Spectrospin Ag

Beat Mraz

Daniel Marek

Charles B Martin

Rene Jeker

Werner Schittenhelm

Silvio Di Nardo

Christoph Notzli

Beat Weber

Ernst Ungricht

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). The cooling losses of the cryostat are minimized in the NMR measurement apparatus in accordance with the invention so that a nearly uninterrupted operation of the apparatus is facilitated with, however, no field distortions being produced by the cryogenic measures, which would be extremely undesirable, in particular, with a high resolution NMR spectrometer and which would have to be compensated for through extremely difficult technical measures.

NMR measurement apparatus with pulse tube cooler

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). The device withdraws kinetic energy from thermo-acoustic oscillations of the helium gas column in the conduit system of the cryostat and thus dampens the detrimental oscillations which entrain increased losses of helium and disturbance of the magnetic field at the locus of the sample (FIG. 3a).

Cryomagnet system with a low-loss helium cryostat of minimized

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.

Method and a device for precooling the helium tank of a cryostat

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. The widening tension bars, which are passed through the tie rods, have the effect that the connection is subjected, preferably, to pressure and shearing forces, whereby the tensile strength is prevented from dropping suddenly if the breaking tension should be exceeded.

Cryostat

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. A locking device by which the said pressure-relief cover is retained in position on the tank wall of the cryostat and which, in its closed position, urges the pressure-relief cover against the edge of the tank opening, under the action of a spring, in such a way that the pressure-relief cover is permitted to be lifted off slightly in the presence of a slight overpressure, against the action of a spring, while in the presence of an important overpressure the locking device assumes its open position in which the pressure-relief cover is released from the tank opening, urges the pressure-relief cover automatically against the tank wall so as to close the opening of the tank edge again after a slight overpressure has been released, but releases the opening when an important overpressure prevails in the cryostat. This arrangement prevents damages to the cryostat and avoids the risks connected therewith.

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Hombrechtikon, Switzerland

Beat Mraz