I was wondering if fusion based on positron-electron annihilation would be possible; my intuition tells me it is, but I'm not completely sure and wanted to consult this community. Essentially, I was wondering if a stream of positrons (ignoring the source and difficulty of production for a moment) could annihilate some of the "free" electrons in a plasma, releasing energy and causing fusion ignition. I would imagine this is possible, and it seems to me that companies like Positron Dynamics are pursuing this. Interestingly, they are smashing a target of non-ionized fusion fuel with the positrons; what would be the advantages/disadvantages of doing this instead of ionizing your fuel first and then effecting annihilation? Furthermore, I'm probably making an extremely elementary mistake here, but here it goes. I'm sorry if it's a dumb question, but it's really bugging me. Wikipedia states that the energy required for proton-boron fusion is 600 KeV, while D-T requires 66 KeV; meanwhile, the collision of an electron and positron produces at least 1022 KeV overall. This would make it seem as if you only need a single positron (perhaps a few more if some of the gamma rays don't hit the nuclei completely) to cause fusion ignition, which seems absolutely ridiculous and almost too easy. Where did I go wrong? Sorry if I'm missing something easy, but I'm curious. Thanks!