Sadly enough, those already exist: "Fusors have also been developed commercially, as sources for neutrons by DaimlerChrysler Aerospace" http://en.wikipedia.org

Sadly enough, those already exist: "Fusors have also been developed commercially, as sources for neutrons by DaimlerChrysler Aerospace" http://en.wikipedia.org/wiki/Fusor http://en.wikipedia.org/wiki/Fusor But you're right, plasma is not the deadly weapon. Neutrons are.