shaped inner explosive, a new spherical wave—centered on the object—is formed. The successful functioning of this device hinges on the simultaneous initiation of the wave in each segment, uniformity and precision in the speed of the wave, and correctness and accuracy in the shape of the interface between the two explosives. A series of experiments was performed in 1944 and 1945 during the Manhattan Project to develop the lenses for a satisfactory implosion. One of the most important tests was the series of RaLa Experiments. Initially, a 32 "point" assembly was used (each of which had a pair of exploding-bridgewire detonators). Later, a 92 "point" assembly was tried, with the objective of obtaining a smaller assembly with improved performance. Finally, with the success of the Swan device, a two "point" assembly became feasible. Swan used an "air lens" system in addition to shaped charges and became the basis of all U.S. successor designs, nuclear and thermonuclear alike, and featured small size, light weight, and exceptional reliability and safety, as well as using the least amount of strategic materials of any design. Other uses Lenses using alternate design techniques and producing flat "plane wave" outputs are used for high transient pressure physics and materials science experiments. See also Impact depth Nuclear weapon design Notes Explosives engineering Nuclear weapon design Nuclear weapon implosion