Hello,
In my semiconductor work, we always used to bleed a bit of nitrogen between the backing mechanical pump and the high vacuum pump (turbomolecular in my case) to prevent the mechanical pump’s oil from diffusing up stream once high vacuum had been achieved. The nitrogen would provide a minimum volume of gas flowing through the backing pump preventing the oil from diffusing up.
Oxygen plasma works well on hydrocarbons, assuming your seals and copper can withstand it, aluminum does.
By the way, thank you for doing this work. I wish I could support it somehow.
Chris
