Nit-pick: the problem with the Z-machine fusing D-T is that the D-T reaction kicks out a ton of neutrons. Once you turn a plasma research experiment over to act

Nit-pick: the problem with the Z-machine fusing D-T is that the D-T reaction kicks out a ton of neutrons. Once you turn a plasma research experiment over to actual fusion, you end up with secondary activation of the machine's core components, thereby turning them into high-level radioactive waste. This stops you tearing it down and poking around inside and reconfiguring it. This was the fate of the UK's JET experiment at Culham (the Joint European Torus, predecessor to ITER): once they finally bit the bullet and went to actual fusion containment experiments, the "hot" reactor became a lot less accessible for tinkering and reconfiguration. So you don't take that step until you're real sure you don't want to play with your plasma containment experiment any more.