Lithium hydride
Before the Castle Bravo nuclear weapons test in 1954, it was thought that only the less common isotope lithium-6 would breed tritium when struck with fast neutrons. The Castle Bravo test showed (accidentally) that the more plentiful lithium-7 also does so under extreme conditions, albeit by an endothermic reaction.
RaLa Experiment
On 25 July 1944 the first preliminary test was fired in the Bayo Canyon as a rehearsal, test of equipment, and measurement of collapse times and detonation and shock wave velocities. The program was delayed by about a month by late radiobarium shipments, as the test scheduled for 15 August was not conducted until mid-September. The first test with radiobarium was fired on 22 September. In late August and at the request of Rossi's group, the RaLa group was reformed under the leadership of Rossi, and Alvarez and his group took over the exploding bridgewire detonator research. At the suggestion of Robert Christy solid spheres instead of the originally intended hollow ones were chosen for the pit, in order to reduce the problems with jets and spalling. The first solid-sphere RaLa shot was performed in early December but the results were inconclusive. The shot from 14 December though, showed (in the words of Robert Bacher) "definite evidence of compression".