JP2012520987A - Cryogen-free cooling device and method - Google Patents

Abstract

  A cryogen-free cooling device has at least one heat shield (54) surrounding the work area (20) and arranged in the vacuum chamber (4). The cryogen free cooling system has a cooling stage coupled to the heat shield (54). The heat ray shield and the vacuum chamber wall are provided with aligned holes (56, 58). The sample loading device has a sample holder (2) that inserts the sample holder through the aligned holes (56, 58) to the working area (20). One or more of the sample holders in the vacuum chamber attached to the elongate probe (3) of the vacuum chamber, wherein the sample holder is thermally conductive by a thermal connector to precool the sample on the sample holder Can be releasably coupled to a cold object.

Description

  The present invention relates to a cryogen free type cooling device and a method of using such a device.

  When operating a cryogenic instrument at low temperatures (less than 100 Kelvin) or very low temperatures (less than 4 Kelvin), it is often necessary to change samples or other objects in the cold part of the instrument. In conventional equipment using a liquid cryogen, such as liquid helium or liquid nitrogen, this is usually done by warming up the equipment and opening the equipment or removing a portion of the equipment and warming it up. The sample is then exchanged at room temperature. Because this can be a slow process, some conventional cryogenic systems using liquid cryogens can allow a large portion of the system to remain cold. Some have a mechanism. An important challenge with these systems is that the sample is placed in the instrument at room temperature, typically about 300 K, and then moved to another location where thermal contact with the object is made at a much lower temperature. This very low temperature may be below 1K in some systems. In systems using liquid cryogens, the sample and associated mounting and coupling equipment are usually passed partially through the cryogenic gas through the system or the cryogenic gas or liquid is passed into the sample transport mechanism. It is precooled by either passing through, which reduces thermal shock to both the sample and the instrument.

  In recent years, cryogenic systems have been developed that do not require the addition of liquid cryogen or require liquid nitrogen only during initial cooling. These cryogenic systems are commonly referred to as cryogen-free (or “cryofree”) type systems. These systems use mechanical coolers such as GM coolers, Stirling coolers or pulse tubes to provide cooling power. Since the cooling power of commercial coolers is somewhat lower than that available from the liquid cryogen reservoir, these systems are typically long to warm up, change samples and cool. It may take time. Accordingly, there is a considerable need for a method of exchanging samples within a cryogen-free system without having to warm up the entire cryogen-free system.

  Some examples of known load locks for loading a sample into a cryo-free cryostat are U.S. Pat. Nos. 4,446,702 (A), 4,577,465 (A), and 5,775,523 (A). No. 5,727,392 (A), No. 5,806,319 (A), No. 5834938 (A), US Patent Application Publication Nos. 2007/0234751 and 2008/0282710. It is described in the specification.

U.S. Pat. No. 4,446,702 (A) US Pat. No. 4,577,465 (A) US Pat. No. 5,077,523 (A) US Pat. No. 5,727,392 (A) US Pat. No. 5,806,319 (A) US Pat. No. 5,834,938 (A) US Patent Application Publication No. 2007/0234751 US Patent Application Publication No. 2008/0282710

  In a cryogen-free system, there are many technical challenges when trying to load a warm sample into a cryostat cryostat. First, the internal structure of the system is usually placed in a sealed vacuum vessel to reduce the heat load. Second, within this sealed vacuum vessel, the sample space is usually surrounded by one or more radiation shields to further reduce the heat load. Third, there is no liquid cryogen available to pre-cool the sample as it moves from room temperature to a cold attachment. It is also necessary to make electrical contact to the sample remotely when loading the sample into the cryostat. The present invention seeks to provide solutions to these problems.

  According to a first aspect of the present invention, a cryogen-free cooling device includes at least one heat ray shield that surrounds a work area and is disposed in a vacuum chamber, and a cooling stage coupled to the heat ray shield. A cryogen-free cooling system, an aligned hole provided in the wall of the heat shield and the vacuum chamber, and a sample holder attached to one or more elongated probes; A sample loading device that inserts the sample through the aligned holes into the working area and a thermal connector, the sample holder holding the thermal connector to precool the sample on or in the sample holder. Through which heat can be transferred to one or more cold objects in the vacuum chamber.

  Typically, the sample loading device further includes a vacuum vessel that movably houses a sample holder and one or more elongated probes, the vacuum vessel being connectable to a hole in the vacuum chamber wall.

According to another aspect of the present invention, a method for loading a sample into a work area of a cryogen-free cooling device according to the first aspect of the present invention includes:
Placing the sample in or on the sample holder; and
Securing the vacuum vessel of the sample loading device to the vacuum chamber and aligning it with the holes of the vacuum chamber;
Evacuating the vacuum vessel;
Opening a hole in the vacuum chamber and manipulating the elongated probe to insert the sample holder into the opened hole so that the sample holder is thermally coupled to the cold object; and in the sample holder or Allowing the sample on the sample holder to cool as a result of heat conduction to the cold object,
a) uncouple the sample holder from the cold object and manipulate the elongated probe to insert the sample holder into the work area, or
b) either strengthening the thermal coupling to the cold body to increase the heat flow taken away from the sample and further cooling the sample.

  The inventor has devised a new type of apparatus that uses a cold object in a vacuum chamber to pre-cool the sample before it reaches the working area to solve the above-mentioned problems.

  Various cold objects in the cryostat can be used, such as any cold surface coupled to a cooling stage of a cooling system or an intermediate stage of a 4K or less cooler, such as a still in a dilution refrigerator, but already exists It is most convenient to use a heat ray shield. As another possible means, the cold object is the object held at the lowest temperature in the cooling device, in which case the thermal connector provides a weak thermal coupling to the initial cold object for pre-cooling. And then strengthen the bond to the cold object so that the sample cools to the desired final temperature.

  Two or more heat ray shields may be provided in the vacuum chamber depending on the temperature at which the work area is to be exposed. Thus, further use of one or more of these can precool the sample.

  For example, in a preferred embodiment, the apparatus further comprises a second heat ray shield disposed within the first heat ray shield and surrounding the work area, wherein the cryogen-free cooling system comprises the first cooling ray. Having a second cooling stage that is cooler than the stage and coupled to a second heat ray shield, the second heat ray shield being aligned with the first heat ray shield and a hole in the vacuum chamber wall. And a hole through which the sample holding device can be inserted, and the sample holding device can be releasably coupled to the second heat ray shield so as to conduct heat.

  If two or more thermal shields are provided, it is not necessary to precool the sample by connection to each shield. For example, pre-cooling should be performed only on the innermost shield (typically 4K). If three or more shields are provided, one or more can be utilized for pre-cooling.

  Typically, the first heat shield is maintained at a temperature between 45K and 90K, and the second heat shield (if provided) is maintained at a temperature below 6K or even below 4.2K.

  The heat shield holes may be left open, but preferably each hole can be closed to each closure system to reduce heat transfer. An example of a suitable closure system is one or more flexible flaps or hinged and spring-loaded flaps.

  In one embodiment, the sample loading device has two elongate probes each coupled to a sample holding device, but in other embodiments a single elongate probe may be used. In both cases, preferably the probe is rotatable about its axis relative to the sample holder. Of course, more than two probes can be used.

  The connector is conveniently formed by providing a thread at one end of the rod, and the first connector cooperates with a thread provided on the cold object or one of the cold objects. Thus, thermal coupling with the low temperature object is achieved. Alternatively, the thermal coupling may be achieved using a spring coupling means, in which case the sample holder is one or more thermally conductive springs that engage the inner surface of the hole in the heat shield. Is provided. As an extension of this inner surface, for example, a tube assembly or a thick plate assembly that allows for engagement may be additionally provided. The spring connectors may be fixed on a hot wire or a heat shield and the sample holder may be pressed against these spring connectors. Alternatively, the thermal coupling may be performed by a spring at the high temperature shield and by screw contact at the low temperature shield, or any combination thereof. In another embodiment, the connector may be configured with a conical or wedge shaped mating portion that increases the contact pressure from the attachment mechanism. This significantly improves performance.

  In the case described above, where the connector initially provides a weak thermal bond, this is achieved by contacting the screws partially for pre-cooling and then bringing them into full contact once pre-cooled (the screws are provided). Or as an alternative, it may be done by initially pushing the screw into spring contact and then tightening the clamp screw once precooled.

  In a particularly preferred embodiment, the probe is releasably coupled to the sample holder, and the first operation of the probe couples the sample holder to a support provided at the work area, and By this operation, the probe can be released from the sample holder and retracted. This allows the probe to be removed from the cryostat vacuum chamber to reduce heat flow into the cryostat. The probe or the cold body may be provided with an actuator that enables this.

  Cryogen-free cooling devices can be used for various purposes such as scientific cryogenic research, quantum computer calculations, experimental analysis, material characterization, device characterization, detector cooling, device cooling, DNP, NMR or cryogenic temperatures. It can be used for any other application that requires cooling of the material, and in many cases, it may be placed in a cryostat surrounding the work area.

  It should be understood that the releasable nature of the sample loading device, particularly the sample holder, just described is considered inventive in its own right and is defined in the first and second aspects of the invention. This is considered to be different from the sample precooling concept.

  Several specific examples of the apparatus and method of the present invention will now be described with reference to the accompanying drawings.

1 is a cut-away partial cross-sectional view of a first embodiment of a sample holding device. FIG. 2 shows a first embodiment of a sample loading device with the sample holder retracted from the shield (shield and electrical connector not shown for clarity); FIG. 3 is a view similar to FIG. 2 of the first embodiment, but showing the state in which the sample holder is connected to a cryogenic plate in the cryostat (the shield is not shown for clarity); 1 is a detailed cross-sectional view of a first embodiment of a sample loading device. A detailed cross-sectional view of the first embodiment showing a possible mechanism for closing the port of the shield when loaded with a sample (the shield and electrical connectors are not shown for clarity); FIG. 6 is a cutaway view of a second embodiment of a sample loading device. It is a cutaway view of the fitting part of 2nd Embodiment of a sample holding device and a sample loading apparatus.

  A first embodiment of the invention is shown in detail in FIGS. In FIG. 1, a sample 1 is attached to a sample carrier or sample holder 2 supported on two rods or a thermally conductive rod of a probe assembly 3. The sample carrier 2 has space for a number of electrical and / or optical connectors (not shown) that allow coupling to connectors attached to the main cold object in the cryostat. This provides a high degree of flexibility and can optionally use multiple push-fit connectors to allow the wiring to go through the cryostat rather than down along the probe tube, thereby significantly Thermal benefits are obtained. The ends of the two rod assemblies 3 can rotate freely in the carrier. The tube / flange assembly forms a vacuum vessel 6 that surrounds the rod assembly 3, which is open at one end, and this end closely contacts the bottom of the gate valve when assembled into the cryostat 50. . At the opposite end of the vacuum vessel 6, the rod assembly extends through a pair of O-ring seals 7. A separate vacuum space 9 and port 8A are provided between the seals so that air leaking through the first seal can be exhausted through the valve 8 when the rod assembly is moved. .

  The cryostat 50 has the outer vacuum vessel 4 closed except for the port 52 covered by the large-diameter gate valve 5. A first radiation shield 54 having a hole 56 aligned with the hole 52 of the vacuum chamber is disposed within the vacuum vessel 4, and a hole 58 aligned with the holes 52, 56 is disposed within the first radiation shield 54. A second radiation shield 10 having the following is arranged. The radiation shields 10 and 54 surround the work area 20 in which the low temperature attachment object 15 is provided.

  The shields 10, 54 are cooled by conventional mechanical coolers, such as GM coolers, Stirling coolers or pulse tube devices. This is not shown in the drawing for clarity. The first stage of the mechanical cooler is thermally coupled to the shield 54, and the second lower temperature stage is thermally coupled to the shield 10. Typically, the first shield 54 is cooled to a temperature of about 77K, and the second shield 10 is cooled to a temperature of 6K or less, for example, about 4.2K. In some cases, the second shield is held at a temperature higher than 6K. Thus, each of the shields held at the lowest temperature as well as the cold attachment object 15 can be considered a “cold object”.

  As can be seen in FIG. 2, the hole 56 in the shield 54 is defined by the plate 12 with the notch 17. In perturbation, the hole 58 in the shield 10 is defined by another plate 12 and a notch 17.

  Optionally, the holes 56, 58 may be closed by a suitable closure mechanism. FIG. 5 is an enlarged cross-sectional view of one possible embodiment of such a mechanism. One or more flaps 25 are connected to the radiation shield 10 by spring hinged structures 26. As the rod assembly 3 penetrates the flap assembly, one or more flaps 25 are opened. The one or more flaps 25 may optionally be shaped to prevent the sample carrier, baffle or rod assembly from catching on the flaps when the rod assembly and / or carrier is retracted. It is preferable to provide a guide mechanism body that performs proper prevention.

  To explain the operation, the sample 1 is loaded on the sample carrier 2, and electrical or optical coupling is performed. Next, the sample carrier 2 is attached to the end of the rod assembly 3. Next, the rod assembly 3 is retracted through the sliding O-ring seal 7 until the sample carrier is completely located in the vacuum vessel 6. Next, the vacuum vessel 6 is attached to the gate valve 5, and air is discharged from the vacuum vessel 6 through the ports 8 </ b> A and 8 </ b> B and the valve 8. When a vacuum is generated on both sides of the gate valve 5, the gate valve is opened. The rod assembly 3 is then pushed to move the sample carrier into the gate valve and to the first precooling position.

  FIG. 2 shows the condition where the sample carrier 2 approaches the plate 12 of the shield 54 and thermally couples the sample carrier to the radiation shield precooling position to form a first cold object. The rod assembly 3 has a key 22 (FIG. 4) provided at the end, which turns the thread 18 when engaged. The thread 18 is aligned with the counter thread 19 provided on the plate 12 so that the sample carrier 2 can be screwed to the plate 12 of the radiation shield 54, thereby obtaining a thermal contact. It is done. An optional thermometer (not shown) is provided on the sample carrier or rod assembly so that the temperature of the sample carrier can be monitored during cooling. When the sample carrier 2 is sufficiently cold, the rod assembly 3 is turned again to separate the two threads from each other. Next, the entire rod and carrier assembly is rotated by a rotary seal provided in the vacuum vessel 6 or the gate valve 5 so that the carrier 2 can pass through the notch 17. The carrier is then optionally coupled in a similar manner to one or more optional additional radiation shields, such as shield 10 (forming additional cold objects).

  Once the sample carrier has been reasonably pre-cooled, the rod assembly 3 is pushed to their final position to allow connection of the sample carrier 2 to the cold object 15, which, for example, can be mixed in a dilution refrigerator. It may be connected to a chamber or cryostat sample plate. FIG. 3 shows a state in which the sample carrier 2 is in contact with the cold plate 15. The screw thread 18 is screwed into a mating screw thread (not shown) provided on the low temperature plate 15. During the thermal coupling of the sample carrier 2 and the cold object 5, a number of optional indentation electrical and optional optical couplings may be made between the sample carrier 2 and the cold object 15. These connectors are not shown in this figure. In this view, two baffle assemblies 14 are also visible. These baffle assemblies can slide freely along the rod assembly 3, and they are pushed or pulled by the spring assembly 21 toward the sample carrier. For the sake of clarity, the baffle assemblies 14 are shown here in the retracted position, and in practice, these baffle assemblies are brought into contact with the plate of the radiation shield by a spring assembly, thereby The notch 17 is closed and thermal contact is made. The baffle assembly is also optionally coupled to the rod assembly using sliding thermal coupling means, such as a thermally conductive spring assembly, thus blocking the heat down along the rod from room temperature. Can do.

  FIG. 4 is an enlarged cross-sectional view of the sample carrier and rod assembly. A key 22 is provided at the end of each rod assembly 3, and this key fits into a fitting connection provided in the screw thread 18. The key and rod assembly is provided with a screw thread 23, and the sample carrier is provided with a screw thread 24 to be screwed therewith. This arrangement means that when the rod assembly is retracted, the threads 23, 24 collide with each other and therefore the sample carrier is also retracted. Once the sample carrier is connected to the cold object 15 by the thread 18, the rod assembly may then be partially retracted and the key removed from behind the thread 18 to reduce sample heat flow. However, this is not essential and the sample may remain coupled to the probe. When the threads 23, 24 collide with each other, the rod assembly is rotated to allow the threads to pass each other, and then either one of the rod assemblies is partially retracted from the cryostat, The baffle can remain in contact with the radiation shield, or either one of the rod assemblies can be fully retracted from the cryostat to further reduce the thermal load.

  When the rod assembly is fully retracted from the cryostat, an optional mechanism 11 may be attached to close the radiation shield cutout.

  A second embodiment of the present invention is shown in FIG. In this embodiment, a single rod assembly 3 is used with a single large diameter thread 18. An adapter 27 for connecting the rod assembly to the sample carrier assembly 2 is provided at the end of the rod assembly 3. The adapter is provided with one or more protrusions 28 that fit into slots or recesses 29 formed in the means 12 that can thermally couple the carrier to the radiation shield. As in the case of the first embodiment, the sample is loaded into the carrier and is inserted into the gate valve 5. The rod assembly is rotated to fit the protrusion 28 into the slot or recess 29 and then push the rod assembly toward the cryostat until the protrusion 28 hits the obstacle 30. In this case, as an option, thermal coupling is performed via a protrusion or an optional spring contact portion 31. Slots and obstructions are optional and they help to prevent the sample carrier from being accidentally pushed past the radiation shield prior to pre-cooling.

  With moderate cooling of the sample, the sample rod is optionally retracted slightly and then rotated so that the protrusion 28 can move past the obstacle 30. The rod assembly is then further inserted so that it can be thermally coupled to the next radiation shield if necessary. When the sample rod is inserted into the shield, an optional baffle 13 with an optional spring thermal contact 14 fits into the assembly 12 to close the radiation shield port and optionally the radiation shield. And the rod assembly are in thermal contact, thereby blocking heat. Next, a similar optional method of precooling on the next radiation shield may be performed, after which the sample is moved to a cold object.

  FIG. 7 is a cross-sectional view of a second embodiment sample carrier assembly engaged with a cold object. The sample carrier 2 is housed in a tube 32 with a thread 18 at one end. At the opposite end of the tube, means 33 are provided for connecting the tube to the adapter at the end of the rod assembly. This allows the tube to be inserted or retracted and rotated by the rod assembly. The sample carrier is free to rotate within the tube, and this sample carrier is thermally coupled to the adapter at the end of the rod assembly using spring thermal contacts 34. When the tube and carrier assembly is pushed and fitted into a mating part attached to a cold object, the keyway rotationally aligns the sample carrier with the mating part and the optional connector 35 is aligned with each other. To do. The rod assembly is then rotated to pull the sample carrier and fit it into the mating part, thereby making thermal contact and optionally providing electrical and optical coupling. The rod assembly may then be withdrawn from the cryostat, thereby releasing the connection at the means for connecting the tube to the adapter at the end of the rod assembly. If the rod assembly is to be completely removed, an optional baffle may be installed to close the radiation shield port. Sample removal is essentially the reverse of the insertion process, with the difference that it is not usually necessary to leave the sample carrier at the radiation shield to warm up as the sample is retracted. .

Modified embodiment

  In a first variant embodiment, a spring connection comprising one or more thermally conductive springs for engaging a mechanism for connection to the radiation shield from the screw connection system to the inner surface of the notch of the radiation shield. It is possible to change to a method. As an extension of this inner surface, for example, a tube assembly or a thick plate assembly that allows for engagement may be additionally provided. Alternatively, the thermal coupling may be performed by a spring at the high temperature shield and by screw contact at the low temperature shield, or any combination thereof. In another embodiment, the connector may use a conical or wedge shaped mating portion on each side of the releasable coupling to increase contact pressure from the attachment mechanism. Pneumatic or piezoelectric or other types of releasable contact methods can also be used.

In all embodiments, the connection to the cold object may optionally be made via a thermally conductive spring contact rather than a screw connection.
In all embodiments, the connection to the radiation shield may optionally be made via a thermally conductive spring contact or a screw contact.

  In all embodiments, if it is specified that thermal coupling to one or more radiation shields may be performed, this thermal coupling may, as a variant, be applied to any other suitable cold surface. It may be performed against.

  In all embodiments, as an alternative to precooling at progressively lower temperatures at the radiation shield, the sample and carrier can optionally make a weak thermal contact to a cold object, e.g., the coldest object. May be pre-cooled. Making the cryostat relatively warm and making the sample and carrier relatively cool can be controlled by close thermal contact.

  In any case where thermally conductive spring contacts are used, these may be made of a single material, for example beryllium copper alloy, or with good spring force and high thermal conductivity. It may be made of a laminate or composite of different materials that provide both. This includes, for example, beryllium copper alloys or steels that provide spring force, and copper, silver and / or gold that increase thermal conductivity. The use of dissimilar materials is preferred to reduce eddy currents and quenching forces when used in magnets. Examples of dissimilar materials may be copper for high thermal conductivity and stainless steel for low thermal conductivity for the purpose of reducing high strength and induced eddy currents. Other possible examples include titanium and copper or brass and copper or aluminum alloys and copper. In general, this is one material with high thermal conductivity and one material with high strength and high resistance. The second material may also be a plastic or a composite.

  In all embodiments, an additional port or multiple additional ports are provided in the second vacuum vessel to remove the sample and optionally the sample carrier without removing the second vacuum vessel from the main vacuum vessel. You may be able to.

  In the second embodiment, the connection to the radiation shield can be changed to a screw thread provided outside the rotary tube assembly. It is also possible to change the threaded connection to the cold object to a male thread, which uses the same thread to connect to the radiation shield for pre-cooling and then to the cold object. It means that the connection of can be performed. The threaded tube assembly may optionally be provided with a tear that allows the diameter to change to compensate for thermal expansion and contraction.

  Although not shown, a superconducting magnet may be disposed in the cryostat 50 as known for conventional dynamic nuclear polarization and nuclear magnetic resonance and cryogenic magnetic field applications.

  In the above example, the rod forms an actuator for attachment to and detachment from a cold object and is removable from the cryostat. In a variant, the rod (or other actuator) may form part of a cryostat, the sample carrier may be supported on a probe independent of the rod (or other actuator), and the rod (or The other actuator) is operated to engage the thread (or other coupling mechanism) as before.

Claims (24)

  A cryogen-free cooling system, comprising at least one heat ray shield surrounding a work area and disposed in a vacuum chamber, and a cryogen-free cooling system having a cooling stage coupled to the heat ray shield An alignment hole provided in a wall of the heat ray shield and the vacuum chamber, and a sample holding device attached to one or more elongated probes, the sample holding device being in the aligned state. A sample loading device for passing through a hole and into the working area; and a thermal connector, wherein the sample holder is used to precool the sample on or in the sample holder. Can be releasably coupled to one or more cold objects in the vacuum chamber so that heat can be conducted Apparatus.   The apparatus of claim 1, wherein the cold object is formed by a surface associated with a cold plate coupled to a cooling stage of the cooling system.   The apparatus according to claim 1, wherein the cold object is formed by a heat shield, and the first connector can be releasably coupled to the heat shield to conduct heat.   A second heat ray shield disposed within the first heat ray shield and surrounding the work area, wherein the cryogen-free cooling system is at a lower temperature than the first cooling stage; A second cooling stage coupled to the second heat ray shield, the second heat ray shield being aligned with the first heat ray shield and the hole in the vacuum chamber wall; 4. The apparatus of claim 3, comprising a hole through which the sample holder can be inserted, wherein the sample holder can be releasably coupled to the second heat shield that acts as the cold body to conduct heat. .   The apparatus of claim 4, wherein the second heat ray shield is maintained at a temperature of less than 6K.   The apparatus according to claim 1, wherein the first heat ray shield is maintained at a temperature of 45K to 90K.   The cold object is the coldest object in the cooling device, and the thermal connector can achieve a weak thermal coupling with the sample holder, and then achieves a high heat flow with a strong thermal coupling relationship Apparatus according to any one of claims 1 to 6, enabling.   The apparatus according to claim 1, wherein the vacuum chamber hole comprises a closure system, for example a vacuum valve.   The apparatus according to claim 1, wherein each of the heat ray shield holes can be closed by a closure system.   The apparatus of claim 9, wherein the closure system for the hole in the heat shield comprises one or more flexible flaps or hinged and spring-loaded flaps.   11. The apparatus according to any one of the preceding claims, wherein the sample loading device comprises two or more elongate probes each coupled to the sample holder.   The apparatus of claim 11, wherein the probe is rotatable about its axis relative to the sample holder.   The probe is a screw provided with a thread at one end so as to constitute the thermal connector, and the thermal connector is a thread provided on one of the low temperature object or the plurality of low temperature objects. 13. An apparatus according to claim 11 or 12, adapted to cooperate with the apparatus to achieve thermal coupling with the cold object.   1. One or more of the thermal connectors comprises one or more thermally conductive springs attached to thermally contact the cold object and the sample holder. The apparatus according to any one of 11.   15. The apparatus of claim 14, wherein the thermally conductive spring comprises a composite material having high thermal conductivity and high spring force.   The sample loading device is rotatable with respect to the vacuum chamber and the heat shield to selectively align with the thermal connector or the hole, respectively, and to allow the sample holder to pass through the hole. Item 16. The apparatus according to any one of Items 1 to 15.   The probe is releasably coupled to the sample holder, and by a first operation of the probe, the sample holder is coupled to a support provided at the working area, and the second second The apparatus according to claim 1, wherein the probe can be released from the sample holder and retracted by operation.   The sample loading device further includes a vacuum vessel that movably houses the sample holding device and the one or more elongated probes, the vacuum vessel being connectable to the hole in the vacuum chamber wall. The device according to claim 1.   The apparatus according to any one of the preceding claims, wherein the cryogen-free cooling system comprises a mechanical cooler, for example a GM cooler, a Stirling cooler or a pulse tube device.   20. The sample holder according to any one of the preceding claims, comprising one or more electrical connectors so that electrical and thermal coupling can be made to a cold object in the work area. The device described in 1.   21. The sample holder includes one or more optical connectors, such as fiber optic connectors, so that electrical and thermal coupling can be made to a cold object in the work area. The device according to any one of the above. A method of loading a sample into a work area of at least a cryogen-free cooling device according to claim 18, comprising:
Placing a sample in or on the sample holder;
Securing a vacuum vessel of the sample loading device to the vacuum chamber and aligning with a hole in the vacuum chamber;
Evacuating the vacuum vessel;
Opening the hole in the vacuum chamber and manipulating an elongate probe to insert the sample holder into the opened hole so that the sample holder is thermally coupled to a cold object; Allowing the sample in or on the sample holder to be cooled as a result of heat conduction to the cold object;
a) decoupling the sample holder from the cold object and manipulating the elongated probe to insert the sample holder into the working area; or
b) enhancing the thermal coupling to the cold body to increase the heat flow taken away from the sample and further cooling the sample.   The sample holder is thermally coupled to the second heat shield before reaching the working area and is cooled by allowing heat to flow to the second heat shield; 23. The method of claim 22, wherein the second heat ray shield is decoupled and the sample holder is then inserted into the work area.   The method further comprising: following insertion into the working area, detaching the sample holder from the elongate probe, retracting the elongate probe, and then closing the hole closure system of the vacuum chamber. The method according to 22 or 23.

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