Can it sustain a reaction for more than a few seconds?
Yes, at JET.
Lifetime of the plasma: 20–60 s
It will operate over a wide range of ITER plasma scenarios, from short plasma pulses (a few hundred seconds) with enlarged fusion power (700 MW) to long plasma pulses of 3,000 s
Are these devices still huge or have they been made on a smaller scale?
They have to be large in order to give out more energy than they consume. This is the ITER link, the one planned and already being built, to get the size idea.
This post imported from StackExchange Physics at 2014-03-24 04:31 (UCT), posted by SE-user anna v