Light guide assembly for electron microscope

Abstract

To provide an electron microscopy capable of detecting a Raman spectroscopy and / or cathodoluminescence detection.SOLUTION: An electron microscopy comprises an optical guide assembly 250 having: an electron column pole piece 202; and a mirror 220 which is coupled to the electron column pole piece 202 so as to be operated and contains one or more detector 257 and a stress limit aperture 225 in which an electron beam 207 from an electron source 204 passes. The mirror 220 is structured so as to collect a back scattering electron and a secondary electron by reflecting a light. A scanning electron microscopy 120 further comprises a chamber 203 as a vacuum environment, and the electron column pole piece 202 and the optical guide assembly 250 are arranged in the chamber 203.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates generally to electron microscopes capable of Raman spectroscopy and / or cathodoluminescence detection. [Background technology]

[0002] It is generally recognized that combining Raman spectroscopy or cathodoluminescence detection with electron microscopy has many advantages, especially when using what is known as environmental scanning electron microscopy (ESEM) techniques. For example, Raman microscopy can aid in material identification, and when combined with scanning electron microscopy, can clearly identify sample features that may have different compositional and / or structural properties. ESEM techniques can operate in a mode that allows imaging in low vacuum and relatively humid environments, which reduces sample drying, which creates sample motion that reduces image resolution. However, it is generally recognized that low vacuum, high humidity environments have a detrimental effect on the imaging performance of electron microscopes. In the example described here, what is known as a pressure limiting aperture (PLA) is used to separate the low vacuum environment beneficial to ESEM techniques from the high vacuum environment beneficial to electron microscopy.

[0003] Combining electron microscopy with optics and PLA for Raman spectroscopy or cathodoluminescence detection is well known, and examples are described in U.S. Pat. No. 7,718,979, entitled "Particle-Optical Apparatus for Simultaneous Observation of a Sample with Particles and Photons," the disclosure of which is incorporated herein by reference in its entirety for various purposes. For example, the '979 patent describes a mirror with a hole in the middle between an electron column pole piece and the sample. An electron beam travels from a source and passes through the hole in the mirror to interact with the sample. The mirror also has a surface that is positioned to reflect and redirect light from the light source to the sample, and to collect and direct light from the sample to a photodetector.

[0004] However, the aforementioned embodiments suffer from several significant drawbacks. First, mirrors are limited to use in high vacuum environments, and because the mirrors used to reflect light are placed between the sample and the electron column pole piece, the mirrors significantly reduce the ability of electrons to reach the electron column pole piece from the sample. This significantly reduces the efficiency of the electron microscope detector. Furthermore, it is highly desirable to keep the working distance of the electron beam path as short as possible. However, the aforementioned PLA configurations increase the working distance, reducing the imaging performance of the electron microscope.

[0005] Therefore, an electron microscope design configured to enable Raman spectroscopy in a low vacuum environment without the adverse effects of signal blockage or increased working distance would provide significant advantages over previous embodiments. Summary of the Invention

[0006] Systems, methods, and articles of manufacture that address these and other needs are described herein with respect to exemplary, non-limiting implementations. Various alternatives, modifications, and equivalents are possible.

[0007] An embodiment of an electron microscope system is described that includes an electron column pole piece and a light guide assembly operably coupled to the electron column pole piece, the light guide assembly also including one or more detectors and a mirror including a pressure limiting aperture through which an electron beam from an electron source passes, the mirror also being configured to reflect light and to collect backscattered and secondary electrons.

[0008] In some implementations of the electron microscope system, the electron column pole piece and light guide assembly are disposed within a chamber with a low vacuum environment, the electron beam is directed to a sample that generates backscattered electrons and secondary electrons in response to the electron beam, and in some cases, the light guide assembly is operatively coupled to an electron lens of the electron column pole piece.

[0009] Also, the light guide assembly and the electron pillar pole piece may be configured to operably couple with a pressure-resistant seal. More specifically, the mirror can provide a pressure-resistant seal for the electron pillar pole piece. Alternatively, the light guide assembly and the intermediate element may be configured to operably couple with a pressure-resistant seal, and the intermediate element and the electron pillar pole piece may be configured to operably couple with a pressure-resistant seal.

[0010] Further, the mirror may be configured to reflect light from the sample to the photodetector and to reflect light from the light source to the sample. The light source may include a laser or a light emitting diode (LED). The mirror may also be configured to convert the backscattered electrons to secondary electrons, and the light guide assembly may also further include a collector electrode configured to collect the converted secondary electrons. In particular, the collector electrode may include a front plate with an aperture through which the backscattered electrons and the secondary electrons travel to the mirror.

[0011] Finally, in some implementations, the light guide assembly may further include an electrode configured to collect secondary electrons, and in some cases, the one or more detectors include one or more solid-state diode detectors.

[0012] Also described are embodiments of a light guide assembly that includes a mirror that includes a pressure-limiting aperture through which an electron beam from an electron source passes, and the mirror is configured to reflect light and to collect backscattered and secondary electrons.

[0013] In some cases, the mirror and the electron pillar pole piece are configured to operably couple to the pressure-tight seal. The mirror may be configured to operably couple to an electron lens of the electron pole piece. Alternatively, the mirror and the intermediate element are configured to operably couple to the pressure-tight seal, and the intermediate element and the electron pillar pole piece are configured to operably couple to the pressure-tight seal. Also, the electron beam travels to a sample disposed within the chamber, and the sample generates backscattered electrons and secondary electrons in response to the electron beam.

[0014] Additionally, the mirror may be configured to reflect light from the sample to the photodetector and to reflect light from the light source to the sample. In some cases, the light source is a laser or a light emitting diode (LED). Additionally, the mirror may be configured to convert backscattered electrons to secondary electrons.

[0015] In some cases, the light guide assembly further includes a collecting electrode configured to collect secondary electrons converted from the backscattered electrons by the mirror, and the collecting electrode may include a front plate with an aperture through which the backscattered and secondary electrons travel to the mirror. The light guide assembly may also include one or more detectors configured to detect the backscattered electrons and another electrode configured to collect the secondary electrons. In particular, the one or more detectors may be solid-state diode detectors.

[0016] The above embodiments and implementations are not necessarily mutually inclusive or exclusive, and may be combined in any manner that is not inconsistent and otherwise possible, regardless of whether they are presented in association with the same or different embodiments or implementations. The description of one embodiment or implementation is not intended to be limiting with respect to other embodiments and / or implementations. Also, any one or more features, steps, operations, or techniques described elsewhere in this specification may be combined with any one or more features, steps, operations, or techniques described in the Summary of the Invention in alternative implementations. Thus, the above embodiments and implementations are illustrative rather than limiting. [Brief description of the drawings]

[0017] The above and further features will be more clearly understood from the following detailed description when read in conjunction with the accompanying drawings, in which like reference numbers indicate like structures, elements, or method steps, and the leftmost digit of the reference number indicates the number of the figure in which the referenced element first appears (e.g., element 110 first appears in FIG. 1). However, all of these conventions are intended to be exemplary or illustrative rather than limiting. [Figure 1] FIG. 1 is a simplified diagram of one embodiment of a scanning electron microscope in communication with a computer. [Diagram 2] FIG. 2 is a simplified diagram of one embodiment of the scanning electron microscope of FIG. 1 with a light guide assembly. [Figure 3A] FIG. 3A is a simplified diagram of one embodiment of a side view of the light guide assembly of FIG. 2 operating in a mode in which the mirror collects secondary electrons at pressures above about 1 millibar. [Figure 3B] FIG. 3B is a simplified diagram of one embodiment of a side view of the light guide assembly of FIG. 2 operating in a mode in which the electrodes collect secondary electrons at pressures less than about 1 millibar. [Figure 4A] FIG. 4A is a simplified diagram of one embodiment of a side view of the light guide assembly of FIG. 2 operating in a mode in which, at pressures above about 1 millibar, the mirror collects backscattered electrons and converts them into secondary electrons collected by the front plate electrode. [Figure 4B] FIG. 4B is a simplified diagram of one embodiment of a side view of the light guide assembly of FIG. 2 operating in a mode in which the mirror collects backscattered electrons and converts them into secondary electrons collected by the electrode at pressures less than about 1 millibar. [Figure 4C] FIG. 4C is a simplified diagram of one embodiment of a side view of the light guide assembly of FIG. 2 operating in a high vacuum environment in a mode in which the detector collects backscattered electrons. [Diagram 5] FIG. 5 is a simplified diagram of one embodiment of a bottom view (eg, looking toward the electron column pole piece) of the light guide assembly of FIG. 2 including one or more detectors.

[0018] Like reference numbers refer to corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] As described in more detail below, the described embodiments of the invention include a scanning electron microscope capable of Raman spectroscopy or cathodoluminescence detection. More specifically, the scanning electron microscope is configured with a light guide assembly that detects backscattered and secondary electrons at a short working distance.

[0020] FIG. 1 illustrates a simplified example of a user 101 that may interact with a computer 110 and a scanning electron microscope 120. An embodiment of the scanning electron microscope 120 may include various commercially available scanning electron microscopes. For example, the scanning electron microscope 120 may include a Quattro or Prisma scanning electron microscope available from Thermo Fisher Scientific. FIG. 1 also illustrates a network connection between the computer 110 and the scanning electron microscope 120, but it will be understood that FIG. 1 is intended to be illustrative and that additional or fewer network connections may be included. Additionally, network connections between elements may include "direct" transmission of wired or wireless data (e.g., represented by lightning bolts) or "indirect" communication via other devices (e.g., switches, routers, controllers, computers, etc.). Thus, the example of FIG. 1 should not be considered limiting.

[0021] Computer 110 may include any type of computing platform, such as a workstation, a personal computer, a tablet, a "smartphone," one or more servers, a compute cluster (local or remote), or other current or future computers or clusters of computers. A computer typically includes known components, such as one or more processors, an operating system, system memory, memory storage devices, input / output controllers, input / output devices, and display devices. It will also be understood that more than one implementation of computer 110 may be used to perform various operations in different embodiments, and thus the representation of computer 110 in FIG. 1 should not be considered limiting.

[0022] In some embodiments, computer 110 may employ a computer program product comprising a computer usable medium having control logic (e.g., a computer software program including program code) stored therein. The control logic, when executed by a processor, causes the processor to perform some or all of the functions described herein. In other embodiments, some functions are implemented primarily in hardware, for example, using a hardware state machine. The implementation of a hardware state machine to perform the functions described herein will be apparent to one of ordinary skill in the art. In the same or other embodiments, computer 110 may employ an Internet client, which may include a dedicated software application enabled to access remote information over a network. The network may include one or more of various types of networks known to those skilled in the art. For example, the network may include a local or wide area network that may employ what is commonly referred to as the TCP / IP protocol suite to communicate. The network may include a worldwide system of interconnected computer networks commonly referred to as the Internet, or may include various intranet architectures. Those skilled in the art will also appreciate that some users in networked environments may prefer to employ what is commonly referred to as a "firewall" (also referred to as a packet filter, or boundary protection device) to control information traffic entering and leaving their hardware and / or software systems. For example, a firewall may include hardware or software elements, or a combination thereof, and is typically designed to enforce security policies established by a user, such as, for example, a network administrator.

[0023] As described herein, embodiments of the present invention include a scanning electron microscope configured with a light guide assembly with a mirror constructed from PLA to collect backscattered and secondary electrons at a short working distance.

[0024] FIG. 2 illustrates an example embodiment of a scanning electron microscope 120 that includes a chamber 203 and an electron column pole piece 202. An embodiment of the electron column pole piece 202 may include any type of electron column pole piece (sometimes referred to as an electron column or pole piece) typically found in embodiments of a scanning electron microscope 120, and generally includes elements such as one or more coils and / or one or more electromagnetic lenses, such as a final lens 206, that focus an electron beam 207 from an electron source 204. It will also be understood that FIG. 2 is for illustrative purposes and should not be considered limiting. For example, while FIG. 2 illustrates the final lens 206 as being elliptical, electromagnetic lenses include a variety of configurations and shapes.

[0025] The environment within the chamber 203 may include a high vacuum environment, although as discussed above, it may be desirable for the chamber 203 to operate in a low vacuum or ESEM environment. For example, the chamber 203 may include a pressure of about 1 mbar, sufficient to remove charge from the surface of a non-conductive sample irradiated by the electron beam. In some cases, the chamber 203 may have a pressure substantially equal to about 6 mbar of water vapor that may be used in combination with an embodiment of the sample holder 210 with cooling capabilities to achieve water equilibrium pressure (100% relative humidity). The chamber 203 may have a pressure of up to about 40 mbar to achieve water vapor equilibrium pressure at room temperature of about 25° C. or greater. However, it is understood that the water equilibrium pressure is dependent on the temperature of the environment, and different pressures may be used.

[0026] The sample holder 210 is typically used to position the sample 211 in the path of the electron beam 207 as well as in the field of view of the mirror 220. It will be appreciated by those skilled in the art that the sample 211 may include any type of sample, such as, for example, a biological sample. FIG. 2 also shows an example of a light guide assembly 250 including a mirror 220 with a pressure-limiting aperture 225 positioned to allow the electron beam 207 to pass through. Those skilled in the art will appreciate that an ESEM microscope typically uses two pressure-limiting apertures. For example, one pressure-limiting aperture may be positioned inside the objective lens (e.g., the final lens 206) with a smaller diameter that has a weaker effect on the field of view, and another pressure-limiting aperture, such as the pressure-limiting aperture 225, may be positioned closer to the sample and in a position that limits the field of view. Thus, the diameter of the pressure-limiting aperture 225 is optimized for a good orientation of the field of view for the sample 211 at lower magnification. In the embodiments described herein, the diameter of the pressure-limiting aperture 225 is small enough to maintain a pressure differential between the chamber 203 and the environment containing the electron source 205. For example, the diameter of the pressure-limiting aperture 225 can range from 500 μm to 1 mm, but is typically greater than about 300 μm. As described above, the pressure in the chamber 203 may include a low vacuum pressure of about 30 mbar separated by the pressure-limiting aperture 225 from the environment containing the electron source 205, which may include a high vacuum pressure of less than about 0.1 mbar (e.g., to limit the degree of electron scattering that occurs at low vacuum pressures). In the examples described herein, the vacuum pressure may be maintained using well-known techniques (e.g., vacuum pumps, etc.).

[0027] In the embodiments described herein, the mirror 220 of the light guide assembly 250 is coupled to the electron pillar pole piece 202 with a pressure-tight seal. In some cases, the light guide assembly 250 is coupled to the final lens 206 of the electron pillar pole piece 202 with a pressure-tight seal. Also, in some embodiments, the formation of a pressure-tight seal can be improved by using an intermediate element 230 constructed of a desired material and configured to interfere with the electron pillar pole piece 202 or the final lens 206 and the mirror 220 without a gap (e.g., there is a pressure-tight seal between the mirror 220 and the intermediate element 230, and between the intermediate element 230 and the electron pillar pole piece 202 or the final lens 206). Also, in some embodiments, the pressure-limiting aperture 225 may be associated with the intermediate element 230 rather than the mirror 220, although it is desirable to position the pressure-limiting aperture 225 as close as possible to the sample 211 in order to shorten the path of the electron beam 207 in the chamber 203 environment. For example, the intermediate element 230 may be constructed of a non-magnetic material so as not to be degraded by the electron beam 207. When mirror 220 is biased with a charge, intermediate element 230 provides galvanic isolation (e.g., isolation to prevent current flow) between mirror 220 and the objective lens of pole piece 204. In some cases, light guide assembly 250 may be configured to provide galvanic isolation. In the example described here, intermediate element 230 is not illuminated by electron beam 207, which could charge intermediate element 230 and degrade the quality of electron beam 207.

[0028] Also, as mentioned above, it is important in the present invention to keep the working distance between the electron column pole piece 202 and the sample 211 as short as possible to limit beam divergence, but with sufficient distance from the detection element to anticipate the formation of what is called "cascade amplification" of secondary electrons. For example, "cascade amplification" may occur in an operating mode in which water vapor is present. Secondary electrons interact with water molecules to generate additional secondary electrons, which in turn interact with adjacent water molecules to generate more secondary electrons, thereby "amplifying" the number of secondary electrons. However, it will be understood that water vapor is not required for cascade amplification to occur. As mentioned above, it is highly desirable to optimally position the sample holder 210 close to the light guide assembly 250. For example, in a low vacuum environment, the desired working distance between the pressure limiting aperture 225 and the sample 211 may include a distance in the range of about 10-20 mm.

[0029] FIG. 2 also illustrates a light source 255, which may include any type of light source (e.g., laser, LED, or other type of light source) known to those of skill in the art for Raman spectroscopy. Similarly, FIG. 2 illustrates a detector 257, which may include any type of detector (e.g., CCD, photomultiplier, or other type of detector) known to those of skill in the art for Raman spectroscopy. It will be understood that typically, various optical elements known to those of skill in the art can direct the light along an optical path 260 between the light source 255 / detector 257 and the sample 211 via mirror 220 (not shown, e.g., mirrors, beam conditioning elements, and / or lenses) and can adjust the properties of the light to obtain the desired Raman spectroscopic performance.

[0030] FIG. 3A shows an example of a side view of a light guide assembly 250 with a mirror 220 that functions as a gas secondary electron detector (GSED) and collects secondary electrons 305 emitted from the surface of the sample 211 in response to the electron beam 207 when the scanning electron microscope 120 operates in a mode where the pressure in the chamber 203 is higher than about 1-2 mbar. For example, the electron beam 207 includes primary electrons that interact with the surface of the sample 211 to generate secondary electrons 305 that move away from the sample 211 and towards the mirror 220, which has a positive charge (e.g., a positive bias of about 600 V) in the operating mode. In this example, the electrode 330 and / or the front plate 315 may include a substantially neutral charge (the front plate 315 may include a very small positive bias) so that the secondary electrons move efficiently to the mirror 220.

[0031] FIG. 3B shows an example of a side view of the light guide assembly 250 when the scanning electron microscope 120 is operated in a mode in which the chamber 203 includes a pressure of less than 1 mbar. For example, the chamber 203 may include a pressure of about 0.5 mbar, and it may be desirable to increase the distance between the sample 211 and the detector to generate a larger signal with cascade amplification. In such a mode, the secondary electrons 305 are not collected by the mirror 220, but rather the secondary electrons 305 are collected and detected by an electrode 330 that is positively biased instead of the mirror 220, which includes a substantially neutral bias (which may include a very small negative bias). In the example described here, the electrode 330 may be positioned some distance from the mirror 220, which provides additional time and space for the cascade amplification to occur. Additionally, the light guide assembly 250 may include a front plate 315 that includes a substantially neutral bias (which may include a very small negative bias) with an aperture 317 through which the secondary electrons 305 from the electron beam 207 and the sample 211 pass.

[0032] 4A shows an example of a side view of the light guide assembly 250 when the scanning electron microscope 120 is operated in a mode where the mirror 220 serves as a conversion electrode for backscattered electrons 309 and the pressure in the chamber 203 is greater than about 1 millibar. For example, the backscattered electrons 309 are collected by the mirror 220, which has a negative bias and generates converted secondary electrons 305 by a known process that are released from the mirror 220. The converted secondary electrons 305' are then collected and detected by the front plate 315, which serves as a gas backscatter detector (GBSD) collection electrode (e.g., substantially neutrally biased, but may include a very small negative bias). In the example shown in FIG. 4A, the electrode 330 may include a negative bias.

[0033] 4B shows an example of a side view of light guide assembly 250 when scanning electron microscope 120 is operated in a mode in which chamber 203 includes a pressure of less than about 1 millibar. Similar to the embodiment of FIG. 3B, chamber 203 desirably uses cascade amplification to generate a larger signal, so that converted secondary electrons 305′ are collected and detected by electrode 330 having a substantially positive bias (e.g., mirror 220 may include a substantially negative bias and front plate 315 may include a substantially neutral bias, which is a very small negative bias).

[0034] In both the embodiments of Figures 4A and 4B, the converted secondary electrons 305' may be further amplified by the cascade amplification of the internal environment of the light guide assembly 250. For example, the internal environment of the light guide assembly 250 may be substantially the same as the environment in the chamber 203 and may be relatively humid (e.g., about 100% RH) when operated in ESEM mode. Thus, the number of converted secondary electrons 305' traveling from the mirror 220 to the front plate 315 (as in Figure 4A) or the electrode 330 (as in Figure 4B) is increased by the cascade amplification of the internal environment of the light guide assembly 250.

[0035] In some embodiments, as shown in the example of FIG. 4C, the backscattered electrons 309 can be detected by a detector 320, which may include any type of detector known, such as, for example, what are called solid-state detectors. This is desirable in situations where the pressure in the chamber 203 and in the light guide assembly 250 is not sufficient for amplification between the mirror 220 and the front plate 315, and / or in high vacuum conditions. It can also be understood that there are more than one embodiment of the detector 320 located on the light guide assembly 250, such as the two embodiments shown in FIG. 5, which are viewed from the bottom of the light guide assembly 250 (e.g., looking toward the electron column pole piece 202 without the front plate 315). In particular, the implementation of the detector 320 may be located laterally with respect to the mirror 220, such that the path of the secondary electrons 305 and / or the backscattered electrons 309 from the sample 211 to the mirror 220 is not blocked by the detector 320. It is also desirable to locate the detector 320 at a distance above the front plate 315 to increase the efficiency of collection of the backscattered electrons 309.

[0036] It will also be appreciated that in some embodiments, the pressure in the chamber 203 may vary, from higher or lower pressure in the operating modes as described in Figures 3A-B, 4A-C, and 5. In some cases, pressure variations may affect performance, but may also provide other benefits and are therefore considered to be within the scope of the described invention. Additionally, while in the example of Figure 5, the mirror 220 is shown as being substantially elliptical, the mirror 220 may include any shape that effectively directs light from the light source 255 to the sample 211. It is also important that the shape of the mirror 220 is effective to collect and direct light (e.g., Raman emission or cathodoluminescence) from the sample 211 to the detector 257. Additionally, it is desirable for the working distance in the light guide assembly 250 to be as short as possible. Thus, it will be appreciated that the embodiments of Figures 2, 3A-B, 4A-C, and 5 are for illustrative purposes and should not be considered limiting.

[0037] While various embodiments and implementations have been described, it should be understood by those skilled in the art that the foregoing are merely illustrative, not limiting, and are presented by way of example only. Many other schemes for distributing functionality among the various functional elements of the illustrated embodiments are possible. The functionality of any element may be performed in various ways in alternative embodiments.

Claims

1. 1. A light guide assembly for an electron microscope system, comprising: a light guide assembly having one or more detectors and a mirror including a pressure limiting aperture through which an electron beam from an electron source passes; Equipped with the mirror is configured to reflect light to collect backscattered electrons and secondary electrons and convert the backscattered electrons to secondary electrons; the mirror is configured to reflect light from the sample to a photodetector; The mirror is configured to reflect light from a light source to the sample.

2. A light guide assembly for an electron microscope system, comprising: a light guide assembly having one or more detectors and a mirror including a pressure limiting aperture through which an electron beam from an electron source passes; Equipped with the mirror is configured to reflect light to collect backscattered electrons and secondary electrons and convert the backscattered electrons to secondary electrons; the light guide assembly further comprising a collector electrode configured to collect the converted secondary electrons. Light guide assembly.

3. the collecting electrode includes a front plate, the front plate having an aperture through which the backscattered electrons and the secondary electrons travel to the mirror; The light guide assembly of claim 2 .

4. the light guide assembly further comprising an electrode configured to collect secondary electrons; The light guide assembly of claim 1 .

5. the one or more detectors are configured to detect backscattered electrons. A light guide assembly according to any one of the preceding claims.

6. The one or more detectors comprise one or more solid state diode detectors. The light guide assembly of claim 5 .

7. Electronic pole pieces, and A light guide assembly according to any one of claims 1 to 6, operably coupled to said electronic pole piece. Equipped with Electron microscope system.

8. a chamber having a low vacuum environment, the electron pole piece and the light guide assembly being disposed within the chamber; 8. The electron microscope system according to claim 7.

9. the electron beam travels to a sample disposed within the chamber; the sample generates the backscattered electrons and the secondary electrons in response to the electron beam. The electron microscope system according to claim 8 .

10. the light guide assembly is operably coupled to a final lens of the electronic pole piece; 10. The electron microscope system according to claim 7.

11. the light guide assembly and the electronic pole piece are configured to be operably coupled with a pressure resistant seal; The electron microscope system according to any one of claims 7 to 10.

12. the mirror provides the pressure tight seal to the electronic pole piece; The electron microscope system according to claim 11.

13. the light guide assembly and intermediate element are configured to be operatively coupled to the pressure resistant seal; the intermediate element and the electronic pole piece are configured to be operatively coupled with the pressure resistant seal. The electron microscope system according to claim 11.

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