finishing Ti surfaces for UHV
finishing Ti surfaces for UHV
(OP)
Anyone familiar with best practices for finishing Ti surfaces for a UHV enclosure?
Mechanical polishing to what level?
any chemical or electro-chemical processes?
Mechanical polishing to what level?
any chemical or electro-chemical processes?





RE: finishing Ti surfaces for UHV
Polishing is essential on sealing surfaces. O ring seals work fine on 32 microinch surfaces, but you might want to improve on that for any metal wire seals you might be using.
Theoretically, the smoother the surface finish, the better it is for vacuum, since less surface area means less gas to desorb, just make sure you don't force polishing compounds into the surface. I have always found machined surfaces to work just fine.
I have never made a vacuum chamber from Titanium, stainless steel has always been an appropriate material for my systems, but I don't see any reason Ti wouldn't work.
RE: finishing Ti surfaces for UHV
The target base pressure is 1E-7 Torr.
The concern is about the total quantity absorbed in the walls (as opposed to the outgassing rate), since after initial pump-down to 1E-3 torr, only a getter is available to pump it down to and maintain to 1E-7 torr.
I guess the question was more about the process itself - what is achievable using common mechanical and electro-chemical processes.
RE: finishing Ti surfaces for UHV
For cleaning, I would certainly proceed with a hot degrease (in isopropyl alcohol or similar), followed by an acid clean. This type of pre clean is used in the vacuum tube industry, (travelling wave tubes, magnetrons and so on)where construction of devices from copper, nickel and stainless steel is common. You could try an electropolish, but it is the removal of grease, dirt and oil that is most critical. I would very much like to know how you get on with the getter, if you are able to divulge any info. If I manage tyo dig up any info on similar things, I will forward it. Good luck!
RE: finishing Ti surfaces for UHV