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.
In: 3143
One of the issues is when you get into high vacuums there there aren’t a lot of molecules left, and your pump can’t remove them from the center of the container.
When you remove them on one side of the container by pump or whatever you’re waiting for entropy to push molecules from the rest of the container towards the place you can pump them away. In normal atmospheres this isn’t an issue, but getting close to ‘perfect vacuum’ this takes time. And in that time new molecules can leak/offgas/whatever other ways back into your container.
(note: “not a lot” is relative here. The space between galaxies are pretty good vacuums but still have about 1 trillion molecules per m3)
Latest Answers