Patent ID: 7430871

Claim:
An NMR spectrometer for examination of a sample, the spectrometer comprising: a cryostat having a room temperature bore; a helium tank disposed in said cryostat; a magnet coil system disposed in said helium tank; an NMR probe head disposed in said room temperature bore of said cryostat; a cooled RF resonator disposed in said probe head for receiving NMR signals from the sample; an evacuated and thermally insulated housing disposed at a spatial separation from said cryostat; a multi-stage, compressor-operated refrigerator disposed in said housing, said refrigerator having a first stage at a first temperature and a second stage, said second stage having a cold head at a second temperature, said second stage having a first region proximate to said first stage having a third temperature intermediate between said first temperature and said second temperature and a second region proximate to said cold head having a fourth temperature intermediate between said third temperature and said second temperature; a first cooling circuit, said-first cooling circuit having a first heat exchanger in thermal contact with said second region, said first cooling circuit structured to transport helium, liquefied by said first heat exchanger, from said first heat exchanger to said helium tank, said first cooling circuit having a Joule-Thompson valve disposed within said helium tank to accept liquid helium from said first heat exchanger and a first compressor connected between said helium tank and said refrigerator to accept and pressurize helium gas escaping from said helium tank and to pass that gas to said refrigerator for completion of said first cooling circuit; and a thermally insulated transfer line system disposed about said first cooling circuit and extending between said housing and said cryostat.