But the question is what kind of infrastructure is needed to to contain 100 grams of positrons? There's no way you've contained 1/1000th of that amount otherwi

But the question is what kind of infrastructure is needed to to contain 100 grams of positrons? There's no way you've contained 1/1000th of that amount otherwise you wouldn't be telling us about it on the internet (assuming you have Q/Top Secret clearance) Also, assuming it is positrons, I'd imagine you might also have to worry slightly about relativistic background electrons and gamma rays/pair production, unless you're under 10ft+ of concrete. The extremely rare case that a 10^19 eV cosmic ray hits you head on sounds like an awesome way to possibly produce a spontaneous "detonation", or when some jokester thinks it's awesome to point a LINAC right at you.