by Doug Coulter » Thu Sep 13, 2012 8:30 pm
No. Well, what just happened was I replaced all the glass and quartz in my main feedthrough, added an antenna (welded in type N connector) for 2.45 ghz, and changed the 2nd grid/ion source to one made of tantalum. So, there's sodium in the glass...I think (some of it is pyrex), but as far as I know, that's it. When I first put it back together (and fought some new leaking) there were some lines up in the 80s-90s I think due to using diff pump oil to lube the O ring that seals the glass on the FT, but that's all gone now.
The glass is well protected now inside copper pipe in the tank - the copper extends past the end of the glass (and is grounded), so as to protect the glass ends from being reduced by hot D ions hitting it when it takes on a little charge - which seems to be working as a scheme. I slid 1" ID copper tubing over the glass, then near the grid a 1" to 1.25" adapter that flares out and comes within about a cm of the grid end, with the glass about 2 cm back from the end of that - it's pretty protected, in other words. Whatever this is I think it's a gas...hmmm.
I tossed this up on my science group on G+ too, and no one there has a clue either. This is pretty new - it didn't used to show up at all. Water, yeah, CO2 etc, yeah, a few light things, always. But not 43.
Note, no argon at all. That's what really tells me "no leaks". If the remaining O2 and N2 weren't matched by a proper percent of Ar, I'd be thinking "leak", but being non noble, they just stick in there longer even if there's no leak at all.
So, it's still a mystery. Not that it seems to be hurting anything at the moment, but I hate not to have a real solid baseline before I do the next set of experiments of putting in some RF to spin things, find plasma resonances, drive recirculation, whatever - just looking to see what effect it might have and maybe learn something.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.