MAGNETIC RESONANCE SYSTEM WITH HEAT STORAGE IN THE OUTER VACUUM CHAMBER

Description

[0001] The present invention relates to a magnetic resonance system comprising a superconducting magnet coil assembly, an external vacuum chamber in which the superconducting magnet coil assembly is arranged, and a load assembly for ramping down the superconducting magnet coil assembly by introducing electric current from the magnet coil assembly into the load assembly. Furthermore, the present invention relates to a method for operating such a magnetic resonance system.

[0002] Modern magnetic resonance imaging (MRI) systems are usually implemented as "dry MRI systems" with a low helium content to save costs and reduce their reliance on helium. For this to be effective, it is essential that dry MRI magnets can self-ramp down (i.e., decouple power to reduce the magnetic field) in the event of a power or cooling failure to prevent a "quench" (the transition of the superconductor from the superconducting to the normal conducting state due to exceeding the transition temperature). During the ramp-down process, the energy stored in the magnetic field is released from the magnet as heat. Specifically, the energy is not stored within the cryoshield (the so-called "4K layer"), where it would take much longer to extract it. Instead, the energy is transferred to a heat storage device located outside the magnet, or outside the outer vacuum chamber (OVC).The current, which initially flows without resistance in the superconductor, is extracted from the magnet and passed through conduction diodes / resistors to transfer the magnetic or electrical energy as heat energy to a run-down load (RDL). The run-down load can be made of a cost-effective material with high heat capacity (e.g., aluminum) or as a "hybrid thermal storage device" (the material undergoes a phase transition during heat storage, e.g., paraffin).

[0003] For magnets with increasing field strength (> 1.5 T), however, aluminum storage units are relatively large and heavy. For example, with 3 T magnets, 200 to 300 kg of aluminum would be needed to absorb the energy of the field (8 to 15 MJ) and simultaneously keep the temperature of the load unit (RDL: Run Down Load) below 70 °C (critical contact temperature for service technicians).

[0004] These large aluminum masses are disadvantageous because they require a lot of space on the magnet, space that is needed for electronics. The increased weight makes transport difficult. For accessibility reasons, the mass usually has to be distributed asymmetrically, which can lead to altered dynamic vibration behavior (floor-born vibrations).

[0005] A cold head for an MRI system for cooling the superconducting magnet coils is described, for example, in the publication DE 11 2016 000 535 T5.

[0006] US Patent 2015 / 346299A1 discloses a cryo-free superconducting MRI magnet system. The magnet system is designed to monitor the condition of system components and, in the event of a predictable quench, to discharge the superconducting magnet at any desired discharge voltage.

[0007] From GB 2 420 858 A, superconducting magnets are known which have a primary superconducting magnet coil circuit and a complementary secondary coil circuit which together generate magnetic fields.

[0008] From US 2011 / 056 218 A1 a device for removing energy from a cryogenically cooled superconducting magnet is known.

[0009] The object of the present invention is therefore to provide an improved method for extracting energy from superconducting coils of a magnetic resonance system. According to the invention, this object is achieved by a magnetic resonance system according to claim 1 with a superconducting magnetic coil assembly, wherein the magnetic resonance system comprises an external vacuum chamber in which the superconducting magnetic coil assembly is arranged. The magnetic resonance system can, for example, be configured as a magnetic resonance imaging (MRI) scanner. It has superconducting magnetic coils to enable, for example, the generation of field strengths greater than 1.5 T with relatively low energy expenditure. For this purpose, the magnetic coils must be cooled down to, for example, 4 K. For this purpose, the superconducting coils are generally located in a so-called cryoshield, which in turn is arranged in an external vacuum chamber (OVC).A vacuum is usually provided between the outer vacuum chamber and the cryoshield to largely prevent heat transfer from the outside to the cooled, superconducting magnetic coils.

[0010] Furthermore, the magnetic resonance system has a first load unit for ramping down the superconducting magnet coil assembly by introducing electric current from the magnet coil assembly into the first load unit. The first load unit typically includes several diodes or resistors that convert the current flowing in the magnet coils into heat. This means that during ramping down, the current is deliberately diverted out of the superconducting magnet coils of the magnet coil assembly to reduce the magnetic field and dissipate the energy. Ramping down (also called run-down) thus corresponds to shutting down the magnet coil assembly by completely or partially switching off the magnetic field. The load unit usually also includes a heat storage device that absorbs and stores the heat produced by the diodes or resistors.The heat can also be transferred directly to the housing of the outer vacuum chamber, if necessary.

[0011] According to the invention, the load assembly is arranged at least partially within the outer vacuum chamber. This means, for example, that the entire load assembly is located in a vacuum between the cryoshield and the vacuum chamber. Optionally, however, the diode or resistor assembly can also be arranged within the vacuum chamber (OVC), and the first heat storage unit of the first load assembly can be located on the outside wall of the vacuum chamber. In this case, the heat from the diode or resistor assembly can penetrate the wall of the vacuum chamber (OVC) to reach the first heat storage unit. Because the load assembly is arranged at least partially within the outer vacuum chamber, less space is required for the load assembly outside, allowing the entire magnetic resonance system to be built more compactly.

[0012] According to the invention, the magnetic resonance system has a cooling circuit within the outer vacuum chamber, to which the first load device is connected for cooling, and a control unit which is configured to activate the cooling circuit only when the first load device is used for ramping down.

[0013] In one embodiment, the first load device is connected via a thermal conductor to a cold head, which is used to cool the superconducting magnet device. Such a cold head is described, for example, in German patent DE 11 2016 000 535 T5. A first stage of the cold head can cool the first load device between the outer vacuum chamber and the cryoshield. For this purpose, a first stage of the cold head can be connected to the first load device via the thermal conductor or thermally coupled. The second stage of the cold head can cool the superconducting magnet coils inside the cryoshield to, for example, 4 K. Thus, the cold head, which is actually used for cooling the superconducting magnet coils, can also be used to cool the first load device to, for example, 50 K.Thermal insulation can be improved by reducing the number of mechanical connections to the inside (i.e., towards the cryoshield). Further improvement can be achieved by encasing the cryoshield and / or the outer vacuum chamber with a film or structure with low infrared emissivity to reduce heat radiation.

[0014] According to a further embodiment, the superconducting magnet coil assembly, as just described, is arranged in a cryoshield within the outer vacuum chamber. The cold head protrudes through the outer vacuum chamber and the cryoshield, and the first load assembly is connected to the cold head between the outer vacuum chamber and the cryoshield via the thermal conductor. The cryoshield and the outer vacuum chamber essentially allow three temperature zones to be isolated from one another: an outer temperature zone of approximately 300 K, a middle temperature zone between the outer vacuum chamber and the cryoshield in the range of 50 K, and an inner temperature zone within the cryoshield of approximately 4 K for superconductivity.

[0015] In another embodiment, the magnetic resonance system incorporates a thermal switch within the thermal conductor, allowing control of the thermal conductivity of the conductor. The thermal conductor thermally couples the first load device and the cold head. Without the thermal switch, precise control of the cooling of the first load device would be impossible. The thermal switch enables the cooling of the first load device to be switched on or off. Optionally, the thermal switch can even be used to set intermediate states of the thermal conductivity of the conductor, thereby regulating the amount of cooling.The thermal switch makes it possible, for example, to first cool the components essential for superconductivity, namely the superconducting magnet coils, when ramping up the magnetic resonance system, and then, if necessary, to cool other components such as the first load device (RDL).

[0016] In a further embodiment, the first load device comprises a first diode arrangement and / or a first resistor arrangement, as well as a first heat storage unit for absorbing thermal energy from the first diode arrangement and / or resistor arrangement. The first load device is thus an electrical load that converts electrical current from the magnetic coil arrangement into heat. Diodes and resistors are particularly suitable for this purpose. For example, the first load device can comprise a plurality of diodes and / or resistors implemented in appropriate arrangements. The first heat storage unit can, for example, be made entirely or partially of copper or aluminum. These metals possess a relatively high heat capacity. Thus, the first load device not only converts the incoming current into heat but also stores this heat.The first heat storage unit can be located on the outside of the OVC.

[0017] In another embodiment, the magnetic resonance system has, in addition to the first load device inside the outer vacuum chamber, a second load device outside the outer vacuum chamber. This second load device is also configured to ramp down the superconducting magnet coil device by introducing electric current from the magnet coil device into the second load device. This means that, in this case, the electric current of the superconducting magnet coils can be introduced not only into the first load device but also into the second load device. In particular, both load devices can be operated simultaneously or alternatively. In principle, each individual load device is suitable for enabling the ramp-down of the superconducting magnet coil device, although this could take a correspondingly long time.

[0018] Using both load units simultaneously allows for faster ramp-down. Because the load units are located in different temperature zones (outside and inside the outer vacuum chamber), they can be cooled differently. This variation increases reliability.

[0019] In a further development, it may be provided that the second load unit comprises a second diode arrangement and / or a second resistor arrangement, as well as a second heat storage unit for absorbing heat energy from the second diode arrangement and / or second resistor arrangement, with the second heat storage unit being connected to a separate cooling system. The second load unit can, in principle, be constructed like the first load unit. However, it is usually sufficient if the second heat storage unit is designed, for example, as a cooling plate. This can be efficiently cooled by the separate cooling system. In this case, the second heat storage unit is, for example, cooled by a cooling medium flowing through it or past it.

[0020] In a further embodiment, the first and second load devices can be connected via a switching device to superconducting coils of the superconducting magnetic coil device, so that, depending on the switching state of the switching device, current from the superconducting coils can be introduced into the first and / or second load device. This switching device can include a superconducting switch. It is, for example, capable of switching a current of 500 to 700 A. Optionally, it is also capable of distributing the current between the two load devices. Naturally, the switching device also has a switching state in which no current is introduced from the superconducting coils.

[0021] Furthermore, the first heat storage unit can be designed to have a material that exhibits at least one phase transition within a specified temperature range inside the outer vacuum chamber. For example, if the first heat storage unit is filled with liquid nitrogen, the nitrogen's phase transition can be used for additional heat absorption. If solid nitrogen is used for the heat storage unit, two phase transitions at approximately 63 K and 77 K can even be utilized to absorb additional energy.

[0022] According to a further embodiment, the first load device is attached directly to the outer vacuum chamber. The first load device can therefore be mechanically supported by the outer vacuum chamber. It is advantageous to design the heat transfer of the support or attachment as efficiently as possible, so that the first load device can also dissipate heat directly to the outer vacuum chamber or its wall, if necessary. Whenever this document refers to the "outer vacuum chamber," it generally means the wall of this vacuum chamber.

[0023] In another embodiment, the magnetic resonance system within the outer vacuum chamber has a cooling circuit to which the first load device is connected for cooling. This cooling circuit can, for example, transfer heat from the first load device to the cold head. A suitable coolant must be selected that is liquid in the temperature range of approximately 50 K.

[0024] According to the invention, the magnetic resonance system includes a control unit configured to activate the cooling circuit only when the first load unit is used for ramping down. This means that the first load unit is not continuously cooled via the cooling circuit. This reduces the energy consumption of a pump and its potential for interference. Rather, the control unit is able to activate the cooling circuit only when the magnetic coil unit is to be ramped down, and in particular, only when the first load unit is also being used for ramping down.

[0025] The above-mentioned problem is also solved according to the invention by a method for operating a magnetic resonance system according to claim 11.

[0026] The advantages and variations mentioned in connection with the magnetic resonance system described above also apply analogously to the method according to the invention. In this case, the functional features of the magnetic resonance system mentioned correspond to the method features.

[0027] For use cases or application situations that may arise during the procedure and are not explicitly described here, it may be provided that, according to the procedure, an error message and / or a request for user feedback is issued and / or a default setting and / or a predetermined initial state is set.

[0028] The present invention will now be explained with reference to the accompanying figures. These show: FIG 1 a schematic view of a magnetic resonance system; FIG 2 a schematic view of components of a cooling system for cooling superconducting magnetic coils of a magnetic resonance system.

[0029] The exemplary embodiments described in more detail below represent preferred embodiments of the present invention. The scope of protection encompassed by the invention is defined by the claims.

[0030] FIG 1 Figure 1 shows a schematic representation of an exemplary embodiment of an MRI or magnetic resonance system.

[0031] The MRI system 1 comprises a magnet unit with a field magnet 3, which generates a static magnetic field for aligning the nuclear spins of an object 8, for example, a patient, within an imaging area. The imaging area is characterized by a highly homogeneous static magnetic field, the homogeneity referring in particular to the magnetic field strength and its amplitude. The imaging area is located in a patient tunnel 2, which extends longitudinally Z through the magnet unit. The field magnet 3 can, for example, be a superconducting magnet capable of generating magnetic fields with a magnetic flux density of up to 3 T or more. However, for lower field strengths, permanent magnets or electromagnets with normal-conducting coils can also be used. A patient table 7 can be movable within the patient tunnel 2.

[0032] Furthermore, the magnet unit comprises a gradient coil arrangement 5 with several gradient coils, which serve to superimpose gradient fields, i.e., location-dependent magnetic fields, in the three spatial directions onto the static magnetic field for the spatial differentiation of the scanned image areas in the imaging area. The gradient coils of the gradient coil arrangement 5 can, for example, be designed as coils made of normally conducting wires, which can generate fields or field gradients that are orthogonal to each other in the imaging area.

[0033] The magnetic unit comprises a transmitting coil arrangement, which may, for example, include a body coil 4 as a transmitting antenna configured to radiate a high-frequency signal into the imaging area. The body coil 4 can therefore be understood as the RF transmitting coil arrangement of the MRI system 1 or as part of the RF transmitting coil arrangement. In some embodiments, the body coil 4 can also be used to receive resonant MR signals emitted by the object 8. In this case, the body coil 4 can also be considered part of a signal acquisition device of the MRI system 1. Optionally, the signal acquisition device includes a local coil 6, which may be arranged in the immediate vicinity of the object 8, for example, on the object 8 or in the patient table 7. The local coil 6 can serve as a receiving coil or receiving antenna, either alternatively or in addition to the body coil 4.

[0034] The MRI system 1 also includes a control and computing system 9. The control and computing system 9 may include a transmit-receive control unit 10, which is connected to the body coil 4, the gradient coil array 5, and / or the local coil 6. Depending on the acquired MR signals, the transmit-receive control unit 10, which may include an analog-to-digital converter (ADC), can generate corresponding MR data, particularly in k-space. The transmit-receive control unit 10 may also be connected to the body coil 4 and control it to generate RF pulses, such as excitation pulses and / or refocusing pulses. Furthermore, the transmit-receive control unit 10 of the control and computing system 9 can also be connected to and control the gradient coil arrangement 5 in order to switch layer selection gradients, gradients for frequency and / or phase coding and / or readout gradients.

[0035] A computer within the control and computing system 9 can analyze the MR data and, for example, perform image reconstruction or parts thereof, or other computational tasks necessary during imaging. It should be noted that the described structure of the control and computing system 9 is only a non-exhaustive example. The various required tasks and functions may also be implemented differently and / or distributed across different control units and / or other computing units.

[0036] The MRI system 1 has, according to FIG 2 a cooling system to cool the magnetic coils 3 to temperatures at which they are superconducting.

[0037] In this example, the cooling system of the magnetic resonance system essentially has three temperature zones. The first temperature zone is in FIG 2 The outer temperature zone is marked with 300 K and roughly symbolizes the ambient temperature. This outer temperature zone is also located within an outer vacuum chamber 11. Inside the outer vacuum chamber 11 are the magnetic coils 3, which are surrounded by a cryoshield 12. Between the cryoshield 12 and the outer vacuum chamber 11 is a middle temperature zone, which is FIG 2 It is marked with 50 K. Typically, the temperature there is in the range of 40 to 70 K.

[0038] Within the cryoshield 12, where the magnetic coils 3 are located, lies the innermost temperature zone, which is in FIG 2 is marked with 4 K. In this temperature zone there is a helium cooling circuit 13 for cooling the magnetic coils 3.

[0039] Cooling is primarily achieved by a cold head 14. The cold head 14 transfers heat from the helium cooling circuit 13 within the cryoshield 12 to the outside through the outer vacuum chamber 11. For this purpose, the cold head 14 has a second cooling stage 15 to which the helium cooling circuit 13 is connected. A first cooling stage 16 of the cold head 14 is located in the vacuum between the outer vacuum chamber 11 and the cryoshield 12. This first cooling stage 16 can, for example, cool the temperature down to 50 K.

[0040] Within the outer vacuum chamber 11 is a first load device 17. This device represents an electrical load and includes, for example, a diode arrangement 18 that can convert electrical current into heat. To dissipate the heat, the first diode arrangement 18 is mounted on a first heat storage unit 19 and thermally connected to it. The first load device 17 can also be attached to the outer vacuum chamber 11 for mechanical support and heat dissipation.

[0041] The first load device 17 can draw current from the superconducting magnet coils 3 via a first current line 20 during a run-down ramp-down. During the conversion of the current by the first diode arrangement 18 (alternatively or additionally a resistor arrangement), heat is generated, which is dissipated via the first heat storage device 19, which is connected to a first cooling circuit 21.

[0042] The first cooling circuit 21 is connected to the first cooling stage 16 of the cold head 14. Optionally, the first cooling circuit 21 can have a thermal switch 22 with which the first cooling circuit 21 can be controlled or regulated. Alternatively, the first cooling circuit 21 can also be designed as a simple thermal conductor.

[0043] During the ramp-down phase, the current from the magnetic coils 3 initially flows via a main line 23 to an electrical switch 24, which may be superconducting. The switch directs the current into the first current line 20 or a second current line 25. The second current line 25 leads from the outer vacuum chamber 11 to a second load unit 26. The switch 24 thus allows the current from the superconducting magnetic coils 3 to be directed either to the first load unit 17 or to the second load unit 26, or optionally to both, for thermal conversion. The second load unit 26 has a second diode array 27, which receives the current from the second current line 25. Alternatively or additionally to the second diode array, the second load unit may have a second resistor array. Furthermore, the second load unit 26 has a second heat storage unit 28.The second heat storage unit 28 can be implemented as a cooling plate. Preferably, this is connected to a second cooling circuit 29 with a separate heat exchanger 30 and pump 31.

[0044] Due to its complexity, the cooling system shown is quite susceptible to malfunctions, which can also occur with varying frequency. For example, the following operating situations can occur: Operating situation 1: The water cooling (in FIG 2 (Not shown); cools the cold head 14) of the system. This fails due to a cooling system malfunction (e.g., pump failure) or a power outage without UPS (uninterruptible power supply) backup. Consequently, the magnet cooling also fails, and simultaneously, when the system shuts down, the heat from the first load unit 17 (RDL) cannot be dissipated because the cold head 14 is not running due to the lack of water circulation. The energy of the magnet or the magnet coils 3 must be completely stored in the first load unit 17 (e.g., at 50 K) and must be extracted again during cooling.

[0045] Operating situation 2: The magnetic cooling fails due to a fault in the compressor (MREF) located in FIG 2 The primary cooling device, not shown, is connected to the cold head 14. However, the water cooling in the second cooling circuit 29 continues through the second load unit 26. The energy of the superconducting magnetic coils 3 can be dissipated by the water circulation, and the second load unit 26 does not need to store all of the energy. All energy is stored outside the actual magnetic resonance system. Recooling of the first load unit 17 is not required in the event of a failure of the compressor or cold head 14, but the water cooling continues.

[0046] Compared to conventional run-down loads, a significant reduction in size and space requirements on the outside of the magnetic resonance system can be achieved by integrating the first load unit 17 into the outer vacuum chamber 11. This allows for thermal coupling of the first load unit 17 to the first stage of the cold head 14, which reaches a temperature of approximately 40 to 70 K in thermal equilibrium. The superconducting switch 24 of the magnetic resonance system can be opened so that the current from the main magnetic field is passed through the diode / resistor array 18 or 27, thereby converting the energy of the static magnetic field into heat. The diode array 18 or 27 is mounted on a respective heat storage unit 19, 28, which temporarily stores this energy until it is dissipated. This energy dissipation can be achieved using air, water, or other cooling methods. In particular, heat pipes can be used.

[0047] As mentioned, the first load unit 17 is located inside the outer vacuum chamber 11. It is thermally connected to the first stage of the cold head 14. For feasibility purposes, it can be estimated that the first stage of the cold head 14 generates approximately 60 W of cooling power at a temperature of approximately 70 K. To extract 12 MJ of energy from the first load unit 17 with a power output of 60 W, it takes 12 MJ / 60 / 3600 s = 55 h (without considering the temperature dependence of the heat capacity and without taking into account that the cold head 14 has a higher cooling capacity at higher temperatures). This would make the magnet operational again significantly faster after a shutdown or ramp-down than with a quench. A significant decrease in the heat capacity of aluminum only begins at approximately 100 to 150 K. This means that a dT of 140 K with full heat capacity is available to increase the temperature to 290 K.The mass of the aluminum heat storage unit 19 could therefore be: 12 MJ / (0.8 kJ / K / W) / 140 K = 100 kg. In practice, the buffer or heat storage unit can be even smaller, since the calculation assumed that the load device has no heat capacity between 70 and 150 K.

[0048] The load units and their heat storage components can be made of aluminum, copper, steel, or other materials with high heat capacity. Liquid nitrogen or helium, as well as combinations of all these materials, can also be used.

[0049] The first load device 17 is optionally connected to the cold head 14 via the thermal switch 22. The thermal switch 22 can be controlled by the magnetic electronics or by the system. As mentioned, it allows switching on / off or intermediate states of the heat transfer.

[0050] In addition to the first load unit inside the outer vacuum chamber 11, which can be cooled to approximately 50 K, a second, external load unit 26 exists. This second load unit 26 can be very small (e.g., only a few kilograms; less than 1 to 30 kilograms). It also contains a resistor or diode arrangement 27 and primarily serves to transfer heat to a flowing cooling medium (e.g., water, air). In a simplified embodiment, a cooling plate with a diode array suffices as the second load unit.

[0051] During operation, the central control unit of the magnetic resonance system can, for example, detect whether the water circulation of the primary cooling device (in the) is impaired in the event of a necessary shutdown. FIG 2(not shown) whether it is still functioning or not. It can thus differentiate between the two operating situations 1 and 2 described above. In the event of a fault as in operating situation 1, the central control unit of the magnetic resonance system will activate the first load device. In the event of a fault as in operating situation 2, the second load device will be activated. This advantageously increases the system's availability, as the long cool-down time of approximately 55 hours is only necessary in operating situation 1. In operating situation 2, the magnet is still cold and can be ramped up again immediately once the fault has been rectified.

[0052] The thermal switch 22 allows, for example, all critical components that enable the magnet's ramp-up to cool first, and the first load device to be cooled down only subsequently. The probability that a fault will occur precisely within these 50 hours, requiring the first load device to be cooled, is tolerable. The thermal switch can usually remain open during operation. Alternatively, it can be opened during the magnet's shutdown if this appears advantageous.

[0053] So-called hybrid cryogenic thermal storage units can be used. In one variant, liquid nitrogen can be used as the storage material. The corresponding hybrid thermal storage unit can consist of a metallic shell and a contents that undergo a phase transition upon heating. In this case, the filling consists of liquid nitrogen. With a specific heat capacity of approximately 2 kJ / kg / K, this has only a slightly higher heat capacity than, for example, aluminum at 0.88 kJ / kg / K. Additionally, the liquid nitrogen requires an energy of 200 kJ / kg for the phase transition. With 10 kg of nitrogen, a volume of 20 m³ would be generated at room temperature. At a pressure of 200 bar, this could be achieved in a 200-liter vessel. However, this provides only about 20 percent of the energy storage required for a 3-T magnet, amounting to 2000 kJ.

[0054] An alternative implementation would also allow the use of solid nitrogen as a cryogenic cold storage medium. This would make both phase transitions at approximately 63 K and 77 K usable. This equates to an additional 25 kJ / kg / K for nitrogen.

[0055] In an alternative approach, helium is used as a cryogenic heat storage medium. Magnetic resonance systems typically require a pressure vessel anyway to store helium in case of quenching or heating of the entire magnet. This pressure vessel is currently located outside the outer vacuum chamber (OVC) and could also be positioned in the space between the OVC and the cryoshield. This would save additional space outside the OVC and eliminate the need for helium lines and their penetrations through the OVC. This pressure vessel would require a large wall thickness (at 20 to 200 bar). Therefore, it is conceivable that the pressure vessel could simultaneously function as a hybrid RDL (Resonance Depth Device).In addition to helium's higher heat capacity compared to nitrogen, helium also has the advantage that synergies can be used, because the pressure vessel can thus perform two functions (store helium, and store heat in the case of a controlled ramp-down).

[0056] The cooling system has always been described above with two load devices 17 and 26. However, the invention can also be implemented with only the first load device 17 within the vacuum chamber 11. An implementation with both load devices is optionally possible.

[0057] The particular advantage of the cryogenic arrangement of the load device or heat storage according to the invention for shutting down "dry magnets" lies in the small space requirement, lower costs and a higher integration of the load device (RDL) into the magnetic resonance system as well as, if applicable, the use of synergies between the load device and the helium storage.

Claims

1. Magnetic resonance system (1) having - a superconducting magnetic coil facility (3), - an outer vacuum chamber (11) in which the superconducting magnetic coil facility (3) is arranged, and - a first load facility (17) for ramping down the superconducting magnetic coil facility (3), in that electrical current is introduced from the magnetic coil facility (3) into the first load facility (17), wherein - the first load facility (17) is arranged at least in part within the outer vacuum chamber (11), wherein the magnetic resonance system has a cooling circuit within the outer vacuum chamber (11), to which the first load facility (17) is connected for cooling, characterised in that - the magnetic resonance system has a control facility, which is configured to only set the cooling circuit into operation when the first load facility (17) is used for the ramping down.

2. Magnetic resonance system (1) according to claim 1, wherein the first load facility (17) is connected to a cold head (14) via a thermal conductor (21) which is used for cooling the superconducting magnetic facility (3).

3. Magnetic resonance system (1) according to claim 2, wherein the superconducting magnetic coil facility (3) is arranged in a cryoschield (12) within the outer vacuum chamber (11), the cold head (14) protrudes through the outer vacuum chamber (11) and the cryoshield (12), and the first load facility (17) is connected between the outer vacuum chamber (11) and the cryoshield (12) via the thermal conductor (21) to the cold head (14).

4. Magnetic resonance system (1) according to claim 2 or 3, which has a thermal switch (22) in the thermal conductor (21), wherein it is possible using the thermal switch (22) to control heat dissipation of the thermal conductor (21).

5. Magnetic resonance system (1) according to one of the preceding claims, wherein the first load facility (17) has a first diode arrangement (18) and / or resistor arrangement and a first heat storage unit (19) for receiving thermal energy from the first diode arrangement (18) and / or resistor arrangement.

6. Magnetic resonance system (1) according to one of the preceding claims, which in addition to the first load facility (17) within the outer vacuum chamber (11) has a second load facility (26) outside the outer vacuum chamber (11), wherein the second load facility (26) is also configured so as to ramp down the superconducting magnetic coil facility (3) in that electrical current is introduced from the magnetic coil facility (3) into the second load facility (26).

7. Magnetic resonance system (1) according to claim 6, wherein the second load facility (26) has a second diode arrangement (27) and / or second resistor arrangement and also a second heat storage unit (28) for receiving thermal energy from the second diode arrangement (27) and / or second resistor arrangement, and wherein the second heat storage unit (28) is connected to a separate cooling system (29).

8. Magnetic resonance system (1) according to claim 6 or 7, wherein the first and second load facility are connected via a switching facility (24) to superconducting coils of the superconducting magnetic coil facility (3) so that depending upon the switching state of the switching facility (24) current of the superconducting coils can be introduced into the first and / or second load facility.

9. Magnetic resonance system (1) according to one of claims 5 to 8, wherein the first heat storage unit (19) has a material which in a temperature range which is predetermined within the outer vacuum chamber (11) has at least one phase transition.

10. Magnetic resonance system (1) according to one of the preceding claims, wherein the first load facility (17) is fastened directly to the outer vacuum chamber (11).

11. Method for operating a magnetic resonance system (1) which has a superconducting magnetic coil facility (3), an outer vacuum chamber (11) in which the superconducting magnetic coil facility (3) is arranged, a first load facility (17) for ramping down the superconducting magnetic coil facility (3) which is arranged at least in part within the outer vacuum chamber (11), a cooling circuit within the outer vacuum chamber, to which the first load facility (17) is connected for cooling, and a control facility, wherein - electrical current within the outer vacuum chamber (11) is introduced from the magnetic coil facility (3) into the first load facility, characterised in that - the control facility only sets the cooling circuit into operation when the first load facility (17) is used for the ramping down.