The Los Alamos Primer: The Introductory Course for Scientists at Los Alamos | Hacker News Reader

The Los Alamos Primer: The Introductory Course for Scientists at Los Alamos

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78 pointsjohnjwang7 comments

There is an edited and expanded edition with an introduction Richard Rhodes available in hard copy http://www.amazon.com/Los-Alamos-Primer-Lectures-Atomic/dp/0...

For the fusion bomb side, recently a book has been written http://www.worldscientific.com/worldscibooks/10.1142/9269 There was some recent controversy regarding what material should be published, the author published it anyway http://www.nytimes.com/2015/03/24/science/hydrogen-bomb-phys...

> Since the weight of 1 nucleus of 25 is 3.88*10-22 gram/nucleus

Anyone know why U-235 is called 25 (section 4), or why the atomic mass is slightly off? (233.66 amu)

U-235 contains 92 protons and 235 protons + neutrons. As a "code word" for Uranium-235 they took the last digit from 92 and the last digit from 235 and referred to it as 2+5 = 25

Same with plutonium-239 which has 94 protons and 239 protons + neutrons. It was referred to as 4+9 = 49

Ah, thanks. I was assuming that material "49" was plutonium. One interesting thing in the notes that I didn't know was the extent to which the role of the "tamper" material was already well-understood. Would it be correct to say that the sphere of inward-facing explosive charges that produced the zone of high pressure in which the reaction occurred was a sort of "active" tamper? Was that the big breakthrough necessary to get the reaction to the critical stage?

Not really. The tamper serves to keep the nuclear material together longer through inward inertia. Additionally tampers are usually neutron reflectors which also reduce the time needed to burn all of the material into energy.

An analogy I've heard is that without a tamper an implosion device would be analagous to resting a hammer on a nail and trying to push down on it. Including a tamper is analogous to raising the hammer and striking the nail. You accelerate the hammer head use the inertia of the hammer head to create a greater impulse to strike the nail.

EDIT: More clearly answering your question yes the spherical implosion mechanism was absolutely critical for creating the needed material density for the bomb. I'm correcting the usage of calling it a tamper, as it is a separate piece of the nuclear bomb puzzle.

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Unfortunately, Los Alamos National Lab has been setting its sights a little lower these days:

"How to use the stairs" https://www.youtube.com/watch?v=rDsTc2oWGSI

Nothing a little federal cash can't fix, though:

"The Los Alamos National Laboratory Slip Simulator Experience" http://www.efcog.org/wg/ism/events/Fall12mtg/presentations/L...

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