Subject Re: RF ion source, modified, with deuterium (a couple "glassblowing" pics)
Posted by Carl Willis on 2008-07-11 01:00
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I replaced my $1 test tube and ceramic-washer anti-sputtering shield with a single piece of glass. The new glass may not be $1 anymore, but it is still a bargain compared to glass-metal adapters. Now the discharge "bottle" is butt-sealed to another piece of 19-mm tubing with a flat closure (made by blowing a hot, thin closed end of tubing into a graphite paddle); and a little hole, slightly smaller than the anode extraction hole, is blown in the seal so that ions can be extracted. No metal is directly exposed to the discharge anymore, and the ion source can be operated in any orientation.
Photos show my primitive glassblowing equipment and a completed discharge bottle so that others may get some ideas. Being that I am not a human lathe, I can't rely on my hands alone to keep two glass tubes coaxial while rotating them and translating them at the same time, so we see the little fixture I made to accomplish this task. The two pieces of tubing are brought together in the jig while rotating in the torch flame, and the springs keep enough restraint on the tubing to keep it coaxial. A finished ion source bottle can be seen on the fixture.
A couple asides now. The best way to cut Pyrex tubing of this size and larger (I have tried many methods!): make a deep but short score mark on the tubing with a carbide knife-sharpener. Wet the score and continue drawing a bit of water about half-way around the circumference of the tube; this is important. Bring a tiny, ultra-hot flame, such as from the #1 tip for this National blowpipe, into brief tangential contact with the tubing a few mm ahead of the score on the DRY half of the tube. The tube will cleanly crack circumferentially on the WETTED side. Finish the job with a gentle tug.
My glassworking torch uses propane from a small $2 bottle (lasts many hours) and oxygen from a 5 LPM medical oxygen concentrator. These concentrators are fascinating but conceptually simple pieces of hardware that exploit the unique affinity of nitrogen for molecular sieve beds. Nitrogen is separated from the air, leaving oxygen and other trace gases. The torch loves it just fine, and you don't have to deal with the expense and nuisance of big gas cylinders.
Thanks to Mike Donovan and local pro glassblower Dean Horinek for their helpful advice on this new skill I'm figuring out.
-Carl
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2008-21-10 01:00 RF ion source, modified, with deuterium 
(Carl Willis) [Latest: 2008-10-11 11:24]
2008-07-11 01:00 Re: RF ion source, modified, with deuterium (a couple "glassblowing" pics)