It is an electron magnet. The medium that holds the electric flow to create the magnetic field is a superconductor, so no energy is needed to maintain the flow, so cutting power doesn't really help.

The aforementioned medium is kept cold by liquid Helium.

As stated I do fire protection, my explanation may be rudimentary in some ways.

I think that '7T' refers to 7 Teslas. I think (note that I am an engineer and not really involved in the response to the fires) that the main determining factor to if they can pull the ax off of the magnet is how close the ax got to the magnet. The force of the pull of the magnet is inverse (or inverse squared) to the distance so if the ax gets really close to the magnet then it is basically impossible.

There are reserves in Africa

I did fire protection engineering and one of the business segments is healthcare (I still do fire protection engineering but in a different area now).

There are special non-ferrous (aka non-magnetic, they use Aluminum) pipe, sprinklers, fittings, etc. that are mainly used for MRI rooms. There are also nonferrous fire extinguishers located outside the rooms, these are typically a white and light blue coloring as opposed to the traditional red. There are also required to be big signs for firefighters to not enter the MRI room.

There are stories of firefighters going into MRI rooms (either they didn't notice the sign or it was not properly marked) and having their fire fighting ax ripped out of their hands by the magnet.

Then the problem is that the ax is basically stuck to the machine. Turning off the magnet is thousands of dollars so they will try to pull the ax off the the magnet with rope and a bunch of guys, sometimes that works, sometimes it does not.

Most of the Helium we get comes from Texas but there are big and underdeveloped deposits in East Africa.