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Old 10-08-2009, 08:09 PM
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jeyurkon jeyurkon is offline
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Location: Central Michigan
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Speaking of aluminum, do you know how thick the coating is? This site seems to indicate 500 angstroms.

http://www.thevalvepage.com/teletech...u/crt_manu.htm
That would be thick enough to be opaque to light, but I'm not sure it would protect the phosphor from ions.

I assume the main ion species are singly charged hydrogen from gettering water and nitrogen which is more difficult to getter.

I've attached two simulations for hydrogen and nitrogen at 16KV on aluminum.

The left is for hydrogen and the right for nitrogen.

You can see that even 2,000 angstroms wouldn't protect agains hydrogen and 500 angstroms would barely protect against nitrogen.

I probably should have made some damage plots, but I think this shows the problem. My 40" rear projection set seems to be showing some ion damage on the blue CRT after about 20 years of use. It's a slightly dim blob in the center.

John
Attached Images
File Type: jpg ion_aluminum.jpg (79.5 KB, 10 views)
File Type: jpg nitrogen_aluminum.jpg (138.3 KB, 7 views)
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