system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] Where does antimatter come from?

The Federation alone must use hundreds of kgs of antimatter in a year, where do they get it from, ~~as it doesn't naturally occur in a matter-based universe?~~
gpt
According to the ST:TNG Technical Manual:

>As used aboard the USS Enterprise, antimatter is first generated at major Starfleet fueling facilities by combined solar-fusion charge reversal devices, which process proton and neutron beams into antideuterons, and are joined by a positron beam accelerator to produce antihydrogen (specifically antideuterium). Even with the added solar dynamo input, there is a net energy loss of 24% using this process, but this loss is deemed acceptable by Starfleet to conduct distant interstellar operations.

"Charge reversal device" is pretty vague, but if we take the naive interpretation that it somehow "converts" matter into antimatter by "reversing its charge" (ahem, not really a worse violation of physics than faster-than-light travel)... that would be the explanation.

I.e. they "reverse the polarity of the beam".