Someone should tell them that square centimeters describes an area, not a volume... But maybe I don't understand what they mean by plasma density.

Shock waves are able to concentrate energy in a quite interesting way (see sonoluminiscence), and increase density, however, the Lawson criterion also establish a determined confinement time to satisty the triple product, the condition to reach ignition and thus fusion.

Interesting issue, although let me follow A.L. advice today. Merry Christmas.

So they are trying to combine both branches of fusion development: magnetic and inertial confinement.

Magnetic confinement consists on heating dim deuterium-tritium gas until it reaches the temperature in which its nuclei come close enough to engage. This is usually done by electric currents, radio frequency and particle beams.

Inertial confinement aims to increase the density and temperature of the sample, usually through laser beams. The physics behind it and the results gotten are much more obscure since their implications in energy and nuclear weaponry.

However, we know magnetic confinement works because 16 MW of power with a Q (ratio of energy generated by fusion over energy injected externaly) of 0.7 were obtained in the JET (Joint European Torus) in 1991. Simply - although nothing is simple regarding the very unstable plasma - increasing the diameter of the torus (the "dougnut",) Q must go beyond 1. Utilizing superconductors may increase the energy yield by the machine further.

Thus, regarding magnetic confinement the issue is no longer if Q>1 is within range, but the way to implement subsystems needed for a continuous operation: feeder, tritium producing units (yes, the reactor will produce its own fuel), ash (helium) drain, steam circuits for energy production, and heating systems to keep the plasma burning when induction heating is not available. If this last does not work, don't worry because there is another type of magnetic confinement device, the stellarator, with continous heating capability.

There is a fundamental drawback regarding these devices, which is the reason, IMHO, we don't have fusion energy yet: size matters, that is, there is no way to test the theoretical results in a machine smaller that the size of the final commercial reactor. It is as if the Wright brothers had had to fly a Jumbo jet from Kitty Hawk!

So I am not surprise that private enterprises, especially from the other side of the pond, try inertial devices (this one will be really noisy). It might yield interesting data without using energy weapons from the government (but it seems some kind of steam aircraft carrier's catapults instead). MSimon points out right the questions of the synchronization and faults. In this last one I somewhat disagree: oscillating masses rise many fault problems, not to say two hundred of them. However, as experiment that may help to develop further knowledge and technologies I consider it very interesting and, above all ingenious.

BTW, as sheik Jamani, Saudi Arabia oil minister said, the stone age did not end for lack of stones. And I agree.