FOGBANK
FOGBANK is a code name given to a material used in nuclear weapons such as the W76, W78 and W80.
FOGBANK's precise nature is classified; in the words of former Oak Ridge general manager Dennis Ruddy, "The material is classified. Its composition is classified. Its use in the weapon is classified, and the process itself is classified." Department of Energy Nuclear Explosive Safety documents simply describe it as a material "used in nuclear weapons and nuclear explosives" along with lithium hydride (LiH) and lithium deuteride (LiD), beryllium (Be), uranium hydride (UH3), and plutonium hydride. Many arms experts believe that FOGBANK is an aerogel material which acts as an interstage material in a nuclear warhead, i.e. a material designed to become a superheated plasma following the detonation of the weapon's fission stage, the plasma then triggering the fusion-stage detonation.