It there any good reason why nobody is making copper cold traps? Seems like they would me more efficient than stainless and way more efficient than glass. Is the vacuum we are running too low for copper to withstand without ridiculous wall thickness?
Look into carbon bed traps. They are more efficient. They use helium to cool and nitrogen to heat. It uses a composite bed and is ten times more effective as any trap out there. They are pricey but worth it.