Bruker Biospin Ag

Bruker Ag

Daniel M Eckert

Robert Schauwecker

Pierre-Alain Bovier

René Flükiger

Michael Westphal

Frank H Laukien

Daniel Guy Baumann

Andreas Amann

René Fluekiger

Vital Abaecherli

Johannes Boesel

Agnès Glémot

Davide Uglietti

Vital Abächerli

Dietrich Vogel

An apparatus for DNP-NMR measurement on a sample, with a magnet configuration for producing a magnetic field in a first working volume and in, a second working volume with a magnetic field gradient in the direction of an axis (z) which extends through the second working volume, with a device for measuring MR signals, with a DNP excitation device, and with a positioning mechanism for transferring the sample, is characterized in that, near the second working volume, a compensation configuration made of magnetic material is mounted that, in the operating condition of the magnet configuration, produces a magnetic field gradient in the direction of the axis (z) in the second working volume that is between &#x2212;90% and &#x2212;110% of the magnetic field gradient of the same order of the stray field of the magnet configuration.

Apparatus for carrying out DNP-NMR measurements with a compensation configuration and method for designing the compensation configuration

The invention relates to a composite (), comprising a Cu&#x2014;Sn bronze matrix () and filaments () surrounded by the bronze matrix (), wherein the filaments () contain niobium (&#x2550;Nb) or a Nb alloy, characterized in that the filaments () contain between 0.3% and 20% of volume of copper (&#x2550;Cu) substructures (), which are distributed within the Nb or the Nb alloy. The composite can be used to produce a superconducting element with the bronze route which has an improved critical current density.

Superconductive elements containing copper inclusions, and a composite and a method for their production

A superconductive element containing NbSn, in particular a multifilament wire, comprising at least one superconductive filament () which is obtained by a solid state diffusion reaction from a preliminary filament structure (), said preliminary filament structure () containing an elongated hollow pipe () having an inner surface () and an outer surface (), wherein said hollow pipe () consists of Nb or an Nb alloy, in particular NbTa, wherein the outer surface () is in close contact with a surrounding bronze matrix () containing Cu and Sn, and wherein the inner surface () is in close contact with an inner bronze matrix () also containing Cu and Sn, is characterized in that the inner bronze matrix () of the preliminary filament structure () encloses in its central region an elongated core () consisting of a metallic material, said metallic material having at room temperature (=RT) a thermal expansion coefficient &#x3b1;&#x3c;17*10K, preferably &#x3b1;&#x2266;8*10K, said metallic material having at RT a yield strength R&#x3e;300 MPa, said metallic material having at RT an elongation at rupture A&#x3e;20%, and wherein the metallic material of the core () is chemically inert with respect to the material of the inner bronze matrix () up to a reaction temperature T of the solid state diffusion reaction. This element has improved superconductive properties in a large volume fraction of its superconductive filaments, in particular a high critical temperature Tand a high critical magnetic filed strength B, and is mechanically stable enough for commercial applications such as magnet coils.

[object Object]

A method for producing a superconductive element, in particular a multifilament wire, starting from a composite () comprising a bronze matrix containing Cu and Sn, in which at least one elongated structure containing Nb or an Nb alloy, in particular NbTa, is embedded, whereby in a first step the composite is extruded at a temperature between 300&#xb0; C. and 750&#xb0; C., followed by cold or hot working and annealing steps in which the composite is elongated in parallel to the elongated structure and softened by temperature treatment, followed by a stacking step, in which a multitude of elongated composites from the preceding cold or hot working steps are bundled, the steps of extruding, elongating, annealing and stacking being repeated one or more times, followed by a final elongating process, including intermediate annealing processes, in which the composite is elongated to its final length, the superconductive phase being obtained by a heat treatment including a solid state diffusion reaction is characterized in that at least part of the elongating steps and annealing steps are performed by isothermal hot rolling in a temperature region between 450&#xb0; C. and 750&#xb0; C. at or above recrystallization temperature of the bronze matrix.

Method for producing a superconductive element

An NMR apparatus comprising an NMR magnet system disposed in a first cryocontainer () of a cryostat (), and an NMR probe head (), wherein the first cryocontainer () is installed in an evacuated outer jacket and is surrounded by a radiation shield () and/or a further cryocontainer (), wherein a cooling device is provided for cooling the NMR probe head () and a cryocontainer (), which comprises a cold head () with several cold stages (), wherein one cold stage () is connected to a heat-transferring device, and wherein a cooling circuit is provided between the cooling device and the NMR probe head (), is characterized in that the cooling device is disposed in a separate, evacuated housing () which is positioned directly above the cryostat (), wherein the heat-transferring device is inserted directly into suspension tubes () of the cryocontainer () and/or is in contact with the radiation shield (). This effects a simple construction that is efficient for cooling an NMR apparatus.

NMR apparatus with commonly cooled probe head and cryogenic container and method for the operation thereof

A magnet arrangement comprising a superconducting magnet coil system (M) for producing a magnetic field in the direction of a z axis in a working volume (AV) disposed on the z axis about z&equals;0, wherein the superconducting magnet coil system (M) comprises a radially inner partial coil system (C ) and a radially outer partial coil system (C ) which is coaxial thereto, and with a field forming device (P) of magnetic material disposed in a preferably cylindrically symmetrical fashion about the z axis, located radially between the radially inner and the radially outer partial coil system (C C ), and being coaxial with respect to the two partial coil systems (C C ), wherein the radially inner partial coil system (C ) produces a homogeneous field in the working volume (AV) and the radially outer partial coil system (C ) produces an inhomogeneous field in the working volume (AV) is characterized in that the radially outer partial coil system (C ) produces, together with the magnetic field forming device (P), a homogeneous field in the working volume (AV), wherein the magnetic material of the field forming device (P) is largely magnetically saturated with its magnetization pointing substantially in a direction along the z axis. In this fashion, a homogenized radially inner partial coil system (C ) can be supplemented with an inhomogeneous radially outer partial coil system (C ), such that, through the use of a magnetic field forming device (P), the overall resulting magnet arrangement once more produces a homogeneous magnetic field in the working volume of the magnet arrangement.

Magnet arrangement comprising a superconducting magnet coil system and a magnetic field forming device and a dimensioning method

A magnet arrangement comprising a superconducting magnet coil system (C) for generating a magnetic field in the direction of a z axis in a working volume (AV) disposed on the z axis about z&equals;0, wherein the field of the magnet coil system (C) in the working volume (AV) comprises at least one inhomogeneous contribution H &middot;z with n&gE;2 whose contribution to the total field strength on the z axis about z&equals;0 varies with the nth power of z, and wherein a field shaping device (P) of magnetic material is provided, which is substantially cylindrically symmetrical with respect to the z axis, is characterized in that the magnet coil system (C) is provided for use in an apparatus for high-resolution magnetic resonance spectroscopy and the field shaping device (P) has, at least partially, a radial separation from the z axis of less than 80 mm and compensates for at least one of the inhomogeneous field contributions H &middot;z of the magnet coil system (C) by at least 50%, wherein at least one additional coil system (S) is provided which acts as a shim device in the magnet arrangement. This permits realization of a field shaping device from magnetic material of a suitable geometry such that at least part of the notch structures for field homogenization can be omitted in the magnet coil system.

Magnet arrangement comprising a superconducting magnet coil system and a magnetic field shaping device for high-resolution magnetic resonance spectroscopy

An actively shielded, superconducting magnet arrangement for the generation of a magnetic field in the direction of a z axis in a working volume arranged about z&equals;0, having a radially inner and a radially outer coaxial coil system, wherein the two coil systems carry the same current and have dipole moments of the same magnitude, but of opposite directions, wherein parts of the radially outer coil system (C &prime;) are electrically connected in series with the radially inner coil system (C ) and wherein a first superconducting switch (S ) is provided via which during operation a superconducting short circuit of a first current path of the magnet arrangement can be effected, is characterized in that a section (A&prime;) of the radially outer coil system (C &prime;), which can be superconductingly short-circuited during operation via a further superconducting switch (S ) is arranged symmetrically to the plane z&equals;0 and that the further superconducting current path formed by the superconductingly short-circuited section is inductively decoupled from the other parts of the magnet arrangement connected in series. In this way, undesired side effects like an increase of the magnet drift or uncontrolled charging of the section (distortion with time of homogeneity, possible increase of the stray field, charging up to quenching) are avoided with simple means without the necessity of a current limiter.

Active shielded superconducting assembly with compensation of magnetic field disturbances

A superconducting magnet arrangement with at least two current paths, short-circuited via switches in the operational state, which may carry different currents, wherein the magnet arrangement comprises at least one actively shielded superconducting magnet with a radially inner and a radially outer coil system which carry approximately the same current and have dipole moments of approximately the same magnitude, but opposite in direction, such that an outer magnetic field disturbance in a working volume of the magnet arrangement in the long-term behavior is suppressed to a remaining value of less than 20% of the external magnetic field disturbance, is characterized in that sections of the superconducting current paths are disturbance, is characterized in that sections of the superconducting current paths are bridged by ohmic resistors and that said sections and the ohmic resistors are chosen such that the magnetic field disturbance in the working volume is reduced already directly after its occurrence with respect to the field shift remaining after a long time, and that subsequently, the magnetic field disturbance in the working volume approaches the said field shift monotonously with a time constant of &tgr;&gE;2 sec. In this manner, also the short-term behavior of such a magnet system is improved in case an external disturbance occurs and new ways for optimizing the dynamic disturbance behavior are shown which require relatively little technical expense.

Active shielded superconducting assembly with improved compensation of magentic field disturbances

A magnet system for magnetic resonance spectrometers comprising an actively shielded superconducting magnet with a radially inner and a radially outer coil system (M,, M,), wherein the two coil systems carry the same current and have identical opposite dipole moments, and comprising a shim coil system for correcting magnetic field inhomogeneities in the working volume, whose z component varies in proportion to z,, is characterized in that the shim coil system comprises a radially inner shim coil set (S,) which is inductively decoupled from the magnet system and generates a magnetic field in the working volume, whose z component varies like &Dgr;H,&plus;c,&middot;z,with c,&equals;const., and a radially outer shim coil set (S,) which is also inductively decoupled from the magnet system and generates a homogeneous magnetic field &minus;&Dgr;H,in the working volume. This produces a Z,shim system with technically simple means which is, on the one hand, compact and does not waste any unnecessary space in the area of the magnet windings, and on the other hand is not susceptible to disturbances due to fluctuating external magnetic fields.

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Duebendorf, Switzerland

Daniel M Eckert