For those of you who are not familiar with NMR spectrometers, these instruments have a superconducting coil to produce the magnetic field, and like most superconductors this must be kept extremely cold by some cryogen, in this case liquid helium. The liquid helium, in turn, is kept cold by being surrounded by liquid nitrogen. And the liquid nitrogen is insulated by a vacuum, just as in a thermos. When something goes wrong and the superconductivity is lost, an enormous amount of heat gets dumped into these cryogens and all that liquid gas turns into normal gaseous gas and emerges from the magnet with a sound resembling a freight train running over your ear. This video of a much smaller magnet quenching under controlled conditions should give you an idea of what’s to come.
A quench is dangerous, especially in a small space, because all this extra nitrogen and helium can lower the percentage of oxygen in the local area to below what can be tolerated by human beings. Because the particular basement room in question is so enormous this will likely not be a serious problem. Anyway, our 500 apparently has a history of quenching when it is brought to field, so it will likely be several more days before we are actually back to using it again. Or at least, we will once we get through with the referencing, calibrations, etc. that are necessary to actually get anything to work.
UPDATE: The magnet quenched on the afternoon of 3/31. Regrettably there wasn’t time to get the lab downstairs for a “Wizard of Oz” re-enactment.