Plasma focus is definitely a conventional hot fusion machine.


Large quantities of tritium are considered Special Nuclear Materials as they have nuclear weapons utility.

Possibly the device is used to create both Xrays and neutrons for experiments to calibratie the nuclear weapons simulations, like the NIF in Livermore (which is sold as an energy research machine when it is not, it is a weapons research machine---a great waste of so much talent).

The secret stuff might not be the dense plasma focus machine (which is why it's open in the name), but what the targets are.