Patent Publication Number: US-2022238301-A1

Title: Electron detector

Description:
TECHNICAL FIELD 
     The present invention relates to an electron detector. 
     BACKGROUND ART 
     Advancements in electron optics and automation are among the key factors that have enabled Transmission Electron Microscopy (TEM) to achieve near-atomic and sub-atomic resolution in structural biology and materials science, respectively. However, the most demanding applications are always pushing technology to advance further. While electron sources are brighter and electromagnetic lenses are more stable, aberration corrected detectors remain an area for improvement. 
     Hybrid pixel sensors are known for photon detection. However hybrid pixel sensors may also be used for electron counting, see “Electronic detectors for electron microscopy”, A. R. Faruqi and R. Henderson, Quarterly Review Biophysics, 2011 August, 44(3): 357-90. 
     DISCLOSURE OF THE INVENTION 
     It is a general object of the invention to provide a detector applicable for electron microscopy. 
     The electron detector according to the present invention comprises a sensor module comprising a sensor for detecting electrons, and an electronics module comprising circuitry for processing signals received from the sensor module. Wiring electrically connects the sensor module to the electronics module. An adaptor is arranged between the sensor module and the electronics module. The adaptor comprises a passage for the wiring, and shielding elements for shielding radiation. 
     By using the adaptor as proposed, a detector can be built that may use many components used in non-electron detector applications, such as in photon detection. The set-up of the present electron detector allows multiple components of a different detector detecting or counting photons to be re-used or manufactured as multi-use components for either variety or type of detector. 
     The sensor for detecting electrons preferably is a sensor applicable in electron microscopy applications, and preferably in transmission electron microscopy (TEM) applications or scanning TEM applications. Accordingly, in one embodiment, the electron detector may be arranged in combination with an electron source, electron optics and a vacuum system. 
     In one embodiment, the sensor for detecting electrons is a semiconductor-based sensor that relies on semiconductor materials, such as silicon, or high-Z, materials such as CdTe, GaAs, Diamond, Ge or CdZnTe to measure the effect of incident electrons. In such a semiconductor-based sensor, the semiconductor detection material is typically arranged between two electrodes. Incident electrons may be directly sensed without conversion to photons, typically via charge carriers released by the impinging electron. In a preferred embodiment of a semiconductor electron sensor, the sensor is a hybrid pixel sensor comprising a sensor and a readout chip, where the sensor electrodes are patterned such as to match a pixelated array of readout electronics connected via an array of contacts (e.g., bump bonds). Different technologies may be used for the semiconductor sensor and the readout chips, allowing separate optimizations. The sensor may be used in diffraction as well as in imaging mode. 
     Given that e.g. a semiconductor-based sensor such as a hybrid pixel sensor may also be used in a different application such as radiation detection, in particular x-ray detection, it is desired to make such sensor, once developed, a multi-use sensor also usable in an electron detector for electron sensing. While for both, radiation sensing and electron sensing, the detector not only comprises the sensor but also further electronics, mechanics etc. it is desired to make also these components once developed multi-use components or redesign with only little amendments or adaptations, in particular when it comes to the design and mechanical functionality of the components. 
     Sensing in electron microscopy requires a vacuum for the sensor to be arranged in given that electrons are least scattered in vacuum. In addition, the electronics module is desired to be located outside the vacuum in order to improve vacuum conditions by preventing outgassing from the electronics module contaminating the vacuum. 
     On the other hand, electron beams as primary radiation may generate secondary radiation such as x-rays or lower energy electrons which is desired to be blocked from irradiating a user and/or from impacting the electronics module. Euratom safety requirements are desired to be met. 
     Hence, electron detection specific elements are preferably embodied in the adaptor, and/or can be assembled to the adaptor. Of course, other components such as the electronics module may include different functionality in electron sensing compared to photon sensing. However, such different functionality may manifest in different logic or software or electrical components on a printed circuit board, which not necessarily may require a change in the design of the component. In particular the footprint and/or dimensions e.g. of the electronics module and/or other electronics, an optional housing of the detector, and/or other mechanical components may remain the same as for other kinds of detectors. As a result, various detectors detecting different parameters, such as radiation versus electrons, can be manufactured in a modular way including multi-use components that may be applied in different detectors. 
     The adaptor not only is arranged between the sensor module and the electronics modules, but preferably also mechanically connects the sensor module and the electronics module. Hence, the adaptor supports the sensor module. For this reason, the adaptor preferably comprises a support portion, while the sensor module preferably comprises a support for the actual sensor, such that the support portion of the adaptor and the support of the sensor module are mechanically linked, e.g. by means of gluing, screwing, or other means. The same may be true for the electronics module and the adaptor. The adaptor may support the electronics module. For this purpose, the adaptor may comprise a mechanical interface such as a nose-piece coupled to a platform of the electronics module, by means of gluing, screwing, or other coupling means. Preferably, the electronics module comprises circuitry preferably arranged on a printed circuit board, including but not limited to Integrated Circuits (ICs), capacitors or resistors. In one example, the platform has the shape of a frame and two printed circuit boards supporting the circuitry are mounted on different sides of the platform. In a different embodiment, the platform supporting the circuitry may be formed integral with the adaptor. 
     The electronics module may preferably take the form of a plate with a main extension in a horizontal plane, and a rather low thickness. In one example, the sensor module may show a main extension in a vertical plane, i.e. orthogonal to the extension of the electronics module. 
     A combination of the electronics module, the adaptor and the sensor module is also referred to as unit. Such unit may be pre-assembled from an individual sensor module, an electronics module and an adaptor, which unit may be introduced in a housing or chassis of the electron detector, e.g. by sliding. For this purpose, the electronics module, in particular its platform, may contain guides that co-operate with rails or other guides at the inner surface of the housing. 
     Wiring is provided for electrically connecting the sensor module to the electronics module. Preferably, the wiring is supported by a flexible carrier, such as a flexible printed circuit board which may additionally support additional components such as ICs in one embodiment. In a different embodiment, the wiring is embodied as one of a ribbon cable, a flexible flat cable, a flat connector or a similar connection. 
     The adaptor shows a first mechanical interface for mechanically connecting to the electronics module, e.g. in form of a nose piece, and a second mechanical interface for connecting to the sensor module. However, given that a body of the adaptor extends between the electronics module and the sensor module, a certain path needs to be overcome by the wiring when connecting the sensor module to the electronics module. And, the wiring needs to overcome a sealing portion of the adaptor, which will be introduced in more detail later. For this reason, the adaptor has one or more passages for the wiring to reach through from its way from the sensor module to the electronics module. Such passage may in a first embodiment be represented as a through-hole in the body of the adaptor, and specifically in the sealing portion. In a different embodiment, the passage may rather be a recess in the body of the adaptor, which recess is open in one direction. 
     In one embodiment of the invention, the adaptor comprises a beam portion between the sealing portion and the support portion. The beam portion preferably shows a cross section smaller than a cross section of the sealing portion, and the wiring or its carrier may be deposited on a surface of the beam portion, e.g. by gluing. Given that in such scenario the sealing portion exceeds the beam portion in height, it is preferred that the one or more passages are arranged in the sealing portion such that a bottom of the passages is co-planar with e.g. a top surface of the beam portion, and/or is co-planar with the printed circuit board/s of the electronics module. In such embodiment, the wiring and its carrier/s may pass the passage without being bent too much. An offset of up to +/−0.5 mm between the bottom of the passage and the top of the beam portion and/or the circuitry may be acceptable in one embodiment. The wiring may be soldered to the circuitry of the electronics module, or be connected thereto by means of a connector, and be soldered to the sensor or circuitry connected upstream to the sensor, or be connected thereto by means of a connector. 
     The sealing portion of the adaptor preferably has a main planar extension orthogonal to the main extension of the electronics module. This results from the sealing portion being responsible for, preferably together with other components such as the sealing plate introduced below, sealing one or more openings of the housing through which the one or more units are inserted and extend into the housing. Hence, the sealing portion of the adaptor preferably comprises a mechanical interface facing the housing when being mounted in/to the housing. This interface preferably includes a recess for an O-ring seal, or for any other sealing means, and/or preferably includes means for mounting the sealing portion to a flange of the housing, and/or to a sealing plate. 
     Given that the sensor module is configured to detect electrons, the sensor module preferably is operated in vacuum conditions. Hence, a domain of the sensor module, i.e. the space around the sensor module preferably is under vacuum, at least when the detector is operated. In order to provide a space that can be evacuated, components of the detector, such as the flange to be introduced later on, and components outside the detector, such as an electron source of an electron microscope may contribute to encapsulating this space also referred to as sensor module domain. Instead, an inside of the housing of the detector does not need to be operated under vacuum. For this reason, a vacuum in the sensor module domain is to be sealed from the electronics module, i.e. the inside of the housing of the detector, also referred to as electronics module domain. Hence, an opening in the housing preferably is vacuum sealed versus the sensor module domain. The vacuum seal may in one embodiment comprise a separate sealing plate to be mounted to the housing, e.g. to a flange of the housing surrounding the opening in the housing. Such sealing plate preferably is made from a gas tight material, and is sealing mounted to the housing. The sealing plate preferably has one opening per unit for introducing the respective unit into the housing of the detector. The sealing portion of the adaptor in turn seals the opening in the sealing plate. For this purpose, the adaptor seals the opening e.g. by means of a sealing ring attached to the interface of the sealing portion of the adaptor. Hence, the sealing portion of the adaptor, preferably in combination with the sealing plate, separates the sensor module domain from the electronics modules domain. 
     Preferably, the or each passage in the adaptor is sealed by means of a sealing compound, preferably an epoxy. The sealing compound, however, may be applied prior to the unit entering the housing, however, after having mounted the wiring. The sealing compound is gas tight, such that no gas may enter the sensor module domain from the non-vacuum electronics module domain. 
     The adaptor preferably comprises shielding elements for supporting shielding. Preferably, secondary radiation, and in particular x-rays present in the sensor module domain, shall remain confined therein in order not to expose a user and guarantee the safety of the user. On the other hand, it may also be beneficial to shield the electronics module from radiation present in the sensor module domain. “Supporting shielding” may express that additional means, such as a shielding plate to be introduced later on, may in combination with the adaptor provide for the shielding. “Shielding” may not only include a full barrier as to the radiation in question, but also includes lowering the transmitted radiation to allowed, certified levels. In the sensor module domain x-ray radiation may be effected during measurements in response to bremsstrahlung generated by the electrons. 
     Given that the adaptor may be of a material to absorb primary or secondary radiation, a certain path length is required in such material which would lead to an adaptor with extended dimensions. For this reason, shielding elements are introduced into the body of the adaptor, which shielding means decreased a range for primary or secondary radiation entering from the sensor module domain. The shielding elements are preferably highly absorbing to primary or secondary radiation and are preferably made from one of tungsten, lead, tantalum, molybdenum. In a different embodiment these materials may be comprised in the shielding element together with other materials. In one example, Inermet® may be used which is a tungsten, copper zinc alloy. In view of effort and costs, it is not envisaged to manufacture the entire body of the adaptor or the shielding portion from the primary or secondary radiation absorbing material, but only individual shielding elements that are arranged in the sealing portion. While the shielding elements generally may take any shape, it is preferred that the shielding elements are prefabricated inserts that are inserted in holes drilled in the body. Preferably, the inserts show a straight, longitudinal extension, preferably with a circular cross section. 
     With the intent to reduce the path for primary or secondary radiation in the body of the adaptor and at the same time keeping a width of the sealing portion of the adaptor small, the inserts are preferably arranged at different positions along a width of the sealing portion. Preferably, the width of the sealing portion is less than 3 cm. 
     In order to further reduce the generation of regular structures which might cause the formation of radiation leakage paths and hence enhance the absorption of the primary or secondary radiation in the material of the body, the rods preferably show two or more different diameters: E.g., a first and a second one, the first one exceeding the second one. By such means, the rods can be arranged close to each other, in particular rods of different diameters at different width positions of the sealing plate, thereby improving the shielding. In addition, the thickness of the sealing portion of the adaptor may be minimized. Preferably, the rods are arranged in the sealing portion such that no line of sight is allowed through the sealing portion. Preferably, the rods support absorbing the primary or secondary radiation. 
     Given that the sealing portion of the adaptor is penetrated by the one or more passages, at least one, and preferably more of the inserts extend into the passage, and preferably bridge the passage. This is preferred since outside the body of the sealing portion, i.e. in the one or more passages, the primary or secondary radiation needs to be shielded as inside the body. In such embodiment, the wiring may pass through the passage between two or more of the inserts or between an insert and a wall defining the passage. In such arrangement of the wiring, its carrier is preferred to be flexible. Preferably, the carrier is S-shaped when meandering the rods in the passage. The rods exposed in the passage may prevent the sealing compound from escaping. 
     Accordingly, the adaptor, and in particular the sealing portion of the adaptor not only contributes to a vacuum seal but also supports for absorbing additional primary or secondary radiation where secondary radiation is generated in the vacuum sensor module domain during electron interaction. The latter may also be achieved in combination with one or more shielding plates arranged in the sensor module domain. For example, a shielding plate may be arranged in the sensor module domain between the sealing portion of the adaptor, and its support portion. Accordingly, the shielding plate comprises an opening for the adaptor to reach through and preferably an opening per adaptor, and in particular for the beam portion of each adaptor to reach through. 
     In an embodiment, a flange is integrated in the sealing plate, for attaching the detector to other components, such as an electron source co-defining the vacuum sensor module domain may be attached to the flange. A shield may be inserted into the sealing plate to support shielding in combination with the sealing portion of the adaptor and the shielding plate. The shield and the shielding plate if any are preferably strongly absorbing primary or secondary radiation and are preferably made from one of tungsten, lead, tantalum, molybdenum. In a different embodiment these materials may be comprised in the shielding element together with another material. E.g. Inermet® may be used. 
     In another embodiment, the shielding elements such as the rods may also comprise borated alloys to shield neutron radiation in further applications. 
     A third function of the adaptor preferably is cooling. Heat generated by the sensor module or in the sensor module domain, or in the electronics module or the electronics module domain may be transferred via the adaptor to the housing of the electron detector, or to the platform of the electronics module. For this reason, it is preferred that the adaptor is made from or comprises a thermally conducting material, such as metal. In addition, the platform of the electronics modules preferably is made from or comprises a thermally conducting material, such as metal, as well as the support of the sensor module. 
     The number of units per detector is not limited to one. Instead, any other number of units may be arranged in the common housing. The housing preferably comprises individual openings per unit in a common face of the housing. In a preferred embodiment, the sensor module, and possibly also the adaptor are shaped such that another sensor module with adaptor can be arranged on each of its sides in order to build a larger sensor array out of individual unit. For this purpose, it is preferred that the sensor module and at least the sealing plate of the adaptor are of rectangular cross section, such that they abut when being arranged next to each other to contribute to a large sensor array. 
     After the units being mounted to the housing all the electronics modules are arranged inside the housing, while all the sensor modules are located outside, and preferably are arranged in a common sensor module domain. In case of a single sealing plate provided for all units, the sealing plate preferably comprises one opening per adaptor. In such manner, the individual units may easily be inserted into the assigned opening and be mounted to the sealing plate. The assembly including the units mounted to the sealing plate may then be mounted to the housing of the detector. Also in case of one or more shielding plates, it is preferred that each shielding plate is a single shielding plate shielding all the electronic modules, and each shielding plate preferably comprises one opening per adaptor. 
     According to another aspect of the present invention, an adaptor is provided with a first mechanical interface for connecting to a sensor module comprising a sensor for detecting electrons, and a second mechanical interface for connecting to an electronics module comprising circuitry for processing signals received from the sensor module. Shielding elements are configured to shield a domain determined by the second mechanical interface from radiation incident from a domain defined by the first mechanical interface. A passage is provided and configured to allow wiring for electrically connecting the sensor module to the electronics module to pass the adaptor. 
     All of the above embodiments of the electron detector shall also be disclosed in connection with the bare adaptor claimed in this aspect of the present invention. 
     According to another aspect of the invention, a detector including shielding and sealing means between the sensor module domain and the electronics module domain, and including an adaptor between the sensor module and the electronics module, may also be used for one of: 
     x-ray detection; 
     gamma radiation shielding; 
     neutron detection; 
     neutron secondary radiation protection; 
     proton detection, alpha detection. 
     According sensors sensitive to the kind of radiation to be detected are used in the corresponding sensor module instead of the electron sensor used in the electron detector according to the previous aspects of the present invention, and the shielding materials are replaced by materials absorbing the corresponding primary or secondary radiation. All other components may remain as is described in connection with electron detection. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. This description makes reference to the annexed drawings, wherein the figures show: 
         FIG. 1  an electron detector according to an embodiment of the invention, in a perspective side view, 
         FIG. 2  the electron detector of  FIG. 1  in an exploded view, 
         FIG. 3  a unit of an electron detector according an embodiment of the present invention, in a first perspective view, 
         FIG. 4  the unit of  FIG. 3  in a second perspective view, 
         FIG. 5  the unit of  FIG. 3  in a third perspective view, 
         FIG. 6  the unit of  FIG. 3  in a perspective open cut view, 
         FIG. 7  an electron detector according to an embodiment of the invention, in a perspective exploded view, 
         FIG. 8  an electron detector according to an embodiment of the invention, in a perspective exploded view, 
         FIG. 9  an electron detector according to an embodiment of the invention, in a perspective exploded view, 
         FIG. 10  the electron detector of  FIG. 1  or  FIG. 8  in a perspective side view, 
         FIG. 11  an electron detector according to an embodiment of the invention, in a perspective open cut view. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
       FIG. 1  shows a perspective side view of an electron detector according to an embodiment of the invention. The electron detector comprises a housing  6  and one or more connectors  10  for supplying the detector with power and/or for data transmission. One of the front ends of the housing  6  is covered by a vacuum sealing plate  5 . A shielding plate  9  is attached to the sealing plate  5 . 
     Two units are arranged to a large extent inside the housing  6 . Each unit comprises a sensor module  1  visible in  FIG. 1  and reaches through an opening  91  in the shielding plate  9  and through an opening in the sealing plate  5  (not visible). Next to the sensor module  1  each unit comprises an adaptor  3  mechanically and elects connecting the sensor module  1  to an electronics module (not visible) arranged inside the housing  6 . 
     The sensor modules  1  are configured to detect electrons. Hence, the detector is an electron detector such as used in electron microscopy applications. Given that electrons approaching the sensor modules  1  may generate secondary radiation, it is desired to prevent such radiation from escaping from a sensor module domain SMD and hence to prevent a user of the detector from being exposed to the radiation, and preferably to shield the electronics modules in the housing  6  from such radiation. The shielding plate  9  is arranged and configured to contribute to such shielding function. The shielding plate  9  is arranged in the sensor module domain SMD. In contrast, a domain inside the housing  6  is also referred to as electronics module domain EMD. As to the material, it is preferred that the shielding plate  9  comprises or consists of an x-ray and electron shielding material, such as tungsten. 
     In addition, for the sensor module  1  to properly work it is preferably arranged in a vacuum. Hence, the electron detector as shown in  FIG. 1  may be mounted, e.g. by means of a flange comprised in the sealing plate  5 , to an electron source. The resulting confined space is evacuated, such that the sensor module domain SMD is under vacuum at least during operation of the electron detector. On the other hand, the inside of the housing  6  of the electron detector is not required to be evacuated, but typically is operated under atmospheric conditions. For this reason, the electron detector comprises a vacuum seal for separating the vacuum sensor module domain SMD from the non-vacuum electronics module domain EMD. The sealing plate  5  contributes to such vacuum seal and acts as a vacuum barrier. The sealing plate  5  is preferably mounted to the housing  6 . The units are preferably mounted to the sealing plate  5 . 
       FIG. 2  illustrates the electron detector of  FIG. 1  in an exploded view. The sealing plate  5  is drawn from the housing  6  which renders the two units U 1  and U 2  inserted in the housing  6  visible. For illustration purposes, the lower unit U 1  is drawn from the housing  6  to a lesser extent than the upper unit U 2 . Each unit U 1 , U 2  comprises the sensor module  1  and an electronics module  2 . An adaptor  3  mechanically and electrically connects the sensor module  1  to the respective electronics module  2 . Each unit U 1 , U 2  is inserted into a dedicated opening  51  in the sealing plate  5 , and is mounted to the sealing plate  5 . This assembly comprising the modules U 1  and U 2  and the sealing plate  5  is then mounted to a flange  61  of the housing  6 . 
       FIG. 3  illustrates a unit of an electron detector according to an embodiment of the present invention, in a first perspective view. Such unit may be, for example, one of the units U 1  or U 2  as shown in  FIG. 2 . 
     The unit comprises a sensor module  1  connected to an electronics module  2  via an adaptor  3 . The electronics module  2  presently comprises a platform  23 , e.g. in the form of a frame, which platform  23  presently supports two printed circuit boards  21  and  22 . Given that the printed circuit boards  21  and  22  each carry electrical and/or electronics collectively referred to as circuitry, reference numerals  21  and  22  are also used to denote circuitry of the electronics module  2  in general. A back end of the electronics module  2  carries sockets and/or other electrical connectors  24 , e.g. for connecting to further circuits or wiring in the electron detector housing, and/or for receiving power supply e.g. via the connector/s  10 , see  FIG. 1 . 
     The platform  23  of the electronics module  2  is attached to the adaptor  3 , e.g. to a nose-piece  31  of the adaptor  3 , and hence mechanically connected, e.g. by welding, screwing, or gluing. The adaptor  3  further includes a sealing portion  32  resembling a box-like piece, and a beam portion  33  extending from the sealing portion  32 . At the end of the beam portion  33  a support portion  34  is provided in form of a plate for attaching the sensor module  1  to. The sensor module  1  comprises a support  12  attached to the support portion  34  of the adaptor  3 , and a sensor  11  attached to the support  12 . 
     Accordingly, in the present embodiment, the unit comprises the electronics module  2  primarily extending in a horizontal plane x,y, and the sensor module  1  primarily extending in a plane orthogonal to the horizontal plane x,y, i.e. in a vertical plane y,z. However, the sensor module  1  may also be oriented in a different plane if needed. As to the adaptor  3 , it is preferred that the shielding portion  32  of the adaptor  3  covers the opening in the housing  6  or the opening of a sealing plate to be introduced yet. Hence, it is preferred that a cross section of the sealing portion  32  matches or exceeds the opening in the housing  6  or the opening in the sealing plate. In addition, it is preferred that a cross section of the sealing portion  32  exceeds a cross section of the beam portion  33 . 
     The adaptor  3 , and in particular its sealing portion  32 , includes a passage  321 , and presently includes four passages  321 , three of which are visible in  FIG. 2 . The passages  321  are provided for a wiring  4  which wiring  4  electrically connects the sensor module  1  with the electronics module  2 . The wiring  4  presently is embodied on a flexible carrier, such as flexible printed circuit boards with or without components arranged on it. In a different embodiment, the wiring  4  is embodied as n ribbon cable or a similar connection. 
     As can be derived from  FIG. 3 , each of the passages  321  is built as a cut-out in the sealing plate  32  with a bottom of each cut-out being in the same plane as a top of the beam portion  33  and a top of the circuitry  21 , 22 . In a different embodiment, a step between the bottom of the passage  321  and the top of the respective aligned component is at most +/−0.5 mm. This facilitates a feed-through of the wiring  4  and its respective carrier and an electrical contact to the circuitry  21 , 22  at the same level. In the present example, the wiring carriers are sealed and held in the passages  321 , e.g. by a sealing compound, such as an epoxy. The sealing compound is configured to avoid gas, and in particular air to pass through the passages  321 . Preferably, a width of the sealing portion  32  in x-direction is dimensioned dependent on the width of the rods arrangement (see below) in x-direction required for effective primary or secondary shielding, and dependent on the extension of the sealing compound in x-direction required for effective sealing. 
     On the end of the sensor module  1 , it can be derived from  FIG. 3  that the wiring  4  is fed through further passages in the support portion  34  of the adaptor  3  and connects to the sensor  11  or to other electronics resident in the sensor module  1 . 
     The sealing portion  32  comprises shielding elements  35  in the form of rod-shaped inserts, only a diameter of which is visible in the perspective view of  FIG. 3 . As can be derived from  FIG. 3 , there are different types of rods  35  used: A first number  351  of rods with a first diameter, and a second number  352  of rods with a second diameter, the second diameter being less than the first diameter. The rods  35  are presently arranged in y-direction only, and all rods  35  are arranged in parallel to each other. The rods  35  reach through the entire body of the sealing section  32  in y-direction, from a side wall that is shown in  FIG. 3  to an opposite side wall not visible in  FIG. 3 . The rods  35  are arranged in different planes in x-direction. 
     The rods  35  are arranged and configured to prevent or reduce an impact of primary or secondary radiation on the electronics module  2 . In particular, in the application of electron microscopy electrons may generate x-ray-bremsstrahlung or lower energy electrons which may damage the electronics module  2 . The rods  35  are made from a material that absorbs primary or secondary radiation. In combination with suitably dimensioning a width of the sealing portion  32  the rods  35  are arranged such that primary or secondary radiation incident from the sensor module domain SMD are absorbed and/or scattered which decreases the range of the radiation. 
     Accordingly, in the unit shown in  FIG. 3  the adaptor  3 , and in particular its sealing portion  32  separates a sensor module domain SMD from an electronics modules domain EMD, which two domains SMD and EMD operate under different conditions. The sensor module domain SMD is assumed as vacuum domain when operating the electron detector, while the electronics module domain EMD is assumed to operate under non-vacuum conditions. Hence, the sealing portion  32  of the adaptor  3  on the one hand contributes to a vacuum seal, i.e. the material of the body of the adaptor  3  preferably is gas tight. The one or more openings  321  arranged in the sealing portion  32  are preferably sealed by a seal which may be applied e.g. in liquid or viscous form and may be hardened. Hence, the adaptor  3 , and in particular its sealing portion  32  not only shields the interior of the housing  6 , and in particular the electronics module  2 , from primary or secondary radiation, but also seals the vacuum sensor module domain SMD from the electronics module domain EMD. 
     Given that heat may be generated in the sensor module  1 , it is preferred that the adaptor  3  supports a third function in addition to primary or secondary radiation shielding and vacuum sealing, i.e. heat dissipation. For this reason, it is preferred that the body of the adaptor  3  is made from a thermally conducting maters such as metal, as is preferably made the platform  23  of the electronics module  2 , as is preferably made the support  34  portion of the sensor module  1 . Given that all these components are mechanically and thermally connected, heat may be removed from the sensor module  1  via the adaptor  3  to the platform  23  of the electronics module  2  and dissipate there when acting as a heat sink, or may be further guided to a heat sink of the housing  6 , for example. 
     Preferably, the platform  23  of the electronics module  2  comprises guides  231 . The guides  231  may cooperate with e.g. rails on an inner surface of the housing  6  such that the unit shown in  FIG. 3  can be slid into the housing. 
     A face of the sealing portion  32  of the adaptor  3  facing the electronics module  2  includes an interface  322 . Preferably, and as will be explained later on, the adaptor  3  is attached by means of this interface  322  to a sealing plate. The interface  322  presently includes a recess for accepting e.g. an O-ring as seal. 
       FIGS. 4 and 5  show the unit of  FIG. 3  in different perspective views. 
       FIG. 6  illustrates the unit of  FIG. 3  in a perspective open cut view. This view in particular illustrates the arrangement of the inserts  35  in the adaptor  3 , and in particular in the sealing portion  32  of the adaptor  3 . As can be derived from this open cut view, the inserts  35  also extend into the one or more passages  321 , and in particular bridge the one or more passages  321 . Accordingly, in the one or more passages  321  the inserts  35  pass through exposed in y-direction, while the wiring  4  passes through the passage  321  in x-direction and passes between two or more rods  35  as can be seen in  FIG. 6 . For this reason, the flexible carrier for the wiring  4  may also be bent to pass between the rods  35  or between a rod  35  and a wall defining the passage  321 . 
       FIG. 7  illustrates a perspective exploded view of an electron detector according to an embodiment of the invention. The detector resembles the detector of  FIG. 2 , however, shown from a different perspective. The units U 1  and U 2  reach through an opening  51  in a sealing n plate  5 . In this embodiment, the sealing plate  5  and the adaptor  3 , and specifically its sealing portion including the rods, contribute to the vacuum seal to be established. On the other hand, the sensor modules  1  remain exposed from the sealing plate  5  for sensing purposes. 
       FIG. 8  illustrates a perspective view of an electron detector according to an embodiment of the invention. The detector differs from the detector of  FIG. 7  in that additionally a shielding plate  9  is provided, which preferably is inserted into the sealing plate  5 . The shielding plate  9  preferably is made from a material shielding x-ray radiation, such as tungsten. Only a half of the shielding plate  9  is shown while the second half is omitted for illustration purposes solely. The shielding plate  9  has an opening  91  through which the units U 1  and U 2  reach into the housing  6 . 
       FIG. 9  shows an electron detector in a perspective exploded view, according to an embodiment of the invention. The electron detector of  FIG. 9  differs from other embodiments in that in addition to shielding plate  9  a shield  7  is provided for shielding from primary or secondary radiation. The shield  7  and the shielding plate  9  are arranged in the sensor module domain, i.e. behind or in front of the sealing portion  32  of the adaptor  3 , subject to perspective. The shield  7  is inserted in the sealing plate  5 . The shielding plate  9  is mounted onto the sealing plate  5 . Openings  91  in the shielding plate  9  provide for an exposure of the sensing modules  1 . 
     In the present embodiment, the housing  6  again comprises a flange  61  at its front end for mounting the sealing plate  5  to. Presently, the flange  61  of the housing  6  includes two openings, one per unit U 1 , U 2  to reach through. In a preassembling step, the shield  5  is inserted in the sealing plate  5 , and the units U 1  and U 2  are mounted to the sealing plate  5 . This assembly containing the sealing plate  5  is then mounted to the flange  61  of the housing  6 . Finally, the shielding plate  9  is mounted to the sealing plate  5 . 
       FIG. 10  illustrates the electron detector of  FIG. 1  or  FIG. 8  in a perspective side view. 
       FIG. 11  shows a perspective open cut and exploded view of an electron detector according to an embodiment of the invention. The present detector only comprises one unit. The sealing plate  5  is mounted to a flange  61  of the housing  6 . In addition, the sealing plate  5  shows a collar  52  surrounding the sensor module  1 . One or more shielding plates may be mounted in the sensor module domain, however, none of these is shown in  FIG. 11 . 
     While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. 
     In particular, for each embodiment, the number of units comprised in the respective detector may vary. Hence, each embodiment shall considered to be disclosed for any number of units mounted in a common housing. However, a preferred number of units for all embodiments is 1, 2, 8, 18 or 32.