CRYOGENIC SAMPLE HANDLING AND STORAGE SYSTEM

Abstract

The invention relates to a sample handling and storage system. The system is used for storing and handling samples, which may be cryogenic samples, that are arranged for use in charged particle microscopy, such as cryo-electron microscope samples for use in cryo-transmission electron microscopy. The system comprises a storage apparatus for storing a plurality of samples, and a Charged Particle Apparatus (CPA), such as a cryo-TEM, at a location remote from said storage apparatus. The system further comprises a transfer device that is releasably connectable to said storage apparatus, and that is releasably connectable to said CPA as well. As defined herein, said transfer device is arranged for acquiring a sample from said plurality of samples when connected to said storage apparatus, and arranged for transferring said sample from said transfer device to said CPA when connected to said CPA.

Claims

1. A cryogenic sample handling and storage system, comprising: A storage apparatus for storing a plurality of cryogenic samples; A Charged Particle Apparatus (CPA) at a location remote from said storage apparatus; and A transfer device that is releasably connectable to said storage apparatus and said CPA, said transfer device comprising: a transfer mechanism that is arranged for acquiring said cryogenic sample from said storage apparatus when connected to said storage apparatus, and for delivering said cryogenic sample to said CPA when connected to said CPA; an elongated housing, wherein an internal volume defined by said elongated housing at least partly comprises an internal transfer room for storing said cryogenic sample during transport of said transfer device; and a heat shield provided within said internal transfer room for keeping said cryogenic sample at cryogenic temperatures during transport of said transfer device.

2. Cryogenic sample handling and storage system according to claim 1, wherein said heat shield is movably provided within said internal transfer room.

3. Cryogenic sample handling and storage system according to claim 2, wherein said heat shield is movable from a first position wherein said heat shield is located within said internal transfer room to a second position wherein at least part of said heat shield is located outside of said elongated housing.

4. Cryogenic sample handling and storage system according to claim 3, wherein said transfer device comprises a transfer port provided in said elongated housing, wherein said heat shield is arranged to move through said transfer port when moving from said first position to said second position.

5. Cryogenic sample handling and storage system according to claim 3, wherein said cryogenic sample handling and storage system is arranged for connecting said transfer device to said storage apparatus, and moving said heat shield to said second position.

6. Cryogenic sample handling system according to claim 5, wherein said storage apparatus comprises a cooling mechanism for cooling said heat shield in said second position thereof.

7. Cryogenic sample handling system according to claim 6, wherein said cooling mechanism comprises a bath of liquid coolant, such as liquid nitrogen.

8. Cryogenic sample handling and storage system according to claims 1-7, wherein said heat shield comprises at least part of a hollow cylinder.

9. Cryogenic sample handling and storage system according to claims 1-8, wherein said transfer mechanism comprises a gripper that is arranged for gripping said cryogenic sample.

10. Cryogenic sample handling and storage system according to claim 9, wherein said gripper is movable from a first gripper position to a second gripper position, wherein in said first gripper position said gripper is located within said internal transfer room and wherein in said second position said gripper is located outside of said elongated housing.

11. Cryogenic sample handling and storage system according to claim 10, wherein said storage apparatus is arranged for cooling said gripper when said transfer device is connected to said storage apparatus and said gripper is moved to said second gripper position.

12. Cryogenic sample handling and storage system according to claims 9-11, wherein said gripper is connected to a shaft.

13. A transfer device for transferring a sample for use in a cryogenic sample handling and storage system according to claims 1-12, wherein said transfer device is releasably connectable to a storage apparatus for storing a plurality of samples, said transfer device comprising: a transfer mechanism that is arranged for acquiring said cryogenic sample from said storage apparatus when connected to said storage apparatus, and for delivering said cryogenic sample to said CPA when connected to said CPA; an elongated housing, wherein an internal volume defined by said elongated housing at least partly comprises an internal transfer room for storing said cryogenic sample during transport of said transfer device; and a heat shield provided within said internal transfer room for keeping said cryogenic sample at cryogenic temperatures during transport of said transfer device.

14. Transfer device according to claim 13, wherein said transfer device is embodied as defined in at least one of claims 2-12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The invention will now be elucidated in more detail on the basis of exemplary embodiments and the accompanying schematic drawings, in which:

[0069] FIG. 1—shows a longitudinal cross-sectional view of a charged particle microscope according to a first embodiment of the invention;

[0070] FIG. 2—shows a longitudinal cross-sectional view of a charged particle microscope according to a second embodiment of the invention;

[0071] FIG. 3—shows a prior art sample handling and storage method;

[0072] FIG. 4—shows an embodiment of a sample handling and storage method and apparatus as defined herein;

[0073] FIG. 5—shows an embodiment of a transfer device for use in a sample handling and storage method and apparatus as defined herein;

[0074] FIG. 6—shows an embodiment of a transfer device and charged particle apparatus for use in a sample handling and storage method and apparatus as defined herein;

[0075] FIG. 7a-7f—shows various stages of a method for transferring a sample in a cryogenic sample handling system as defined herein.

[0076] FIG. 8a-8c—embodiments of a transfer device as described herein;

[0077] FIG. 9a-9c—embodiments of a transfer mechanism as described herein;

[0078] FIG. 10—a detail of a gripper for a transfer mechanism.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0079] FIG. 1 (not to scale) is a highly schematic depiction of an embodiment of a charged-particle microscope M. More specifically, it shows an embodiment of a transmission-type microscope M, which, in this case, is a TEM/STEM (though, in the context of the current invention, it could just as validly be a SEM (see FIG. 2), or an ion-based microscope, for example). In FIG. 1, within a vacuum enclosure 2, an electron source 4 produces a beam B of electrons that propagates along an electron-optical axis B′ and traverses an electron-optical illuminator 6, serving to direct/focus the electrons onto a chosen part of a specimen S (which may, for example, be (locally) thinned/planarized). Also depicted is a deflector 8, which (inter alia) can be used to effect scanning motion of the beam B.

[0080] The specimen S is held on a specimen holder H that can be positioned in multiple degrees of freedom by a positioning device/stage A, which moves a cradle A′ into which holder H is (removably) affixed; for example, the specimen holder H may comprise a finger that can be moved (inter alia) in the XY plane (see the depicted Cartesian coordinate system; typically, motion parallel to Z and tilt about X/Y will also be possible). Such movement allows different parts of the specimen S to be illuminated/imaged/inspected by the electron beam B traveling along axis B′ (in the Z direction) (and/or allows scanning motion to be performed, as an alternative to beam scanning). If desired, an optional cooling device (not depicted) can be brought into intimate thermal contact with the specimen holder H, so as to maintain it (and the specimen S thereupon) at cryogenic temperatures, for example.

[0081] The electron beam B will interact with the specimen S in such a manner as to cause various types of “stimulated” radiation to emanate from the specimen S, including (for example) secondary electrons, backscattered electrons, X-rays and optical radiation (cathodoluminescence). If desired, one or more of these radiation types can be detected with the aid of analysis device 22, which might be a combined scintillator/photomultiplier or EDX or EDS (Energy-Dispersive X-Ray Spectroscopy) module, for instance; in such a case, an image could be constructed using basically the same principle as in a SEM. However, alternatively or supplementally, one can study electrons that traverse (pass through) the specimen S, exit/emanate from it and continue to propagate (substantially, though generally with some deflection/scattering) along axis B′. Such a transmitted electron flux enters an imaging system (projection lens) 24, which will generally comprise a variety of electrostatic/magnetic lenses, deflectors, correctors (such as stigmators), etc. In normal (non-scanning) TEM mode, this imaging system 24 can focus the transmitted electron flux onto a fluorescent screen 26, which, if desired, can be retracted/withdrawn (as schematically indicated by arrows 26′) so as to get it out of the way of axis B′. An image (or diffractogram) of (part of) the specimen S will be formed by imaging system 24 on screen 26, and this may be viewed through viewing port 28 located in a suitable part of a wall of enclosure 2. The retraction mechanism for screen 26 may, for example, be mechanical and/or electrical in nature, and is not depicted here.

[0082] As an alternative to viewing an image on screen 26, one can instead make use of the fact that the depth of focus of the electron flux leaving imaging system 24 is generally quite large (e.g. of the order of 1 meter). Consequently, various other types of analysis apparatus can be used downstream of screen 26, such as: [0083] TEM camera 30. At camera 30, the electron flux can form a static image (or diffractogram) that can be processed by controller/processor 20 and displayed on a display device 14, such as a flat panel display, for example. When not required, camera 30 can be retracted/withdrawn (as schematically indicated by arrows 30′) so as to get it out of the way of axis B′. [0084] STEM camera 32. An output from camera 32 can be recorded as a function of (X,Y) scanning position of the beam B on the specimen S, and an image can be constructed that is a “map” of output from camera 32 as a function of X,Y. Camera 32 can comprise a single pixel with a diameter of e.g. 20 mm, as opposed to the matrix of pixels characteristically present in camera 30, although camera 32 can be an Electron Microscope Pixel Array Detector (EMPAD) as well. Moreover, camera 32 will generally have a much higher acquisition rate (e.g. 10.sup.8 points per second) than camera 30 (e.g. 10.sup.2 images per second). Once again, when not required, camera 32 can be retracted/withdrawn (as schematically indicated by arrows 32′) so as to get it out of the way of axis B′ (although such retraction would not be a necessity in the case of a donut-shaped annular dark field camera 32, for example; in such a camera, a central hole would allow flux passage when the camera was not in use). [0085] As an alternative to imaging using cameras 30 or 32, one can also invoke spectroscopic apparatus 34, which could be an EELS module, for example.

[0086] It should be noted that the order/location of items 30, 32 and 34 is not strict, and many possible variations are conceivable. For example, spectroscopic apparatus 34 can also be integrated into the imaging system 24.

[0087] In the embodiment shown, the microscope M further comprises a retractable X-ray Computed Tomography (CT) module, generally indicated by reference 40. In Computed Tomography (also referred to as tomographic imaging) the source and (diametrically opposed) detector are used to look through the specimen along different lines of sight, so as to acquire penetrative observations of the specimen from a variety of perspectives.

[0088] Note that the controller (computer processor) 20 is connected to various illustrated components via control lines (buses) 20′. This controller 20 can provide a variety of functions, such as synchronizing actions, providing setpoints, processing signals, performing calculations, and displaying messages/information on a display device (not depicted). Needless to say, the (schematically depicted) controller 20 may be (partially) inside or outside the enclosure 2, and may have a unitary or composite structure, as desired. The controller comprises, as shown in this embodiment, a data processing apparatus P that is arranged for carrying out the method as defined herein.

[0089] The skilled artisan will understand that the interior of the enclosure 2 does not have to be kept at a strict vacuum; for example, in a so-called “Environmental TEM/STEM”, a background atmosphere of a given gas is deliberately introduced/maintained within the enclosure 2. The skilled artisan will also understand that, in practice, it may be advantageous to confine the volume of enclosure 2 so that, where possible, it essentially hugs the axis B′, taking the form of a small tube (e.g. of the order of 1 cm in diameter) through which the employed electron beam passes, but widening out to accommodate structures such as the source 4, specimen holder H, screen 26, camera 30, camera 32, spectroscopic apparatus 34, etc.

[0090] Now referring to FIG. 2, another embodiment of a charged particle apparatus is shown. FIG. 2 (not to scale) is a highly schematic depiction of a charged-particle microscope M; more specifically, it shows an embodiment of a non-transmission-type microscope M, which, in this case, is a SEM (though, in the context of the current invention, it could just as validly be an ion-based microscope, for example). In the Figure, parts which correspond to items in FIG. 1 are indicated using identical reference symbols, and will not be separately discussed here.

[0091] Additional to FIG. 1 are (inter alia) the following parts: [0092] 2a: A vacuum port, which may be opened so as to introduce/remove items (components, specimens) to/from the interior of vacuum chamber 2, or onto which, for example, an ancillary device/module may be mounted. The microscope M may comprise a plurality of such ports 2a, if desired; [0093] 10a, 10b: Schematically depicted lenses/optical elements in illuminator 6; [0094] 12: A voltage source, allowing the specimen holder H, or at least the specimen S, to be biased (floated) to an electrical potential with respect to ground, if desired; [0095] 14: A display, such as a FPD or CRT; [0096] 22a, 22b: A segmented electron detector 22a, comprising a plurality of independent detection segments (e.g. quadrants) disposed about a central aperture 22b (allowing passage of the beam B). Such a detector can, for example, be used to investigate (the angular dependence of) a flux of output (secondary or backscattered) electrons emerging from the specimen S.

[0097] Here also, a controller 20 is present. The controller is connected to the display 14, and the display 14 may be connectable to a data processing apparatus P that is arranged for carrying out the method as defined herein. In the embodiment shown, the data processing apparatus P is a separate structure that does not form part of the controller, and does not even form part of the microscope P. The data processing apparatus P may be local or cloud based, and is in principle not limited to any location.

[0098] The charged particle apparatuses shown in FIGS. 1 and 2, and Electron Microscope (EM) in particular, offer a number of ways to study biological samples: conventional TEM is used to study gross morphology of biological samples; electron crystallography and single-particle analysis are dedicated to study proteins and macromolecular complexes; and (cryo-)electron tomography and Cryo-EM of vitreous sections (CEMOVIS) are aimed at cellular organelles and molecular architectures.

[0099] As indicated in the introduction, these biological samples can be preserved by rapid freezing using a vitrification technique, to be subsequently studied using a cryo-EM technique, such as cryo-TEM. Cryo-sectioning of the sample, using a cryo-FIB technique, may be part of sample study.

[0100] Samples used in these studies, must first be prepared, and are then stored. To this end, an aqueous sample of a biological material (usually a purified protein complex) is taken and applied to a support structure (grid), the dimension is reduced to a very thin layer, and then this layer is frozen fast enough to prevent the water from crystallising. Samples are then prepared and stored for further handling.

[0101] As indicated in the introduction, one of the methods for storing and handling samples relates to a so-called AutoLoader. Now referring to FIG. 3, an embodiment of this prior art technique is discussed. FIG. 3 shows a workflow of collecting samples S for transport to a charged particle microscope M, such as a cryo-TEM, using an AutoLoader AL and associated NanoCab N cartridge. The AutoLoader AL is part of the microscope M. The NanoCab is loaded with a plurality of samples S, and then transported to the AutoLoader AL for loading a sample into the TEM.

[0102] Shown in FIG. 3, top row, from left-to-right, is the preparation of the NanoCab N. A plurality of samples S (i.e. a biological specimen that is provided on a grid) are provided in gridboxes G. The gridboxes G with the samples S are put into a loading station 101. The loading station 101 is filled with liquid nitrogen 103, keeping the samples S and the gridboxes G at a desired, low, temperature. A cassette C is also provided in the liquid nitrogen 103. The samples S are manually transferred from the gridboxes G to the cassette C. Once the cassette is full, the Nanocab device N is connected to the loading station 101, and the cassette is provided inside the Nanocab N. The Nanocab N device now contains the cassette C with desired samples S, wherein the Nanocab N device is filled with liquid nitrogen for keeping the samples S at the desired, low, temperature. The loading station 101 can then go back to room temperature, as the liquid nitrogen is removed from the loading station when, or after, the cassette C is introduced into the Nanocab device N.

[0103] FIG. 3, bottom part, shows that the Nanocab N, comprising the cassette C with a plurality of samples S, is connected to an Autoloader AL module. The Autoloader AL module is connected to a microscope, or is part thereof.

[0104] The Autoloader AL module comprises a cassette arm 113, and a sample arm 111. The inside of the Autoloader AL housing is kept at a desired, low, temperature that is arranged for preserving cryo-Samples. The Autoloader AL module comprises two valve elements 115, 117. The first one 115 is able to provide a connection to a connected Nanocab N. The second one 117 is able to provide a connection to the microscope M.

[0105] The procedure for loading the samples from the Nanocab N to the microscope M is as follows. The Nanocab N is connected to the Autoloader AL, as shown in FIG. 3, lower part. The valve 115 is opened, and the cassette arm 113 reaches downwards to grab the cassette C with samples S, after which upwards movement is initiated for moving a desired sample S in front of the sample arm 111. The valve 115 can be closes again.

[0106] The sample arm 111 can then collect a sample S, after which the cassette arm 113 moves the cassette C with the remaining samples further upwards, and out of the way of the sample arm 111.

[0107] Then, the valve 117 can be opened, and the sample arm 111 moves the sample towards the sample holder H of the microscope M. Once the sample S is transferred to the microscope M, the sample arm 111 can return, and the valve 117 can be closed again. Then, observation or manipulation of the sample can take place.

[0108] As indicated, this known Autoloader AL system provides excellent results, especially in terms of sample transfer quality and screening throughput. There exists, however, a desire for improving this system, in particular with respect to sample loading, complexity, ease of installation and maintenance, and associated costs.

[0109] To this end, the invention provides a system for handling and storing cryo-charged-particle samples, such as cryo-EM samples. In general, this system comprises a storage apparatus, a charged particle apparatus, and a transfer device that is arranged for transferring cryo-Samples from the storage apparatus to the charged particle apparatus.

[0110] FIG. 4 shows an embodiment of the storage apparatus L. The top row of FIG. 4 shows how samples S are loaded into the storage apparatus L. To this end, samples are provided in gridboxes G. The gridboxes are placed inside a housing 201 of the storage apparatus L, wherein said housing 201 is partly filled with liquid nitrogen 203. A cassette C is provided in the liquid nitrogen 203 as well. The samples are then manually transferred (step 1.) from the gridbox G to the cassette C. Once the samples S are transferred, the cassette C remains (step 2.) inside the housing of the storage apparatus L. The cassette C may be moved, such as for example using cassette arm 211 (see bottom part of FIG. 4), to a separate storage location of the storage apparatus (not shown).

[0111] As shown in FIG. 4, the cassette C with samples S is stored inside the housing 201 of the storage apparatus L. In this sense, the housing 201 with liquid nitrogen 203 provides a cryogenic storage room for safely storing the samples inside the storage apparatus.

[0112] Once a desired sample is required, the following procedure may be followed. First, a transfer device T as defined herein is provided, and said transfer device T is connected to the storage apparatus S.

[0113] The transfer device T comprises an elongated housing 303 that is filled with gaseous nitrogen 303, in which a sample S to be transferred can be temporarily stored at the right temperature. The transfer device T comprises a transfer arm 311 with a gripper 331. The gripper 331 may be used for collecting a sample S. The gripper with the sample S may then be moved inside the housing 303 of the transfer device T.

[0114] In the embodiment shown in FIG. 4, the storage apparatus L comprises a valve member 215. The transfer device T also comprises a valve member 315, or transfer port 315. The storage apparatus comprises a first docking member 221 that is arranged to mate with a second docking member 321 of the transfer device T (shown schematically). The storage apparatus may comprise a slot 221, and a housing part 321 of the transfer device may slide into said slot 221 for providing a connected state of the transfer device T and the storage apparatus. This way, a translational docking is provided. Other docking mechanisms or ways of connecting the transfer device T to the storage apparatus L are conceivable as well. It is advantageous in case the docking member 321 of the transfer device T acts as a male connector 321, and the docking member 221 of the storage apparatus L acts as a female connector 221.

[0115] As shown in FIG. 4, the system may comprise at least one connection mechanism 340 for securing said connection between said transfer device T and said storage apparatus L. Here, the connection mechanism 340 is a suction disc mechanism 340 that comprises a first sealing ring 341, and a second sealing ring 342, that together with the transfer device T and the storage apparatus L define an annular, ring-shaped suction disc volume 345. It is noted that the second sealing ring 342 encloses said transport port 315 (valve 315), so that the transport port 315 is not part of the suction disc volume 345.

[0116] The transfer device T can be connected (or docked) to the storage apparatus L. When the transfer device T is in contact with the storage apparatus, and the suction disc volume 345 is established and closed, the pressure inside the suction disc volume 345 can be reduced. This way, the reduced pressure ensures a suction force between the transfer device T and the apparatus L, so that the connection is temporarily fixed and movement between the transfer device T and the apparatus L is substantially prevented. The suction disc mechanism ensures in this way that connection is easy, safe and secure, without needing complicated latching mechanisms, for example.

[0117] In an alternative embodiment (not shown) a latching mechanism is used for securing said connection between said transfer device T and said storage apparatus L. The latching mechanism may comprise a latch that grips onto a hook member or recess.

[0118] Once the transfer device T is connected (or docked) to the storage apparatus L, transfer of the sample S can take place. The valve 315 of the transfer device T is opened, and the valve of the storage apparatus 215 is opened as well. The cassette arm 211 positions the desired sample S in line with the transfer arm 311 of the transfer device T. The transfer arm 311 moves inside the housing 201 of the storage apparatus L, and picks the sample S out of the cassette C, using the gripper 331. The transfer device T is thus arranged for acquiring a sample S out of said cassette C. The gripper 331 with the sample S is then moved to the inside of the housing 303 of the transfer device T. All valves 215, 315 are then closed. The transfer device T can then be disconnected from the storage apparatus L, for movement to the Charged Particle apparatus.

[0119] Indicated in FIG. 4, is that the step of positioning the desired sample S, using cassette arm 211, is done mechanically, and in particular automatically, without handling being required by a human operator. The human operator may, through a user interface, select the desired sample, but movement, positioning, collection and transfer are done automatically. This limits the possibility of errors that can occur.

[0120] FIG. 5 shows the transfer device T in a disconnected state, wherein the sample S is safely seated in gripper 331 of the transfer arm 311. The sample is housed inside housing 303, wherein the housing is filled with gaseous nitrogen to keep the sample at a desired, low, temperature. The heat capacity of the gaseous cold nitrogen inside the housing 303 is such that the transfer device keeps the sample at a desired temperature range for several minutes, such as, for example 15 minutes. Additional cooling means may be provided on, or inside of, the transfer device T to provide active cooling of the sample S inside the housing 331. The transfer device T is transportable by a human operator. The dimensions of the transport device T are chosen such that the average human operator is able to carry the transport device from a first location to a second location, such as for example from the storage apparatus L to the charged particle microscope M. The device may have a length in the order of centimetres, decimetres, or even metres. In a practical embodiment, the device T has a length in between 40 cm to 80 cm, although other dimensions are conceivable as well. The weight of the device T may be in the order of 1 to several kilograms.

[0121] FIG. 6 shows the transfer device T being connected to a microscope M. The microscope M is provided with a first docking member 421 that is able to mate with the second docking member 321 of the transport device T. As indicated previously, the docking member 321 of the transport device T may be formed by an external housing part of the transport device T. The microscope M may be provided with a slot 421 that is able to receive the transport device T, or at least the second docking member thereof 321.

[0122] The transfer device T can be connected (or docked) to the charted particle apparatus CPA, M. The microscope M has a valve member 415. Once the transport device T is connected and fixed to the microscope M, or charged particle apparatus CPA in general, the valves 315, 415 can be opened, and the transfer arm 311 can move inside the microscope for transferring the sample S to the holder H of the microscope M. With this, the transfer of the sample from a storage location to the charged particle apparatus, such as an electron microscope M, is complete.

[0123] The transfer device T can be removed from the microscope M, and transfer of a second sample S2 may occur, whilst the microscope is examining the first sample S.

[0124] FIG. 7a-7f schematically show an embodiment of the sample handling and storage system 500 as defined herein.

[0125] FIG. 7a shows that the system 500 comprises a storage apparatus L for storing a plurality of samples S, S2. The storage apparatus L may comprise a user input device 114, in the form of a conventional personal computer having a screen, for example.

[0126] The system further comprises a Charged Particle Apparatus (CPA) M, such as a SEM, TEM, STEM and/or FIB. The CPA M is positioned at a location remote from said storage apparatus L. This means, in an embodiment that the CPA M is positioned at a distance of at least 50 cm from the storage apparatus L. For example, the CPA may be positioned at a distance of one to several metres from the storage apparatus. In effect, the distance between the storage apparatus L and the Charged Particle Apparatus M is so large, that a direct transfer from the storage apparatus L to the Apparatus M is not possible, and that an intermediate transfer step is necessary. The advantage of such a system is that it is relatively flexible, as the storage apparatus L and the charged particle apparatus can be positioned at any desirable location, even in different rooms with different environmental conditions.

[0127] To ensure safe and reliable sample transfer between the charged particle apparatus CPA and the storage apparatus L is possible, the system 500 comprises a transfer device T. The transfer device T can be handled by a human operator 600. The human operator 600 may carry the transfer device T to and from the storage device, and to and from the charged particle apparatus CPA M.

[0128] Now turning to FIG. 7b, it is shown that the transfer device T is releasably connectable to said storage apparatus L. As indicated before with respect to FIG. 4, the transfer device is arranged for acquiring a sample S from said plurality of samples S, S2 when connected to said storage apparatus L. In the embodiment shown, the sample is a cryogenic sample. The transfer is effected by connecting the transfer device T to the storage apparatus L, for example by inserting the transfer device T in a slot or recess that is present in the storage apparatus. The connection can then be secured by means of a connection mechanism (not shown), such as the earlier mentioned suction disc mechanism. After connecting and securing, the sample transfer as described in FIG. 4 can take place. As shown in FIGS. 7b and 7c, the sample is moved from the storage apparatus L to the transfer device T, in a docked position of the transfer device T with respect to said storage apparatus L. Sample transfer from the storage apparatus L to the transfer device T takes place automatically, in an embodiment, without the need of human operator sample handling.

[0129] Once the sample is inside the transfer device T, the human operator may retrieve the transfer device T from the storage apparatus L. The transfer device T with the desired sample S can then be moved to a further location, such as the microscope. The human operator 600 may walk to the further location, wherein the transfer device T is carried by the human operator 600.

[0130] Now turning to FIG. 7e, it is shown that the transfer device T with the sample S is connected to the microscope M (or charged particle apparatus in general). The transfer mechanism of the transfer device T then transfers the sample S from the transfer device T to the sample holder H of the microscope M.

[0131] Then, the sample can be observed and/or examined by the microscope M, as described with respect to FIG. 1 and FIG. 2.

[0132] As indicated in FIG. 4-7, the transfer device T comprises a transfer mechanism 311, 331 that is arranged for acquiring said sample S (which is a cryogenic sample in the embodiment shown, although other samples can be used as well) from said storage apparatus L when connected to said storage apparatus L, and for delivering said sample to said CPA when connected to said CPA. This way a single mechanism can be used to transfer the sample between two external apparatuses. The apparatuses do not need to have such a mechanism, although they should be arranged to cooperate with the transfer mechanism. Additionally, the apparatuses may comprise additional measures, including mechanical arms 211, valves 215, 415 and the like, for optimizing sample transfer and cooperation with the transfer mechanism 311, 331 of the transfer device.

[0133] In an embodiment, the transfer mechanism comprises a movable arm 311. The movable arm may be arranged for translational movement. An outer end of the movable arm 311 may be provided with a gripper 331, wherein said gripper 331 is arranged for gripping and releasing a sample, in particular a sample that comprises a specimen that is provided on a specimen grid. The specimen grid may be connected to other grid elements as well, wherein these grid elements aid in the ease of handling of the sample. The grid elements may comprise, for example, a C-clip ring (i.e. AutoGrid, Thermo Fisher Scientific™) onto which the specimen grid can be mounted, and a C-clip for securing the specimen grid inside the C-clip ring. Other grids are, of course, conceivable as well. Embodiments of the transfer mechanism will be described later with respect to FIG. 9.

[0134] As shown in FIG. 7a-7f, the storage apparatus L comprises an operator input device 114 in the form of a computer, and a control unit 220 that is connected to said operator input device 114 and that is arranged for performing at least some functions of said storage apparatus L, or of said system 500, for example in a connected state of said transfer device T to said storage apparatus L. The operator input device is, in an embodiment, arranged for selecting a sample S, S2 to be transferred, by a human operator 600, from the storage apparatus to the charged particle microscope M. The control unit 220 is arranged for controlling said storage apparatus L and said transfer device T, in a connected state thereof, for transferring said selected sample S from said storage apparatus L to said transfer device T.

[0135] The storage apparatus L, including the operator input device 114 may form a first workstation, that enables the human operator to quickly and reliably transfer prepared samples to the storage apparatus L. For example, a top part of the housing 201 of the storage apparatus L may coincide with a desk feature of the workstation. The top part of the housing 201, and/or a desk feature of the workstation, may comprise a lid that is openable and closable by a human operator, such that a gridbox G containing samples S (see FIG. 4, step 1.) can be inserted into the storage apparatus L, and the sample grids S can be transferred to the container C. The lid may also be used for refilling the liquid nitrogen level 203 inside the housing 201. The operator input device and/or the controller may be connected to the housing 201, so that information relating to the housing 201 may be provided to the human operator. For example, the storage apparatus may comprise a number of sensor elements, such as a temperature sensor, a liquid level sensor, or the like, for monitoring a condition of the storage apparatus. The operator input device 114 may provide feedback to the user with respect to one or more of these conditions.

[0136] Furthermore, it is conceivable that the operator input device 114 is used for labelling and tracking features. In an embodiment, the operator input device 114 may be wirelessly connected to the Charged Particle Apparatus, so that information regarding the sample S can be transferred to the Charged Particle Apparatus. Information may comprise sample input information, e.g. information that the human operator enters into the operator input device 114 at the time of loading a sample S into a cassette C.

[0137] Now turning to FIG. 8a-8c, embodiments of the transfer device T will be discussed.

[0138] FIG. 8a shows an overview of the transfer device T. The transfer device T comprises an elongated housing 303. On one side of the elongated housing 303 a support handle 305 is provided, that allows easy transfer and operation of the transfer device T by a user. On the opposite side of the elongated housing, the transfer device T comprises a connection face 306. On the connection face 306, a suction disc mechanism 340 is provided. The suction disc mechanism 340 is arranged for securing a connection between said transfer device T and a desired apparatus, such as the storage apparatus L or the CPA M. In the embodiment shown, the suction disc mechanism 340 comprises a first sealing ring 341, and a second sealing ring 342. The first sealing ring 341 is provided along an outer edge of the connection face 306. The second sealing ring 342 is provided near the center part of the connection face 306. The connection face 306 also comprises a transfer port 315, or transfer valve 315. The transfer port 315 is surrounded by the second sealing ring 342. As can be seen in FIG. 8a, the suction disc volume 345 is ring-shaped or donut-shaped, with the transfer valve 315 provided in the “hole” of the ring/donut. This way the transfer port 315 does not form part of the suction disc volume 345, but is enclosed by the suction disc volume. In an alternative embodiment (not shown) it is conceivable that the transfer port 315 is not enclosed by the suction disc volume 340, but that the suction disc volume is provided at a distance from said transfer port 315. However, by enclosing the transfer port 315 by the suction disc volume, a safe and reliable connection between the transfer device T and the desired apparatus L, M is established, and furthermore the risk of contamination of the sample during transfer is reduced.

[0139] To establish the connection between the transfer device T and the desired apparatus L, M, the suction disc mechanism 340 may be operated. To this end, the connection face 306 is brought into contact with the desired apparatus, and excess air is removed from the suction disc volume 345. The transfer device T comprises an air exhaust 346 that can be used to remove excess air.

[0140] As can be seen in FIG. 8a, the transfer device T comprises electrical contact elements 355. These electrical contact elements 355 are arranged for connecting to further electrical contact elements 355 provided on the desired apparatus L, M. The electrical connection provided by the electrical contact elements 355 allows information to be exchanged between the connected device and the desired apparatus, but also allows operation of parts of the transfer device, wherein said operation is initiated by the desired apparatus, for example. The information can be related to the sample type, the temperature, the sample storage condition, but may also include information regarding a successful connection, for example.

[0141] The transfer device T further comprises an interface opening 359, which may be used to operate the transfer mechanism that, in certain embodiments, is situated inside of the transfer device. In an embodiment, the interface opening 359 allows compressed air to pass from the desired apparatus L, M to the transfer device (or vice versa) for operating the transfer mechanism 311, 331.

[0142] Once the transfer device T is connected (or docked) to the desired apparatus L, M, and the suction disc mechanism 340 is operated, it will be possible to transfer the sample S from the transfer device T to the desired apparatus L, M (or vice versa). As can be seen in more detail in FIG. 8b, the transfer device comprises a latching mechanism 351 to open valve 315. The latching mechanism 351 basically comprises a sliding door mechanism. The latching mechanism 351 comprises a recess in the sliding door, that can be operated by a hook element 461 that is part of the desired apparatus L, M. This way, unintentional and undesired opening of the valve is prevented, and can only be done in a truly connected state of the transfer device. When the sliding door is moved outside of the housing of the transfer device T, then the valve 315 is opened (FIG. 8b). Returning the sliding door 351 into the elongated housing ensures that the valve 315 is closed again (FIG. 8c).

[0143] Now turning to FIG. 9a, a more detailed view of an embodiment of the transfer device T is shown, and in particular of the transfer mechanism that is provided within said elongated housing. As can be seen, the transfer device T comprises a transfer mechanism 301 that is arranged for acquiring said cryogenic sample from said storage apparatus when connected to said storage apparatus, and for delivering said cryogenic sample to said CPA when connected to said CPA. The transfer mechanism 301 is part of said transfer device T, which allows for easy transfer from and to a desired apparatus. The transfer mechanism 301 is arranged for acquiring said sample from said storage apparatus L when connected to said storage apparatus L, and for delivering said sample to said CPA M when connected to said CPA M. As shown in FIG. 9a, the transfer mechanism 301 is arranged within the elongated housing 303, which, for clarity purposes, is indicated with a dashed line. The elongated housing 303 defines an internal volume 401 that at least partly comprises an internal transfer room 402 for storing said cryogenic sample S during transport of said transfer device T. This internal transfer room 402 may be snugly surrounding the transfer mechanism 301, in this first position of the transfer mechanism 301, wherein the transfer mechanism 301 is located inside the elongated housing 303 of the transfer device T. The internal transfer room 402 protects the cryogenic sample S during transfer thereof.

[0144] As shown in FIG. 9a, the transfer device T further comprises a heat shield 411 provided within said internal transfer room 402 for keeping said cryogenic sample S at cryogenic temperatures during transport of said transfer device T. The heat shield 411 is arranged for minimizing heat loss from the cryogenic sample to the surroundings, e.g. by minimizing convective heat transfer and/or radiation to the sample. In the position shown in FIG. 9a, the sample is located inside the cylindrical heat shield 411. The heat shield can comprise, or may substantially consist of, a hollow body, such as a hollow cylinder, that is made of copper, brass, or another suitable metal. By minimizing heat loss it is ensured that the sample is maintained at the desired cryogenic temperature for a longer time period, so that the user will have sufficient time for transferring said cryogenic sample from a first desired apparatus to another desired apparatus.

[0145] As can be seen in FIGS. 9a and 9c, the heat shield 411 is movably provided within said internal transfer room 402. The heat shield 411 is movable with respect to the elongated housing 303. The heat shield 411 is movable from a first position (FIG. 9a) wherein said heat shield is located within said internal transfer room 402 to at least one second position (FIGS. 9b and 9c) wherein at least part of said heat shield 411 is located outside of said elongated housing 303. FIG. 9b shows that the heat shield 411 together with the transfer mechanism 301 are moved outside of the elongated housing 303, thereby passing through the transfer port 315. In the position shown in FIG. 9b, the heat shield 411 has moved with respect to the gripper 331 of the transfer mechanism 301, exposing the gripper 331 to the surroundings. In this position the gripper 331 is able to retrieve or deliver a sample to a desired apparatus. In the position shown in FIG. 9c, the heat shield 411 has moved relative to the gripper 331, so that the gripper 331 (and the sample S gripped by the gripper) are located within said heat shield. This protects the sample S during transfer back to the internal transfer room 402. It is noted that in the position shown in FIG. 9c, the heat shield 411 is also able to be pre-cooled, for example by using an external cooling mechanism. In principle, this holds also true for the position shown in FIG. 9b. To illustrate this, it is referred to FIG. 4, where this cooling of the heat shield 411 by an external cooling mechanism is shown. The transfer device T is connected to the storage apparatus L. The gripper 331 of the transfer mechanism 301 is moved inside the bath of liquid nitrogen 203. The heat shield 411 is moved to the second position, and is moved through the transfer port 315 and the valve 215 provided in the storage apparatus L. In this embodiment, the external cooling mechanism is provided inside the storage apparatus L, in the form of the bath of liquid coolant 203, such as liquid nitrogen 203. Here, also the gripper of the transfer mechanism 301 is cooled by the bath of liquid coolant 203, and is thus pre-cooled to maintain the sample at the desired cryogenic temperature during transfer of the sample with the transfer device T.

[0146] FIG. 10 shows an embodiment of the gripper 331 of the transfer mechanism 301. The gripper 331 is arranged for gripping said cryogenic sample S. The gripper 331 is connected to shaft 311. The gripper comprises, in this embodiment, a crocodile-like gripping mechanism, having a first gripping element 332 and a second gripping element 333, wherein said first gripping element 332 and said second gripping element 333 are arranged for gripping each other. In the embodiment shown, the gripping elements 332, 333 have distal ends 336, 337 that can be brought towards each other for gripping the sample S. Here, the second gripping element 333 is movable, whilst the first gripping element 332 is fixed. By moving the second gripping element 333 away from the first gripping element (downwards, in the embodiment shown in FIG. 10), room is made for acquiring or delivering a sample S.

[0147] Returning to FIG. 9a-9c, it can be seen that this gripper 331 is movable from a first gripper position (FIG. 9a) to a second gripper position (FIG. 9b and FIG. 9c), wherein in said first gripper position said gripper is located within said internal transfer room 402 and wherein in said second position said gripper is located outside of said elongated housing 303. This way the gripper 331 is able to reach outside of the transfer device T, and into the desired apparatus (L, M), where a transfer of the sample can take place. It will be appreciated that in the situation shown in FIG. 9b, the gripper can be cooled by an external cooling mechanism as well (similar to the heat shield 411).

[0148] Above, the system has been discussed in more detail using exemplary embodiments. The desired protection is conferred by the appended claims.