In the meantime, in California, Lawrence worked a more effective way of separating isotopes that depended simply on a deflection of ions that have been given a certain energy by accelerating them and then deflecting them by a magnetic field. The same energy at different masses will give different deflections. That method worked, but it worked only to make enough explosive material for one or two bombs. The mass production looked too expensive, too difficult. There remained a third method, the main method pursued in the Metlab, Metallurgical laboratory in Chicago; make a reactor, construct a reactor, produce a new element, plutonium. In the meantime we, at Los Alamos, found a method to compress the plutonium and make little of it enough to make an explosion, but at the same time the work at Chicago in the Metallurgical Laboratory really took on impressive dimensions.