This is, like the Nature News article, a non-technical article, but it has some interesting bits of information.
On General Fusion:
The number of pistons needed is growing rapidly, probably because of the results of General Fusions simulation results to work around the Richtmeyer Meshkov instability. For the pilot plant they probably want to have a good safety margin so that it will work, but 400 pistons is a lot.At the moment, they expect that will require a monster version of their current setup, with a reaction chamber three times as big, up to 400 pistons hammering its surface, and possibly two opposing plasma injectors firing compact toroids that collide and merge before compression.
On EMC2:"We're very far along compared with the others," Lerner says. "Tri Alpha is three orders of magnitude behind."
This article is behind library access or a paywall at this link:http://www.sciencemag.org/content/345/6195/370.summaryIn experiments carried out last October, EMC2 used improved electron guns to build up a high pressure of electrons in the center and showed that confinement was significantly improved. "We've taken a big step forward," Park says. "We were behind Tri Alpha, now we're competing directly."