MRI Scanner Superconducting Magnet Quench

MRI Scanner Superconducting Magnet Quench

Once a superconducting magnet is ramped up and fully magnetized, it literally takes no additional current or power to keep the magnet going. There's zero resistance -- that's the "superconducting" part -- so  the current flowing in the magnet coils will run forever. That is, forever if the liquid helium cooling the magnet is kept cold enough, which is quite close to Absolute Zero. If the cooling system goes on the fritz, the magnet starts to develop resistance, which cause heat, which causes more resistance, and more heat, and so on until all the liquid helium gets hot enough to become a gas, which then erupts in a jet-engine-sounding event known as a quench. That's thousands of dollars worth of helium you see in the photo sequence above, going bye-bye.

The photo is of the GE MRI manufacturing plant where I used to work, and I myself saw a magnet quench much like this one. Unforgettable, much better than inhaling those balloons and talking like Donald Duck for 15 seconds. In a wide-open space like a manufacturing plant, there's really not much cause for alarm. But in a smaller space, the inert helium can displace all the oxygen and kill you. Several years ago a GE field engineer was killed by a slower, less spectacular helium leak at a customer's site. In a small, enclosed space it can sneak up on you pretty quick.

Comments

[Jason]

Fascinating information. I never realized that those magnets were always on. (And Strategy of bingo/excitement of chess is great)

[Cody]

May i use the quench photo you have displayed at http://www.tommcmahon.net/2005/08/mri_scanner_sup.html for a research project at the university of southern indiana?

[susan]

I was wondering, what is the lowest % of helium you can have before a quench happens,i.e 60% 25% etc, and at what temperature (of the chiller) do you start to suspect a quench will happen
Thanks
Susan

[Lee Pinsanetti]

I guess there is no taste or smell to the helium gasses then? If so I would think the engineer would have been able to exit the infected area and seek help before succumbing to the gasses.

[Wristbands]

Very interesting. Is the cost to keep the magnets cooled down worth the energy they create?