On Sun, 03 Mar 2013 10:06:58 -0500, George
wrote:

On 3/3/2013 8:37 AM, Kurt Ullman wrote:
In article ,
micky wrote:


Just for the record, I was told the MRI machines were magnetic even
when they are off.. That's why I think they won't let me in the room
just to look at a machine with no one in it, until I've undressed.
They let me look at it through a window.

Yep. That is because it is never off, it is just in standby. From my MRI
safety lectures in the past, IIRC, to turn it all the way off there is
an emergency "quenching" that stops the superconducting magnets from
conducting but it take a while, and a whole bunch of money, to bring it
back online.


The "whole bunch of money" is because the emergency shutdown procedure
vents the liquid helium coolant outside.

http://www.youtube.com/watch?v=5z33ZcDgavY

...and a bunch more.