Bruker Biospin Gmbh

Bruker Switzerland Ag

Other

Bruker Analytik Gmbh

Bruker Biospin Ag

Bruker Biospin Gmbh & Co. Kg

Marco Strobel

Michael Westphal

Gerhard Roth

Patrick Wikus

Joerg Hinderer

Steffen Bonn

Gerald Neuberth

Andreas Kraus

Holger Liebel

Jörg Hinderer

Johannes Bösel

A method is provided for precooling a cryostat having a hollow cold head turret into which a neck tube protrudes and connects an object to be cooled to the exterior of the cryostat, wherein a cold head having a cold head stage for cooling a cryogenic working medium may be introduced into the neck tube. During a condensation operation the cryogenic working medium flows through a heat pipe into an evaporator chamber which is thermally conductively connected to the object to be cooled. During a precooling phase a precisely fitting, thermally conductive short circuit block is inserted through the neck tube into the heat pipe to provide thermal conduction between the object to be cooled and a cooling device. The short circuit block is removed from the heat pipe after the target temperature is reached, and heat is subsequently transmitted through the heat pipe during a condensation operation.

Method and device for precooling a cryostat

A method for autonomously cooling down a cryogen-free superconductive magnetic coil system includes:

Autonomous cooling of a superconductive dry-cooled MR magnetic coil system

A cryostat assembly with an outer container for a storage tank with a first cryogenic fluid and a coil tank for a superconducting magnet coil system. The magnet coil system is cooled by a second cryogenic fluid colder than the first cryogenic fluid, the coil tank being mechanically connected to the outer container and/or to radiation shields surrounding the coil tank via a mounting structure. Liquid helium at an operating temperature of approximately 4.2 K is the first cryogenic, fluid and helium at an operating temperature of &#x3c;3.5 K is the second cryogenic fluid in the coil tank. The mounting structure has mounting elements with thermally conductive contact points thermally coupled to heat sinks having a temperature at or below that of the storage tank, via thermal conductor elements. This ensures long times to quench if malfunctions occur.

Cryostat assembly with superconducting magnet coil system with thermal anchoring of the mounting structure

A magnet assembly () with a cryostat () has a superconducting magnet coil system (), an active cooling device () for the coil system, and current leads () for charging the coil system. The current leads have at least one normal-conducting region (), wherein multiple cold reservoirs () are thermally coupled to the current leads along the normal-conducting region thereof, in order to absorb heat the normal-conducting region during charging of the magnet coil system. The current leads have a variable cross-sectional area B in the normal-conducting region along the extension direction thereof, wherein at least over a predominant fraction of their overall length in the normal-conducting region, the cross-sectional area B decreases from a cold end () toward a warm end (). This provides a magnet assembly requiring reduced cooling power during charging, with less heat introduced into the magnet coil system in normal operation.

Magnet assembly with cryostat and magnet coil system, with cold reservoirs on the current leads

A cryostat has a cooling arm with a first thermal contact surface which can be brought into thermal contact with a second thermal contact surface on an object to be cooled. A hollow volume () between the inner side of the neck tube, the cooling arm, and the object is filled with gas and the cooling arm is pressurized by the inner pressure of the gas and also by atmospheric pressure. A contact device brings the first and the second contact surfaces into thermal contact below a threshold gas pressure and moves them away from each other when the threshold pressure has been exceeded such that a gap () filled with gas thermally separates the first and second contact surfaces. Operationally safe and fully automatic reduction of the thermal load acting on the object to be cooled is thereby obtained in case the cooling machine fails.

Automatic thermal decoupling of a cold head

A method is provided for precooling a cryostat having a hollow cold head turret into which a neck tube protrudes and connects an object to be cooled to the exterior of the cryostat, wherein a cold head having a cold head stage for cooling a cryogenic working medium may be introduced into the neck tube. During a condensation operation the cryogenic working medium flows through a heat pipe into an evaporator chamber which is thermally conductively connected to the object to be cooled. During a precooling phase a precisely fitting, thermally conductive short circuit block is inserted through the neck tube into the heat pipe to provide thermal conduction between the object to be cooled and a cooling device The short circuit block is removed from the heat pipe after the target temperature is reached, and heat is subsequently transmitted through the heat pipe during a condensation operation.

A nuclear magnetic resonance (NMR) apparatus () comprises a superconducting main field magnet coil system () which generates a homogeneous magnetic field of at least 3T, and a gradient coil system () which generates a gradient strength of at least 10 mTm, with a slew rate of at least 100 Tms, wherein the main field magnet coil system () is arranged in a cryostat () with liquid helium and a refrigerator () in the form of a pulse tube cooler or a Gifford-McMahon cooler, and wherein an evaporation line () is provided for helium that might evaporate from the cryostat. In all states of operation of the NMR apparatus () without gradient switching, the refrigerator provides a cooling capacity which is at least 0.3 W above the overall power loss of the cryostat, the evaporation line terminates in a buffer container (') disposed outside of the cryostat for collecting the evaporating helium, and a return line () is provided for returning the evaporated helium that has been collected in the buffer container into the cryostat. For this reason, a considerable amount of evaporating helium is saved, thereby considerably extending the refill cycles of liquid helium, which greatly disturb and obstruct normal work cycles and are disadvantageous for operation, in particular, in hospitals.

High field NMR apparatus with excess cooling power and integrated helium re-liquification

A method for cooling a cryostat configuration (') during transport, wherein the cryostat configuration () comprises a superconducting magnet coil () in a helium tank () containing liquid helium (), which is surrounded by at least one radiation shield (), wherein the cooling inside the cryostat configuration (&#x2032;) in stationary operation is performed entirely without liquid nitrogen by means of a refrigerator, characterized in that during transport, the refrigerator is switched off and instead, liquid nitrogen () is conducted from an external nitrogen vessel () via a supply tube () from the nitrogen vessel () to the cryostat configuration (&#x2032;) and brought into thermal contact with the radiation shield () by means of a thermal contact element () in the cryostat configuration (&#x2032;). In this way, the consumption of liquid helium during transport can be greatly reduced and the possible transport time of a charged superconducting magnet configuration increased.

Method for cooling a cryostat configuration during transport and cryostat configuration with transport cooler unit

An NMR spectrometer comprising a magnet coil system disposed in the helium tank () of a cryostat and an NMR probe head () which is disposed in a room temperature bore of the cryostat and contains a cooled RF resonator () for receiving NMR signals from a sample to be examined, wherein the helium tank () and the NMR probe head () are cooled by a common, multi-stage, compressor-operated refrigerator, is characterized in that the common refrigerator comprises a cold head () and several heat exchangers () at different temperature levels, wherein the refrigerator is disposed at a spatial separation from the cryostat in a separate, evacuated and thermally insulated housing (), and several cooling circuits () having thermally insulated transfer lines () are provided between the housing () containing the heat exchangers () and the cryostat, and also between the housing () and the NMR probe head (). The probe head and magnet cryostat of the inventive NMR spectrometer can thereby be cooled by a common refrigerator, wherein the cooling resources of the used refrigerator are optimally utilized.

NMR spectrometer with a common refrigerator for cooling an NMR probe head and cryostat

An NMR apparatus comprising a superconducting magnet coil system, in particular, an NMR spectrometer, with a cryostat which comprises an outer shell and a helium tank which contains the magnet coil system, and with an NMR probe head which is disposed in a room temperature bore of the cryostat and which contains a cooled RF resonator for receiving NMR signals from a sample to be examined and is cooled, together with the NMR probe head, by a cold head of a common, multi-stage, compressor-operated refrigerator, is characterized in that the cold head of the refrigerator is disposed in a neck tube, the upper end of which is connected to the outer shell of the cryostat and the lower end of which is connected to the helium tank in such a manner that the neck tube and the helium tank delimit a helium space, with at least one cooling circuit with thermally insulated transfer lines being provided between the helium space and the NMR probe head, wherein the cryogenic helium in the helium space is used as coolant for the cooling circuit. This produces an NMR apparatus which cools a plurality of elements at different temperature levels using only one single cryocooler to optimally utilize the cooling resources of the refrigerator.

NMR spectrometer with common refrigerator for cooling an NMR probe head and cryostat

A cryostat configuration for keeping liquid helium, comprising an outer jacket ( ) accommodating a helium container ( ), a neck pipe ( ) which is filled with gaseous helium during operation, and a refrigerator ( ), wherein the outer jacket ( ), the helium container ( ) and the neck pipe ( ) delimit an evacuated chamber ( ) which surrounds the helium container ( ); and wherein the refrigerator ( ) has a cooling finger ( ) which has a condensation body ( ) in the region of the lower end of the neck pipe ( ), is characterized in that the condensation body ( ) is partially surrounded by a condensation chamber ( ) which has a first lower opening ( ) to permit draining of liquid helium, and a second opening which communicates with a lower end of a gas supply pipe ( ), wherein the upper end of the gas supply pipe ( ) terminates in the region of the upper end of the neck pipe ( ). This improves the thermal properties of the cryostat configuration. In particular, the convection flow inside the neck pipe ( ) is controlled.

Cryostat configuration with improved properties

A cryostat arrangement for keeping liquid helium comprising an outer shell ( ), a helium container ( ) installed therein and a neck pipe ( ) extending from the helium container to the outer shell whose upper warm end is connected to the outer shell and whose lower cold end is connected to the helium container, wherein the outer shell, the helium container and the neck pipe define an evacuated space ( ) containing a radiation shield ( ) surrounding the helium container and being connected at a coupling to the neck pipe in a heat-conducting fashion, wherein a refrigerator is installed in the neck pipe having a cold finger ( ) which consists of at least one pipe and projects into the neck pipe, is characterized in that at least one pipe of the cold finger is surrounded by at least one separating body ( ) which divides the neck pipe into two partial volumes ( and ) which are connected to one another through a lower opening ( ) and an upper opening ( ). A cryostat arrangement of this type with active cooling through refrigerators shows considerable improvements over conventional cryostats with respect to thermal properties. In particular, it is possible to completely stop consumption of liquid helium.

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Karlsruhe, Germany

Marco Strobel