A device, method and system for causing a controlled collapse of cavities formed within liquid droplets wherein a pressurized jet comprising a liquid and nanoparticle material and possibly fuel produces droplets from the breakup of the jet stream. The liquid droplets are irradiated with energy to produce and expand cavities formed within the droplets by irradiation of the nanoparticles contained within the droplets. The droplets are collided with a target to collapse the cavities within the droplets. The irradiating and colliding are timed to enhance implosion energy resulting from the cavities' collapse. The implosion energy and the fuel in the cavity may be used to activate and sustain a fusion reaction.