Bruker Biospin Gmbh

Bruker Analytische Messtechnik Gmbh

Bruker Analytik Gmbh

Brucker Analytik Gmbh

Hartmut Schmidt

Michael Westphal

Bertold Knuttel

In a magnetic resonance (MR) apparatus comprising a main field magnet system with a tubular opening for receiving the object to be investigated and at least one tubular mechanically oscillatory component, disposed in this opening, in particular a gradient coil system, and at least one cylindrical element of electrically conducting material surrounded by the main field magnet system, which is rigidly mechanically connected to at least one of the mechanically oscillatory components or forms an integral mechanical component thereof, the sum of the products p of the electric conductivities &sgr;, the cylinder radii R and the wall thicknesses d of the cylindrical element per mechanically oscillatory component is between 1 Am/V and 10,000 Am/V, preferably between 10 Am/V and 1000 Am/V, and particularly preferred between 20 Am/V and 500 Am/V. This produces good noise damping in an inward direction.

Magnetic resonance apparatus with damping of inner mechanical vibrations

A gradient coil system comprises a gradient coil for generating a rapidly changing magnetic gradient field in a working volume of a magnetic resonance apparatus, with a current path guided in windings on the surface of a geometric body, the geometry of which results in the desired spatial dependence of the magnetic field of this gradient coil in the working volume. N current power supplies (NG , NG ) can be controlled with an analog or digital control signal to each generate a time-dependent controlled electric current (i , i ) proportional to the control signal. The current path is divided into several parallel conductor paths which are electrically insulated from one another, and which form a doubly or multiply wound transformer, wherein the inductances of the various conductor paths with respect to one another as well as the mutual inductances with respect to one another have approximately the same value L. The ends of each conductor path are each connected to one respective current power supply (NG ,NG ), and the current power supplies (NG , NG ) can be controlled with control signals in such a manner as to supply the same current (i , i ) to the conductor paths at all times. This enables operation of a gradient coil with several current power supplies in such a manner that, should the dependencies of the currents of the current power supplies not be precisely identical, generation of disturbing magnetic fields having a geometry which differs considerably from the desired geometry for the gradient coil is prevented.

Electric arrangement for operation of a gradient coil with several power supplies

The windings of an NMR magnet coil are formed of at least two adjacent non-crossing conductor paths which are electrically insulated from one another. Each conductor path of a partial coil can be transformed geometrically into one respective conductor path in each partial coil through the symmetrical operations. The various conductor paths in each partial coil are coded in such a manner that the conductor paths adjacent to one another in a winding and attributed with identical successive cardinal numbers as code numbers in their geometric order. The conductor paths in the various partial coils which can be transformed into one another through symmetrical operations have the same code numbers. Each conductor path in a partial coil is electrically connected in series with one conductor path each in at least one other partial coil. These series connections of conductor paths are electrically connected to one another in parallel. The sum of the code numbers of the conductor paths connected in series in the various partial coils is identical in each case with all series connections of conductor paths which are connected in parallel. In this manner it is possible, with an extremely small number of crossings, to avoid the problem of strong current redistributions by eddy currents in the generation of magnetic fields which are rapidly variable with time.

Magnet coil with parallel conductor paths

Magnetic shielding for a superconducting magnet coil, arranged in the inside of a cryostat and having a vertical z-axis for generating a static magnetic field of a homogeneity of <10,in the measuring volume of an NMR spectrometer, wherein the shielding comprises spatial shielding at a distance from the cryostat in the form of a ferromagnetic shielding plate arranged above the cryostat, is characterized in that the shielding plate comprises either areas outside of the z-axis having a final curvature in the downward direction or plane surfaces which are inclined with respect to the horizontal line at an angle 10&deg;<theta<60&deg;, truncated conical or truncated pyramid shaped surfaces. In this manner, the magnetic flux in a room located above the spectrometer is minimized and the expenditure for material and assembly for the shielding elements is considerably reduced.

Ferromagnetic spatial shielding for the superconducting high field magnet of an NMR spectrometer

In an NMR apparatus with a system of gradient coils for the production of a magnetic field gradient within a measurement volume (1) within a field coil, the transverse gradient coils are constructed unsymmetrically with respect to the z=0 plane dividing the measurement volume (1), however largely mirror symmetric to a x=0 or y=0 plane containing the z axis, and possess only two partial coils (20', 20''; 40', 40'') whose windings each exhibit the same winding direction. The axial gradient coils are cylindrically symmetric with respect to the z axis and totally unsymmetric with respect to the z=0 plane, and consist of at least two partial coils which are arranged on differing sides of z=0 plane, whereby the partial coils on one side largely exhibit the opposite winding direction than the coils on the other side, and whereby the number of coils with a particular winding direction is not equal to the number of coils with the opposite winding direction. In each case, it is thereby achieved that the measurement volume (1) is displaced to a, relative to the z axis, axial end of the apparatus so that access to the measurement volume (1) is substantially improved.

Gradient coil system

In a method for the production of a magnet coil arrangement which can create a predetermined magnet field B and has a minimal inductance L. The magnetic field B to be generated is expanded in spherical harmonics with coefficients C.sub.n,m and a field error .DELTA. B=f.sub.1 (C.sub.n,m) is defined fixing the deviation of the magnet field profile of the coil arrangement to be calculated from the given magnet field B within a volume and, if necessary, further parameters P=f.sub.2 (C.sub.n,m) are predefined, whereby the value of P which is calculated with a particular set of coefficients C.sub.n,m is within predetermined limits. By defining limits for technically relevant parameters and their variation as well as by giving the desired minimum inductance, the procedure achieves a high flexibility in conjunction with independent optimization of the parameters, in particular field errors, minimum inductance and current density oscillations.

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Karlsruhe, Germany

Hartmut Schmidt