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The atomic bomb test for 'Fat Man'


Help from the British, and the 'Christy Gadget'
Hans Bethe Scientist
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We found out that indeed implosion would work very well, and Teller had suggested that implosion would compress the material. And when you compress the material then the critical mass goes down about as the square of the density that you achieve. So it would... it would seem natural to me to ask Teller, who was the leader of one of the group, that he would take charge of this and... and do theoretical work on implosion. But he refused to do that because he was still more interested in investigating the Super; the use of light nuclear deuterium for further increasing the energy from a nuclear reaction, so I had to get somebody else. And fortunately, at just about the same time, collaboration was established between the British and the American project, and I was told, was there anybody among the British scientists whom I would like to have at Los Alamos? 'Yes,' I said, 'let me take the best, let me ask for Rudi Peierls.' And indeed, Rudi Peierls was assigned to Los Alamos and became the Group Leader of the Theoretical Implosion Division - Group I should say - And he had very good people in his group, one of them was Bob Christy. And when the practical implementation of implosion didn't work quite satisfactory, Christy suggested 'Well, there's a very easy way to do it. We know that material is compressed, so why don't we assemble the material from the beginning, assemble one critical mass, 95% of a critical mass, and then let the implosion act on complete sphere of material. The implosion will compress it to maybe twice the original density, and then we have four critical masses, and that's splendid, and that will give us a very good efficiency.' So this Christy Method was adopted, and it was tested at what is called Alamogordo, in the New Mexican desert, on July 16th, 1945.

The late German-American physicist Hans Bethe once described himself as the H-bomb's midwife. He left Nazi Germany in 1933, after which he helped develop the first atomic bomb, won the Nobel Prize in Physics in 1967 for his contribution to the theory of nuclear reactions, advocated tighter controls over nuclear weapons and campaigned vigorously for the peaceful use of nuclear energy.

Listeners: Sam Schweber

Silvan Sam Schweber is the Koret Professor of the History of Ideas and Professor of Physics at Brandeis University, and a Faculty Associate in the Department of the History of Science at Harvard University. He is the author of a history of the development of quantum electro mechanics, "QED and the men who made it", and has recently completed a biography of Hans Bethe and the history of nuclear weapons development, "In the Shadow of the Bomb: Oppenheimer, Bethe, and the Moral Responsibility of the Scientist" (Princeton University Press, 2000).

Tags: 1946, Alamogordo, New Mexico, Edward Teller, Rudolf Peierls, Robert Christy

Duration: 3 minutes, 45 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008