Bruker Biospin Gmbh

Other

Wolfgang Frantz

Patrick Wikus

Robert Schauwecker

Gerhard Roth

Volker Niemann

Gerald Neuberth

Michael Dumm

Michael Wagenknecht

Klaus Schlenga

Pierre-Alain Bovier

Andreas Amann

Steffen Bonn

Rafael Caminada

The invention relates to a superconducting magnet coil system comprising a first electrical mesh (M) and a second electrical mesh (M), which are interconnected in series with one another, wherein the first electrical mesh (M) comprises in a first path an HTS (high temperature superconductor) coil section (A) and, in series therewith, a first main coil section (A) and in a second path a quench protection element (Q), which bridges the series connection of HTS coil section (A) and first main coil section (A). The first main coil section (A) comprises a conductor comprising superconducting filaments in a matrix. The second electrical mesh (M) comprises a neighbouring main coil section (A) comprising a conductor comprising superconducting filaments in a matrix. The neighbouring main coil section (A) is that main coil section of an electrical mesh different from the first electrical mesh which, in a radial direction outwards, lies closest to the first main coil section (A) of the first electrical mesh. The magnet coil system is characterized in that, in the case of a quench, the conductors of the main coil sections (A, A, A) each generate a specific power input (LT/2π)*1/ρ, wherein the specific power input of the conductor of the first main coil section (A) of the first electrical mesh (M) is higher than the specific power input of the conductor of the neighbouring main coil section (A) of the second electrical mesh (M). Consequently, using HTS superconductor material, it is possible to provide a magnet coil system with which particularly high field strengths can be generated and/or which has a small structural size.

Superconducting magnet coil system

A superconducting magnet coil arrangement has a high-temperature superconductor (HTS) coil section () in the form of a solenoid that is wound with an HTS tape conductor, and also has a field-shaping device comprising at least two field-shaping elements (). At least one respective field-shaping element is arranged adjoining each of the two axial ends of the HTS coil section, the field-shaping elements being configured in such a way that they reduce the field angle of the magnetic field generated by the magnet coil arrangement with respect to the axial direction in the region of the HTS coil section by at least 1.5&#xb0;.

Magnet arrangement with field-shaping element for reducing the radial field component in the region of an HTS section

A superconducting magnet coil system with high resistance to quench events includes a first coil portion () with a first superconducting material and a second coil portion () with a second superconducting material. The first superconducting material has a higher critical temperature than the second superconducting material. The first and the second coil portions are bridged by a common quench protection element () and together with the quench protection element form a first loop. The magnet coil system also includes a third coil portion () which is part of a second electrical loop with a second quench protection element ()as well as a heating element () which is supplied with a heating voltage in response to a quench of the third coil portion. Among the series connected coil portions () only the second coil portion is in thermal contact with the first heating element ().

An arrangement for setting the spatial profile of a magnetic field in a working volume of a main field magnet (), in particular a superconducting main field magnet, of a magnetic resonance installation. The main field magnet is arranged in a cryostat () and the spatial profile is set by a passive shim apparatus () with magnetic field forming elements which are arranged within the cryostat during operation and which have cryogenic temperatures. The magnetic resonance installation contains a room temperature tube (), in which the sample volume is situated during operation. The passive shim apparatus is introduced into or removed from the cold region of the cryostat via a vacuum lock (), without needing to ventilate the cold region of the cryostat. This provides a relatively simple, cost effective, and time-efficient method to carry out a stable field homogenization using a passive shim apparatus.

Magnet and cryostat arrangement, and method for passive shimming

A cryostat includes a magnet arrangement for the generation of a magnetic field B0, the magnet arrangement comprising an LTS portion having at least one LTS section made from a conventional low-temperature superconductor and an HTS portion having at least one HTS section made from a high-temperature superconductor. The HTS portion is arranged radially within the LTS portion, and the cryostat is designed to control the temperature of the LTS portion and the HTS portion independently of one another, wherein the HTS portion is electrically isolated from the LTS portion, and is designed to be superconductingly short-circuited. The invention proposes a cryostat with magnet arrangement which enables a high magnetic field strength in a compact space and, at the same time, can be easily constructed.

Cryostat with magnet arrangement which includes an LTS portion and an HTS portion

A superconducting high-field magnet coil system comprising several radially nested main coil sections () which are connected to each other in series in such a fashion that currents of the same direction flow through them during operation, wherein a first main coil section (EHS) is disposed radially further inward than a second main coil section (ZHS) and at least one intermediate main coil section (ZW) is disposed radially between the first and the second main coil section (EHS, ZHS), and with a superconducting switch () via which all main coil sections () can be superconductingly short-circuited in series, is characterized in that the first main coil section (EHS) and the second main coil section (ZHS) are directly successively series-connected and the first main coil section (EHS) and the second main coil section (ZHS) are bridged by a common quench protection element, which does not bridge the at least one intermediate main coil section (ZW). The magnet coil system realizes quench protection for selectively preventing excess currents in magnet coil areas in which the excessive mechanical force load associated with an excess current would damage the superconductor.

Superconducting magnet coil system with quench protection for the prevention of excessive localized currents

A method for testing a new superconducting wire involves charging an actively shielded magnet coil configuration which comprises a first partial region which can be superconductingly short-circuited using an additional switch. A superconductor to be tested under increased current load is used in this first partial region, thereby preventing superconductor in the second partial region from being subjected to this increased current load. Operating currents are determined for both partial regions that have the desired excess current in the first partial region, with the overall field Bonly slightly differing from the standard operating field of the magnet coil configuration. The operating currents are adjusted through initial charging of the overall magnet coil configuration, thereby taking into consideration the inductive coupling between the partial regions and after closing of the additional switch, by continued charging or discharging in the second partial region only. The method permits inexpensive testing of a superconductor in a series-produced NMR magnet under NMR conditions.

Method for testing a superconductor under increased current load in a series-produced and actively shielded superconducting NMR magnet

A superconducting magnet coil system comprising a main field coil which is formed from series-connected sections, wherein the conductors of the radially inner sections contain a first superconducting material and have first electric voltage insulation, the conductors of the radially outer sections comprise a second superconducting material and are provided with second electric voltage insulation, wherein the first superconducting material has a higher critical magnetic field than the second superconducting material, and the first voltage insulation has a smaller dielectric strength than the second voltage insulation, and a shielding coil which is connected in series with the main field coil, radially surrounds the main field coil, and comprises conductors of the second superconducting material having the second electric voltage insulation, wherein the main field coil and the shielding coil are superconductingly short-circuited during operation and are protected through several ohmic resistances and/or diodes in case of a quench, is characterized in that the inner sections are protected by at least one ohmic resistance and the outer sections are protected, together with the shielding coil, by one single ohmic resistance.

Superconducting magnet coil system with quench protection

The invention concerns a method for charging an actively shielded magnet coil arrangement () comprising a first partial region () which can be superconductingly short-circuited using an additional switch (), and a second partial region (), wherein the two partial regions () generate dipole moments of different signs. The magnetic fringe field B* is measured close to the desired operating state of the arrangement () and operating currents are determined for each of the two partial regions () at which the overall magnetic field B is free from an additional dipole moment caused by production tolerances to permit setting of the theoretically optimum fringe field, irrespective of production tolerances. These operating currents are adjusted taking into consideration the inductive coupling between the partial regions () through initially charging the entire magnet coil arrangement () and, after closing the additional switch (), through continuation of the charging process in the second partial region () only. This eliminates deviations, which are caused by production tolerances, from the optimum theoretical fringe field of the arrangement () in a simple and inexpensive manner.

Method for fringe field compensation of an actively shielded superconducting NMR magnet

The invention concerns a method for charging a magnet arrangement () comprising a first partial region () which can be superconductingly short-circuited via an additional switch (), and a second partial region (), wherein the two partial regions () generate, in an investigational volume (), gradients of second order having different signs. A magnetic field dependence B* is measured close to the desired operating state of the magnet arrangement () and operating currents are determined for each of the two partial regions () at which the overall magnetic field B in the volume () under investigation is freed from a magnetic field gradient of second order. These operating currents are set thereby taking into consideration the inductive coupling of the partial regions () through initially charging of the overall magnet arrangement () and, after closing of the additional switch (), through continuation of charging only in the second partial region (). The magnetic field homogeneity of the magnet arrangement () can thereby be improved in a simple and inexpensive manner.

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Karlsruhe, Germany

Wolfgang Frantz