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Could a relatively sparse Dyson Sphere be used to produce a useful amount of antimatter for weaponry in the form of antimatter missiles and maybe basic antimatter fusion drives?

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  • $\begingroup$ Given the cost of preventing antimatter interacting with a matter environment, I don't think it's efficient to have a weapons with antimatter payload. If you solve the containment problem, you can start by eating bananas: K40 emit positrons. Otherwise, the current antimatter produced so far by the human civilization is under 15 nanograms - not enough to boil a cuppa $\endgroup$ Commented Jan 2, 2022 at 6:08

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This is one of those problems where you just multiply everything together and you get the right answer. The amount of antimatter produced by a Dyson sphere is simply the energy flux of the host star at the relevant distance times how long the Dyson sphere has been active. Mathematically:

$ M = (e*t*L*S) / (2*r^2*c^2) $

where e is the efficiency of the Dyson sphere's collectors, t is how long the Dyson sphere as been active, L is the luminosity of the host star, S is the surface area of the Dyson sphere's collectors, r is the radius of the Dyson sphere from the host star, and c is the speed of light in a vacuum. You divide by 2 because you need to produce matter and antimatter in equal amounts.

According to Forbes, the most efficient commercially available solar panels have an efficiency of about 20%. If your Dyson sphere orbits a Sun-like star, is a circle with the same radius of the Earth, and is 1 AU from the star, then this formula simplifies to:

$ M = 2.45kg/s * t $

In 1 year this Dyson sphere will produce $ 7.71*10^7kg $, which is about the mass of a very large ship. Exactly what you consider a "useful" amount of antimatter is highly dependent on what you are doing.

Having that much matter in outer space would be way more than necessary for a kinetic bombardment attack, never-mind what you could do using antimatter. If you are trying to make an economically profitable fusion reactor, then no. The whole point of a reactor is to produce energy, and since both the processes of converting energy into antimatter and turning antimatter into energy will always have inefficiencies, you are better off just charging batteries or beaming the energy back to Earth directly (although this may also result in weapon applications).

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    $\begingroup$ Nice idea, but I suspect 100% efficiency of conversion from electrical energy to matter might be out of reach at the moment. We've recently come-up with a simple method of creating positrons which might work towards that goal. $\endgroup$ Commented Jan 2, 2022 at 8:19
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Yes

Dyson spheres/swarms collect solar energy and covert it to electricity. Electricity can be used to power particle accelerators. Particle accelerators can produce Antimatter.

Given that producing antimatter requires a phenomenal amount of energy, and Dyson spheres/swarms capture a phenomenal amount of energy, they are well suited to the task. I would also guess that any civilization that can construct a Dyson sphere/swarm would have already cracked many of the challenges associated with producing and storing antimatter, so it's a perfectly viable way for them to store energy for later.

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