Readily accessible deep cooled nmr shim assembly

Abstract

The invention provides a magnet arrangement in an NMR apparatus comprising a superconducting magnetic coil system (C) for producing a homogeneous one with a He container (H1) having liquid helium and a He inner tube (H), the magnetic coil system being mechanically rigidly connected to the He container , Wherein a radiation shield with a radiation shield inner tube (S) surrounds the He container at a distance for reducing the evaporation rate of the liquid helium, and wherein a field shaping device (P) made of magnetic material for shimming the homogeneous magnetic field is arranged in the space between the he inner tube and the radiation shield inner tube , Is characterized in that the field-shaping device is fixed in the space between the he inner tube and the radiation shield inner tube in such a way that it is in a rigid mechanical contact with the He container without touching the radiation shield inner tube.The field shaping device can be installed in the cryostats so that it does not move relative to the superconducting coils. The He container does not have to be opened for work on the field-shaping device and a decomposition of the cryostat is avoided.

Description

technical field [0001] The invention relates to a magnet arrangement in an NMR (Nuclear Magnetic Resonance) apparatus having a superconducting magnet coil system for generating a uniform magnetic field along the z-axis direction, wherein the superconducting magnet coil system is arranged in a In the He tank of the He tube, the inner He tube in operation contains liquid helium for cooling the coil and is mechanically rigidly connected to the He tank with the radiation shielding device having the inner radiation shielding tube at a distance enclosing the He tank in order to reduce the evaporation rate of liquid helium, and a field shaping device composed of soft magnetic material is arranged in the space between the inner He tube and the inner radiation shielding tube in order to adjust the uniform magnetic field (i.e. shimming). [0002] Such a device is disclosed in JP 3737636 B2. Background technique [0003] The fields of application of superconducting magnet systems inc...

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Problems solved by technology

[0015] Unfortunately, however, this seemingly ideal solution has major disadvantages which the authors of JP 3737636 B2 have conspicuously neglected: namely, that the nitrogen tank moves when the nitrogen filling height changes, and with the installed field shaping the internal tube of the device naturally moves with it too

However, this movement now causes significant changes in the homogeneity of the magnetic field in the working volume, which is unacceptable in many applications

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