 A disappointed Oliphant flew to the United States to speak to the American scientists. These included Ernest O. Lawrence at the University of California's Radiation Laboratory in Berkeley. The two men had met before the war, and were friends. Lawrence was sufficiently impressed to commence his own research into uranium. Uranium-235 makes up only about 0.72 % of natural uranium, so the separation factor of any uranium enrichment process needs to be higher than 1250 to produce 90 % uranium-235 from natural uranium. The Maud Committee had recommended that this be done by a process of gaseous diffusion, but Oliphant had pioneered another technique in 1934: electromagnetic separation. This was the process that Nier had used.
