Incidentally when I went to see JET (it's up the road from me, not that far from Oxford) the scale of the thing was enormous. They mentioned that they'd had been able to sustain plasma for 600 seconds. I've got some pictures up[2] on flickr.
[1] - http://www.i15.p.lodz.pl/strony/EIC/ne/future_2_1.html
[2] - http://www.flickr.com/photos/z3r0kl3w/sets/72157623979315835...
One of my favorite stories is the disruption. This happens when things don't go just right, and all the plasma with its energy squirts onto one spot. This typically puts the equipment in jeopardy. People try to prevent it, but as they push the boundaries of what's been done, it's going to happen.
Keep in mind that there's only about as much mass in the entire chamber as in a few cubic centimeters of air; it's basically a vacuum. But what little there is is so hot, and there's so much energy wound up in the fields. When JET had a disruption, the entire machine, the largest tokamak in the world, LIFTED ITSELF OFF THE GROUND AND JUMPED A FEW FEET OVER.
Any good refs for this disruption situation?
[1] http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach...
[2] http://www.symmetrymagazine.org/article/december-2007/protec...