A clean fusion device was a laser-triggered weapon that compressed hydrogen without the containment necessary for a safe reaction. The result was a fusion reaction that released all its radiation at once without the toxic fallout of earlier such weapons.
During the World War Era, fusion bombs were actually fission bombs with a hydrogen core. The result would be wide-spread radioactive fallout from the initial fission detonation. The clean fusion devices eliminated this problem but were never used on Earth.
Clean fusion devices were used on some of the domes on Farigha when it was attacked.
Appearances: No Marigolds in the Promised Land