Abstract: An NMR measuring device contains an NMR probe head (10a) having an NMR receiver coil (11), and the probe head can be supplied via a cryogenically insulated transfer conduit (9) with coolant from a cooling device (1a). The cooling device comprises a cryo-cooler (2) having a first cooling stage (4) with a first stage exchanger (12) and a second cooling stage (3) having a second stage exchanger (8). A pump (6) transports coolant in the cooling circuit. The NMR probe head (10a), in addition to the NMR receiver coils (11), has preamplifiers (21) for amplifying the received NMR signals and an additional cryogenically insulated transfer conduit (20) is inserted between the cooling device (1a) and the NMR probe head (10a) by means of which, the preamplifiers (21) and/or the components in contact with the preamplifiers (21) can be supplied with a flow of coolant at a higher temperature than that used for cooling the NMR receiver coils (11).

Abstract: A nuclear magnetic resonance (NMR) probe head for use in a room temperature bore of a superconducting NMR magnet cryostat for investigation of generally room temperature samples comprises a radio frequency (RF) receiving coil, a receiving coil preamplifier connected to the receiving coil, at least one additional coil and cryogenic means connected to the RF receiving coil, to the receiving coil preamplifier, and to the at least one additional coil for keeping the RF receiving coil, the preamplifier and the additional coil at a cryogenic temperature. The apparatus is improved in that at least one additional preamplifier is connected to the additional coil and to the cryogenic means the cryogenic means keeping the additional preamplifier at a cryogenic temperature. The apparatus exhibits improved performance and increased flexibility.

Abstract: A NMR measurement apparatus comprising a cryostat (10) in which a superconducting magnet coil system (9) is disposed in a first tank (8) having cryogenic liquid and surrounded by additional cooling devices such as radiation shields (5, 6), superinsulating foil (7) and, if appropriate, a second tank (3) having cryogenic liquid, is characterized by a pulse tube cooler (11) cryotechnically connected to at least one of the additional cooling devices in a good heat conducting fashion with this cooling device being mechanically attached in the cryostat (10) in such a fashion that vibrational and cryotechnical decoupling is achieved between the cooling device and the first tank (8) having the cryogenic liquid and, in particular, between the cooling device and the superconducting magnet coil system (9).

Abstract: An RF receiver coil configuration for NMR spectrometers has at least two largely mutually orthogonal RF receiver coil systems of which at least one is made from superconducting material and is at least partially cooled to a cryogenic temperature lying far below room temperature, with each RF receiver coil system comprising at least one single coil arranged symmetrically about a sample the RF receiver coil systems having differing radial separations from the sample. The inner RF receiver coil system is made from a material having differing physical characteristics in dependence on the actual operating temperature than the material of the outer RF receiver coil system, with the materials and the geometries of the RF receiver coil systems being chosen to minimize the influence of the susceptibility of the RF receiver coil system on the homogeneity of the magnetic field in the vicinity of the sample.

Abstract: In an apparatus having at least one detection coil (1) for the detection of nuclear magnetic resonance (NMR) from a sensitivity region of the detection coil (1) in the ground, whereby nuclear spins within the sensitivity region are excited by repeated coherent excitation, in each case, to precess in the earth's field and produce a small NMR induction voltage in the detection coil (1) which is introduced to a first amplifier (7), the detection coil (1) consists of at least two oppositely wound partial coils (2, 3) having parallel coil axes which are connected electrically in series and at least one compensation coil (8, 9, 10) is provided for additional compensation of spatially inhomogeneous interfering fields whose induction signal is introduced to a second amplifier (18, 19, 20) having adjustable amplification. In this fashion, in addition to the homogeneous portion, an inhomogeneous portion due to distant disturbances can be eliminated from the measured signal.

Abstract: A method for tuning of the probe head impedance (Z.sub.x) of an NMR receiver coil having a receiver circuit for an NMR signal with which, by means of an RF tuning signal (3), the probe head impedance (Z.sub.x) is tuned via a first reference signal produced with real reference resistance (R.sub.0) at one location M2 within the receiver circuit is characterized in that a reference impedance (Z.sub.0) is matched at an arbitrary location in the path of the RF tuning signal (3) in the receiver circuit (10; 11) in such a fashion that a second reference signal corresponding to the first reference signal at location M2 occurs at location M2 and that subsequently, the probe head impedance (Z.sub.x) is tuned to the second reference signal at location M2. In this fashion, in the path of the NMR signal at the input to the preamplifier, the number of necessary diodes, RF chokes and other components, which can lead to signal losses, is minimized.

Abstract: A mixing device for the mixing of fluid measuring samples in an NMR measuring device, whereby the measuring device includes a rod (10) which is arranged coaxially to the main field magnet coil of the NMR measuring device to be movable in the axial direction and, on one end, exhibits a piston projecting into the measuring sample and, with the assistance of a drive coil (8) arranged at the end facing away from the measuring sample, is moved in the axial direction when current flows through the drive coil (8), wherein a spring element (7) is provided to move the rod (10) into a rest position when no current flows through the drive coil (8), is characterized by the drive coil (8) being arranged, in an axially movable fashion, in the inhomogeneous region of the magnetic field produced by the main field magnet coil coaxial to the main field magnet coil, the drive coil (8), on one axial end, being rigidly connected to the rod (10) and, on the end facing away from the rod (10), being connected, via the spring element

Abstract: It is shown that is is possible to inhibit the transfer of magnetization in a chemically exchanging system with several sites in dynamic equilibrium, so that the forward and the backward reaction rates involving two selected species can be studied without being significantly perturbed by other exchange processes. This can be achieved either by selective inversion of the magnetization of the two chosen sites in the course of the reaction interval, or alternatively by inversion of all other sites in the network of exchanging nuclei that one wishes to "decouple" from the selected pair of interest.

Abstract: A method for exciting transverse magnetization by irradiating a nuclear spin system subjected to a constant magnetic field with a frequency-modulated rf-pulse ("chirp"-pulse) and with a further frequency-modulated rf-pulse (further chirp-pulse) for refocusing the magnetization, is characterized in that the rf-pulse-(P1) and the further rf-pulse (P2) overlap each other in time at least partially. Thus, the duration of the pulses can be reduced.

Abstract: A cryostat (1) in particular for the acceptance of a superconducting magnet coil (2) for NMR or ICR measurements, exhibits a central vessel (3) for fluid helium which by means of holding means (4), preferentially thin-walled suspension tubes, is mechanically connected to, preferentially is suspended from, the inside of a closed outer jacket (5) of the cryostat (1) whereby the holding means (4) are in good thermal contact, via good thermally conducting tube-shaped connecting elements (6) which completely surround the holding means (4), with a shell (7) surrounding a central vessel (3), the shell (7) being held, in particular, at the temperature of liquid nitrogen, and the thermally good conducting tube-shaped connecting elements (6) being configured to be mechanically flexible. In this fashion, the central vessel (3) is mechanically decoupled from the shell (7) which is thermally connected to the holding means (4) of the central vessel (3).

Abstract: In the case of a method for the generation of nuclear magnetic resonance (NMR) signals from a measuring volume with test substance which is exposed to a highly homogeneous stationary magnetic field B.sub.0, by irradiation of a sequence of at least two radio frequency (RF)-pulses into the measuring volume, wherein the at least two RF-pulses excite nuclear spins of the test substance within the measuring volume in a resonant manner within a frequency band which is narrow with respect to their frequency, the phases of the at least two RF-pulses are selected in dependence upon their frequency in such a manner that the phases of the NMR signals generated by each individual of the at least two RF-pulses are randomised in such a manner that the vectorial sum over the signal intensities of the individual signals is zero, whereas the combination of the at least two RF-pulses leads to the development of observable coherent magnetization of the test substance.

Abstract: Frequency-modulated "chirp" pulses for exciting multiple-quantum coherences over large bandwidths can be considered as an alternative to composite pulses to combat the effects of large offsets and tilted effective fields. Refocusing of the phase dispersion of double-quantum coherence can be combined with suitable detection sequences to yield pure absorption two-dimensional double-quantum spectra. The method of symmetrical excitation and detection by time-reversal may be applied to obtain t.sub.1 -modulated longitudinal magnetization, which may then be converted into observable single-quantum coherence by a chirp echo sequence. Similar approaches can be used for many other NMR experiments involving coherence transfer.

Abstract: In a method for compensation of time variant field disturbances in magnetic fields of electromagnets with high field-homogeneity, in particular in sample volumes of superconducting electromagnets for measurements of magnetic resonance, the dispersion signal u.sub.x of the nuclear signal of a reference substance is acquired and taken into consideration for compensation by generation of a current dependent on the dispersion signal in a field correction coil of the electromagnet. The method is characterized in that the absorption signal u.sub.y of the reference substance is additionally acquired and that the compensation is carried out in dependence on the quantity u.sub.x /u.sub.y and/or (1/u.sub.y)(du.sub.x /dt). These are substantially independent of many influencing quantities.

Abstract: A method for generating a spectrum of NMR signals with rectangular characteristic in the frequency space by radiating a sequence of RF pulses onto a sample in the homogeneous magnetic field is presented. The RF pulses of the sequence are amplitude modulated and the enveloping function of the sequence consists of a superposition of bell-curve-shaped RF pulses with optimized positions of the maxima, pulse widths and peak amplitudes. The response signals, in dependence on the standardized frequency, shift, approximate virtually ideally, a rectangular function. The method is applicable with success especially in image generation for NMR tomography, in multidimensional NMR spectroscopy, as well as in volume selective NMR spectroscopy.

Abstract: A method for measuring cross-relation rates in high-resolution nuclear magnetic resonance (NMR) spectroscopy in which in a homogeneous static magnetic field B.sub.0 in a direction of a z-axis which causes alignment of longitudinal components I.sub.Z.sup.A, I.sub.Z.sup.X of magnetization vectors I.sup.A, I.sup.X of nuclei A, X during a time interval .tau..sub.m a sample substance, preferably dissolved in liquid, with nuclei A and X having different chemical shifts .OMEGA..sub.A and .OMEGA..sub.X is irradiated with a radio-frequency (rf) field and afterwards by action of a suitable rf-pulse sequence the longitudinal magnetization is transferred into a transverse magnetization creating a rf-signal received by a detector, is characterized in that the rf field is composed by at least two weak, selective component fields, the frequencies of these fields being chosen such that the magnetization vectors I.sup.A and I.sup.

Abstract: An actuating drive for controllable adjustment of a plurality of actuators in a nuclear resonance spectrometer is characterized in that the actuating drive has a drive train with a drive shaft (9) that can be driven by an electric drive motor (3) and with a plurality of drive train outputs, for coupling to the actuators, each of which can be individually coupled to the drive shaft by means of a changeover device. This enables the actuators to be adjusted automatically.

Abstract: A cryomagnet system, in particular for use with nuclear magnetic resonance (NMR) experiments or ion cyclotron resonance (ICR) experiments, with a low-loss helium cryostat (1) comprising a helium container (2) and one or a plurality of tubes for the feed or exit of helium into or out of the helium container (2), respectively, the tubes being sealed to the atmosphere outside the helium container (2) by at least one non-return low-pressure valve (4), wherein at least one exhaust pipeline (3) is provided with a device for dissipating the energy of the expanding helium. Such a device may consist of a chamber which is deviated from the exhaust pipeline (3) and has a wall material of very high extensibility, e.g. a folding balloon. Yet the device may also consist of a flow baffle which is provided in the exhaust pipeline (3), for example a porous disc (6).

Abstract: In the case of a nuclear magnetic resonance spectrometer containing a sample (1) arranged in a homogeneous magnetic field and being adjusted approximately to room temperature or a higher temperature, and a RF receiver coil (3) which is arranged around the sample (1) and cooled down to far below room temperature, for receiving nuclear magnetic resonance signals from the sample (1), at least certain parts of the RF receiver coil (3) are in thermal contact with a cooled platform (7). The connection lines of the RF receiver coil (3), the outer resonator wall (10), the pre-amplifier and the coolant transfer lines can be cooled by cold return gas. Thanks to this arrangement of the RF receiver coil (3), one achieves an optimum space factor, the thermal noise of the receiver system is drastically reduced, the Q factor of the resonant circuit is increased, and consequently the signal-to-noise ratio is improved.

Abstract: For determining flowing material within a body by NMR tomography, a disk-shaped area in the body is excited, whereafter one applies a flow phase gradient directed in the same sense as the selection gradient (1) and comprising two successive, inversely identical sections (3,4) whose values are varied for the successive excitations. The echo signals obtained, which originate substantially from moving material, are received at a reading gradient directed perpendicularly to the selection gradient. 2DFT reconstruction of a set of spin echo signals furnishes an image which contains the spatial coordinate of the reading gradient in one direction and the flow speed of the material flowing in a direction perpendicular to the excited area in the second direction.

Abstract: The invention concerns a vibration-damping mount (1) for vibration-sensitive equipment and apparatus. The vibration-damping mount (1) has a damping device (10), a supporting structure (20) connected thereto, shock absorption elements (30), and height adapters (40). The vibration-damping mount (1) can be divided, and can be erected without changing the position of the unit being held.