Abstract: A device for centering an elongated sample tube (8), filled with a measuring substance, relative to the vertical axis of an NMR receiver coil system (9) which is rigidly mounted in a support device, is characterized in that at least two centering devices (13,14) are provided which are separated from each other in an axial direction of the receiver coil axis and act on the sample tube in a radial direction only, one of which is disposed above and the other below the NMR receiver coil system, and at least one positioning devices (16;17) which acts on the sample tube in an exclusively axial direction and which can be located either below or above the NMR receiver coil system, wherein the exclusively radially acting centering devices are rigidly connected to the support device for mounting the NMR receiver coil system.

Abstract: An NMR (=nuclear magnetic resonance) probe head comprising an RF (=radio frequency) receiver coil system, which can be cooled down to cryogenic temperatures, and a room temperature pipe (5), extending in a z direction, for receiving a sample tube (6) containing sample substance to be examined by NMR measurements is characterized by a centering device (10) for centering the sample tube (6) in its measuring position about the axis of the room temperature pipe (5) to thereby provide simple and substantial reduction in the temperature gradient in the z direction during operation without thereby impairing the NMR measurement.

Abstract: A device for centering an elongated sample tube (8), filled with a measuring substance, relative to the vertical axis of an NMR receiver coil system (9) which is rigidly mounted in a support device, is characterized in that at least two centering means (13,14) are provided which are separated from each other in an axial direction of the receiver coil axis and act on the sample tube in a radial direction only, one of which is disposed above and the other below the NMR receiver coil system, and at least one positioning means (16;17) which acts on the sample tube in an exclusively axial direction and which can be located either below or above the NMR receiver coil system, wherein the exclusively radially acting centering means are rigidly connected to the support device for mounting the NMR receiver coil system.

Abstract: An NMR (=nuclear magnetic resonance) probe head comprising an RF (=radio frequency) receiver coil system, which can be cooled down to cryogenic temperatures, and a room temperature pipe (4), extending in a z direction, for receiving a sample tube (6) containing sample substance (7) to be examined by NMR measurements is characterized in that at least one, preferably several radiation shields (9) extending in the z direction and surrounding the room temperature pipe (4) in a radial direction are disposed between the RF receiver coil system (1) and the room temperature pipe (4) which are formed of one or several materials oriented in the z direction and are almost completely transparent to RF fields, at least have an absorption of <5%, preferably <1% for RF fields to thereby provide simple and substantial reduction in the temperature gradient in the z direction during operation without thereby impairing the NMR measurement.

Abstract: An NMR (=nuclear magnetic resonance) probe head comprising an RF (=radio frequency) receiver coil system, which can be cooled down to cryogenic temperatures, and a room temperature pipe (5), extending in a z direction, for receiving a sample tube containing sample substance to be examined by NMR measurements is characterized in that a temperature control (11) is disposed between the RF receiver coil system and the sample tube which surrounds the sample tube in a radial direction and extends in the z direction and is almost completely transparent to RF fields, or at least has an absorption of <5%, preferably <1% for RF fields to thereby provide simple and substantial reduction in the temperature gradient in the z direction during operation without thereby impairing the NMR measurement.

Abstract: A method of operating a high-resolution NMR spectrometer comprising a DDS generator containing an NCOL for generating an LO frequency, wherein the frequency of the NCOL is defined by inputting a numerical value Z, is characterized in that this numerical value Z may assume only values which satisfy the equation Z=n·N/m, wherein Z, n, N, and m are integer and positive numbers, N is a power of 2 with a positive integer exponent, wherein said exponent represents the maximum number of bits during the calculation process, m is approximately 2·fs/&Dgr;B, n approximately m·fout/fs and m additionally a common integer divisor of n·N and fs is the clock frequency of the NCOL, &Dgr;B is the desired bandwidth with high spectral purity and fout is the output frequency of the NCOL.