US govt talks up $2B X-ray photobooth to check its nuke weapon sims are right What to do when you want to perform physical tests of the plutonium in your nuclear weapons and you've pretty much told the world you won't set off any more nukes in these kinds of experiments? If you're the US government, you can do what's called sub-critical tests, the results of which can help scientists understand what …
They took photos with 10ns aperture times in the 1950s shown atom bombs actually exploding:
https://en.wikipedia.org/wiki/Rapatronic_camera
More famous images (as unclassified) were of bullets passing through light bulbs or playing cards, etc, for demonstrations of the camera's capabilities.
The El Reg side-bar on the Demon Core incident is a fraction too simple.
The Demon core was two hemispheres of Plutonium. The experiements were to bring the two halves almost together to understand criticality.
Unfortunately, the process for ensuring the two hemispheres remained far enough apart was crude: LIke holding a stick or screwdriver between the two halves.
Guess what? The stick slipped. Twice.
The radiation doses killed some of the people in the room.
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Pardon the correction (see icon), but the demon core itself WAS a sphere.
The first incident used reflector blocks -- one of which got dropped right on top -- not the hemispherical beryllium reflectors of the second incident. The screwdriver was only used as a non-standard/non-approved method by a cocky S.O.B. that paid for it with his life; the approved method used shims.
Wikipedia > Demon Core has all the facts, including validating that Feynman coined the phrase. (Could this have inspired J.K. Rowling's motto for Hogwarts, "Draco dormiens nunquam titillandus" / "Never Tickle a Sleeping Dragon"?)
The term "Tickling the dragon's tail" was coined by Richard Feynman, the experiment itself was designed by Otto Frisch.
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