The Los Alamos Primer — Section I

“On Edward Teller’s blackboard at Los Alamos,  I once saw a list of weapons— ideas for weapons — with their abilities and properties displayed. For the last one on the list, the largest, the method of delivery was listed as “Backyard”. Since that particular design would probably kill everyone on Earth, there was no use carting it elsewhere.”

Robert Serber

Albert Einstein and J. Robert Oppenheimer. Einstein warned that the Germans were researching an atomic bomb and suggested that the United States do the same. Oppenheimer was the leading scientist at Los Alamos National Laboratory. Image courtesy Wikimedia Commons.

The ‘Los Alamos Primer’ is perhaps the most important single document of the 20th Century. Yet, it is a rather simple document that could have been written by many others “elsewhere”, and possibly several years earlier. Thus, the History of this world could have been drastically different. In this post, I  discus the first — and shortest —  section of the entire document. Follow us on Twitter: @INTEL_TODAY

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When the Los Alamos National Laboratory was first organized, Oppenheimer decided not to compartmentalize the technical information among different departments.

This increased the effectiveness of the technical workers in problem solving, and emphasized the urgency of the project in their minds, now they knew what they were working on.

So it fell to Serber to give a series of lectures explaining the basic principles and goals of the project.

These lectures were printed and supplied to all incoming scientific staff, and became known as The Los Alamos Primer, LA-1.

Let us then get started. Here is section 1 of the document followed by my analysis and comments.

THE LOS ALAMOS PRIMER

— — —

The following notes are based on a set of five lectures given by R. Serber during the first two weeks of April 1943, as an “indoctrination course” in connection with the starting of the Los Alamos Project. The notes were written up by E. U. Condon.

1. Object

The object of the project is to produce a practical military weapon in the form of a bomb in which the energy is released by a fast neutron chain reaction in one or more of the materials known to show nuclear fission.

— — —

Discussion & Analysis

The word “bomb” will no longer be used at Los Alamos after these lectures. For security reasons, Oppenheimer asked that all physicists refer to the device as the “gadget”.

The key words are of course “practical military weapon”.  What does “practical” actually mean? According to Serber, it meant that the size/weight of the device had to be small enough to be delivered by an airplane. So, a bomb weighing 100 Tons or so would have had no “practical” military value.

Notice that the low weight was a necessary condition for the airplane to carry the bomb. But it was not so obvious that the plane would survive the blast. Actually, the escape maneuver was quite complex and pushed the plane to its extreme mechanical limits.

Surprisingly, “practical” does not appear to refer to a low/acceptable probability of failure due to the intrinsic features of quantum mechanics. I believe that Oppenheimer warned the US military before Hiroshima that such a possibility could not be avoided, due to pre-detonation or fizzle. But it is unclear — at least to me — when the Los Alamos physicists first understood this issue and when the US military were first told about it.

Nuclear Fission — The lost years

Nuclear fission of heavy elements was discovered on December 17, 1938 by German Otto Hahn and his assistant Fritz Strassmann, and explained theoretically in January 1939 by Lise Meitner and her nephew Otto Robert Frisch.

English physicist James Chadwick discovered the neutron in 1932. Enrico Fermi and his colleagues in Rome studied the results of bombarding uranium with neutrons in 1934. Fermi concluded that his experiments had created new elements with 93 and 94 protons.

The German chemist Ida Noddack was not convinced and suggested — in print — during 1934 that instead of creating a new, heavier element 93, that “it is conceivable that the nucleus breaks up into several large fragments.”

Noddack’s conclusion was not pursued at the time. Had the German scientists paid attention to her extraordinary intuition, the History of the world could have been totally different. There is no doubt that Germany had the technical ability to produce an atomic bomb at that time in just a few years.

What if?

Ask yourself a simple question. Suppose that the Germans had produced a few A-bombs, used them and nevertheless lost WW II. What would have happen to them?

Werner Heisenberg answered that question after the bombing of Hiroshima. Without a doubt, they would have been convicted of war crimes as the use of A-bombs is obviously illegal under the principles of International Humanitarian Law. But — in the real world — the Law of War only applies to the vanquished. Vae victis!

In a conversation between WIRTZ, VON WEIZSÄCKER and HEISENBERG, HEISENBERG repeated that in July 1944 a senior SS official had come to him and asked him whether he seriously believed that the Americans could produce an atomic bomb. He said he had told him that in his opinion it was absolutely possible as the Americans could work much better and quicker than they could. VON WEIZSÄCKER again expressed horror at the use of the weapon and HEISENBERG replied that had they produced and dropped such a bomb they would certainly have been executed as War Criminals having made the “most devilish thing imaginable”.

Anecdotes…

In the early 90s, George Wells FARWELL introduced me to Hans BETHE, often described as the most important “gift” from Nazi Germany to the United States. Bethe came to UW in Seattle to discuss first the 1987A supernova and then — what was known at that time as — the solar neutrino puzzle.

After graduating from Harvard in 1941 Farwell began graduate studies in physics at Berkeley. In 1943 he joined the Manhattan Project at Los Alamos, New Mexico. He participated in the first atomic bomb detonation at Trinity Site, New Mexico, in 1945. After the war he completed his PhD under Enrico Fermi at the University of Chicago. The subject was the induced fission of Plutonium.

Once George told me about stressing situations. “Suppose you are sitting at your desk doing some calculations. Then, out of the blue, you smell Oppie’s pipe behind you. Now, that IS stress!” [BTW, George was one of the kindest person I ever met.]

Bethe told me two things I never forgot. The first is obvious to physicists but nevertheless completely misunderstood by politicians. US President Truman is proof of that when — speaking about the Russians — he stated that the “Mongols” are not smart enough to build an atomic bomb….

Bethe — as the Los Alamos primer makes it very clear — stated that there is only ONE SECRET about the A bomb. And the secret is that it can be built! After Hiroshima, there was no secret left whatsoever. Everyone KNEW that there is a solution to the problem. Full Stop!

Bethe made a second point which — in my opinion — has not been debated in a satisfactory way to this day. He said that Hiroshima may, or may not,  have been justified. But in his mind, Nagasaki was without a doubt a war crime. I agree.

President Harry Truman announces the Bombing of Hiroshima

REFERENCES

Revisiting The Los Alamos Primer — Physics Today

The Los Alamos Primer — Original pdf

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The Los Alamos Primer — Section I

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