Abstract: The use of 270.degree. Gaussian pulses instead of the selective 90.degree. pulses usual heretofore makes it possible, for many NMR experiments, to achieve a frequency-selective excitation of samples which is largely free from phase errors and which, consequently, does away in many cases with the need for rephasing measures which heretofore were necessary as a rule.

Abstract: In a temperature-control device for samples, in particular for NMR spectroscopy, comprising a vessel (20) provided with an opening (19) for receiving a measuring sample (1), an inlet opening (10) for introduction of the fluid, an outlet opening (15) for the outflow of the fluid and a flow channel (18) through which at least a partial flow of the fluid is guided past the sample (1), as direct fluid flow, from the bottom to the top, there is provided at least one by-pass channel (17) which is arranged in such a way that an additional partial fluid flow can be guided past the upper area of the said sample (1) in the form of a by-pass fluid flow (7). This enables also the upper area of the sample (1) to be temperature-controlled in an efficient way so as to minimize the temperature gradient in the sample (1).

Abstract: The present invention relates to a method and a device for compensating undesirable side bands in nuclear magnetic resonance spectrometers. The frequency (.omega..sub.m) and the phase of rotation of the sample (10) are detected by means of a light sensor (12) and supplied to a compensation generator (18). The latter generates modulation signals (44 and 43) for modulating the amplitude and the phase of the detected nuclear magnetic signal of the sample, using an amplitude modulator (13) and a phase modulator (14), the modulation frequency being equal to an integral multiple, including the simple value, of the frequency of rotation (.omega..sub.m) of the sample. The additional frequency components heterodyne with the side bands provoked by the rotation of the sample (10) in the static magnetic field (B.sub.O), whereby the said side bands are eliminated.

Abstract: In a method and a device for precooling the helium tank of a cryostat, in particular one for accommodating a superconductive magnet coil, contamination of the helium tank is avoided by the fact that helium gas is cooled down to the temperature of boiling nitrogen in a closed circuit, the helium gas is then circulated through the helium tank and thereafter cooled down again to the temperature of boiling nitrogen. The helium tank is cooled by means of the helium gas, which has a temperature of 77 K, until the tank has reached that temperature. The interior of the helium tank getting into contact exclusively with helium, the helium tank can be filled with liquid helium immediately after it has reached the precooling temperature, without the need to clean the tank first.

Abstract: Method for reducing the content of spurious signals in the output signal of a mixer and mixer designed for carrying out the method according to the invention. When using quadrature mixtures as generators for tunable rf signals it has been found to be a disadvantage that differences in the two channels of the quadrature mixers lead to a high content of undesirable mixture signals. The content of disturbing mixture signals in the output signals of such mixers is reduced according to the invention by feeding the ring modulators of the quadrature mixer with signals differing from pure sine oscillations, which are phase-shifted relative to each other by 90.degree. and which have been determined in such a manner that all pairs of d.c. signals supplied to the two ring modulators result in output signals which have all the same amplitude and each of which has a phase position conforming exactly to the phase position to which the respective pair of d.c. signals is assigned.

Abstract: A cryostat, in particular for superconductive magnets, comprising different components nested in each other, one of them forming an outer shell and at least another one forming a tank arranged in the latter for receiving a coolant, and comprising further tension bars for interconnecting each inner component with its respective adjacent outer component, the said tension bars containing reinforcing fibers and being equipped at their ends with tie rods by means of which they are fixed to the respective component. A bond of high strength is achieved between the tension bars and tie rods due to the fact that the tie rods are provided with an outwardly widening bore, that each end of each tension bar is arranged in the bore in such a manner that the ends of the reinforcing fibers, being spread apart and impregnated with a glue, are located at the wider end of the bore.

Abstract: In NMR pulse experiments transverse magnetization is excited by irradiating the nuclear spin system with a two pulse sequence of a first RF chirp pulse and a second RF chirp pulse, generated after a defocusing time interval .tau.. The pulse duration of the second chirp pulse is half the duration of the first pulse, and the amplitude of the second chirp pulse is approximately three times the amplitude of the first chirp pulse. The first pulse being a 90.degree.-pulse, the second pulse being a 180.degree.-pulse, a refocusing of the magnetization vectors occurs at a time .tau.'=.tau.+.tau.180.degree. after elapse of the second chirp pulse, and acquisition of the resulting echo signal is started at peak of the echo.

Abstract: A method and drive for generating spin echo signals by a sequence of equidistant rf pulses of different amplitude and small flip angle .alpha., which pulses follow each other in very rapid succession. By proper selection of the amplitude, it is ensured that the sequence of equidistant echo signals so obtained has of an image without numerous gradient switching steps heretofore required.

Abstract: The invention relates to a cryostat, in particular a helium cryostat with an additional nitrogen tank and a vacuum section, comprising a pressure-relief cover arranged at the outside of the tank wall of the cryostat for closing an opening therein.

Abstract: In a method for the simultaneous measurement of spin resonance signals, in particular NMR signals, from layers located at different depths in a test volume, simultaneous excitation of the different layers is effected by a multiple-component rf excitation pulse P.sub.n, consisting of n individual components P.sub.m with the frequencies .omega..sub.m, which act selectively on defined layers m of the test volume, in the presence of a layer-selective gradient, the individual components P.sub.m having a phase displacement .phi..sub.m which is varied from one sequence to the next by successive addition of a constant phase increment .DELTA..phi..sub.m modulo 360 fixed individually for each individual component P.sub.m.

Abstract: An ICR ion trap comprises electrically conductive side plates (1) extending in parallel to one axis (Z), and electrically conductive end plates (5,6) extending perpendicularly to the said axis (Z). Additional electrode plates (8,9) are arranged at a certain spacing from the said end plates (5,6) and can be supplied with trapping potentials of a polarity opposite to the polarity of the potentials applied to the said end plates so that an outer space is defined in which electrodes of opposite sign are trapped. Following analysis and elimination of the ions contained in the inner space, the ions of opposite sign can be trapped in the inner space for subsequent analysis. The arrangement provides also the possibility to observe recombination reactions between ions of different signs.

Abstract: A method of operating an ICR spectrometer comprising a measuring cell (1) having a plurality of side walls (3, 4) designed as rf electrodes and arranged symmetrically to an axis (2) extending in parallel to the field direction of a magnetic field, and further electrically insulated trapping electrodes (5, 6) arranged on both sides of the cell, viewed in the direction of the axis, which trapping electrodes can be supplied with trapping potentials of the polarity of the ions under examination in order to prevent, to a large extent, the ions from leaving the measuring cell (1) in the direction of the axis, provides that, in order to minimize the components of the electric rf field directed in parallel to the axis, which act upon the ions in the measuring cell (1), additional electric rf signals are applied to at least one said trapping electrode (5) on both sides of the said measuring cell (1).

Abstract: An ICR ion trap comprises electrically conductive side plates (1) extending in parallel to one axis (Z), and electrically conductive end plates (5,6) extending perpendicularly to the said axis (Z). Additional electrode plates (8,9) are arranged at a certain spacing from the said end plates (5,6) and can be supplied with trapping potentials of a polarity opposite to the polarity of the potentials applied to the said end plates so that an outer space is defined in which electrodes of opposite sign are trapped. Following analysis and elimination of the ions contained in the inner space, the ions of opposite sign can be trapped in the inner space for subsequent analysis. The arrangement provides also the possibility to observe recombination reactions between ions of different signs.

Abstract: Method and apparatus for introducing ions into an ion trap of an ion cyclotron resonance spectrometer, the ion trap being arranged in a constant homogeneous magnetic field and comprising walls which are designed as electrodes and extend in parallel and/or perpendicularly to a symmetry axis having the direction of the magnetic field and which are supplied with electric trapping potentials retaining the ions in the ion trap, one of the walls which extend perpendicularly to the magnetic field being provided with a hole, the method including the steps of generating the ions outside the ion trap, forming the ions into an ion beam, directing the ion beam upon the hole in the one wall of the ion trap, in the direction of the magnetic field, and reducing thereafter the velocity component, in the direction of the magnetic field, of the ions which have passed the hole and entered the ion trap, below the value determined by the trapping potentials which is needed by the ions for leaving the ion trap, characterized in th

Abstract: The invention provides a cryostat whose components are detachably connected to each other. Each of the tanks (1, 7) is equipped with only one radial pipe (15 or 16) arranged at the end of the tank (1, 7). Each of the inner components (3, 7) is provided, at its end neighboring the pipe (15), with a detachable cover (5, 9), and provided with a recess (31, 71) into which the pipe (15) can be introduced from the end of the component. The jacket (11) is divided in a plane neighboring the pipes (15, 16). The shorter section (45) comprises a recess for the pipes (15, 16) passing through the jacket, and a connection for a tower (19) enclosing the pipes. This makes it possible to do without any welded connections between those sections of the concentrically arranged components which pass through each other.

Abstract: The components of cryostats are interconnected by means of tension members which are frequently made from a fiber glass reinforced plastic material. Such members, which exhibit a rectangular cross-section and bores for receiving the mounting bolts have shown to be not fully reliable because they tend to break easily in the areas of the bores. Consequently, loop-like tension members have been frequently used; but their production is expensive and connected with considerable production tolerances. The invention proposes to use a tension member which is cut out from a plastic sheet material reinforced by a fiber glass weave, and which comprises an elongated portion (21) with parallel edges, followed on both ends by enlarged areas (22) with bores (25) for the mounting bolts. The transition between the central area (21) and the enlarged areas (22) is formed by a transition portion (23) with arc-shaped edges (24).

Abstract: Method for encoding n parameters in multi-dimensional Fourier NMR spectroscopy. In NMR tomography, recording a third parameter is rendered possible without any additional input, in addition to the determination of the two-dimensional data required for generating an image, by generating phase-encoded double signals. During Fourier transformation the double signals lead to a striated pattern which is characteristic of the amount of the parameter It is possible in this manner to represent in NMR images in particular the velocity of a flowing material or, for example, variations of the static magnetic field, the susceptibility and the chemical displacement.

Abstract: In the case of NMR spectrometers comprising a cryomagnet with vertical axis, the sample to be examined is introduced into the measuring area of the magnet by means of a sample carrier which is arranged in a guide tube passing axially through a central space of the craymagnet, and can be moved therein by means of a flow of compressed air. For changing the sample, one switches on the compressed air flow so that the sample carrier is raised to the upper end of the guide tube where the sample can be changed. With increasing sizes of the cryomagnets, the upper end of the guide tube is no longer accessible without an aid (ladder or platform). The invention therefore provides that a direction switch is arranged at the upper end of the guide tube and that an inclined tube extends from the said direction switch to an easily accessible point, for inserting and removing the sample carrier at its end.

Abstract: Ion cyclotron resonance is an important method used in mass spectroscopy. Examinations for determining the reactions between substances by means of the two-dimensional ICR method are carried out using the following measuring sequence:P.sub.1 -t.sub.1 -P.sub.2 -T.sub.m -P.sub.3 -t.sub.2,wherein P.sub.1, P.sub.2 and P.sub.3 are rf pulses, with the rf pulses P.sub.1 and P.sub.2 having the same frequency, t.sub.1 and T.sub.m are time intervals between the pulses and t.sub.2 is the observation time following the last pulse. This measuring sequence is repeated several times while varying t.sub.1. In this manner, a plurality of induction signals recorded during the time t.sub.2 is obtained, from which then a two-dimensional spectrum is derived by transformation from the time domain into the frequency domain. The transformation from the time domain to the frequency domain can be effected by two-dimensional Fourier transformation, or with the aid of the method of maximum entropy.

Abstract: For eliminating undesirable charged low-mass particles from the measuring cell of an ion cyclotron resonance spectrometer the electrodes normally required for exciting the cyclotron movement are supplied with an rf voltage having a frequency twice as high as the resonance frequency of the trapping oscillation of the charged particles between the trapping electrodes provided perpendicularly to the homogenous magnetic field of the spectrometer. In this manner, the low-mass charged particles are excited to perform trapping oscillations in the direction of the homogenous magnetic field which cause the charged particles to overcome the trapping potentials and, thus, to be eliminated.