Comment by fabian2k
7 years ago
I'm very certain that there are usually oxygen sensors installed for MRI machines and NMR spectrometers. I'm not sure how sensitive they are. Either they were not triggered, e.g. because the helium concentration was low, or at least low at the position of the sensors. Or if it was high, they were disabled or ignored.
120 liters of liquid helium is a lot, but it wasn't released at once but over a longer time as far as I understand the story.
Some have sensors and some don’t. GE ones do in my limited experience (one scanner), other vendors don’t (experiece limited to half a dozen scanners).
I don't mean sensors directly attached to the machine. My experience is with NMR spectrometers, which work based on the same principle as MRI machines and have the same superconducting magnets that require liquid helium and nitrogen. And those essentially always have an oxygen sensor in the room somewhere, but not connected to the spectrometer itself.
Yes - that’s what I mean too. GE located theirs in the scanner control room. The other vendors didn’t have them. I’m going to confirm this as I’m doubting myself now, but the GE one would fail every few years as the sensors have a limited life. It was ear splittingly obvious that they had one.