Helium and nitrogen reliquefying apparatus

Abstract

A cryogen boil-off gas re-liquefier adapted for retrofitting magnetic resonance instruments designed to exhaust vaporized helium. Means for recondensing helium and nitrogen boil off gasses to reduce operating cost of cryogenic systems.

Description

TECHNICAL FIELD[0001]The invention pertains to the field of cryorefrigeration. The invention more particularly pertains to conserving liquid helium and liquid nitrogen in nuclear magnetic resonance and magnetic resonance imaging systems.BACKGROUND[0002]Liquid helium and liquid nitrogen are used to maintain low temperatures for superconductivity, magnets operated with superconducting elements, and instruments for imaging and spectroscopy referred to as Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) spectroscopy. Many of these systems were designed and installed with the expectation that helium and nitrogen vapor would boil off and be exhausted as they were both plentiful and not environmentally harmful. Presently however it has been observed by the inventors that resupply of cryogens is both inconvenient and increasingly expensive as helium supply has not expanded at the rate of helium demand.[0003]Cryocoolers comprising a compressor and a cold head are within ...

AI Technical Summary

Benefits of technology

[0009]The cost and inconvenience of resupplying liquid helium and liquid nitrogen is reduced. New shipments of superconducting magnets can be delivered in the chilled state without the cryogen refrigeration system installed which eliminates boil off of cryogen due to environmental heat in the unpowered refrigeration heat mass. Maintenance on the cryogen refrigeration equipment can be done by removing the transfer line and leaving the NMR / MRI system in production mode. Multiple client NMR / MRI cryostats may be served by a single high capacity refrigeration unit. Legacy NMR / MRI systems designed to vent helium to the atmosphere may be upgraded with a reliquefier without removal or time consuming modification.

Problems solved by technology

Presently however it has been observed by the inventors that resupply of cryogens is both inconvenient and increasingly expensive as helium supply has not expanded at the rate of helium demand.

Conventional cryogen reliquefication systems have been observed to induce undesirable sidebands in NMR and artifacts in MRI images due to mechanical vibration of the high intensity magnets.

Moreover, cryogen reliquefication systems, being mechanical, require periodic servicing and maintenance which if integrated into the cryostat interrupts the production schedule of the highly expensive NMR / MRI capital equipment.

Cryogen refrigeration systems cause undesired sidebands in spectroscopy and artifacts in images provided by nuclear magnetic resonance instruments yet cryogen boil-off is ever more expensive and inconvenient in materials, lost production time, and supply chain management.

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