That orb in the middle of the apparatus is The Demon Core, a piece of plutonium produced during the Manhattan Project, for a third nuke which was never needed. So it was used for criticality experiments, which is where those hemispheres come in.
Anyway, in those experiments it was key in a few accidents, which caused the deaths by radiation of several researchers. After the later bout of experiments, the core was scrapped.
What’s the middle bottom one?
That orb in the middle of the apparatus is The Demon Core, a piece of plutonium produced during the Manhattan Project, for a third nuke which was never needed. So it was used for criticality experiments, which is where those hemispheres come in.
Anyway, in those experiments it was key in a few accidents, which caused the deaths by radiation of several researchers. After the later bout of experiments, the core was scrapped.
A little more reading in case you’re interested
A fun little experiment you can do at home!
Demon Core
https://en.m.wikipedia.org/wiki/Demon_core