Tungsten Parts for Ion Source Construction: Cheap Source !!!

[DaveC]

Doug -

Thanks for the tidbit about aluminum dissolving tungsten. If I knew it before, I had completely forgotten about it.

Just last week, I had the exact situation you described, in which my relatively fine W filament was evaporating some Al for some thin films ( < 1um thickness). I had been quite successful at reusing the filament several times, without breaking it, when loading up with the Al. This time, just as I finished, the filament got very much hotter at one point away from the evaporation region, and subsequently broke. I was a bit surpised to see that it was necked down as if it had been dissolved away.... which it had been! The vacuum was pretty good, since the coating were beautifully bright and shiny like mini-mirrors. Gaging indicated pressures of low -6s. So oxidation was not the culprit here.

Aluminum dissolving the tungsten is a nice explanation that "fits all the data." Thank you.

Dave Cooper