JP3794983B2 - Electron acceleration space structure of X-ray microscope - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron acceleration space in an X-ray microscope in which an X-ray image is observed by accelerating and enlarging an electron image generated corresponding to a shadow formed on a photoelectric conversion surface by irradiation with X-rays. Related to the structure.
[0002]
[Prior art]
Conventionally, an X-ray microscope has been used as a measuring instrument capable of obtaining a high-resolution transmission image of an object using X-rays having a short wavelength and strong transmission power as a light source.
X-ray microscopes have a method for enlarging and converging the X-ray beam itself by using an X-ray imaging element such as a Fresnel zone plate or a grazing incidence mirror in order to enlarge the image. Since the focal length of the system becomes long, the apparatus becomes large, and since the image magnification cannot be adjusted arbitrarily, there is a problem that it is necessary to use an optical microscope for specifying the observation position of the object. Further, since the light collection efficiency is poor, a powerful X-ray light source such as synchrotron radiation is required.
[0003]
On the other hand, there is a projection enlargement method in which a sample is placed near a point light source and the projected image of X-rays that diverge from the light source and transmitted through the sample is observed. Therefore, the practical limit of the resolution is about 0.1 to 0.2 μm, and there is a great restriction on the measurement object.
The contact method in which the sample is brought into close contact with the photosensitive plate and irradiated with X-rays and the developed image is magnified and observed with an optical system does not use an X-ray magnifying optical system. Since it is in close contact, the blur is small, so a high-resolution image can be easily obtained in principle. However, since the sensitivity is extremely low at present, a powerful X-ray source is required. In order to enlarge and observe an X-ray image, the photosensitive plate is taken out from the vacuum vessel, developed, and then observed with another optical microscope or the like, which requires complicated work.
[0004]
In order to overcome the disadvantages of the conventional X-ray microscope, the applicant of the present application has already generated a photoelectric conversion surface by applying X-rays from the back by bringing the sample into close contact with the photoelectric conversion surface according to Japanese Patent Application No. 2001-235678. A new type X-ray microscope apparatus is disclosed that draws and enlarges electrons, forms an image on the surface of an electron detection element, and presents the image as a visible image.
In the disclosed X-ray microscope, as shown in FIG. 4, the X-ray that has passed through the sample is applied to a photoelectric conversion element, and the generated electrons are extracted by a strong electric field and accelerated. The image is magnified by an electronic image enlarging apparatus using a lens and a projection electromagnetic lens, and projected onto an electron beam detecting element surface such as a fluorescent screen or a CCD element surface to be visualized.
[0005]
According to the disclosed X-ray microscope, a high-resolution X-ray transmission image can be obtained in real time without taking time and effort such as development.
In addition, in the conventional X-ray microscope, only an image with a clear contrast using hard X-rays was obtained. However, in the disclosed apparatus, X-rays transmitted through the sample are converted into electrons by a photoelectric conversion element. It is possible to create a grayscale image that reflects the difference between them, and observation with soft X-rays is also possible. For this reason, the amount of information of the acquired X-ray image has increased remarkably, and living organisms can be observed.
[0006]
Unlike the apparatus using an X-ray optical system having a weak convergence power, the disclosed apparatus uses an electronic image enlarging apparatus having a sufficient convergence power, so that the entire apparatus becomes small and the sample is set in close contact with the photoelectric conversion surface. Therefore, an X-ray transmission image without blur can be obtained.
Furthermore, since the electronic image enlargement device of the disclosed X-ray microscope can change the image magnification by adjusting the current of the electromagnetic coil, the target position can be confirmed at a low magnification even when observing a minute part. Thus, the magnification can be increased to obtain a target image, and the target can be accurately captured and observed.
[0007]
In the magnetic lens as well as the optical lens, there is a relationship of M = b / a between the object distance a, the image distance b, and the magnification M. Therefore, the magnification M of the microscope when the objective electromagnetic lens and the two projection electromagnetic lenses are combined is
M = M ₁ M ₂ M ₃ = (B ₁ / A ₁ ) (b ₂ / A ₂ ) (b ₃ / A ₃ )
Is required. Here, subscripts 1, 2, and 3 represent the objective lens, the first projection lens, and the second projection lens, respectively.
[0008]
FIG. 5 shows the result of the electron trajectory analysis when passing through the magnetic lens group in one example of the X-ray microscope. In the figure, the horizontal axis indicates the distance in the electron beam axis direction measured with an appropriate base point, and the vertical axis indicates the distance from the axis. Electrons converge and expand while rotating by a magnetic field, but the figure ignores the rotation and displays the movement of the electrons only by changing the distance from the axis.
Here, the case where the objective electromagnetic lens is installed at a position of about 27 mm, the first projection electromagnetic lens is installed at a position of about 130 mm, the second projection electromagnetic lens is installed at a position of about 185 mm, and the image observation unit is analyzed at a position of about 210 mm is analyzed. Yes.
[0009]
An electron beam having a radius of 0.01 mm is once narrowed by an objective lens having a maximum magnetic flux density of about 0.14T, then expanded, and then expanded again by a first projection lens having a peak magnetic flux density of about −0.2T. The second projection lens having a density of about + 0.2T is expanded to an electron beam having a radius of about 2.25 mm, and is observed on the phosphor screen. The overall magnification as an image is about 225 times.
Since the electrons rotate in the magnetic lens, a pair of coils excited in opposite directions are used as projection lenses to cancel the rotation and obtain an upright image.
[0010]
In order to miniaturize a high-power and high-performance X-ray microscope apparatus as much as possible, it is necessary to increase the magnification of the electromagnetic lens. As the maximum magnetic flux density is higher and the peak width is narrower, the electromagnetic lens becomes a stronger lens and has a higher magnification. Therefore, in order to make a strong lens, it is effective to increase the number of turns of the coil and the exciting current, to narrow the gap between the pole pieces, and to reduce the inner diameter.
[0011]
The position of the sample is determined so that an enlarged image formed by the combination of the objective lens and the projection lens is formed on the fluorescent screen. In order to simplify the structure of the apparatus, it is preferable not to change the positions of the sample, the electromagnetic lens, and the phosphor screen.
For example, when the projection lens is set to a high magnification and the focus is not good, the exciting current of the electromagnetic coil of the objective lens is adjusted to obtain a magnification M ₁ Use the method of changing the focus.
For simplification of design and adjustment, if the two projection lenses have the same shape and the same excitation current flows, the same magnification will be obtained. ₂ = M ₃ Is established.
[0012]
By the way, in an X-ray microscope using photoelectric conversion, the higher the electric field applied to the electrons generated on the photoelectric conversion surface, the higher the speed of the electrons and the shorter the wavelength, thus increasing the resolution and reducing aberrations such as blurring and distortion. To do. However, although the deflection force due to the magnetic field is proportional to the velocity, the electron inertia force increases in proportion to the square of the velocity, so the amount of refraction does not increase, so the magnification of the electromagnetic lens decreases as the electron velocity increases. To do.
Therefore, if the electron velocity is increased with the same magnification to improve resolution and aberration, there is a problem that the apparatus becomes large.
[0013]
The magnification M of the objective electromagnetic lens ₁ To increase the object distance a between the photoelectric conversion surface and the lens ₁ If is reduced, the electron acceleration space for extracting and accelerating the electrons generated on the photoelectric conversion surface is shortened. A strong electric field is required to sufficiently accelerate electrons, but if a high potential difference occurs at a small interelectrode distance, a discharge occurs and a necessary electric field state cannot be created, and a sufficient effect cannot be obtained after all. .
Note that, when an electron image generated on the photoelectric conversion surface is extracted, there is a distribution in the direction in which electrons are emitted from the photoelectric conversion surface, and thus aberration such as blurring is likely to occur. In order to prevent this, it is preferable to cause the objective electromagnetic lens to converge before the electrons spread.
[0014]
[Problems to be solved by the invention]
Therefore, the problem to be solved by the present invention is to accelerate the electron image generated by irradiating X-rays and projecting the shadow of the sample onto the photoelectric conversion surface, and to enlarge and project the X-ray image onto the phosphor screen. In an X-ray microscope to be observed, an electron acceleration space structure having a sufficiently high electron velocity and an action of a high-magnification objective electromagnetic lens is provided.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the electron acceleration space structure of the X-ray microscope of the present invention is provided between the anode and the sample holder and a pair of annular pole pieces arranged on the outside and provided at the entrance of the lens barrel.
The conductive anode is formed of a non-magnetic material, and has a flat bottom surface provided with an opening connected to the lens barrel at the center, and a cylindrical side wall parallel to the axis with the axis of the lens barrel as the central axis .
The pole piece upper pole is arranged so that the inner peripheral surface is in contact with the outer periphery of the anode side wall, and the pole piece lower pole has an annular plane perpendicular to the axis of the lens barrel, and this plane is on the outer wall of the bottom surface of the anode. It arrange | positions so that it may oppose.
[0016]
The sample holder is a conductive cylinder having a diameter smaller than the inner diameter of the anode side wall, has a front surface formed substantially perpendicular to the axis and provided with an opening in the center, and the position of the sample in the sample holder is The front surface is arranged in parallel with the bottom surface of the anode so as to substantially coincide with the axis of the lens barrel.
In this electron acceleration space, when a potential difference is applied between the sample holder and the anode, a parallel electric field is generated along the central axis, and when a magnetic flux is generated between the pole piece upper pole and the pole piece lower pole, A rotationally symmetric magnetic field is generated between the anodes.
[0017]
In the electron acceleration space structure of the present invention, the cylindrical sample holder and the cylindrical anode are combined in a rotationally symmetrical manner, and the front surface of the sample holder and the bottom surface of the anode are disposed so as to face each other substantially in parallel. The electric field generated between the holder and the anode is sufficiently parallel near the central axis.
Since the photoelectric conversion surface is gripped on the front surface of the sample holder and the electron emission surface is exposed at the back of the opening, the emitted electrons are straight along the optical axis without deviating from the optical axis by a parallel electric field. Drawn and accelerated.
Since the outer diameter of the sample holder is smaller than the inner diameter of the side wall of the anode, it is possible to secure a distance that does not discharge even when a high voltage is applied between the inner wall surface of the anode and the outer surface of the sample holder.
[0018]
The magnetic field for the objective lens is constituted by a magnetic gap formed between the pole piece upper pole and the pole piece lower pole.
Since the pole piece upper pole is arranged outside the anode side wall and the inner peripheral surface surrounds the axis of the acceleration space, the pole piece lower pole is arranged from the outside of the anode bottom to the inside of the acceleration space, Due to the magnetic flux generated between the inner peripheral surface of the pole piece upper pole and the plane of the pole piece lower pole, a strong magnetic field gradient exists in the electron acceleration space. Further, when observed along the optical axis, the peak of the magnetic flux density can be disposed at a position close to the photoelectric conversion surface.
[0019]
Thus, in the electron acceleration space structure of the present invention, the objective lens magnetic field is superimposed in the acceleration space where the acceleration electric field works, so that a sufficient electron acceleration region is ensured and before the electron flow is diffused. By converging, the amount of imaging electrons is secured to reduce aberrations, and the objective lens is operated in a low speed region, so that an image with a sufficiently large magnification can be easily formed.
[0020]
The positions of the sample holder and the pole piece upper pole are preferably arranged so that the front surface of the sample holder is surrounded by the inner peripheral surface of the pole piece upper pole on the central axis.
To increase the magnetic field for the objective lens, it is better that the distance between the tip surface of the pole piece upper pole and the side surface of the pole piece lower pole is shorter. However, since the anode is inserted, the distance between the two cannot be sufficiently shortened. For this reason, it is preferable to arrange the photoelectric conversion surface so as to be close to the end face of the pole piece so that the peak of the magnetic flux density appears at a position closer to the photoelectric conversion surface even if the strengthening of the magnetic field is suppressed to some extent.
[0021]
In addition, an opening that exposes the photoelectric conversion surface irradiated with X-rays is provided at the center position on the front surface of the sample holder. This opening is gently chamfered to form a cathode surface that is substantially parallel to the anode bottom surface. In addition, it is preferable to remove the sharp edges so as not to disturb the parallel electric field in the electron acceleration space.
Furthermore, when using a sample slide with an integrated photoelectric conversion surface, it is possible to place the sample slide in the receiving groove and screw the cap with a hole in the shaft so that the sample slide can be pressed from the front side. Convenient. When a sample holder having such a structure is used, it is preferable that the front surface of the cap is formed almost flat so that the cathode surface faces the anode bottom surface.
[0022]
In addition, it is preferable to form the side surface inside the axial direction of the inner peripheral surface of the pole piece upper pole in a tapered shape. By concentrating the magnetic flux generated from the surface of the pole piece as close as possible to the photoelectric conversion surface, a more preferable magnetic flux density distribution can be formed in the electron acceleration space.
Moreover, it is preferable to attach the aperture piece which has a pinhole in the opening part connected to the lens barrel of an anode. Similar to an ordinary optical system, only the electron beam in the vicinity of the central axis is received in the lens barrel, thereby reducing the aberration.
[0023]
Furthermore, it is preferable that at least an end portion of the outer wall of the lens barrel is formed integrally with the anode.
The lens barrel forms a high vacuum passage through which an electron beam passes, and the perpendicularity to the anode bottom surface is important. Further, the portion where the magnetic lens is formed with the electron acceleration space is formed extremely thin in order to increase the magnetic flux density. Moreover, it is a diaphragm with respect to the atmospheric pressure part which installs a magnetic coil etc. Therefore, in the past, the lens barrel was welded to the anode, but it was made to be exactly perpendicular to the anode and to prevent vacuum leakage. High-level manufacturing technology was required, such as preventing burrs from being generated because of the discharge that hinders formation.
However, by cutting out from one metal lump and integrally forming the anode part and the lens barrel, problems such as vacuum leakage and burrs are eliminated.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to examples.
FIG. 1 is a cross-sectional view showing an electron acceleration space structure for an X-ray microscope of the present embodiment, FIG. 2 is a drawing showing an electric field state in the electron acceleration space, and FIG. 3 is a relationship between magnetic flux density and electron beam trajectory in the electron acceleration space. FIG.
The electron acceleration space structure of the present invention is a space for accelerating electrons generated on a photoelectric conversion surface in an X-ray microscope for observing an X-ray image by converting it into an electron image. Be placed.
The electron accelerating space structure of the present embodiment is characterized in that pole pieces forming an objective lens are arranged around and the first stage of the convergence expansion process is performed in the acceleration space.
[0025]
As shown in FIG. 1, the electron acceleration space 1 is a space surrounded by a casing 11, a sample stage 13, a sample holder 21, and an anode 31.
The casing 11 covers the space of the sample chamber 2 used when exchanging the sample, and is joined to the casing of the electronic image enlargement unit that houses an electromagnetic coil and the like. The housing 11 includes a partition wall 12 having a circular hole centered on the electron beam trajectory, and a sample stage 13 is fixed to the partition wall 12. The sample stage 13 inserts and fixes the sample holder 21 and is formed of an electrically insulating material. The sample stage 13 is supported so that the axis of the sample holder 21 substantially coincides with the X-ray central axis. A mechanism capable of adjusting the shaft position while maintaining the direction is provided.
[0026]
The sample holder 21 has a cylindrical shape, is provided with a hole through which X-rays pass along the central axis, and includes a holder piece 22 at the tip. A cap 23 is engaged with the tip of the holder piece 22 so that the sample slide 24 fitted in the groove provided on the tip surface of the sample holder 21 can be fixed.
The sample slide 24 is formed by depositing a double thin film layer made of conductive gold and cesium iodide having a good photoelectric conversion performance on a substrate such as a collodion film that transmits X-rays. A sample to be observed is placed on the transmission thin film, and set so that the surface on which the sample is placed comes to the side on which the X-rays are incident.
The holder piece 22 can be fixed by adjusting the axial position of the sample slide 24 by engaging with the main body of the sample holder 21 with a screw and tightening with a presser nut.
[0027]
A flange portion of the anode 31 is sandwiched between the partition wall 12 and the housing that houses the electromagnetic coil 41. The anode 31 has a bowl-shaped recess at the center. The recess is formed by a bottom surface 32 substantially perpendicular to the central axis and a side wall 33 substantially perpendicular thereto.
The side wall 33 is a non-magnetic material, has a circular cross section and has a cylindrical shape in which the axis of the electron beam and the central axis are common, and an appropriate distance is provided between the inner wall and the outer wall of the sample holder 21. Discharge does not occur even when a high voltage of the required level is applied.
[0028]
The bottom surface 32 is a conductive non-magnetic material and is formed substantially flat, and has a hole in the center where an electron is incident on the lens barrel 4 of the electronic image enlargement unit.
The lens barrel 4 is a non-magnetic thin tube and is airtightly fixed to the bottom surface 32.
An aperture holder 35 into which an aperture plate 34 is inserted is inserted into the opening of the bottom surface 32. The aperture plate 34 is a plate in which a small hole having a diameter of 0.3 mm or 0.5 mm, for example, is provided at the center, and improves the aberration by limiting the electron beam entering the lens barrel 4 to only the paraxial component. is there.
Since it is necessary to change the diameter of the pinhole depending on the measurement conditions, the aperture holder 35 is configured so that it can be attached and detached relatively easily from the front of the lens barrel 4 using an appropriate jig.
[0029]
It arrange | positions so that the inner side front end surface of the annular | circular pole piece upper pole 42 may contact | connect the outer wall of the side wall 33. FIG. The inner front end surface of the pole piece upper pole 42 is finished to a smooth curved surface with high roundness. Further, the side surface on the downstream side in the electron beam traveling direction forms a taper toward the central axis by scraping off a portion near the opposing pole piece lower pole 43.
The pole piece lower pole 43 is provided on the back side of the bottom surface 32 of the anode 31 and is disposed so that the surface perpendicular to the electron beam axis is substantially in contact with the back surface of the bottom surface 32.
The pole piece upper pole 42 and the pole piece lower pole 43 are opened at one corner of a yoke 44 configured to surround the electromagnetic coil 41 and joined to the ends thereof. When the electromagnetic coil 41 is excited, the pole piece A large amount of magnetic flux is generated in the gap between them to form a strong magnetic field in the electron acceleration space 1 and to act as a magnetic lens for converging and expanding the electron flow.
[0030]
The anode 31 is grounded via the casing 11 of the sample chamber 2 portion or the casing of the electromagnetic coil.
A negative electrode terminal of a DC power supply device is connected to the sample holder 21 and a negative voltage up to about −20 kV is applied. When a negative voltage is applied to the sample holder 21, the grounded anode 31 and the negative potential holder piece 22 face each other, so that a rotationally symmetric electric field as shown in FIG. 2 is formed in the electron acceleration space 1. This electric field has a shape in which equipotential surfaces perpendicular to the axis are arranged in parallel near the central axis.
Electrons generated in the photoelectric conversion film of the sample slide 24 by X-ray irradiation are drawn out by the electric field in the electron acceleration space 1 and accelerated to enter the lens barrel 4. When the central portion is irradiated with X-rays, the generated electron stream travels in the vicinity of the central axis, but is accelerated by a parallel electric field, so that the electron trajectory does not deviate greatly from the central axis.
[0031]
The aperture holder 35 is chamfered so as not to have a sharp edge on the side of the electron acceleration space 1 to be a substantially flat surface, and does not protrude greatly from the bottom surface 32 so as to generate an electric field generated in the electron acceleration space. I do not disturb.
The tip of the sample holder 21 inserted into the electron acceleration space 1 is preferably formed on a flat surface perpendicular to the axis. Further, the edge of the hole for exposing the surface of the sample slide 24 to the electron acceleration space 1 is chamfered to eliminate an acute angle portion.
[0032]
FIG. 3 is a drawing for explaining the relationship between the magnetic flux density and the electron beam trajectory in the electron acceleration space structure of this embodiment. The horizontal axis of FIG. 3 is a distance measured from an arbitrary base point, and FIG. 3A shows the shape change of the electron flow when a parallel electron flow enters, with the vertical axis taking the distance from the central axis. 3 (b) schematically shows the position of the electron accelerating space structure corresponding to the shape change state of the electron current, and FIG. 3 (c) shows the change in the magnetic flux density along the traveling axis of electrons, with the magnetic flux density on the vertical axis. Indicates.
[0033]
When the magnetic flux formed by the pole piece upper pole 42 and the pole piece lower pole 43 is applied to the electron flow at the axial position of the electron acceleration space 1, the electron flow converges and expands as shown in FIG. To do.
Since the magnetic flux density has a distribution with a peak P at an intermediate position between the pole piece upper pole 42 and the pole piece lower pole 43, it exerts a force that deflects the electrons traveling along the central axis in the axial direction. It has the effect of. The lens magnification increases as the maximum magnetic flux density at the peak P increases, the peak width H decreases, and the peak sharpens.
[0034]
Further, the closer the electrons are to the photoelectric conversion surface 24, the slower the electrons are. Therefore, the closer the peak P of the magnetic flux density is to the photoelectric conversion surface 24, the greater the lens effect.
For this reason, the downstream side surface of the pole piece upper pole 42 is tapered to make it difficult for the magnetic flux to be connected between the pole piece lower poles 43 so that the magnetic flux density peak P approaches the photoelectric conversion surface 24.
[0035]
Since the photoelectric conversion surface 24 is in a region where the magnetic flux density is changing, electrons emitted from the surface move in a direction that converges somewhat toward the central axis, and the curvature is maximized at the sharp magnetic flux density peak P. Converge and then expand at the same moment as it passes through the convergence point. The objective lens in the electron acceleration space 1 expands the electron flow having a radius of 0.01 mm to an electron flow having a radius of about 0.1 mm at the position of the next first projection lens, and is projected onto the phosphor screen through the second projection lens. The position is about 2.3 mm.
[0036]
The stronger the electric field E in the electron acceleration space 1, the shorter the electron wavelength λ. On the other hand, the resolution is proportional to the third power of the wavelength λ, and the spherical aberration and chromatic aberration are inversely proportional to the electric field E. Therefore, the higher the voltage, the higher the quality of the electronic image.
However, if the distance between the electrodes is too small, a discharge occurs between the electrodes and an effective electric field cannot be maintained. Therefore, the distance between the cap 23 of the holder piece 22 and the anode bottom surface 32 and the distance between the anode side wall 33 and the outer periphery of the holder piece 22 can be reduced. The distance cannot be made too small.
[0037]
On the other hand, when this distance is increased, the pole piece 42 arranged outside the outer wall 33 is separated from the electron trajectory, so that a high magnetic flux density cannot be generated at the position of the electron flow.
For this reason, there is an appropriate compromise between the distance between the two, and in this embodiment, the distance between the tip end surface of the cap 23 and the anode bottom surface 32 is approximately 6 mm, and the distance between the outer periphery of the holder piece 22 and the anode side wall 33 is approximately 6 mm. With good results.
[0038]
The lens barrel 4 is installed through the portion where the objective lens electromagnetic coil 41 is disposed and the portion where the two projection lens electromagnetic coils are disposed, and guides the electron flow to the phosphor screen. Outside the lens barrel 4, a stigma coil 45 and a deflection coil for reducing aberration are provided between the objective lens and the projection lens.
The anode 31 and the lens barrel 4 can be joined by welding. However, a high level of technology is required to manufacture such that there is no perpendicularity to the bottom surface 32 and no vacuum leakage from the weld. In addition, burrs around the weld must be processed so as not to disturb the electric field distribution.
[0039]
Therefore, the anode 31 and the lens barrel 4 may be integrally formed and cut out from a single nonmagnetic material. When integrated and manufactured by machining in this way, it is relatively easy to guarantee a squareness and to make parts free from vacuum leakage and burrs.
In particular, a vacuum shut-off valve is provided between the objective lens area and the projection lens area so that the same vacuum is maintained during operation, and the vacuum is shut off when the sample chamber 2 and the electron acceleration space 1 are opened to the atmosphere and the sample is exchanged. Thus, in order to facilitate the preparation for operation by maintaining the vacuum on the downstream side, the lens barrel 4 is divided at the position of the vacuum shut-off valve. Since it becomes shorter, it becomes easier to process integrally with the anode 31.
[0040]
The description based on the above embodiment has been made with respect to an example of an apparatus that embodies the technical idea of the present invention, and it goes without saying that there are various modifications to the configuration for carrying out the present invention. Absent.
For example, the side wall of the anode is formed in a cylindrical shape, but may be in the form of a bulge, for example, as long as it can hold a distance that does not cause discharge between the anode and the sample holder.
[0041]
Further, the aperture holder may not project from the bottom surface, and an electric field distribution with better parallelism may be formed in the electron acceleration space.
Alternatively, the sample slide set in the sample holder may not be pressed with a cap but may be pressed from the inside and stopped.
In addition, by applying a metal mesh to the back of the sample slide and connecting it to the sample holder to apply a negative voltage so that the electric field acts from the back side of the photoelectric conversion film, electrons are more easily emitted. You may make it do.
Further, the objective lens and the projection lens may be formed by combining a plurality of electromagnetic gaps.
[0042]
【The invention's effect】
As described above, the electron acceleration space structure for the X-ray microscope of the present invention arranges the magnetic flux density peak that forms the objective lens in the high electric field region for extracting and accelerating electrons from the photoelectric conversion surface. The electron velocity can be sufficiently increased and a high-magnification objective lens can be used to form and observe a high-resolution X-ray image with little aberration.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an electron acceleration space structure for an X-ray microscope according to one embodiment of the present invention.
FIG. 2 is a diagram illustrating a state of an electric field in an electron acceleration space according to the present embodiment.
FIG. 3 is a diagram for explaining a relationship between a magnetic flux density and an electron beam locus in an electron acceleration space according to the present embodiment.
FIG. 4 is a conceptual diagram illustrating the configuration of an X-ray microscope to which the present invention is applied.
FIG. 5 is a diagram showing an analysis result of an electron flux diameter change when passing through a magnetic lens group of an X-ray microscope.
[Explanation of symbols]
1 electron acceleration space
2 Sample room
4 Lens tube
11 Case
12 Partition wall
13 Sample stage
21 Sample holder
22 Holder piece
23 cap
24 Sample slide
31 Anode
32 Anode bottom
33 Anode side wall
34 Aperture plate
35 Aperture holder
41 Electromagnetic coil
42 pole piece upper pole
43 Pole Peace Lower Pole
44 York
45 Stigma Coil

Claims (7)

An electron accelerating space structure for an X-ray microscope provided between an anode and a sample holder and having a pair of annular pole pieces arranged outside and provided at the entrance of a lens barrel, the anode being formed from a non-magnetic material A flat bottom surface provided with an opening for connecting to the lens barrel and a cylindrical side wall parallel to the axis with the axis of the lens barrel as a central axis, and the pole piece upper pole with the inner peripheral surface of the side wall The pole piece lower pole is disposed so as to be in contact with the outer periphery, and is disposed so that the lower surface of the pole piece has an annular plane perpendicular to the axis of the lens barrel and the plane faces the outer wall of the bottom surface. A conductive cylinder having a diameter smaller than the inner diameter and having a front surface formed substantially perpendicular to the axis and provided with an opening in the center, the center axis of the sample holder being coincident with the axis of the lens barrel and the The front surface is set parallel to the bottom surface, and the sample holder and the anode To generate a magnetic field between the sample holder and the anode by generating a magnetic field between the upper pole and the lower pole of the pole piece. An electron acceleration space structure characterized by being generated and used. The electron acceleration space structure according to claim 1, wherein the front surface of the sample holder is disposed at a position surrounded by an inner peripheral surface of the pole piece upper pole. 3. The electron acceleration space structure according to claim 1, wherein the opening on the front surface of the sample holder is chamfered. The electron acceleration space structure according to any one of claims 1 to 3, wherein the front surface of the sample holder is a front surface of a cap that presses the sample slide from the front surface side. 5. The electron acceleration space structure according to claim 1, wherein an axially inner side surface of the inner peripheral surface of the pole piece upper pole is formed in a tapered shape. The electron acceleration space structure according to claim 1, wherein an aperture piece having a pinhole is attached to an opening connected to the lens barrel of the anode. The electron acceleration space structure according to any one of claims 1 to 6, wherein at least an end portion of an outer wall of the lens barrel is formed integrally with the anode.

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