My university has a sputtering machine which is this crazy expensive piece of equipment that has to have a really strong vacuum pump and wacky copper seals and if it loses power for even a minute it has to spend 16 hours pumping it’s vacuum back down.
I know people talk about how a perfect vacuum is like near impossible, but why? We can pressurize things really easily, like air soft co2 canisters or compressed air, which is way above 1 atmosphere in pressure, so why is going below 1 atmosphere so hard? I feel dumb asking this as a senior mechanical engineering student but like I have no clue lol.
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One technology you might be using to get to low pressure is a cryo pump. Basically you have a very cold surface and any air molecule that happens to bump into it “freezes” onto the surface. Now imagine what happens when you cut the power: the plate warms up and the air molecules are released back into your vacuum chamber. You turn the power on and the plate gets cold again, but now you need to wait for all those air molecules to randomly bump into the plate which takes time. And the fewer particles you can afford to have left the longer you need to wait.
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