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My understanding is that a particle must meet its antiparticle. So if you a one-gram cube of, say, anti-gold and shot it into a one-gram cube of normal gold, how would you get the particles to come in contact with the corresponding antiparticles? Would you perhaps try to vaporize both cubes using heat and then mix the hot gas together?

If you actually tried compressing the matter into the antimatter like in a Big Boy implosion device, is it not possible that the exterior layers of the cube would react and destroy the assembly before the antimatter inside the the cube found their antiparticle?

Qmechanic
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releseabe
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    Nobody has any prospect of getting a gram of antimatter anytime soon, so seems unlikely you need to worry about it. ("Big Boy" = "Fat Man"?) – Jon Custer Jan 09 '22 at 21:02
  • what kind of pressure vessel would you put the antimatter vapor in? – niels nielsen Jan 09 '22 at 21:07
  • What you are getting at is that making an antimatter weapon would be a (very) difficult engineering challenge much like making the first fission/fusion weapons were. Of course, like you state in the 2nd para, a major challenge for those weapons exactly was finding ways to keep the reaction going long enough to produce a yield close to the theoretical yield, as they have a tendency to blow themselves apart before the reactions complete. In that sense the "1 gram anti-matter produces x energy" is the theoretical yield. I'm not sure an actual weapon design has ever been rigorously studied. – eps Jan 09 '22 at 21:18
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    On a related note, I have some numbers for the annihilation of hydrogen & antihydrogen here "Surprisingly, starting with $n_H = n_{\bar H} = 10^7 \text{cm}^{-3}$ and energy <10 K, it takes a whole 17 minutes for the mixture of equal amounts of hydrogen and antihydrogen to lose half of all atoms". – PM 2Ring Jan 09 '22 at 21:43
  • Heres the thing, you'd definitely want to use ionized, low atomic mass matter so you can contain them as two containers of plasma and it's anti-matter plasma. The reason is due to the reason you cannot physically touch something because the electron clouds usually repel one another. But in this case anti-matter has attractive positron clouds instead, so it can undergo partial annihilation with any material. – Triatticus Jan 09 '22 at 21:49
  • Nah. You want anti-matter in the form of anti-iron so you can support it magnetically. Makes it very stable. Working out if the thing would detonate or fizzle would be quite a lot of maths. But 1 gm of anti-matter yields in the range of 2-times the Trinity weapon. So you don't need to work very much harder than with existing fission weapons. – Dan Jan 09 '22 at 21:57
  • "This question appears to be about engineering, which is the application of scientific knowledge to construct a solution to solve a specific problem." /s – Michael Seifert Feb 09 '22 at 14:41

1 Answers1

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Aside from the issues of handling antimatter (it's hard).

  • Little Boy released around 63 TJ
  • 1g of matter has an energy of around 90 TJ
  • 1g of antimatter reacting with 1g of standard matter would be two grams, 180TJ
  • 0.35g of antimatter should therefor be enough

Getting masses that react quickly with each other to still get as close as possiblem to each other is a problem every engineer constructing a nuclear bomb faces. You don't want it to start reacting too early (that's why the masses were quite "far apart" in the gun type little boy bomb). Even the microseconds it takes to get the rod into the ball are a problem because once the chain reaction start it's getting really messy really quickly... and it want's to push itself appart quite violently (that's what you want in the end but not too early!)

But with antimatter you're "better off". Because you don't need gold to react with anti-gold. Any neutron will react with any anti neutron. So if after inital contact your gold cubes race away from each other, the anti-gold will react with anything its meeting, also air molecules. So your gold cube will at most travel a few meters until it is completely anihilated and you're left with a rapidly expanding sphere of superheated plasma.

kruemi
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