Roth's "Vacuum Sealing Techniques" goes into the subject of glass to metal seals extensively. I mentioned this book elsewhere.
I've made very good feedthroughs using borosilicate tubing of various diameters and Ace Glass' "Ace Thred" feedthroughs for the conductor. Without going into a lot of detail these fittings are a glass tube with a female thread. The conductor (tube, rod) is held in the threaded tube with an o-ring and a nylon or teflon compression nut.
Very high vacuum compatible and cheap (<$15 for the 11mm (3/8") size plus the cost of the glass work).
The two big illustrations in the article "Neutrons and Neutron Generators" recently posted by The Perfessor show these fittings.
Steve
Created on Friday, March 02, 2001 7:24 PM EDT by Steve Hansen