I am aware of the “cold fusion” claims. Very interesting stuff, as much as it is controversial.

My proposal was to have one part hot fuel (high speed protons) and one part cold fuel (solid crystalline boron).
If fusion yield is an issue, maybe the protons can be put in a circular path (like a circular accelerator), going round and round until it hits something (hopefully boron!).
Would the protons just scatter in the crystal lattice, eventually running out of the necessary energy for fusion?