It’s like shooting one tiny drop against another and a bit bigger drop. Doesn’t much of the material just pass through. And even if it doesn’t I don’t think much of the kinetic energy will be released. The drop must be slowed down to a much lower speed if the kinetic energy is to be released. The slow down distance is very short. So I suppose that’s why you have to shoot from all direction simultaneously to make that happening. A cylinder of deuterium could if it’s long enough slow down the drop and release the kinetic energy, but the volume is too big and the heat would be spread in too much mass to reach high temperatures enough. So collision is possible but difficult.
