Device for arrangement in a closed-circuit cryostat

Abstract

Device (1) for arrangement in a cryostat (2) with a closed circuit, comprising - a coil holder (6) having a first coil receiving area (10a) for attaching a first superconducting coil (31) to the first coil receiving area (10a); and - a support (7) on which the coil holder (6) is mounted and which has a support surface opposite the coil holder (6) for supporting the device (1) on a cooled contact surface (4) of the cryostat (2), wherein the support surface is thermally coupled to the first coil receiving area (10a) and wherein a vertical axis (9) of the device (1) is perpendicular to the support surface.

Description

[0001] The present invention relates to a device for arrangement in a closed-circuit cryostat, that is to say a device suitable for arrangement in such a cryostat, and to a system comprising a cryostat and such a device.

[0002] A closed-loop cryostat, also known as a dry cryostat, is a cooling system for achieving and maintaining very low temperatures of down to 4 K or below. Cooling is based on a closed, recirculating gas circuit, typically using helium as the gas. This is a significant difference and advantage over conventional open-loop cryostats, which require regular refilling of liquid coolants, such as liquid helium. In particular, this also enables continuous operation of closed-loop cryostats.

[0003] Closed-loop cryostats are used in a wide variety of applications, particularly where continuous operation and the avoidance of handling liquid coolant are desirable, such as in areas of materials science or physics research, particularly in experiments in quantum optics, quantum transport, single-particle microscopy, and so on.

[0004] Many of these examinations require a magnetic field. One way to generate such magnetic fields is to place the coils outside the cryostat, so that the area of the cryostat where the object under investigation is located is located inside the coil windings. Disadvantages of such solutions include the complex structure of the coil arrangements and their sensitivity to mechanical disturbances such as vibrations, as well as the increased space requirements. A further disadvantage is the possible need for additional cooling of the coils, especially with normally conducting coils.

[0005] It is an object of the present invention to provide an improved concept which makes it possible to generate a magnetic field in a closed-circuit cryostat, so that the aforementioned disadvantages are at least partially overcome.

[0006] This problem is solved by the subject matter of the independent claim. Advantageous further developments and preferred embodiments are the subject matter of the dependent claims.

[0007] The invention is based on the idea of providing a device which can be arranged in a closed-circuit cryostat and which has, on the one hand, a coil receiving area for attaching a superconducting coil and, on the other hand, a support surface for supporting the device on a cooled surface of the cryostat, wherein the support surface is thermally coupled to the coil receiving area.

[0008] According to one aspect of the invention, a device for arrangement in a closed-circuit cryostat is specified. The device comprises a coil holder with a first coil receiving area for attaching a first superconducting coil to the coil receiving area, for example, to an outer surface of the first coil receiving area. The device comprises a carrier on which the coil holder is mounted. The carrier has a support surface opposite the coil holder for supporting the device on a cooled surface, also referred to as a contact surface, of the cryostat. The support surface is thermally coupled to the first coil receiving area, for example, to the outer surface of the first coil receiving area. A vertical axis of the device is perpendicular to the support surface.

[0009] The vertical axis is, in particular, a virtual axis, which is used below primarily to define the positions and / or orientations of objects. In particular, the support surface of the carrier can define a bottom side of the device. Along the vertical axis, the support surface is located, for example, below the rest of the device. In particular, the coil holder is mounted on top of the carrier with respect to the vertical axis.

[0010] When reference is made here and in the following to a superconducting object, for example, the first superconducting coil, this can be understood to mean that the object consists of a superconductor or consists essentially of a superconductor. However, this does not necessarily mean that the object is always in a superconducting state. This is not the case if the temperature of the superconducting object is above the corresponding transition temperature, also known as the transition temperature or critical temperature.

[0011] The device does not necessarily include the first superconducting coil. However, in some embodiments, the device does include the first superconducting coil. Then, the first superconducting coil is attached to the first coil receiving area, in particular to the outer surface of the first coil receiving area, so that, in particular, a winding axis of the first superconducting coil is identical to or parallel to the vertical axis. This means, in particular, that turns of the first superconducting coil run along the outer surface.

[0012] The first superconducting coil is designed to be supplied with an electric current. A corresponding current or voltage source can be arranged, in particular, external to the device and, if necessary, external to the cryostat. Consequently, a magnetic field is generated by the first superconducting coil. The magnetic field is generated, among other things, in the volume encircled by the coil's windings. The magnetic field can be used, for example, to conduct examinations on an object under investigation.

[0013] If the first superconducting coil is in the superconducting state, a very high magnetic field strength can be achieved and the electrical losses through the first superconducting coil are extremely low.

[0014] Due to the thermal coupling of the first coil receiving area, in particular the outer surface of the first coil receiving area, with the support surface, the cooled surface of the cryostat is thermally coupled to the first superconducting coil when the device is used to examine the object under investigation in a magnetic field. Thus, the operation of the cryostat allows the first superconducting coil to be cooled very efficiently and without significant thermal losses, thus maintaining it in a superconducting state.

[0015] The thermal coupling between the first coil receiving area and the support surface can be achieved, for example, by providing an uninterrupted chain of components made of thermally conductive materials, in particular metals, which are in direct mechanical contact with each other in pairs, between the first coil receiving area and the support surface.

[0016] The device is suitable for being arranged in a closed-circuit cryostat, in particular for being arranged entirely within such a cryostat. The device can also be referred to as a device for arranging at least the first superconducting coil in a closed-circuit cryostat, wherein the entire device is suitable for being arranged in such a cryostat.

[0017] Since the entire device can be arranged inside the cryostat, i.e., in the cooled chamber of the cryostat, a particularly compact design is achieved, which is at best very low susceptibility to external mechanical disturbances. The direct placement within the cryostat enables significantly more efficient generation of the magnetic field compared to arrangements in which the coils are positioned outside the cryostat. This reduces energy consumption and minimizes interference from external fields. A further advantage is the use of the cryostat's cooling capacity to maintain the coil's superconducting state.

[0018] The coil holder can be made of aluminum or an aluminum alloy or copper or a copper alloy, for example.

[0019] Accordingly, particularly high mechanical stability and particularly good heat transfer are achieved.

[0020] According to at least one embodiment, the outer surface of the first coil receiving region is cylindrical or approximately cylindrical, in particular circular-cylindrical or approximately circular-cylindrical.

[0021] This makes it possible to increase the symmetry of the first superconducting coil attached to the outer surface of the first coil receiving area and the resulting magnetic field.

[0022] If the first superconducting coil is attached to the outer surface of the first coil receiving area, the windings of the first superconducting coil run in particular along the outer surface of the cylindrical shape.

[0023] According to at least one embodiment, an outer radius of the first coil receiving area lies in the range [60 mm, 150 mm] or in the range [70 mm, 100 mm]. According to at least one embodiment, an inner radius of the first coil receiving area lies in the range [50 mm, 140 mm] or in the range [60 mm, 90 mm].

[0024] The dimensions of the first coil receiving area thus defined allow, in particular, an optimal adaptation of the device to the typical internal dimensions of closed-circuit cryostats where the available space is limited.

[0025] According to at least one embodiment, a height of the device along the vertical axis is in the range [80 mm, 250 mm] or in the range [100 mm, 150 mm].

[0026] The dimensions of the first coil receiving area thus defined allow, in particular, an optimal adaptation of the device to the typical internal dimensions of closed-circuit cryostats where the available space is limited.

[0027] According to at least one embodiment, the coil holder has a second coil receiving area for attaching a second superconducting coil to the second coil receiving area, for example to an outer surface of the second coil receiving area, and the support surface of the carrier is thermally coupled to the second coil receiving area, in particular the outer surface of the second coil receiving area.

[0028] In such embodiments, the device does not necessarily include the second superconducting coil. However, in some embodiments, the device does include the second superconducting coil. Then, the second superconducting coil is mounted on the second coil receiving area, in particular on the outer surface of the second coil receiving area, so that, in particular, a winding axis of the second superconducting coil is identical to or parallel to the vertical axis. This means, in particular, that turns of the second superconducting coil run along the outer surface.

[0029] The statements and explanations regarding the first superconducting coil and the first coil receiving area apply analogously to the second superconducting coil and the second coil receiving area. This also applies in particular to the geometric shape of the second coil receiving area and the dimensions of the second coil receiving area.

[0030] By providing two superconducting coils, the total magnetic field strength can be further increased and / or the magnetic field strength and / or the spatial distribution of the magnetic field can be modified. In particular, a particularly homogeneous magnetic field can be generated, for example, between the two coils, especially when they are arranged coaxially.

[0031] According to at least one embodiment, the outer radius of the first coil receiving area is equal to the outer radius of the second coil receiving area. For example, the inner radius of the first coil receiving area can also be equal to the inner radius of the second coil receiving area.

[0032] According to at least one embodiment, a center point of the first coil receiving area, in particular of the cylindrical shape of the outer surface of the first coil receiving area, and a center point of the second coil receiving area, in particular of the cylindrical shape of the outer surface of the second coil receiving area, lie on the vertical axis. In particular, the first coil receiving area and the second coil receiving area are oriented identically.

[0033] For example, the support surface of the carrier is circular or approximately circular and the vertical axis passes through a center point of the support surface.

[0034] The concentration of the coil mounting areas on the vertical axis optimizes the space utilization within the cryostat, which is important for these devices since the available space is limited.

[0035] For example, the first superconducting coil and the second superconducting coil are arranged coaxially. This makes it easier to adjust the resulting magnetic field generated by the coils.

[0036] According to at least one embodiment, the first coil receiving area and the second coil receiving area are arranged axially offset from one another along the vertical axis.

[0037] According to at least one embodiment, the device comprises the first superconducting coil and / or the second superconducting coil.

[0038] In particular, the first superconducting coil is mounted on the first coil receiving portion such that a winding axis of the first superconducting coil is identical to or parallel to the vertical axis. In particular, the second superconducting coil is mounted on the first coil receiving portion such that a winding axis of the second superconducting coil is identical to or parallel to the vertical axis.

[0039] The first and / or second superconducting coil consists, for example, of a superconductor with a transition temperature that is greater than or equal to a temperature that can be generated by the cryostat in the cooled chamber of the cryostat. For example, the transition temperature is 77 K or less, 70 K or less, 20 K or less, or 10 K or less.

[0040] According to at least one embodiment, the coil holder at least partially encloses an interior space for receiving an object to be examined.

[0041] In particular, the first coil receiving area and, if applicable, the second coil receiving area encircle the interior tangentially with respect to the vertical axis.

[0042] This allows the object under investigation to be positioned in the most controllable and, if necessary, most homogeneous area of the generated magnetic field.

[0043] For example, the interior can be freely accessible from above, axially relative to the vertical axis. This allows the object to be examined to be easily inserted and removed from the interior without having to disassemble any parts of the device.

[0044] The device, in particular the coil holder and / or the carrier, can also have a mounting arrangement for mounting an object to be examined, in particular for fastening the object to be examined to the device and / or for securely holding the object to be examined in the device.

[0045] According to at least one embodiment, the coil holder has an opening between the first coil receiving area and the second coil receiving area, in particular in the axial direction between the first coil receiving area and the second coil receiving area, through which the interior is accessible from outside the device.

[0046] Thus, even after it has been arranged in the interior space, the object under investigation is easily accessible from the outside and can thus be manipulated, aligned, or the like, and / or further components, sensors, or the like can be easily introduced into the interior space and precisely positioned or removed from it. In applications in the field of optics, in particular quantum optics, the object under investigation, which may, for example, contain an optical resonator or optical microresonator for analyzing and / or manipulating a sample, can, for example, be aligned in the interior space in such a way that light from outside the device, but in particular within the cryostat, can be irradiated into the interior space, in particular the optical resonator or optical microresonator, and / or reflected, scattered, or transmitted radiation can exit the interior space and be detected.

[0047] According to at least one embodiment, the device comprises the object to be examined and the object to be examined is arranged in the interior space.

[0048] According to at least one embodiment, the object to be examined includes an optical resonator, also referred to as an optical cavity, in particular an optical microresonator, or the like.

[0049] The optical resonator can, for example, have two opposing mirrors, one or both of which are concave mirrors. One of the two mirrors can also be a planar mirror. One or both of the two mirrors can, for example, be formed by a respective axial end facet of an optical fiber. One or both of the two mirrors can, for example, be formed by a mesa structure, in particular a semiconductor mesa structure.

[0050] According to at least one embodiment, the device, for example a contact arrangement of the device, has a persistence switch arrangement which is configured to short-circuit the first superconducting coil.

[0051] The integration of the persistence switch assembly into the device offers advantages in the operation of the cryostat. By short-circuiting the first superconducting coil, it is placed in a persistent current state. This enables the coil to operate without a continuous power supply, reducing energy consumption and minimizing heat output within the cryostat. Since closed-loop cryostats rely on maintaining extremely low temperatures, reducing any heat output is particularly important. The persistence switch assembly thus contributes to improving the efficiency and stability of the investigations. Furthermore, the elimination of a continuous power supply increases operational reliability.The ability to operate the coil without external power supply is particularly advantageous in long-term experiments, as it ensures the reliability and continuity of the measurements.

[0052] In some embodiments, the persistence switch arrangement may be configured to short-circuit the second superconducting coil. In some embodiments, the device, for example the contact arrangement, comprises a further persistence switch arrangement configured to short-circuit the second superconducting coil.

[0053] The persistence switch arrangement enables a continuous current to be maintained in the first superconducting coil, even when no external voltage or current source is connected. The persistence switch arrangement can, for example, comprise another superconductor connected in parallel to the first superconducting coil and a heating element configured to heat the other superconductor above its transition temperature so that it transitions to the normally conducting state. In this state, the first superconducting coil can be supplied with a supply current; no current flows through the other superconductor in this state. To switch to continuous operation, the supply current can optionally be adjusted until a predetermined magnetic field generated by the first superconducting coil is reached. The heating element can then be deactivated.The remaining superconductor cools below its critical temperature and short-circuits the first superconducting coil. Then the supply current can be switched off.

[0054] According to at least one embodiment, the carrier has a base plate which forms the support surface, in particular an underside of the base plate forms the support surface.

[0055] In other words, it is provided, for example, that the carrier has a base plate as a base, which at the same time represents the support surface for the thermal coupling with the cryostat.

[0056] The use of the base plate as a support surface simplifies the design of the device and optimizes the heat transfer from the coil holder via the carrier to the cooled surface of the cryostat.

[0057] The base plate can be made of copper or a copper alloy, for example. This ensures excellent heat transfer while maintaining high mechanical stability.

[0058] According to at least one embodiment, the carrier has an intermediate body which is mechanically and thermally connected to the base plate and to the coil holder.

[0059] In other words, the intermediate body is arranged axially with respect to the vertical axis between the base plate and the coil holder.

[0060] The intermediate body, in particular an outer contour of the intermediate body, can, for example, have a cylindrical, in particular circular-cylindrical, basic shape, which is arranged in particular coaxially to the first coil receiving area and / or the second coil receiving area.

[0061] The intermediate body can, for example, be made of copper or a copper alloy.

[0062] Accordingly, particularly high mechanical stability and particularly good heat transfer are achieved.

[0063] According to at least one embodiment, the intermediate body has a flange which is in planar contact with a flange of the coil holder, in particular is connected thereto.

[0064] This allows for a mechanically very stable connection between the intermediate body and the coil holder and also for particularly good heat transfer.

[0065] The surfaces of the flanges that are in contact with each other are oriented in particular perpendicular to the vertical axis.

[0066] According to at least one embodiment, the intermediate body is screwed or riveted to the coil holder, in particular the flange of the intermediate body to the flange of the coil holder, and / or the intermediate body is screwed or riveted to the base plate.

[0067] Screwing or riveting allows for a particularly stable mechanical connection, which is particularly advantageous given the demanding conditions within the cryostat. Furthermore, it can achieve particularly good heat transfer.

[0068] The screwing or riveting can be realized in particular by a plurality of screws or rivets distributed, in particular evenly distributed, in the circumferential direction of the cylindrical basic shape of the intermediate body or in the circumferential direction of the flanges or the base plate.

[0069] According to at least one embodiment, the base plate is in direct mechanical contact with the intermediate body and the intermediate body is in direct mechanical contact with the coil holder.

[0070] This allows for a reduction in the number of contact areas between different components, which lowers the thermal resistance between the first coil receiving area and the base plate. The direct mechanical connection also increases the rigidity of the entire device and minimizes unwanted vibrations.

[0071] According to at least one embodiment, the device comprises a contact arrangement for electrically contacting the first superconducting coil. In particular, the contact arrangement comprises a first section comprising a first conductor for connecting to a first end of the first superconducting coil and a second conductor for connecting to a second end of the first superconducting coil. For example, the first conductor and the second conductor are made of a superconducting material, in particular of a superconducting material with a transition temperature of at least 30 K, or at least 40 K, or at least 70 K, or at least 90 K.

[0072] For example, the first superconducting coil consists of a superconductor with a transition temperature that is lower than the transition temperature of the superconducting material from which the first conductor and the second conductor are made.

[0073] The contact arrangement serves, in particular, to supply power to the first superconducting coil. As part of the device, the contact arrangement is particularly designed to be arranged inside the cryostat. The contact arrangement can accordingly be connected to an electrical current or voltage source by means of additional conductors, in particular cables, located outside or partially outside the cryostat.

[0074] By designing the first section with superconducting conductors, heat generation inside the cryostat can be further reduced. By selecting the transition temperatures described above, the first section can also be routed through less cooled regions, whose temperatures are particularly above the transition temperature of the first superconducting coil but still below the transition temperature of the first and second conductors, without the first and second conductors transitioning to the normally conducting state.

[0075] According to at least one embodiment, the device comprises a further contact arrangement for electrically contacting the second superconducting coil. In particular, the further contact arrangement comprises a further first section, which comprises a further first conductor for connection to a first end of the second superconducting coil and a further second conductor for connection to a second end of the second superconducting coil. For example, the further first conductor and the further second conductor consist of a superconducting material, in particular of a superconducting material with a critical temperature of at least 30 K, or at least 40 K, or at least 70 K, or at least 90 K.

[0076] For example, the second superconducting coil consists of a superconductor with a transition temperature that is lower than the transition temperature of the superconducting material from which the further first conductor and the further second conductor are made.

[0077] The additional contact arrangement serves, in particular, to supply power to the second superconducting coil. As part of the device, the additional contact arrangement is particularly designed to be arranged inside the cryostat. The additional contact arrangement can accordingly be connected to an electrical current or voltage source by means of additional conductors, in particular cables, located outside or partially outside the cryostat.

[0078] The statements and explanations regarding the contact arrangement apply analogously to the further contact arrangement.

[0079] According to at least one embodiment, the contact arrangement comprises a second section having a third conductor connected to the first conductor and a fourth conductor connected to the second conductor. In particular, the third conductor and the fourth conductor are made of copper or a copper alloy, in particular brass.

[0080] Accordingly, the first section can lead from the temperature level of the first superconducting coil or the contact surface of the cryostat, which is cooled to a predetermined target temperature of the cryostat, to another contact surface of the cryostat, which is cooled to a predetermined intermediate temperature that is greater than the target temperature but lower than an ambient temperature outside the cryostat. The second section can then lead from the further contact surface to the boundary between the cooled receiving space of the cryostat and the environment outside the cryostat. Since the third and fourth conductors are made of copper or a copper alloy, any transition temperature of the third and fourth conductors does not need to be considered in the region of the second section.

[0081] As a result, the first section of the contact arrangement reduces the heat input into the interior of the cryostat and the second section ensures that the first and second conductors are reliably kept in the superconducting state.

[0082] According to at least one embodiment, the further contact arrangement has a further second section, which has a further third conductor connected to the further first conductor, and a further fourth conductor connected to the further second conductor. In particular, the further third conductor and the further fourth conductor are made of copper or a copper alloy, in particular brass.

[0083] The statements and explanations regarding the contact arrangement apply analogously to the further contact arrangement.

[0084] According to a further aspect of the invention, a system is provided comprising a closed-circuit cryostat and a device according to the invention. The cryostat has a receiving space, in particular a closed receiving space, in which a contact surface of the cryostat is arranged. The cryostat is configured to cool the contact surface to a predetermined target temperature. The device is arranged within the receiving space such that the support surface rests on the contact surface, for example, rests completely on it.

[0085] The target temperature is determined in particular by the specific design of the cryostat and, for example, the coolant used in the cryostat. The target temperature can, for example, be less than or equal to 10 K, less than or equal to 5 K, or less than or equal to 4 K. In particular, the target temperature is lower than the transition temperature of the first superconducting coil and, if applicable, the second superconducting coil. The cryostat can, in particular, be designed according to a known embodiment.

[0086] According to at least one embodiment of the system, the device according to the invention is designed according to an embodiment in which the device has the contact arrangement as described above. The cryostat has a further contact surface and is configured to cool the further contact surface to an intermediate temperature that is greater than the target temperature. The first section of the contact arrangement extends between the further contact surface and the carrier, in particular the intermediate body, and / or between the further contact surface and the coil holder.

[0087] Further embodiments of the system according to the invention follow directly from the various embodiments of the device according to the invention, and vice versa. In particular, individual features and corresponding explanations as well as advantages relating to the various embodiments of the device according to the invention can be transferred analogously to corresponding embodiments of the system according to the invention.

[0088] Further features of the invention are evident from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or illustrated in the figures, can be encompassed by the invention not only in the respective combination specified, but also in other combinations. In particular, embodiments and combinations of features that do not have all the features of an originally formulated claim can also be encompassed by the invention. Furthermore, embodiments and combinations of features that go beyond or deviate from the combinations of features mentioned in the claims can also comprise the invention.

[0089] The invention will be explained in more detail below with reference to specific exemplary embodiments and corresponding schematic drawings. In the drawings, identical or functionally equivalent elements may be provided with the same reference numerals. The description of identical or functionally equivalent elements is not necessarily repeated with reference to the various figures.

[0090] The figures show Fig. 1 a schematic representation of an exemplary embodiment of a device according to the invention for arrangement in a closed-circuit cryostat and of such a cryostat; Fig. 2 a schematic representation of a part of another exemplary embodiment of a device according to the invention; Fig. 3 a schematic representation of a further exemplary embodiment of a device according to the invention; Fig. 4 a schematic representation of a part of a contact arrangement of a further exemplary embodiment of a device according to the invention; Fig. 5 is a schematic representation of part of a contact arrangement of another exemplary embodiment of a device according to the invention; and Fig. 6 a simplified circuit diagram of a persistence switch arrangement of a further exemplary embodiment of a device according to the invention.

[0091] In Fig. 1 schematically shows an exemplary embodiment of a device 1 according to the invention for arrangement in a cryostat 2 with a closed circuit. Furthermore, the cryostat 2 is also schematically shown. The device 1 has a coil holder 6 with a first coil receiving area 10a for attaching a first superconducting coil 31 to an outer surface of the first coil receiving area 10a. The device 1 has a carrier 7 on which the coil holder 6 is mounted. The carrier 7 has a support surface opposite the coil holder 6, in particular formed by the underside of a base plate 8 of the carrier 7, for supporting the device 1 on a cooled contact surface 4 of the cryostat 2, wherein the support surface is thermally coupled to the outer surface of the first coil receiving area 10a and wherein a vertical axis 9 of the device 1 is perpendicular to the support surface.The outer surface of the first coil receiving area 10a may, for example, be cylindrical or approximately cylindrical.

[0092] The coil holder 6 also includes, for example, a second coil receiving area 10b for attaching a second superconducting coil. The outer surface of the second coil receiving area 10b can also be cylindrical or approximately cylindrical. The outer radius of the first coil receiving area 10a can be the same as the outer radius of the second coil receiving area 10b.

[0093] The first coil receiving area 10a and the second coil receiving area 10b are arranged, for example, axially offset from one another along the vertical axis 9. The center of the first coil receiving area 10a and the center of the second coil receiving area 10b can lie on the vertical axis 9. The coil holder 6 can, for example, be designed as a single piece.

[0094] The coil holder 6 at least partially encloses an interior space 12 for receiving an examination object 18. The coil holder 6 has, for example, an opening between the first coil receiving area 10a and the second coil receiving area 10b, through which the interior space 12 is accessible from outside the device 1. For example, the first coil receiving area 10a and the second coil receiving area 10b are connected by a plurality of axially extending webs 13a, 13b, of which Fig. 1, two of which are visible, are connected to each other, and the said opening is formed between two of the webs 13a, 13b. Furthermore, the coil holder 6 can also have an opening on an axial upper side through which the interior space 12 is accessible from outside the device 1.

[0095] The coil holder 6 can be made of various materials, preferably a metal. In some examples, the coil holder 6 is made of aluminum or an aluminum alloy. In other examples, the coil holder 6 can be made of copper or a copper alloy.

[0096] The coil holder 6 comprises, for example, a flange 15, which can be used for mounting or connecting the coil holder 6 to the carrier 7.

[0097] The base plate 8 can be made of copper or a copper alloy, for example, and thus offers excellent thermal conductivity. This composition enables efficient heat transfer between the device 1 and the cooled contact surface 4 of the cryostat 2.

[0098] The carrier comprises, for example, an intermediate body 11, which is mechanically and thermally connected to the base plate 8 on the one hand and the coil holder 6 on the other. The intermediate body 11 has, for example, a cylindrical basic shape and ensures structural stability and heat transfer between the base plate 8 and the coil holder 6. The intermediate body 11 can be made of copper or a copper alloy, for example.

[0099] The intermediate body 11 comprises a flange 14, which is, for example, in surface contact with the flange 15 of the coil holder 6. The flange 14 of the intermediate body 11 can be connected to the flange 15 of the coil holder 6, in particular screwed by means of fastening screws 16, in order to ensure a secure mechanical connection and good heat transfer. Likewise, the intermediate body 11 can be screwed to the base plate 8 by means of fastening screws 17. This is shown for an exemplary embodiment in Fig. 2. The base plate 8 has radially outer elevations or reinforcements 19 to which the intermediate body 11 is screwed.

[0100] In particular, the base plate 8 is in direct mechanical contact with the intermediate body 11, and the intermediate body 11 is in direct mechanical contact with the coil holder 6. This arrangement creates a continuous thermal path from the base plate 8 to the coil holder 6 and thus an efficient heat transfer throughout the device 1.

[0101] The first superconducting coil 31 can be attached to the first coil receiving portion 10a of the coil holder 6 such that a winding axis of the first superconducting coil 31 is identical to or parallel to the vertical axis 9. The second superconducting coil can be attached to the second coil receiving portion 10b of the coil holder 6 such that a winding axis of the second superconducting coil is identical to or parallel to the vertical axis 9.

[0102] As shown schematically in Fig. 3, Fig. 4 and Fig. 5, the device 1 can have a contact arrangement for electrically contacting the first superconducting coil 31 with an external voltage or current source 29. The contact arrangement has a first section 21, which has a first conductor 24 for connection to a first end of the first superconducting coil 31, for example by means of a terminal 26, and a second conductor 25 for connection to a second end of the first superconducting coil 31, for example by means of a terminal 27. The first conductor 24 and the second conductor 25 consist of a superconducting material with a critical temperature of at least 30 K, for example YBCO. The first conductor 24 and the second conductor 25 can, for example, be attached to corresponding carrier bodies 22, 23. The contact arrangement can also have a heat sink 28, which is arranged between the carrier plate 23 and the intermediate body 11.

[0103] The contact assembly includes a second portion 30 having a third conductor connected to the first conductor 24 and a fourth conductor connected to the second conductor 24. The third conductor and the fourth conductor are made of brass, for example.

[0104] For example, the first section 21 can lead from the temperature level of the first superconducting coil 31 or the contact surface 4 of the cryostat 2 to another contact surface 5 of the cryostat 2, which is cooled to a predetermined intermediate temperature. The second section 30 can then lead from the other contact surface 5 to the boundary between the cooled receiving space of the cryostat 2 and the environment 3 outside the cryostat 2.

[0105] The device 1 may comprise a persistence switch arrangement 32, 33 designed to short-circuit the first superconducting coil 31, as shown schematically in Fig.6. The persistence switch arrangement 32, 33 enables a continuous current to be maintained in the first superconducting coil 31, even when the external voltage or current source 29 is disconnected. The persistence switch arrangement 32, 33 can, for example, comprise a superconductor 32 connected in parallel to the first superconducting coil 31, and a heating element 33 configured to heat the superconductor 32 above its transition temperature so that it transitions to the normally conducting state. In this state, the first superconducting coil 31 is supplied with supply current by the voltage or current source 29; no current now flows through the superconductor 32. To switch to continuous operation, the supply current is adjusted until the desired magnetic field is reached. Heating element 33 is then deactivated. The superconductor 32 cools below its transition temperature and short-circuits the first superconducting coil 31.The power supply can then be switched off. A similar arrangement can also be provided for the second superconducting coil. Reference symbol 1 device 2 cryostat 3 Surroundings 4 Contact surface 5 Contact surface 6 spool holders 7 carriers 8 Base plate 9 Vertical axis 10a, 10b Coil receiving areas 11 Intermediate body 12 Interior 13a, 13b Footbridges 14 Flange 15 Flange 16, 17 fixing screws 18 Subject of investigation 19 reinforcements Section 21 22 carrier bodies 23 carrier bodies 24 ladders 25 leaders 26 terminal 27 Terminal 28 heat sink 29 Power source Section 30 31 superconducting coil 32 superconductors 33 Heating element

Claims

[1] Device (1) for arrangement in a cryostat (2) with a closed circuit, comprising - a coil holder (6) having a first coil receiving area (10a) for attaching a first superconducting coil (31) to the first coil receiving area (10a); and - a support (7) on which the coil holder (6) is mounted and which has a support surface opposite the coil holder (6) for supporting the device (1) on a cooled contact surface (4) of the cryostat (2), wherein the support surface is thermally coupled to the first coil receiving area (10a) and wherein a vertical axis (9) of the device (1) is perpendicular to the support surface. [2] Device (1) according to claim 1, wherein the first coil receiving area (10a) has an outer surface for attaching the first superconducting coil (31) to the outer surface and wherein the support surface is thermally coupled to the outer surface of the first coil receiving area (10a). [3] Device (1) according to claim 2, wherein the outer surface of the first coil receiving area (10a) is cylindrical or approximately cylindrical. [4] Device (1) according to claim 3, wherein - an outer radius of the first coil receiving area (10a) lies in the range [60 mm, 150 mm] or in the range [70 mm, 100 mm]; and / or - an inner radius of the first coil receiving area (10a) is in the range [50 mm, 140 mm] or in the range [60 mm, 90 mm]. [5] Device (1) according to one of the preceding claims, wherein - the coil holder (6) has a second coil receiving area (10b) for attaching a second superconducting coil to the second coil receiving area (10b), and - the support surface is thermally coupled to the second coil receiving area (10b). [6] Device (1) according to claim 5, wherein the second coil receiving area (10a) has an outer surface for mounting the second superconducting coil and wherein the support surface is thermally coupled to the outer surface of the second coil receiving area (10b). [7] Device (1) according to claim 6, wherein the outer surface of the second coil receiving area (10b) is cylindrical or approximately cylindrical. [8] Device (1) according to one of claims 3 or 4 and claim 7, wherein an outer radius of the first coil receiving area (10b) is equal to an outer radius of the second coil receiving area (10b). [9] Device (1) according to one of claims 3 or 4 and one of claims 7 or 8, wherein a center point of the first coil receiving area (10a) and a center point of the second coil receiving area (10b) lie on the vertical axis (9). [10] Device (1) according to one of claims 6 to 9, wherein the first coil receiving area (10a) and the second coil receiving area (10b) are arranged axially offset from one another along the vertical axis (9). [11] The device (1) according to any one of claims 6 to 10, wherein the device (1) comprises the second superconducting coil mounted on the second coil receiving portion (10b) such that a winding axis of the second superconducting coil is identical or parallel to the vertical axis (9). [12] Device (1) according to one of the preceding claims, wherein - the coil holder (6) at least partially encloses an interior space (12) for receiving an object to be examined (18); or - the device (1) has an object to be examined (18) and the object to be examined (18) is arranged in an interior space (12) at least partially enclosed by the coil holder (6). [13] Device (1) according to claim 12 and one of claims 6 to 11, wherein the coil holder (6) has an opening between the first coil receiving area (10a) and the second coil receiving area (10b) through which the interior space (12) is accessible from outside the device (1). [14] Device (1) according to one of the preceding claims, wherein a height of the device (1) along the vertical axis (9) is in the range [80 mm, 250 mm] or in the range [100 mm, 150 mm]. [15] Device (1) according to one of the preceding claims, wherein the device (1) comprises the first superconducting coil mounted on the first coil receiving portion (10a) such that a winding axis of the first superconducting coil (31) is identical or parallel to the vertical axis (9). [16] Device (1) according to one of the preceding claims, wherein the device (1) comprises a persistence switch arrangement (32, 33) arranged to short-circuit the first superconducting coil (31). [17] Device (1) according to one of the preceding claims, wherein the carrier (7) has a base plate (8) which forms the support surface. [18] Device (1) according to claim 17, wherein the base plate (8) is made of copper or a copper alloy or aluminum or an aluminum alloy. [19] Device (1) according to one of claims 17 or 18, wherein the carrier (7) has an intermediate body (11) which is mechanically and thermally connected to the base plate (8) and to the coil holder (6). [20] Device (1) according to claim 19, wherein the intermediate body (11) has a cylindrical basic shape. [21] Device (1) according to one of claims 19 or 20, wherein the intermediate body (11) has a flange (14) which is in planar contact with a flange (15) of the coil holder (6). [22] Device (1) according to claim 21, wherein - the flange (14) of the intermediate body (11) is screwed, riveted, soldered or welded to the flange (15) of the coil holder (6); or - the intermediate body (11) is screwed or riveted to the coil holder (6). [23] Device (1) according to one of claims 19 to 22, wherein the intermediate body (11) is screwed, riveted, soldered or welded to the base plate (8). [24] Device (1) according to one of claims 19 to 23, wherein the base plate (8) is in direct mechanical contact with the intermediate body (11) and the intermediate body (11) is in direct mechanical contact with the coil holder (6). [25] Device (1) according to one of claims 19 to 24, wherein the intermediate body (11) consists of copper or a copper alloy or aluminum or an aluminum alloy. [26] Device (1) according to one of the preceding claims, wherein the coil holder (6) is made of aluminum or an aluminum alloy or copper or a copper alloy. [27] Device (1) according to one of the preceding claims, wherein the carrier (7) has a mounting arrangement for mounting an object to be examined (18). [28] Device (1) according to one of the preceding claims, wherein - the device (1) has a contact arrangement (21, 30) for electrically contacting the first superconducting coil (31); - the contact arrangement (21, 30) has a first section (21) which has a first conductor (24) for connection to a first end of the first superconducting coil (31) and a second conductor (25) for connection to a second end of the first superconducting coil (31); and - the first conductor (24) and the second conductor (24) consist of a superconducting material having a transition temperature of at least 30 K or at least 40 K or at least 70 K or at least 90 K. [29] Device (1) according to claim 28, wherein - the contact arrangement (21, 30) has a second section (30) having a third conductor connected to the first conductor (24) and a fourth conductor connected to the second conductor (25); and - the third conductor and the fourth conductor are made of copper or a copper alloy, in particular brass. [30] System comprising a closed-circuit cryostat (2) and a device (1) according to one of the preceding claims, wherein - the cryostat (2) has a receiving space in which a contact surface (4) is arranged, wherein the cryostat (2) is designed to cool the contact surface (4) to a predetermined target temperature; and - the device (1) is arranged within the receiving space so that the support surface rests on the contact surface (4). [31] System according to claim 30, wherein the device (1) is designed according to one of claims 28 or 29 and - the cryostat (2) has a further contact surface (5) and is designed to cool the further contact surface (5) to an intermediate temperature which is greater than the target temperature; and - the first section (21) of the contact arrangement runs between the further contact surface (5) and the carrier (7) and / or between the further contact surface (5) and the coil holder (6).

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