CRYOMAGNETIC SYSTEM WITH LOW-LOSS HELIUM CRYOSTAT

摘要

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).