This question already has an answer here:
this company is running a similar project described below. https://firstlightfusion.com/technology/#our-approach Let me clarify here, this is not cold fusion. D&T gas will be compressed very rapidly and its temperature will increase very fast. So, I don't think this is a duplicate question.
This idea is very simple. By accelerating piston (right side) toward the cylinder, we can very easily accelerate piston to speed 100 kilometers per second or higher. The piston will compress D&T mixed gas, and gas will ignite before the cylinder falls to pieces. The cylinder, at this time, you can treat it as a pure fusion bomb. If we put this fusion bomb to a cave and then collect the energy of this bomb and produce electric power. By simply extender accelerating RAIL or improve piston weight, we can easily make the piston with very high kinetic energy to compress D&T gas.