Trains are always good for comedy relief, or so I learned from Silver Streak. The problem with plasma containment is generally not holding pressure. The real

Trains are always good for comedy relief, or so I learned from Silver Streak. The problem with plasma containment is generally not holding pressure. The real problem is that plasmas which are hot enough to fuse have a really, really high thermal transfer coefficient. This means that if they touch anything, they want to give away all their heat to whatever they are touching. It is possible to do things quickly enough to have fusion happen before the heat leaks away (this is how inertial confinement fusion works), but that speed is way beyond train speeds. Quickly moving magnetic fields do cause high voltages, which can be used to concentrate charges. Most metals are not fusion fuels, so I'm guessing this wire would be made of lithium. The real problem with this idea is the part where the ions bunch up in the corner of the diamond crystal. What exactly is making them bunch up? The diamond? Realize that CVD works in reverse as well, and diamond is bound together with 3.7 eV bonds and we need a plasma of at least 15000 eV. Any plasma which is hot and dense enough to fuse is going to either be chilled too much by touching the diamond or go through it like a hot knife through butter.