 21 Charged particle sources 22 Radiation side containment section 23 Radiation side base 23a Output port 23b,23c plane 24 First adjacent device 30 Detection unit 31 Detection device 32 Detection side housing 33 Detection-side base 33a Inlet 33b,33c plane 34 Second adjacent device 40 Magnetic field generation unit 41a First coil 41b Second coil 50 Object to be measured 60 axis 70 Shielding part

Claims

1. A radiation section that houses a charged particle source, A detection device for detecting charged particle beams emitted from the charged particle source is housed inside, and the detection unit is positioned at a distance from the emission unit, The system includes a magnetic field generating unit that generates a magnetic field between the radiating unit and the detection unit, with the magnetic field generating unit directing from one side of the radiating unit and the detection unit to the other side. The radiation unit has an outlet formed in a position opposite the detection unit for emitting charged particle beams emitted from the charged particle source toward the outside. The detection unit is a measuring device in which an inlet for injecting the charged particle beam is formed at a position opposite to the outlet.

2. The measuring device according to claim 1, wherein the magnetic field generating unit is provided in one of the radiating unit and the detection unit, and includes a first coil that surrounds one of the charged particle source and the detection device with respect to the axis passing through the outlet and the inlet.

3. The measuring device according to claim 2, wherein the magnetic field generating unit is provided in the other of the radiating unit and the detection unit, and includes a second coil that, when viewed along the axis, surrounds the other of the charged particle source and the detection device with the axis as the center.

4. The measuring device according to claim 3, wherein the first coil and the second coil constitute a Helmholtz coil.

5. The measuring device according to claim 1, wherein the magnetic field generating unit is provided in one of the radiating unit and the detection unit, and includes a first magnet that surrounds one of the charged particle source and the detection device with respect to the axis passing through the outlet and the inlet.

6. The measuring device according to claim 5, wherein the magnetic field generating unit is provided in the other of the radiating unit and the detection unit, and includes a second magnet that, when viewed along the axis, surrounds the other of the charged particle source and the detection device with respect to the axis.

7. The measuring device according to claim 6, wherein the first magnet and the second magnet are formed in an annular shape with respect to the axis.

8. The measuring device according to claim 6, wherein the first magnet and the second magnet are divided into a plurality of parts along the circumferential direction.

9. An adjacent device arranged adjacent to the magnetic field generating unit, The measuring device according to claim 1, further comprising a shielding section that surrounds the adjacent device and shields the magnetic field generated from the magnetic field generating section.

10. The measuring apparatus according to claim 1, wherein the charged particle source is a beta-ray source that emits beta rays.

11. The measuring device according to claim 1, further comprising a frame that scannably supports the radiation unit and the detection unit while the discharge port and the inlet port are facing each other.

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