EP3467852B1 - Magnet assembly with cryostat and magnet coil system, with cold storage at the power connections - Google Patents

Magnet assembly with cryostat and magnet coil system, with cold storage at the power connections Download PDF

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Publication number
EP3467852B1
EP3467852B1 EP18198875.9A EP18198875A EP3467852B1 EP 3467852 B1 EP3467852 B1 EP 3467852B1 EP 18198875 A EP18198875 A EP 18198875A EP 3467852 B1 EP3467852 B1 EP 3467852B1
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EP
European Patent Office
Prior art keywords
cold
magnet assembly
current leads
cryostat
coil system
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EP18198875.9A
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German (de)
French (fr)
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EP3467852A1 (en
Inventor
Patrick Wikus
Jörg Hinderer
Marco Strobel
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Bruker Switzerland AG
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Bruker Switzerland AG
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/06—Coils, e.g. winding, insulating, terminating or casing arrangements therefor
    • H01F6/065—Feed-through bushings, terminals and joints
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/06—Coils, e.g. winding, insulating, terminating or casing arrangements therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/04—Cooling

Definitions

  • the invention relates to a magnet arrangement comprising a cryostat, a superconducting magnet coil system, an active cooling device for the magnet coil system and power supply lines for charging the magnet coil system in the cryostat, wherein the power supply lines comprise at least one normally conducting area, in particular wherein the power supply lines also include an HTS area, wherein a plurality of cold stores are thermally coupled to the power supply lines along the normally conductive area of the power supply lines in order to absorb heat generated in the normally conductive area when the magnetic coil system is charged.
  • Such a magnet arrangement is from the JP H04 23305 A known.
  • the superconducting magnetic coil systems can carry large electrical currents without loss, with which the strong magnetic field strengths are generated.
  • cooling to cryogenic temperatures below the transition temperature of the superconducting material in the magnet coil system is necessary for the superconducting state.
  • the superconducting magnetic coil systems are therefore arranged in a cryostat.
  • active cooling devices are used in some cases, e.g. Pulse tube cooler with which a cryogenic temperature can be maintained permanently and inexpensively.
  • the thermal load during charging is due to several effects (eg operation of the "persistent mode switch" or ohmic dissipation in the Power supply) significantly larger than in normal operation.
  • the active cooling device can be dimensioned so large that the heat load of the charging also takes into account the cooling device can be compensated.
  • this leads to high production costs and high maintenance costs, to a large size and to requirements for cooling and power supply, which must be based on the peak performance required for charging. Since charging typically only takes a few hours, but normal operation usually takes many weeks or months, most of the time the active cooling device is not used to capacity.
  • cryogenic containers of the cryostat filled with a liquid cryogen such as liquid helium
  • a high consumption of coolant can simply be accepted during charging, but this entails high costs.
  • Power supplies for a superconducting magnet system are known, on which heat storage material is arranged.
  • the power supply lines are tubular and the heat storage material is arranged in the tube, the heat storage material being divided inside the tube by layers of a thermally insulating material.
  • the power supplies are cooled with a stream of helium gas.
  • the invention has for its object to provide a magnet arrangement in which a reduced cooling capacity is required during charging of the superconducting magnet coil system, and a heat input into the superconducting magnet coil system is reduced during normal operation.
  • a magnet arrangement of the type mentioned at the outset which is characterized in that the current leads in the normally conductive region have a variable cross-sectional area B along their direction of extension, whereby the cross-sectional area B decreases from a cold end to a warm end over at least a predominant part of the total length of the current leads in the normally conductive region.
  • the power supply lines in their normally conductive area with a special geometry in order to optimize the power supply lines for charging requirements on the one hand and in normal operation on the other hand, with several cold stores on the power supply lines thermally along the normally conductive area of the power supply lines are coupled.
  • the invention therefore provides for the cross-sectional area to be increased towards the cold end (perpendicular to the longitudinal extension or current flow direction), so that the ohmic resistance towards the cold end is reduced insofar as it is caused by the cross-sectional area. This also reduces heat generation near the cold end.
  • the cross-sectional area of the power supply lines is reduced towards the end at room temperature, which increases the heat conduction resistance, insofar as it is caused by the cross-sectional area.
  • the simultaneous distribution of several cold stores along the power supply lines in the normally conductive area ensures that the local limitations in the heat development and heat input achieved by the geometry of the power supply lines can be used over a long period of time, and in particular are not quickly compensated for by heat conduction along the power supply lines can.
  • the cold stores slow down the compensation processes;
  • the duration of a complete charging process can be buffered by suitable dimensioning of the cold storage (and suitable geometry of the power supply lines).
  • the power supply lines in the normally conductive area typically run from a connection at room temperature (warm end) to the magnet coil system or up to an HTS area (or HTS section) of the power supply lines (cold end); the power supply in the HTS area then continues to the solenoid system.
  • the magnetic coil system typically has a superconducting short-circuit switch for setting up continuous current operation (persistent mode).
  • the short-circuit switch can preferably be operated with a low heating current or a low heating power, for example with 50 mW or less.
  • LTS low-temperature superconductor
  • the operating current of the magnetic coil system is advantageously low in normal operation, approximately 100 A or less, preferably 70 A or lower.
  • the magnet coil system can preferably be charged with high charging voltages, for example with 5 V or more.
  • the active cooling device can in particular be a pulse tube cooler or a Gifford-McMahon cooler.
  • a preferred power consumption of the active cooling device is 2 kW or less, in particular 1.5 kW or less.
  • the active cooling device is preferably operated without cooling water or air-cooled.
  • the cross-sectional area B of the current leads in the normally conductive region typically decreases over the entire length of the normally conductive region from the cold end to the warm end, but at least over a predominant proportion of the total length of the current leads in the normally conductive region.
  • the reduction in cross-section can take place continuously or in stages or in a mixed form.
  • connection points usually have a smaller cross-sectional area B ("soldering point"), less frequently a larger cross-sectional area (“soldering bead”) than the surrounding power supply parts.
  • the cross-sectional area B preferably decreases from the cold end to the warm end over a proportion of at least 95%, preferably at least 98%, of the total length of the current leads in the normally conductive area within the cryostat.
  • the active cooling device is preferably arranged within a tube which is filled with gas during operation (in particular during charging and normal operation); then the active cooling device can be removed or replaced without breaking the insulation vacuum of the cryostat.
  • this tube can be provided for one of the power supplies; this is there anyway and therefore the heat load does not increase further during normal operation.
  • This tube can also be the neck tube of the cryostat, in particular one of the current leads also running in the neck tube. Any excess cooling capacity that is available on a regenerator of the active cooling device can be used for cooling the power supply by thermal contact via the gas in the tube.
  • a preferred embodiment of the magnet arrangement according to the invention provides that the current leads in the normally conductive region each have N consecutive sections, with N ⁇ 2, in particular 3 ⁇ N ⁇ 7, the sections each having a constant cross-sectional area Bi within a section, and that the cross-sectional areas Bi decrease from the cold end to the warm end.
  • This embodiment is structurally simple to implement;
  • the thermal behavior during a charging process can be simulated relatively easily and the geometry of the power supply lines can be optimized accordingly. With a large number of sections, heat flow and heat development or the temperature distribution in the power supply lines can be adjusted more precisely.
  • this setting can also be further optimized via the Bi / Hi ratios, with Hi: length of the section i (along the longitudinal direction / current flow direction).
  • N ⁇ 3 or N ⁇ 4 also applies.
  • at least one coupled cold store is provided for each section.
  • different sections are thermally coupled to different cold stores.
  • the cold stores only have a (direct) coupling to one of the sections; a connection to other sections is only made indirectly via the former section. This facilitates the formation of a strong temperature gradient in the power supply lines.
  • the cold stores can contact the subareas, for example, approximately in the middle (with respect to the direction of extension).
  • At least one cold accumulator is thermally coupled to a transition from two subsections, in particular wherein at least one cold accumulator is also thermally coupled to the cold end of the power supply in the normally conductive area is.
  • This is usually structurally particularly simple.
  • One or more cold stores at the cold end provide particularly good protection for the superconducting magnetic coil system (or an HTS area of the power supply lines).
  • K stages of the thermal coupling are set up along the current leads in the normally conductive region, at least one cold store being thermally coupled to the current leads at each stage, with K ⁇ 2, especially 3 ⁇ K ⁇ 7.
  • K ⁇ 3 or K ⁇ 4 is also advantageous.
  • the heat flow or the temperature distribution in the power supply lines can be adjusted more precisely by a larger number of stages of the thermal coupling.
  • the cold stores are used more thermodynamically efficiently.
  • a stage of the thermal coupling corresponds to contacting a power supply through one or more cold stores at a specific length position along the power supply; Different levels of thermal coupling contact a power supply in the normally conductive area, i.e. at different length positions.
  • a further development of this embodiment is advantageous, in which a heavy mass Mi of cold-storing material in the at least one cold store of a respective stage of the thermal coupling decreases over the stages from the cold end to the warm end.
  • the specific heat capacity of most cold-storing materials increases sharply with higher temperatures (in the cryogenic area), so that such large (absolute) heavy masses are not required towards the warm end.
  • the concept of the "heavy” (ie weight-generating) mass of a cold store is used here in order to avoid confusion with the "thermal mass” (ie the absolute heat capacity).
  • cryostat is designed as a cryogen-free cryostat.
  • an increased heat load during charging cannot be compensated for by accepting an increased cryogen consumption during charging.
  • the invention enables the use of an active cooling device with a low cooling capacity, which is inexpensive and compact.
  • a cryostat is considered to be cryogen-free if cryogens cannot escape from the system in any operating condition to be expected (i.e. not even when loading or during a quench).
  • the magnet coil system is typically arranged directly in the vacuum of the vacuum container (and in particular not in a cryogen tank with liquid cryogen, in which the magnet coil system is immersed).
  • An embodiment is also preferred in which at least some of the cold stores are designed as gas-tight containers, with some of the volume of the gas-tight containers being filled with an evaporable substance.
  • thermal energy can be bound by evaporating the substance which can be evaporated (at the temperatures prevailing during operation).
  • the vaporizable substance can be, for example, nitrogen, krypton or argon, and in a colder area it can also be neon or helium.
  • the evaporable (mostly liquid) substance essentially provides the "heavy mass" of the respective cold store.
  • the container is typically made of a poorly heat-conductive material, such as stainless steel or titanium alloy 15-3-3-3. Typically, several containers are connected in series along the power supply lines.
  • At least some of the containers are thermally coupled with a lower end to a heat sink of the active cooling device via a heat-conducting element, and the boiling point of the substance contained in the container is above the temperature of the heat sink.
  • Heat can be slowly removed from the container (after loading) via the heat-conducting element in order to recondense the vaporized substance, typically slowly over several hours or even several days.
  • two containers can be used in series, which are coupled to two different cooling stages of the active cooling device (such as a pulse tube cooler).
  • An embodiment is also preferred in which at least some of the cold stores are designed as metallic bodies. This design is particularly simple and robust. Good thermal contact between the (metallic) power supply lines in the normally conductive area and the metallic bodies is easy to set up directly.
  • An embodiment is advantageous in which a plurality of cold stores designed as metallic bodies are arranged spaced apart from one another in a vacuum region of the cryostat. This easily avoids thermal short-circuits of the cold stores, in particular between cold stores of different stages of the thermal coupling.
  • An embodiment is particularly preferred in which there is also an active auxiliary cooling device which is thermally coupled to a part (section) of the power supply lines in the normally conductive region, in particular where a lowest working temperature AT helps Auxiliary cooling device is higher than a lowest working temperature AT mss of the active cooling device for the magnet coil system.
  • auxiliary cooling device With the auxiliary cooling device, additional heat energy can be extracted from the power supply lines, particularly when charging; this can relieve the load on the active cooling device (which is primarily intended to cool the magnetic coil system).
  • the auxiliary cooling means typically has a AT Helpful in a range of -70 ° C to -30 ° C, usually from -60 ° C to -50 ° C, which is relatively easy to achieve (especially low-power); however, AT mss is usually 4 K to 10 K (-269 ° C to -263 ° C).
  • An auxiliary cooling device or a corresponding cooling coil (associated heat exchanger) is typically arranged in the vacuum container (in a vacuum).
  • auxiliary cooling device is furthermore thermally coupled to a radiation shield of the cryostat and / or a vacuum container of the cryostat and / or a temperature control device for a sample to be examined.
  • the active cooling device is additionally relieved, in particular in normal operation.
  • the auxiliary cooling device is used to cool the vacuum container of the cryostat below the ambient temperature, it is advantageous to thermally insulate the vacuum container. For this, e.g. Plastic foams. With this e.g. Condensation can be prevented.
  • the cross-sectional area B changes from the cold end to the warm end by at least a factor 3.
  • a factor of 3 or more can already significantly reduce the load on the active cooling device with regard to the heat load during charging.
  • a magnet arrangement also falls within the scope of the present invention, wherein the magnet coil system is charged via the power supply lines and a charging current is selected and the variable cross-sectional area B and / or the cold storage devices are set up in such a way that they charge for a heat load WL which has a maximum effect on a coldest stage of the power supply lines in the normally conductive area during charging , and for a heat load WL gg to this coldest stage in an equilibrium state with charged solenoid system: WL load ⁇ 5 * WL gg, especially WL load ⁇ 2 * WL gg.
  • the coldest level (or level of thermal coupling) is the area of the power supply to which the cold end next cold storage (or cold storage set at the same length position on the power supply lines ) is thermally coupled.
  • the specified ratios are easy to achieve within the scope of the invention and enable the use of active cooling devices (cryocoolers) with low cooling capacity, which is inexpensive, enables a compact construction of the magnet arrangement and contributes to the integration of the system in a customer laboratory as easily as possible possible.
  • the Fig. 1 shows schematically a first embodiment of a magnet arrangement 1 according to the invention.
  • This comprises a cryostat 2, a magnet coil system 3, an active cooling device 4 and here two current leads 5a, 5b for charging the magnet coil system 3.
  • the cryostat 3 is designed here with a vacuum container 11, an outer radiation shield 6, a middle radiation shield 7 and an inner radiation shield 8.
  • the vacuum container 11, which simultaneously forms the outer wall of the cryostat 2 is at room temperature (approx. 20 ° C.).
  • the outer radiation shield 6 is at approx. 213 K (approx. -60 ° C).
  • the middle radiation shield 7 couples to an upper cooling stage 9 of the active cooling device 4 at approximately 50 K, and the inner radiation shield 8 couples to a lower cooling stage 10 of the active cooling device at approximately 3.5 K; the latter also represents the lowest working temperature AT mss of the active cooling device 4.
  • the magnetic coil system 3 is arranged in a vacuum, which can be superconductively short-circuited via a switch 12 of a charging and short-circuit circuit 12a.
  • the magnetic field generated by the magnetic coil system 3 can be used in normal operation, for example for an NMR measurement.
  • the inner radiation shield 8 can also be gas-tight, so that to improve the thermal conductivity, for example, some gaseous helium can be provided or contained, which, however, does not have to be filled in during operation (including charging and normal operation) and cannot escape ( "cryogen-free cryostat").
  • the cryostat 2 can also be designed as a cryogen-containing cryostat (in Fig. 1 not shown).
  • a cryogenic container is provided, which typically contains liquid cryogen (such as helium), in which the magnetic coil system 3 is completely or partially immersed.
  • the cryogen in the cryocontainer can be refilled in the cryogen-containing cryostat during operation, if necessary also during loading.
  • the current leads 5a, 5b lead from connections 13a, 13b on the vacuum container 11 through the cryostat 3 to connections 14a, 14b on the charging and short-circuit circuit 12a.
  • the power supply lines 5a, 5b each comprise a normally conducting area 15a, 15b (between vacuum container 11 and middle radiation shield 7), an HTS area 16a, 16b (between middle radiation shield 7 and inner radiation shield 8) and an LTS area (inside the inner radiation shield 8).
  • the current supply lines 5a, 5b in the normally conductive area 15a, 15b each have a cross-sectional area B which decreases continuously from the cold (near the magnetic coil system) end 18a, 18b to the warm (near the room temperature connection) end 19a, 19b, as can be seen from an upward direction reducing diameter;
  • the cross-sectional area B is drawn approximately in the middle (along the longitudinal direction) of the current leads 5a, 5b in the normally conductive region 15a, 15b.
  • the cross-sectional area B is reduced by a factor of approximately 3 in the exemplary embodiment shown (note that the diameter is square in the cross-sectional area B, the cold to warm diameter ratio being approximately 1.75 here).
  • the reduction in cross-section is established here over the entire (vertical) length of the current leads 5a, 5b in the normally conductive region 15a, 15b.
  • Cold accumulators 20 are coupled to the supply leads 5a, 5b in the normally conductive area 15a, 15b.
  • the cold stores 20 are designed here as metallic masses 20a.
  • three stages 21, 22, 23 of the thermal coupling are set up, two cold stores 20 (left and right) at each of the stages 21, 22, 23 at the same length position (the length direction runs in Fig. 1 vertically) are coupled.
  • the cold stores 20 of the coldest stage 21 have a total heavy mass M1 which is greater than the total heavy mass M2 which the cold stores 20 of the middle stage 22, and the total heavy mass M2 of the cold stores 20 of the middle stage 22 is again greater than the total Heavy mass M3 of the cold accumulator 20 of the warmest stage 23.
  • the cold accumulator 20 of the different stages 21-23, and here also within the stages 21-23, are spaced apart from one another in the vacuum region 11a of the vacuum container 11 in order to avoid a thermal short circuit.
  • the power supply lines 5a, 5b are coupled to the central radiation shield 7, so that a certain cooling capacity of the upper cold stage 9 of the active cooling device 4 can be used.
  • the outer radiation shield 6 contacts the current leads 5a, 5b in the normally conductive area 15a, 15b, here between the stages 22 and 23; alternatively, a non-coupling passage can also be provided on the outer radiation shield 6.
  • the heat load (heat flow "downwards") in the area of the lowest stage 21 when loading WL can be limited compared to the heat load in equilibrium in normal operation WL gg , so that WL laden ⁇ 2 * WL gg. Load the remaining heat load WL can be compensated for by the active cooling device 4, so that the superconducting magnet coil system 3 and also not the HTS region 16a, 16b of the power supply lines 5a, 5b heat up inadmissibly (above the respective transition temperature).
  • the Fig. 2 shows a second embodiment of a magnet arrangement 1 according to the invention, which largely corresponds to the design of Fig. 1 corresponds; only the main differences are explained below.
  • the cryostat 2 here only has an outer radiation shield 6, which is coupled to the upper cooling stage 9 of the active cooling device 4, and an inner radiation shield 8, which is coupled to the lower cooling stage 10, but not via a middle radiation shield.
  • the current leads 5a, 5b in the normally conductive region 15a, 15b each run here with two cylindrical sections 25, 26, the colder section 25 having a significantly larger cross-sectional area B 1 compared to the cross-sectional area B 2 of the warmer section 26.
  • the lower section 25 essentially runs in a cold store 20 which is formed with a gas-tight container 27 and an evaporable substance 28 contained therein.
  • the evaporable substance 28 is in liquid form; some vaporizable substance 28 is already in the container 27 evaporates.
  • the lower end of the container 27 is coupled to the lower cooling stage 10 of the active cooling device 4 via a heat-conducting element 29.
  • the upper section 26 runs essentially in a cold store 20, which is formed with a gas-tight container 30 and an evaporable substance 28 contained therein.
  • the lower end of the container 30 is coupled to the upper cooling stage 9 of the active cooling device 4 via a heat-conducting element 29.
  • the lower container 27 is significantly larger than the upper container 30, and the lower container 27 contains significantly more (based on the heavy mass) vaporizable substance 28 than the upper container 30.
  • the Fig. 3 shows a power supply 5a in the normal conducting area 15a for the invention.
  • the cross-sectional areas B1-B4 decrease from the cold end 18a to the warm end 19a.
  • the different sections 41-44 are coupled to different cold stores 20, here in the form of metallic bodies 20a.
  • the two coupled cold stores 20 of a section 41-44 contact their section 41-44 here approximately in the middle with respect to the vertical longitudinal direction of the power supply 5a by means of a short bridge element 45.
  • the total heavy masses Mi of the cold stores 20 of the four stages of the thermal coupling decrease from the cold end 18a to the warm end 19a.
  • the Bi / Hi ratio decreases from the cold end 18a to the warm end 19a.
  • FIG. 4 A further power supply line 5a is shown in the normally conductive area 15a, which largely corresponds to the design of Fig. 3 corresponds, so that only the main differences are explained.
  • the cold stores 20 are each coupled to the transitions between the sections 41-44 with short bridge elements 45, and in addition a pair of cold stores 20 are coupled to the lower, cold end 18a of the power supply 5a in the normally conductive region 15a via bridge elements 45.
  • the power supply 5a here is made integrally from a single part, e.g. as a metal plate cut to size.
  • the Fig. 5 shows a third embodiment of a magnet arrangement 1 according to the invention, which largely corresponds to the design of Fig. 1 corresponds; only the main differences are explained below.
  • an active auxiliary cooling device 50 is also present here, which is coupled to the outer radiation shield 6 via a heat exchanger 51.
  • the outer radiation shield 6 in turn contacts a part (a section) of the power supply lines 5a, 5b in the normally conductive area 15a, 15b, here between the stages 22, 23 of the thermal coupling.
  • the auxiliary cooling device 50 can reach a lowest working temperature AT aid of approximately -60 ° C.
  • auxiliary cooling device 50 Via the auxiliary cooling device 50, part of the heat load occurring during charging can be derived from the power supply lines 5a, 5b in the normally conductive area 15a, 15b, so that the active cooling device 4 is relieved. It is also possible to support the cooling in normal operation with the auxiliary cooling device 50.
  • Fig. 6 shows a fourth embodiment of a magnet arrangement 1 according to the invention, largely of the design of Fig. 5 corresponds, so that only the essential differences are explained below.
  • the active auxiliary cooling device 50 not only cools the heat exchanger 51 to the outer radiation shield 6, but also a heat exchanger 52, which in turn cools a heat exchanger 53 of a temperature control device 54 for a sample 55 to be examined.
  • the sample 55 to be examined is shown during its measurement by NMR spectroscopy in a not shown
  • the room temperature bore of the cryostat 2 is kept at a constant temperature by the tempering device 54, the magnetic field generated by the magnet coil system 3 of the magnet arrangement 1 during normal operation being used.

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  • Containers, Films, And Cooling For Superconductive Devices (AREA)

Description

Die Erfindung betrifft eine Magnetanordnung, umfassend einen Kryostaten, ein supraleitendes Magnetspulensystem, eine aktive Kühleinrichtung für das Magnetspulensystem und Stromzuführungen zum Laden des Magnetspulensystems im Kryostaten,
wobei die Stromzuführungen zumindest einen normalleitenden Bereich umfassen, insbesondere wobei die Stromzuführungen auch einen HTS-Bereich umfassen,
wobei entlang des normalleitenden Bereichs der Stromzuführungen mehrere Kältespeicher an die Stromzuführungen thermisch gekoppelt sind, um beim Laden des Magnetspulensystems im normalleitenden Bereich entstehende Wärme aufzunehmen.The invention relates to a magnet arrangement comprising a cryostat, a superconducting magnet coil system, an active cooling device for the magnet coil system and power supply lines for charging the magnet coil system in the cryostat,
wherein the power supply lines comprise at least one normally conducting area, in particular wherein the power supply lines also include an HTS area,
wherein a plurality of cold stores are thermally coupled to the power supply lines along the normally conductive area of the power supply lines in order to absorb heat generated in the normally conductive area when the magnetic coil system is charged.

Eine solche Magnetanordnung ist aus der JP H04 23305 A bekannt geworden.Such a magnet arrangement is from the JP H04 23305 A known.

Für Kernspinresonanz(=NMR, nuclear magnetic resonance)-Messungen werden starke Magnetfelder benötigt, die mittels supraleitenden Magnetspulensystemen erzeugt werden können. Die supraleitenden Magnetspulensysteme können verlustfrei große elektrische Ströme tragen, mit denen die starken Magnetfeldstärken erzeugt werden. Allerdings ist für den supraleitenden Zustand eine Kühlung auf kryogene Temperaturen unterhalb der Sprungtemperatur des supraleitenden Materials im Magnetspulensystem nötig. Die supraleitenden Magnetspulensysteme werden daher in einem Kryostaten angeordnet. Um den Heliumverbrauch des Kryostaten zu minimieren, werden teilweise aktive Kühleinrichtungen verwendet, z.B. Pulsrohrkühler, mit denen eine kryogene Temperatur dauerhaft und kostengünstig unterhalten werden kann.Strong magnetic fields are required for nuclear magnetic resonance (NMR) measurements, which can be generated by means of superconducting magnetic coil systems. The superconducting magnetic coil systems can carry large electrical currents without loss, with which the strong magnetic field strengths are generated. However, cooling to cryogenic temperatures below the transition temperature of the superconducting material in the magnet coil system is necessary for the superconducting state. The superconducting magnetic coil systems are therefore arranged in a cryostat. In order to minimize the helium consumption of the cryostat, active cooling devices are used in some cases, e.g. Pulse tube cooler with which a cryogenic temperature can be maintained permanently and inexpensively.

Um ein supraleitendes Magnetspulensystem innerhalb eines Kryostaten mit elektrischem Strom zu laden, verlaufen im Kryostaten von der raumtemperaturwarmen Außenwand des Kryostaten zum Magnetspulensystem Stromzuführungen. Zumindest ein Abschnitt dieser Stromzuführungen ist dabei normalleitend ("normalleitender Bereich"); ein unterer (magnetspulensystemnaher) Abschnitt der Stromzuführungen ist oft auch aus einem Hochtemperatursupraleiter(=HTS)-Material. Während des Ladens fließt durch die Stromzuführungen elektrischer Strom, welcher im normalleitenden Bereich eine ohmsche Wärme erzeugt. Während des Normalbetriebs (auch "steady state" Betrieb genannt) fließt durch die Stromzuführungen typischerweise kein elektrischer Strom ("persistent mode"), jedoch stellen die Stromzuführungen thermische Brücken dar, die Wärme in das Magnetspulensystem einbringen.In order to charge a superconducting magnet coil system within a cryostat with electrical current, current leads in the cryostat run from the outer wall temperature of the cryostat to the magnet coil system. At least a section of these current leads is normally conductive ("normally conductive area"); a lower (near the magnetic coil system) section of the power supply lines is often also made of a high-temperature superconductor (= HTS) material. During charging, electrical current flows through the power supply lines, which generates ohmic heat in the normally conductive area. During normal operation (also called "steady state" operation), typically no electrical current flows through the power supply lines ("persistent mode"), but the power supply lines represent thermal bridges that bring heat into the magnetic coil system.

Typischerweise ist die Wärmelast beim Laden aufgrund mehrerer Effekte (z.B. Betrieb des "Persistent Mode Switches" oder ohmsche Dissipation in den Stromzuführungen) deutlich größer als im Normalbetrieb. Um zu verhindern, dass während des Ladens eine zu hohe, zu einem Quench (Verlust der Supraleitung) führende Temperatur am Magnetspulensystem oder auch im HTS-Bereich der Stromzuführungen entsteht, kann die aktive Kühleinrichtung so groß dimensioniert werden, dass auch die Wärmelast des Ladens mit der Kühleinrichtung kompensiert werden kann. Dies führt aber zu hohen Herstellungskosten und hohen Unterhaltskosten, zu einer großen Baugröße und zu Anforderungen an Kühlung und Stromversorgung, die sich an der beim Laden benötigten Spitzenleistung orientieren müssen. Da das Laden typischerweise nur einige Stunden, der Normalbetrieb aber meist viele Wochen oder Monate dauert, wird die aktive Kühleinrichtung die meiste Zeit nicht ausgelastet.Typically, the thermal load during charging is due to several effects (eg operation of the "persistent mode switch" or ohmic dissipation in the Power supply) significantly larger than in normal operation. In order to prevent a too high temperature leading to a quench (loss of superconductivity) on the magnet coil system or in the HTS area of the power supply lines during charging, the active cooling device can be dimensioned so large that the heat load of the charging also takes into account the cooling device can be compensated. However, this leads to high production costs and high maintenance costs, to a large size and to requirements for cooling and power supply, which must be based on the peak performance required for charging. Since charging typically only takes a few hours, but normal operation usually takes many weeks or months, most of the time the active cooling device is not used to capacity.

Im Falle von mit einem flüssigen Kryogen (etwa flüssigem Helium) gefüllten Kryobehälter des Kryostaten kann beim Laden einfach ein hoher Kühlmittelverbrauch hingenommen werden, was aber hohe Kosten verursacht.In the case of cryogenic containers of the cryostat filled with a liquid cryogen (such as liquid helium), a high consumption of coolant can simply be accepted during charging, but this entails high costs.

Aus der EP 2 624 262 A2 ist es bekannt, bei einem kryogenfreien Kryokühlersystem eine Stromzuführung an die obere Kühlstufe eines zweistufigen Kühlers zu koppeln, und im Bereich dieser oberen Kühlstufe weiterhin ein thermisches Trägheitselement (thermal inertia member) anzukoppeln. Das thermische Trägheitselement kann einen Temperaturanstieg beim Laden oder Entladen einer gekühlten supraleitenden Spule reduzieren.From the EP 2 624 262 A2 it is known to couple a power supply to the upper cooling stage of a two-stage cooler in a cryogen-free cryocooler system, and to further couple a thermal inertia member in the region of this upper cooling stage. The thermal inertia element can reduce an increase in temperature when charging or discharging a cooled superconducting coil.

Aus der JP H04 23305 A sind Stromzuführungen für ein supraleitendes Magnetsystem bekannt geworden, an denen Wärmespeichermaterial angeordnet ist. In einer Ausführungsform sind die Stromzuführungen rohrförmig ausgebildet, und das Wärmespeichermaterial ist in dem Rohr angeordnet, wobei das Wärmespeichermaterial im Inneren des Rohrs durch Schichten eines thermisch isolierenden Materials unterteilt ist. Die Stromzuführungen werden mit einem Heliumgasstrom gekühlt.From the JP H04 23305 A Power supplies for a superconducting magnet system are known, on which heat storage material is arranged. In one embodiment, the power supply lines are tubular and the heat storage material is arranged in the tube, the heat storage material being divided inside the tube by layers of a thermally insulating material. The power supplies are cooled with a stream of helium gas.

Aus der GB 2 506 009 A , der US 5 317 296 , der CN 102 360 694 A und der CN 102 592 773 A sind trennbare Stromzuführungen für einen supraleitenden Magneten bekannt geworden. Durch Trennung der Stromzuführungen nach dem Laden kann im Normalbetrieb ein Wärmeeintrag verhindert werden. Dieser Ansatz ist jedoch technisch schwierig und mit hohen Herstellungskosten verbunden.From the GB 2 506 009 A , of the US 5,317,296 , of the CN 102 360 694 A. and the CN 102 592 773 A. separable power supplies for a superconducting magnet have become known. By disconnecting the power supply after charging, heat input can be prevented in normal operation. However, this approach is technically difficult and involves high manufacturing costs.

In der US 5 302 928 ist eine Stromzuführung für einen supraleitenden Magneten bekannt geworden, die zwischen dem Interface bei Raumtemperatur und der Magnetspule geteilt ist, und an der Stelle der Teilung an eine Wärmesenke angekoppelt ist. Nachteilig ist der Leitungsfortsatz (lead extension), der in den Strompfad eingebracht wird und durch zusätzliche Kontaktwiderstände zu erhöhtem ohmschen Widerstand führt.In the US 5,302,928 A power supply for a superconducting magnet has become known, which is divided between the interface at room temperature and the magnet coil and is coupled to a heat sink at the point of division. A disadvantage is the lead extension, which is introduced into the current path and leads to increased ohmic resistance through additional contact resistances.

In der JP H06 231950 , der GB 2 476 716 A und der DE 10 2007 013 350 A1 sind Stromzuführungen bekanntgeworden, die mit flüssigen Kryogenen gekühlt werden.In the JP H06 231950 , of the GB 2 476 716 A. and the DE 10 2007 013 350 A1 have become known power supplies that are cooled with liquid cryogens.

In der DE 69 324 436 T2 ist ein supraleitendes Magnetsystem bekannt geworden, dessen Stromzuführungen an dem der Spule naheliegenden Ende aus Hochtemperatursupraleitermaterial besteht, und dessen warmes Ende nicht mechanisch befestigt ist.In the DE 69 324 436 T2 A superconducting magnet system has become known, the current leads at the end close to the coil made of high-temperature superconductor material, and the warm end of which is not mechanically fastened.

In der US 5 586 437 wird ein MRI-Kryostat mit einem inneren Wärmeschild und einem äußeren Wärmeschild beschrieben, wobei zur Kühlung des äußeren Wärmeschilds eine eigene Kühleinrichtung vorgesehen ist.In the US 5,586,437 describes an MRI cryostat with an inner heat shield and an outer heat shield, with a separate cooling device being provided for cooling the outer heat shield.

Aufgabe der ErfindungObject of the invention

Der Erfindung liegt die Aufgabe zugrunde, eine Magnetanordnung bereit zu stellen, bei der während des Laden des supraleitenden Magnetspulensystems eine verringerte Kühlleistung benötigt wird, und im Normalbetrieb ein Wärmeeintrag in das supraleitende Magnetspulensystem verringert ist.The invention has for its object to provide a magnet arrangement in which a reduced cooling capacity is required during charging of the superconducting magnet coil system, and a heat input into the superconducting magnet coil system is reduced during normal operation.

Kurze Beschreibung der ErfindungBrief description of the invention

Diese Aufgabe wird auf überraschend einfache und wirkungsvolle Weise gelöst durch eine Magnetanordnung der eingangs genannten Art, die dadurch gekennzeichnet ist, dass die Stromzuführungen im normalleitenden Bereich entlang ihrer Erstreckungsrichtung eine veränderliche Querschnittsfläche B aufweisen,
wobei sich zumindest über einen überwiegenden Anteil der gesamten Länge der Stromzuführungen im normalleitenden Bereich die Querschnittsfläche B von einem kalten Ende zu einem warmen Ende hin verringert.This object is achieved in a surprisingly simple and effective manner by a magnet arrangement of the type mentioned at the outset, which is characterized in that the current leads in the normally conductive region have a variable cross-sectional area B along their direction of extension,
whereby the cross-sectional area B decreases from a cold end to a warm end over at least a predominant part of the total length of the current leads in the normally conductive region.

Im Rahmen der vorliegenden Erfindung wird vorgeschlagen, die Stromzuführungen in ihrem normalleitenden Bereich mit einer besonderen Geometrie zu versehen, um die Stromzuführungen für die Anforderungen beim Laden einerseits und im Normalbetrieb andererseits zu optimieren, wobei entlang des normalleitenden Bereichs der Stromzuführungen mehrere Kältespeicher an die Stromzuführungen thermisch gekoppelt sind.In the context of the present invention, it is proposed to provide the power supply lines in their normally conductive area with a special geometry in order to optimize the power supply lines for charging requirements on the one hand and in normal operation on the other hand, with several cold stores on the power supply lines thermally along the normally conductive area of the power supply lines are coupled.

Beim Laden der supraleitenden Magnetspule ist es wichtig, die ohmsche Wärmeentwicklung vor allem am kalten Ende der Stromzuführungen zu reduzieren. Daher sieht die Erfindung vor, zum kalten Ende hin die Querschnittsfläche (Senkrecht zur Längserstreckung bzw. Stromflussrichtung) zu vergrößern, so dass der ohmsche Widerstand zum kalten Ende hin, soweit er durch die Querschnittsfläche bedingt ist, gesenkt wird. Dadurch wird auch die Wärmeentwicklung nahe dem kalten Ende reduziert.When charging the superconducting magnet coil, it is important to reduce the ohmic heat development, especially at the cold end of the power supply. The invention therefore provides for the cross-sectional area to be increased towards the cold end (perpendicular to the longitudinal extension or current flow direction), so that the ohmic resistance towards the cold end is reduced insofar as it is caused by the cross-sectional area. This also reduces heat generation near the cold end.

Im Normalbetrieb, aber auch beim Laden, ist es wichtig, den Wärmeeintrag in das supraleitende Magnetspulensystem über die Stromzuführungen als Wärmebrücke zur raumtemperaturwarmen Außenwand des Kryostaten zu reduzieren. Der Wärmeeintrag erfolgt vor allem von der warmtemperaturwarmen Außenwand des Kryostaten her. Daher wird erfindungsgemäß die Querschnittsfläche der Stromzuführungen zum raumtemperaturwarmen Ende hin verkleinert, was den Wärmeleitungswiderstand, soweit er durch die Querschnittsfläche bedingt ist, erhöht.In normal operation, but also during charging, it is important to reduce the heat input into the superconducting magnet coil system via the power supply as a thermal bridge to the cryostat's outer wall at room temperature. The heat input occurs primarily from the warm, warm outer wall of the cryostat. Therefore, according to the invention, the cross-sectional area of the power supply lines is reduced towards the end at room temperature, which increases the heat conduction resistance, insofar as it is caused by the cross-sectional area.

Durch die gleichzeitige Verteilung von mehreren Kältespeichern entlang der Stromzuführungen im normalleitenden Bereich wird gewährleistet, dass die durch die Geometrie der Stromzuführungen erreichten lokalen Begrenzungen in der Wärmeentwicklung und dem Wärmeeintrag über längere Zeit genutzt werden können, und insbesondere nicht durch Wärmeleitung entlang der Stromzuführungen schnell ausgeglichen werden können. Die Kältespeicher verlangsamen die Ausgleichsprozesse; durch geeignete Dimensionierung der Kältespeicher (und geeignete Geometrie der Stromzuführungen) kann ohne weiteres die Dauer eines vollständigen Ladevorgangs abgepuffert werden.The simultaneous distribution of several cold stores along the power supply lines in the normally conductive area ensures that the local limitations in the heat development and heat input achieved by the geometry of the power supply lines can be used over a long period of time, and in particular are not quickly compensated for by heat conduction along the power supply lines can. The cold stores slow down the compensation processes; The duration of a complete charging process can be buffered by suitable dimensioning of the cold storage (and suitable geometry of the power supply lines).

Dadurch ist es möglich, das Laden mit einer vergleichsweise kleinen Kühlleistung während der Dauer des Ladevorgangs zu bewältigen, ohne dass das Magnetspulensystem oder ggf. ein supraleitender Abschnitt der Stromzuführungen zu warm wird und quencht. Entsprechend kann eine kostengünstige aktive Kühleinrichtung mit vergleichsweise geringer Kühlleistung eingesetzt werden, die wenig Bauraum benötigt. Im Falle eines kryogenhaltigen Kryostaten kann der Kryogenverbrauch (Kühlmittelverbrauch) beim Laden minimiert werden. Gleichzeitig kann auch der Wärmeeintrag über die Stromzuführungen im Normalbetrieb gering gehalten werden, so dass auch hierfür nur eine geringe Kühlleistung benötigt wird und im Normalbetrieb nur geringe Betriebskosten anfallen.This makes it possible to manage the charging with a comparatively small cooling capacity during the charging process, without the magnetic coil system or possibly a superconducting section of the power supply lines becoming too warm and quenching. Accordingly, an inexpensive active cooling device with a comparatively low cooling capacity, which requires little space, can be used. In the case of a cryogenic cryostat, the cryogen consumption (coolant consumption) during charging can be minimized. At the same time, the heat input via the power supply lines can be kept low in normal operation, so that only a low cooling capacity is required for this and only low operating costs are incurred in normal operation.

Die Stromzuführungen im normalleitenden Bereich laufen typischerweise von einem Anschluss bei Raumtemperatur (warmes Ende) bis zum Magnetspulensystem oder bis zu einem HTS-Bereich (oder HTS-Abschnitt) der Stromzuführungen (kaltes Ende); die Stromzuführung im HTS-Bereich führt dann weiter zum Magnetspulensystem.The power supply lines in the normally conductive area typically run from a connection at room temperature (warm end) to the magnet coil system or up to an HTS area (or HTS section) of the power supply lines (cold end); the power supply in the HTS area then continues to the solenoid system.

Das Magnetspulensystem hat typischerweise einen supraleitenden Kurzschlussschalter zur Einrichtung eines Dauerstrombetriebs (persistent mode). Bevorzugt kann der Kurzschlussschalter mit einem geringen Heizstrom bzw. einer geringen Heizleistung betrieben werden, etwa mit 50 mW oder weniger. Das Magnetspulensystem ist bevorzugt mit Tieftemperatursupraleiter (=LTS)-Materialien (insbesondere NbTi oder bevorzugt Nb3Sn für höhere Betriebstemperaturen) ausgebildet. Vorteilhafter Weise ist der Betriebsstrom des Magnetspulensystems im Normalbetrieb niedrig, etwa 100 A oder weniger, bevorzugt 70 A oder niedriger. Bevorzugt kann das Magnetspulensystem mit hohen Ladespannungen geladen werden, beispielsweise mit 5 V oder mehr.The magnetic coil system typically has a superconducting short-circuit switch for setting up continuous current operation (persistent mode). The short-circuit switch can preferably be operated with a low heating current or a low heating power, for example with 50 mW or less. The magnetic coil system is preferably formed with low-temperature superconductor (= LTS) materials (in particular NbTi or preferably Nb 3 Sn for higher operating temperatures). The operating current of the magnetic coil system is advantageously low in normal operation, approximately 100 A or less, preferably 70 A or lower. The magnet coil system can preferably be charged with high charging voltages, for example with 5 V or more.

Die aktive Kühleinrichtung kann insbesondere ein Pulsrohrkühler oder ein Gifford-McMahon-Kühler sein. Eine bevorzugte Leistungsaufnahme der aktiven Kühleinrichtung liegt bei 2 kW oder weniger, insbesondere 1,5 kW oder weniger. Bevorzugt wird die aktive Kühleinrichtung ohne Kühlwasser bzw. luftgekühlt betrieben.The active cooling device can in particular be a pulse tube cooler or a Gifford-McMahon cooler. A preferred power consumption of the active cooling device is 2 kW or less, in particular 1.5 kW or less. The active cooling device is preferably operated without cooling water or air-cooled.

Die Querschnittsfläche B der Stromzuführungen im normalleitenden Bereich verringert sich typischerweise über die gesamte Länge des normalleitenden Bereichs vom kalten Ende hin zum warmen Ende, zumindest aber über einen überwiegenden Anteil der gesamten Länge der Stromzuführungen im normalleitenden Bereich. Die Querschnittsverringerung kann kontinuierlich oder in Stufen oder in einer gemischten Form erfolgen. Manchmal sind Ausnahmen im Querschnittsflächenverlauf, insbesondere an Verbindungsstellen von Stromzuführungsteilen, nötig und/oder gewünscht. Solche Verbindungsstellen weisen meist eine geringere Querschnittsfläche B ("Lötpunkt"), seltener eine größere Querschnittsfläche ("Lötwulst") auf als die umgebenden Stromzuführungsteile. Diese Ausnahmen machen typischerweise weniger als 5%, meist weniger als 2%, der Gesamtlänge der Stromzuführungen im normalleitenden Bereich aus, und haben entsprechend nur geringen Einfluss auf die gesamte Wärmeentwicklung in den Stromleitungen beim Laden des Magnetspulensystems oder auf den gesamten Wärmeeintrag vom warmen Ende der Stromzuführungen her. Bevorzugt verringert sich die Querschnittsfläche B vom kalten Ende zum warmen Ende hin über einen Anteil von wenigstens 95%, bevorzugt wenigstens 98%, der gesamten Länge der Stromzuführungen im normalleitenden Bereich innerhalb des Kryostaten.The cross-sectional area B of the current leads in the normally conductive region typically decreases over the entire length of the normally conductive region from the cold end to the warm end, but at least over a predominant proportion of the total length of the current leads in the normally conductive region. The reduction in cross-section can take place continuously or in stages or in a mixed form. Sometimes there are exceptions in the cross-sectional area, especially at junctions of Power supply parts, necessary and / or desired. Such connection points usually have a smaller cross-sectional area B ("soldering point"), less frequently a larger cross-sectional area ("soldering bead") than the surrounding power supply parts. These exceptions typically make up less than 5%, usually less than 2%, of the total length of the power supply in the normally conductive area, and accordingly have only a minor influence on the total heat development in the power lines when charging the magnetic coil system or on the total heat input from the warm end of the Power supplies. The cross-sectional area B preferably decreases from the cold end to the warm end over a proportion of at least 95%, preferably at least 98%, of the total length of the current leads in the normally conductive area within the cryostat.

Bevorzugt ist die aktive Kühleinrichtung innerhalb eines Rohres angeordnet, das im Betrieb (insbesondere beim Laden und im Normalbetrieb) mit Gas gefüllt ist; dann ist ein Ausbau oder Tausch der aktiven Kühleinrichtung möglich, ohne das Isolationsvakuum des Kryostaten zu brechen. Beispielsweise kann dieses Rohr für eine der Stromzuführungen vorgesehen sein; diese ist ohnehin vorhanden und somit erhöht sich die Wärmelast im Normalbetrieb nicht weiter. Ebenso kann dieses Rohr das Halsrohr des Kryostaten sein, insbesondere wobei auch eine der Stromzuführungen im Halsrohr verläuft. Eine etwaige überschüssige Kühlleistung, die an einem Regenerator der aktiven Kühleinrichtung zur Verfügung steht, kann durch einen thermischen Kontakt über das Gas im Rohr für die Kühlung der Stromzuführung verwendet werden.The active cooling device is preferably arranged within a tube which is filled with gas during operation (in particular during charging and normal operation); then the active cooling device can be removed or replaced without breaking the insulation vacuum of the cryostat. For example, this tube can be provided for one of the power supplies; this is there anyway and therefore the heat load does not increase further during normal operation. This tube can also be the neck tube of the cryostat, in particular one of the current leads also running in the neck tube. Any excess cooling capacity that is available on a regenerator of the active cooling device can be used for cooling the power supply by thermal contact via the gas in the tube.

Bevorzugte Ausführungsformen der ErfindungPreferred embodiments of the invention

Eine bevorzugte Ausführungsform der erfindungsgemäßen Magnetanordnung sieht vor,
dass die Stromzuführungen im normalleitenden Bereich jeweils N aufeinanderfolgende Teilabschnitte aufweisen, mit N≥2, insbesondere 3≤N≤7, wobei die Teilabschnitte jeweils eine innerhalb eines Teilabschnitts konstante Querschnittsfläche Bi aufweisen,
und dass sich die Querschnittsflächen Bi vom kalten Ende zum warmen Ende hin verringern. Diese Ausführungsform ist baulich einfach zu realisieren; zudem kann das thermische Verhalten während eines Ladevorgangs relativ einfach simuliert und entsprechend die Geometrie der Stromzuführungen gut optimiert werden. Durch eine große Anzahl von Teilabschnitten können Wärmefluss und Wärmeentwicklung bzw. die Temperaturverteilung in den Stromzuleitungen genauer eingestellt werden. Man beachte, dass auch über die Verhältnisse Bi/Hi diese Einstellung weiter optimiert werden kann, mit Hi: Länge des Teilabschnitts i (entlang der Längsrichtung/Stromflussrichtung). Meist gilt auch N≥3 oder N≥4. Typischerweise ist je Teilabschnitt wenigstens ein angekoppelter Kältespeicher vorgesehen. Alternativ ist es auch möglich, die Querschnittsfläche einer Stromzuführung entlang der Erstreckungsrichtung kontinuierlich zu ändern.A preferred embodiment of the magnet arrangement according to the invention provides
that the current leads in the normally conductive region each have N consecutive sections, with N≥2, in particular 3≤N≤7, the sections each having a constant cross-sectional area Bi within a section,
and that the cross-sectional areas Bi decrease from the cold end to the warm end. This embodiment is structurally simple to implement; In addition, the thermal behavior during a charging process can be simulated relatively easily and the geometry of the power supply lines can be optimized accordingly. With a large number of sections, heat flow and heat development or the temperature distribution in the power supply lines can be adjusted more precisely. It should be noted that this setting can also be further optimized via the Bi / Hi ratios, with Hi: length of the section i (along the longitudinal direction / current flow direction). Usually N≥3 or N≥4 also applies. Typically, at least one coupled cold store is provided for each section. Alternatively, it is also possible to continuously change the cross-sectional area of a power supply along the direction of extension.

Bei einer bevorzugten Weiterbildung dieser Ausführungsform sind unterschiedliche Teilabschnitte an unterschiedliche Kältespeicher thermisch gekoppelt. Bei dieser Bauform haben die Kältespeicher nur jeweils eine (direkte) Kopplung zu einem der Teilabschnitte; eine Verbindung zu anderen Teilabschnitten erfolgt nur indirekt über ersteren Teilabschnitt. Dadurch wird die Ausbildung eines starken Temperaturgradienten in den Stromzuleitungen erleichtert. Die Kältespeicher können die Teilbereich beispielsweise jeweils näherungsweise in der Mitte (bezüglich der Erstreckungsrichtung) kontaktieren.In a preferred development of this embodiment, different sections are thermally coupled to different cold stores. With this type of construction, the cold stores only have a (direct) coupling to one of the sections; a connection to other sections is only made indirectly via the former section. This facilitates the formation of a strong temperature gradient in the power supply lines. The cold stores can contact the subareas, for example, approximately in the middle (with respect to the direction of extension).

Bei einer anderen Weiterbildung ist jeweils an einem Übergang von zwei Teilabschnitten wenigstens ein Kältespeicher thermisch angekoppelt, insbesondere wobei auch am kalten Ende der Stromzuführung im normalleitenden Bereich wenigstens ein Kältespeicher thermisch angekoppelt ist. Dies ist meist baulich besonders einfach. Ein oder mehrere Kältespeicher am kalten Ende sorgen für einen besonders guten Schutz des supraleitenden Magnetspulensystems (oder eines HTS-Bereichs der Stromzuleitungen).In another development, at least one cold accumulator is thermally coupled to a transition from two subsections, in particular wherein at least one cold accumulator is also thermally coupled to the cold end of the power supply in the normally conductive area is. This is usually structurally particularly simple. One or more cold stores at the cold end provide particularly good protection for the superconducting magnetic coil system (or an HTS area of the power supply lines).

Bevorzugt ist auch eine Ausführungsform, bei der entlang der Stromzuführungen im normalleitenden Bereich jeweils K Stufen der thermischen Kopplung eingerichtet sind, wobei an jeder Stufe wenigstens ein Kältespeicher an die Stromzuführungen thermisch gekoppelt ist,
mit K≥2, insbesondere 3≤K≤7. Vorteilhaft ist auch K≥3 oder K≥4. Durch eine größere Zahl von Stufen der thermischen Kopplung kann der Wärmefluss bzw. die Temperaturverteilung in den Stromzuführungen genauer eingestellt werden. Zudem werden die Kältespeicher thermodynamisch effizienter eingesetzt. Bevorzugt ist im Falle von N Teilabschnitten jeweils konstanten Querschnitts Bi weiterhin K=N oder K=N+1. Eine Stufe der thermischen Kopplung entspricht einer Kontaktierung einer Stromzuführung durch einen oder mehrere Kältespeicher bei einer bestimmten Längenposition entlang der Stromzuführung; unterschiedliche Stufen der thermischen Kopplung kontaktieren eine Stromzuführung im normalleitenden Bereich also an unterschiedlichen Längenpositionen.An embodiment is also preferred in which K stages of the thermal coupling are set up along the current leads in the normally conductive region, at least one cold store being thermally coupled to the current leads at each stage,
with K≥2, especially 3≤K≤7. K≥3 or K≥4 is also advantageous. The heat flow or the temperature distribution in the power supply lines can be adjusted more precisely by a larger number of stages of the thermal coupling. In addition, the cold stores are used more thermodynamically efficiently. In the case of N partial sections, in each case constant cross-section Bi is preferably K = N or K = N + 1. A stage of the thermal coupling corresponds to contacting a power supply through one or more cold stores at a specific length position along the power supply; Different levels of thermal coupling contact a power supply in the normally conductive area, i.e. at different length positions.

Vorteilhaft ist eine Weiterbildung dieser Ausführungsform, bei der eine schwere Masse Mi von kältespeicherndem Material in dem wenigstens einen Kältespeicher einer jeweiligen Stufe der thermischen Kopplung über die Stufen vom kalten Ende zum warmen Ende hin abnimmt. Die spezifische Wärmekapazität der meisten kältespeichernden Materialien (etwa Metallen) nimmt mit höherer Temperatur (im kryogenen Bereich) stark zu, so dass zum warmen Ende hin keine so großen (absoluten) schweren Massen benötigt werden. Der Begriff der "schweren" (also Gewichtskraft erzeugenden) Masse eines Kältespeichers wird hier verwendet, um eine Verwechslung mit der "thermischen Masse" (also der absoluten Wärmekapazität) zu vermeiden.A further development of this embodiment is advantageous, in which a heavy mass Mi of cold-storing material in the at least one cold store of a respective stage of the thermal coupling decreases over the stages from the cold end to the warm end. The specific heat capacity of most cold-storing materials (such as metals) increases sharply with higher temperatures (in the cryogenic area), so that such large (absolute) heavy masses are not required towards the warm end. The concept of the "heavy" (ie weight-generating) mass of a cold store is used here in order to avoid confusion with the "thermal mass" (ie the absolute heat capacity).

Bevorzugt ist eine Ausführungsform, bei der der Kryostat als kryogenfreier Kryostat ausgebildet ist. In diesem Fall kann eine erhöhte Wärmelast während des Ladens nicht durch Inkaufnahme eines erhöhten Kryogenverbrauchs beim Laden ausgeglichen werden. Die Erfindung ermöglicht in diesem Fall die Nutzung einer aktiven Kühlvorrichtung mit kleiner Kühlleistung, die kostengünstig und kompakt ist. Ein Kryostat wird hier als kryogenfrei angesehen, wenn in keinem zu erwartenden Betriebszustand (also auch nicht beim Laden oder bei einem Quench) Kryogene aus dem System entweichen können. Typischerweise ist das Magnetspulensystem hierbei direkt im Vakuum des Vakuumbehälter angeordnet (und insbesondere nicht in einem Kryogentank mit flüssigem Kryogen, in welches das Magnetspulensystem eintaucht).An embodiment is preferred in which the cryostat is designed as a cryogen-free cryostat. In this case, an increased heat load during charging cannot be compensated for by accepting an increased cryogen consumption during charging. In this case, the invention enables the use of an active cooling device with a low cooling capacity, which is inexpensive and compact. A cryostat is considered to be cryogen-free if cryogens cannot escape from the system in any operating condition to be expected (i.e. not even when loading or during a quench). The magnet coil system is typically arranged directly in the vacuum of the vacuum container (and in particular not in a cryogen tank with liquid cryogen, in which the magnet coil system is immersed).

Bevorzugt ist auch eine Ausführungsform, bei der zumindest ein Teil der Kältespeicher als gasdichte Behälter ausgebildet ist, wobei ein Teil des Volumens der gasdichten Behälter mit einer verdampfbaren Substanz gefüllt ist. Bei dieser Bauform kann Wärmeenergie durch Verdampfen der (bei den im Betrieb vorherrschenden Temperaturen) verdampfbaren Substanz gebunden werden. Die verdampfbare Substanz kann zum Beispiel Stickstoff, Krypton oder Argon, und in einem kälteren Bereich auch Neon oder Helium sein. Man beachte, dass bei dieser Bauform die verdampfbare (meist flüssige) Substanz im Wesentlichen die "schwere Masse" des jeweiligen Kältespeichers bereitstellt. Man beachte weiterhin, dass der Behälter typischerweise aus schlecht wärmeleitfähigem Material besteht, etwa aus Edelstahl oder der Titanlegierung 15-3-3-3. Typischerweise sind entlang der Stromzuführungen mehrere Behälter in Serie geschaltet.An embodiment is also preferred in which at least some of the cold stores are designed as gas-tight containers, with some of the volume of the gas-tight containers being filled with an evaporable substance. With this design, thermal energy can be bound by evaporating the substance which can be evaporated (at the temperatures prevailing during operation). The vaporizable substance can be, for example, nitrogen, krypton or argon, and in a colder area it can also be neon or helium. It should be noted that with this type of construction, the evaporable (mostly liquid) substance essentially provides the "heavy mass" of the respective cold store. It should also be noted that the container is typically made of a poorly heat-conductive material, such as stainless steel or titanium alloy 15-3-3-3. Typically, several containers are connected in series along the power supply lines.

Eine vorteilhafte Weiterbildung dieser Ausführungsform sieht vor, dass die Stromzuführungen im normalleitenden Bereich zumindest teilweise innerhalb der Behälter verlaufen. Dadurch kann ein besonders guter Wärmefluss erfolgen. In den Behältern können Leitbleche und Strahlungsschilde (Baffles) angeordnet werden, um den Wärmefluss zwischen dem warmen und kalten Ende des Behälters durch Konvektion und/oder Wärmestrahlung zu minimieren.An advantageous further development of this embodiment provides that the current leads in the normally conductive area run at least partially within the containers. This enables a particularly good heat flow to take place. Baffles and radiation shields can be placed in the containers. be arranged to minimize the heat flow between the hot and cold ends of the container by convection and / or heat radiation.

Bevorzugt ist weiterhin eine Ausführungsform, bei der zumindest ein Teil der Behälter mit einem unteren Ende über ein Wärmeleitelement an eine Wärmesenke der aktiven Kühleinrichtung thermisch gekoppelt ist, und der Siedepunkt der im Behälter enthaltenen Substanz über der Temperatur der Wärmesenke liegt. Über das Wärmeleitelement kann dem Behälter (nach dem Laden) langsam Wärme entzogen werden, um die verdampfte Substanz wieder zu rekondensieren, typischerweise langsam über mehrere Stunden oder auch mehrere Tage. Insbesondere können zwei Behälter in Serie eingesetzt werden, die an zwei unterschiedliche Kühlstufen der aktiven Kühleinrichtung (etwa eines Pulsrohrkühlers) gekoppelt werden.Also preferred is an embodiment in which at least some of the containers are thermally coupled with a lower end to a heat sink of the active cooling device via a heat-conducting element, and the boiling point of the substance contained in the container is above the temperature of the heat sink. Heat can be slowly removed from the container (after loading) via the heat-conducting element in order to recondense the vaporized substance, typically slowly over several hours or even several days. In particular, two containers can be used in series, which are coupled to two different cooling stages of the active cooling device (such as a pulse tube cooler).

Bevorzugt ist auch eine Ausführungsform, bei der zumindest ein Teil der Kältespeicher als metallische Körper ausgebildet sind. Diese Bauform ist besonders einfach und robust. Ein guter thermischer Kontakt zwischen den (metallischen) Stromzuführungen im normalleitenden Bereich und den metallischen Körpern ist leicht direkt einzurichten.An embodiment is also preferred in which at least some of the cold stores are designed as metallic bodies. This design is particularly simple and robust. Good thermal contact between the (metallic) power supply lines in the normally conductive area and the metallic bodies is easy to set up directly.

Vorteilhaft ist dabei eine Ausführungsform, bei der mehrere als metallische Körper ausgebildete Kältespeicher voneinander beabstandet in einem Vakuumbereich des Kryostaten angeordnet sind. Dies vermeidet auf einfache Weise thermische Kurzschlüsse der Kältespeicher, insbesondere zwischen Kältespeichern verschiedener Stufen der thermischen Kopplung.An embodiment is advantageous in which a plurality of cold stores designed as metallic bodies are arranged spaced apart from one another in a vacuum region of the cryostat. This easily avoids thermal short-circuits of the cold stores, in particular between cold stores of different stages of the thermal coupling.

Besonders bevorzugt ist eine Ausführungsform, bei der weiterhin eine aktive Hilfskühleinrichtung vorhanden ist, die an einen Teil (Teilstück) der Stromzuführungen im normalleitenden Bereich thermisch gekoppelt ist, insbesondere wobei eine tiefste Arbeitstemperatur AThilf der Hilfskühleinrichtung höher ist als eine tiefste Arbeitstemperatur ATmss der aktiven Kühleinrichtung für das Magnetspulensystem. Mit der Hilfskühleinrichtung kann den Stromzuführungen zusätzlich Wärmeenergie entzogen werden, insbesondere beim Laden; dadurch kann die aktive Kühleinrichtung (die vor allem das Magnetspulensystem kühlen soll) entlastet werden. Die Hilfskühleinrichtung hat typischerweise ein AThilf in einem Bereich von -70°C bis -30°C, meist von -60°C bis -50°C, was relativ einfach (insbesondere mit geringer Leistungsaufnahme) zu erreichen ist; hingegen liegt ATmss meist bei 4 K bis 10 K (-269°C bis -263°C). Eine Hilfskühleinrichtung bzw. eine entsprechende Kühlwendel (zugehöriger Wärmetauscher) ist typischerweise im Vakuumbehälter (im Vakuum) angeordnet.An embodiment is particularly preferred in which there is also an active auxiliary cooling device which is thermally coupled to a part (section) of the power supply lines in the normally conductive region, in particular where a lowest working temperature AT helps Auxiliary cooling device is higher than a lowest working temperature AT mss of the active cooling device for the magnet coil system. With the auxiliary cooling device, additional heat energy can be extracted from the power supply lines, particularly when charging; this can relieve the load on the active cooling device (which is primarily intended to cool the magnetic coil system). The auxiliary cooling means typically has a AT Helpful in a range of -70 ° C to -30 ° C, usually from -60 ° C to -50 ° C, which is relatively easy to achieve (especially low-power); however, AT mss is usually 4 K to 10 K (-269 ° C to -263 ° C). An auxiliary cooling device or a corresponding cooling coil (associated heat exchanger) is typically arranged in the vacuum container (in a vacuum).

Eine Weiterbildung dieser Ausführungsform sieht vor, dass die Hilfskühleinrichtung weiterhin an einen Strahlungsschild des Kryostaten und/oder einen Vakuumbehälter des Kryostaten und/oder eine Temperiervorrichtung für eine zu untersuchende Probe thermisch gekoppelt ist. Dadurch wird die aktive Kühleinrichtung zusätzlich entlastet, insbesondere im Normalbetrieb. Wird die Hilfskühleinrichtung genutzt, um den Vakuumbehälter des Kryostaten unter die Umgebungstemperatur abzukühlen, ist es vorteilhaft, den Vakuumbehälter thermisch zu isolieren. Besonders geeignet sind dafür z.B. Kunststoffschäume. Damit kann z.B. Kondenswasserbildung vorgebeugt werden.A further development of this embodiment provides that the auxiliary cooling device is furthermore thermally coupled to a radiation shield of the cryostat and / or a vacuum container of the cryostat and / or a temperature control device for a sample to be examined. As a result, the active cooling device is additionally relieved, in particular in normal operation. If the auxiliary cooling device is used to cool the vacuum container of the cryostat below the ambient temperature, it is advantageous to thermally insulate the vacuum container. For this, e.g. Plastic foams. With this e.g. Condensation can be prevented.

Bevorzugt ist zudem eine Ausführungsform, bei der sich die Querschnittsfläche B vom kalten Ende zum warmen Ende hin um wenigstens einen Faktor 3 verändert. Durch einen Faktor von 3 oder mehr (bezogen auf den überwiegenden Anteil der Stromzuführungen im normalleitenden Bereich) kann bereits eine sehr deutliche Entlastung der aktiven Kühleinrichtung bezüglich der Wärmelast beim Laden erreicht werden.Also preferred is an embodiment in which the cross-sectional area B changes from the cold end to the warm end by at least a factor 3. A factor of 3 or more (based on the majority of the power supplies in the normally conductive area) can already significantly reduce the load on the active cooling device with regard to the heat load during charging.

In den Rahmen der vorliegenden Erfindung fällt auch eine Verwendung einer erfindungsgemäßen Magnetanordnung,
wobei das Magnetspulensystem über die Stromzuführungen geladen wird und ein Ladestrom so gewählt wird und die veränderliche Querschnittsfläche B und/oder die Kältespeicher so eingerichtet sind, dass für eine Wärmelast WLladen, die auf eine kälteste Stufe der Stromzuführungen im normalleitenden Bereich während des Ladens maximal einwirkt, und für eine Wärmelast WLgg auf diese kälteste Stufe in einem Gleichgewichtszustand mit geladenem Magnetspulensystem gilt:
WLladen ≤ 5*WLgg, insbesondere WLladen ≤ 2*WLgg. Die kälteste Stufe (oder Stufe der thermischen Kopplung) entspricht dem Bereich der Stromzuführung, an dem der dem kalten Ende nächste Kältespeicher (oder Kältespeichersatz bei gleicher Längenposition auf den Stromzuführungen) thermisch angekoppelt ist. Die angegebenen Verhältnisse sind im Rahmen der Erfindung gut zu erreichen, und ermöglichen die Nutzung von aktiven Kühleinrichtungen (Kryokühlern) mit geringer Kühlleistung, was kostengünstig ist, einen kompakten Bau der Magnetanordnung ermöglicht und dazu beiträgt, die Integration des Systems in ein Kundenlabor so einfach wie möglich zu gestalten.The use of a magnet arrangement according to the invention also falls within the scope of the present invention,
wherein the magnet coil system is charged via the power supply lines and a charging current is selected and the variable cross-sectional area B and / or the cold storage devices are set up in such a way that they charge for a heat load WL which has a maximum effect on a coldest stage of the power supply lines in the normally conductive area during charging , and for a heat load WL gg to this coldest stage in an equilibrium state with charged solenoid system:
WL load ≤ 5 * WL gg, especially WL load ≤ 2 * WL gg. The coldest level (or level of thermal coupling) is the area of the power supply to which the cold end next cold storage (or cold storage set at the same length position on the power supply lines ) is thermally coupled. The specified ratios are easy to achieve within the scope of the invention and enable the use of active cooling devices (cryocoolers) with low cooling capacity, which is inexpensive, enables a compact construction of the magnet arrangement and contributes to the integration of the system in a customer laboratory as easily as possible possible.

Weitere Vorteile der Erfindung ergeben sich aus der Beschreibung und der Zeichnung. Ebenso können die vorstehend genannten und die noch weiter ausgeführten Merkmale erfindungsgemäß jeweils einzeln für sich oder zu mehreren in beliebigen Kombinationen Verwendung finden. Die gezeigten und beschriebenen Ausführungsformen sind nicht als abschließende Aufzählung zu verstehen, sondern haben vielmehr beispielhaften Charakter für die Schilderung der Erfindung.Further advantages of the invention result from the description and the drawing. Likewise, according to the invention, the features mentioned above and those which have been elaborated further can be used individually or in combination in any combination. The embodiments shown and described are not to be understood as an exhaustive list, but rather have an exemplary character for the description of the invention.

Detaillierte Beschreibung der Erfindung und ZeichnungDetailed description of the invention and drawing

Die Erfindung ist in der Zeichnung dargestellt und wird anhand von Ausführungsbeispielen näher erläutert. Es zeigen:

Fig. 1
eine schematische Darstellung einer ersten Ausführungsform einer erfindungsgemäßen Magnetanordnung, mit metallischen Körpern als Kältespeicher;
Fig. 2
eine schematische Darstellung einer zweiten Ausführungsform einer erfindungsgemäßen Magnetanordnung, mit Behältern gefüllt mit verdampfbarer Substanz als Kältespeicher;
Fig. 3
eine schematische Darstellung einer Stromzuführung im normalleitenden Bereich für die Erfindung, mit Teilabschnitten konstanter Querschnittsfläche, mit mittig kontaktierenden Kältespeichern;
Fig. 4
eine schematische Darstellung einer Stromzuführung im normalleitenden Bereich für die Erfindung, mit Teilabschnitten konstanter Querschnittsfläche, mit Kältespeichern am Übergang von Teilabschnitten;
Fig. 5
eine schematische Darstellung einer dritten Ausführungsform einer erfindungsgemäßen Magnetanordnung, mit Hilfskühleinrichtung zur Kühlung des äußeren Strahlungsschilds;
Fig. 6
eine schematische Darstellung einer vierten Ausführungsform einer erfindungsgemäßen Magnetanordnung, mit Hilfskühleinrichtung zur Kühlung des äußeren Strahlungsschilds und einer Temperiervorrichtung einer zu untersuchenden Probe.
The invention is illustrated in the drawing and is explained in more detail using exemplary embodiments. Show it:
Fig. 1
a schematic representation of a first embodiment of a magnet arrangement according to the invention, with metallic bodies as cold stores;
Fig. 2
a schematic representation of a second embodiment of a magnet arrangement according to the invention, with containers filled with vaporizable substance as a cold store;
Fig. 3
is a schematic representation of a power supply in the normally conductive area for the invention, with sections of constant cross-sectional area, with centrally contacting cold stores;
Fig. 4
a schematic representation of a power supply in the normal conducting area for the invention, with sections of constant cross-sectional area, with cold storage at the transition from sections;
Fig. 5
a schematic representation of a third embodiment of a magnet arrangement according to the invention, with auxiliary cooling device for cooling the outer radiation shield;
Fig. 6
is a schematic representation of a fourth embodiment of a magnet arrangement according to the invention, with Auxiliary cooling device for cooling the outer radiation shield and a temperature control device of a sample to be examined.

Die Fig. 1 zeigt schematisch eine erste Ausführungsform einer erfindungsgemäßen Magnetanordnung 1. Diese umfasst einen Kryostaten 2, ein Magnetspulensystem 3, eine aktive Kühleinrichtung 4 und hier zwei Stromzuführungen 5a, 5b zum Laden des Magnetspulensystems 3.The Fig. 1 shows schematically a first embodiment of a magnet arrangement 1 according to the invention. This comprises a cryostat 2, a magnet coil system 3, an active cooling device 4 and here two current leads 5a, 5b for charging the magnet coil system 3.

Der Kryostat 3 ist hier mit einem Vakuumbehälter 11, einem äußeren Strahlungsschild 6, einem mittleren Strahlungsschild 7 und einem inneren Strahlungsschild 8 ausgebildet. Der Vakuumbehälter 11, der gleichzeitig die Außenwand des Kryostaten 2 bildet, befindet sich auf Raumtemperatur (ca. 20°C). Der äußere Strahlungsschild 6 ist bei ca. 213 K (ca. -60°C). Der mittlere Strahlungsschild 7 koppelt an eine obere Kühlstufe 9 der aktiven Kühlvorrichtung 4 bei ca. 50 K, und der innere Strahlungsschild 8 koppelt an eine untere Kühlstufe 10 der aktiven Kühlvorrichtung bei ca. 3,5 K; letzteres stellt auch die tiefste Arbeitstemperatur ATmss der aktiven Kühleinrichtung 4 dar.The cryostat 3 is designed here with a vacuum container 11, an outer radiation shield 6, a middle radiation shield 7 and an inner radiation shield 8. The vacuum container 11, which simultaneously forms the outer wall of the cryostat 2, is at room temperature (approx. 20 ° C.). The outer radiation shield 6 is at approx. 213 K (approx. -60 ° C). The middle radiation shield 7 couples to an upper cooling stage 9 of the active cooling device 4 at approximately 50 K, and the inner radiation shield 8 couples to a lower cooling stage 10 of the active cooling device at approximately 3.5 K; the latter also represents the lowest working temperature AT mss of the active cooling device 4.

Im Inneren des inneren Strahlungsschilds 8 ist im Vakuum das Magnetspulensystem 3 angeordnet, welches über einen Schalter 12 eines Lade- und Kurzschlussstromkreises 12a supraleitend kurzschließbar ist. Das vom Magnetspulensystem 3 erzeugte Magnetfeld kann im Normalbetrieb beispielsweise für eine NMR-Messung verwendet werden. Der innere Strahlungsschild 8 kann auch gasdicht ausgebildet sein, sodass zur Verbesserung der thermischen Leitfähigkeit beispielsweise etwas gasförmiges Helium vorgesehen werden bzw. enthalten sein kann, das im Rahmen des Betriebs (einschließlich Laden und Normalbetrieb) allerdings nicht eingefüllt werden muss und auch nicht entweichen kann ("kryogenfreier Kryostat").In the interior of the inner radiation shield 8, the magnetic coil system 3 is arranged in a vacuum, which can be superconductively short-circuited via a switch 12 of a charging and short-circuit circuit 12a. The magnetic field generated by the magnetic coil system 3 can be used in normal operation, for example for an NMR measurement. The inner radiation shield 8 can also be gas-tight, so that to improve the thermal conductivity, for example, some gaseous helium can be provided or contained, which, however, does not have to be filled in during operation (including charging and normal operation) and cannot escape ( "cryogen-free cryostat").

Alternativ zum kryogenfreien Kryostat kann der Kryostat 2 auch als kryogenhaltiger Kryostat ausgebildet sein (in Fig. 1 nicht näher dargestellt). In diesem Fall ist anstelle des inneren Strahlungsschilds 8 ein Kryobehälter vorgesehen, welcher typischerweise flüssiges Kryogen (etwa Helium) enthält, in welches das Magnetspulensystem 3 ganz oder teilweise eingetaucht ist. Das Kryogen im Kryobehälter kann beim kryogenhaltigen Kryostaten bei Bedarf im Betrieb nachgefüllt werden, gegebenenfalls auch während des Ladens.As an alternative to the cryogen-free cryostat, the cryostat 2 can also be designed as a cryogen-containing cryostat (in Fig. 1 not shown). In this case, instead of the inner radiation shield 8, a cryogenic container is provided, which typically contains liquid cryogen (such as helium), in which the magnetic coil system 3 is completely or partially immersed. The cryogen in the cryocontainer can be refilled in the cryogen-containing cryostat during operation, if necessary also during loading.

Die Stromzuführungen 5a, 5b führen von Anschlüssen 13a, 13b am Vakuumbehälter 11 durch den Kryostaten 3 bis zu Anschlüssen 14a, 14b am Lade- und Kurzschlussstromkreis 12a. Die Stromzuführungen 5a, 5b umfassen dabei in der gezeigten Ausführungsform jeweils einen normalleitenden Bereich 15a, 15b (zwischen Vakuumbehälter 11 und mittlerem Strahlungsschild 7), einen HTS-Bereich 16a, 16b (zwischen mittlerem Strahlungsschild 7 und innerem Strahlungsschild 8) und einen LTS-Bereich (innerhalb des inneren Strahlungsschilds 8).The current leads 5a, 5b lead from connections 13a, 13b on the vacuum container 11 through the cryostat 3 to connections 14a, 14b on the charging and short-circuit circuit 12a. In the embodiment shown, the power supply lines 5a, 5b each comprise a normally conducting area 15a, 15b (between vacuum container 11 and middle radiation shield 7), an HTS area 16a, 16b (between middle radiation shield 7 and inner radiation shield 8) and an LTS area (inside the inner radiation shield 8).

Die Stromzuführungen 5a, 5b im normalleitenden Bereich 15a, 15b weisen hier jeweils eine sich vom kalten (magnetspulensystemnahen) Ende 18a, 18b zum warmen (Raumtemperatur-anschlussnahen) Ende 19a, 19b hin kontinuierlich verkleinernde Querschnittsfläche B auf, erkennbar an einem sich nach oben hin verkleinernden Durchmesser; beispielshaft ist hier die Querschnittsfläche B etwa in der Mitte (entlang der Längsrichtung) der Stromzuführungen 5a, 5b im normalleitenden Bereich 15a, 15b eingezeichnet. Die Querschnittsfläche B verringert sich im gezeigten Ausführungsbeispiel um einen Faktor von ca. 3 (man beachte, dass der Durchmesser quadratisch in die Querschnittsfläche B eingeht, wobei das Durchmesserverhältnis kalt zu warm hier bei ca. 1,75 liegt). Die Querschnittsverringerung ist hier über die gesamte (vertikale) Länge der Stromzuführungen 5a, 5b im normalleitenden Bereich 15a, 15b eingerichtet.The current supply lines 5a, 5b in the normally conductive area 15a, 15b each have a cross-sectional area B which decreases continuously from the cold (near the magnetic coil system) end 18a, 18b to the warm (near the room temperature connection) end 19a, 19b, as can be seen from an upward direction reducing diameter; As an example, the cross-sectional area B is drawn approximately in the middle (along the longitudinal direction) of the current leads 5a, 5b in the normally conductive region 15a, 15b. The cross-sectional area B is reduced by a factor of approximately 3 in the exemplary embodiment shown (note that the diameter is square in the cross-sectional area B, the cold to warm diameter ratio being approximately 1.75 here). The reduction in cross-section is established here over the entire (vertical) length of the current leads 5a, 5b in the normally conductive region 15a, 15b.

Entlang der Stromzuführungen 5a, 5b im normalleitenden Bereich 15a, 15b sind Kältespeicher 20 an diese angekoppelt. Die Kältespeicher 20 sind hier als metallische Massen 20a ausgebildet. Im gezeigten Beispiel sind dabei jeweils drei Stufen 21, 22, 23 der thermischen Kopplung eingerichtet, wobei an jeder der Stufen 21, 22, 23 jeweils zwei Kältespeicher 20 (links und rechts) bei der gleichen Längenposition (die Längenrichtung verläuft in Fig. 1 vertikal) angekoppelt sind. Die Kältespeicher 20 der kältesten Stufe 21 haben insgesamt eine schwere Masse M1 die größer ist die die gesamte schwere Masse M2 der die Kältespeicher 20 der mittleren Stufe 22, und die gesamte schwere Masse M2 der Kältespeicher 20 der mittleren Stufe 22 ist wiederum größer als die gesamte schwere Masse M3 der Kältespeicher 20 der wärmsten Stufe 23. Die Kältespeicher 20 der unterschiedlichen Stufen 21-23, und hier auch innerhalb der Stufen 21-23, sind im Vakuumbereich 11a des Vakuumbehälters 11 voneinander beabstandet angeordnet, um einen thermischen Kurzschluss zu vermeiden.Cold accumulators 20 are coupled to the supply leads 5a, 5b in the normally conductive area 15a, 15b. The cold stores 20 are designed here as metallic masses 20a. In the example shown, three stages 21, 22, 23 of the thermal coupling are set up, two cold stores 20 (left and right) at each of the stages 21, 22, 23 at the same length position (the length direction runs in Fig. 1 vertically) are coupled. The cold stores 20 of the coldest stage 21 have a total heavy mass M1 which is greater than the total heavy mass M2 which the cold stores 20 of the middle stage 22, and the total heavy mass M2 of the cold stores 20 of the middle stage 22 is again greater than the total Heavy mass M3 of the cold accumulator 20 of the warmest stage 23. The cold accumulator 20 of the different stages 21-23, and here also within the stages 21-23, are spaced apart from one another in the vacuum region 11a of the vacuum container 11 in order to avoid a thermal short circuit.

Am unteren, kalten Ende 18a, 18b sind die Stromzuführungen 5a, 5b an den mittleren Strahlungsschild 7 gekoppelt, so dass eine gewisse Kühlleistung der oberen Kaltstufe 9 der aktiven Kühleinrichtung 4 genutzt werden kann. Zudem kontaktiert hier auch der äußere Strahlungsschild 6 die Stromzuführungen 5a, 5b in normalleitenden Bereich 15a, 15b, hier zwischen den Stufen 22 und 23; alternativ kann auch eine nicht-koppelnde Durchführung am äußeren Strahlungsschild 6 vorgesehen sein.At the lower, cold end 18a, 18b, the power supply lines 5a, 5b are coupled to the central radiation shield 7, so that a certain cooling capacity of the upper cold stage 9 of the active cooling device 4 can be used. In addition, here also the outer radiation shield 6 contacts the current leads 5a, 5b in the normally conductive area 15a, 15b, here between the stages 22 and 23; alternatively, a non-coupling passage can also be provided on the outer radiation shield 6.

Beim Laden (oder Entladen) des Magnetspulensystems 3 über die Stromzuleitungen 5a, 5b entsteht Wärme in den Stromzuführungen 5a, 5b im normalleitenden Bereich 15a, 15b, die die Kältespeicher 20 durch Erwärmen der metallischen Massen 20a zumindest teilweise kompensieren, wodurch ein Wärmeeintrag in den HTS-Bereich 16a, 16b der Stromleitungen 5a, 5b oder gar in das Magnetspulensystem 3 verringert wird. Die sich zum kalten Ende 18a, 18b hin erweiternde Geometrie der Stromzuführungen 5a, 5b im normalleitenden Bereich 15a, 15b verringert dabei die ohmsche Wärmeentwicklung nahe dem kalten Ende 18a, 18b, und verringert einen Wärmeeintrag vom raumtemperaturwarmen warmen Ende 19a, 19b her. Die Wärmelast (Wärmefluss "nach unten") im Bereich der untersten Stufe 21 beim Laden WLladen kann dabei im Vergleich zur Wärmelast im Gleichgewichtszustand im Normalbetrieb WLgg begrenzt werden, so dass gilt WLladen ≤ 2*WLgg. Die verbleibende Wärmelast WLladen kann durch die aktive Kühleinrichtung 4 kompensiert werden, so dass sich das supraleitende Magnetspulensystem 3 und auch nicht der HTS-Bereich 16a, 16b der Stromzuführungen 5a, 5b unzulässig (über die jeweilige Sprungtemperatur) erwärmt.When charging (or discharging) the magnetic coil system 3 via the current leads 5a, 5b, heat is generated in the current leads 5a, 5b in the normally conductive region 15a, 15b, which at least partially compensate for the cold stores 20 by heating the metallic masses 20a, thereby introducing heat into the HTS Region 16a, 16b of the power lines 5a, 5b or even into the magnetic coil system 3 is reduced. The geometry of the power supply lines 5a, 5b in the direction widening towards the cold end 18a, 18b Normally conductive region 15a, 15b reduces the ohmic heat development near the cold end 18a, 18b, and reduces heat input from the warm end of the room temperature 19a, 19b. The heat load (heat flow "downwards") in the area of the lowest stage 21 when loading WL can be limited compared to the heat load in equilibrium in normal operation WL gg , so that WL laden ≤ 2 * WL gg. Load the remaining heat load WL can be compensated for by the active cooling device 4, so that the superconducting magnet coil system 3 and also not the HTS region 16a, 16b of the power supply lines 5a, 5b heat up inadmissibly (above the respective transition temperature).

Die Fig. 2 zeigt eine zweite Ausführungsform einer erfindungsgemäßen Magnetanordnung 1, die weitgehend der Bauform von Fig. 1 entspricht; es werden nachfolgend nur die wesentlichen Unterschiede erläutert.The Fig. 2 shows a second embodiment of a magnet arrangement 1 according to the invention, which largely corresponds to the design of Fig. 1 corresponds; only the main differences are explained below.

Der Kryostat 2 verfügt hier über lediglich einen äußeren Strahlungsschild 6, der an der oberen Kühlstufe 9 der aktiven Kühleinrichtung 4 angekoppelt ist, sowie einen inneren Strahlungsschild 8, der an die untere Kühlstufe 10 angekoppelt ist, nicht jedoch über einen mittleren Strahlungsschild.The cryostat 2 here only has an outer radiation shield 6, which is coupled to the upper cooling stage 9 of the active cooling device 4, and an inner radiation shield 8, which is coupled to the lower cooling stage 10, but not via a middle radiation shield.

Die Stromzuführungen 5a, 5b im normalleitenden Bereich 15a, 15b verlaufen hier jeweils mit zwei zylinderförmigen Teilabschnitten 25, 26, wobei der kältere Teilabschnitt 25 eine deutlich größere Querschnittsfläche B1 im Vergleich zur Querschnittsfläche B2 des wärmeren Teilabschnitt 26 hat.The current leads 5a, 5b in the normally conductive region 15a, 15b each run here with two cylindrical sections 25, 26, the colder section 25 having a significantly larger cross-sectional area B 1 compared to the cross-sectional area B 2 of the warmer section 26.

Der untere Teilabschnitt 25 verläuft im Wesentlichen in einem Kältespeicher 20, der mit einem gasdichten Behälter 27 und einer darin enthaltenen, verdampfbaren Substanz 28 ausgebildet ist. Die verdampfbare Substanz 28 liegt flüssig vor; etwas verdampfbare Substanz 28 ist bereits im Behälter 27 verdampft. Das untere Ende des Behälters 27 ist über ein Wärmeleitelement 29 mit der unteren Kühlstufe 10 der aktiven Kühleinrichtung 4 gekoppelt.The lower section 25 essentially runs in a cold store 20 which is formed with a gas-tight container 27 and an evaporable substance 28 contained therein. The evaporable substance 28 is in liquid form; some vaporizable substance 28 is already in the container 27 evaporates. The lower end of the container 27 is coupled to the lower cooling stage 10 of the active cooling device 4 via a heat-conducting element 29.

Der obere Teilabschnitt 26 verläuft im Wesentlichen in einem Kältespeicher 20, der mit einem gasdichten Behälter 30 und einer darin enthaltenen, verdampfbaren Substanz 28 ausgebildet ist. Das untere Ende des Behälters 30 ist über ein Wärmeleitelement 29 mit der oberen Kühlstufe 9 der aktiven Kühleinrichtung 4 gekoppelt.The upper section 26 runs essentially in a cold store 20, which is formed with a gas-tight container 30 and an evaporable substance 28 contained therein. The lower end of the container 30 is coupled to the upper cooling stage 9 of the active cooling device 4 via a heat-conducting element 29.

Der untere Behälter 27 ist deutlich größer als der obere Behälter 30, und der untere Behälter 27 enthält deutlich mehr (bezogen auf die schwere Masse) verdampfbare Substanz 28 als der obere Behälter 30.The lower container 27 is significantly larger than the upper container 30, and the lower container 27 contains significantly more (based on the heavy mass) vaporizable substance 28 than the upper container 30.

Beim Laden (oder Entladen) des Magnetspulensystems 3 über die Stromzuleitungen 5a, 5b entsteht Wärme in den Behältern 27, 30, die durch Verdampfen von verdampfbarer Substanz 28 (was den Gasdruck in den Behältern 27, 30 erhöht) zumindest teilweise kompensiert, wodurch ein Wärmeeintrag in den HTS-Bereich 16a, 16b der Stromzuführungen 5a, 5b oder gar in das Magnetspulensystem 3 im inneren Strahlungsschild 8 verringert wird. Im Normalbetrieb kann gespeicherte Wärmeenergie über die Wärmeleitelemente 29 an die Kühlstufen 9, 10, die als Wärmesenken wirken, allmählich wieder abgegeben werden, so dass die verdampfte Substanz wieder rekondensieren kann. Bei der Auslegung der Behälter 27, 30 ist zu beachten, dass das Verdampfen und Rekondensieren isochore Prozesse sind, da aus den Behältern 27, 30 im Betrieb keine Substanz entweichen darf. Die Veränderung der latenten Wärme bei steigendem Druck und steigender Temperatur im jeweiligen Behälter 27, 30 muss entsprechend berücksichtigt werden.When charging (or discharging) the magnetic coil system 3 via the current leads 5a, 5b, heat is generated in the containers 27, 30, which is at least partially compensated for by evaporation of evaporable substance 28 (which increases the gas pressure in the containers 27, 30), thereby introducing heat in the HTS area 16a, 16b of the power supply lines 5a, 5b or even in the magnetic coil system 3 in the inner radiation shield 8. In normal operation, stored thermal energy can be gradually released again via the heat-conducting elements 29 to the cooling stages 9, 10, which act as heat sinks, so that the vaporized substance can recondense. When designing the containers 27, 30, it should be noted that the evaporation and recondensation are isochore processes, since no substance is allowed to escape from the containers 27, 30 during operation. The change in latent heat with increasing pressure and increasing temperature in the respective container 27, 30 must be taken into account accordingly.

Die Fig. 3 zeigt eine Stromzuführung 5a im normalleitenden Bereich 15a für die Erfindung. Diese umfasst hier N=4 aufeinanderfolgende Teilabschnitte 41, 42, 43, 44, wobei jeder Teilabschnitt 41-44 eine eigene, einheitliche Querschnittsfläche B1-B4 aufweist. Die Querschnittsflächen B1-B4 nehmen vom kalten Ende 18a zum warmen Ende 19a hin ab.The Fig. 3 shows a power supply 5a in the normal conducting area 15a for the invention. This comprises N = 4 consecutive sections 41, 42, 43, 44, each section 41-44 having its own uniform cross-sectional area B1-B4. The cross-sectional areas B1-B4 decrease from the cold end 18a to the warm end 19a.

Die unterschiedlichen Teilabschnitte 41-44 sind an unterschiedliche Kältespeicher 20, hier in Gestalt von metallischen Körpern 20a, gekoppelt. Die jeweils zwei gekoppelten Kältespeicher 20 eines Teilabschnitts 41-44 kontaktieren ihren Teilabschnitt 41-44 hier jeweils näherungsweise mittig bezogen auf die vertikale Längsrichtung der Stromzuführung 5a mittels eines kurzen Brückenelements 45. Die Anzahl K der Stufen thermischer Kopplung, hier jeweils ausgebildet durch die Kontaktierung von zwei Kältespeichern 20 an einer gemeinsamen Längenposition, beträgt hier ebenfalls 4, so dass hier K=N=4 ist. Die gesamten schweren Massen Mi der Kältespeicher 20 der vier Stufen der thermischen Kopplung nimmt vom kalten Ende 18a zum warmen Ende 19a hin ab.The different sections 41-44 are coupled to different cold stores 20, here in the form of metallic bodies 20a. The two coupled cold stores 20 of a section 41-44 contact their section 41-44 here approximately in the middle with respect to the vertical longitudinal direction of the power supply 5a by means of a short bridge element 45. The number K of the stages of thermal coupling, here each formed by the contacting of two cold stores 20 at a common length position is also 4 here, so that here K = N = 4. The total heavy masses Mi of the cold stores 20 of the four stages of the thermal coupling decrease from the cold end 18a to the warm end 19a.

Man beachte, dass für eine Einstellung eines bestimmten Wärmeflusses oder Temperaturprofils auch das Verhältnis Bi/Hi bei den verschiedenen Teilabschnitten 41-44 variiert werden kann, mit Hi: Länge des Teilabschnitts i, mit i=1 bis 4 für die Teilabschnitte 41-44. Typischerweise nimmt das Verhältnis Bi/Hi vom kalten Ende 18a zum warmen Ende 19a hin ab.It should be noted that the ratio Bi / Hi can also be varied for the various subsections 41-44 for setting a specific heat flow or temperature profile, with Hi: length of subsection i, with i = 1 to 4 for subsections 41-44. Typically, the Bi / Hi ratio decreases from the cold end 18a to the warm end 19a.

In der Fig. 4 ist eine weitere Stromzuführung 5a im normalleitenden Bereich 15a gezeigt, die weitgehend der Bauform von Fig. 3 entspricht, so dass nur die wesentlichen Unterschiede erläutert werden.In the Fig. 4 A further power supply line 5a is shown in the normally conductive area 15a, which largely corresponds to the design of Fig. 3 corresponds, so that only the main differences are explained.

Die Kältespeicher 20 sind hier jeweils an den Übergängen zwischen den Teilabschnitten 41-44 mit kurzen Brückenelementen 45 angekoppelt, und zusätzlich ist ein Paar Kältespeicher 20 am unteren, kalten Ende 18a der Stromzuführung 5a im normalleitenden Bereich 15a über Brückenelemente 45 angekoppelt.The cold stores 20 are each coupled to the transitions between the sections 41-44 with short bridge elements 45, and in addition a pair of cold stores 20 are coupled to the lower, cold end 18a of the power supply 5a in the normally conductive region 15a via bridge elements 45.

Die Stromzuführung 5a ist hier integral aus einem einzigen Teil gefertigt, z.B. als eine in entsprechender Form zurechtgeschnittene Metallplatte.The power supply 5a here is made integrally from a single part, e.g. as a metal plate cut to size.

Die Fig. 5 zeigt eine dritte Ausführungsform einer erfindungsgemäßen Magnetanordnung 1, die weitgehend der Bauform von Fig. 1 entspricht; es werden nachfolgend nur die wesentlichen Unterschiede erläutert.The Fig. 5 shows a third embodiment of a magnet arrangement 1 according to the invention, which largely corresponds to the design of Fig. 1 corresponds; only the main differences are explained below.

Neben der aktiven Kühleinrichtung 4 ist hier auch eine aktive Hilfskühleinrichtung 50 vorhanden, die über einen Wärmetauscher 51 an den äußeren Strahlungsschild 6 gekoppelt ist. Der äußere Strahlungsschild 6 kontaktiert wiederum einen Teil (ein Teilstück) der Stromzuführungen 5a, 5b in normalleitenden Bereich 15a, 15b, hier zwischen den Stufen 22, 23 der thermischen Kopplung. Die Hilfskühleinrichtung 50 kann hier eine tiefste Arbeitstemperatur AThilf von ca. -60°C erreichen.In addition to the active cooling device 4, an active auxiliary cooling device 50 is also present here, which is coupled to the outer radiation shield 6 via a heat exchanger 51. The outer radiation shield 6 in turn contacts a part (a section) of the power supply lines 5a, 5b in the normally conductive area 15a, 15b, here between the stages 22, 23 of the thermal coupling. The auxiliary cooling device 50 can reach a lowest working temperature AT aid of approximately -60 ° C.

Über die Hilfskühleinrichtung 50 kann ein Teil der beim Laden auftretenden Wärmelast aus den Stromzuführungen 5a, 5b im normalleitenden Bereich 15a, 15b abgeleitet werden, so dass die aktive Kühleinrichtung 4 entlastet wird. Es ist auch möglich, die Kühlung im Normalbetrieb mit der Hilfskühleinrichtung 50 zu unterstützen.Via the auxiliary cooling device 50, part of the heat load occurring during charging can be derived from the power supply lines 5a, 5b in the normally conductive area 15a, 15b, so that the active cooling device 4 is relieved. It is also possible to support the cooling in normal operation with the auxiliary cooling device 50.

Die Fig. 6 zeigt eine vierte Ausführungsform einer erfindungsgemäßen Magnetanordnung 1, die weitgehend der Bauform von Fig. 5 entspricht, so dass nachfolgend nur die wesentlichen Unterschiede erläutert werden.The Fig. 6 shows a fourth embodiment of a magnet arrangement 1 according to the invention, largely of the design of Fig. 5 corresponds, so that only the essential differences are explained below.

Die aktive Hilfskühleinrichtung 50 kühlt hier nicht nur den Wärmetauscher 51 zum äußeren Strahlungsschild 6, sondern auch einen Wärmetauscher 52, der seinerseits einen Wärmetauscher 53 einer Temperiervorrichtung 54 für eine zu untersuchende Probe 55 kühlt. Die zu untersuchende Probe 55 wird während ihrer Vermessung durch NMR-Spektroskopie in einer nicht näher dargestellten Raumtemperaturbohrung des Kryostaten 2 durch die Temperiervorrichung 54 auf konstanter Temperatur gehalten, wobei das im Normalbetrieb vom Magnetspulensystem 3 der Magnetanordnung 1 erzeugte Magnetfeld genutzt wird.The active auxiliary cooling device 50 not only cools the heat exchanger 51 to the outer radiation shield 6, but also a heat exchanger 52, which in turn cools a heat exchanger 53 of a temperature control device 54 for a sample 55 to be examined. The sample 55 to be examined is shown during its measurement by NMR spectroscopy in a not shown The room temperature bore of the cryostat 2 is kept at a constant temperature by the tempering device 54, the magnetic field generated by the magnet coil system 3 of the magnet arrangement 1 during normal operation being used.

BezugszeichenlisteReference list

11
MagnetanordnungMagnet arrangement
22nd
KryostatCryostat
33rd
supraleitendes Magnetspulensystemsuperconducting magnetic coil system
44th
aktive Kühleinrichtungactive cooling device
5a, 5b5a, 5b
StromzuführungenPower supply
66
äußerer Strahlungsschildouter radiation shield
77
mittlerer Strahlungsschildmedium radiation shield
88th
innerer Strahlungsschildinner radiation shield
99
obere Kühlstufe (Wärmesenke)upper cooling level (heat sink)
1010th
untere Kühlstufe (Wärmesenke)lower cooling level (heat sink)
1111
VakuumbehälterVacuum container
11a11a
VakuumbereichVacuum range
1212th
supraleitender Schaltersuperconducting switch
12a12a
supraleitender Lade- und Kurzschlussstromkreissuperconducting charging and short circuit
13a, 13b13a, 13b
Anschluss (am Vakuumbehälter)Connection (on the vacuum container)
14a, 14b14a, 14b
Anschluss (am Lade- und Kurzschlussstromkreis)Connection (on the charging and short-circuit circuit)
15a, 15b15a, 15b
normalleitender Bereichnormal conducting area
16a, 16b16a, 16b
HTS-BereichHTS area
17a, 17b17a, 17b
LTS-BereichLTS area
18a, 18b18a, 18b
kaltes Endecold end
19a, 19b19a, 19b
warmes Endewarm end
2020th
KältespeicherCold storage
20a20a
metallischer Körpermetallic body
2121
kälteste Stufe der thermischen Kopplungcoldest stage of thermal coupling
2222
mittlere Stufe der thermischen Kopplungmiddle stage of thermal coupling
2323
wärmste Stufe der thermischen Kopplungwarmest stage of thermal coupling
25,2625.26
TeilabschnittSubsection
2727
Behältercontainer
2828
verdampfbare Substanzvaporizable substance
2929
WärmeleitelementThermal element
3030th
Behältercontainer
41-4441-44
TeilabschnittSubsection
4545
BrückenelementBridge element
5050
aktive Hilfskühleinrichtungactive auxiliary cooling device
51-5351-53
WärmetauscherHeat exchanger
5454
TemperiervorrichtungTemperature control device
5555
Probesample
BB
QuerschnittsflächeCross sectional area
B1-B4B1-B4
Querschnittsfläche (Teilabschnitt)Cross-sectional area (subsection)
H1-H4H1-H4
Länge (Teilabschnitt)Length (section)
M1-M3M1-M3
schwere Massenheavy masses

Claims (16)

  1. A magnet assembly (1), comprising a cryostat (2), a superconducting magnet coil system (3), an active cooling device (4) for the magnet coil system (3), and current leads (5a, 5b) for charging the magnet coil system (3) in the cryostat (2),
    wherein the current leads (5a, 5b) comprise at least one normal-conducting region (15a, 15b), in particular wherein the current leads (5a, 5b) also comprise an HTS region (16a, 16b),
    wherein multiple cold reservoirs (20) are thermally coupled to the current leads (5a, 5b) along the normal-conducting region (15a, 15b) of the current leads (5a, 5b), in order to absorb the heat arising in the normal-conducting region (15a, 15b) during the charging of the magnet coil system (3),
    characterized in that
    the current leads (5a, 5b) have a variable cross-sectional area B in the normal-conducting region (15a, 15b) along the extension direction thereof,
    wherein at least over a predominant fraction of the overall length of the current leads (5a, 5b) in the normal-conducting region (15a, 15b), the cross-sectional area B decreases from a cold end (18a, 18b) toward a warm end (19a, 19b).
  2. The magnet assembly (1) as claimed in claim 1, characterized in that the current leads (5a, 5b) in the normal-conducting region (15a, 15b) each have N successive subsections (25, 26; 41-44), with N≥ 2, in particular 3≤N≤7,
    wherein the subsections (25, 26; 41-44) each have a constant cross-sectional area Bi within a subsection (25, 26; 41-44),
    and the cross-sectional areas Bi decrease from the cold end (18a, 18b) toward the warm end (19a, 19b).
  3. The magnet assembly (1) as claimed in claim 2, characterized in that different subsections (25, 26; 41-44) are thermally coupled to different cold reservoirs (20).
  4. The magnet assembly (1) as claimed in claim 2, characterized in that at least one cold reservoir (20) is thermally coupled on at each transition of two subsections (25, 26; 41-44),
    in particular wherein at least one cold reservoir (20) is also thermally coupled on at the cold end (18a, 18b) of the current lead (5a, 5b) in the normal-conducting region (15a, 15b).
  5. The magnet assembly (1) as claimed in any one of the preceding claims, characterized in that K stages of the thermal coupling (21-23) are configured along each of the current leads (5a, 5b) in the normal-conducting region (15a, 15b), wherein at least one cold reservoir (20) is thermally coupled to the current leads (5a, 5b) at each stage (21-23), with K≥2, in particular 3≤K≤7.
  6. The magnet assembly (1) as claimed in claim 5, characterized in that a heavy mass Mi of cold-storing material in the at least one cold reservoir (20) of a respective stage of the thermal coupling (21-23) decreases over the stages (21-23) from the cold end (18a, 18b) toward the warm end (19a, 19b).
  7. The magnet assembly (1) as claimed in any one of the preceding claims, characterized in that the cryostat (2) is designed as a cryogen-free cryostat (2).
  8. The magnet assembly (1) as claimed in any one of the preceding claims, characterized in that at least a part of the cold reservoirs (20) is formed as gas-tight containers (27, 30), wherein a part of the volume of the gas-tight containers (27, 30) is filled with an evaporable substance (28).
  9. The magnet assembly (1) as claimed in claim 8, characterized in that the current leads (5a, 5b) extend at least partially inside the containers (27, 30) in the normal-conducting region (15a, 15b).
  10. The magnet assembly (1) as claimed in one of the preceding claims 8 and 9, characterized in that at least a part of the containers (27, 30) is thermally coupled with a lower end via a heat conduction element (29) to a heat sink (9, 10) of the active cooling device (4), and the boiling point of the substance (28) contained in the container (27, 30) is greater than the temperature of the heat sink (9, 10).
  11. The magnet assembly (1) as claimed in any one of the preceding claims, characterized in that at least a part of the cold reservoirs (20) are formed as metallic bodies (20a).
  12. The magnet assembly (1) as claimed in claim 11, characterized in that multiple cold reservoirs (20) formed as metallic bodies (20a) are arranged spaced apart from one another in a vacuum region (11a) of the cryostat (2).
  13. The magnet assembly (1) as claimed in any one of the preceding claims, characterized in that furthermore an active auxiliary cooling device (50) is provided, which is thermally coupled to a part of the current leads (5a, 5b) in the normal-conducting region (15a, 15b),
    in particular wherein a lowest working temperature AThilf of the auxiliary cooling device (50) is higher than a lowest working temperature ATmss of the active cooling device (4) for the magnet coil system (3).
  14. The magnet assembly (1) as claimed in claim 13, characterized in that the auxiliary cooling device (50) is furthermore thermally coupled to a radiation shield (6, 7, 8) of the cryostat (2) and/or a vacuum container (11) of the cryostat (2) and/or a temperature control device (54) for a sample (55) to be studied.
  15. The magnet assembly (1) as claimed in any one of the preceding claims, characterized in that the cross-sectional area B changes from the cold end (18a, 18b) toward the warm end (19a, 19b) by at least a factor of 3.
  16. The use of a magnet assembly (1) as claimed in any one of the preceding claims,
    wherein the magnet coil system (3) is charged via the current leads (5a, 5b), and a charging current is selected and the variable cross-sectional area B and/or the cold reservoirs (20) are configured such that for a thermal load WLladen, which acts maximally on a coldest stage (21) of the current leads (5a, 5b) in the normal-conducting region (15a, 15b) during the charging, and for a thermal load WLgg on this coldest stage (21) in an equilibrium state with charged magnet coil system (3), the following applies:
    WLladen ≤ 5*WLgg, in particular WLladen ≤ 2*WLgg.
EP18198875.9A 2017-10-09 2018-10-05 Magnet assembly with cryostat and magnet coil system, with cold storage at the power connections Active EP3467852B1 (en)

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DE102017217930.9A DE102017217930A1 (en) 2017-10-09 2017-10-09 Magnet arrangement with cryostat and magnetic coil system, with cold accumulators on the power supply lines

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EP3467852B1 true EP3467852B1 (en) 2020-04-15

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CN109637772A (en) 2019-04-16
CN109637772B (en) 2020-11-03
EP3467852A1 (en) 2019-04-10
US20190108932A1 (en) 2019-04-11
US10839998B2 (en) 2020-11-17
DE102017217930A1 (en) 2019-04-11

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