NYTimes: Robert F. Christy, who as a young Canadian-born physicist working on the Manhattan Project came up with a critical insight that led to the creation of the world’s first atom bomb, died on Wednesday at his home in Pasadena, Calif. He was 96.Caltech Oral History:
... The first bomb, developed in secrecy during World War II at Los Alamos, N.M., relied on implosion. The plan was to detonate a sphere of conventional explosives, the blast from which would compress a central ball of nuclear fuel into an incredibly dense mass; that in turn would start a chain reaction that would end in a nuclear explosion.
But the Los Alamos team discovered that the interface between the detonating explosives and the hollow sphere could become unstable and ruin the crushing power of the blast wave.
Dr. Christy, while studying implosion tests, realized that a solid core could be compressed far more uniformly, and he worked hard in the days that followed to convince his colleagues of its superiority. He succeeded, and the hollow core was replaced with one made of solid plutonium metal.
A 1993 book, “Critical Assembly,” sponsored by the Department of Energy, which maintains the nation’s nuclear arsenal, said Dr. Christy’s insight reduced the risk that the core would lose its spherical form and thus fail to explode.
And Robert S. Norris, an atomic historian and the author of “Racing for the Bomb,” called Dr. Christy’s breakthrough, known as the Christy pit, “a conservative solution to a problem they were having” that “increased the likelihood of a successful detonation.”
[ The bomb itself was called the "Christy Gadget". ]
Robert Frederick Christy was born May 14, 1916, in Vancouver and studied physics at the University of British Columbia. He was a graduate student at the University of California, Berkeley, under J. Robert Oppenheimer, a leading theoretical physicist who became known as the father of the atomic bomb.
After completing his studies in 1941, Dr. Christy worked at the University of Chicago before being recruited to join the Los Alamos team when Oppenheimer became its scientific director.
After the war, Dr. Christy joined Caltech in theoretical physics and stayed at the university for the rest of his academic career, serving as a faculty chairman, vice president, provost (from 1970 to 1980) and acting president (1977-78). He was elected to the National Academy of Sciences.
Then, in the examinations at the end of grade twelve, they gave us general exams — and this was given to the whole province of British Columbia ... I could get top marks in anything, in that kind of exam. So I got the highest marks on these exams of anyone in the province.