I used 7" of Ta wires, times three, .020" diameter each, and one Ti wire, .032", and this time, loaded it with a 1.5" piece of 1 mil thick Pd foil, about 1/4" wide, wrapped around the middle of this heater.
- Heater that works for Ti and Pd just fine, thanks.
http://www.youtube.com/watch?v=2cr0yJRVFXg
Kind of boring when it works and you're going slowly. At the temps I was creeping up to, this didn't go real fast - except for the Pd if you watch the mica carefully. Not sure that's the best way, but it's the way it happened this time.
So, after doing most of that, I decided to put that last little bit on with D present in normal fusor pressure or a little higher, figuring that if that surface was wonky, I had the good Pd, then Ti under it. It did flake off the mica, but it turned out I had that mica WAY too hot for its health - and at the distance of the tank walls, it didn't flake off the mica either. Turns out though, that this thing really sucked in the D - about 20 times what it normally takes to bring the tank from e-8 mbar up to 2.5e-2. That's a heck of a lot of gas, but I just kept adding more (foreline shut off) and the pressure just kept dropping again, for quite some time.
http://www.youtube.com/watch?v=_NdsyPyqvPA
I'm letting this sit in 1e-1 mbar of D overnight and then I'll put in a new grid with Th doped W rods this time, for grins. If I ever get it really hot, it'll emit electrons better. I expect the Th will get reduced by hot D and some of it will sputter off. We'll see.