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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Turkey9 wrote ...
A simple o-ring groove with the proper gland design will hold a vacuum fine. For ultra high vacuums, a Teflon seal would work great. The only issue is getting it machined. It has to be seated against a well polished surface and the rod has to be slightly larger than the seal inside diameter. Teflon is used to seal vacuum ball valves.
Id be willing to bet that if a 100 micron vacuum doesnt blast through a seal of this type in less than a second, that it would slowly leak over the course of hours or days spoiling the vacuum.
And as for the ball valves, those are used in activley vacuum drawn circuits, a vacuum tube is static once made.
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
Electroholic wrote ...
Sorry for digging up this old thread, but I was looking at the cool tube thread and noticed Anders' cool tube collection. So the next obvious question is, what about rotating anode xray tubes? Quick google search points to ferrofluid seals, is that the only way?
As others have said, the rotating portion is sealed entirely within the vacuum envelope and spun by way of an externally mounted motor stator. I have one that has noisy bearings but the anode will still spin for literally 20 minutes after power is removed. It's like a freaking perpetual motion machine. I've also seen a few where the rotor control failed and the beam was turned on with a stationary anode, it's not pretty.
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How do Vacuum caps rotate, yet keep there vacuum?
